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HomeMy WebLinkAboutPermit L06-089 - BARGHAUSEN TOM - LA TOURELLE SHORT PLATLA TOURELLE SHORT PLAT LAND DIVISION LAND DEVELOPMENT S 16OST&S3AVS L06-089 18215 72ND AVENUE SOUTH KENT. WA 98032 (425) 251-6222 (425) 251-8782 FAX E-MAIL adorsch@barghausen com www.barghausen.com CIVIL ENGINEERING. LAND PLANNING SURVEYING. ENVIRONMENTAL SERVICES • • City of Tu;'.. ,la Jim Haggerton, Mayor Department of Community Development Jack Pace, Director April 1, 2009 Ms. Alexia D. Dorsch Bargahausen Consulting Engineers 18215 72"d Ave S Kent, WA 98032 RE: La Tourelle Short Plat (L06-089) Dear Ms. Dorsch: The above short plat application was submitted to the City in December of 2006. It was agreed the City and the applicant would resolve the sensitive area issues on the property prior to the City conducting a complete short plat application review. On October 4, 2008, the City mailed you a letter noting that the City's geotechnical consultant had found the geotechnical study prepared by ORA acceptable. Additionally, the most recent site plan indicated that there would be not impacts to the wetland buffer area on the property. The City's letter further noted that it would seem appropriate to begin the formal short plat review process. Revised short plat documents needed to be prepared that reflected the revised site plan and the report by ORA. As of today the revised information has yet to be submitted. If you wish to proceed with this short plat application you will need to submit revised short plat documents to the City by April 30, 2009. The City will assume the short plat application canceled if no information is submitted by that date. If you have any questions, please call (206) 431-3684 or send an email to bmiles@ci.tukwila.wa.us. Brandon J. Miles Senior Planner cc. (File L06-089) 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • Phone: 206-431-3670 • Fax: 206-431-3665 • City of Tukwila • Jim Haggerton, Mayor Department of Community Development Jack Pace, Director October 4, 2008 Ms. Alexia D. Dorsch Bargahausen Consulting Engineers 18215 72nd Ave S Kent, WA 98032 RE: La Tourelle Short Plat (Permit Number L06-089) Forth Geotechnical Peer Review Dear Ms. Dorsch: Attached you will find a letter from Shannon and Wilson, Inc who the City used to conduct a peer review of the geotechnical report submitted by Otto Rosenau and Associates. The letter from Shannon and Wilson notes, "The revised geotechnical report dated September 18, 2007 and response letters from ORA from an acceptable geotechnical study for the proposed short plat and development". Now that an acceptable geotechnical evaluation has been completed it would seem appropriate to begin reviewing short plat and civil plans for the proposed short plat. When you submit please provide four copies of all plans and documents. Also, please ensure that the short plat survey and civil plans reference the geotechnical documents completed by Otto Rosenau and Associates. If you have any questions, please feel free to call me at (206) 431-3684 or send an email to bmiles ' ci. kwila.wa.us. Sin Brat don J. iles Senior Planner cc. File (L06-089) 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • Phone: 206-431-3670 • Fax: 206-431-3665 SHANNON 6WILSON, INC. GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS September 10, 2008 Ms. Joanna Spencer City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 ALASKA CALIFORNIA COLORADO FLORIDA MISSOURI OREGON WASHINGTON tilEivED seal 2 0008 pUg� C vv RKS RE: FOURTH GEOTECHNICAL PEER REVIEW, LA TOURELLE PLAT, SOUTH 160TH STREET AND 53" AVENUE SOUTH, TUKWILA, WASHINGTON Dear Ms. Spencer: We have reviewed a letter prepared by Otto Rosenau & Associates, Inc., entitled, "Response to Third Geotechnical Peer Review, Proposed La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, Washington, King County Parcel #5279200005 and 5379200006, ORA Project Number: 06-373, Report 3," dated July 19, 2008. Otto Rosenau & Associates, Inc. (ORA) is the geotechnical engineer -of -record for the proposed La Tourelle Short Plat project in Tukwila, Washington. In our opinion, the responses provided by ORA adequately address our review comments. The revised geotechnical report dated September 18, 2007, and response letters from ORA form an acceptable geotechnical study for the proposed short plat and development. We appreciate the opportunity to be of service. If you require any additional services, please contact me at mwp@shanwil.com or at (206) 695-6875. Sincerely, SHANNON & WILSON, INC. Martin W. Page, P.E., L.E.G. Associate MWP:TMG/mwp 21-1-20689-003-L2.doc/wp/LKD 400 NORTH 34TH STREET • SUITE 100 P.O. BOX 300303 SEATTLE, WASHINGTON 98103 206.632.8020 FAX 206.695.6777 TDD: 1.800.833.6388 www.shannonwilson.com 21-1-20689-003 LOG,- CRA oZs jJ' g2 NG ENG%N�`fi Brandon Miles City of Tukwila Planning Department 6200 Southcenter Boulevard Tukwila, WA 98188 RE: Response to Geotechnical Comments La Tourelle Preliminary Short Plat Permit No. L06-089 Our Job No. 12650 Dear Brandon: CIVIL ENGINEERING, LAND PLANNING. SUHVLYINL;, LNvIHONMLNIALSEIIVICES August 4, 2008 COURIER DELIVERY Otto Rosenau and Associates, Inc., has prepared a Response to Third Geotechnical Review, dated July 19, 2008, to address the peer review comments by Shannon and Wilson, Inc., dated May 8, 2008. We are submitting three (3) copies of the response for your continued review and routing. It is our understanding that the enclosed response addresses all of the comments received from Shannon and Wilson, Inc., and the City of Tukwila regarding geotechnical review to date. If you have questions or need additional information regarding this project, please do not hesitate to contact me at this office. Thank you. Sincerely, Alexia D. Dorsch Assistant Planner ADD/tep 12650c.021.doc enc: As Noted cc: Joe Arnon (w/enc) Anthony Coyne, Otto Rosenau and Associates, Inc. Tom Barghausen, Barghausen Consulting Engineers, Inc. 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251 6222 (425) 251-8782 FAX BRANCH OFFICES • OLYMPIA, WA 1 TACOMA, WA 1 SACRAMENTO. CA 1 TEMECULA, CA www. barghausen. com July 19, 2008 OTTO ROSENAU & ASSOCIATES, INC. Geotechnical Engineering, Construction Inspection & Materials Testing 6747 M. L. King Way South, Seattle, Washington 98118-3216 USA Tel: (206) 725-4600 • Toll Free: (888) OTTO-4-US • Fax: (206) 723-2221 WBE W2F5913684 • WABO Registered Agency • Website: www.ottorosenau.com City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila, Washington 98188 Re: Updated Drilled Shaft Design Response to Third Geotechnical Peer Review La Tourelle Short Plat South 160th Street and 53rd Avenue South Tukwila, Washington King County Parcel # 5379200005 and 5379200006 ORA Project Number: 06-373, Report 3 These updated drilled shaft design recommendations have been developed in response to peer review comments provided by Shannon & Wilson, Inc. following their review of our report titled "Geotechnical Engineering Report, Proposed La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, Washington, King County Parcel # 5379200005 and 5379200006, ORA Project Number: 06-373, Report 3" dated March 11, 2008. Shannon & Wilson's review comments were prepared for the City of Tukwila in a letter dated May 8, 2008. These updated drilled shaft recommendations are intended to replace Section 11.3.2 and the associated appendix figures in our most -recent report for the project March 11, 2008. 11.3.2 Drilled Shafts: Based on the large anticipated lateral loads and bending moments that could be developed in the event of slope instability, we anticipate that a drilled shaft element will be necessary. We anticipate that the drilled shafts selected for use on this project will be designed to be as efficient as possible, and still be able to resist the anticipated design loads. We estimate that the minimum drilled shaft diameter for use on this project will be 24 inches. The use of larger, higher capacity, drilled shafts is possible, but usually the added expense in having larger construction equipment on site outweighs the benefit gained in reducing the number of drilled shafts installed. As a result, we have performed our analyses based on the assumption that 24 -inch diameter drilled shafts will be utilized. We have also assumed a preliminary loading scenario that may not be representative of the final design requirements, and should be re-evaluated as the actual design loads are determined. We estimated the lateral pressures that would be exerted on the future foundation elements by examining the interslice forces from the slope stability analyses. The interslice were selected at the approximate location of the future structures at Borings B-1 and B-3. The lateral forces from possible slope instability were modeled in our pile design as a 2,000 pound per square foot uniform bad applied horizontally on the grade beam (assumed 3 -foot by 8 -foot tributary area), as well as on the drilled shafts from the bottom of the grade beam to the depth of the geologic Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Plat, South 160'" Street and 53rd Avenue South, Tukwila, WA Project No.: 06-373 Date: July 19, 2008 contact of the dense to very dense sand or very stiff to hard silt and clay. We also included a 30,000 pound shear load applied in the horizontal direction, and a 30,000 pound downward axial Toad applied at the grade beam to model future structural loads that may be imposed on the foundation. The figure on page A-63 of Appendix A presents our assumed pile loading model. We recommend that drilled shafts have no less than a 24 -inch cross-sectional diameter and extend to a depth of at least 40 feet, and at least 10 feet into the very stiff to hard silt and clay or the dense sands. The design of drilled shafts was based on subsurface profiles as presented in Borings B-1 and B-3. The presence of approximately 10 feet of structural fill was included for the design of drilled shafts at Boring B-1 to represent the minimum amount of fill that will likely be required in the developed condition. No new fill was assumed to be necessary at boring B-3 based on the existing site grades. The drilled shafts were designed assuming that the potentially liquefiable soils provide no frictional resistance along the sides of the shaft through the zone of potentially liquefiable soils (zero side friction). We further assumed that the shafts did not develop any tip resistance through the entire soil profile. 24 -inch diameter drilled shafts may be designed for the following preliminary values assuming the above-mentioned loading conditions are present. Axial Shaft Capacity Location Downward (kips) Uplift (kips) Boring B-1 38 37 Boring B-3 47 34 These values include a factor of safety of about 2.5. These capacity values may be increased by one-third when considering design Toads of short duration such as wind but not seismic forces, due to the significant seismic hazards that are present at the site. Figures presenting the allowable axial pile capacities versus pile length are presented on the attached figures titled "Allowable Axial Capacity vs Pile Length (Boring B-1)" and "Allowable Axial Capacity vs Pile Length (Boring B-3)". The allowable axial capacities presented above are based on the strength of the supporting soils for the penetrations indicated. The axial capacities apply to single shafts. If shafts within groups are spaced at least 3 -shaft diameters on center, no reduction for group action is required for axially -applied Toads. We have also provided a table of the anticipated lateral loading performance of the installed shafts. The loading conditions described above were used and fixed head conditions were Otto Rosenau & Associates, Inc. Page 2 of 3 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client Mr. Jawaid Amon Job Name: La Tourelle Plat, South 160`" Street and 53rd Avenue South, Tukwila, WA Project No.: 06-373 Date: July 19, 2008 assumed at the pile top (no rotation). ORA can provide a similar table for other loading conditions upon your request. Location Drilled Shaft Diameter (inches) Estimated Deflection (in.) Estimated Maximum Moment (foot -kips) Approximate Depth to Point of Fixity, Moment = 0 ft -kips, below grade beam (feet) Boring B-1 24 0.5 270 37 Boring B-3 24 0.7 355 33.5 We recommend that reinforcing sufficient to resist the expected bending moments be installed full depth in the 24 -inch -diameter drilled shafts. A reduction factor may need to be applied to piles that are spaced closer than 8 pile diameters to account for pile group effects under lateral loading conditions, which we anticipate will be the case. ORA should be contacted to determine appropriate lateral load capacity reduction factors once the final loading conditions and shaft selection is completed. If the applicant wished to more clearly define the characteristics of the likely failure surface and to provide confirmation of the assumed subsurface characteristics used in the pile and slope stability analyses, an additional deep test pit exploration (20 to 25 feet in depth) could be considered between the locations of B-1 and B-3. The test pit excavation should be completed using a Targe excavator that could extend to the dense to very dense sand or the very stiff to hard silt/clay contact. The test pit excavation should take place during a drier time of the year. If you have any questions please contact us. Sincerely, Otto Rosenau & Associates, Inc. (11/0 Anthony G. Coyne, P.E. Geotechnical Engineer Attachments: Figures titled ""Allowable Axial Capacity vs Pile Length (Boring B-1)" and "Allowable Axial Capacity vs Pile Length (Boring B-3)" Otto Rosenau & Associates, Inc. Page 3 of 3 a 80 70 60 50 a 73 40 co 0. U m 30 a. 20 10 0 Allowable Axial Capacity vs Pile Length (Boring B-1) 24 -inch diameter drilled shafts (Developed Condition - 10 feet of new fill and GW at -13 feet Assumes zero skin friction from 13 to 31 feet and zero tip resistance along entire shaft length) —�—Compression - - + - - Uplift 1-g b3 .3 17 71 0 10 20 30 Pile Length, L (ft) 40 50 60 OTTO ROSENAU & ASSOCIATES, INC. Project Title: La Tourelle Short Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 07/19/2008 ORA Job No.: 06-373 90 80 70 a 60 50 cu R 40 U d E 30 20 10 0 Allowable Axial Capacity vs Pile Length (Boring B-3) 24 -inch diameter drilled shafts (Developed Condition - No new fill and GW at -24 feet, Assumes zero skin friction from 23 to 35 feet and zero tip resistance along entire shaft length) 0 10 20 30 Pile Length, L (ft) 40 50 60 OTTO ROSENAU & ASSOCIATES, INC. Project Title: La Tourelle Short Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 07/19/2008 ORA Job No.: 06-373 =0 —a—Compression - - o - - Uplift A 61 64 44 ,047 ,o'32 .*"(4 .0.49 .-1‘9 27 . . 0.22 0 10 20 30 Pile Length, L (ft) 40 50 60 OTTO ROSENAU & ASSOCIATES, INC. Project Title: La Tourelle Short Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 07/19/2008 ORA Job No.: 06-373 July 19, 2008 OTTO ROSENAU & ASSOCIATES, INC. Geotechnical Engineering, Construction Inspection & Materials Testing 6747 M. L. King Way South, Seattle, Washington 98118-3216 USA Tel: (206) 725-4600 • Toll Free: (888) OTTO-4-US • Fax: (206) 723-2221 WBE W2F5913684 • WABO Registered Agency • Website: www.ottorosenau.com City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila, Washington 98188 Re: Response to Third Geotechnical Peer Review La Tourette Short Plat South 160th Street and 53rd Avenue South Tukwila, Washington King County Parcel # 5379200005 and 5379200006 ORA Project Number: 06-373, Report 3 ORA prepared a third revised report for the project titled "Geotechnical Engineering Report, Proposed La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, Washington, King County Parcel # 5379200005 and 5379200006, ORA Project Number: 06- 373, Report 3" dated March 11, 2008. Shannon & Wilson, Inc. provided peer review comments of the report for the City of Tukwila in a letter dated May 8, 2008. Our response to the review comments are listed below. o During our second peer review, we observed and stated that there was a discrepancy between the number of samples analyzed for liquefaction and the number of samples retrieved/tested in boring B-2. Liquefaction results for boring B-2 were presented in Figure A-62 of ORA's August 2007 geotechnical report and now are presented in Figure A-54 of the revised geotechnical report. The discrepancy has not been corrected. We recommend checking the analysis and correcting the figure for completeness, even though boring B-2 is not within the revised development boundaries. ORA Response: The liquefaction analysis completed for boring 8-2 was updated with factors of safety against liquefaction calculated for each Standard Penetration Test (SPT) performed. A total of 15 Standard Penetration Tests were performed at boring 8- 2. A revised figure titled "Result of Liquefaction Analysis at 8-2 (Updated)" is attached to this letter. • Section 11.3.2 of ORA's revised report presents recommendations for designing drilled shaft foundations. ORA recommends that the shafts should be at least 40 feet long and at least 10 feet into the very stiff to hard silt and clay or dense sands underlying the site. Recommended axial capacities are presented in the table on page 15 and in figures A- 65 through A-68. Assumed pile loading conditions are presented in Figure A-64. One of the loading conditions presented in Figure A-64 is that zero skin friction should be considered in the potentially liquefiable soil zone. It appears that this liquefaction -state Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Plat, South 160th Street and 53rd Avenue South, Tukwila, WA Project No.: 06-373 Date: July 19, 2008 loading condition may be factored into the axial capacities in the table on page 15 of the report, but not in the axial capacities presented in Figures A-65 through A-68. We recommend that ORA verify this and revise both the table and figures to provide clarification. Additionally, we recommend that axial capacities be referenced to boring locations or to specific portions of the proposed development area, rather than to subsurface profiles as currently shown in the Table on page 15 of the geotechnical report. ORA Response: The discrepancy observed between the table on page 15 and the figures on pages A-65 through A-68 has been amended. We have attached a letter that includes an updated table that reflects axial shaft capacity values for an assumed 40 foot drilled shaft length based on subsurface conditions observed at borings 8-1 and 8-3. The presented drilled shaft designs include an assumed zone of zero skin friction to account for a liquefaction -state loading condition and zero tip resistance along the shaft length. If you have any questions please contact us. Attachment: Sincerely, Otto Rosenau & Associates, Inc. 62, Anthony G. Coyne, P.E. Geotechnical Engineer Figure titled "Result of Liquefaction Analysis at B-2 (Updated) Letter titled "Updated Drilled Shaft Design, Response to Third Geotechnical Peer Review, La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, Washington, King County Parcel # 5379200005 and 5379200006, ORA Project Number: 06-373, Report 3 Otto Rosenau & Associates, Inc. Page 2 of 2 Depth below Ground Surface (ft) 0 10 20 30 40 50 60 70 80 Factor of Safety Against Liquefaction B-2 0 2 nedium dense Silty (SM) and Fine Sand P -SM). wet at about 17.5 feet. L). Moist to wet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983) and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. Granular soils with (N1)60 blow counts greater than or equal to 30 are considered to dense to liquefy. Non -liquefiable soils are shown as having a factor of safety equal to 1.5. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-2 (UPDATED Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St , Tukwila, Washington Date: June 27, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-61 r --- i � I lEBecomes Loose to , Fine Sant --- withSilt(, 1 I - 1 1 Stiff to hard Silt (1 1 ilk, � II III IIIr r nedium dense Silty (SM) and Fine Sand P -SM). wet at about 17.5 feet. L). Moist to wet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983) and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. Granular soils with (N1)60 blow counts greater than or equal to 30 are considered to dense to liquefy. Non -liquefiable soils are shown as having a factor of safety equal to 1.5. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-2 (UPDATED Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St , Tukwila, Washington Date: June 27, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-61 MAY -09-2008 FRI 11:26 AM May 8, 2008 FAX NO. P. 02 SHANNON &WILSON, INC. ALASKA CALIFORNIA CIO FLORIDA GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS MISSOURI CIFaiC]N WAAHINCITON Ms. Joanna Spencer City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 RE: THIRD GEOTECHNICAL PEER REVIEW, LA TOURELLE PLAT, SOUTH 160" STREET AND 53RD AVENUE SOUTH, TUICJLA, WASHINGTON Dear Ms. Spencer: This .letter presents review comments on the recently revised geotechnical engineering report and development plan for the above -referenced project in Tukwila, Washington. The proposed development is located on undeveloped land northwest of the intersection of South 160th Street and 53`iJ Avenue South. We understand the development area has been reduced significantly and will be located within "the most geologically stable portion of the site," as recommended by Otto Rosenau & Associates, Inc. (ORA). In this letter, we offer an opinion as to the appropriateness and adequacy of the revised geotechnical report and responses prepared by ORA. Our opinion is based on our review of the following documents: ► A letter prepared by Barghausen Consulting Engineers, Inc., entitled, "Resubmittal of Geotechnical Evaluation Reports in Response to Peer Review Comments for City of Tukwila Project N. L06-089, Proposed Development of La Tourelle, Our Job No. 12650," dated March 21, 2008. P. A letter prepared by Otto Rosenau & Associates, Inc., entitled, "Response to Second Geotechnical Peer Review Comments, Proposed La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, Washington, King County Parcel #5279200005 and 5379200006, ORA Project Number: 06-373, Report No. 3," dated March 11, 2008. P. A letter prepared by Tubbs Geosciences, entitled, "Geologic and Slope Stability Conditions, Proposed La Tourelle Plat, Tukwila, Washington, File No. BAR4-01," dated March 11, 2008. ► A report prepared by Otto Rosenau & Associates, Inc., entitled, "Geotechnical Engineering Report, Proposed La Tourelle Plat, South 160th St and 53'' Ave S, Tukwila, Washington, King County Parcels #5379200005 and #5379200006," dated March 11, 2008. 400 NORTH 34TH STREET • SUITE 100 P.O. BOX 300303 SEATTLE. WASHINGTON 96103 206.632.8020 FAX 208•685.6777 TOD: 1.800.833.6388 21-1-20689-003 LO -Ogg MAY -09-2008 FRI 11:27 AM Ms. Joanna Spencer City of Tukwila May 8, 2008 Page 2 FAX NO. P. 03 REVIEW COMMENTS SHANNON&WILSON, INC. In our October 25, 2007, peer review letter, we provided comments pertaining to the following items: the suspected sag pond feature (i.e., Wetland 3), conflicting groundwater level readings, liquefaction analysis results, estimated liquefaction -induced settlements, slope stability analysis parameters and results, setback and buffer distances, and pile -supported foundations. ORA addressed all of our review comments and, in general, their revised geotechnical recommendations for the reduced development proposal are satisfactory. The following are minor comments resulting from our review of ORA's revised geotechnical report dated March 11, 2008: ► During our second peer review, we observed and stated that there was a discrepancy between the number of samples analyzed for liquefaction and the number of samples retrieved/tested in boring 13-2. Liquefaction results for boring 1-2 were presented in Figure A-62 of ORA's August 2007 geotechnical report and now are presented in Figure A-54 of the revised geotechnical report. The discrepancy has not been corrected. We recommend checking the analysis and correcting the figure for completeness, even though boring 13-2 is not within the revised development boundaries. ► Section 11.3.2 of ORA's revised report presents recommendations for designing drilled shaft foundations. ORA recorrunends that the shafts should be at least 40 feet long and at least 10 feet into the very stiff to hard silt and clay or dense sands underlying the site. Recommended axial capacities are presented in the table on page 15 and in Figures A-65 through A-68. Assumed pile loading conditions are presented in Figure A-64. One of the loading conditions presented in Figure A-64 is that zero skin friction should be considered in the potentially liquefiable soil zone. It appears that this liquefaction -state loading condition may be factored into the axial capacities in the table on page 15 of the report, but not in the axial capacities presented in Figures A -6S through A-68. We recommend that ORA verify this and revise both the table and figures to provide clarification. Additionally, we recommend that axial capacities be referenced to boring locations or to specific portions of the proposed development area, rather than to subsurface profiles as currently shown in the Table on page 15 of the geotechnical report. 21 -00689 -003 -LI .dnu/wp/LK I) 21-1-20689.003 MAY -09-2008 FRI 11:27 AM Ms. Joanna Spencer City of Tukwila May 8, 2008 Page 3 CONCLUSION FAX NO. P. 04 SHANNON iWILSON. INC. In general, the revised geotechnical report is acceptable for the currently planned development; however, we recommend that the Geotechnical Engineer -of -Record address the two continents above to minimi=ze potential misunderstanding related to the estimated liquefaction depths and pile design. Please note, comments made during the review proccss do not relieve the project applicant or designer from compliance with code requirements, conditions of approval, or permit requirements; nor is the designer relieved of responsibility for a complete design in accordance with the laws of the State of Washington. This peer review is a check for compliance with generally accepted professional geotechnical engineering principles and practices used by geotechnical engineering firms in this area. We appreciate the opportunity to be of service. If you require any additional services, we are available at (206) 632-8020. Sincerely, SHANNON & WILSON, INC. ureen M. Beintunl, P.E. Senior Engineer LMB:MWP/lmb 21-1-20689.003-LJ.aoe/wp/I.KD 1EXPIRES: O4/21/!D j Martin W. Page, P.E., L.E.G. Associate 21-1-20689-003 TO: .r'' Building L Planning City of Tukwila Department of Community Development File Number Lo' LAND USE PERMIT ROUTING Public Works Fire Dept. Date transmitted: C7104L if/ 3 (, j cacc Staff fe) M • coordinator: 10." I ► 1 t') REVIEWERS: Please specify how the development regulations, including citations. want made to the plans. When referencing plan change needed. Response / 7 requested by: / ( 0 Date response received: attached plans conflict with your ADOPTED Be specific in describing the types of changes you codes, please identify the actual requirement and The Planning Division review does not supplant each department's ability to administer its own regulations and permits. However, project consistency at the Planning review stage is important to minimize significant later design changes. More than minimal design changes require further Planning Commission review, even if alteration is required to satisfy a City requirement. This further review is typically a minimum 60 -day process. Requirements based on SEPA (e.g., not required by an adopted development regulation) MUST identify the impact being mitigated, the policy basis for requiring mitigation, and the method used to calculate the mitigation required. Calculations of project impacts and the mitigation required (e.g., water capacity, road level of service analyses, or tuming analyses) may be required of the applicant. COMMENTS (Attach additional comment sheets and/or support materials as needed.) ;gyp ccaw►veyP;r;6- tiC � � VIs', v_e ctzue� D S 44-36 f e r ri" f it1'E�`+ ) 4 -tri b T� 1r S kl1 } S / q � S . ! -C e o IS.) We_ yid b o` a ,TIS �ie o (re kino,,e-k;,o,� S) D Ve. 5 ) b -e teicr n d 6u-e.04t„c) burs. Plan check date: I -i --3 -p 'g Comments prepared by: E-T-- Update date: City of Tukwila Department of Community Development LAND USE PERMIT TO:d Building Planning Public Works Project: Address: File Number L o .2cf ING F�Fn Fire Dept. Date transmitted: Staff coordinator: C7AL 2cot ift 3(12 - 53-1(1.x.9 -D�� Response requested by: Date response received: Police Dept. Parks/Rec c,j 1j "ra,K.1164 REVIEWERS: Please specify how the attached plans conflict with your ADOPTED development regulations, including citations. Be specific in describing the types of changes you want made to the plans. When referencing codes, please identify the actual requirement and plan change needed. The Planning Division review does not supplant each department's ability to administer its own regulations and permits. However, project consistency at the Planning review stage is important to minimize significant later design changes. More than minimal design changes require further Planning Commission review, even if alteration is required to satisfy a City requirement. This further review is typically a minimum 60 -day process. Requirements based on SEPA (e.g., not required by an adopted development regulation) MUST identify the impact being mitigated, the policy basis for requiring mitigation, and the method used to calculate the mitigation required. Calculations of project impacts and the mitigation required (e.g., water capacity, road level of service analyses, or turning analyses) may be required of the applicant. COMMENTS (Attach additional comment sheets and/or support materials as needed.) ge.. r y q�' f-'� e rs �:�� ‘ok Ebc i2 -SL -e cc.fLS S , u Ate` S kb 1P -e- c-ev ..,<.t . �.vn Ci)r-cv Yvv-ck\vA$ .ton 'c ' (des i Ve.,. c.K. c IN \;ASI -t-c, 6E -E c. u is -175s.:c s . Plan check date. dk-\\,C)b Comments prepared by\a y1 Update date: I/ .2 ' oy�` y. 1 <r�~G ENG%N*fr Minnie Dhaliwal, Senior Planner City of Tukwila Department of Community Development 6300 Southcenter Boulevard Tukwila. WA 98188 CIVIL ENGINEERING, LAND PLANNING. SURVEYING, ENVIRONMENTAL SERVICES March 21, 2008 COURIER DELIVERY RECEIVED MAR 21 2008 COMMUNITY DEVELOPfidENT RE: Resubmittal of Geotechnical Evaluation Reports in Response to Peer Review Comments for City of Tukwila Project No. L06-089 Proposed Development of LaTourelle Our Job No. 12650 Dear Minnie: Since the fall of 2007 we have been working diligently with officials from Otto Rosenau & Associates, Inc. to prepare a comprehensive supplemental report and response to the peer review comments received from Shannon and Wilson, Inc., dated October 25, 2007 for the project known as LaTourelle. Enclosed with this letter are five copies of this updated report identified as "Report No. 3" dated March 11, 2008, together with three other documents. These include a response from Mr. Donald W. Tubbs, Ph.D., a Professional Engineering Geologist as requested by Shannon and Wilson, Inc., a detailed point -by -point response letter dated March 11, 2008, from Otto Rosenau & Associates, Inc., which responds to each comment provided by Shannon and Wilson, Inc., in their last 2007 review of the geotechnical information submitted for this project, and a proposed site plan. We are also including five copies of the revised development concept for LaTourelle, which is now substantially different than originally proposed. As you know from our meeting on this revision held on December 18, 2007, the project intensity has been substantially reduced from 16 Tots to an 8 -lot short plat in the City of Tukwila. The project now limits development to what has been identified by Otto Rosenau & Associates, Inc., as the areas suited for development where potential impacts associated with the on-site geotechnical conditions can be mitigated such that the construction of eight homes will not have a significant adverse impact on the property or the surrounding properties, and where such homes can be built safely in accordance with applicable regulations. The new project almost entirely eliminates grading on the property, except as may be associated with single-family home foundation construction, and a sewer line extension and storm line along the back of the lots from 53rd Avenue South. The revised report: from Otto Rosenau & Associates, Inc., includes a summary of specific mitigation measures for single-family home construction, which would be incorporated at the time of building permits for the individual lots. Construction requirements for the short plat would be effectively limited to installation of sidewalks along the frontage with 160th Avenue South and extending around along a portion of 53rd Avenue South to connect to the existing sidewalk near the northeast corner. By eliminating virtually all grading on the site, we are no longer incorporating the intensity of activity previously anticipated, which is in direct response to the geotechnical evaluation and recommendations. ,4 to\ A) 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES • OLYMPIA, WA • TACOMA, WA • SACRAMENTO, CA • TEMECULA, CA www.barghausen.com Minnie Dhaliwal, Senior Planner City of Tukwila Department of Community Development -2- March 21, 2008 The other important change to the project is that we have eliminated all impacts to the small on-site wetlands, one of which was previously proposed to be filled in the center of the property. Both wetlands are now being preserved in their entirety, along with their required buffers, without any change to the buffers or request for buffer averaging. Approximately 60 percent of the property is now being left as permanent open space, which includes both wetlands and their buffers, as well as the steep slopes along 53rd Avenue South. Please forward this information to Shannon and Wilson, Inc., including this cover letter and the proposed site plan illustrating the revised development concept that will be pursued through a short plat, so that they have a clear understanding that the scope of the project has changed in response to their initial comments and consequent work completed by Otto Rosenau & Associates, Inc. We believe we have addressed every comment from Shannon and Wilson, Inc., and hope that we can move forward with a Preliminary Short Plat Application once we complete this peer review process. Thank you. Respectfully, Thomas A. Barghausen, P.E. President TAB/tep 12650c.020.doc enc: As Noted cc: Joe Amon (w/enc) Alexia D. Dorsch, Barghausen Consulting Engineers, Inc. f - 40' 1,i° ; PRELIMINARY SHORT PLAT MAP FOR LA TOURELLE A PORTION OF THE NW 1/4 OF SECTION 28, TOWNSHIP 23 N, RANGE 4 E, WM TUKWILA, WASHINGTON LEGAL DESCRIPTION O ON L. 5.5 nam 354501 23 x51x.. 120...1. MOST CORNER OF 3510 =TM NO SOM. WOO' 23.06 FR. O. SOWN 40, E4 40. m 1 ,ER M .E 1O 51 W O 5340 NOW SOTx. aS. 2110401 SOON 21 OW UST 3417 On 5.014 SOTTO 314... 451 .40 FRS 4 M .OR1xOSR.CT ORM OW ST• ,FO,• MOO ..ICM SATO 46I01002 wow 60M 26-07I' 033 131,1 rt0: KM. 105505. 1x4 30565 FBF,: 01340 TORT .025 0 1x0.7 „•x9 FRT: M. NOM 5.000-.tS 25412 F¢, W M PONT O 0x45002 434 POO 4 . ,0071007 s CM 1. F3O 1. 1014. Ota TO M 660[000 FLO noon ,S WOOF c ., 400361224 0.11 NOM 0304.0m M SWIMS, OWNER OF INE .1O.x OWN. TO . ,.04 NOM .610 M 44 l.[ OF 5.50 TOM. MCI ,u. FRS. Txpia 93.110011.• Os 5 313. 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TOT) 321-17T AOC Ma15OMITTO,at 'KW N.• �,,, 204431 0420 ow NOM MUNN 4 5, I IVO [24-324 MINA 422 WORM. MN. .4.4 U5.) 525-44M 15675 =1410, 004 W-2.,1 OWNER/DEVELOPER No0 WOO NON 04.74 WO nw..w4ROI Falx O • 1203 4.-055 ENGINEER/PLANNER/SURVEYOR MOOR. C.5020K 0062. NC. Wei TOTS SOM Y 23 n n-324 5CON is *w Son. 4.02.03, ORS. ej e� $ t s!i ► OTTO ROSENAU & ASSOCIATES, INC. March 11, 2008 Mr. Jawaid Amon 16424 53rd Place South Tukwila, Washington 98168 Geotechnical Engineering, Construction Inspection & Materials Testing 6747 M. L. King Way South, Seattle, Washington 98118-3216 USA Tel: (206) 725-4600 • Toll Free: (888) OTTO-4-US • Fax: (206) 723-2221 WBE W2F5913664 • WABO Registered Agency • Website: www.ottorosenau.com Re: Geotechnical Engineering Report Proposed La Tourelle Short Plat South 160th Street and 53rd Avenue South Tukwila, Washington King County Parcel # 5379200005 and 5379200006 ORA Project Number: 06-373, Report 3 Dear Mr. Amon: We are pleased to provide this revised report for the referenced project. The revisions to the original report are based on review comments provided by the City of Tukwila and Shannon & Wilson. Based on our subsurface explorations and our analyses, we determined that the site is stable under static loading conditions, but will likely be unstable during an International Building Code (IBC) level seismic event if the vulnerable soil layers liquefy. For the purposes of this report, we consider an IBC level seismic event to be a seismic event with a peak ground acceleration of 36% of the acceleration due to gravity and a 2,475 year recurrence interval. We propose to mitigate for this scenario by providing a robust deep foundation system to support the future residential structures. The residential structures may sustain some damage during large scale earth movements, but should allow the safe exit of the occupants after the event. We have estimated that the maximum lateral movement of the proposed structures, built as recommended in this report, should be on the order of a few inches in the event of a seismic event that liquefies the vulnerable underlying soils and causes slope instability at the site. The primary ways that the risk of future slope instability can be reduced and the detrimental effects of future slope instability can be minimized is to incorporate the following measures into the development of the project site. • Limit the area of development to the most geologically stable portion of the site as shown on page A-52 of the appendix. The remainder of the site should remain in its current undeveloped condition. • The soils at the site appear to be vulnerable to liquefaction during an IBC level seismic event, in particular in the vicinity of B-1. We recommend that the new residential structures be supported Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, WA Project No.: 06-373 Date: March 11, 2008 on deep foundation elements that will resist the lateral forces induced by a slope failure if liquefaction occurs following such an event. • The residential structures should be oriented with the narrow dimension of the structure adjacent to South 160th Street. The long dimension of the structure should be oriented to follow the direction of the slope of the hillside. This will help minimize the amount lateral force that can be generated against below -grade foundation elements in the event of slope instability. • The residential structures should have a minimal amount of embedment into the hillside to reduce the amount of lateral force that can be generated against below -grade foundation elements in the event of slope instability. • The residential structures should incorporate reinforced concrete grade beams. Grade beams are continuous foundation elements in which the deep foundation elements are embedded into. Interconnecting grade beams will provide a rigid foundation upon which the superstructure can be built upon, and will help reduce the risk of differential movement or settlement at different parts of the same structure. • The water from new impervious surfaces and foundation drains should be collected and routed offsite to enhance the stability of the site slopes. • This site is not suitable for on-site infiltration of stormwater runoff from impermeable surfaces such as roadways, paved surfaces, and roofs. All piping and detention facilities should be designed to reduce exfiltration into the adjacent soils. Detailed earthwork and foundation recommendations are presented in the attached report. If you have any questions, or if we may be of additional service, please contact us. Copies to: Addressee (8) Sincerely, Otto Rosenau & Associates, Inc. Anthony G. Coyne, P.E. Geotechnical Engineer TABLE OF CONTENTS 1. INTRODUCTION 1 2. PROJECT DESCRIPTION 2 3. SCOPE OF SERVICES 2 4. SITE CHARACTERIZATION 2 5. SURFACE CONDITIONS 3 6. SUBSURFACE CONDITIONS 4 7. LABORATORY TESTING 5 8. REVIEW OF LITERATURE 6 9. PAST SLOPE INSTABILITY 7 9.1 Regional Slope Instability 7 9.2 On Site Slope Instability 8 10. DISCUSSION 9 11. CONCLUSIONS AND RECOMMENDATIONS 9 11.1 General 9 11.2 Seismic Considerations 11 11.3 Foundations 13 11.3.1 Shallow Foundations 13 11.3.2 Drilled Shafts 14 11.3.3 Drilled Shaft Settlement 16 11.3.4 Drilled Shaft Installation 16 11.4 Below -Grade Walls and Retaining Walls 17 11.5 Slabs -on -Grade 17 11.6 Earthwork 18 11.6.1 Site Clearing 18 11.6.2 Structural Fill 18 11.7 Site Slopes 20 11.7.1 Permanent Slopes 20 11.7.2 Temporary Slopes 21 11.7.3 Setbacks and Buffers 21 11.8 Slope Stability Analysis 21 11.9 Erosion and Sedimentation Control 24 11.10 Drainage 24 11.10.1 Construction Dewatering 24 11.10.2 Surface Drainage 25 11.10.3 Subsurface Drainage 25 11.11 Construction Observation and Testing 25 12. REPORT LIMITATIONS 25 Vicinity Map A-1 LIDAR Image Vicinity Map A-2 Site Plan A-3 Boring Logs A-4 Boring Log Notes A-21 Unified Soil Classification System A-24 Geologic Cross Section A -A' and C -C' A-25 Geologic Cross Section B -B' A-26 Geologic Cross Section D -D' A-27 Geologic Cross Section E -E' A-28 Geologic Cross Section F -F' A-29 Shannon & Wilson Geologic Cross Section B -B' A-30 Atterberg Limit Test Results A-31 Particle Size Distribution Report A-32 Direct Shear Test Results A-47 Location of Geologically Most Stable Area A-52 Result of Liquefaction Analyses A-53 Slope Stability Analyses A-56 Assumed Pile Loading Model A-64 Allowable Axial Capacity vs. Pile Length Analyses A-65 Typical Foundation Detail A-68 APPENDIX B Report titled "Geologic and Slope Stability Conditions by Tubbs Geosciences dated March 11, 2008 GEOTECHNICAL ENGINEERING REPORT PROPOSED LA TOURELLE SHORT PLAT SOUTH 160TH STREET AND 53RD AVENUE SOUTH TUKWILA, WASHINGTON KING COUNTY PARCELS # 5379200005 AND 5379200006 REPORT NO. 3 Prepared for Mr. Jawaid Amon by Otto Rosenau & Associates, Inc. March 11, 2008 1. INTRODUCTION This revised report presents the results of our geotechnical engineering services for the proposed residential development in Tukwila, Washington. This revised report presents a geotechnical evaluation for a significantly scaled back development. The currently proposed development is for a short plat of eight Tots to be limited to the most geologically stable portion of the project site. This significant revision to the project has been prompted by review of recently -available Light Detection and Ranging (LIDAR) imaging for the project site, which presents evidence that the project site is located within a landslide complex that is approximately 'A miles in width. Please refer to the LIDAR Image Vicinity Map on page A-2 of Appendix A. It is our opinion that this large area of past slope instability is likely a result of several geologic processes including glacial scour, ice -marginal erosion, relatively high groundwater levels, groundwater seepage, deglacial and postglacial backscarp failures, and possibly liquefaction of near -surface, saturated, sandy soils. Dr. Donald Tubbs, Ph.D., L.G., L.E.G. of Tubbs Geosciences has been included as a member of the design team to assist in evaluating the complex geology at the project site. Dr. Tubbs has provided geological review services on this project. Dr. Tubbs and Otto Rosenau & Associates, Inc. (ORA) completed a visual reconnaissance of the project site and the adjacent areas on December 31, 2007 and on February 18, 2008. Dr. Tubbs' report is included in Appendix B of this report. Our original report for this project was titled "Geotechnical Engineering Report, Proposed Tukwila Residential Development, South 160th Street and 53rd Avenue South, Tukwila, Washington, King County Parcel # 5379200005 and 5379200006, ORA Project Number: 06-373, Report 1" and was dated August 15, 2006. We have incorporated our response to review comments provided by Shannon Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 2 of 26 & Wilson in their October 25, 2007 peer review of our Report No. 2 for the project dated August 29, 2007 into this current report. 2. PROJECT DESCRIPTION Based on current project information, we understand that the project involves creating about 8 new building Tots along South 160th Street in Tukwila, Washington. The area to be developed extends approximately 150 feet to the north of South 160th Street and approximately 450 feet west of the intersection of 53rd Avenue South and South 160th Street. The building lots will be accessed from South 160th Street. The remainder of the site will remain fully undeveloped and in its current state. A 50 -foot wide buffer zone will be included around the mapped wetlands. The location of the site is shown on the Vicinity Map on page A-1 of Appendix A. 3. SCOPE OF SERVICES The original scope of services included a reconnaissance of the site by the geologist, a review of geologic literature, and witnessing the drilling of five borings (B-1 through B-5) and installation of two ground water monitoring wells at borings B-1 and B-2 in June 2006. Three additional drilling explorations (B-6 through B-8) were completed in April 2007. A hand auger (HH -1) exploration was completed on February 19, 2008. The approximate location of the explorations is shown on the Site Plan on page A-2 of Appendix A. The geotechnical engineering services were performed by ORA to provide the following information: • seismic design considerations including liquefaction potential, • allowable bearing capacity and depth of suitable foundation systems with estimated settlements, • lateral earth pressures and friction coefficients, • slope stability analysis, • influence of groundwater on the development, and • site preparation, earthwork and temporary cut slope recommendations. 4. SITE CHARACTERIZATION We reviewed the "Geologic Map of The Des Moines 7.5' Quadrangle, King County, Washington", 2004 by Booth, Derek B. and Waldron, Howard H. The soils in the vicinity of the project site are predominantly mapped as Deposits of the Vashon Stade of Fraser Age glaciation. These deposits consist of recessional outwash (Qvr), till (Qvt), and recessional Iacustrine deposits (QvrI). (Qvr) Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 3 of 26 typically consist of stratified sand and gravel, moderately, well sorted to well sorted; typically deposited in outwash channels. (Q,,) consist of compact diamict containing sub -rounded to well-rounded clasts in massive, silt or sand rich matrix, which is glacially transported and deposited. (Q,d) consist of very fine grained sand, silt and clay deposited in small lakes during glacial ice recession. The City of Tukwila considers the project site to be located within a Sensitive Area. In particular, the site is considered to be a Class 4 Area of Potential Geologic Hazard due to the presence of slopes with very high landslide potential and/or mapped landslide deposits. 5. SURFACE CONDITIONS The site consists of two adjacent parcels that form an irregular shape. The site is bounded on the south and southwest by South 160th Street, along the east side by 53rd Avenue South. The north boundary of the site includes a Seattle Public Utilities water line easement with South 159th Street immediately to the north of it. The site grades slope downwards to the northeast from approximately Elevation 290 feet near the intersection of 51st Avenue South and South 160th Street to Elevation 196 feet at the northeast property corner the intersection of 53rd Avenue South and South 159th Street. The majority of the elevation change is located at the northeast section of the site (Elevation 196 feet to Elevation 236 feet). The proposed area to be developed is to be located in the eastern two-thirds of the site with access from South 160th Street at the southeast corner of the site. The western third of the site is to remain undeveloped. The site is located on a greater slope that extends upwards to the southwest and downwards towards the 1-5 / 1-405 interchange. There is a fairly level area at the southeast corner of the site near the intersection of South 160th Street and 53rd Avenue South. South 160th Street rises to the west and a concrete retaining wall is located along much of the South 160th Street right-of-way that borders the site. The Seattle Public Utilities water line easement along the north side of the site contains a delineated wetland and a drainage ditch that drains to the northeast under 53rd Avenue South. Steep slopes are present at the east side of the site along 53rd Avenue South. Portions of the slopes appear to have been built up as an embankment at the approximate location of the historic structures and driveways that used to be present on the site. Other steep slope areas appear to be cut slopes related to past legal roadway construction. The site has three delineated wetlands as identified by Mead, Gilman and Associates in their survey dated January 6, 2006. The site is heavily vegetated with holly, ivy and deciduous trees, a combination of mostly maple trees up to 50 inches in diameter and alder trees of various sizes. There is evidence of past development and grading activities on the site based on presence of fill embankments and linear features that appear to have been driveways. The site has also been used, until recent times, as an uncontrolled dump site. The dumped materials include household waste, wood and metal construction Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 4 of 26 debris, soil, rock, and concrete rubble. Based on our review of historical maps, there appeared to have been several structures (likely residential) present on the site with access from the southeast corner of the site. The area described as Wetland 3 on our site plan was identified as a potential sag pond. Borings B-6 through B-8 were completed near Wetland 3 on our Site Plan to evaluate the subsurface conditions and to identify any subsurface conditions that would support the assertion that this low-lying area is a slide - related feature. Based on the linear nature of this feature and the presence of a significant amount of wood debris and organic soils at depths up to 14 feet below the existing site grade in boring B-8, it is our opinion that this area is likely a sag pond related to past slope instability through the upper zone of loose to medium dense sands. Hummocky terrain is present at portions of the site, in particular in the vicinity of Wetland 3. However, the area adjacent to Wetland 3 is outside the proposed limits of the current development. 6. SUBSURFACE CONDITIONS We evaluated the subsurface soil and groundwater conditions by completing five borings (B-1 through B-5) at the site using a subcontracted, track -rig mounted, hollow -stem auger, and mud rotary drilling equipment between June 20 and 23, 2006. Borings B-6 through B-8 were completed on April 6, 2007. Borings B-1 through B-3, and boring B-5 were completed using mud rotary drilling techniques. Boring B-4, and borings B-6 through B-8 were completed using hollow -stem auger drilling equipment. HH -1 was completed using hand auger equipment on February 19, 2008. The following table summarizes the depths of borings completed for this project. Boring Depth Below Existing Grade (feet) Drilling Method Ground Surface Elevation (feet) Groundwater Level (feet below ground surface) B-1 101.5 Mud Rotary 256 18 feet on 6/21/06, 3 feet on 6/6/07 B-2 81.5 Mud Rotary 205 20 feet on 6/21/06, 17.5 feet on 6/6/07 B-3 66.5 Mud Rotary 228 24 feet based on lab testing B-4 51.5 Hollow Stem Auger 228 11 feet observed during drilling B-5 51.5 Mud Rotary 243 3 feet observed during drilling B-6 51.5 Hollow Stem Auger 232 31 feet observed during drilling B-7 51.5 Hollow Stem Auger 226 15 feet observed during drilling B-8 51.5 Hollow Stem Auger 224 7 feet observed during drilling Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 08-373 March 11, 2008 Page 5 of 26 Boring Depth Below Existing Grade (feet) Drilling Method Ground Surface Elevation (feet) Groundwater Level (feet below ground surface) HH -1 10.0 Hand Auger 275 6 feet observed during exploration Please refer to the Site Plan on page A-3 of Appendix A for the approximate location of the borings. The details and explanations of our explorations are presented on pages A-4 through A-24 of Appendix A. Similar soil conditions were observed at each boring location with an upper zone of loose to dense sand with varying silt content ranging from 21 to 46 feet in thickness over stiff to hard sandy silt, silt and lean clay. We did not observe indications of a slide plane in any of our explorations as might be evidenced by slickensides or a highly disturbed zone. We prepared several geologic cross-sections of our interpretation of the geologic soil conditions at, the site that are presented on pages A-25 through A- 28 of Appendix A. The locations of the geologic contact between soil units and the elevation of the groundwater was estimated between the boring locations, and should be considered to be approximate. The approximate location of these cross-sections is presented on our Site Plan. We also have included a geologic cross-section based on a figure "Generalized Soil Profiles A -A' and B -B' from a letter titled "Geotechnical Review of Proposed LeRoy Lowe Development, Tukwila Washington" prepared by Shannon & Wilson on page A-29 of Appendix A. The approximate location of this cross-section is presented on the LI DAR Image Vicinity Map. Supplemental Borings B-6 through B-8 were completed to evaluate the subsurface conditions at a possible sag pond feature identified as Wetland 3 in our Site Plan. We performed nearly continuous sampling in the upper 18 to 20 feet at each location to try and identify any past failure planes. Supplemental exploration HH -1 was completed to evaluate the subsurface conditions at the western boundary scarp face along the south side of South 160th Street. Groundwater was observed during drilling at most of our explorations. The mud rotary drilling technique makes direct observation of water levels in borings difficult. A 2 -inch diameter PVC standpipe piezometer was installed at borings B-1 and B-2 in the upper sandy soils overlying the stiff to hard silts. Please refer to the boring logs for details of well construction at B-1 and B-2. The groundwater levels at the site will likely vary with season and precipitation. 7. LABORATORY TESTING We performed a wide range of laboratory tests on representative soil samples at the ORA soils laboratory. The tests performed include the following: Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2006 Page 6 of 26 • Moisture content determinations: results are presented on the boring Togs. • Atterberg limit determinations (ASTM D 4318): results are presented on page A-30 of Appendix A. • Grain size analyses (ASTM D 422): results are presented on pages A-31 through A-45 of Appendix A. • Direct shear test (ASTM D 3080): results are presented on pages A-45 through A-50 of Appendix A. Direct shear tests were performed by HWA Geosciences in Lynnwood, Washington. 8. REVIEW OF LITERATURE We reviewed several geotechnical reports that were completed in the vicinity of the project site. These included the following projects: • Hillcrest Residential Development located upslope and south of the project site. Cascade Geotechnical Inc. completed a geotechnical investigation and a series of subsequent responses to the City of Tukwila's review comments. Shannon & Wilson, Inc. provided geotechnical review services for the City of Tukwila. The correspondence that we reviewed is dated between 1992 and 1993. The location of the Hillcrest Residential Development is very close to the scarp of the large landslides that occurred in the 1960s during the construction of the 1-5 / 1-405 Interchange. The landslide was remediated partially by installing horizontal drains on WSDOT right-of-way. It appears that the horizontal drains have not been maintained by WSDOT and that several consultants have indicated that the factor of safety against slope failure at this site will continue to decrease as long as maintenance is not performed on the horizontal drains. • Five Rivers Development located downslope to the northeast of the project site. LSI Adapt, Inc. completed a geotechnical investigation and presented the results of their investigation in "Geotechnical Engineering Report, Five Rivers Preliminary Plat, 53rd Avenue S. and S. 159th Street, Tukwila, Washington" dated August 2001. LSI Adapt, Inc. prepared several subsequent engineering design supplements to address slope stability issues that were not initially addressed. Shannon & Wilson, Inc. provided geotechnical review services for the City of Tukwila on this project and concurred that LSI Adapt Inc.'s design approach satisfies the City of Tukwila's requirement for development in an environmentally -sensitive area. • 53rd Avenue South and South 160th Street Improvements project located along the south border of the site and extending to the west. Landau Associates, Inc. completed a geotechnical investigation for this project and presented their recommendations in "Geotechnical Study, 53rd Avenue South and South 160th Street Improvements, Tukwila, Washington" dated March 5, 1991. We also reviewed the project plans prepared by the City of Tukwila Public Works. We Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 7 of 26 were able to determine that the cast -in-place concrete retaining wall that is present along South 160th Street is a cantilevered retaining wall and appears to be supported on conventional spread footings. The report identified a roadway shoulder embankment failure that occurred west of the proposed development along South 160th Street. The report identified the presence of a substantial amount of loose fill at this location. The report does not address the issue of slope instability related to the headscarp along the south side of South 160th between 51St Avenue South and 53rd Avenue South. The report describes in detail a slope failure occurred during the construction of 1-5 in the early 1960s. The slope failure extended up to Slade Way at a location approximately 700 feet south of the project. 9. PAST SLOPE INSTABILITY 9.1 REGIONAL SLOPE INSTABILITY ORA reviewed recently -available LIDAR imaging for the project site, which presents evidence that the project site is located on a very large area of past slope instability. Please refer to the LIDAR Image Vicinity Map on page A-2 of Appendix A. The large area of past slope instability appears to be bounded approximately by Washington State Route 518, Klickitat Drive, Interstate Highway 5 and Slade Way along the north, northeast and south sides. The headscarp(s) of the area of unstable soils roughly parallels the toe of the slope. The project site appears to be located in relatively close proximity to the headscarp on the south side of South 160th Street. Shannon & Wilson, Inc. identified a "possible prehistoric slide scarp" in their map of the Tukwila Interchange revised in May 1968. The scarp was identified in this map as being located offsite on the far west boundary of the site and follows along the south side of South 160th Street adjacent to the south side of the site. Shannon & Wilson's report to the City of Tukwila, November 23, 1992, describes this slide scarp and estimates that displacements of up to 30 to 40 feet have occurred along portions of the 3,000 feet estimated length. Based on the site reconnaissances completed by Dr. Donald Tubbs and ORA on December 31, 2007 and on February 18, 2008, we estimate that the width of past slope instability approaches 4,000 feet. The western boundary scarp(s) appears to trend to the northwest nearly approaching Washington State Route 518 on the north side of the site and becomes obscured to the southeast towards Slade Way to the south of the site. During the site reconnaissances completed with Dr. Donald Tubbs, we looked for evidence of recent slope instability to determine how active the slide(s) may be. We did not observe any indication of recent slope instability in proximity to the headscarp(s) in developed areas where slide features may be manifested in uneven curb lines, cracked pavements, etc. This tends to indicate that there has been Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 8 of 28 little to no activity near the headscarp(s) in recent history. We observed abundant slide related features as described in Shannon & Wilson's 1968 map, including the large offset features at the headscarp along the length of the area of past slope instability. The headscarp features are not continuous and become obscure in several locations and may indicate that past slope instability may have occurred at different times at different locations. We understand that there are several peat deposits in low-lying areas near the slide scarp in nearby off-site areas, which supports the assertion that the slide has not been active in recent times. There have been numerous other slope failures identified in the vicinity of the site. One of the largest is a deep-seated slide that occurred just to the southwest of the site in 1960 during the construction of the 1-5 / 1-405 interchange. This slide was located along the lower edge of the large area of past slope instability. The lower edges of areas of previously unstable slopes tend to be more active than the upper areas located closer to the headscarp. We observed slide blocks and hummocky terrain at this area during our reconnaissance. We did not see evidence that the recent slope instability in this area had extended to 53rd Avenue South immediately adjacent to the site. It is our opinion that the landslide complex that includes the project site is likely a result of several geologic processes that likely include glacial scour, ice -marginal erosion and backscarp instability during and following the most recent glacial events approximately 13,500 years ago. We observed a discontinuity in the thickness of the sands in the western boundary scarp along South 160th Street and our nearest borings on the opposite side of South 160th Street, which indicates that he backscarp did not originate by offset along a deep-seated failure surface cutting through the underlying silt and clay. More recent slope instability in the landslide complex is probably a result of relatively shallow failures involving the upper loose to medium dense sands sliding over the stiff to hard silts and clays and the occasional dense sands. The subsurface soil layers generally appear to be generally inclined in a gentle downwards inclination. The presence of relatively shallow groundwater levels, groundwater seepage, and possibly liquefaction of near -surface, saturated, sandy soils perched above the relatively impermeable silt and clay layers could all be contributing factors to past slope instability. Please refer to Dr. Tubb's attached report in Appendix B for a detailed assessment of the geologic and slope stability conditions at the project site. 9.2 ON SITE SLOPE INSTABILITY There is evidence of recent slope instability on site as evidenced by severely leaning trees on the steep slopes along 53rd Avenue South. It is likely that the slopes in this area were oversteepened through legal grading activities during the construction of 53rd Avenue South. These slope failures are shallow Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 9 of 26 and relatively small slides that do not appear to be related to the large-scale slope instability that occurred across the landslide complex. There is also evidence of slope instability in the more distant past as manifested by the presence of apparent sag pond features at the approximate location of Wetlands 2 and 3. We observed the presence of wood debris and organic soils to depths of about 14 feet below the existing site grade at Boring B-8, which is adjacent to Wetland 3. We also observed a significantly increased depth to the silt/clay contact in Boring B-8 as shown in our,figure titled Geologic Cross -Section B -B'. The increased depth, at which the underlying very stiff to hard silt/clay layer is encountered at Boring B-8, could arguably be a result of slope instability that extended through the very stiff to hard silt/clay layer, but we interpret it to be an ice -marginal erosion feature. We did not encounter evidence of failure planes in our borings that might indicate failure planes extending through the very stiff to hard silt/clay layer. It is our opinion that the past slope failures at the project site most likely took place through the upper loose to medium dense sand near the contact with the underlying stiff to hard silt and clays and occasional dense sands. We were not able to obtain any historical records of slope failures at the project site. The presence of standing water in sag pond features can increase the risk of future slope instability by providing a conduit for water to more easily enter into zones of past slope disturbance. The stability of the hillside could be enhanced by preventing the accumulation of water in these areas. 10. DISCUSSION The recommendations presented in this report are based on our understanding of the project as presented in the Project Description Section and on the assumption that the subsurface conditions are as assumed herein. Project conditions, regarding type and location of structures and foundation Toads can change, and subsurface conditions are not always similar to those encountered during the subsurface exploration. Therefore, if discrepancies are noticed, the geotechnical engineer must be contacted for review and for possible revision of the recommendations. 11. CONCLUSIONS AND RECOMMENDATIONS 11.1 GENERAL The engineering recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical engineering practices in the area. The recommendations are based on our understanding of the geology of the area and on experience with similar projects. It is our opinion that it is possible to develop the site, provided that it is completed in accordance with the recommendations presented in this report. The primary concern for development in Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing_ La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 10 of 26 environmentally sensitive areas such as the project site is to not increase the risk of future slope instability. It is our opinion that it would not be economically feasible to stabilize the portion of the landslide complex which includes the project site. Instead, we recommend that development be limited to the portions of the site that are located furthest upslope adjacent to South 160th Street. Based on the results of our liquefaction and slope stability analyses, we determined that this portion of the site may experience slope instability if the soils beneath the site liquefy during an International Building Code (IBC) level seismic event. For the purposes of this report, we consider an IBC level seismic event to be a Magnitude 7.5 earthquake with peak ground accelerations equal to 36% of the acceleration due to gravity, and a 2,475 year recurrence interval. We propose to mitigate for this condition by designing the proposed residential structures to be resistant to movement by providing deep foundation elements, which extend through the upper unstable soils into the intact hard silt and clay layer or the very dense sand layers that underlie the site. The residential structures may sustain some damage during large scale earth movements, but should allow the safe exit of the occupants after the event. We have estimated that the maximum lateral movement of the proposed structures, built as recommended in this report, should be on the order of a few inches in the event of a seismic event that liquefies the vulnerable underlying soils and causes slope instability at the site. The primary ways that the risk of future slope instability can be reduced and the detrimental effects of future slope instability can be minimized is to incorporate the following measures into the development of the project site. • Limit the area of development to the most geologically stable portion of the site as shown on page A-51 of Appendix A. The remainder of the site should remain in its current undeveloped condition. • The soils at the site appear to be vulnerable to liquefaction during an IBC level seismic event, in particular in the vicinity of B-1. We recommend that the new residential structures be supported on deep foundation elements that will resist the lateral forces induced by a slope failure if liquefaction occurs following such an event. • The residential structures should be oriented with the narrow dimension of the structure adjacent to South 160th Street. The long dimension of the structure should be oriented to follow the direction of the slope of the hillside. This will help minimize the amount lateral force that can be generated against below -grade foundation elements in the event of slope instability. • The residential structures should have a minimal amount of embedment into the hillside to reduce the amount of lateral force that can be generated against below -grade foundation elements in the event of slope instability. • The residential structures should incorporate reinforced concrete grade beams. Grade beams are continuous foundation elements in which the deep foundation elements are embedded into. Interconnecting grade beams will provide a rigid foundation upon which the superstructure can Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 11 of 26 be built upon, and will help reduce the risk of differential movement or settlement at different parts of the same structure. • The water from new impervious surfaces and foundation drains should be collected and routed offsite to enhance the stability of the site slopes. • This site is not suitable for on-site infiltration of stormwater runoff from impermeable surfaces such as roadways, paved surfaces, and roofs. All piping and detention facilities should be designed to reduce exfiltration into the adjacent soils. 11.2 SEISMIC CONSIDERATIONS The seismic design of structures in the City of Tukwila is governed by the requirements of the 2003 International Building Code (IBC). The IBC requires that the site be classified into a site class. Based on the results of the soil exploration completed at the project site, it is our opinion that the observed conditions most closely meet the described conditions of Site Class D (IBC Table 1615.1.1). Site specific criteria can be obtained from maps in the IBC (Figures 1615(1) and 1615(2)) for short period (SS) and 1 -second -period (S1) spectral accelerations. The values for Ss and S1 are spectral response accelerations (SRA) for a maximum considered earthquake event with a 2,475 year return period, or a 2% probability of exceedance (PE) in 50 years. Values for SS and S1 are also available from the United States Geological Survey (USGS) National Seismic Hazard Mapping Project website. The values recommended for use in this report were obtained from the USGS website by inputting latitude and longitude for the project site (N 47.45943°, W 122.26734°). The 1996 data set from the USGS website was used for consistency with the relevant figures in the 2003 IBC. The following table presents recommended values from the 2003 IBC for seismic design: 2003 International Building Code (IBC) Seismic Design Values (2% PE in 50 years) Mapped max. earthquake SRA at short periods, Ss, % g 135.1 Mapped max. earthquake SRA at 1 -second period, S1, % g 46.5 Site Class Definition (Table 1615.1.1) D Site Coefficient Fa (Table1615.1.2(1)) 1.0 Site Coefficient F„ (Table1615.1.2(2)) 1.5 Max. considered earthquake SRA for short periods, SMS 135.1 Max. considered earthquake SRA for 1 -second periods, SM1 69.8 Design SRA at short periods, SDS 90.1 Design SRA at 1 -second period, SD1 46.5 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 12 of 26 2003 International Building Code (IBC) Seismic Design Values (2% PE in 50 years) Design Peak Ground Acceleration (Design PGA = Sips x 0.4, for period, T = 0) , % g 36.0 For the purposes of this report, we consider an IBC level seismic event to be a Magnitude 7.5 earthquake with peak ground accelerations equal to 36% g, and a 2,475 year recurrence interval. Liquefaction may be defined as the sudden Toss of strength of soil as the soil is subjected to a rapid cyclic loading, such as during an earthquake. The mechanism that allows this to occur is that excess pore water pressures are generated between the soil particles. This excess pore water pressure reduces the frictional contact between the soil particles and reduces the shear strength of the soil. If the earthquake is of large magnitude and duration, the soil can begin to behave more like a liquid than solid and "liquefy". In order for liquefaction to occur, several conditions must typically be present. These include the following: • Saturated soil. • Fine to medium sand matrix containing Tess than about 10 percent fines (soil that can pass a No. 200 sieve). • Very loose to medium dense soil conditions. This is usually defined as soils that have N - values of 15 or Tess. Based on the results of our explorations and our observation of the soil and groundwater conditions at the site, it is our opinion that the potential for liquefaction at the site is medium to high along the western portions of the site to be developed and low to medium along the eastern portions of the site to be developed. We completed a liquefaction analysis using the subsurface information and related laboratory testing collected from borings B-1 through B-3. The liquefaction analysis was completed in general accordance with "Seed's Simplified Procedure" with the suggested modifications proposed by Seed, Youd, et al. in "Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshop on Evaluation of Liquefaction Resistance of Soils" (Journal of Geotechnical and Geoenvironmental Engineering — October 2001). The analyses were completed assuming an IBC level seismic event (peak ground acceleration = 36% g and a 2,475 year recurrence interval). The silty soils with fines content greater than 50% are considered to be non -liquefiable. The sandy soils with (N1)80 blow counts equal to or greater to 30 were also considered too dense to liquefy. We have included figures presenting the estimated factor of safety versus depth at borings B-1 through B-3. These figures are presented on pages A-52 and A-54 of Appendix A. In general, the upper loose to medium dense sands, which are below the groundwater level, are vulnerable to liquefaction during an IBC level seismic event. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 13 of 26 Similarly, we estimated liquefaction -induced settlement using the subsurface information and related laboratory testing collected from borings B-1 through B-3. The Tokimatsu-Seed approach as described in "Geotechnical Earthquake Engineering" (Kramer, 1996) was used to evaluate liquefaction -induced settlement. Estimates for liquefaction -induced settlement are typically considered to provide an order of magnitude estimate of the possible settlement that may occur. The results of our liquefaction analyses are presented in the following table. Estimated Liquefaction -Induced Settlement Location Assumed Thickness of Potentially -Liquefiable Soils (feet) Estimated Liquefaction - Induced Settlement (inches) B-1 20 4.1 B-2 12 1.3 B-3 16 0.4 The most recent, significant, seismic event was the Nisqually earthquake which occurred on February 28, 2001 with a Richter magnitude of 6.8 and a peak ground accelerations in the Seattle area approaching 20% g. Little to no slope instability was reported in the Seattle area as a result of the earthquake. Significant structural damage did occur to buildings where the existing subsurface conditions tended to amplify the ground motion, such as in the area south of downtown Seattle, where Targe areas of hydraulically -placed fill are present over former tidal mudflats. It is important to note that there are no records or substantive on-site evidence that any seismically -induced slope failures occurred on this site or immediately adjacent areas during the 2001 Nisqually earthquake. 11.3 FOUNDATIONS We recommend that the proposed residential structures be supported on deep foundation elements such as drilled shafts that can resist large lateral loads that could develop in the event of future slope instability. Other deep foundation systems such as driven steel piles or augercast piles could also be considered for use on this project, but drilled shafts were selected for their reliability of installation, resistance to bending moments and lateral load carrying capacity. We recommend that the drilled shafts or other deep foundation elements be connected to a rigid framework that connects all of the deep foundation elements, such as a grade beam. A grade beam is a reinforced concrete, continuous foundation element, in which the deep foundation elements are embedded. Please refer to the Typical Foundation Detail on page A-67 of Appendix A. 11.3.1 Shallow Foundations: Small retaining walls (less than 4 feet in height), and lightly -loaded ancillary structures of low importance may be supported on shallow foundation elements. All shallow foundation elements for this project should be supported by at least a 2 -foot thick zone of structural fill Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 14 of 26 as measured from the design bottom of the foundation element. The overexcavation should extend laterally a distance at least equal to the overexcavation depth. We recommend that the following allowable bearing capacities be used for the design of conventional spread footings: Foundation bearing on a minimum 2 -foot thick zone of structural fill that extends to the native, re -compacted sandy soil or stiff silt: 2,000 psf If the recommendations in this report are followed, we estimate that maximum post -construction settlements will be less than three-quarters (3/4) of an inch and differential settlements will be less than one-half (1/2) of an inch between comparably loaded column footings or along a 25 -foot long section of continuous wall footing. We recommend that the minimum width of continuous footings be 1.5 feet and that the minimum size of column footings be 2 -foot by 2 -foot. AH foundation elements shall be embedded at least 18 inches below the lowest adjacent finished grade for frost protection and to meet the minimum code requirements as presented in Section 1805 — Footings and Foundations of the 2003 International Building Code (IBC). Passive resistance should be evaluated using an equivalent fluid pressure of 250 pounds per cubic foot (pcf) where grade beams are cast on structural fill or dense native soils and backfilled on both sides with structural fill compacted to at least 95 percent of maximum dry density (MDD). This value of passive pressure includes a factor of safety of 1.5. An ultimate coefficient of friction between footings and bearing soils of 0.35 may be used to resist lateral foundation Toads. If passive earth pressures are used in conjunction with base friction to resist lateral loads, reduce the ultimate coefficient of friction to 0.30. A factor of safety of 1.2 should be applied to these values. 11.3.2 Drilled Shafts: Based on the large anticipated lateral Toads and bending moments that could be developed in the event of slope instability, we anticipate that a drilled shaft element will be necessary. We anticipate that the drilled shafts selected for use on this project will be designed to be as efficient as possible, and still be able to resist the anticipated design loads. We estimate that the minimum drilled shaft diameter for use on this project will be 24 inches. The use of larger, higher capacity, drilled shafts is possible, but usually the added expense in having larger construction equipment on site outweighs the benefit gained in reducing the number of drilled shafts installed. As a result, we have performed our analyses based on the assumption that 24 -inch diameter drilled shafts Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 15 of 26 will be utilized. We have also assumed a preliminary loading scenario that may not be representative of the final design requirements, and should be re-evaluated as the actual design Toads are determined. We estimated the lateral pressures that would be exerted on the future foundation elements by examining the interslice forces from the slope stability analyses. The interslice were selected at the approximate location of the future structures at cross-sections B -B', E -E', and F -F'. The lateral forces from possible slope instability were modeled in our pile design as a 2,000 pound per square foot uniform load applied horizontally on the grade beam (assumed 3 -foot by 8 -foot tributary area), as well as on the drilled shafts from the bottom of the grade beam to the depth of the geologic contact of the dense to very dense sand or very stiff to hard silt and clay. We also included a 30,000 pound shear Toad applied in the horizontal direction, and a 30,000 pound downward axial load applied at the grade beam to model future structural loads that may be imposed on the foundation. The figure on page A-63 of Appendix A presents our assumed pile loading model. We recommend that drilled shafts have no Tess than a 24 -inch cross-sectional diameter and extend to a depth of at least 40 feet, and at least 10 feet into the very stiff to hard silt and clay or the dense sands. The design of drilled shafts was based on subsurface profiles as presented in Geologic Cross Sections B -B', E -E', and F -F'. The presence of approximately 10 feet of structural fill was included for the design of drilled shafts at F -F' based on the topography that is present. No structural fill was included for the design of shafts at B -B' and E -E'. Please note that the subsurface information at B -B' is based on subsurface information inferred from borings located more than 130 feet away and may not accurately represent the subsurface conditions in that area. The drilled shafts were designed assuming that the potentially liquefiable soils provide no frictional resistance. 24 -inch diameter drilled shafts may be designed for the following preliminary values assuming the above-mentioned loading conditions are present. Axial Shaft Capacity Location Downward (kips) Uplift (kips) Section B -B' 60 45 Section E -E' 60 40 Section F -F' 44 25 These values include a factor of safety of about 2.5. These capacity values may be increased by one- third when considering design Toads of short duration such as wind but not seismic forces, due to the significant seismic hazards that are present at the site. Figures presenting the allowable axial pile capacities versus pile length are presented on pages A-64 through A-66 of Appendix A. The allowable axial capacities presented above are based on the strength of the supporting soils for the penetrations Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 17 of 26 during drilling. The contractor should be prepared to install full length casing or use other means to minimize sloughing of the drilled shaft side walls during construction. Portions of the site had been used as an uncontrolled dump site and the contractor must be prepared to remove any deleterious debris that may obstruct drilled shaft installation. The base of the drilled shaft excavation should be free of loose and sloughed -in debris prior to placing concrete. Specialized, cleanout bucket equipment, which matches the drilled hole diameter, shall be used on each shaft. If more than 6 inches of water is present at the base of the drilled shaft excavation upon completion of drilling to the design depth, a tremie pipe should be used to place the concrete. The tip of the tremie pipe should be kept about five feet below the surface of concrete as the pour is being completed to ensure that water, drilling mud, and other deleterious material is displaced out of the excavation. Concrete placement for each drilled shaft should be completed in a single continuous pour to avoid the formation of a cold joint in the shaft. 11.4 BELOW -GRADE WALLS AND RETAINING WALLS Lateral earth pressures for design of below—grade walls, retaining walls, and foundation elements with level backfill and with no hydrostatic pressures or surcharge loads, may be calculated using the following equivalent fluid pressures: Active (unrestrained and drained conditions): Compacted granular soils Active (restrained and drained conditions): Compacted granular soils Passive: Continuous footings Column footings 36 psf/ft. 57 psf/ft. 250 psf/ft. 250 psf/ft. The geotechnical engineer should be contacted to determine appropriate lateral earth pressures for situations not described above. Seismic earth pressures were estimated using the Mononobe-Okabe pseudo -static method. We recommend that seismic earth pressures be estimated using a rectangular pressure distribution equal to 10H, where H is the height of the retained soil behind the wall. A total soil unit -weight of 125 pounds per cubic foot should be used in design of any permanent below - grade wall or retaining structures. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 18 of 26 11.5 SLABS -ON -GRADE If slabs -on -grade are to be provided on this project, we recommend that the slab -on -grade be supported on a minimum 6 -inch -thick, free -draining, gravel base as described in the Structural Fill section of this report. The 6 -inch thick free draining gravel base will serve as a capillary break and should contain less than 3 percent fines (material which can pass a No. 200 sieve). We also recommend that a robust under slab vapor barrier be provided under slabs -on -grade, where moisture -sensitive floor finishings are to be placed over the slab -on -grade, or in heated areas. The under slab vapor barriers should have a perm rating at least equal to the requirements of the proposed flooring system including their adhesive. A vapor retarder such as Stego Wrap produced by Stego Industries of San Clemente, California, Moistop produced by Fortifiber Building Systems Group of Reno, Nevada, or other approved material should be considered for use on this project. The under slab vapor barriers must be installed with strict accordance with the manufacturer's recommendations to ensure satisfactory performance of the system. This typically involves taping all seams and penetrations, sealing perimeter edges, and the use of plastic reinforcing steel chairs. 11.6 EARTHWORK The recommendations presented in this report are predicated on fulfillment of the following earthwork recommendations. 11.6.1 Site Clearing: Any existing vegetation, organic soils, woody debris, uncontrolled fill, and any other deleterious materials including asphalt pavements and old foundation elements shall be removed from the future building areas prior to construction. After site clearing and stripping, the exposed surfaces should be graded to allow good surface drainage during construction. The near -surface soils at the site are moisture -sensitive and easily disturbed during periods of wet weather. A gravel or quarry spall work surface may be built to protect the underlying native soils and to reduce the amount of soil disturbance during periods of wet weather. 11.6.2 Structural Fill: In general, the native soils on site that consist of sand with silt (SP -SM) or silty sand (SM) should only be used as structural fill during drier periods, provided that the soil is moisture - conditioned to within three (3) percent of optimum moisture. All fill and backfill materials should be placed in relatively horizontal loose lifts, not exceeding 10 inches in thickness, and compacted to at least 95 percent of the maximum dry density (MDD) as determined by the modified Proctor test (ASTM D1557). If manually -operated equipment such as a jumping jack compactor is used, the thickness of each loose lift should be no greater than 6 inches. Light vibratory plate compactors are not suitable for the compaction of structural fill. Soils consisting of clay, silt, peat, or containing deleterious matter are generally not suitable for use as structural fill. Structural fill material should be approved by ORA prior to use. The following table summarizes our recommendations and compaction requirements in Otto Rosenau & Associates, Incorporated. Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 19 of 26 reference to the 2006 edition of Washington State Department of Transportation's (WSDOT) Standard Specifications for Road, Bridge, and Municipal Construction for various types of aggregates. Intended Use Specification. Compaction Requirements Structural fill for overexcavation backfill below foundation elements 2- to 4 -inch quarry spalls, or washed crushed rock with a typical particle size between 1.25 and 2 inches and less than 5 percent fines Quarry spalls or dean crushed rock must be placed in lifts no greater than 12 inches in thickness, with each lift thoroughly compacted with a vibratory roller, or hoepack mounted on an excavator. Structural fill below pavements or sidewalks Suitable native soil, Gravel Borrow (WSDOT 9-03.14(1), Select Borrow (WSDOT 9-03.14(2), Crushed Surfacing Base Course (WSDOT 9- 03.9(3) Fill placed at depths greater than 2 feet below finish subgrade elevation must be compacted to 90 percent of MDD. Fill placed at depths within 2 feet of finish subgrade elevation must be compacted to 95 percent of MDD. Free -draining wall drainage material behind below -grade walls and retaining walls Gravel Backfill for Walls (WSDOT 9- 03.12(2), Gravel Backfill for Drains (WSDOT 9-03.12(4) Fill placed within 5 feet of below - grade walls or retaining walls shall be compacted with manually -operated compaction equipment. Fill placed at depths greater than 2 feet below finish subgrade elevation compacted to 90 percent of MDD. Fill placed at depths within 2 feet of finish subgrade elevation must be compacted to 95 percent of MDD, if the area will be supporting pavements or roadway. Capillary break material below slabs Pea gravel with a maximum particle size of about 3/8" and Tess than 3 percent fines. Washed, crushed rock with a maximum particle size of about 5/8". Washed, crushed rock shall be mechanically compacted prior to placing concrete. Structural fill to be compacted to 95 percent of MDD should be moisture -conditioned to within three (3) percent of optimum moisture. Structural fill to be compacted to 90 percent of MDD should be moisture- Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 20 of 26 conditioned to within six (6) percent of optimum moisture content. Placement of frozen soils or placement of soils on frozen ground should not be attempted. 11.7 SITE SLOPES 11.7.1 Permanent Slopes: We recommend that permanent cut slopes for this project be inclined no steeper than 2H:1V (horizontal to vertical). However, along South 160th Street we recommend that the permanent fill slopes be inclined no steeper than 2.5H:1V. The slopes adjacent to the South 160th Street right-of-way may be temporarily cut at an inclination no steeper 1.5H:1V if no seepage is observed and then built up as a fill slope to a 2.5H:1V final inclination in accordance with the embankment construction methods described in this section. Permanent fill slopes may be inclined up to 2H:1V if built with select granular materials (sand and gravel) that contains less than 10 percent fines and essentially free of any deleterious debris. Any proposed embankment fill must be approved by the geotechnical engineer before placement. All embankment fill must be compacted to at least 95 percent of the maximum dry density. Fill placed at depths greater than 2 feet below final grade shall be placed in loose lifts no greater than 10 inches in thickness. Fill placed at depths within 2 feet of finished grade shall be placed in loose lifts no greater than 6 inches. All fill embankments built on hillsides shall be built by benching into the original ground surface. Each bench shall penetrate into the hillside by at least 5 feet and shall not be greater than 5 feet in height. The horizontal portion of each bench shall be slightly sloped to drain outwards. Achieving the required compaction at the face of embankment slopes is difficult. We recommend that the embankment fill be temporarily over -steepened during construction and then cut to the final slope inclination at the end of embankment fill placement operations to ensure that the fill at the outside face of the embankment is adequately compacted. Alternatively, a 4 -foot wide strip of geogrid such as Mirafi 2XT, Tensar UX1000, or an approved equivalent may be used to stabilize the slope face. The geogrids should be installed at the slope face at 2 foot intervals for the full height of the embankment. Geogrids should be installed in a taut condition using pins as required, and fill should be carefully spread over it to prevent the creation of wrinkles. Geogrids should be installed in accordance with the manufacturer's recommendations. If seepage is observed at the excavation face during construction, drainage shall be provided at the location of the seepage and shall extend at least 5 feet laterally to either side of the seepage. The drainage shall consist of a rock -filled chimney drain at least 12 inches in width built against the excavation face. The rock shall consist of "Gravel Backfill for Drains" (VVSDOT 9-03.12(4)). A geotextile fabric shall surround the drain rock and a 4 -inch minimum diameter PVC perforated collector pipe (SDR 35 or Schedule 40) will be placed at the base of the rock -filled chimney drain. A 4 -inch Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 21 of 28 minimum diameter PVC tightline pipe (SDR 35 or Schedule 40) will direct the collected water to an appropriate discharge point at the base of the slope in accordance with City of Tukwila requirements. The geotextile used for the chimney drain and perforated collector pipe shall consist of Mirafi 140N, Amoco 4545, or other approved equivalent. Alternatively, a drainage panel such as Mirafi G200N, or other approved equivalent may be placed at the location of the observed seepage at the excavation face and shall extend at least 5 feet laterally to either side of the seepage. The collected water at the base of the panel may be directed to a gravel - filled drain with a 4 -inch minimum diameter PVC perforated collector pipe (SDR 35 or Schedule 40) fully surrounded with a geotextile fabric, such as Mirafi 140N, Amoco 4545, or other approved equivalent. A 4 -inch minimum diameter PVC tightline pipe (SDR 35 or Schedule 40) will direct the collected water to an appropriate discharge point at the base of the slope in accordance with City of Tukwila requirements. Upon completion of embankment construction, the exposed soil surfaces shall be hydroseeded. An erosion control blanket such as Western Excelsior Excel SS -2 Regular, or other approved equivalent, should then be installed over the hydroseeded surface in accordance with the manufacturer's recommendations. 11.7.2 Temporary Slopes: We anticipate that temporary cut slopes will be used at portions of the site to complete roadway and utility trench excavations. We recommend that the inclination of the temporary cut slopes be no greater than 1.5H:1V in the upper loose, sandy soils. Flatter slope inclinations will be required if groundwater seepage is encountered in excavations. All temporary cut slopes and excavations must comply with the provisions of Washington Administrative Code (WAC) Chapter 296-155, Part N, "Excavation, Trenching and Shoring." The contractor performing the work has the primary responsibility for protection of workers and adjacent improvements. However, we recommend that the contractor submit a work plan and excavation support plan for our review prior to beginning work on the site. 11.7.3 Setbacks and Buffers: We do not anticipate the need for steep slope setbacks or buffers on this project. 11.8 SLOPE STABILITY ANALYSIS ORA performed a computer-based slope stability analysis using the GeoStudioTM 2007 (Version 7.03, Build 3678) software program. The Morgenstern Price method of slices was selected to estimate factors of safety and forces. We evaluated several conditions at Sections B -B', E -E', and F -F'. The pre -developed and developed condition were assumed to be the same at Sections B -B' and E -E' since we do not anticipate that significant regrading will occur and we anticipate that the new structures will Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 22 of 26 be supported on deep foundations that will not add significant new surface loads. We evaluated the pre -developed and developed conditions at Section F -F' since we anticipate that significant regrading will be required. No assumption was made for the drawing down of water across the site. Two loading conditions were modeled for each location. 1. Static Loading Conditions — No earthquake forces applied, existing site conditions. 2. Seismic Loading Conditions — An IBC level seismic event (peak ground acceleration = 36 % g, and a 2,475 recurrence interval), modeled as a horizontal coefficient, ah of 0.18 in the pseudo - static analysis. Liquefied soil conditions were assumed to be present in this case. The existing slope was modeled assuming the presence of multiple soil layers as observed at borings B-1 and B-3 for Sections E -E' and F -F'. Assumed subsurface conditions were modeled at Section B -B'. The following soil parameters were used and are based on direct shear test results completed for this project: Soil Unit Description Assumed Unit Weight, y, (pcf) Angle of Internal Friction, 4), (degrees) Cohesion (psf) Silt and Clay 120 26 300 Medium Dense to Dense Sand and Medium Stiff Silt 105 28 75 Loose to Medium Dense Sand and Medium Stiff Silt 105 28 50 Liquefiable Sand and Silt 105 0 100 Dense Sand and Gravel Fill 125 34 25 The above listed soil parameters are reduced from those obtained in the laboratory testing completed for this project. In addition, the soil strength parameters used in our revised slope stability model are Tess than those used in a recent USGS report titled "Shallow -Landslide Hazard Map of Seattle, Washington: U. S. Geological Survey Open -File Report 2006-1139" by Edwin Harp and John A. Michael of the U. S. Geological Survey in Golden, Colorado, and William T. Laprade of Shannon and Wilson, Inc. in Seattle, Washington that was published in 2006. The residual strength of the liquefied sand layer was estimated using the residual strength approach presented in "Geotechnical Earthquake Engineering" (Kramer, 1996). We estimated that the residual strength of the soil following liquefaction is approximately 400 psf using this method. The estimated strength of the liquefied sand layer using the normalized strength approach presented in "Geotechnical Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 23 of 26 Earthquake Engineering" (Kramer, 1996) is less than 100 psf. A residual strength of 100 psf was used to model the strength of liquefied soils at the site. A graphical presentation of the results of our slope stability analysis are presented on pages A-55 through A-62 of Appendix A. A summary of the results under the various loading conditions is presented in the following table: Section Site Condition Loading Condition Estimated Minimum Factor of Safety Recommended Minimum Factor of Safety B_B' Pre -developed / Developed Static 2.2 1.5 B -B' Pre -developed / Developed Seismic 0.36 g 0.5 1.1 E -E' Pre -developed / Developed Static 2.9 1.5 E -E' Pre -developed / Developed Seismic 0.36 g 0.8 1.1 F -F' Pre -developed Static 1.9 1.5 F -F' Pre -developed Seismic 0.36 g 0.2 1.1 F -F' Developed Static 2.1 1.5 F -F' Developed Seismic 0.36 g 0.2 1.1 A factor of safety of 1 indicates that the forces that cause instability are in equilibrium with the forces that are resisting instability. A factor of safety of less than 1 indicates that the forces that cause instability are greater than the forces resisting instability and that the slope will fail. Conversely, factors of safety greater than 1 indicates that the forces resisting instability are greater than those causing instability and that the slope is stable. Based on the results of the slope stability analyses, we anticipate that the site is stable under static loading conditions, but would be unstable under a IBC level seismic event (peak ground acceleration = 36% g and a 2,475 year recurrence interval) if liquefaction occurs. We propose to mitigate for this scenario by providing a robust deep foundation system for each structure. The primary failure method anticipated by the slope stability analysis are failures through the upper sand layer. The most vulnerable areas were in the vicinity of boring B-1 where near -surface, liquefiable soils are present. It can be expected that seismic events with larger peak ground accelerations and longer recurrence intervals, will result in a lower estimated factor of safety for slopes at the site. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 24 of 28 In order to reduce the risk of slope instability after construction, we recommend the following practices: • All roof drains, footing drains, and other drains should be gathered and tightlined to a discharge location approved by City of Tukwila. • No on-site infiltration of stormwater runoff should be used. • Any accumulations of yard waste and biodegradable construction waste (cut branches, lawn clippings, and lumber) that are present should be removed from the slope face and adjacent areas. • Yard waste should not be placed on any of the existing slopes. • Vegetative cover should be continuously maintained on overall steep slope areas to reduce erosion potential and to stabilize surficial soils. • Avoid allowing water to accumulate in low-lying depressed areas around the site, such as at the identified sag pond features, which may allow the rapid infiltration of water into areas disturbed by past slope instability. 11.9 EROSION AND SEDIMENTATION CONTROL The migration of sediments from the site must be installed and controlled in accordance with City of Tukwila requirements. We recommend that the following minimum erosion control measures be employed at the site: 1. Provide silt fencing around the construction area to delineate the construction limits. No construction or soil disturbance should take place outside of the construction limits. 2. Stockpiled soil at the site should be kept to a minimum. Any stockpiled soils should be covered with carefully secured plastic sheeting. 3. Catch basin socks should be installed in nearby catch basins located downhill of the work area that could be impacted by construction activities. 4. All sediment and soil should be removed from adjacent pavements at the end of each day of construction activities. 5. Periodic inspection of the adequacy and condition of the installed erosion control measures by a geotechnical engineer or an experienced representative assigned by the geotechnical engineer. Additional erosion control measures may be required as construction progresses. 11.10 DRAINAGE 11.10.1 Construction Dewatering: Groundwater seepage will likely be encountered during construction. However, we anticipate that dewatering could be satisfactorily completed by routing water through ditches to a low spot or sump in the excavation. Water collected in the excavation should be Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 25 of 26 removed as soon as possible and should be discharged to a location approved by the City of Tukwila and in accordance with City of Tukwila requirements. 11.10.2 Surface Drainage: Good surface drainage is an integral part of the performance of earth - supported structures such as foundations, retaining walls, and pavements. Therefore, construction grades and final site grades should be designed to prevent water from entering the foundations or gravel drains behind any retaining walls, or from ponding on or next to pavements. Where pavement does not immediately abut structures, the ground surface should be sloped with an outfall of at least three (3) percent for a minimum distance of five (5) feet from exterior footings. These slopes should be capped with relatively impervious soils to prevent infiltration of water into the foundation soils. Runoff water should be collected from all impervious surfaces on the project and should be routed away from steep slope area on the west side of the site to a discharge location approved by the City of Tukwila. We strongly recommend that no on-site infiltration of runoff water be performed to minimize the flow of additional groundwater and to help minimize the risk of future slope instability. 11.10.3 Subsurface Drainage: We recommend that subsurface drainage be provided around each structure. The foundation drains for the residential structures should be built in accordance with the Typical Foundation Detail shown on page A-67 of Appendix A. The foundation drains should be sloped to drain to a suitable discharge point. Roof downspout drains and footing drains must be kept separate. Below -slab drainage may need to be considered if high groundwater levels appear to be problematic. 11.11 CONSTRUCTION OBSERVATION AND TESTING The recommendations presented in this report rely on adequate observation and testing of construction materials and procedures by the geotechnical engineer or his qualified representative. At a minimum, the testing program should include: • Observation and review of site preparation, structural fill placement, drainage installation, drilled shaft installation, or piling installation to evaluate whether actual conditions are consistent with those encountered during exploration and used for design. 12. REPORT LIMITATIONS The recommendations presented in this report are for the exclusive use of Mr. Jawaid Amon and other members of the design team for the proposed La Tourelle residential development at South 160th Street and 53rd Avenue South in Tukwila, Washington (King County Parcels # 5379200005 and 5379200006). The recommendations are based on the readily -available geologic literature and eight borings completed in June 2006 and April 2007, and a hand auger exploration completed on February 19, 2008. The recommendations of this report are not transferable to any other site. If there are any revisions to the plans or if deviations from the subsurface conditions noted in this report are Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Short Plat ORA Project No.: 06-373 March 11, 2008 Page 26 of 26 encountered during construction, Otto Rosenau & Associates, Inc. (ORA) should be notified immediately to determine whether changes to the design recommendations are required. oOo APPENDIX A f BMW IIVAIMENfAl SR-518„),=tea 6 24 53rd Ave S and S 160th St Iojse1a. ��UMWprzav Note: The location of all features shown is approximate. Reference: Des Moines, Washington USGS Quadrangle and portions of adjacent quadrangles, ALL TOPO MAPS: Washington. VICINITY MAP Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 1, 2008 For: Mr. Jawaid Amon OTTO ROSENAU & ASSOCIATES, INC. ORA Project Number: 06-373 A-1 Note: The location of all features shown is approximate. Reference: Puget Sound LiDAR Consortium, Seattle, WA LIDAR IMAGE VICINITY MAP Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 20, 2008 OTTO ROSENAU & . ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-2 0 60 -... \. N `- _ .__ l- 280 N'-,`-, �-��� _ �` n \ 2`90 ` \ `�---- `� ``• \ \ \ \\ c'WETLAND 11 ��N. -••••••amm..... --_,./../:: \ 300 %I ` \�9`�` �` N\ ` �, o V o `.� �� �\ so B-5 `\ B-4 \26 ��-- �, �� yam' ' ` Qk \�2 \ I - �t i ‘ 1 {WETLAND 21- \I 1 / 28 ` \ \1---='<--' .'. 0 \ I / Curb line S. 159TH ST. `Property line 70 140 190 MN '0 a B-2 B-1 B-6 tt N N-'0 .T 0 N i c 'o . \-• TDi10 0 N. t tWETLAND 3I t ao j o \`\` y Np G N� \ / o o Horizontal and Vertical Scale in Feet LEGEND O B-1 through B-5 Borings completed by ORA in June 2006 • B-6 through B-8 Borings completed by ORA in April 2007 • HH -1 Hand -Auger Exploration completed by ORA in February 2008 B B' l Location of Geologic Cross Section HH -1 tt 0 Curb line Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. O- 761076, s 1 SITE PLAN Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: February 20, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-3 o 0 c9 0i 1- z z 5 a 0) vi c) z 0 m m w a 0 a 5 1- 1- -J J 1a x OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-1 6747 M.L. King Way South PAGE 1 OF 3 Seattle, WA 98118 Telephone: (206) 725-4600 - Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/20/06 COMPLETED 6/20/06 GROUND ELEVATION 256 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING --- LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop 71 yearhrs AFTER DRILLING 3.0 ft / Elev 253.0 ft o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS U.S.C.S. GRAPHIC LOG MATERIAL DESCRIPTION WELL DIAGRAM - - - -XSS MC=15/° MC=19%GSes=26% MC=13% MC=18% MC=22% MC=32% MC=27% MC=32% LL=45 PL=26 Fines=93% , GS, HYD, AL SP- SM ;'• • :* ' ,, : > .: , Medium dense, fine to medium, gray -brown I SAND with SILT with some oxidation . ' . • • ` . — --'—' , :-� , . • '.'..e •. Bentonite seal with solid pipe Sand filter pack with solid pipe Sand filter with slotted pipe -1Bottom cap 1 33 5-6-6° (12) 5 SM SM SM SM SM �•.: .......• :'• •`•': :• . ,`:;. ..:. -:•' `:. • • '`:: .; •:. : .•.;: ' •`:•' :'• • ``'. Very loose, gray Silty SAND with Gravel Medium dense, gray Silty SAND with gravel in tip of sampler• Loose, gray Silty SAND with gravel in tip of sampler Medium dense, brown, Silty SAND with a 1 inch layer of oxidized sand at approximately 16 feet Loose, brown, interbedded SiltySAND and 20.8 235.3 _ -X - ZS 33 4(4)2 X 3S 33 �13� 10 - 15 / X /• 4S 44 4-4-5 ) - -X - - - - 20 5S 44 4-8-13 ( ) - -X 25 SS 6 56 2-3-5 (8) \medium stiff SILT, lowest 2 inches gray SILy-- ML ML Very stiff, dark gray SILT Very stiff, dark gray SILT - 30 S X 7S 56 8 (26) 5 _ 35 SS X7 100 �30� 8 A-4 (Continued Next Page) 00 0 M H 0 q ui D co1- z 0) z 0 uJ w a 0 a 5 J O. CO LLI OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-1 6747 M.L. King Way South PAGE 2 OF 3 Seattle, WA 98118 Telephone: (206) 725-4600 __ - Fax: - Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington c,, DEPTH cn (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS U.S.C.S. GRAPHIC LOG MATERIAL DESCRIPTION WELL DIAGRAM - ST 100 MC=27% DSD=93pcf , MC=25% MC=27% MC=28% MC=28% MC=34% DD=87pcf , DS MC=30% MC=32% Fines=99% , GS MC=33% MC=28% ML ML ML ML ML ML ML ML ML ML Very stiff, dark gray SILT Hard, dark gray SILT Hard, gray SILT Very stiff, gray SILT Very stiff, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT with 1 -inch thick seam of fine SAND at 71 feet _ - 40 SOS 100 8- 15-134)9 34) 9 - -� 45 SS 11 100 9-167-21 _ 50 \/ S2 100 7 �25� 4 _ _ 55 \ / X S3 100 7 �24� 4 - _ 60 14 1100 S5 100 9-17-35) 8 -16 65 SS 100 12-17-21 (38) _ 70 \ / S� 100 10(51)28 _ _ 75 \/ ` 8 100 12(66)35 1 A-5 (Continued Next Page) 0 M H 0 s. U) 1- 1- z 0. a vi 0 z it 0 a 0 a 5 1- -J J m OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-1 6747 M.L. King Way South PAGE 3 OF 3 Seattle, WA 98118 Telephone: (206) 725-4600 -'- - "- ' - - Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington a. wai o - 75 w EL Efj a QZ U) o O 0 ce m p > oz TESTS ui ci GRAPHIC LOG MATERIAL DESCRIPTION WELL DIAGRAM _ \/ X 9 100 16(56)31 MC=30% ML ML ML ML ML ML Hard, gray SILT with medium SAND in tip No recovery Hard, gray SILT with distinct 1/4 -inch lamination dark gray to black SILT at 86.25 feet. Inclined bedding orientation. Massive silt present above and below sand lamination. Hard, gray SILT Hard, gray SILT Hard, dark gray SILT 5 154.5 101.5 80 SS 0 . 50/6" - 20 _ 85 - _ \/ X / 2S 100 16(64)38 MC=26% - 90 _ _ \ / X 22 100 15(703 MC=26% 95 - _ X 23 100 20(69)39 MC=27% 100 ` SS 101 23-50/6" MC=30% \ ' Bottom of hole at 101.5 feet. A-6 0 0) O q vi z z Q. 0 z it 0 uJ w 0 rea 5 H J 3 a 1- x m OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-2 6747 M.L. King Way South PAGE 1 OF 3 Seattle, WA 98118 Telephone: (206) 725-4600 _. — ___ _.__.._ Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/21/06 COMPLETED 6/21/06 GROUND ELEVATION 205 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING --- LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop 2 1 yearhrs AFTER DRILLING 17.5 ft / Elev 187.5 ft o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) i I TESTS U.S.C.S. GRAPHIC LOG MATERIAL DESCRIPTION WELL DIAGRAM 5 GS MC=21% Fines=44% MC=12% MC=20% SD=86pcf , MC=16% Fines=20% GS MC=27%DD SD=93pcf , MC=29% MC=30% MC=29% SM SM •. • ; `..: • .: .'. •• " ` " Gravelly drilling from 1.5 feet to 5 feet Loose, light brown Silty fine SAND 11.0 194.0 Medium dense, light brown Silty fine SAND :: .. : ••'— • • "'; "_ • ,-•' : •• •_ • ' :•••• • • • . •• • ....4 Bentonite seal with solid pipe Sand filter pack with solid Sand filter pack with slotted pipe Bottom cap 10 " SS1 44 2-3-4(7) "SS . 2 100 5'7-10 (17) �., Medium dense, light brown Silty fine SAND with Silt Medium dense, light brown fine SAND with Silt occasional thin oxidized layers 187.0'• ;:' .• • '.•::• .. :18.0 SP- SM SM S3T 100 15 '''' il 100 4-11-13 (24) SM :•:: .; '. •••`:•' Loose to medium dense, Silty fine SAND 23.0 Loose to medium dense, Silty fine SAND 182.0 25 6T 100 ri S6S 67 3106 ( ) , Stiff, gray Sandy SILT Very stiff, gray SILT Very stiff, gray SILT ML ML ML 30 " 6S 56 5-7-8 (15) 35 " 6S 100 (7) A-7 (Continued Next Page) 0 0 1- z z 0 0 0 c� ai z 0 0 LU Lu a 0 5 3 Y 1- F - J 3 a 1- x 0 0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-2 6747 M.L. King Way South PAGE 2 OF 3 Seattle, WA 98118 Telephone: (206) 725-4600 —. - Fax: (206)723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington __ o 35 w �w Qui a Z O (-) O ��D m p> 0 TESTS vi GRAPHIC LOG MATERIAL DESCRIPTION WELL DIAGRAM ST 9 100 MC=27%DIS =97pcf , ML ML ML ML ML ML ML Very stiff, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT with distinct 1/4 -inch lamination black SILT at 71 feet. Inclined bedding orientation. 40 - -X 10 SS45 67 5- (24) 2 MC=25% - X11 SS 100 7 i30) 7 MC=30% 50 _ -X SS 78 10(8)23 MC=29% LL=33 PL=26 Fines=96% , GS, HYD, AL 55 - -X 13 100 9 (38) 2 MC=30% 60 \ / X / ` S4 4 100 15-25-235 ( ) MC=29% 65 - -/ \ 15S 100 16(52)26 MC=31 % 70 _ _X 16 100 15(83)52 MC=24% - - 75 A-8 (Continued Next Page) GENERAL BH / TP / WELL TUKWILA PROPERTY BORINGS.GPJ GINT US.GDT 3/7/08 A-9 OTTO ROSENAU & ASSOCIATES, INC. M.L. King Way South WA 98118 (206) 725-4600 (206) 723-2221 BORING NUMBER B-2 PAGE 3 OF 3 PROJECT NAME La Tourelle Short Plat 6747 Seattle, Telephone: _ CLIENT PROJECT — - Fax: Mr. Jawaid Amon NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington _ o - 75 cn w w w g az > 0 cc V2S OJ m > mooz TESTS GRAPHIC LOG MATERIAL DESCRIPTIONBO WELL DIAGRAM _ 80 \ / X S� 100 17-4 9j 7 MC=24% MC=22% ML ML 81.5 Hard, gray SILT Hard, gray SILT 123.5 - _X SS 18 100 22 34 40 (74) Bottom of hole at 81.5 feet. A-9 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-3 6747 M.L. King Way South PAGE 1 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 — - Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/22/06 COMPLETED 6/22/06 GROUND ELEVATION 228 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING — LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop T Esthrs AFTER DRILLING 24.0 ft / Elev 204.0 ft o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS U.S.C.S. 1 GRAPHIC LOG MATERIAL DESCRIPTION -X MC=16% MC=33% MC=14% MC=15% MC=21%GSes=15% MC=14% MC=20% SP -SM SP- SM .::•::•�•: ::. :j •` •' • .: `,� Medium dense, brown, fine to medium SAND with SILT, some oxidation evident Medium dense, light brown, fine to medium SAND with Silt 6.5 221.5 SS 1 100 3-4-81 ( ) 5 -XS -VI 2 89 6-9-9 (18) SW • •. o.,.ti Medium dense, light brown, well -graded Silty SAND 9.5 218.5 I S3S ��/ VVV 33 8� 10 SP- SM P- SP SM SP- SM SP -•Medium SM :' ::.:.� :.`.�• .'• :: :..;.:� •:• : •• • >.:: `: • • `. ; �' No recovery with trace fine sand in sampler Medium dense, light brown, fine to medium, SAND with Silt and gravel Medium dense, light brown, fine to medium SAND with Silt and gravel Dense, light brown, fine to medium SAND with Silt and occasional gravel with some oxidation evident 51 dense, light brown, fine to medium SAND with Silt and occasional gravel with some oxidation evident 29.0 199.0 _V - 15 SS 4 0 10-13-17 (30) \ J12 X 5S � 22 -9-8:r _)( 20 \/ /\ 6 33 2) -X _ 25•'` 7S 100 8 233) 2 -X - 30 SS 8 44 7-6-18 (24 SM • •• `? ::':".•..• : No recovery _ 35 \/) x 9S 0 32 17-15-17 A-10 (Continued Next Page) 0 0 vi 1- Z_ m z 0 m m w a 0 a 5 F LjJ a x CO 111 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-3 6747 M.L. King Way South PAGE 2 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington C) DEPTH cn (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui ai GRAPHIC LOG MATERIAL DESCRIPTION - _ - - 40 X / \ S� 100 11(200)10 MC=28% MC=26 /° MC=22% LL=39 PL=22 Fines=88% , GS, HYD, AL MC=31% MC=29% MC=30% SM SM ::.:;; :..: • :::.:�.•: Medium dense, light brown, fine to medium, Silty fine to medium SAND with interbedded Sandy SILT Dense, light brown, Silty fine SAND 44.0 184.0 - -X _ _////' 45 SS 11 56 14-14-23 ( ) CL CL CL CL CL j % No recovery with trace day in sampler Hard, gray lean CLAY Hard, gray lean CLAY Hard, gray lean CLAY Hard, gray y lean CLAY 66.5 161.5 - 50 224 S2 0 39 21 - - 55 SS 13 X 56 15-21-23 (44) - _ 60 X S 100 14 13(47)23 _ _ 65 S5 15(53)25 X 100 -X SS 16 100 14-26-58 (84) Bottom of hole at 66.5 feet. A-11 o 0 1) 0 1- z z 0 0 0 0 z 0 o m 3 0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-4 6747 M.L. King Way South PAGE 1 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/19/06 COMPLETED 6/19/06 GROUND ELEVATION 228 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger Q AT TIME OF DRILLING 11.0 ft / Elev 217.0 ft LOGGED BY Anthony Coyne P.E. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING -- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop AFTER DRILLING --- DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS u) vli GRAPHIC LOG MATERIAL DESCRIPTION 5 MC=15% MC=13% Fines=26% GS MC=16% ° MC=15 /° MC=30% MC=24% MC=26% SM'• SM SM• SM SM •'• ' •:� ".; ..• : ,.;,•,• ;.:.� ;.. • .' `' >•: `' Medium dense, gray, Silty fine to medium SAND with occasional debris and organics (charcoal and root hairs) (fill) Loose, fine to medium, gray Silty SAND (fill) Medium dense, gray Silty SAND with occasional fine gravel (fill), oxidation present. Medium dense, gray, Silty Sand with occasional fine gravel (fill), oxidation 11 0 217.0 " SS 89 (11) 10 " 100 4-4-4 (8) 1'ssS 100 311) _-:'.�•': GENERAL BH / TP / WELL TUKWILA PROPERTY BORINGS.GPJ GINT US.GDT 3/7/08 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-4 6747 M.L. King Way South PAGE 2 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 .. "- —. - Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington co DEPTH v' (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui ui GRAPHIC LOG MATERIAL DESCRIPTION 40 XSS 9 33 2-1 (19) MC26% Fines49% GS MC=23% MC=33% MC=29% SM SM SM • ```•' ••:: • `'�::.46.3 Medium dense, light brown, Silty fine SAND Loose, bluish -gray, Silty fine SAND Medium dense, bluish -gray, Silty SAND 181,8 _X 45 SOS 33 8(3)3 _X 50 SS 67 1 �) ML ML Stiff, bluish -gray, Sandy SILT Very stiff, bluish -gray, Sandy SILT 51.5 176.5 SS 12 100 5-7-10 (17) Bottom of hole at 51.5 feet. A-13 0 (9 ai 1- z z a ai z m w cc a 5 11 m Lu OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-5 6747 M.L. King Way South PAGE 1 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 --- - Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/19/06 COMPLETED 6/19/06 GROUND ELEVATION 243 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING --- LOGGED BY Anthony Covne P.E. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop SI 24hrs AFTER DRILLING 3.0 ft / Elev 240.0 ft o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS u) 6. GRAPHIC LOG MATERIAL DESCRIPTION MC=13% MC=10% Fines=7% , GS MC=27% MC=26%GFS es=8% , MC=30% MC=32% Fines=23% , GS MC=25% MC=33% SM: • : • :.1 5 Loose, dark brown, Silty fine SAND (topsoil) 241.5 SP- SPP SP- ML : • . • .. .. Lose, light brown, fine to medium SAND with Silt and occasional organics Loose, light brown, fine SAND with Silt Loose, light brown, fine SAND with Silt and occasional interbedded Silt Medium dense, light brown, fine SAND with Silt 13.0 230.0 Vss 100 4-4-5 5 1 SS 2 100 4-4-4 (8) _- :' 3S 100 (13) 10 15 _- 4S 100 4 126 ML SM SM 1111 • •'• Stiff, light brown, Sandy SILT with thin, interbedded fine, dean SAND seams, oxidation present 18.0 225.0 20 ri5S 100 415) Medium dense, light brown, Silty fine SAND Dense, light brown, Silty fine SAND 28.5 214.5 25 " S S6 89 3-5-6 (11) 30 3S 100 9 i32) 6 SM • • .31.0 Medium dense, gray, fine SAND with SILT 212.0 35 "SP 8 100 9)8 (18 Very stiff, gray, Sandy SILT 33.3 209.8 ML :. 1 A-14 (Continued Next Page) GENERAL BH / TP / WELL TUKWILA PROPERTY BORINGS.GPJ GINT US.GDT 3/7/08 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-5 6747 M.L. King Way South PAGE 2 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 -•- _...._ -- - Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington iI-w w 35 wwo a? QZ ti) 0 W CC FF-� m O> 0 TESTS u.S.c.s. 1 U z � O 0 MATERIAL DESCRIPTION _X SS 9 100 9-11-12 (23) MC=31 % SP- � SM i .-:;•j L .35.8 Medium dense, gray,fine SAND with SILT 207.3 Very stiff, gray SILT Very stiff, gray SILT Very stiff, gray SILT 51.5 Stiff, gray SILT 191.5 ML ML ML ML 40 _ -X SOS 100 X16) MC=30% LL=33 PL=26 Fines=98% , GS, HYD, AL _ 45 _X 11 SS 100 -15 7 X29) 5 MC=29% 50 _ _ \ / X // �\ 32 100 (14) MC=30% Bottom of hole at 51.5 feet. A-15 o 0 0 0 D z 0 0 m 0 w 0 w w O 3 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-6 6747 M.L. King Way South PAGE 1 OF 1 Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-0373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA DATE STARTED 4/6/07 COMPLETED 4/6/07 GROUND ELEVATION 232 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Davies Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger Q AT TIME OF DRILLING 31.0 ft / Elev 201.0 ft LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING — NOTES 140 # safety hammer, SPT sampler, rope and cathead, 30 -inch drop AFTER DRILLING --- DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS U.S.C.S. GRAPHIC LOG MATERIAL DESCRIPTION - 10 SS 100 3 2 MC=14% MC=12% MC=10% MC=7% MC=7% MC=27% MC=28% MC=30% MC=27% MC=30% SP- SP- SM SP SM ':: •'•::.`, :•• • : • • .. •,:12.0 Loose, light brown, fine SAND with silt (moist) Loose, light brown, fine SAND with silt (moist) Loose, light brown, fine SAND with silt (moist) 220.0 SS 2 100 4-4-4 8 _ _ _\>U41/Li 20 SS 3 100 3-3-3 6 / SP SP SP•:' • ': . �. ` , Medium dense, light brown, fine SAND (moist) Medium dense, light brown, fine SAND (moist) Medium dense, light brown, fine SAND (moist) 28.0 204.0 00 )4-164-8 _6 - - 30 5S 100 6 20 1 100 8121716 SM '.: :; -;. . : : 2 Medium dense, light brown, Silty fine SAND (moist to wet) 33.0 199.0 _ 40 3S 100 8-120010 SP SM ::' • '•: • : .• • Medium dense, light brown, fine SAND with silt (wet) 38.0 194.0 SS 100 7-11-14 25 ML ML ML Very stiff, gray, sandy SILT with interbedded silty sand (wet) Hard, gray SILT (wet) 51.5 Hard, gray SILT (wet) 180.5 _ 50 V SS 9 /—\ 100 9-10-16 (26) SS 10 100 12-19-26 45 ;; •_/±10-3143-19 Bottom of hole at 51.5 feet. A-16 CO 1- ui D 1- z 0 0 w 0 0 w J w 0 0 5 3 x m OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-7 6747 M.L. King Way South PAGE 1 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 Fax(206)723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-0373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA DATE STARTED 4/6/07 COMPLETED 4/6/07 GROUND ELEVATION 226 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Davies Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger Q AT TIME OF DRILLING 15.0 ft / Elev 211.0 ft LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 # safety hammer, SPT sampler, rope and cathead, 30 -inch drop AFTER DRILLING --- o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui 6 . v U_ ° O 0 MATERIAL DESCRIPTION - - _ 5 SS 1 33 1-1 MC=26% MC=16% MC=15% MC=17% MC=16% MC=14% MC=12% MC=14% o MC=12 /o MC=24% MC=25% SM . :,. ; , ; `: Very loose, brown, Silty SAND with organics (moist, bark) 1.5 224.5 SP- SM . .. • : ,! • Very loose, brown, fine to medium SAND with silt and debris fragments (moist, brick) 223.0 SS 2 100 1-1-1 (2) SM :: ' ' ` • :' �' �', Loose, brown, Silty SAND with organics and occasional gravel (moist, roots and charcoal) 4.8 221.3 SS 3 100 1-2-3 4 (5) ML ML ML Very stiff, gray, sandy SILT (moist, heavily oxidized, root hairs and charcoal) gray, sandy SILT with organics and occasional gravel (wet) Stiff, gray, sandy SILT with organics and occasional gravel (moist) 9.8 216.3 _' - - 10 S 4S 100 620)1 5S 100 Stiff, X10) 6 100 X13) SM SM SM :. .. ..'• ':.`>.; . :. '• ,. .14.5 Medium dense, gray silty SAND with occasional gravel (moist) Dense, gray silty SAND (moist) Medium dense, gray silty SAND with occasional gravel (moist) 211.5 _ - _ - 15 fSS 7 100 2-5-6-10 (11) 8 100 6 (3'I; 8 SS 9 100 12-7-10 (17)•:: SM Sp_ SM SP- SM •:. ••:: .:: '::.\ ':• .` •. •' • ' ,. . : ' ��• • • a Medium dense, gray, fine to medium SAND with occasional gravel (wet) Medium dense, gray, fine to medium SAND (wet) Medium dense, light brown, fine to medium SAND (wet) - - - - - - 20 SS 10 100 15-10-11-8 (21) SS 11 100 4-6-8 (14) SS 12 100 8-11-15 (26) A-17 (Continued Next Page) o 1- zql CD oi z 5 Ef m w w 0 a w w D: 0 O 5 J w OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-7 6747 M.L. King Way South PAGE 2 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-0373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA _ _w w o 20 w a QZ u) O w 0: ~� j m00z TESTS v? GRAPHIC LOG MATERIAL DESCRIPTION XSS 13 100 8-17-19 (36) MC 27% SP- SM SP- SM SP- SM •: :•:-` :•: :. •' ',`%' ::•`.` .:: .....• ;' • • .• . • :: `• �' Dense, light brown, fine to medium SAND with silt (wet) Dense, light brown, fine to medium SAND with silt (wet) Very dense, light brown, fine to medium SAND with silt (wet) 35.5 190.5 25 - - SS 14 100 8-16-16 (32) MC=27% 30 - -/ SS 15 100 37-37-28 (65) MC=27% - - 35 - I. SS 16 100 5-11-17 (28) MC=24% ML 36.5 Verystiff, gray SILT (wet) 189.5 Bottom of hole at 36.5 feet. A-18 co 0 e 0 N 3 a m m 0 1- 0 a w J Lu rt 0 3 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-8 6747 M.L. King Way South PAGE 1 OF 1 Seattle, WA 98118 Telephone: (206) 725-4600 _-_ __ .- Fax: (206) 723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-0373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA DATE STARTED 4/6/07 COMPLETED 4/6/07 GROUND ELEVATION 224 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Davies Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger Q AT TIME OF DRILLING 7.0 ft / Elev 217.0 ft LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 # safety hammer, SPT sampler, rope and cathead, 30 -inch drop AFTER DRILLING --- o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ai j GRAPHIC LOG MATERIAL DESCRIPTION _ _ r - 10 SS 1 22 9 1-32 1 MC=18% MC=9% MC=26% MC=133% MC=446% ° MC=70% MC=23% MC=19% MC=18% MC=16% MC=18% MC=21% MC=20% MC=19% MC=26% SM :. Medium dense, brown silty SAND and gravel and occasional debris (asphalt fragments, and roots) (moist) 6.0 218.0 11-8-5 (13) i VSS 2 22 r- SS 3 2-3-3 6 100 SP SM :, : 8 0 Q Loose, brown fine to medium SAND with silt and organics (moist becomes 216.0 2-2-2 X (4) i X SS ' '1 100 wet at 7.0 feet) /_- ....; ��i�� ♦x_11.5 Wood:;* Loose, dark brown, decayed, wood fragments with sand (wet) 212.5 SS 5 1-2-1 3 J _ 20 100 OL — _ = Soft, black Organic SILT with wood fragments (wet) 14.0 210.0 1 6S -.4___42..\___u_ SM :: .. Medium dense, light brown, Silty SAND with organics and occasional gravel 206.0 SS 7 100 4-7-9 16 J: ML Stiff, gray, sandy SILT with interbedded sand (wet) 23.0 201.0 _ 1 30 SS 8 100 4-5-8 1j_4� SM :: •;•... . :. Medium dense, light brown, fine Silty SAND with occasional gravel (wet) 28.0 196.0 SS 9 100 -10 6 9 19 SP SP SP Sp :: ' • ;: .48.0 Medium dense, light brown, fine Silty SAND with occasional gravel (wet) Very dense, light brown, fine SAND (wet) Very dense, light brown, fine SAND (wet) Medium dense, light brown, fine SAND (wet) 176.0 _ _SS 40 SS 10 100 5-9-16 25 11 100 6-21-38 9 _ _ - 50 4.1/Li SS 2 100 5-22-33 55 SS 13 100 188-8-10 SP- k SM / •'`• :: ''.. '. 51.0 Very dense, light brown, fine SAND with silt (wet) 173.0 _ - SS ., 14 / 101 33 32 50/6" 56.5 Hard, gray SILT (wet) 167.5 ML ` SS15 100 /—\ 10-18-2222 ( Bottom of hole at 56.5 feet. A-19 GENERAL 13H 1 TP / WELL LA TOURELLE HAND AUGER.GPJ GINT US.GDT 3/7/08 OTTO ROSENAU & ASSOCIATES, INC. HAND AUGER 6747 M.L. King Way South NUMBER HH -1 PAGE 1 OF 1 Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME La Tourelle Short Plat PROJECT NUMBER 06-0373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 2/19/08 COMPLETED 2/19/08 GROUND ELEVATION 275 ft HOLE SIZE 3 -inches DRILLING CONTRACTOR ORA GROUND WATER LEVELS: DRILLING METHOD Hand Auger Q AT TIME OF DRILLING 6.0 ft / Elev 269.0 ft LOGGED BY Anthony Coyne P.E. CHECKED BY Anthony Covne P.E. T. AT END OF DRILLING 6.0 ft / Elev 269.0 ft NOTES AFTER DRILLING --- o DEPTH (ft) SAMPLE TYPE NUMBER ui U ui GRAPHIC LOG MATERIAL DESCRIPTION _ - - - _ 5 SM. `•:'. 1.0 fine to medium Silty SAND with organics (loose, moist)(roots) 274.0 ,Brown, Light brown fine SAND with Silt (medium dense to dense, moist) 271.0 SP- SM "; ;; "• :. SM ..�': : .;•:. Orange -brown heavily oxidized layer at 6.5 to 7 feet Light brown, fine to medium Silty SAND with organics (medium dense to dense, moist to wet) 265.5 - - - - 10 ML 1 11 Light brown to gray SILT (stiff, wet) 11n n I~— Bottom of hole at 10.0 feet. A-20 BORING LOG NOTES These notes and boring Togs are intended for use with this geotechnical report for the purposes and project described therein. The boring logs depict ORA's interpretation of subsurface conditions at the location of the boring on the date noted. Subsurface conditions may vary, and groundwater levels may change because of seasonal or numerous other factors. Accordingly, the boring logs should not be made a part of construction plans or be used to define construction conditions. The approximate locations of the borings are shown on the Site Plan. The borings were located in the field by measuring from existing site features. "Boring Size" refers the diameter and type of auger used. "HSA" denotes hollow -stem auger. "SSA" denotes solid -stem auger. "BA" denotes bucket auger. "Sample Number and Type" refers to the sampling method and equipment used during exploration where: • "SS" indicates split -spoon sampler with 1-3/8" inside diameter and 2" outside diameter. • "ST" indicates sample attempted using a Shelby thin-wall sampling tube with 3" O.D. "N -Values" refer to the Standard Penetration Test which records number of blows from a 140 -pound hammer falling 30 inches required to advance a standard sampler eighteen inches. The blow counts required to drive the sampler through each 6 -inch interval is recorded. The number of blows to drive the sampler for the last 12 inches of driving are added together and is considered to be the N -Value. The N -Value is presented in parentheses on the boring logs. The actual blow count values for each 6 -inch interval is also presented. If the sample is driven less than 6 inches for a given interval, the actual distance driven is recorded. "Moisture Content (MC)" refers to the moisture content of the soil expressed in percent by weight of dry sample as determined in the laboratory. "Grain Size (GS)" refers to a grain size distribution analysis completed in general accordance with the ASTM D422 test procedure. "Hydrometer (HYD)" refers to a grain size distribution analysis completed in general accordance with the ASTM D422 test procedure. "Fines" is an estimate of the portion of a soil sample passing a No. 200 sieve as determined using the ASTM D422 test procedure. A-21 "Atterberg Limits (AL)" refers to a determination of the liquid and plastic limits of a cohesive soil using the ASTM D 4318 test procedure. "Dry Density (DD)" refers to an estimate of the dry density of a soil sample collected using a Shelby thin-wall sampling tube. "Direct Shear (DS)" refers to an estimate of the shear strength of a soil as determined using direct shear test equipment and performed in general accordance with ASTM D 3080. "Description and USCS Classification" refer to the materials encountered in the boring. The descriptions and classifications are generally based on visual examination in the field and laboratory. Where noted, laboratory tests were performed to determine the soil classification. The terms and symbols used in the boring logs are in general accordance with the Unified Soil Classification System. Laboratory tests are performed in general accordance with applicable procedures described by the American Society for Testing and Materials. "V" Indicates location of groundwater at the time noted. TERMS for RELATIVE DENSITY of NON -COHESIVE SOIL Term Standard Penetration Resistance "N" Very Loose 4 or less Loose 5 to 10 Medium Dense 11 to 30 Dense 31 to 50 Very Dense Over 50 blows/foot TERMS for RELATIVE CONSISTENCY of COHESIVE SOIL Term Unconfined Compressive Strength Very Soft 0 to 0.25 tons/square-foot (tsf) Soft 0.25 to 0.50 tsf Medium Stiff 0.50 to 1.00 tsf Stiff 1.00 to 2.00 tsf Very Stiff 2.00 to 4.00 tsf Hard Over 4.00 tsf A-22 DEFINITION of MATERIAL by DIAMETER of PARTICLE Boulder 8 -inches+ Cobble 3 to 8 inches Gravel 3 inches to 5mm Coarse Sand 5mm to 0.6mm Medium Sand 0.6mm to 0.2mm Fine Sand 0.2mm to 0.074mm Silt 0.074mm to 0.005mm Clay less than 0.005mm SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL DESCRIPTIONS GRAPH LETTER COARSE GRAINED SOILS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE CLEAN GRAVELS (LITTLE OR NO FINES) '' ' 4. is O•• b/ is AGI ••�S, GW WELL -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES o Qo o° )o D�o )00000 Qo D", t GP POORLY -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES GRAVELS WITH FINES (MORE THAN 12% FINES) ,'l i • j o b DO 1R o 46 . 046 V 1 C D Q ' GM SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES ���! d,.I� i' e.e '4'I� �,� �! 74 GC CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES SAND AND...•.• SANDY SOILSPOORLY-GRADED MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE CLEAN SANDS (LITTLE OR NO FINES) SW WELL -GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES •. . :: • SP SANDS, GRAVELLY SAND, LITTLE OR NO FINES SANDS WITH FINES (MORE THAN 12% FINES) •SM SILTY SANDS, SAND - SILT MIXTURES `SC' CLAYEY SANDS, SAND - CLAY MIXTURES FINELIQUID GRAINED SOILS MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE SILTS LIMIT AND LESS THAN 50 CLAYS ML INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY / CL INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ---- _ _ _ _ OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS SILTS LIQUID LIMIT CLAYS GREATER THAN 50/)1AND CH INORGANIC CLAYS OF HIGH PLASTICITY M OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS \` i, 0 ', , ', \' ', '�",", �`!, PT PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS NOTE: FINES ARE MATERIALS PASSING THE NO. 200 SIEVE. COARSE GRAINED SOILS RECEIVE DUAL SYMBOLS IF THEY CONTAIN BETWEEN 5% AND 12% FINES. FINE GRAINED SOILS RECEIVE DUAL SYMBOLS IF THEIR LIMITS PLOT LEFT OF THE "A" LINE WITH A PLASTICITY INDEX (PI) OF 4% TO 7%. A-24 ELEVATION (feet) A 250 240 230 220 210 200 190 180 170 160 150 140 130 120 Approximate existing ground surface Loose to medium dense sands A' C Approximate piezometric surface Stiff to hard silt and lean clay Section A -A' 0 40 80 Horizontal and Vertical Scale in Feet Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. 250 240 230 220 210 200 190 180 170 160 150 140 130 120 ELEVATION (feet) 250 240 230 220 210 200 190 180 170 160 150 140 130 120 Approximate piezometric surface Loose to medium dense sands CO 0) u) O N Approximate existing ground surface C' SM 7 7 7 /// Medium dense to dense sands Stiff to hard silt and lean clay Section C -C' 250 240 230 220 210 200 190 180 170 160 150 140 130 120 ELEVATION (feet) GEOLOGIC CROSS SECTION A -A' and C -C' Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: January 30, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-25 ELEVATION (feet) 0 B 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 Property Line Building (Setback 1 Stiff to hard silt and lean clay 20' SM ML Approximate existing ground surface Loose to medium dense sands Medium dense to dense sands 7 B-8 (offse Wetland 3 SM B-6 ( SM ML ML Stiff to hard silt and lean clay SM Approxi mate piezometric surface O U) > 1. ML B' 40 80 Horizontal and Vertical Scale in Feet Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. Section B -B' 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 ELEVATION (feet) GEOLOGIC CROSS SECTION B -B' Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., OTTO ROSENAU & Tukwila, Washington ASSOCIATES, INC. Date: January 30, 2008 For: Mr. Jawaid Amon ORA Project Number: 06-373 A-26 ELEVATION (feet) D 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 0 40 80 Horizontal and Vertical Scale in Feet SM ML Stiff to hard silt and lean clay Approximate ,_.piezometric surface Approximate existing ground surface Loose to medium dense sands Medium dense to dense sands Section D -D' Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. a) m M D' SP -SM ----------s-------- SP-SM vvv 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 ELEVATION (feet) GEOLOGIC CROSS SECTION D -D' Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., OTTO ROSENAU & Tukwila, Washington ASSOCIATES, INC. Date: January 30, 2008 For: Mr. Jawaid Amon ORA Project Number: 06-373 A-27 ELEVATION (feet) 0 40 80 Horizontal and Vertical Scale in Feet 250 250 240 230 220 210 200 190 180 170 160 150 E 0 (0 Property Line Approximate existing ground surface Building Setback 20'20' Approximate piezometric surface E' Loose to medium dense sands a) > co SP -SM & SW 7 SP -SM & SM Stiff to hard silt and lean clay Section E -E' Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. Medium dense to dense sands 250 250 240 230 220 210 200 190 180 170 160 150 ELEVATION (feet) GEOLOGIC CROSS SECTION E -E' Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: January 30, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-28 Glacially-overidden surface ELEVATION (feet) 310 300 290 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 Western Boundary Scarp Advance Outwash, Qva Property Line Building `Setback 20' Approximate piezometric 00 surface Stiff to hard silt and lean clay Loose to medium dense sands F' //0 Stiff to hard silt and lean clay 0 50 100 Horizontal and Vertical Scale in Feet Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. Section F -F' • 310 300 290 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 ELEVATION (feet) GEOLOGIC CROSS SECTION F -F' Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: February 20, 2008 . OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-29 300 250 a) a) z 200 0 w 150 -J 100 50 0 Piezometric Surface, June 1962 0 Slade Way Sand and Siltm 2 0 Gray, Clayey Silt Silty Sand and Gravel Gray, Clayey to Sandy Silt (Tin Gray, Coarse Sand and Silt Gray, Fine Sand and Silt Gray_B rc'wn Clayey Silt Gravelly Lens --41/ Clayey, Silt Gray, Sand Proposed Cut for West Side of 1-5 H"tomedium sand Silt Silt Fill Fine to Medium Sand 0 100 200 Horizontal and Vertical Scale in Feet S & W Section B -B' Note: The location of all features shown is approximate. Reference: Generalized Soil Profiles A -A' and B -B' , Geotechnical Review of Proposed LeRoy Lowe Developement, Tukwila, Washington by Sannnon & Wilson, Inc, October, 1992. Please refer to the figure titled "Lidar Image Vicintiy Map" for an approximate location of this cross section. 300 250 200 150 100 50 0 ELEVATION (feet) SHANNON & WILSON GEOLOGIC CROSS SECTION B -B' Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: February 20, 2008 124----4 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-30 60 50 X 40 W 0 Z 30 U H Q 20 J d 10 7 4 0 10 16 20 30 40 50 60 LIQUID LIMIT 70 80 90 100 SYMBOL EXPLORATION NUMBER SAMPLE DEPTH MOISTURE CONTENT (%) LIQUID LIMIT (%) PLASTIC LIMIT (%) PLASTICITY INDEX, PI (%) SOIL DESCRIPTION • B-1 30 - 31.5 feet 32 45 I 19 I j O9 i i B-2 50 - 51.5 feet 29 33 26 7 Hard, gray SILT (ML) • B-3 50 - 51.5 feet 22 39 22 17 Hard, gray, lean CLAY (CL) • B-5 30 - 31.5 feet 30 33 26 7 Very stiff, gray SILT (ML) 13 / 1o x`, p i i G'' oc o / V , .ter / / ON' • MH or CH CL -ML / // Ci'6 / i / / ML or OL 10 16 20 30 40 50 60 LIQUID LIMIT 70 80 90 100 SYMBOL EXPLORATION NUMBER SAMPLE DEPTH MOISTURE CONTENT (%) LIQUID LIMIT (%) PLASTIC LIMIT (%) PLASTICITY INDEX, PI (%) SOIL DESCRIPTION • B-1 30 - 31.5 feet 32 45 26 19 Very stiff, gray SILT (ML) • B-2 50 - 51.5 feet 29 33 26 7 Hard, gray SILT (ML) • B-3 50 - 51.5 feet 22 39 22 17 Hard, gray, lean CLAY (CL) • B-5 30 - 31.5 feet 30 33 26 7 Very stiff, gray SILT (ML) Note: Atterberg limits determined in general accordance with the ASTM D 4318 test procedure. ATTERBERG LIMIT TEST RESULTS Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 1, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-31 Particle Size Distribution Report - ASTM D 422 < <_ _ < m _o 0_ o V H O O CO y �p O 10 n N 1p' M ik .- ik ik iF it E ,i E 100 I I I I I I I I I I I I 1 1 Y 1 1 1 I 1 1 1 1 1 1 1 1 I I 1 1 1 1 I 1 1 I I 1 1 I 1 I I 1 1 1 1 1 I I 1 1 1 90 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 80 I 1 I 1 I I I I 1 I I I I 1 1 I I 1 1 1 1 1 • 1 1 1 1 1 1 1 1 • 1 1 I I I I 1 I I 1 1 1 1 1 1 1 1 70 N LCL 1 1 1 I I I 1 1 I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 • 1 1 1 1 1 1 I 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 W 60 z E I— I I I I 1 1 1 I 1 1 1 I 11 I I I I 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 I I 1 1 1 1 I I I I 1 1 1 I I 1 I 1 1 1 Z 50 W 0 LL I I 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 I 1 I I 1 1 1 I 1 1 I 1 I 1 W 40 CL I I I 1 1 I I 1 1 I 1 1 1 1 1 1 1 11 1 I 1 I 1 1 I I 1 I 1 1 1 1 1 1 1 I 1 1 I 1 • 1 1 1 1 301 I I 1 1 1 I 1 1 1 1 1 1 I 1 I 1 1 1 1 1 1 1 1 1 1 1 I 1 I 1 1 I 1 I 1 1 1 1 1 1 1 1 1 I I 1 1 I 1 1 1 1 1 1 1 20 1 1 1 1 1 10 0 1 1 1 1 1 1 I 1 1 1 i 1 1 1 1 . I 1 1 1 1 1 i i , . 1 1 1 1 1 1 i ; 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 500 100 10 1 GRAIN 0 1 SIZE - mm 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 29.9 44.0 26.1 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT I (X=NO) Sample #2700 - B1 Sample #2: Gray Silty Sand with gravel 0.75 in. 0.625 in. 100.0 79.8 Atterberq Limits (ASTM D 4318) 0.5 in. 0.375 in. 0.25 in. #4 77.0 75.8 72.4 70.1 PL= NP LL= NV Pl= NP Classification #10 #40 #100 65.0 52.9 33.7 USCS= SM AASHTO= A-2-4(0) Coefficients #200 26.1 Dg5= 16.9 D60= 0.793 D50= 0.358 D30= 0.113 Di5= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 * (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B1 Sample #2 Elev./Depth: 5 to 6.5 feet Checked By: A. Coyne Title: P.E. OTTO ROSENAU s INC.53rd Client: Jawaid Amon Project: La Tourelle Short Plat Ave. S. & S. 160th St., Tukwila, WA Project No: 06-373 A-32 Particle Size Distribution Report - ASTM D 422 c _ _ C C C y O (O{�V O O {Otpp O O '0 1'1 N e7 e7 # i! ii is a i ; ; iL 100 I I 1 1 1 i ` l 1 1 I I 1 I I I 1 I 1 1 1 1 1 1 1 I 1 I 1 I 1 1 1 1 I Y 1 1 1 v 1 1 1 1 1 1 1 1 1 1 I I I 1 I 1 I I 1 1 I 90 I 1 1 1 1 I I 1 1 1 1 1 1 1 1 1 1 1 4 1 1 1 1 1 , 80 I I I I 1 I I 1 1 1 1 I 1 1 1 I 1 I I 1 1 I 1 1 I I I 1 1 1 1 1 1 -4 1 I I 1 I 1 1 1 I 1 I 1 1 1 1 I 1 I I I I 1 1 1 1 1 • 70 IX Ll.. I I I 1 1 I I I 1 I I I 1 I I I I 1 1 1 1 1 1 I 1 I I 1 1 1 I I 1 1 1 1 I 1 1 1 I I 1 1 1 1 I I 1 I I I I I I 1 I 1 I I 1 W 60 Z 1 I I I I 1 I 1 I 11 1 1 1 1 I I 1 I I I I I 1 1 I I 1 I I I I 1 1 I I I I 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 I I I I I • Z 50 W 0 rt I 1 1 1 I 1 1 1 1 1 1 1 , I 1 I 1 I 1 I I 1 1 1 1 I 1 1 I 1 1 * 1 1 I 1 1 1 1 1 1 I I 1 , 1 1 I I I I I I 1 W40 a 1 1 I I I 1 I I I I 1 1 1 I I I 1 I 1 1 1 1 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 . 301 I I I I I I I I I I I I I I I 1 1 I I I 1 1I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 I I 1 1 1 1 1 1 1 1 I 1 I 1 1 1 1 I 1 • 20 , i I 1 1 10 0 I I 1 1 1 1 1 1 I I I 1 1 1 1 I 1 I 1 1 1 1 1 1 1 I 1 1 1 I 1 I I I I I 1 I I 1 1 I 1 1 1 1 1 I I I 500 100 10 1 GRAIN 0 1 SIZE - mm 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 1.6 5.0 74.8 18.6 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B1 Sample #8: Dark Gray Silt 0.5 in. 0.375 in. 100.0 98.5 Atterberq Limits (ASTM D 4318) 0.25 in.4 #4 #10 #40 98.4 98.5 98.3 98.1USCS= PL= 26.3 LL= 45.4 PI= 19.1 Classification #100 #200 95.22 93.4 ML AASHTO= A-4(0) Coefficients 085= 0.0290 060= 0.0116 050= 0.0098 D30= 0.0068 D15= 0.0043 010= 0.0029 Cu= 3.99 Cc= 1.38 Date Tested: 7/27/2006 Tested By: A. Duong Remarks Classification (ASTM D2487) Test Equipment ID: 5 (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B1 Sample #8 Elev./Depth: 30 to 31.5 Checked By: A. Coyne Title: P.E. feet OTTO ROSENAU & ASSOCIATES INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-33 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 C C C C Mr M O O O O yOO�pp Oy �_ d O it i! R ik ik tk I I I 1 I 1 I 1 1 1 I I I I I I I I I 1 500 100 10 1 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND SILT % CLAY 0.0 0.0 1.0 99.0 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 #10 #40 #100 #200 100.0 100.0 100.0 99.5 99.0 (no specification provided) Sample No.: 2700 Source of Sample: Location: B1 Sample#16 Checked By: A. Coyne Soil Description Sample #2700 - BI Sample #16: Gray Silt Atterberq Limits (ASTM D 4318) PL= NT LL= NT Pl= NT Classification USCS= ML AASHTO= A-4(0) Coefficients D85= D60= 050= D30= D15= 010= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 60 to 61.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-34 Particle Size Distribution Report - ASTM D 422 100 1 1 1 1 11 1 1 1 1 1 1 1 1 1 I 1 90 r 1 1 r 1 1 1 1 i 1- 80 1 J 1 1 �, 1 11 1 1 1 , 1 1 1 1 1 1 , I 1 I 1 „ 1 70 N LCL I I I 1 , 1 I I 1 1 I W 60 z LI , z 50 W 0 cc W 40 d 30 20 10 0 500 100 10 1 GRAIN 0 1 0.01 0.001 SIZE - mm COBBLES % GRAVEL % SAND % SILT % CLAY 55.3 44.0 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B2 Sample #1: Light brown Silty Sand #4 #10 99.3 99.1 Atterberg Limits (ASTM D 4318) #40 #100 #200 98.7 70.6 44.0 PL= NT LL= NT Pl= NT Classification USCS= SM AASHTO= A-4(0) Coefficients D85= 0.243 060= 0.112 D50= 0.0870 D30= 015= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 * (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B2 Sample #1 Elev./Depth: 5 to 6.5 feet Checked By: A. Coyne Title: P.E. OTTO ROS E NAU & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA project No: 06-373 A-35 Particle Size Distribution Report - ASTM D 422 CC C O00 00 o O O 100 11 90 80 1 70 C LLI 60 Z 1-1 1 I I I I 1 Ii I 1 I I I 1 I 1 I 1 1 1 1 1 I 1 1 1 1 1 1 I I I 1 1 I I I 1 1 I I 1 I 1 1 11 1 1 1 1 1 I 1 1 1 I 1 1 1 z 50 w 0 cc I I 1 I 1 I 1 1 1 1 1 1 . 1 1 1 1 , . I 1 1 1 1 1 1 1 , 1 1 I 1 I 1 I 1 1 1 I 1 1 I 1 1 1 1 1 1 I 1 Lu 40 a_ 30 20 y 10 0 500 100 10 1 GRAIN 0 1 0.01 0.001 SIZE - mm % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 79.9 20.1 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B2 Sample #4: Light brown Silty Sand #4 #10 100.0 100.0 Atterberq Limits (ASTM D 4318) #40 #100 #200 99.8 68.6 20.1 PL= NT LL= NT Pl= NT Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 0.221 D60= 0.130 D50= 0.112 D30= 0.0852 D15= 010= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 * (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B2 Sample #4 Elev./Depth: 15 to 16.5 Checked By: A. Coyne Title: P.E. feet OTTO ROSENAU /+ & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA project No: 06-373 A-36 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 0 0 0 0 0 0 0 0 o a o int 0 0 u t. 500 100 10 1 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 4.2 38.6 57.2 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 #10 #40 #100 #200 100.0 100.0 99.5 97.4 95.8 (no specification provided) Sample No.: 2700 Source of Sample: Location: B2 Sample #12 Checked By: A. Coyne Soil Description Sample #2700 - B2 Sample #12: Gray Silt Atterberg Limits (ASTM D 4318) PL= 26.5 LL= 33.3 Pl= 6.8 Classification USCS= ML AASHTO= A-4(0) Coefficients D85= 0.0141 D60= 0.0052 050= 0.0044 D30= 0.0025 015= D10= Cu= Cc= Date Tested: 7/27/2006 Tested By: A. Duong Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 50 to 51.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-37 Particle Size Distribution C C C v C - C _ 7 c a N v. r �j o 0 u a Report - ASTM D 422 o O O 0 0 0 o a 'o E ; E a u loo I I I I 1 I I I I I I I I 1 I I 1 I 1 I `>' I I 1 I 1 I I 1 1 1 1 I 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 I 1 1 1 1 1 I 1 1 1 1 I I I 90 1 , • • , 1 1 I _ I 80 • • 70 CC W 60 Z LL Z 50 W 0 I I I , I I I , 1 1 1 1 , 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 I 1 1 1 1 I I 1 I I 1 I 1 I 1 L W 40 a I I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 I 1 I 1 1 1 I I 1 1 1 1 1 1 I 1 I 1 1 1 1 1 I I I I 1 I 1 I 1 I 1 1 1 30 • 20 f 1 1 1 1 1 10 0 500 100 10 1 GRAIN 0 1 SIZE - mm 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 20.6 64.7 14.7 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B3 Sample #6: Light brown, Silty Sand with 0.75 in. 0.625 in. 100.0 88.4 gravel Atterberq Limits (ASTM D 4318) 0.5 in. 0.375 in. 0.25 in.4 86.0 811.11 79.9 4 PL= NT LL= NT Pl= NT Classification #10 #40 #100 78.1 63.6 22.3 USCS= SM AASHTO= A-2-4(0) Coefficients #200 14.7 085= 11.7 D60= 0.393 D50= 0.317 D30= 0.196 D15= 0.0796 010= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 * (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B3 Sample #6 Elev./Depth: 15 to 16.5 Checked By: A. Coyne Title: P.E. feet OTTO ROSENAU & ASSOCIATES INC. f•Project Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA No: 06-373 A-38 Particle Size Distribution Report - ASTM D 422 CC C C 8 < 8 100 • • • 'i 1 , 90 __.. 1 80 70 W 60 Z L_ Z 50 W 0 CL I I1 1 1 1 1 1 1 1 t 1 , 1 I W 40 LI_ 30 20 10 0 500 100 10 1 GRAIN 0 1 0.01 0.001 SIZE - mm % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 9.5 2.7 87.8 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B3 Sample #13: Gray, lean CLAY 0.5 in. 0.375 in. 100.0 92.1 Atterberq Limits (ASTM D 4318) 0.25 in.4 #4 #10 #40 90.5 90.5 90.5 90.1 PL= 22.3 LL= 38.8 PI= 16.5 Classification #100 #200 88.6 87.8 USCS= CL AASHTO= A-4(0) Coefficients D85= D60= D50= D30= D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder, A. Duong Remarks Classification (ASTM D2487) Test Equipment ID: 5 * (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B3 Sample #13 Elev./Depth: 50 to 51.5 Checked By: A. Coyne Title: P.E. feet OTTO ROSENAU & ASSOCIATES INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-39 Particle Size Distribution Report - ASTM D 422 C C - ,9 C O O O O O < O TF -100 1 1 I 1 1 1 1 1 1 1 1 I• 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 I 1 1 1 1 1 I I I iii I I 1 90 1 • I 80 70 CC W 60 Z_ Li Z 50 W U 1 1 1 , 1 1 1 ' 1 1 1 1 1 1 , 1 1 1 1 1 W 40 a 1 • 30 v 1 20 1 1 1 10 0 1 1 1 1 1 1 1 1 1 1 i 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 I 1 500 100 10 1 0 1 GRAIN SIZE - mm 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 64.4 25.7 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B4 Sample #2: Gray, Silty sand 0.75 in. 0.625 in. 95.6 95.6 Atterberq Limits (ASTM D 4318) 0.5 in. 0.375 in. 0.25 in. #4 93.7 93.0 91.3 90.1 PL= NT LL= NT Pl= NT Classification #10 #40 #100 86.9 76.2 36.3 USCS= SM AASHTO= A-2-4(0) Coefficients #200 25.7 D85= 1.40 060= 0.294 D50= 0.230 D30= 0.108 D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 + (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B4 Sample #2 Elev./Depth: 5 to 6.5 feet Checked By: A. Coyne Title: P.E. OTTO ROS E NAU s INC.53rd Client: Jawaid Amon Project: La Tourelle Short Plat Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-40 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 74 V co O O O pO Op P 0 _ it ik O O it i! it 500 100 10 1 GRAIN SIZE - mm 0 1 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 86.8 13.2 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 #10 #40 #100 #200 100.0 99.8 97.5 32.7 13.2 (no specification provided) Sample No.: 2700 Source of Sample: Location: B4 Sample #5 Checked By: A. Coyne Soil Description Sample #2700 - B4 Sample #5: Light brown Silty sand Atterberq Limits (ASTM D 4318) PL= NT LL= NT P1= NT Classification USCS= SM AASHTO= A-2-4(0) Coefficients D 85= 0.357 D60= 0.248 D50= 0.211 D 30= 0.140 D15= 0.0816 D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 15 to 16.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-41 Particle Size Distribution C C C - O O Report - ASTM D 422 O yCy �0,p 0 O 0 100 1 1 1 1 I I 1 1 I I 1 1 I I 1 1 1 1 1 1 1 1 I I 1 1 1 1 Y 1 1 1 1 1 1 I 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 I I 1 1 I I I I 1 90 1 1 1 1 1 1 1 1 , 1 • 1 1 80 1 1 1 70 N 1 W 601 Z I --I 1 1 1 1 1 1 I 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 I I 1 1 1 I 1 1 1 I 1 1 1 1 I 1 1 1 1 I 1 I 1 1 I 1 1 1 1 1 1 1 1 I I Z 50 W 0 c 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Y W 40 a 30 20 10 0 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 500 100 10 1 GRAIN 0 1 SIZE - mm 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 H 51.2 48.8 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B4 Sample #9: Light brown Silty sand #4 #10 100.0 99.9 Atterberq Limits (ASTM D 4318) #40 #100 1 #200 98.9 84.1 48.8 PL= NT LL= NT Pl= NT Classification USCS= SM AASHTO= A-4(0) Coefficients D85= 0.154 D60= 0.0911 D50= 0.0766 D30= D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 * (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B4 Sample #9 Elev./Depth: 35 to 36.5 Checked By: A. Coyne Title: P.E. feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA project No: 06-373 A-42 Particle Size Distribution Report - ASTM D 422 . C C G 0.- O CC �p 0o < 0O Nh O a a # i! a 100 1 90 ' 80 1 I I I 1 I I I I ' I I I I I 1 I I 70 W 60 Z L_ z 1 501 U cc 1 1 II 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I I I 1 1 1 1 , T 1 1 I 1 4 I 1 1 1 1 1 I 1 1 1 , 1 1 1 1 1 1 1 W40 a_ 30 1 20 10 0 I I Y 500 100 10 1 GRAIN 0 1 SIZE - mm 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 92.8 7.2 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B5 Sample #2: Light brown, poorly -graded #4 #10 100.0 100.0 Sand with silt Atterberg Limits (ASTM D 4318) #40 #100 #200 93.6 12.4 1 7.2 PL= NT LL= NT PI= NT Classification USCS= SP -SM AASHTO= A-3 Coefficients D85= 0.390 D60= 0.300 D50= 0.269 D30= 0.208 D15= 0.160 D10= 0.109 Cu= 2.76 Cc= 1.33 Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B5 Sample #2 Elev./Depth: 5 to 6.5 feet Checked By: A. Coyne Title: P.E. OTTO ROSENAU & ASSOCIATES,INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-43 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 0 0 0 # a 0 0 0 0 0 o a o • r 500 100 10 1 GRAIN SIZE - mm 01 0.01 0.001 COBBLES 0.0 % GRAVEL 0.0 % SAND 91.5 % SILT 8.5 % CLAY SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 #10 #40 #100 #200 100.0 100.0 97.6 20.7 8.5 (no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #4 Checked By: A. Coyne Soil Description Sample #2700 - B5 Sample #4: Light brown, poorly -graded Sand with Silt Atterberp Limits (ASTM D 4318) PL= NT LL= NT Pl= NT Classification USCS= SP -SM AASHTO= A-3 D85= 0.370 D30= 0.182 Cu= 3.01 Coefficients 060= 0.277 D15= 0.126 Cc= 1.29 050= 0.244 010= 0.0920 Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 10 to 11.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-44 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 ss 000 0 O O o a o 500 100 10 1 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 77.1 22.9 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 #10 #40 #100 #200 100.0 100.0 100.0 86.5 22.9 } (no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #6 Checked By: A. Coyne Soil Description Sample #2700 - B5 Sample #6: Light brown Silty Sand Atterberq Limits (ASTM D 4318) PL= NP LL= NV Pl= NP Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 0.148 D60= 0.112 D30= 0.0810 D15= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 D50= 0.100 010= Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 20 to 21.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-45 Particle Size Distribution < <<vz-z o oao08?8 Report - ASTM D 422 100 .---.. 90 4 4 804 70 CL W 60 Z LI Z 50 W U ce 1 , 1 , 1 1 , W 40 0 30 20 10 0 500 100 10 1 GRAIN 0 1 SIZE - mm 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 1.5 98.5 SIEVE PERCENT SPEC.* PASS? Soil Description SIZE FINER PERCENT (X=NO) Sample #2700 - B5 Sample #10: Gray Silt #4 #10 100.0 100.0 Atterberq Limits (ASTM D 43181 #40 #100 #200 99.9 99.3 98.5 PL= 26.5 LL= 33.0 Pl= 6.5 Classification USCS= ML AASHTO= A-4(8) Coefficients D85= D60= D50= D30= D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 * (no specification provided) Sample No.: 2700 Source of Sample: Date Sampled: 6/22/2006 Location: B5 Sample #10 Elev./Depth: 40 to 41.5 Checked By: A. Coyne Title: P.E. feet OTTO ROSE NAUClient: & ASSOCIATES INC. Jawaid Amon Project: La Tourelle Short Plat 53rd Ave. S. and S. 160th St., Tukwila, WA Project No: 06-373 A-46 SHEAR STRESS (ksf) 9 9 8 7 6 5 4 3 2 1 0 c = - 0.4 ksf 1 2 LEGEND: Phi = 37 T 1 0 1 2 3 4 5 6 7 8 9 1 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-1, Sample 9, Depth = 35 feet Soil Description: Gray Silt (ML) Phi = (I), measured angle of internal friction c = measured cohesion 0 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 1, 2008 IIMIN OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-47 SHEAR STRESS (ksf) 9 8 7 6 5 4 3 2 1 0 c=-0.7ksf 1 2 LEGEND: Phi = 34.5' 0 2 3 4 5 6 7 8 9 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-1, Sample 14, Depth = 55-56 feet Soil Description: Gray Silt with trace fine gravel (ML) Phi = 4, measured angle of internal friction c = measured cohesion 10 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St Tukwila, Washington Date: February 1, 2008 nimmilimml OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-48 SHEAR STRESS (ksfl 9 9 8 7 6 5 4 3 2 c = 0.33 ksf 0 -1 2 LEGEND: Phi = 30.3' 1 0 2 3 4 5 6 7 8 9 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 3, Depth = 12 feet Soil Description: Silty fine Sand (SP -SM) Phi = 4), measured angle of internal friction c = measured cohesion 0 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 1, 2008 '-' OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-49 SHEAR STRESS (ksfl 9 9 8 7 6 5 4 3 2 1 c = 0.25 ksf 0 1 2 LEGEND: '\ Phi = 33.7 / 0 1 2 3 4 5 6 7 8 9 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 5, Depth = 20 feet Soil Description: Dark gray Silty Sand (SM) Phi = 4), measured angle of internal friction c = measured cohesion 10 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 1, 2008 OTTO ROSENAU & _ ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-50 SHEAR STRESS (ksf) 9 8 7 6 5 4 3 2 1 c = 0.3 ksf 0 0 77t7/ 1 2 LEGEND: Phi = 32.3' 1 1 2 3 4 5 6 7 8 9 1 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 9, Depth = 35 feet Soil Description: Gray Silt (ML) Phi = (I), measured angle of internal friction c = measured cohesion 0 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St. Tukwila, Washington Date: February 1, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-51 `90 800 Curb line / �` 260 4_\` 280 \ '� '�- ``- '-- r �' i 1 \N V (WETLAND 11 ..•\ \ gp0 0 70 140 Horizontal and Vertical Scale in Feet LEGEND O B-1 through B-5 B-6 through B-8 , Property line 200 1_. - - -- -- + o �VD 0 \ \ t• `'so B-5 B-4 `�- �'0 ®B-2 \ i `,`� 60. / .-\ Y� o \ ! l I_ • -- \ 1 l °�� I {WETLAND 2F �I t B-7 \, \•, ‘00 I_ `-, t , ( B-6 `co\ A\ Borings completed by ORA in June 2006 Borings completed by ORA in April 2007 Location of geologically most stable area f \ • N E N N 130' Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. LOCATION OF GEOLOGICALLY MOST STABLE AREA Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: January 30, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-52 Depth Below Ground Surface (ft) 0 0 10 20 30 40 50 60 70 80 90 100 Factor of Safety Against Liquefaction B-1 1 2 Y = Loose Fine with Becomes I to medium Sand (SM) a Silt (SP -SM). wet at a I I I Stiff to hard (Silt (ML). Moist to wet. - I I T " T r - dense Silty nd Fine Sand bout 2.3 feet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983) and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. Granular soils with (N1)60 blow counts greater than or equal to 30 are considered to dense to liquefy. Non -liquefiable soils are shown as having a factor of safety equal to 1.5. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-1 Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 1, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-53 Depth below Ground Surface (ft) 0 10 20 30 40 50 60 70 80 0 Factor of Safety Against Liquefaction B-2 1 I I I I I I I I I I I I I I M I I I Loose Fine S with Sil I Becom I I I I � I L I I I _ L i I I I � i Stiff to hard Silt (ML) r i _ - L _ o medium dense Silty ind (SM) and Fine Sand (SP -SM). �s wet at about 17.5 feet. Moist to wet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983) and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. Granular soils with (N1)60 blow counts greater than or equal to 30 are considered to dense to liquefy. Non -liquefiable soils are shown as having a factor of safety equal to 1.5. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-2 Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 1, 2008 OTTO ROSENAU & _.. ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-54 Depth Below Ground Surface (ft) Factor of Safety Against Liquefaction B-3 0 0 10 20 30 40 50 60 70 1 2 dense fine Sand with SM) to 18 feet. Grades im dense to dense fine h Silt (SP -SM) and Silty M) from about 18 to 44 timated groundwater about 24 feet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983) and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. Granular soils with (N1)60 blow counts greater than or equal to 30 are considered to dense to liquefy. Non -liquefiable soils are shown as having a factor of safety equal to 1.5. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-3 Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St. Tukwila, Washington Date: February 1, 2008 For: Mr. Jawaid Amon OTTO ROSENAU & __._ ASSOCIATES, INC. ORA Project Number: 06-373 A-55 r r L Medium L Silt (SP- to mediL Sand wii Sand (S 1 — r feet. Es level at 4 r 4- — Hard lean Clay (CL). Moist to wet. — r L dense fine Sand with SM) to 18 feet. Grades im dense to dense fine h Silt (SP -SM) and Silty M) from about 18 to 44 timated groundwater about 24 feet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983) and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. Granular soils with (N1)60 blow counts greater than or equal to 30 are considered to dense to liquefy. Non -liquefiable soils are shown as having a factor of safety equal to 1.5. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-3 Project Name: La Tourelle Short Plat Location: 53rd Ave. S. and S 160th St. Tukwila, Washington Date: February 1, 2008 For: Mr. Jawaid Amon OTTO ROSENAU & __._ ASSOCIATES, INC. ORA Project Number: 06-373 A-55 Elevation (feet) 280 270 260 250 240 230 220 210 200 190 180 0 Project: La Tourelle (Static Condition) Slope Stability Analysis Method: Morgenstern -Price S. 160th St Name: SILT and Weight: 120 pcf Cohesion: 300 p Phi: 26 CLAY Property Line 20' Name: Medium Dense to Dense SAND and Medium Sti Weight: 105 pcf Cohesion: 75 psf Phi: 28 ° Factor of Safety: 2.240 Name: Loose to Medium Dense SAND and Medium Stiff SILT Weight: 105 pcf Cohesion: 50 psf Phi: 28 ° Assumed Piezometric Surface — Wetland 3 20 40 60 80 100 120 140 160 180 200 Distance (feet) Section B -B' A-56 220 240 260 280 300 320 280 270 260 250 240 230 220 210 200 190 180 340 Elevation (feet) 280 270 260 250 240 230 220 210 200 190 180 Method: Morgenstern -Price S. 160th St Project: La Tourelle (EQ Load and Liquefied Soils) Property Line 20' Slope Stability Analysis Factor of Safety: 0.487 Name: Liquefiable SAND and SILT Weight: 105 pcf Name: Loose to Medium Dense SAND and Medium Stiff SILT Cohesion: 100 psf Weight: 105 pcf Phi: 0 ° Cohesion: 50 psf Phi: 28 ° — 280 Assumed Piezometric Surface — Wetland 3 Name: SILT and CLAY' Weight: 120 !pcf Cohesion: 300 psf Phi: 26 ° Name: Medium Dense to' Weight: 105 pcf Cohesion: 75 psf Phi: 28 AND and Medium Sti 0 20 40 60 80 100 120 140 160 180 200 Distance (feet) Section B -B' A-57 220 240 260 280 300 320 270 260 250 240 230 220 210 200 190 180 340 Elevation (feet) Method: Morgenstern -Price S. 160th St 250 Property Line i 20' Project: La Tourelle (Static Condition) 240=^---•..��r11‘MONIPPV 230 220 210 200 190 180 170 160 Slope Stability Analysis -- Name: SILT and CLAY Weight: 120 pcf Cohesion: 300psf Phi: 26 ° Factor of Safety: 2.9339 Name: Loose to Medium Dense SAND and Medium Stiff SILT Weight: 105 pcf Cohesion: 50 psf Phi: 28 ° Assumed Piezometric Surface 53rd Ave S Name: Medium Dense to Dense SAND and Medium Stiff SILT Weight: 105 pcf ion: 75 .sf •1 Phi: 28 1 1 I '1 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 Distance (feet) E -E' Section A-58 300 250 240 230 220 210 200 190 180 170 160 320 Elevation (feet) 250 240 230 220 210 200 190 180 170 160 0 Method: Morgenstern -Price S. 160th St Property Line i 20' 11111®111ftimst Assumed Piezometric Surface Project: La Tourelle (EQ Load and Liquefied Soils) Slope Stability Analysis Factor of Safety: 0.7779 Name: Liquefiable SAND and SILT Weight: 105 pcf Cohesion: 100 psf Phi: 0 ° Name: Loose to Medium Dense SAND and Medium Stiff SILT Weight: 105 pcf Cohesion: 50 psf Phi: 28 ° Name: SILT and CLAY Weight: 120 pet Cohesion: 300 psf Phi: 26 ° 53rd Ave S Name: Medium Dense to Dense SAND and Medium Stiff SILT Weight: 105 pcf Cohesion: 75 psf • 20 40 60 80 100 120 140 160 180 Distance (feet) E -E' Section A-59 250 240 230 220 210 200 190 180 170 160 200 220 240 260 280 300 320 280 270 260 N 250 p 240 (Ti N 230 W 220 210 200 Project: La Tourelle (Pre -Development Condition - Static Condition) Slope Stability Analysis Method: Morgenstern -Price Property Line S 160th St. 20' Factor of Safety: 1.877 Name: Loose to Medium Dense SANDS Unit Weight: 105 pcf Cohesion: 50 psf Phi: 28 ° Assumed Piezometric Surface Name: SILT and CLAY Unit Weight: 120 pcf Cohesion: 300 psf Phi: 26 ° 0 25 50 75 100 f i 1 125 Distance (feet) Section F -F' A-60 150 175 200 280 270 260 250 240 230 220 210 200 225 Elevation (feet) 280 270 260 250 240 230 220 210 200 0 Project: La Tourelle (Pre -Development, EQ Load and Liquefied Soils) Slope Stability Analysis Method: Morgenstern -Price S 160th St Property Line 20' Factor of Safety: 0.217 Name: Loose to Medium Dense SANDS Unit Weight: 105 pcf Cohesion: 50 psf Phi: 28 ° ,44401.000, 44.1111111111111114111111r Name: SILT and CLAY'. Unit Weight: 120 pcf!° Cohesion: 300 psf Phi: 26 Name: Liquefiable SAND and SILT Unit Weight: 105 pcf Cohesion: 100psf Phi: 0 ° Assumed Piezometric Surface 25 50 75 100 280 270 260 250 240 230 220 210 200 125 150 175 200 225 Distance (feet) Section F -F' A-61 280 270 260 250 O 240 a) 230 W 220 210 200 Project: La Tourelle (Developed Condition - Static Condition) Method: Morgenstern -Price Property Line S 160th St 20' Slope Stability Analysis Factor of Safety: 2.105 Name: Dense Sand and Gravel Fill Unit Weight: 125 pcf Cohesion: 25 psf Phi: 34 ° Assumed Piezometric Surfac Name: SILT and CLAY' Unit Weight: 120 pcf Cohesion: 300 psf Phi: 26 0 Name: Loose to edium Dense Unit Weight:. 105 pcf Cohesion: 50 psf Phi: 28 ° 1 25 50 75 100 125 Distance (feet) Section F -F' A-62 150 175 200 22', 280 270 260 412 250 p 240 crs N 230 W 220 210 200 Project: La Tourelle (Developed Condition - EQ Load and Liquefied Soils) Method: Morgenstern -Price Property Line 20' Slope Stability Analysis Factor of Safety: 0.181 Name: Dense Sand and Gravel Fill Weight: 125 pcf Cohesion: 25 psf Phi: 34 ° Name: Loose to Medium Dense SAND Weight: 105 pcf Cohesion: 50 psf Phi: 28 ° Assumed Piezometric Surface Name: SILT and'CLAY Weight; pcf; Cohesion: 300 p Phi: 26 0 25 50 75 Name: Liquefiable AND We ght: 105 pcf Cohesion: 100 psf Phi 0 ° 100 125 Distance (feet) Section F -F' A-63 150 175 200 280 270 260 250 240 230 220 210 200 225 Grade Beam Ground Surface Assumed Piezometric Surface Assumed Axial Load P = 30 kips Assumed Shear Load V = 30 kips J.1•.. ••••,,, • f. Assumed slide plane at very stiff to hard silt and clay or at dense sands Or - C. • • •1',' •r•I • Assumed: Fixed Head Condition 41.1 r ' it • .44 .sa Soils above piezometric surface assumed to be non -liquefiable Assumed zero skin friction through liquefiable soils 10' minimum embedment into very stiff to hard silt/clay or dense sands I I 2' ASSUMED PILE LOADING MODEL Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: January 29, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-64 0) Pile Capacity, Q (kip) 120 100 80 60 40 20 0 Allowable Axial Capacity vs Pile Length (Section B -B') 24 -inch diameter drilled shafts 0 10 20 30 Pile Length, L (ft) 40 50 60 OTTO ROSENAU & ASSOCIATES, INC. Project Title: La TourelleShort Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 01/30/2008 ORA Job No.: 06-373 112 Compression - - ♦ - - Uplift f 95 ♦ 92 ,7 ,i 75 41 59 •58 ,i4' 24 ,i25 43 ♦•5 ------♦•5-. 0 10 20 30 Pile Length, L (ft) 40 50 60 OTTO ROSENAU & ASSOCIATES, INC. Project Title: La TourelleShort Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 01/30/2008 ORA Job No.: 06-373 Pile Capacity, Q (kip) 100 90 80 70 60 50 40 30 20 10 0 Allowable Axial Capacity vs Pile Length (Section E -E') 24 -inch diameter drilled shafts 0 10 20 30 Pile Length, L (ft) 40 50 60 OTTO ROSENAU & _ _ ASSOCIATES, INC. Project Title: La Tourelle Short Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 01/30/2008 ORA Job No.: 06-373 95 - - + - - Uplift f Compression 82 69 ,r 68 55 .x'57 42 e'46 ,•'36 29 •'25 8 ,i016+.6- ♦3 •••7 0 10 20 30 Pile Length, L (ft) 40 50 60 OTTO ROSENAU & _ _ ASSOCIATES, INC. Project Title: La Tourelle Short Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 01/30/2008 ORA Job No.: 06-373 0) Pile Capacity, Q (kip) 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 Pile Length, L (ft) Allowable Axial Capacity vs Pile Length (Section F -F) 24 -inch diameter drilled shafts 40 50 60 OTTO ROSENAU & _... ASSOCIATES, INC. Project Title: La Tourelle Short Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 01/30/2008 ORA Job No.: 06-373 90 - - ♦ - - Uplift �— Compression 72 70 • 54 53 36 A.36 21 *'20 -*1 ♦$-----.6 40 50 60 OTTO ROSENAU & _... ASSOCIATES, INC. Project Title: La Tourelle Short Plat 53rd Ave S and S 160th St, Tukwila, WA Date: 01/30/2008 ORA Job No.: 06-373 t/– , 3% Min. Slope Impermeable soil cover Roof drain - tightline with glued or gasketed fittings — Final site grades should be sloped to drain away from foundation Not to scale • . • 4 at • Non -woven geotextile fabric - Mirafi 140N or equivalent 4" diameter, SDR 35 or Schedule 40, perforated pipe. Holes oriented downwards. Grade Beam Provide 6 mil vapor barrier over exposed soil in crawl space areas and required venting /— Drilled Shaft Notes: 1. The installation of the drilled shafts must be monitored on a full-time basis by an ORA representative. 2. All pipes should be sloped to drain to an approved discharge point. 3. Washed rock used as drainage material should consist of inch to 14 inch washed rock. 4. All temporary excavations must be completed in accordance with the recommendations of the geotechnical report for this project. TYPICAL FOUNDATION DETAIL Project Name: La Tourelle Short Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: February 1, 2008 For: Mr. Jawaid Amon OTTO ROSENAU & ASSOCIATES, INC. ORA Project Number: 06-373 A-68 co x a z W a a Q TU Sa802,©SRCO2, Otto Rosenau & Associates 6747 M. L. King Way South Seattle, Washington 98118 March 11, 2008 Geologic and Slope Stability Conditions Proposed La Tourelle Short Plat Tukwila, Washington File No.BAR4-01 This letter report summarizes our observations and conclusions regarding geologic and slope stability conditions in the vicinity of the proposed La Tourelle Short Plat in Tukwila, Washington. We understand that you are providing geotechnical engineering services to your client relative to the development of the proposed development. You have asked us to provide our opinions regarding geologic conditions within the site and nearby areas as they relate to slope instability within and near the site. Our conclusions are based on a review of previous reports in the vicinity of the site, information that you have developed and presented in your report dated March 11, 2008, site visits in December of 2007 and February of 2008, and our experience. That experience includes previous report reviews and reconnaissance in the vicinity of the site performed as part of a 1990 geologic hazards evaluation for the City of Tukwila. The proposed short plat is located along the west valley wall of the Green River Valley, west of 53rd Avenue South and north of South 160th Street, as shown in the Vicinity Map (Figure 1), and the Site Plan (Figure 2). As disclosed in previous nearby site explorations and your explorations within the subject site, the valley wall in the vicinity of the site is underlain by sandy soils overlying pre-Vashon very stiff to hard gray silt (see Geologic Cross Section F -F' - Figure 3). The gray silt is underlain by sand and gravel and perhaps glacial till, as shown in Figure 4, which is based on a 1992 Cross Section by Shannon & Wilson. As indicated in that cross-section, the pre-Vashon units appear to dip downward toward the northeast with inclinations of approximately 15 percent. The uppermost portion of the valley wall, west of the proposed short plat, is underlain by glacial outwash sand, which has been mapped as Vashon recessional outwash. Some recessional outwash probably does locally exist within the upland area at the top of the valley wall. However, dense sand was observed within the steep slope along the uphill side of South 160th Street, immediately upslope from the subject site, and the nearby upland area appears to be a glaciated surface, including scattered glacial erratics. We believe that the outwash sand underlying the uppermost portion of the valley wall in the vicinity of the site is Vashon advance outwash. 7505 West Lake Sammamish Parkway Northeast Redmond, Washington 98052 425-882-4850 www.tubbs.com Otto Rosenau & Associates March 1 l , 2008 Page 2 The subject site lies entirely within a landslide complex that extends nearly 4000 feet along the contour of the valley wall and which can be seen in the Lidar imagery shown in Figure 1. The existence of the landslide complex has been known since the 1960's, but its origin and the mechanisms of the landslide movements have not been well described. The landslide complex is bounded on the west by a steep scarp, typically ranging between 30 and 50 feet in height. The near surface soil unit within the landslide complex typically consists of loose to medium dense sand, with some medium dense to dense sand, and ranges up to approximately 50 feet in thickness. Groundwater levels within the surficial sandy soils near the base of the scarp are typically at or near the ground surface. The scarp is not uniform in character, but includes higher and steeper segments north of South 156th Street and south of South 160th Street, and less steep segments along its middle portion. Within this middle portion, areas of apparently glaciated topography locally extend across the interpolated scarp alignment (for instance, south of South 156th Street), and other areas exist (such as within Crystal Springs Park) where emergent groundwater and consequent slope instability has resulted in a number of small-scale scarps instead of a continuous scarp alignment. Approximately 40 feet of sandy outwash soils overlie the pre-Vashon silt immediately upslope of the landslide complex, but only about 20 feet of sandy material overlies the silt in your boring B-1. For this reason and because of the geomorphic characteristics described above, we do not believe that the western boundary scarp originated by down -dropping along a deep-seated failure surface. It is our opinion that the landslide complex originated as a result of a series of events that began during the retreat of the last (Vashon) glacier to occupy this area, approximately 13,500 years ago. Glacial scour from south-southwest moving ice and erosion along an ice -marginal drainage channel created an erosional bench along the valley wall, at an elevation of roughly 185 feet. The western margin of this ice -marginal erosion feature intersected the contact between the glacial advance outwash sand and the underlying pre-Vashon sediments. The outwash sand subsequently and progressively failed as a result of groundwater emerging along the contact with the underlying silty soils, and the failed material has since then episodically moved downslope across the upper surface of the pre-Vashon silt. The timing of landslide movements within the landslide complex are probably mainly a function of groundwater levels within the sandy landslide material, but some of the movement episodes may have occurred as a result of liquefaction of the failed material during seismic events. We understand that no movements are known to have occurred within the subject site during historic time; however this may only be due to the lack of observations within the site. Recent landslide movements are known to have occurred within nearby areas, downslope from 53rd Avenue South and Slade Way. 7505 West Lake Sammamish Parkway Northeast Redmond, Washington 98052 425-882-4850 www.tubbs.com Otto Rosenau & Associates March 11, 2008 Page 3 A landslide with a deeper failure surface, involving not just the previously failed sandy landslide material but also the pre-Vashon materials that underlie the lower portion of the valley wall, occurred in 1960 adjacent to an excavation within the lower portion of the valley wall. Additional movement occurred the following year in adjacent upslope areas where the upper, sandy soils were oversteepened by the 1960 landslide; we understand that the 1961 slide extended as far upslope as Slade Way. It is our opinion that the 1960 failure is not representative of the origin of the landslide complex or the mechanisms of failure elsewhere within the landslide complex. We trust that this report meets your present needs. If you have any questions regarding this report or if we can provide additional services, please call. Donald W. Tubbs Document ID: BAR40IRI Yours very truly, Tubbs Geosciences z‘tx Donald W. Tubbs, Ph.D. Engineering Geologist 7505 West Lake Sammamish Parkway Northeast Redmond, Washington 98052 425-882-4850 www.tubbs.com Note: The location of all features shown is approximate. Reference: Puget Sound LiDAR Consortium, Seattle, WA - "Q47122D32BE.TIF" 0 500 1000 APPROXIMATE SCALE (FEET) VICINITY MAP - FIGURE 1 Project Name: La Tourelle Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 20, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 Curb line \`r s� *\ \ \ 9° ` \ iso B o r- ` B-4 1 . L. S. 1 9TH ST. Property line B-1 HH -1 O - Curb line LEGEND • B-1 through B-5 Borings completed by ORA in June 2006 t B-6 through B-8 Borings completed by ORA in April 2007 • HH -1 Hand -Auger Exploration completed by ORA in February 2008 F F' Location of Geologic Cross Section 100 200 SCALE IN FEET Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. SITE PLAN - FIGURE 2 Project Name: La Tourelle Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 20, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 Glacially-overidden surface ELEVATION (feet) 310 300 290 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 Advance Outwash, Qva Western Boundary Scarp L 0 Cc Property Line Building / Setback 20' rn c • O m Approximate piezometric surface Stiff to hard silt and lean clay Loose to medium dense sands (o (a F' 310 • 300 • 290 • 280 • 270 260 250 240 • 230 • 220 • 210 • 200 190 180 170 160 150 140 130 120 //? Stiff to hard silt and lean clay 0 50 100 SCALE IN FEET Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. ORA Section F -F' ELEVATION (feet) ORA GEOLOGIC CROSS SECTION F -F' - FIGURE 3 Project Name: La Tourelle Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: February 20, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 ELEVATION (feet) 300 250 200 150 100 50 0 Piezometric Surface, June 1962 =Sand and 0 Silt. OD .. 0 0 Silty Sand and Gravel Gray. Clayey to Sandy Silt (rio?) Gray. Coarse Sand and Silt Gray, Fine Sand and Silt =--- Clayey, Silt Gray, Sand 100 200 SCALE IN FEET 0 Proposed Cut Fine to Medium Sand i 0 2 m 0. co 2 m Note: The location of all features shown is approximate. Reference: Generalized Soil Profiles A -A' and B -B' , Geotechnical Review of Proposed LeRoy Lowe Developement, Tukwila, Washington by Sannnon & Wilson, Inc, October, 1992. S & W Section B -B' Fine to Medium Sand 300 250 200 150 100 50 0 ELEVATION (feet) S & W GEOLOGIC CROSS SECTION B -B' - FIGURE 4 Project Name: La Tourelle Location: 53rd Ave. S and S 160th St. Tukwila, Washington Date: February 20, 2008 OTTO ROSENAU & ----- ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 Minnie Dhaliwal - Re: Fwd: La Tourelle Short Plat From: Joanna Spencer To: Minnie Dhaliwal Date: 09/18/2007 2:11 pm Subject: Re: Fwd: La Tourelle Short Plat Minnie, Page 1 Perfect timing. I have inserted copy of Sandra's e-mail to the packet that will be mailed out to S&W today. Thanks, Joanna »> Minnie Dhaliwal 09/18/2007 1:25 pm »> Hi Joanna, Please pass these on to Shannon and Wilson so that they are in the loop and know about hydrology concerns related to wetlands. Minnie »> Sandra Whiting 09/18/2007 11:24 am »> Minnie, I have reviewed the second geotech report dated August 29, 2007 and have the following comments/questions: 1. The explanation regarding groundwater measurements is still unclear (Section 6). What is the screen length of the peizometer installed at B-1? What are the characteristics of groundwater hydrology at the site? Is there a shallow groundwater flow and a deeper one? Where would seeps be expected to occur? Does groundwater flow follow topography in general? 2. What will be the impact on hydrology of wetlands downgradient of the site if roof, foot and other drainage is tightlined? if this water is discharged into the off-site downgradient wetland, what will be the impact? what will be the impact of the proposed project on the hydrology of the wetland proposed to be retained (and expanded)? This has not been addressed in the report. 3. Is groundwater drawdown on the site planned or not? The report states that "no assumptions have been made" regarding this. Finally, an issue not related to the report, but indicated in the new preliminary plat map is the apparent buffer reduction on the retained wetland. It seems to me that given that one wetland on the site is proposed for filling and that the remaining wetland will be expanded and enhanced as mitigation, that a buffer reduction for the mitigation wetland is not appropriate and not in keeping with the intent of the SAO. Let me know if you have any questions. Sandra Z 1 2 s may. ()'NG ENGIN Minnie Dhaliwal City of Tukwila Planning Department 6200 Southcenter Boulevard Tukwila, WA 98188 CIVIL ENGINEERING, LAND PLANNING, SURVEYING. ENVIRONMENTAL SERVICES December 6, 2007 COURIER DELIVERY RE: Request for Review of Revised Development Proposal Proposed Plat of La Tourelle (South 160th Street at 53rd Avenue South) Permit No. L06-089 Our Job No. 12650 Dear Minnie: RECEIVED CITY OF TUKWILA !DEC 0 7 20071 PERMIT CENTER Pursuant to your conversation with Alexia Dorsch of this office, I want to take this opportunity to discuss a revised development proposal that we would like to pursue for the above -referenced 4 -acre parcel at the northwest corner of the above intersection. As you know, we have been diligently working toward satisfaction of the "sensitive area" issues and requirements for this project that were first identified over a year ago. After exhaustive studies by several of our subconsultants, along with numerous discussions and plan revisions that we have conducted internally, I have determined that the applicant is best served if we amend the proposal as shown on the enclosed maps. We would like to meet with you on Tuesday, December 18, 2007, at 10 a.m. to discuss the revised proposal. I understand Alexia has already confirmed this time with you. I will be in attendance at that meeting, along with my client and Alexia. We do not intend to bring any of our subconsultants. I have enclosed five copies of the revised conceptual plan for you to review and distribute to staff as needed in advance of the meeting. I do not believe it is necessary to have the subconsultants involved in this discussion, based on the reasoning outlined below. The following is a summary of the key issues affecting development of this site that have been identified by the subconsultanls, as well as Shannon and Wilson, Inc., on behalf of the City of Tukwila, and, of course, by City staff. 1. The most significant issue affecting the development of this site is related to the geotechnical stability of the site. After extensive studies involving numerous deep borings and subsequent technical analysis of the field data collected, we have come to the conclusion (based on the information we have today) that the only area on the site that can be safely developed in a cost-effective manner is the area shown on the attached plan. This represents an area approximately 150 feet deep off South 160th Street, extending from the intersection of 53rd Avenue South to just west of the existing concrete retaining wall along South 160th Street, a distance of approximately 400 feet. This area has been identified by Otto Rosenau & Associates, Inc., after carefully considering all of the comments and concerns expressed by Shannon and Wilson, Inc., from the studies prepared for the site. The applicant has no desire to construct a project that would in any 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES • OLYMPIA, WA • TACOMA, WA • SACRAMENTO, CA • TEMECULA, CA www.barghausen.com Minnie Dhaliwal City of Tukwila Planning Department -2- December 6, 2007 way create concerns for stability in the future. Therefore, we believe the best course of action is to limit development of the property to the above area. A specific geotechnical summary is being prepared by Otto Rosenau & Associates, Inc., for resubmittal to Shannon and Wilson, Inc., reflecting these changes, and incorporating their recommendations into the proposal. 2. The other issue affecting development of the property has been the two small wetlands on the property and the complications associated with filling even one of these under the existing City of Tukwila Sensitive Area Guidelines. Although we believe we had been able to develop a proposal that could have met City requirements for filling the smaller wetland in the central portion of the site, limiting development to the area shown on the enclosed map will enable us to preserve both of these wetlands and their buffers without impact. By doing so, we will be in compliance with the Tukwila City Code with respect to wetland preservation. The advantages of developing this site under this option are as follows: • The property can be developed to its reasonable maximum density based on physical constraints and its current zoning classification, which will provide the additional housing units anticipated within the urban area. • The lots can be developed without significant grading being required, which is consistent with the recommendations of both geotechnical engineers. • Lot clearing will be limited to only what is required to provide for utility services, so that most of the identified site will remain undisturbed until individual Building Permits are applied for. • Approximately 70 percent of the site will be set aside as permanent open space. This open space will preserve the wetland areas and their buffers, as well as all other sensitive areas, including the steep slope along 53rd Avenue South. • The site will not be cleared and graded for construction of deep utilities and a public/private roadway as contemplated in the previous proposal, together with those related impacts. • Additional frontage improvements involving sidewalks would still be completed along the property frontage as required in the previous proposal, thereby completing a needed public improvement. • Individual homes can be constructed safety on lots within this "zone of geologic stability" through the use of shallow pile footings or other structural elements determined necessary by the geotechnical engineers. • Storm drainage will be controlled through individual home site systems, eliminating the requirement for extensive construction and site disturbance activity for drainage purposes. To summarize, our proposal is to seek development of the property through this revised proposal, which we believe minimizes environmental impacts and other construction -related impacts within the parcel that Minnie Dhaliwal City of Tukwila Planning Department: -3- December 6, 2007 is a significant benefit to the public. At the same time, our proposal still allows for reasonable development of the property as contemplated in the City of Tukwila's Land Use Plan while also preserving substantial open space. South 160th Street has numerous lots having direct access to it between 46th Avenue South and 53rd Avenue South. Although we are showing direct driveway access to South 160th Street for the proposed lots, we can also incorporate the use of shared driveways, where necessary, to minimize the number of new access points. Finally, the revised proposal would create a total of eight single-family lots and one open space tract. This will enable the applicant to also pursue development through the short plat process rather than a formal subdivision. As a result, we would be proposing to withdraw the Formal Plat Application and submit for a short plat approval as allowed by City Code. I look forward to meeting with you and other members of City staff to discuss this concept so that we can, hopefully, proceed forward with a revised application as soon as possible. Thank you. Respectfully, Thomas A. Barghausen, P.E. President TAB/tep 12650c.017.doc enc: As Noted cc: Joe Amon (w/enc) Raymond van der Roest, Barghausen Consulting Engineers, Inc. (w/enc) Alexia D. Dorsch, Barghausen Consulting Engineers, Inc. (w/enc) OTTO ROSENAU & ASSOCIATES, INC. March 11, 2008 Geotechnical Engineering, Construction Inspection & Materials Testing 6747 M. L. King Way South, Seattle, Washington 98118-3216 USA Tel: (206) 725-4600 • Toll Free: (888) OTTO-4-US • Fax: (206) 723-2221 WBE W2F5913684 • WABO Registered Agency • Website: www.ottorosenau.com City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila Washington 98188 Re: Response to Second Geotechnical Peer Review Comments Proposed La Tourelle Short Plat South 160th Street and 53rd Avenue South Tukwila, Washington King County Parcel # 5379200005 and 5379200006 ORA Project Number: 06-373, Report No. 3 ORA prepared a revised report to address review comments related to the proposed La Tourelle Plat. The locations of our response to the review comments are listed below. • ORA performed three additional borings in the vicinity of a suspect topographic feature at the sit, i.e., the sag pond feature. ORA indicated that they did not observe indications of a slide plane, such as slickenside or a highly disturbed zone. They did not provide an explanation as to how the Wetland 3 feature may have been formed. Although the ORA report does not present subsurface profiles through the property ... ORA Response: Based on a review of recently -available LIDAR images for this area and our current understanding of the geology at the site, we agree that Wetland 3 is most likely a sag pond feature caused by past slope instability. We observed the presence of wood debris and organic soils to depths of about 14 feet below the existing site grade at Boring B-8, which is adjacent to Wetland 3. We also observed a significantly increased depth to the silt/clay contact in Boring B-8 as shown in our figure titled Geologic Cross -Section B -B'. The increased depth, at which the underlying very stiff to hard silt/clay layer is encountered at Boring B-8, could arguably be a result of slope instability that extended through the very stiff to hard silt/clay layer, but we interpret it to be an ice -marginal erosion feature. We did not encounter evidence of failure planes in our borings that might indicate failure planes extending through the very stiff to hard silt/clay layer. The increased depth, at which the underlying very stiff to hard silt/clay layer is encountered at Boring B-8, may be a result of slope instability depth that extended through the very stiff to hard silt/clay layer, or may be an ice -marginal erosion feature. We acknowledge this Section 9.2 On Site Slope Stability Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, WA Project No.: 06-373 Date: March 11, 2008 We have included 6 subsurface profiles on the project site as well as a 7th subsurface profile offsite on pages A-25 through A-30 of Appendix A. The offsite profile is based on a subsurface profile that Shannon & Wilson had included in a figure titled "Generalized Soil Profiles A -A' and 8-8" in a peer review that they completed for an adjacent site titled "Geotechnical Review of Proposed LeRoy Lowe Development, Tukwila, Washington" dated October 1992. • In our March 2007 letter we recommended that ORA clarify their summary of groundwater conditions groundwater conditions in Section 6 of their response letter that the conflicting statements were resolved, the summary is still unclear. Revised water levels for borings B-1 and B-2 are not presented on the boring logs.... ORA Response: As stated in our previous report it is difficult to directly observe groundwater levels in borings completed while using mud rotary drilling techniques. It is our opinion that the higher groundwater levels measured about one year after dri/ling are representative of the groundwater conditions at these locations. The boring logs completed for 8-1 and 8-2 have been updated to represent our most recent observations, which also match well with the measured laboratory moisture content determinations of samples collected at both locations at the time the explorations were completed. The boring logs for 8-1 and 8-2 have been updated to show the manner of piezometer construction at each location. The boring logs for each boring log on pages A-4 through A-20 have been updated with either a measured or estimated groundwater level at each boring location. The table in Section 6.0 presents a summary in the text of the report. We have assumed that the highest groundwater levels are present in our slope stability and liquefaction analyses. We provided an additional liquefaction analyses for the portions of the site being developed, which includes the area being developed in the vicinity of boring 8-3. The updated results of our liquefaction analyses for borings 8-1 through 8-3 are presented on pages A-49 through A-51 of the appendix. The area in the vicinity of borings 8-6 through B-8 are outside the limits of the currently proposed short plat development. The areas outside of the limits of the short plat development are to remain undeveloped and in its current condition and were not evaluated for liquefaction susceptibility. A tabular summary of the results liquefaction analyses is presented in Section 11.2 of the report and presents a summary of the estimated thickness of potentially liquefiable soils used in our analyses and our estimate of liquefaction -induced settlement. Otto Rosenau & Associates, Inc. Page 2 of 4 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, WA Project No: 06-373 Date: March 11, 2008 We have recommended that all of the proposed residential structures for the short plat development be supported on deep foundations that extend through the upper potentially -liquefiable soils and are embedded in the underlying very stiff to hard silt/clay or the dense to very dense sands that are present in some areas. The structures would then not be reliant on the underlying potentially -liquefiable soils to provide foundation support. • ORA performed additional slope stability analyses as requested. However, the horizontal seismic coefficient used is not consistent with their recommended peak ground acceleration (PGA) for International Building Code (IBC) design.... ORA Response: The slope stability analyses that evaluated stability under seismic loading conditions were revised to be consistent with our recommended IBC design values (Design PGA = 0.36 g). We used the normalized strength approach to estimate the shear strength of liquefied soils and estimated that the strength of the liquefied soil is likely 100 pounds per square foot (psf) or less. We used a value of 100 psf to model the shear strength of the liquefied soils in our slope stability analyses. • ORA provided a discussion on appropriate steep slope setback... ORA Response: The project scope has changed considerably and now requires that the proposed structures be embedded to a minimum depth to provide frost protection in order to reduce the amount of force that is generated by potentially unstable soils moving beneath the structures. No deep excavations are planned for the proposed residential structures. No dewatering is currently planned for the currently proposed project. • Section 10.3.2 of the report suggests that several structures will be pile -supported.... ORA Response: Detailed revised foundation recommendations are included in Section 11.3 of this report and reflect our recommendations that all of the proposed residential structures be supported on deep foundation elements. We have included a design for 2 - foot diameter drilled shafts. The design for the drilled shafts is based on an assumed loading condition. Final design for a drilled shaft or other type of deep foundation system must be completed once final loading conditions are determined. Dr. Donald Tubbs, Ph.D., L.G., L.E.G. of Tubbs Geosciences has been included as a member Otto Rosenau & Associates, Inc. Page 3 of 4 Otto Rosenau t Associates, incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Short Plat. South 160 Street and 53"' Avenue South, Tukwila, WA Project No.: 06-373 Date: March 11, 2008 of the design team to assist in evaluating the complex geology at the project site. Dr. Tubbs has provided geological review services on this project. Dr. Tubbs and Otto Rosenau & Associates, Inc. (ORA) completed a visual reconnaissance of the project site and the adjacent areas ort December 31, 2007 and on February 18, 2008. Dr. Tubbs' report titled "Geologic and Slope Stability Conditions" is included in Appendix B of this report. If you have any questions please contact us. Copies to: Addressee (8) Sincerely, Otto Rosenau & Associates, Inc. Anthony G. Coyne, P.E. Geotechnical Engineer Otto Rosenau & Associates, Inc. Page 4of4 SHANNON bWILSON, INC. GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS October 25, 2007 Ms. Joanna Spencer City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 RECEIVE OCT 29 2007 WWII r-UBLc KS ALASKA CALIFORNIA COLORADO FLORIDA MISSOURI OREGON WASHINGTON RE: SECOND GEOTECHNICAL PEER REVIEW, LA TOURELLE PLAT, SOUTH 160T11 STREET AND 53RD AVENUE SOUTH, TUKWILA, WASHINGTON Dear Ms. Spencer: This letter presents the results of our review of the second geotechnical engineering report for the above -referenced development in Tukwila, Washington. The development will be located on undeveloped land northwest of the intersection of South 160th Street and 53`d Avenue South. In this letter we offer an opinion as to the appropriateness and adequacy of the revised geotechnical report and responses prepared by Otto Rosenau & Associates, Inc. (ORA). Our opinions are based on information contained in the revised report, our previous visit to the site, review of available project files and the City of Tukwila Municipal Code, and our experience with other projects in the area. ORA submitted a revised geotechnical report to the City of Tukwila (City) on September 18, 2007. They addressed all of the comments provided in our letter to the City on March 8, 2007. ORA performed three additional borings, addressed groundwater conditions, performed limited liquefaction analyses, provided an estimate of liquefaction -induced settlement, and performed additional slope stability analyses. REVIEW COMMENTS The following continents present our opinions about ORA's responses to our March 8, 2007, letter: ► ORA performed three additional borings in the vicinity of a suspect topographic feature at the site, i.e., the sag pond feature. ORA indicated that they did not observe indications of a slide plane, such as slickenslides or a highly disturbed zone. They did not provide an 400 NORTH 34TH STREET • SUITE 100 P.O. BOX 300303 SEATTLE, WASHINGTON 98103 206.632.8020 FAX 206.695.6777 TDD: 1.800.833.6388 www.shannonwilson.com 21-1-20689-002 Ms. Joanna Spencer City of Tukwila October 25, 2007 Page 2 SHANNON FJWILSON, INC. explanation as to how the Wetland 3 feature may have been formed. Although the ORA report does not present subsurface profiles through the property, which would be very helpful in understanding the geology, we observed an unusual subsurface feature between the upper and lower soil units presented in Section B -B' (which we assume was created using the results of the three new borings). This feature is shown in the slope stability output on pages A-50 through A-55. The feature consists of a sharp depression in the contact between "Soil 1" and "Soil 2," and appears to be reflected in the overlying surface topography. It is our opinion that this feature is significant, and should be considered as evidence of possible pre -historic landsliding. Additionally, we observed anomalies in the logs of borings B-7 and B-8, consisting of low Standard Penetration Test (SPT) blow counts in the sand layer below higher blow counts. This may be interpreted as a weaker, disturbed zone within the sand layer and may be evidence of previous sliding. ► In our March 2007 letter, we recommended that ORA clarify their summary of groundwater conditions in Section 6 of their report. Although they stated in their response letter that the conflicting statements were resolved, the summary is still unclear. Revised water levels for borings B-1 and B-2 are not presented on the boring logs. In our previous review letter, we recommended that shallow groundwater levels be considered when evaluating slope stability and liquefaction potential. However, it appears that shallow groundwater levels were not consistently applied in ORA's slope stability analyses. Based on the standing water observed at the site and high groundwater observations in some of the borings, worst-case groundwater conditions should be considered in both the liquefaction and slope stability analyses. ORA performed liquefaction analyses for soil conditions of two borings performed at the site, B-1 and B-2. Results of the liquefaction analyses are presented on pages A-62 and A-63. On page A-63, there is a discrepancy in the number of samples analyzed for liquefaction and the number of samples retrieved/tested in boring B-2. Additionally, ORA did not include a statement in their report about the estimated depth of liquefaction. It is not clear as to how they used the results of the two borings to extrapolate the liquefaction potential across the site. Liquefaction of medium dense sands found in borings B-6, B-7, and B-8 should be evaluated. We recommend that ORA further explain their liquefaction analyses and subsequent foundation design recommendations related to mitigating liquefaction potential. ORA included an estimate of liquefaction -induced settlement in their revised report. However, ORA did not indicate whether the estimate was the same across the whole site, and what liquefaction depth was associated with the estimate. Furthermore, ORA indicated that if recommendations in their report were followed, settlement of the 21-1-20689-001 -L1/wp/LKD 21-1-20689-002 Ms. Joanna Spencer City of Tukwila October 25, 2007 Page 3 SHANNON &WILSON. INC. structure would be less than an inch. They do not explain how the settlement magnitude was reduced. It is not clear in the report whether overexcavation will mitigate all or just some of the liquefaction. potential. ORA should further explain their analyses regarding depth of liquefaction, overexcavation, and liquefaction -induced settlement for each proposed development lot. ► ORA performed additional slope stability analyses, as requested. However, the horizontal seismic coefficient used is not consistent with their recommended peak ground acceleration (PGA) for International Building Code (IBC) design. The recommended PGA provided on page 7 is 0.36g. Therefore, the horizontal seismic coefficient for slope stability analyses should be about 0.18g. It is likely that slope stability factors of safety will be less when the higher acceleration is used. In ORA's additional slope stability analyses, they considered liquefaction in the upper sandy soil unit. However, the residual strength, i.e., all cohesion and no friction angle, assigned to the liquefied case is greater than the equivalent non -liquefied, static shear strength (cohesion and friction angle) of the upper sandy soil unit. In our opinion, the assumed residual strength is not appropriate; it can not be greater than the static strength. We recommend considering the normalized strength approach when dealing with relatively shallow liquefiable soils. This approach is presented in "Geotechnical Earthquake.Engineering" (Kramer, 1996). ► ORA provided a discussion on appropriate steep slope setback and buffer distances in Section 10.7.3 of their revised report. However, in Section 10.3 of their revised geotechnical report, ORA indicated that a 12 -foot -high cut may be necessary near Lot 11. It appears that Lot 11 is about 25 feet away from Wetland 2. In our opinion, the hydrogeology of the wetland and the effect of a 12 -foot cut on groundwater should be evaluated. Dewatering could potentially impact the wetland. ► Section 10.3.2 of the report suggests that several structures will be pile -supported. Please state which structures need pile supports and describe how these structures will gain lateral resistance to seismic forces if the small pipe pile should not be relied upon for uplift or lateral resistance. As stated in our prior peer review letter: "Based on our review of available documents, it is apparent that the project site is located in an area of potential prehistoric landsliding and contains steep slopes with mappable zones of groundwater seepage. As such, it should be classified as a Class 4 area of potential geologic instability, as stated in Section 18.45.120 of the Tukwila Municipal Code." Based on the results of ORA's previous and additional explorations and analyses, we believe that this project should be evaluated by a licensed engineering geologist. 21-1-20689-001-L1 /wp/LKD 211-20689-002 -20689-002 Ms. Joanna Spencer City of Tukwila October 25, 2007 Page 4 SHANNON 6WILSON. INC. An engineering geologist is typically one who specializes in the "application of geologic principles to civil works," according to the Washington State Department of Licensing. The geology at the subject property is complicated and has not been clearly interpreted in the ORA report. In addition, Section 18.45.040, Part C.4, of the Tukwila Municipal Code states that "a geologist be included as part of the geotechnical consulting team", where appropriate. It is our opinion that it would be appropriate for a geologist, particularly a licensed engineering geologist, to be included in the evaluation of this proposed development. We would anticipate that an engineering geologist should assist in developing the following items for the geotechnical report: ► Detailed geologic subsurface profiles. ► Discussion regarding prehistoric and historic landsliding at the site and adjacent properties. ► Analysis of slope stability considering weak or liquefied sand layers. CONCLUSION In general, the revised geotechnical report that we reviewed is incomplete and not acceptable at this time. We recommend that the permit applicant have the Geotechnical Engineer of Record respond to these comments, enlist an engineering geologist on their project team, and submit a final report with analyses and calculations, clearly presented. Comments made during the review process do not relieve the project applicant or designer from compliance with code requirements, conditions of approval, or permit requirements; nor is the designer relieved of responsibility for a complete design in accordance with the laws of the State of Washington. This peer review is a check for compliance with generally accepted professional geotechnical engineering principles and practices used by geotechnical engineering firms in this area. 21-1-20689-001-L1 /wp/LKD 21-1-20689-002 Ms. Joanna Spencer City of Tukwila October 25, 2007 Page 5 SHANNON F&WILSON, INC. We appreciate the opportunity to be of service. If you have any questions or need clarification, we are available at (206) 632-8020. Sincerely, SHANNON & WILSON, INC. aureen M. Beinturn (McKenna), P.E. Senior Engineer EXPIRES: 04121 10 g Martin W. Page, P.E., L.E.G. Associate LMM:MWP:WTLIlmm 21-1-20689-001-L1/wp/LKD 21-1-20689-002 marimmammi OTTO ROSENAU & ASSOCIATES, INC. MINI March 11, 2008 Geotechnical Engineering, Construction Inspection & Materials Testing 6747 M. L. King Way South, Seattle, Washington 98118-3216 USA Tel: (206) 725-4600 • Toll Free: (888) OTTO-4-US • Fax: (206) 723-2221 WBE W2F5913684 • WABO Registered Agency • Website: www.ottorosenau.com City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila Washington 98188 Re: Response to Second Geotechnical Peer Review Comments Proposed La Tourelle Short Plat South 160th Street and 53rd Avenue South Tukwila, Washington King County Parcel # 5379200005 and 5379200006 ORA Project Number: 06-373, Report No. 3 ORA prepared a revised report to address review comments related to the proposed La Tourelle Plat. The locations of our response to the review comments are listed below. • ORA performed three additional borings in the vicinity of a suspect topographic feature at the sit, i.e., the sag pond feature. ORA indicated that they did not observe indications of a slide plane, such as slickenside or a highly disturbed zone. They did not provide an explanation as to how the Wetland 3 feature may have been formed. Although the ORA report does not present subsurface profiles through the property ... ORA Response: Based on a review of recently -available LIDAR images for this area and our current understanding of the geology at the site, we agree that Wetland 3 is most likely a sag pond feature caused by past slope instability. We observed the presence of wood debris and organic soils to depths of about 14 feet below the existing site grade at Boring B-8, which is adjacent to Wetland 3. We also observed a significantly increased depth to the silt/clay contact in Boring B-8 as shown in our figure titled Geologic Cross -Section B -B'. The increased depth, at which the underlying very stiff to hard silt/clay layer is encountered at Boring B-8, could arguably be a result of slope instability that extended through the very stiff to hard silt/clay layer, but we interpret it to be an ice -marginal erosion feature. We did not encounter evidence of failure planes in our borings that might indicate failure planes extending through the very stiff to hard silt/clay layer. The increased depth, at which the underlying very stiff to hard silt/clay layer is encountered at Boring B-8, may be a result of slope instability depth that extended through the very stiff to hard silt/clay layer, or may be an ice -marginal erosion feature. We acknowledge this Section 9.2 On Site Slope Stability. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Short Plat, South 160th Street and 53rd Avenue South, Tukwila, WA Project No.: 06-373 Date: March 11, 2008 We have included 6 subsurface profiles on the project site as well as a 7th subsurface profile offsite on pages A-25 through A-30 of Appendix A. The offsite profile is based on a subsurface profile that Shannon & Wilson had included in a figure titled "Generalized Soil Profiles A -A' and 8-8" in a peer review that they completed for an adjacent site titled "Geotechnical Review of Proposed LeRoy Lowe Development, Tukwila, Washington" dated October 1992. • In our March 2007 letter we recommended that ORA clarify their summary of groundwater conditions groundwater conditions in Section 6 of their response letter that the conflicting statements were resolved, the summary is still unclear. Revised water levels for borings B-1 and B-2 are not presented on the boring Togs.... ORA Response: As stated in our previous report it is difficult to directly observe groundwater levels in borings completed while using mud rotary drilling techniques. It is our opinion that the higher groundwater levels measured about one year after drilling are representative of the groundwater conditions at these locations. The boring logs completed for B-1 and 8-2 have been updated to represent our most recent observations, which also match well with the measured laboratory moisture content determinations of samples collected at both locations at the time the explorations were completed. The boring logs for 8-1 and 8-2 have been updated to show the manner of piezometer construction at each location. The boring logs for each boring log on pages A-4 through A-20 have been updated with either a measured or estimated groundwater level at each boring location. The table in Section 6.0 presents a summary in the text of the report. We have assumed that the highest groundwater levels are present in our slope stability and liquefaction analyses. We provided an additional liquefaction analyses for the portions of the site being developed, which includes the area being developed in the vicinity of boring 8-3. The updated results of our liquefaction analyses for borings 8-1 through 8-3 are presented on pages A-49 through A-51 of the appendix. The area in the vicinity of borings 8-6 through 8-8 are outside the limits of the currently proposed short plat development. The areas outside of the limits of the short plat development are to remain undeveloped and in its current condition and were not evaluated for liquefaction susceptibility. A tabular summary of the results liquefaction analyses is presented in Section 11.2 of the report and presents a summary of the estimated thickness of potentially liquefiable soils used in our analyses and our estimate of liquefaction -induced settlement. Otto Rosenau & Associates, Inc. Page 2 of 4 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Short Plat, South 160th Street and 53ftl Avenue South, Tukwila, WA Project No.: 06-373 Date: March 11, 2008 We have recommended that all of the proposed residential structures for the short plat development be supported on deep foundations that extend through the upper potentially -liquefiable soils and are embedded in the underlying very stiff to hard silt/clay or the dense to very dense sands that are present in some areas. The structures would then not be reliant on the underlying potentially -liquefiable soils to provide foundation support. • ORA performed additional slope stability analyses as requested. However, the horizontal seismic coefficient used is not consistent with their recommended peak ground acceleration (PGA) for International Building Code (IBC) design.... ORA Response: The slope stability analyses that evaluated stability under seismic loading conditions were revised to be consistent with our recommended IBC design values (Design PGA = 0.36 g). We used the normalized strength approach to estimate the shear strength of liquefied soils and estimated that the strength of the liquefied soil is likely 100 pounds per square foot (psf) or less. We used a value of 100 psf to model the shear strength of the liquefied soils in our slope stability analyses. • ORA provided a discussion on appropriate steep slope setback... ORA Response: The project scope has changed considerably and now requires that the proposed structures be embedded to a minimum depth to provide frost protection in order to reduce the amount of force that is generated by potentially unstable soils moving beneath the structures. No deep excavations are planned for the proposed residential structures. No dewatering is currently planned for the currently proposed project. • Section 10.3.2 of the report suggests that several structures will be pile -supported.... ORA Response: Detailed revised foundation recommendations are included in Section 11.3 of this report and reflect our recommendations that all of the proposed residential structures be supported on deep foundation elements. We have included a design for 2 - foot diameter drilled shafts. The design for the drilled shafts is based on an assumed loading condition. Final design for a drilled shaft or other type of deep foundation system must be completed once final loading conditions are determined. Dr. Donald Tubbs, Ph.D., L.G., L.E.G. of Tubbs Geosciences has been included as a member Otto Rosenau & Associates, Inc. Page 3 of 4 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawaid Amon Job Name: La Tourelle Short Plat. South 160" Street and 53`" Avenue South, Tukwila, WA Project No.: 06-373 Dale: March 11, 2008 of the design team to assist in evaluating the complex geology at the project site. Dr. Tubbs has provided geological review services on this project. Dr. Tubbs and Otto Rosenau & Associates, Inc. (ORA) completed a visual reconnaissance of the project site and the adjacent areas on December 31, 2007 and on February 18, 2008. Dr. Tubbs' report titled "Geologic and Slope Stability Conditions" is included in Appendix B of this report. If you have any questions please contact us. Copies to: Addressee (8) Sincerely, Otto Rosenau & Associates, Inc. 114.04, Anthony G. Coyne, P.E. Geotechnical Engineer Otto Rosenau & Associates, Inc. Page 4 of 4 TUBBS Otto Rosenau & Associates 6747 M. L. King Way South Seattle, Washington 98118 March 11. 2008 Geologic and Slope Stability Conditions Proposed La Tourelle Plat Tukwila. Washington File No.BAR4-01 This letter report summarizes our observations and conclusions regarding geologic and slope stability conditions in the vicinity of the proposed La Tourelle Plat in Tukwila, Washington. We understand that you are providing geotechnical engineering services to your client relative to the development of the proposed development. You have asked us to provide our opinions regarding geologic conditions within the site and nearby areas as they relate to slope instability within and near the site. Our conclusions are based on a review of previous reports in the vicinity of the site, information that you have developed and presented in your report dated March 1 1.2008, site visits in December of 2007 and February of 2008, and our experience. That experience includes previous report reviews and reconnaissance in the vicinity of the site performed as part of a 1990 geologic hazards evaluation for the City of Tukwila. The proposed plat is located along the west valley wall of the Green River Valley, west of 53rd Avenue South and north of South 160th Street, as shown in the Vicinity Map (Figure 1), and the Site Plan (Figure 2). As disclosed in previous nearby site explorations and your explorations within the subject site, the valley wall in the vicinity of the site is underlain by sandy soils overlying pre-Vashon very stiff to hard gray silt (see Geologic Cross Section F -F' - Figure 3). The gray silt is underlain by sand and gravel and perhaps glacial till, as shown in Figure 4, which is based on a 1992 Cross Section by Shannon & Wilson. As indicated in that cross-section, the pre-Vashon units appear to dip downward toward the northeast with inclinations of approximately 15 percent. The uppermost portion of the valley wall. west of the proposed plat, is underlain by glacial outwash sand, which has been mapped as Vashon recessional outwash. Some recessional outwash probably does locally exist within the upland area at the top of the valley wall. However. dense sand was observed within the steep slope along the uphill side of South 160th Street. immediately upslope from the subject site, and the nearby upland area appears to be a glaciated surface, including scattered glacial erratics. We believe that the outwash sand underlying the uppermost portion of the valley wall in the vicinity of the site is Vashon advance outwash. 7505 West Lake Sammamish Parkway Northeast Redmond, Washington 98052 425-882-4850 www.tubbs.com Otto Rosenau & Associates March 11. 2008 Page 2 The subject site lies entirely within a landslide complex that extends nearly 4000 feet along the contour of the valley wall and which can be seen in the Lidar imagery shown in Figure 1. The existence of the landslide complex has been known since the 1960's. but its origin and the mechanisms of the landslide movements have not been well described. The landslide complex is bounded on the west by a steep scarp, typically ranging between 30 and 50 feet in height. The near surface soil unit within the landslide complex typically consists of loose to medium dense sand. with some medium dense to dense sand, and ranges up to approximately 50 feet in thickness. Groundwater levels within the surficial sandy soils near the base of the scarp are typically at or near the ground surface. The scarp is not uniform in character, but includes higher and steeper segments north of South 156th Street and south of South 160th Street. and less steep segments along its middle portion. Within this middle portion, areas of apparently glaciated topography locally extend across the interpolated scarp alignment (for instance, south of South 156th Street), and other areas exist (such as within Crystal Springs Park) where emergent groundwater and consequent slope instability has resulted in a number of small-scale scarps instead of a continuous scarp alignment. Approximately 40 feet of sandy outwash soils overlie the pre-Vashon silt immediately upslope of the landslide complex. but only about 20 feet of sandy material overlies the silt in your boring B-1. For this reason and because of the geomorphic characteristics described above. we do not believe that the western boundary scarp originated by down -dropping along a deep-seated failure surface. It is our opinion that the landslide complex originated as a result of a series of events that began during the retreat of the last (Vashon) glacier to occupy this area, approximately 13.500 years ago. Glacial scour from south-southwest moving ice and erosion along an ice -marginal drainage channel created an erosional bench along the valley wall, at an elevation of roughly 185 feet. The western margin of this ice -marginal erosion feature intersected the contact between the glacial advance outwash sand and the underlying pre-Vashon sediments. The outwash sand subsequently and progressively failed as a result of groundwater emerging along the contact with the underlying silty soils, and the failed material has since then episodically moved downslope across the upper surface of the pre-Vashon silt. The timing of landslide movements within the landslide complex are probably mainly a function of groundwater levels within the sandy landslide material, but some of the movement episodes may have occurred as a result of liquefaction of the failed material during seismic events. We understand that no movements are known to have occurred within the subject site during historic time; however this may only be due to the lack of observations within the site. Recent landslide movements are known to have occurred within nearby areas, downslope from 53rd Avenue South and Slade Way. 7505 West Lake Sammamish Parkway Northeast Redmond. Washington 98052 425-882-4850 www.tubbs.com Otto Rosenau & Associates March 11. 2008 Page 3 A landslide with a deeper failure surface, involving not just the previously failed sandy landslide material but also the pre-Vashon materials that underlie the lower portion of the valley wall, occurred in 1960 adjacent to an excavation within the lower portion of the valley wall. Additional movement occurred the following year in adjacent upslope areas where the upper, sandy soils were oversteepened by the 1960 landslide: we understand that the 1961 slide extended as far upslope as Slade Way. It is our opinion that the 1960 failure is not representative of the origin of the landslide complex or the mechanisms of failure elsewhere within the landslide complex. We trust that this report meets your present needs. If you have any questions regarding this report or if we can provide additional services, please call. Donald W. Tubbs Document ID: BAR40I R I Yours very truly, Tubbs Geosciences Donald W. Tubbs, Ph.D. Engineering Geologist 7505 West Lake Sammamish Parkway Northeast Redmond, Washington 98052 425-882-4850 www.tubbs.Com Note: The location of all features shown is approximate. Reference: Puget Sound LiDAR Consortium, Seattle, WA - "Q47122D32BE.TIF" 0 500 1000 :TT APPROXIMATE SCALE (FEET) VICINITY MAP - FIGURE 1 Project Name: La Tourelle Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: February 20, 2008 126-3 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 ✓ Curb line S...159rH ST. \• -- �� Property line ��: - •• 1 B-4 1l 2B X B-1 HH -1 Curb Iine7 O' LEGEND • B-1 through B-5 Borings completed by ORA in June 2006 B-6 through B-8 Borings completed by ORA in April 2007 ® HH -1 Hand -Auger Exploration completed by ORA in February 2008 F F' Location of Geologic Cross Section o 100 200 \\\ SCALE IN FEET Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. SITE PLAN - FIGURE 2 Project Name: La Tourelle Location: 53rd Ave. S. and S 160th St Tukwila, Washington Date: February 20, 2008 For: Mr. Jawaid Amon OTTO ROSENAU & ASSOCIATES, INC. ORA Project Number: 06-373 Glaciallyoveridden surface ELEVATION (feet) 310 300 290 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 Advance Outwash, Qva HH Western Boundary Scarp L 0 lD rn Cc Sen Stiff to hard silt and lean clay iBuilding Setback / 20' Property Line m Approximate .o piezometric surface !SM ML 'GW Loose to medium dense sands SM Stiff to hard silt and lean clay SM F' 0 50 100 SCALE IN FEET Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. ORA Section F -F' 310 300 290 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 130 120 ELEVATION (feet) ORA GEOLOGIC CROSS SECTION F -F' - FIGURE 3 Project Name: La Tourelle Location: 53rd Ave. S and S 160th St. Tukwila, Washington Date: February 20, 2008 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 ELEVATION (feet) 300 250 200 150 100 50 0 Piezometric Surface, June 1962 = Sand and Silt m 0 Gray, Clayey Silt Silty Sand and Gravel Gray Clayey to Sandy Silt (Till?) Gray, Coarse Sand and Silt Gray, Fine Sand and Silt Clayey, Silt Gray, Sand Gray -Brown Clayey Silt Gravelly Lens 2 m 0 Proposed Cut Fine to Medium Sand o Silt rn 2 m 0 Silt Fill .01 rn CO w 0 Fine to Medium Sand 0 100 200 SCALE IN FEET Note: The location of all features shown is approximate. Reference: Generalized Soil Profiles A -A' and B -B' , Geotechnical Review of Proposed LeRoy Lowe Developement, Tukwila, Washington by Sannnon & Wilson, Inc, October, 1992. S & W Section B -B' 300 250 200 150 100 50 0 ELEVATION (feet) S & W GEOLOGIC CROSS SECTION B -B' - FIGURE 4 Project Name: La Tourelle Location: 53rd Ave. S and S 160th St. Tukwila, Washington Date: February 20, 2008 For: Mr. Jawaid Amon OTTO ROSENAU & ASSOCIATES, INC. ORA Project Number: 06-373 City of Tukwila Department of Community Development File Number Lob -DSc' LAND USE PERMIT ROUTING FOIllta,,L),„_s_ TO: Building ' Planning ,Public Works Fire Dept. =11 Police Dept. !_' Parks/Rec Project: Lct- To e_ 11-e. ISL` _A— Address: --, 160 w-- S 3 Ae S Date 1 / transmitted: Response requested by: Staff II '� coordinator:'`'�''"�'`E''`�'�' _ Date response received: REVIEWERS: Please specify how the attached plans conflict with your ADOPTED development regulations, including citations. Be specific in describing the types of changes you want made to the plans. When referencing codes, please identify the actual requirement and plan change needed. The Planning Division review does not supplant each department's ability to administer its own regulations and permits. However, project consistency at the Planning review stage is important to minimize significant later design changes. More than minimal design changes require further Planning Commission review, even if alteration is required to satisfy a City requirement. This further review is typically a minimum 60 -day process. Requirements based on SEPA (e.g., not required by an adopted development regulation) MUST identify the impact being mitigated, the policy basis for requiring mitigation, and the method used to calculate the mitigation required. Calculations of project impacts and the mitigation required (e.g., water capacity, road level of service analyses, or turning analyses) may be required of the applicant. COMMENTS (Attach additional comment sheets and/or support materials as needed.) S yeAA CLQ_ cam. y' es -,4/ Plan check date: Comments prepared by: Update date: Minnie Dhaliwal City of Tukwila Planning Department 6200 Southcenter Boulevard Tukwila, WA 98188 RE: Resubmittal of Geotechnical Report La Tourelle Preliminary Plat Permit No. L06-089 Our Job No. 12650 Dear Minnie: CIVIL ENGINEERING, LAND PLANNING. SURVEYING. ENVIRONMENTAL SERVICES September 4, 2007 COURIER DELIVERY Otto Rosenau and Associates, Inc. has revised the Geotechnical Report for the above - referenced project, dated August 15, 2006 in accordance with the comment/peer review letter by Shannon and Wilson, Inc. dated March 8, 2007. The revised report includes a letter including each of the comments made by Shannon and Wilson, Inc. and how they are addressed in the report. It is our understanding that the enclosed report addresses all of the comments received from Shannon and Wilson, Inc. and the City of Tukwila regarding geotechnical review to date. We understand that the report will be reviewed by the City's Public Works department, Sandra Whiting, and Shannon and Wilson, Inc. We respectfully request that all reviews be expedited, including the peer review performed by Shannon and Wilson, Inc. Please let me know if there are any forms necessary in order to expedite review. If you have questions or need additional information regarding this project, please do not hesitate to contact me at this office. Thank you. Sincerely, ..4:21s.:.,,Q..._ Alexia D. Dorsch Assistant Planner ADD/pj 12650c.015.doc enc: Three (3) copies of the Geotechnical Engineering Report with cover letter, Rosenau and Associates, Inc., dated August 29, 2007 cc: Joe Amon Anthony Coyne, Otto Rosenau and Associates, Inc. Ilon Logan, ESA Adolfson Tom Barghausen, Barghausen Consulting Engineers, Inc. Raymond van der Roest, Barghausen Consulting Engineers, Inc. prepared by Otto 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES 1 OLYMPIA, WA 1 TACOMA, WA 1 SACRAMENTO, CA 1 TEMECULA, CA www.barghausen.com RECEIVED CITY 7F 11 i(WQ,A SEP - 4 20011 PERMIT CENTER TO: U °Zs �` ; 6,- ccp 1 4 cu01 <?)NG ENG CIVIL ENGINEERING, LAND PLANNING, SURVEYING, ENVIRONMENTAL SERVICES LETTER OF TRANSMITTAL Minnie Dhaliwal COMMUNITY DEVELOPMENT DATE: September 14, 2007 SENT VIA: Courier Delivery City of Tukwila - Dept. of Community Development OUR JOB: 12650 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 RE: Revised Geotechnical Report Quantity Date Description I 08/29/07 Revised Geotechnical Report prepared by Otto Rosenau and Associates, Inc. Per your request. Signed: Alexia D. Dorsch Assistant Planner 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES 1 OLYMPIA, WA 1 TACOMA, WA • SACRAMENTO, CA • TEMECULA, CA www.barghausen.com 12650t.005.doc GEOTECHNICAL ENGINEERING REPORT PROPOSED LA TOURELLE PLAT SOUTH 160TH ST AND 53RD AVE S TUKWILA, WASHINGTON KING COUNTY PARCELS # 5379200005 AND #5379200006 PREPARED FOR: MR. JAWAID AMON BY: OTTO ROSENAU & ASSOCIATES, INC. ORA JOB No. 06-373, REPORT No. 2 OTTO ROSENAU & ASSOCIATES, INC. Geotechnical Engineering, Construction Inspection & Materials Testing OTTO ROSENAU & ASSOCIATES, INC. Geotechnical Engineering, Construction Inspection & Materials Testing 6747 M. L. King Way South, Seattle, Washington 98118-3216 USA Tel: (206) 725-4600 • Toll Free: (888) OTTO-4-US • Fax: (206) 723-2221 WBE W2F5913684 • WABO Registered Agency • Website: www.ottorosenau.com August 29, 2007 Mr. Jawaid Amon 16424 53rd Place South Tukwila Washington 98168 Re: Geotechnical Engineering Report Proposed La Tourelle Plat South 160th Street and 53`d Avenue South Tukwila, Washington King County Parcel # 5379200005 and 5379200006 ORA Project Number: 06-373, Report 2 Dear Mr. Amon: We are pleased to provide this revised report for the referenced project. The revisions to the original report are based on review comments provided by the City of Tukwila and Shannon & Wilson. Based on our subsurface explorations and our analyses, it is our opinion that the proposed residential development can be satisfactorily completed in accordance with the City of Tukwila development standards for an environmentally critical area, such as that present at the site. It is our opinion that it is possible to develop the site, provided that it is completed in accordance with the recommendations presented in this report. The primary concern for development in environmentally sensitive areas such as the project site is to not increase the risk of future slope instability. The primary ways that the risk of future slope instability can be reduced or minimized is to incorporate the following measures into the development of the project site. • Careful grading to minimize fills at the upland areas of the site to avoid increasing potential driving forces that could lead to slope instability. Overall, the project should be a net export or balance site. • This site is not suitable for on-site infiltration of stormwater runoff from impermeable surfaces such as roadways, paved surfaces and roofs. As a result, large detention facilities will likely be required. All piping and detention facilities should be designed to reduce exfiltration into the adjacent soils. • Significant overexcavations will be required to remove unsuitable organic soils and potentially liquefiable soils at most of the building lots. Alternatively, deep foundation support may be implemented to mitigate the presence of unsuitable soils. EXPIRES 1 Copies to: Ad. res ee (8) Sincerely, Otto Rosenau & Associates, Inc. Anthony G. Coyne, P.E. Geotechnical Engineer Otto Rosenau & Associates, Inc. Page 2 of 2 TABLE OF CONTENTS 1. INTRODUCTION 1 2. PROJECT DESCRIPTION 1 3. SCOPE OF SERVICES 1 4. SITE CHARACTERIZATION 2 5. SURFACE CONDITIONS 2 6. SUBSURFACE CONDITIONS 3 7. LABORATORY TESTING 5 8. REVIEW OF LITERATURE 5 9. DISCUSSION 6 10. CONCLUSIONS AND RECOMMENDATIONS 6 10.1 General 6 10.2 Seismic Considerations 7 10.3 Foundations 9 10.3.1 Shallow Foundations 10 10.3.2 Deep Foundations 10 10.4 Below -Grade Walls and Retaining Walls 12 10.5 Slabs -on -Grade 12 10.6 Earthwork 13 10.6.1 Site Clearing 13 10.6.2 Structural Fill 13 10.7 Site Slopes 15 10.7.1 Permanent Slopes 15 10.7.2 Temporary Slopes 16 10.7.3 Setbacks and Buffer 16 10.8 Slope Stability 16 10.9 Erosion and Sedimentation Control 20 10.10 Drainage 20 10.10.1 Construction Dewatering 20 10.10.2 Surface Drainage 20 10.10.3 Subsurface Drainage 20 10.11 Construction Observation and Testing 21 11. REPORT LIMITATIONS 21 APPENDIX Vicinity Map A-1 Site Plan A-2 Boring Logs A-3 Boring Log Notes A-19 Unified Soil Classification System A-22 TABLE OF CONTENTS Atterberg Limit Test Results A-23 Particle Size Distribution Report A-24 Direct Shear Test Results A-39 Typical Foundation Detail A-44 Typical Building Pad Overexcavation A-45 XSTABL Analyses A-46 Result of Liquefaction Analyses A-62 Notes A-64 GEOTECHNICAL ENGINEERING REPORT PROPOSED LA TOURELLE RESIDENTIAL DEVELOPMENT SOUTH 160TH STREET AND 53RD AVENUE SOUTH TUKWILA, WASHINGTON KING COUNTY PARCELS # 5379200005 AND 5379200006 Prepared for Mr. Jawaid Amon by Otto Rosenau & Associates, Inc. August 29, 2007 1. INTRODUCTION This revised report presents the results of our geotechnical engineering services for the proposed residential development in Tukwila, Washington. This revised report includes additional information based on review comments provided in Shannon & Wilson's peer review of the original report dated March 8, 2007. Our original report for this project was titled "Geotechnical Engineering Report, Proposed Tukwila Residential Development, South 160th Street and 53rd Avenue South, Tukwila, Washington, King County Parcel # 5379200005 and 5379200006, ORA Project Number: 06-373, Report 1" and was dated August 15, 2006. 2. PROJECT DESCRIPTION Based on preliminary project information, we understand that the project involves developing two undeveloped Tots to create a gated community of about 15 homes. Based on our review of the most recent proposed grading plans prepared by Barghausen Consulting Engineers, Inc., we understand that the site will be graded close to "balanced" conditions with respect to the planned cuts and fills to avoid surcharging hillside in this area beyond the current conditions. The location of the site is shown on the Vicinity Map on page A-1 of the appendix. 3. SCOPE OF SERVICES The original scope of services included a reconnaissance of the site by the geologist, a review of geologic literature, and witnessing the drilling of five borings (B-1 and B-5) and installation of two ground water monitoring wells at borings B-1 and B-2 in June 2006. Three additional drilling explorations were completed in April 2007. The approximate location of the explorations is shown on the Site Plan on page A-2 of the appendix. The geotechnical engineering services were performed by Otto Rosenau and Associates, Inc. (ORA) to provide the following information: Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 2 of 21 • seismic design considerations including liquefaction potential, • allowable bearing capacity and depth of suitable foundation systems with estimated settlements, • lateral earth pressures and friction coefficients, • slope stability analysis, • influence of groundwater on the development, and • site preparation, earthwork and temporary cut slope recommendations. 4. SITE CHARACTERIZATION We reviewed the "Geologic Map of The Des Moines 7.5' Quadrangle, King County, Washington", 2004 by Booth, Derek B. and Waldron, Howard H. The soils at the project site are predominantly mapped as Deposits of the Vashon Stade of Fraser Age glaciation. These deposits consist of recessional outwash (Qvr), till (Q,t), and recessional lacustrine deposits (Qvri). (Qvr) typically consist of stratified sand and gravel, moderately, well sorted to well sorted; typically deposited in outwash channels. (Qv,) consist of compact diamict containing sub -rounded to well-rounded clasts in massive, silt or sand rich matrix, which is glacially transported and deposited. (Qvr,) consist of very fine grained sand, silt and clay deposited in small lakes during ice recession 5. SURFACE CONDITIONS The site is two parcels which were combined to create an irregular shaped site. The site is bounded on the south and southwest by South 160th Street, along the east side by 53rd Avenue South. The north boundary of the site consists of a Seattle Public Utilities water line easement with South 159th Street immediately to the north of it. The site grades slope downwards to the northeast from approximately Elevation 290 feet near the intersection of 51St Avenue South and South 160th Street to Elevation 196 feet at the northeast property corner the intersection of 53`d Avenue South and South 159th Street. The majority of the elevation change is located at the northeast section of the site (Elevation 196 feet to Elevation 236 feet). The proposed area to be developed is to be located in the eastern two-thirds of the site with access from South 160th Street at the southeast corner of the site. The western third of the site is to remain undeveloped. The site is located on a greater slope that extends upwards to the southwest and downwards towards the 1-5 / 1-405 interchange. There is a fairly level area at the southeast corner of the site near the intersection of South 160th Street and 53rd Avenue South. South 160th Street rises to the west and a concrete retaining wall is located along much of the South 160th Street right-of-way that borders the site. The site grades are quite steep in the far western end of the site that is to remain undeveloped. The Seattle Public Utilities water line easement along the north side of the site contains a delineated wetland and a drainage ditch that drains to the northeast under 53`d Avenue South. Steep slopes border the east side of the site along 53`d Avenue South. Portions of the slopes appear to have been Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29. 2007 Page 3 of 21 built up as an embankment at the approximate location of the historic structures and driveways that used to be present on the site. There are several low-lying areas that have developed into wetlands in the central portion of the site and is identified as Wetland 3 on our site plan. This area was identified as a potential sag pond. Borings B-6 through B-8 were completed near Wetland 3 on our Site Plan to evaluate the subsurface conditions and to identify any subsurface conditions that would support the assertion that this low-lying area is a slide -related feature. The site has three delineated wetlands as identified by Mead, Gilman and Associates in their survey dated January 6, 2006. The site is heavily vegetated with holly, ivy and deciduous trees, a combination of mostly maples up to 50 inches in diameter and alders of various sizes. There is evidence of past development on the site based on presence of fill embankments and linear features that appear to have been driveways. The site has also been used, until recent times, as an uncontrolled dump site. The dumped materials include household waste, wood and metal construction debris, soil, rock, and concrete rubble. Based on our review of historical maps, there appeared to have been several structures (likely residential) present on the site with access from the southeast corner of the site. There is evidence of a past slope instability as evidenced by severely leaning trees on the steep slopes along 53rd Avenue South. We understand that the slopes in this area are to be flattened and reduced substantially in height as part of the site development. A possible prehistoric slide scarp was identified by Shannon & Wilson, Inc. in their map of the Tukwila Interchange revised May 1968. The possible scarp is located on the far west boundary of the site and follows along the south side of South 160th Street adjacent to the south side of the site. Shannon & Wilson's report to the City of Tukwila, November 23, 1992, describes this slide scarp and estimates that displacements of up to 30 to 40 feet have occurred along portions of the 3000 feet estimated length. They indicate that the scarp appears to trend to northwest above the project site and to the southeast towards Slade Way. The presence of several peat deposits in low-lying areas near the slide scarp in nearby off-site areas supports the assertion that the slide has not been activated in historic times. There have been numerous other slope failures identified in the vicinity of the site. One of the largest is a deep-seated slide that occurred just to the southwest of the site in 1960 during the construction of the 1-5 / 1-405 interchange. As a result of this slide, in the 1960's, a network of horizontal drains was installed to relieve artesian pressure within the hillside. 6. SUBSURFACE CONDITIONS We evaluated the subsurface soil and groundwater conditions by completing five borings (B-1 through B-5) at the site using a subcontracted, track -rig mounted, hollow -stem auger, and mud rotary drilling Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 4 of 21 equipment between June 20 and 23, 2006. Borings B-6 through B-8 were completed on April 6, 2007. Borings B-1 through B-3 and boring B-5 were completed using mud rotary drilling techniques. Boring B-4, and borings B-6 through B-8 were completed using hollow -stem auger drilling equipment. The following table summarizes the depths of borings completed for this project. BORING DEPTH BELOW EXISTING GRADE (feet) DRILLING METHOD GROUND SURFACE ELEVATION (feet) WELL INSTALLED (screen depths) B-1 101.5 Mud Rotary 256 Yes, screens from 15 to 20 feet B-2 81.5 Mud Rotary 205 Yes, screens from 18 to 23 feet B-3 66.5 Mud Rotary 228 No B-4 51.5 Hollow Stem Auger 228 No B-5 51.5 Mud Rotary 243 No B-6 51.5 Hollow Stem Auger 232 No B-7 51.5 Hollow Stem Auger 226 No B-8 51.5 Hollow Stem Auger 224 No Please refer to the Site Plan on page A-2 of the appendix for the approximate location of the borings. The details and explanations of our explorations are presented on pages A-3 through A-22 of the appendix. Similar soil conditions were observed at each boring location with an upper zone of loose to dense sand with varying silt content ranging from 21 to 46 feet in thickness over stiff to hard sandy silt, silt and lean clay. We did not observe indications of a slide plane in any of our explorations as might be evidenced by slickensides or a highly disturbed zone. Borings B-7 through B-8 were completed to evaluate the subsurface conditions at a possible sag pond feature identified as Wetland 3 in our Site Plan. We performed nearly continuous sampling in the upper 18 to 20 feet at each location to try and identify any past failure planes, but did not observe any evidence of such a feature. The remainder of the sampling was performed at about 5 -foot intervals. Based on our observations of the subsurface conditions encountered at borings B-7 and B-8, it is our opinion that Wetland 3 is not a slide -related feature. However, it is not clear how this feature was created. Groundwater was observed during drilling at most of our explorations. The mud rotary drilling technique makes direct observation of water levels in borings difficult. A 2 -inch diameter PVC standpipe piezometer was installed at borings B-1 and B-2 in the upper sandy soils overlying the stiff to Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Matenals Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 5 of 21 hard silts. Groundwater was measured at B-1 and B-2 at depths of about 2.5 feet and 17.5 feet below the existing adjacent site grade on June 6, 2007. A groundwater measurement of 18 feet below the existing site grade was recorded 24 hours after completion of the well installation at B-1. We believe that this may have been artificially low because groundwater may not have had enough time to enter the well at the time the reading was taken. We believe that the much higher reading taken in June 2007 is more representative of actual conditions in the vicinity of B-1. The groundwater levels at the site will likely vary with season and precipitation. We observed standing water in close proximity to the location of boring B-1. 7. LABORATORY TESTING We performed a wide range of laboratory tests on representative soil samples at the ORA soils laboratory. The tests performed include the following: • Moisture content determinations. Results are presented on the boring logs. • Atterberg Limit Determinations (ASTM D 4318). Results are presented on pages A-23 of the appendix. • Grain size analyses (ASTM D 422). Results are presented on pages A-24 through A-38 of the appendix. • Direct shear test results (ASTM D 3080). Results are presented on pages A-39 through A-43 of the appendix. Direct shear tests were performed by HWA Geosciences in Lynnwood, Washington. 8. REVIEW OF LITERATURE We reviewed several geotechnical reports that were completed in the vicinity of the project site. These included the following projects: • Hillcrest Residential Development located upslope and south of the project site. Cascade Geotechnical Inc. completed a geotechnical investigation and a series of subsequent responses to the City of Tukwila's review comments. Shannon & Wilson, Inc. provided geotechnical review services for the City of Tukwila. The correspondence that we reviewed is dated between 1992 and 1993. The location of the Hillcrest Residential Development is very close to the scarp of the large landslides that occurred in the 1960s during the construction of the 1-5 / 1-405 Interchange. The landslide was remediated partially by installing horizontal drains on WSDOT right-of-way. It appears that the horizontal drains have not been maintained by WSDOT and that several consultants have indicated that the factor of safety against slope failure at this site will continue to decrease as long as maintenance is not performed on the horizontal drains. • Five Rivers Development located downslope to the northeast of the project site. LSI Adapt, Inc. completed a geotechnical investigation and presented the results of their investigation in "Geotechnical Engineering Report, Five Rivers Preliminary Plat, 53rd Avenue S. and S. 159'h Street, Tukwila, Washington" dated August 2001. LSI Adapt, Inc. prepared several subsequent engineering design supplements to address slope stability issues that were not initially Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29. 2007 Page 6 of 21 addressed. Shannon & Wilson, Inc. provided geotechnical review services for the City of Tukwila on this project and concurred that LSI Adapt Inc.'s design approach satisfies the City of Tukwila's requirement for development in an environmentally -sensitive area. • 53rd Avenue South and South 160th Street Improvements project located along the south border of the site and extending to the west. Landau Associates, Inc. completed a geotechnical investigation for this project and presented their recommendations in "Geotechnical Study, 53rd Avenue South and South 160th Street Improvements, Tukwila, Washington" dated March 5, 1991. We also reviewed the project plans prepared by the City of Tukwila Public Works. We were able to determine that the cast -in-place concrete retaining wall that is present along South 160th Street is a cantilevered retaining wall and is supported on conventional spread footings. 9. DISCUSSION The recommendations presented in this report are based on our understanding of the project as presented in the Project Description Section and on the assumption that the subsurface conditions are as assumed herein. Project conditions, regarding type and location of structures and foundation loads can change, and subsurface conditions are not always similar to those encountered during the subsurface exploration. Therefore, if discrepancies are noticed, the geotechnical engineer must be contacted for review and for possible revision of the recommendations. 10. CONCLUSIONS AND RECOMMENDATIONS 10.1 GENERAL The engineering recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical engineering practices in the area. The recommendations are based on our understanding of the geology of the area and on experience with similar projects. It is our opinion that it is possible to develop the site, provided that it is completed in accordance with the recommendations presented in this report. The primary concern for development in environmentally sensitive areas such as the project site is to not increase the risk of future slope instability. The primary ways that the risk of future slope instability can be reduced or minimized is to incorporate the following measures into the development of the project site. • Careful grading to minimize fills at the upland areas of the site to avoid increasing potential driving forces that could lead to slope instability. Overall, the project should be a net export or balance site. • This site is not suitable for on-site infiltration of stormwater runoff from impermeable surfaces such as roadways, paved surfaces and roofs. As a result, large detention facilities will likely be required. All piping and detention facilities should be designed to reduce exfiltration into the adjacent soils. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 7 of 21 • Significant overexcavations will be required to remove unsuitable organic soils and potentially liquefiable soils at most of the building lots. Alternatively, deep foundation support may be implemented to mitigate the presence of unsuitable soils. 10.2 SEISMIC CONSIDERATIONS The seismic design of structures in the City of Tukwila is governed by the requirements of the 2003 International Building Code (IBC). The IBC requires that the site be classified into a site class. Based on the results of the soil exploration completed at the project site, it is our opinion that the observed conditions most closely meet the described conditions of Site Class D (IBC Table 1615.1.1). Site specific criteria can be obtained from maps in the IBC (Figures 1615(1) and 1615(2)) for short period (SS) and 1 -second -period (S1) spectral accelerations. The values for Ss and S1 are spectral response accelerations (SRA) for a maximum considered earthquake event with about a 2,500 year return period, or a 2% probability of exceedance (PE) in 50 years. Values for SS and S1 are also available from the United States Geological Survey (USGS) National Seismic Hazard Mapping Project website. The values recommended for use in this report were obtained from the USGS website by inputting latitude and longitude for the project site (N 47.45943°, W 122.26734°). The 1996 data set from the USGS website was used for consistency with the relevant figures in the 2003 IBC. The following table presents recommended values from the 2003 IBC for seismic design: 2003 International Building Code (IBC) Seismic Design Values (2% PE in 50 years) Mapped max. earthquake SRA at short periods, Ss. % g 135.1 Mapped max. earthquake SRA at 1 -second period, Sl, % g 46.5 Site Class Definition (Table 1615.1.1) D Site Coefficient Fa (Table1615.1.2(1)) 1.0 Site Coefficient F, (Table1615.1.2(2)) 1.5 Max. considered earthquake SRA for short periods, SMS 135.1 Max. considered earthquake SRA for 1 -second periods, SM1 69.8 Design SRA at short periods, SDS 90.1 Design SRA at 1 -second period, SD1 46.5 Design Peak Ground Acceleration (PGA, PGA = SDS x 0.4, for period, T = 0) , % g 36.0 Liquefaction may be defined as the sudden loss of strength of soil as the soil is subjected to a rapid cyclic loading, such as during an earthquake. The mechanism that allows this to occur is that excess pore water pressures are generated between the soil particles. This excess pore water pressure Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 8 of 21 reduces the frictional contact between the soil particles and reduces the shear strength of the soil. If the earthquake is of Targe magnitude and duration, the soil can begin to behave more like a liquid than solid and "liquefy". In order for liquefaction to occur, several conditions must typically be present. These include the following: • Saturated soil. • Fine to medium sand matrix containing less than about 10 percent fines (soil that can pass a No. 200 sieve). • Very loose to medium dense soil conditions. This is usually defined as soils that have N - values of 15 or less. Based on the results of our explorations and our observation of the soil and groundwater conditions at the site, it is our opinion that the potential for liquefaction at the site is medium to high along the western portions of the site to be developed and low to medium along the eastern portions of the site to be developed. We completed a liquefaction analysis using the subsurface information and related laboratory testing collected from borings B-1 and B-2. The liquefaction analysis was completed in general accordance with "Seed's Simplified Procedure" with the suggested modifications proposed by Seed, Youd, et al. in "Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshop on Evaluation of Liquefaction Resistance of Soils" (Journal of Geotechnical and Geoenvironmental Engineering — October 2001). The analyses were completed assuming design peak ground acceleration equal to 36% g. The silty soils with fines content greater than 50% are considered to be non -liquefiable. The results of the analyses are presented on pages A-61 and A-62 of the appendix. Similarly, we estimated liquefaction -induced settlement using the subsurface information and related laboratory testing collected from borings B-1 and B-2. The Tokimatsu-Seed approach as described in "Geotechnical Earthquake Engineering" (Kramer, 1996) was used to evaluate liquefaction -induced settlement. Estimates for liquefaction -induced settlement are typically considered to provide an order of magnitude estimate of the possible settlement that may occur. The results of our analyses indicate that liquefaction -induced settlement on the order of 4.5 inches may occur in the pre -developed condition. Provided that the recommendations of this report are followed, the liquefaction -induced settlement at the future building pads should be Tess than an inch. The most recent, significant, seismic event was the Nisqually earthquake which occurred on February 28, 2001 with a Richter magnitude of 6.8 and a peak ground accelerations in the Seattle area approaching 20% g. Little to no slope instability was reported in the Seattle area as a result of the earthquake. Significant structural damage did occur to buildings where the existing subsurface conditions tended to amplify the ground motion, such as in the area south of downtown Seattle, where Targe areas of hydraulically -placed fill are present over former tidal mudflats. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 9 of 21 10.3 FOUNDATIONS We anticipate that the majority of the proposed residential structures and the detention vault may be supported on conventional spread footings or a thickened edge slab foundation system provided that the underlying unsuitable organic soils and potentially -liquefiable soils are removed and replaced with structural fill. We recommend that overexcavations, where needed, be completed across the entire building pad to the underlying stiff to very stiff silts or suitable sandy soils. Alternatively, the structures may be supported on a pile -supported foundation. The following table is a summary of the anticipated foundation support methods at each building lot. This table is based on the currently -available information but must be confirmed at the time of site clearing by an ORA representative to determine the most appropriate foundation system. LOT NUMBERS LIKELY FOUNDATION SYSTEM NOTES 1 - 4 Shallow foundations Will bear on new structural fill — minimal overexcavations anticipated. 5 - 8 Shallow foundations Will likely need substantial overexcavations (up to 14 feet below the existing site grade) prior to placement of structural fill, or a deep foundation system. 9-10 Shallow foundations Will likely need moderate overexcavations (less than 4 feet below the existing site grade) prior to placement of structural fill, or a deep foundation system 11 Shallow foundations Will likely need significant temporary shoring (up to 12 feet high) along the south and west sides of structure to be developed without encroaching on adjacent wetland. Will likely need moderate overexcavations (up to 4 feet below the existing site grade), or a deep foundation system if required overexcavation depths are greater than about 4 feet. 12 - 15 Shallow foundations Will likely need moderate overexcavations (up to 4 feet below the existing site grade) to bear on native stiff silt prior to placement of structural fill, or a deep foundation system if required overexcavation depths are greater than about 4 feet. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 10 of 21 10.3.1 Shallow Foundations: Following the satisfactory preparation of the building pad subgrade as recommended in the "Earthwork" section of this report, all shallow foundation elements for this project should be supported by at least a 2 -foot thick zone of structural fill as measured from the design bottom of the foundation element. The overexcavation should extend laterally a distance at least equal to the overexcavation depth. Please refer to the Typical Foundation Detail on page A-44 of the appendix and the Typical Building Pad Detail on page A-45 of the appendix for a summary of these recommendations. We recommend that the following allowable bearing capacities be used for the design of conventional spread footings: Foundation bearing on a minimum 2 -foot thick zone of structural fill that extends to the native, re -compacted sandy soil or stiff silt: 2,000 psf The allowable bearing capacities may be increased by one-third for wind and seismic loads. If the recommendations in this report are followed, we estimate that maximum post -construction settlements will be less than three-quarters (3/4) of an inch and differential settlements will be less than one-half (1/2) of an inch between comparably loaded column footings or along a 25 -foot long section of continuous wall footing. We recommend that the minimum width of continuous footings be 1.5 feet and that the minimum size of column footings be 2 -foot by 2 -foot. All foundation elements shall be embedded at least 18 inches below the lowest adjacent finished grade for frost protection and to meet the minimum code requirements as presented in Section 1805 — Footings and Foundations of the 2003 International Building Code (IBC). Passive resistance should be evaluated using an equivalent fluid pressure of 250 pounds per cubic foot (pcf) where grade beams are cast on structural fill or dense native soils and backfilled on both sides with structural fill compacted to at least 95 percent of maximum dry density (MDD). This value of passive pressure includes a factor of safety of 1.5. An ultimate coefficient of friction between footings and bearing soils of 0.35 may be used to resist lateral foundation loads. If passive earth pressures are used in conjunction with base friction to resist lateral loads, reduce the ultimate coefficient of friction to 0.30. A factor of safety of 1.2 should be applied to these values. 10.3.2 Deep Foundations: It is likely that several of the residential structures will need to be supported on deep foundation elements. 3-, 4-, or 6 -inch diameter steel pipe piles driven to refusal would be suitable for use to provide downward axial support for the future residences. Small -diameter Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29. 2007 Page 11 of 21 steel pipe piles should not be relied upon to provide uplift or lateral resistance. If pile -supported foundations are being used to avoid excessive excavation of unsuitable materials beneath a future structure, we recommend that the floors on the lowest levels be designed as structural slabs that carry the imposed Toads to the pile -supported foundation without relying on the underlying soils for structural support. The pipe piles should consist of galvanized, Schedule 40, Grade A53 steel pipe. The piles should be driven by an experienced contractor, using a hydraulic hammer weighing between 850 and 3,000 pounds depending on the pile size to be installed. ORA should be contacted once a pile driving contractor is selected to provide appropriate driving refusal criteria for the equipment being used. In general, the pipe piles must be driven through the upper loose to medium dense sandy layers and shall be embedded at least 5 feet into the stiff to hard clay layers, or the depth required to achieve refusal, whichever is greater. Pipe piles driven to refusal as described will have the following allowable downward pile capacities: Pile Diameter (inches) Allowable Downward Pile Capacity (tons) 3 6 4 10 6 15 Pile load testing will be required for this project to verify that the design loads are appropriate for the soil conditions at the site. A minimum of 5% of the total number of piles installed should be load tested for this project. The pile load tests should be monitored by an ORA representative. If the pile load test program indicates that higher loads are achievable on the project than presented above, ORA can provide revised recommendations for design pile capacities with an appropriate factor of safety. If the recommendations in this report are followed, we estimate that maximum post -construction settlements will be less than three-quarters (3/4) of an inch and differential settlements will be less than one-half (1/2) of an inch over a 50 -foot length of continuous grade beam or pile cap. Grade beams, pile caps, and any retaining walls should be reinforced to reduce the potential for distress caused by differential foundation movements. A qualified engineer should determine the size, quantity, and location of reinforcement. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Matenals Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 12 of 21 10.4 BELOW -GRADE WALLS AND RETAINING WALLS Lateral earth pressures for design of below—grade walls, retaining walls, and foundation elements with level backfill and with no hydrostatic pressures or surcharge loads, may be calculated using the following equivalent fluid pressures: Active (unrestrained and drained conditions): Compacted granular soils 36 psf/ft. Active (restrained and drained conditions): Compacted granular soils 57 psf/ft. Passive: Continuous footings Column footings 250 psf/ft. 250 psf/ft. The geotechnical engineer should be contacted to determine appropriate lateral earth pressures for situations not described above. Seismic earth pressures were estimated using the Mononobe-Okabe pseudo -static method. We recommend that seismic earth pressures be estimated using a rectangular pressure distribution equal to 10H, where H is the height of the retained soil behind the wall. A total soil unit -weight of 125 pounds per cubic foot should be used in design of any permanent below - grade wall or retaining structures. 10.5 SLABS -ON -GRADE Based on our understanding of the project construction, we anticipate that the only slab -on -grade will be in the garage and we expect that only small amounts of fill will be required to raise the grades for floor slab support. Slabs -on grade should be at least 4 inches in thickness. The slab -on -grade should be supported on a minimum 4 -inch -thick, free -draining, gravel base as described in the Structural Fill section of this report. A vapor retarder such as 6 -mil polyethylene sheeting shall be included beneath the slab to minimize transmission of moisture through the concrete floor. A minimum, two-inch thick layer of clean sand with less than 3 percent fines may be placed on top of the polyethylene sheeting to protect the sheeting and to enhance the curing of the concrete slabs. The sand must not be saturated at the time of concrete placement to provide a drainage path for bleed water from the curing concrete. A more robust vapor barrier system may be required for the residences to be located in the western portion of the development where ground water levels are significantly higher. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29. 2007 Page 13 of 21 10.6 EARTHWORK The recommendations presented in this report are predicated on fulfillment of the following earthwork recommendations. 10.6.1 Site Clearing: Any existing vegetation, loose soil, and any other deleterious materials including asphalt pavements and old foundation elements household shall be removed from the future building area prior to construction. After site clearing and stripping, the exposed surfaces should be graded to allow good surface drainage during construction. An ORA representative must be on site during site clearing operations to verify if adequate stripping is completed and whether a deep foundation system may be required over a shallow foundation system. The near -surface soils at the site are moisture -sensitive and easily disturbed during periods of wet weather. A gravel or quarry spall work surface may be built to protect the underlying native soils and to reduce the amount of soil disturbance during periods of wet weather. Wetland deposits including peat and a substantial amount of organic material and wood debris were encountered near the proposed cul-de-sac at depths of up to 14 feet below the existing site grades as observed in boring B-8, which is close to the proposed location of the future stormwater detention vault. Organic material and wood debris are prone to long-term settlement as they decay. In addition, organic silts are highly compressible. We strongly recommend that the organic silts and wood debris be fully - removed from beneath any future site improvements, such as buildings, roadways, sidewalks, stormwater detention vault, etc., to reduce the risk of post -construction settlement. All overexcavations should be backfilled with structural fill. 10.6.2 Structural Fill: In general, the native soils on site that consist of sand with silt (SP -SM) or silty sand (SM) should only be used as structural fill during drier periods, provided that the soil is moisture - conditioned to within three (3) percent of optimum moisture. All fill and backfill materials should be placed in relatively horizontal loose lifts, not exceeding 10 inches in thickness, and compacted to at least 95 percent of the maximum dry density (MDD) as determined by the modified Proctor test (ASTM D1557). If manually -operated equipment such as a jumping jack compactor is used, the thickness of each loose lift should be no greater than 6 inches. Light vibratory plate compactors are not suitable for the compaction of structural fill. Soils consisting of clay, silt, peat, or containing deleterious matter are generally not suitable for use as structural fill. Structural fill material should be approved by ORA prior to use. The following table summarizes our recommendations and compaction requirements in reference to the 2006 edition of Washington State Department of Transportation's (WSDOT) Standard Specifications for Road, Bridge, and Municipal Construction for various types of aggregates. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 14 of 21 Intended Use Specification Compaction Requirements Structural fill for overexcavation backfill below foundation elements 2- to 4 -inch quarry spalls, or washed crushed rock with a typical particle size between 1.25 and 2 inches and Tess than 5 percent fines Quarry spalls or clean crushed rock must be placed in lifts no greater than 12 inches in thickness, with each lift thoroughly compacted with a vibratory roller, or hoepack mounted on an excavator. Structural fill below pavements or sidewalks Suitable native soil, Gravel Borrow (WSDOT 9-03.14(1), Select Borrow (WSDOT 9-03.14(2), Crushed Surfacing Base Course (WSDOT 9- 03.9(3) Fill placed at depths greater than 2 feet below finish subgrade elevation must be compacted to 90 percent of MDD. Fill placed at depths within 2 feet of finish subgrade elevation must be compacted to 95 percent of MDD. Free -draining wall drainage material behind below -grade walls and retaining walls Gravel Backfill for Walls (WSDOT 9- 03.12(2), Gravel Backfill for Drains (WSDOT 9-03.12(4) Fill placed within 5 feet of below - grade walls or retaining walls shall be compacted with manually -operated compaction equipment. Fill placed at depths greater than 2 feet below finish subgrade elevation compacted to 90 percent of MDD. Fill placed at depths within 2 feet of finish subgrade elevation must be compacted to 95 percent of MDD, if the area will be supporting pavements or roadway. Capillary break material below slabs Pea gravel with a maximum particle size of about 3/8" and less than 3 percent fines. Washed, crushed rock with a maximum particle size of about 5/8" Washed, crushed rock shall be mechanically compacted prior to placing concrete. Structural fill to be compacted to 95 percent of MDD should be moisture -conditioned to within three (3) percent of optimum moisture. Structural fill to be compacted to 90 percent of MDD should be moisture - conditioned to within six (6) percent of optimum moisture content. Placement of frozen soils or placement of soils on frozen ground should not be attempted. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 15 of 21 10.7 SITE SLOPES 10.7.1 Permanent Slopes: We recommend that permanent cut slopes for this project be inclined no steeper than 2H:1V (horizontal to vertical). However, along South 160th Street we recommend that the permanent fill slopes be inclined no steeper than 2.5H:1V. The slopes along South 160th Street may be temporarily cut at an inclination during construction and then built up as a fill slope to a 2.5H:1V final inclination in accordance with the embankment construction methods described in this section. Permanent fill slopes may be inclined up to 2H:1V if built with select granular materials (sand and gravel) that contains less than 10 percent fines and essentially free of any deleterious debris. Any proposed embankment fill must be approved by the geotechnical engineer before placement. All embankment fill must be compacted to at least 95 percent of the maximum dry density. Fill placed at depths greater than 2 feet below final grade shall be placed in loose lifts no greater than 10 inches in thickness. Fill placed at depths within 2 feet of finished grade shall be placed in loose lifts no greater than 6 inches. All fill embankments built on hillsides shall be built by benching into the original ground surface. Each bench shall penetrate in to the hillside at least 5 feet and shall not be greater than 5 feet in height. The horizontal portion of each bench shall be slightly sloped to drain outwards. Achieving the required compaction at the face of embankment slopes is difficult. We recommend that the embankment fills be temporarily over -steepened during construction and then cut to the final slope inclination at the end of embankment fill placement operations to ensure that the fill at the outside face of the embankment is adequately compacted. Alternatively, a 4 -foot wide strip of geogrid such as Mirafi 2XT, Tensar UX1000, or an approved equivalent may be used to stabilize the slope face. The geogrids should be installed at the slope face at 2 foot intervals for the full height of the embankment. Geogrids should be installed in a taut condition using pins as required, and fill should be carefully spread over it to prevent the creation of wrinkles. Geogrids should be installed in accordance with the manufacturer's recommendations. If seepage is observed at the excavation face during construction, drainage shall be provided at the location of the seepage and shall extend at least 5 feet laterally to either side of the seepage. The drainage shall consist of a rock -filled chimney drain at least 12 inches in width built against the excavation face. The rock shall consist of "Gravel Backfill for Drains" (WSDOT 9-03.12(4). A geotextile fabric shall surround the drain rock and 4 -inch minimum diameter, PVC perforated collector pipe (SDR 35 or Schedule 40) will be placed at the base of the rock -filled chimney drain. A 4 -inch minimum diameter, PVC tightline pipe (SDR 35 or Schedule 40) will direct the collected water to an appropriate discharge point at the base of the slope in accordance with City of Tukwila requirements. The geotextile used shall consist to surround the chimney drain and perforated collector pipe shall consist of Mirafi 140N, Amoco 4545, or other approved equivalent. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 16 of 21 Alternatively, a drainage panel such as Mirafi G200N, or other approved equivalent may be placed at the location of the observed seepage at the excavation face and shall extend at least 5 feet laterally to either side of the seepage. The collected water at the base of the panel may be directed to a gravel - filled drain with a 4 -inch minimum diameter, PVC perforated collector pipe (SDR 35 or Schedule 40) fully surrounded with a geotextile fabric, such as Mirafi 140N, Amoco 4545, or other approved equivalent. A 4 -inch minimum diameter, PVC tightline pipe (SDR 35 or Schedule 40) will direct the collected water to an appropriate discharge point at the base of the slope in accordance with City of Tukwila requirements. Upon completion of embankment construction, the exposed soil surfaces shall be hydroseeded. An erosion control blanket such as Western Excelsior Excel SS -2 Regular, or other approved equivalent, should then be installed over the hydroseeded surface in accordance with the manufacturer's recommendations. 10.7.2 Temporary Slopes: We anticipate that temporary cut slopes will be used at portions of the site to complete roadway and utility trench excavations. We recommend that the inclination of the temporary cut slopes be no greater than 1.5H:1V in the upper loose, sandy soils. Flatter slope inclinations will be required if groundwater seepage is encountered in excavations. All temporary cut slopes and excavations must comply with the provisions of Washington Administrative Code (WAC) Chapter 296-155, Part N, "Excavation, Trenching and Shoring." The contractor performing the work has the primary responsibility for protection of workers and adjacent improvements. However, we recommend that the contractor submit a work plan and excavation support plan for our review prior to beginning work on the site. 10.7.3 Setbacks and Buffers: Provided that the project is developed in accordance with the most - recent grading plan prepared by Barghausen Consulting Engineers dated July, 17, 2007 and in accordance with the recommendations of this report, we do not foresee the need for steep slope setbacks or buffers on this project. 10.8 SLOPE STABILITY We performed a visual reconnaissance of the slopes to evaluate the current slope stability conditions at the site. We observed indications of recent slope instability at the steep slope areas along 53rd Avenue South as evidenced by severely leaning trees. However, many of the trees are covered with English ivy, which can adversely affect the health of the trees. Areas with near -surface wet soil conditions are present along South 160th Street, which is possibly similar to a sag pond feature that is common in areas where past slope instability has occurred. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No: 06-373 August 29, 2007 Page 17 of 21 ORA performed a computer-based slope stability analysis using the XSTABL Version 5.206. XSTABL uses the Bishop Method of Slices to estimate factors of safety and forces. We evaluated several cases for the pre -developed and developed conditions at the site at three locations described as Sections A- A' through C -C'. The pre -developed condition assumes current site grades and no subsurface drainage. The post -developed condition assumes the current site grades are modified based on Barghausen Consulting Engineers' most recent grading plan for the project. No assumption was made for the drawing down of water across the site. Two loading conditions were modeled for the pre - developed and developed conditions. 1. Static Loading Conditions — No earthquake forces applied, existing site conditions. 2. Seismic Loading Conditions — 0.2 g peak ground acceleration, modeled as a horizontal coefficient, ah of 0.1 in the pseudo -static analysis. A third condition was evaluated for Section B -B' to evaluate slope stability after the onset of liquefaction in the developed condition. The existing slope was modeled assuming the presence of two soil layers — the upper loose to medium dense sand layer and the stiff to hard silt and lean clay layer. The developed condition was modeled using two to four different soil layers. The extra soil layers in the developed condition are related to a zone of structural fill used to build up a fill slope along South 160th Street and a zone of liquefied soil following a large seismic event. The following soil parameters were used and are based on direct shear test results completed for this project: Soil Unit Description Assumed Unit Weight, y, (pcf) Angle of Internal Friction, 4), (degrees) Cohesion (psf) Upper Sandy Soil Unit (SP -SM and SM) 105 pcf dry 28 100 115 pcf saturated Lower Silt and Clay Unit (ML and CL) 116 pcf dry 28 200 to 1000 120 pcf saturated Structural Fill 125 pcf dry 34 50 130 pcf saturated Liquefied Sandy Soil Unit (SP -SM and SM) 105 pcf dry 0 800 115 pcf saturated The above listed soil parameters are reduced from those obtained in the laboratory testing completed for this project. In addition, the soil strength parameters used in our revised slope stability model are less than those used in a recent USGS report titled "Shallow -Landslide Hazard Map of Seattle, Washington: U. S. Geological Survey Open -File Report 2006-1139" by Edwin Harp and John A. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 18 of 21 Michael of the U. S. Geological Survey in Golden, Colorado, and William T. Laprade of Shannon and Wilson, Inc. in Seattle, Washington. The report was published in 2006. The cohesion values used to model the lower silt and clay unit range from 200 to 1000 psf and were selected to model possible slope failures surfaces that pass through the upper sandy soil units and not through the lower silt and clay layers. The residual strength of the liquefied sand layer was based on methods presented in "Geotechnical Earthquake Engineering" (Kramer, 1996). A graphical presentation of the results of our slope stability analysis are presented on pages A-46 through A-60 of the appendix. A summary of the results under the various loading conditions is presented in the following table: Section Site Condition Loading Condition Estimated Minimum Factor of Safety Recommended Minimum Factor of Safety A -A' Pre -development Static 1.6 1.5 A -A' Pre -development Seismic 0.2 g 1.3 1.1 A -A' Developed Static 1.6 1.5 A -A' Developed Seismic 0.2 g 1.3 1.1 B -B' Pre -development Static 1.5 1.5 B -B' Pre -development Seismic 0.2 g 1.3 1.1 B -B' Developed - Upper Slope Area Static 1.7 1.5 B -B' Developed - Upper Slope Area Seismic 0.2 g 1.3 1.1 B -B' Developed - Lower Slope Area Static 1.5 1.5 B -B' Developed - Lower Slope Area Seismic 0.2 g 1.2 1.1 B -B' Developed - Liquefied Upper Slope Area Seismic 0.2 g 1.7 1.1 B -B' Developed - Liquefied Lower Slope Area Seismic 0.2 g 1.1 1.1 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 19 of 21 Section Site Condition Loading Condition Estimated Minimum Factor of Safety Recommended Minimum Factor of Safety C -C' Pre -development Static 1.2 1.5 C -C' Pre -development Seismic 0.2 g 1.0 1.1 C -C' Developed Static 1.7 1.5 C -C' Developed Seismic 0.2 g 1.3 1.1 A factor of safety of 1 indicates that the forces that cause instability are in equilibrium with the forces that are resisting instability. A factor of safety of Tess than 1 indicates that the forces that cause instability are greater than the forces resisting instability and that the slope will fail. Conversely, factors of safety greater than 1 indicates that the forces resisting instability are greater than those causing instability and that the slope is stable. Based on the results of the slope stability analyses, we anticipate that the site is stable under static and seismic loading conditions (peak ground acceleration = 0.2g). The primary failure method anticipated by the slope stability analysis are failures through the upper sand layer. The most vulnerable slopes were the slopes along 53rd Avenue South, which our analyses demonstrate should become more stable with the proposed grading. Also, the off-site slopes along South 159th Street appear to be vulnerable and are not to be addressed as part of this project. It can be expected that seismic events with larger peak ground accelerations, and longer recurrence intervals, will result in a lower estimated factor of safety for slopes at the site. In order to reduce the risk of slope instability after construction, we recommend the following practices: • All roof drains, footing drains, and other drains should be gathered and tightlined to a discharge location approved by City of Tukwila. • No on-site infiltration of stormwater runoff should be used. • Any accumulations of yard waste and biodegradable construction waste (cut branches, lawn clippings, and lumber) that are present should be removed from the slope face and adjacent areas. • Yard waste should not be placed on any of the existing slopes. • Vegetative cover should be continuously maintained on overall steep slope areas to reduce erosion potential and to stabilize surficial soils. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 20 of 21 10.9 EROSION AND SEDIMENTATION CONTROL The migration of sediments from the site must be installed and controlled in accordance with City of Tukwila requirements. We recommend that the following minimum erosion control measures be employed at the site: • Provide silt fencing around the construction area to delineate the construction limits. No construction or soil disturbance should take place outside of the construction limits. • Stockpiled soil at the site should be kept to a minimum. Any stockpiled soils should be covered with carefully secured plastic sheeting. Additional erosion control measures may be required as construction progresses. 10.10 DRAINAGE 10.10.1 Construction Dewatering: Ground water seepage will likely be encountered during construction. However, we anticipate that dewatering could be satisfactorily completed by routing water through ditches to a low spot or sump in the excavation. Water collected in the excavation should be removed as soon as possible and should be discharged to a location approved by the City of Tukwila and in accordance with City of Tukwila requirements. 10.10.2 Surface Drainage: Good surface drainage is an integral part of the performance of earth - supported structures such as foundations, retaining walls, and pavements. Therefore, construction grades and final site grades should be designed to prevent water from entering the foundations or gravel drains behind any retaining walls, or from ponding on or next to pavements. Where pavement does not immediately abut structures, the ground surface should be sloped with an outfall of at least three (3) percent for a minimum distance of five (5) feet from exterior footings. These slopes should be capped with relatively impervious soils to prevent infiltration of water into the foundation soils. Runoff water should be collected from all impervious surfaces on the project and should be routed away from steep slope area on the west side of the site to a discharge location approved by the City of Tukwila. We strongly recommend that no on-site infiltration of runoff water be performed to minimize the flow of additional groundwater and to help minimize the risk of future slope instability. 10.10.3 Subsurface Drainage: We recommend that subsurface drainage be provided around each structure. The foundation drains for the residential structures should be built in accordance with the Typical Foundation Detail shown on page A-44 of the appendix. The foundation drains should be sloped to drain to a suitable discharge point. Roof downspout drains and footing drains must be kept separate. Below -slab drainage may need to be considered if high groundwater levels will appear to be problematic. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Residential Development ORA Project No.: 06-373 August 29, 2007 Page 21 of 21 10.11 CONSTRUCTION OBSERVATION AND TESTING The recommendations presented in this report rely on adequate observation and testing of construction materials and procedures by the geotechnical engineer or his qualified representative. At a minimum, the testing program should include: • Observation and review of site preparation, structural fill placement, drainage installation, pile driving and pile Toad testing to evaluate whether actual conditions are consistent with those encountered during exploration and used for design. 11. REPORT LIMITATIONS The recommendations presented in this report are for the exclusive use of Mr. Jawaid Amon and other members of the design team for the proposed La Tourelle residential development at South 160th Street and 53rd Avenue South in Tukwila, Washington (King County Parcels # 5379200005 and 5379200006). The recommendations are based on the readily -available geologic literature and eight borings completed on June 2006 and April 2007. The recommendations of this report are not transferable to any other site. If there are any revisions to the plans or if deviations from the subsurface conditions noted in this report are encountered during construction, Otto Rosenau & Associates, Inc. (ORA) should be notified immediately to determine whether changes to the design recommendations are required. oOo x 0 z w a. 0. Q Note: The location of all features shown is approximate. Reference: Des Moines, Washington USGS Quadrangle and portions of adjacent quadrangles, ALL TOPO MAPS: Washington. VICINITY MAP Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 30, 2007 For: Mr. Jawaid Amon OTTO ROSENAU & ASSOCIATES, INC. ORA Project Number: 06-373 A-1 s0 — 0 9 000 � N \ \ i__� \\ .. \ - .. \\'WETLAND 11. , .v 0 \ iso B-5 \ r_- 0 1 JWETLAND 2T \1 / Curb line S. 1159TH ST. Property line 1A _ 190 3 Of MO -\- ✓ III Mil 0 B-4 `'so \°'` N•• \ 0 0 B-2 ti B-6 B-1 415 `c ',WETLAND 31 _\ B-8 \ LEGEND O B-1 through B-5 O B-6 through B-8 Borings completed by ORA in June 2006 Borings completed by ORA in April 2007 CO 0 I 1 4 0 B-3 • • • Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. Scale: 1" = 70 feet SITE PLAN Project Name: La Tourelle Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: September 5, 2007 For: Mr. Jawaid Amon OTTO ROSENAU & ASSOCIATES, INC. ORA Project Number: 06-373 A-2 1' - 40' 0 20 40 80 PRELIMINARY PLAT MAP FOR LA TOURELLE A PORTON OF THE NW 1/4 OF SECTION 26, TOWNSHIP 23 N., RANGE 4 E, W.M. TUKWILA, WASHINGTON SOUTH 159TH STREET 1 L`rJJ` VJ`. 2`1 � J C✓` .0''51004 547 ✓4 PROPOSED ROW DEO7CA 749 5F LEGAL DESCRIPTION BE0INHNNG AT A PORT ON 101 NORTH ONE OF SECTION 26. 100465HIP 23 NORTH. RANGE 4 EAST 643AMERE MERCIAN, IN KING COUNTY, w45HNGT09. A INSTANT SOUTH 85)113' EAST 23.86 FIE2 TROY THE NORTHWEST CORNER OF SAID SECTION THENCE CONTINLR40 SOUTH 69'3123" EAST 601.67 FEET TO THE WEST 188 D1 5300 AVENUE SOUTH; THENCE SOUTH 21'10'20" EAST 26737 FEET; THENCE SOWN 12020' UST 162.95 1EE1 TO THE NOR1HE457ERL4 YARO7, OF SOu1H 16010 STREET: TIERCE ALONG THE SAID NORTHEASTERLY MARLIN NORTH 76'07'40 WE51 209 97 FEET, THENCE NORTH 705505- WEST 305.05 FEET. THENCE NORTH 4025'10" WEST 170.49 FEET, THENCE NORTH 572000" WEST 254.38 FEET 10 THE POINT OF BEGINNING (ALSO KNOWN AS A PORTON OE LOT 1. BLOCK 1, MC TACKER HEIGHTS 5575209 N0. 1 ACCORDING TO 114[ UNRECORDED PUT THEREOF): RELOCATE EX5T810 •. , 8U5 5HEL710''' 10 S5OR 151.11 a PROPOSED Cr `' l ROw DE01121 ON tea\ y EXCEPT THAT PORTION BEGINNING Al THE SOUTHEAST CORNER OF THE ABODE DESCRIBED TRACT. FENCE NORTH ALONG THE EAST LINE OF SAO DESCRIBED TRACT 104.30 FEET. THENCE SOUTHWESTERLY ON A 51RUGNT LINE 100 FEE1, YORE OR LESS, TO A PORT ON 1 W SOUTHERLY LINE OE 040 DESCRIBED TRACT WHICH 5 40 FEET wESTER11 OF THE POINT OF 8EGRN8RG: THENCE SOUTHEASTERLY ALONG THE SOUTHERLY UNE OF SAID DESCRIBED TRACT 40 FEET 10 THE P0IN1 OF BEGNNNG: EXCEPT THAT PORTON OF THE NORTHWEST OUWTER OF SECTOR 26. TOWNSHIP 23 NORTH. RANGE EAST, w.Y, N KING COUNTY. WA58616TON, OESCR1810 A5 FOLL0w5' COMMENCING AT THE SOUTHEAST CORNER OF PROPERTY DESCRIBED IN ♦ DEED DATED FEBRUARY 24 1953. AND RECORDED UNDER RECORDING NUMBER 4317609; THENCE NORTH 7607'40 WEST ALONG THE NORTHEASTERLY RIGHT -OF -687 LINE OF SOUTH 160(8 STREET A DISTANCE OF 109 97 FEET: THENCE NORTH 7055'05" WEST ALONG SND RICHT-OF-MAY LINEA DISTANCE OF 216.50 FEET 10 THE TRUE POINT OF BEGINNING: THENCE CONTINUING NORTH 7055'05" wE57 ALONG SAID PoGHI -OF -681 UNE A DISTANCE OF 88.55 TEO: THENCE NORTH 4025'10" WEST ALONG 5160 RIGHT-OF-WAY LIME A INSTANCE OF 137.58 FEET: THENCE SOUTH 47'21'59" EAST, 60.55 FEET TO A PONT ON A CURVE THROUGH WHC0 A RADIAL UNE OF SAID CURVE BEARS SOUTH 4510'11" WEST FROM THE RADIUS P0474I THENCE SOUTHEASTERLY ALONG SAID CURVE TO THE LEFT HAVING A RA07u5 OF 620.00 FEET 11411WGH4 A CENTRAL ANGLE OF 14'4009" AND A4 WC 051ANCE OF 158.78 FEET TO THE TRUE P0841 OF BEGINNING. LOT AREA TABLE 101 1 AREA (SF ) 101 1 AREA (5 F.) 2 6.563 9 7.925 2 6,693 10 6.871 8 :28 22 6,621 1018 12 6.682 5 8.655 13 6 526 6 8.329 14 6512 7 8.300 15 6517 8 6.868 TOTAL l0 AREA 104198 ST 2.41 AC. AVERAGE 101 AREA 7.273 57 TRACT TABLE TRACT 1 USE AREA (5 T) 999 15ENSINE AREA 35,300 998 I ACCESS/DRAINAGE 2.320 TOTAL AREA 37.700 Sr 0.67 AL VICINITY MAP 67 WTS NOTES 3. 4. S 6. 7. TAX 1: 537920-0005. -0006 WE AREA 160.896 S.F. (3.69 AC) EX51NG USE: SINGLE FAMILY RESIDEMAL (vACANT) PROPOSED USE: 58171E TALLY RESIDENTIAL EX15RNG 2018746: LOW DENSITY RESOENINL (UDR) PROPOSED ZONING: LOW OEN51TY RE5R)ENTNL (106) EXISTING COMPREHENSIVE PLAN DE54NATION. LOW DENSITY RESIDENINL (LCR) 8 PROPOSED CO8PREHENSNE RAN 0510NATION: LOW DENSITY RESIDENTIAL (102) 9. REWIRED M84. LOT WIDTH: 50 FEET 10. PROPOSED YN. LOT 67004: 50 FEET I1. RE [MIRED MIN. LOT AREA 8500 Y 12. PROJECT DENSITY: 4.07 OU/ACRE 13, RE011RED MIN. SETBACKS: FRONT: 20 FEET INTERIOR: 5 FE17 REAR: 10 FEET 14. Mut 875E HEIGHT OF BUILDINGS: 30 FEET 15, WAX LOT COTERAGE: 35 PERCENT 16, STORM DRAINAGE FACILITES 10 BE PRIVATELY OWNED AND LRANIANEO BY HOME OwNER5 AS50CL6RON. 17. SOURCE OF BOLOC417 : MEAD GIl1A N AND ASSOC.. JANUARY. 2006 p4T1W: 71AVD 138 BENCHMARKS. ORIGRK B4 - BRASS DISC 81/PUNCH IN CONC 11LLED PJC PIPE. DOWN 051' IN CASE. WESTERLY OF 2 MONS. 84 INTERSECTION OF 5. 160TH S7. R 5IST AVE. 5. ELEV. = 297.89' 7'958 - 1' '6' ON NORTHERLY CAP BOLT OF FIRE HYDRANT ON THE EAST SIDE 0E S. 160TH S1 250 7EE1 EAST Cl/- CONCRETE FCONCRETE STAIRS. ELEV. 242.39' 28. SOURCE OF TOPOGRAPHY. MEAD GILMAN AND ASSOC., JANUARY, 2006 UTlLfiIES/SERVICES- wA1ER: H012161'E WATER DISTRICT 23826 30TH AVE 5 KEN1, WA 98032 (206) 024-0375 SEWER: 8811 CY VIEW SEWER DISTRICT 14816 MIUITARY RD 5 P.O. BOX 69550 SEATTLE. WA 98168 (2716) 242-1527 POWER/GAS: PUGE7 SOUND ENERGY 105 156714 AVE NE BELLEVUE, WA 98005 1 (888) 321-7779 PHONE: OwE57 COMWN10A70N5 P.O. 60X 91073 swill. WA 98111 1 (800) 744 -11 11 CABLE: CONCAST 4070 AUBURN WAY NORTH AUBURN, WA 98002 7 (877) 824-2288 TIRE IUKWEA FRE DEPARTMENT 144 ANDOVER PINK EAST 1UK67lA. MA 98188 (205) 575-4404 SCHOOL INGHLRE PUBLIC SCHOOLS 15675 ALB.WN 8L`A 59 (WRIER, RA 98166 (206) 433-2141 OWNER/DEVELOPER .8WAID (JOE) AMON 26424 53RD PLACE SOUTH TUKWRA WA 98166 PHONE (206) 856-4255 ENGINEER/PLANNER/SURVEYOR BARbMU5(9 CONSULTING ENGINEERS. INC. 18215 72840 AvE. 50UTM 1E10, WA 98032 (425) 251-6222 TAX (415) 251-8782 CONTACT TOY [MORALISER/ALEXIA DORS. 1 0 JAWAID AMON 16424 53RD PLACE SOUTH SEATTLE, WASHINGTON 98188 7 Y x � i 8 i co N r-40' 70 ,0 BO III 1 1 N PRELIMINARY ROAD, CHANNELIZATION, GRADING AND DRAINAGE PLAN OF LA TOURELLE A PORTION OF THE NW 1/4 OF SECTION 26, TOWNSHIP 23 N., RANGE 4 E , W.M. TUKWILA, WASHINGTON • • SOUTH 159TH STREET t -- DETEN1I0N/I.`E_TENTION VAULT •70`X 40'. SEE\DETAIL SHEET \.7 Er ".• 1 \ REMOVE ROCKERY AS REQUIRED I NEW 5' CONC. SIDEWALK, 4' THICKNESS a7� \ MATCH EXIST COMC VERTICAL CUPS, TYP \` �\ \V_ EXIST STREEI LGHIING END OF EXIST 5 CONC WALK 51ST AVENUE SOUTH SD = 429' `�� FOR A COMBINATION TRUCK ' N AT 25 MPH ISD = 356' FOR A SINGLE -UNIT TRUCK AT 25 MPH- ISD = 282 FOR A PASSENGER CAR NEW BUS STOP AND 10X(0• CONC PAD W/ RAILINGS. SEE DETL. EARTHWORK VOLUMES CUT - ± 12,185 C.Y. FILL - ± 10,101 C.Y. STRIP DUFF - ± 2,335 C.Y. EXPORT - ± 2,084 C.Y. IMPERVIOUS SURFACE PRE -DEVELOPED - 0 SF DEVELOPED - ± 49.617 SF THERMOPLASTIC EXIST. STREET LIGHTING STOP BAR AND LETTERS ON PAVEMENT AND SLOP SIGN MOVE EXIST. BUS S •P PER APPROVAL FROM KC. METRO IO MIN U1ILITY EA5EMENt .0' 11/0 20 70 LEGEND (• STORM I.n4 (• CATCH BASIH TYRE I 1, CATCH BASO. TYRE • E. CON1O0R 00000000 STORY LINE PROPOSED CATCH BASO. TYPE I PROPOSED CATCH BASO. TYPE • PROPOS(0 ROCKER, PROPOSED CONTOUR PROPOSED CONCRETE PROPOSED ASPHALT PROPOSED 'INCE (0000) 02 - AVAI, ABI E [SD = 183 F 'HIS +LL DNS 1 DR A 10 V0,1 SPEED _ INTO THE LINE OF SIGH; FOR ALL VEHICLE T1055 INSTAL STOP SIGN ANO IHEPMOPLASIIC STOPEAR ON PAvE IFN" `2z — t LASS 8 ASPHALT CONCRETE -- RUSHED SURFACING \ LCLASS 8 GRALTL `SIORm SC*(R & CATCH ETASw (SEE 1011*0A TYRCAI DC1A&S) _ 75 1HTCK450 00 RIOUR(D D/ C0GINCE0'S DESIGN 40' R/W CURB AND GUTTER ROADWAY SECTION ROAD 'BI NC' '0 SZAL -- ETF+(5 A(« 75 10 MIN %Purr [ASEM(N1 11 _CEMC01 CONCPCI( \\l SIDCWAL K -7' 01 0/6' 01041,0 CRUSHED ROCK. —CLUE N' [(MGR(11 CURB & C.J1114 S(( IUK0RA TYP,CAL 1014,5 20" TO' x 10' ::..•:. •:x k:. ,.0 v:4c;•r:xc e; c•acc;:.c:x-v:v 2" ASPHALT CONCR(70 - \ i ASO BASE 1/ 1 2" CRUSHED SURFED SUREA[wG BASE COURSE 0.0011100/11 R000UIRED OCPENDING/J146I ON 501 0000111005. SCC 5(0, 0.02 -------- 20' JOINT USE DRIVEWAY 001 '0 SCALE CITY FILE NOS. PRELIMINARY ROAD, CHANNELIZAT1ON, GRADING AND DRAINAGE PLAN 0 m co 0 0 0) F- a. a 0 0 z 0 m 1- w 0 0 a 1- ✓ w 0- -J a w z 0 onessemaam OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-1 6747 M.L. King Way South PAGE 1 OF 3 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/20/06 COMPLETED 6/20/06 GROUND ELEVATION 256 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING --- LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop 1 24hrs AFTER DRILLING 18.0 ft / Elev 238.0 ft o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS U.S.C.S. GRAPHIC LOG MATERIAL DESCRIPTION - -� 5 MC=15% MC=19%GSes=26% MC=13% MC=22% - MC -32% MC=27% MC=32% LL=45 PL=26 Fines=93% , GS, HYD, AL SP- SM • Medium dense, fine to medium, gray -brown SAND with SILT with some oxidation 251.5 SS 33 526 (1 )•••4.5 SM SM SM SM SM . : ,::` ., •` : • ` : • : ti•. :: .. .. `.••••: - .•. `-. '• • Very loose, gray Silty SAND with Gravel Medium dense, gray Silty SAND with gravel in tip of sampler Loose, gray Silty SAND with gravel in tip of sampler Medium dense, brown, Silty SAND with a 1 inch layer of oxidized sand at approximately 16 feet 1 20.8 Loose, brown, interbedded Silty SAND and medium stiff SILT, lowest 2 235.3 - ` 10 X SS 33 4(x)2 x J\/\ 3S 33 3� _ - 15 x 4S 44 44MC=18% 4-4-5 _ - 20 / \ SS 44 4(21)3 25 SS 6- 56 2-3-5 (8) ML ML \inches gray SILT Very stiff, dark gray SILT Very stiff, dark gray SILT - _ 30 \ / �S 56 8 2615 ---X 35 SS 8 100 7 (30) 8 A-3 (Continued Next Page) c- 0 0 C7 vi z 3 c? z Er 0 m >-- cc 0 a 1- J w a x CO CCw z 0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-1 6747 M.L. King Way South PAGE 2 OF 3 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington c,, DEPTH u, (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui Li GRAPHIC LOG MATERIAL DESCRIPTION - _ 40 ST !! 100 MC=27%DS DD=93pcf , MC=25% MC=27% MC=28% MC=28% MC=34% DD=87pcf , DS MC=30% MC=32% Fines=99% , GS MC=33% MC=28% ML ML ML ML ML ML ML ML ML ML Very stiff, dark gray SILT Hard, dark gray SILT Hard, gray SILT Very stiff. gray SILT Very stiff, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT with 1 -inch thick seam of fine SAND at 71 feet �p (34) 100 8 9 - - 45 1 100 9-16-21 7 - 50 \ / 12 100 7 �25� 4 _ 55 \ / x 13 100 7-10-14 (24) _ _ 60 ST 14 , 100 100 9 l35) 8 15 - 65 SS 16 100 12-17-21 (38) - _ 70 \ j x S� 100 10(51)28 75 X SS S$ 100 12(66)35 ) A-4 (Continued Next Page) 0 m 0 0 to z 0 a 0 z 0 m rr a 0 J F- J J W 1 a x m W Z 0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-1 6747 M.L. King Way South PAGE 3 OF 3 Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DEPTH cn (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui (.5 GRAPHIC LOG MATERIAL DESCRIPTION _X S9 100 16-26-31 (57)MC=30% MC=26% MC=27% MC=30% ML ML ML ML ML ML Hard, gray SILT with medium SAND in tip No recovery Hard, gray SILT with distinct 1/4 -inch lamination dark gray to black SILT at 86.25 feet. Inclined bedding orientation. Massive silt present above and below sand lamination. Hard, gray SILT Hard, gray SILT X01 5 Hard, dark gray SILT 154.5 80 SS 0 50/6" - 20J 85 _ X / \ 21 100 16(64)38 - 90 - (\ SS 22 100 15-270-43 (7)MC=26% 95 X ( SS 23 100 20-30-39 ( ) 100 XSS 101 23-50/6" Bottom of hole at 101.5 feet. A-5 co m 0 z a 0 z 0 0 >- 0 0 cea a 7 W a x CC W Z 0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-2 6747 M.L. King Way South PAGE 1 OF 3 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/21/06 COMPLETED 6/21/06 GROUND ELEVATION 205 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING --- LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop AFTER DRILLING --- DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS GRAPHIC LOG MATERIAL DESCRIPTION - MC=21% Fines=44% GS MC=12% MC=20%DS -86pcf , MC=16% Fines=20% , GS MC=27% DD=93pcf , DS MC=29% MC=29% SM- SM . s•: ` -:-,•: :=• ' ` •_ .. Gravelly drilling from 1.5 feet to 5 feet - Loose, light brown Silty fine SAND ' 11.0 Medium dense, light brown Silty fine SAND �0 - 10 v SS44 1 2-3-4 (7) _ 15 \J x ?S 100 5(��� .:• .: •100 :- • : :c\ . -•: Medium dense, light brown Silty fine SAND with Silt - Medium dense, light brown fine SAND with Silt occasional thin oxidized ": layers `•'18.0 187.0 SP- SM SP SM 3ST - 20 SS 100 4-11-13 (24) (24) SM.. • `'-• ,• •••`'•• •Loose to medium dense, Silty fine SAND 23.0 to medium dense, Silty fine SAND 182.___0 _ 25 ST 5 100 6S 67 �10� ML ML ML \Loose Stiff, gray Sandy SILT Very stiff, gray SILT Very stiff, gray SILT _ 30 \ / X SS 56 8 58 MC=30% _ 35 X 8S 100 8� A-6 (Continued Next Page) N co o 1- 0 m 1- 1- 3 3 a 0 0 z 0 m >- 0 0 1- W a 1- x m 0 w z 0 OTTO ROSENAU ASSOCIATES, INC. BORING NUMBER B-2 6747 M.L. King Way South PAGE 2 OF 3 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DEPTH cn (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS U.S.C.S. GRAPHIC LOG MATERIAL DESCRIPTION 40 IST 9 100 MC=27%DS DD=97pcf , MC=25% MC=30% MC=29% LL=33 PL=26 Fines=96% , GS, HYD, AL MC=30% MC=29% MC=31% MC=24% ML ML ML ML ML ML ML Very stiff, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT with distinct 1/4 -inch lamination black SILT at 71 feet. Inclined bedding orientation. 45 x �� 67 5-12-124 _ 50 \/ X 1 100 7 �30� 7 55SS X S2 78 10(4823 60 x S3 100 9 �38� 2 _ 65 x 14 100 15($)23 70 X 15 100 16�52�26 _ _ 75 X 16 100 15(83)52 2 A-7 (Continued Next Page) GENERAL BH / TP /WELL TUKWILA PROPERTY BORINGS.GPJ GINT US.GDT 8/6/07 A-8 OTTO ROSENAU & ASSOCIATES, INC. M.L. King Way South WA 98118 (206) 725-4600 (206) 723-2221 Amon PROJECT NAME PROJECT LOCATION BORING NUMBER B-2 PAGE 3 OF 3 Tukwila Property 6747 Seattle, Telephone: CLIENT PROJECT Fax: Mr. Jawaid NUMBER 06-373 53rd Ave. S. and S. 160th St., Tukwila, Washington DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui v0i GRAPHIC LOG MATERIAL DESCRIPTION 80 x �� 100 17-42-47`89) MC=24% MC=22% ML ML 81.5 Hard, gray SILT Hard, gray SILT 123.5 -v n SS 18 100 22(74)40 (74) Bottom of hole at 81.5 feet. A-8 immosammEsszi OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-3 6747 M.L. King Way South PAGE 1 OF 2 Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/22/06 COMPLETED 6/22/06 GROUND ELEVATION 228 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING --- LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop AFTER DRILLING --- DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui vUi GRAPHIC LOG MATERIAL DESCRIPTION MC=16% MC=33% MC=14% MC=15% MC=21 % Fines=15% GS MC=14% MC=20% SP- SP- SM :;::.; ": .... ':1� `: ..- : Medium dense, brown, fine to medium SAND with SILT, some oxidation evident Medium dense, light brown, fine to medium SAND with Silt 6.5 221.5 X /// \\\ �S 100 3-4-81 (12) - 5 -v n SS 2 89 6-9-9 (18) SW •. �•;•z Medium dense, light brown, well -graded Silty SAND 9.5 218.5 X /// ��` 3- S 33 $� - 10 SP- SM SP- SM SP- SM SP- SM SP- SM ::.,.� ;• :: ••.=•• - • ' . :-ti .lt ::.• -: "", :; :..ti i.. •`.: . . ` ti '.:: . " :• No recovery with trace fine sand in sampler Medium dense, light brown, fine to medium, SAND with Silt and gravel Medium dense, light brown, fine to medium SAND with Silt and gravel Dense, light brown, fine to medium SAND with Silt and occasional gravel with some oxidation evident Medium dense, light brown, fine to medium SAND with Silt and occasional gravel with some oxidation evident 29.0 199.0 SS0 4 10 13 17 (30) X 5S 22 1��9�8 15 - - - 20S SS 6 33 6-5-7 (12) - - 25 \ 7S 100 8 (33) 2 - - - _ 30 X / \ S8 44 7-24)8 SM t :'• '`.= : ti " No recovery 35 SS17-15-17 9 0 (32) A-9 (Continued Next Page) 0 0 m 1- 0 U' z z 0 a 0 0) 0 z 0 m cr cr0 0 a a 1- 1- w a 1x 0 uJ w z insfsmisionsimm OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-3 6747 M.L. King Way South PAGE 2 OF 2 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington V, DEPTH cn (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui d GRAPHIC LOG MATERIAL DESCRIPTION _X 40 0 100 11-10-100 MC=28% MC=26% MC=22% LL=39 PL=22 Fines=88% , GS, HYD, AL MC=31% MC=29% MC=30/ SM ML .' -:.:.. •: ``- .:s:: Medium dense, light brown, fine to medium, Silty fine to medium SAND with interbedded Sandy SILT 38.0 190.0 SM Dense, light brown, Silty fine SAND 44.0 184.0 45 XSS56 11 14(37)23 CL CL CL CL CL No recovery with trace clay in sampler Hard, gray lean CLAY Hard, gray lean CLAY Hard, gray lean CLAY Hard, graylean CLAY16 161.5 =X 50 \xj SS0 12 24-18-21 (39) 55 SS 13 56 15-21-23 23 (44) _ 60SS x 14 100 13`47)23 - - 65 15 100 15-28-25 (53 ) SS X 100 14-26-58 (84) Bottom of hole at 66.5 feet. A-10 0D z 0 a. 0 0 z 0 0 m 1- w 0 t D W O. x m w z 0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-4 6747 M.L. King Way South PAGE 1 OF 2 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/19/06 COMPLETED 6/19/06 GROUND ELEVATION 228 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger V- AT TIME OF DRILLING 11.0 ft / Elev 217.0 ft LOGGED BY Anthony Coyne P.E. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer SPT sampler, 30 -inch drop AFTER DRILLING --- DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS v0i GRAPHIC LOG MATERIAL DESCRIPTION - - 5 MC=15% MC=13% Fines=26% GS MC=15% MC=25%GSes=13% MC=30% MC=24% MC=260/0 SM SM SM SM SM •-- : • • " "`'' •": s.•.,-•, :: ,•:ti••• •: • :..:. •::t_• "•` -•- .. -.• • :: ." `: •' Medium dense, gray, Silty fine to medium SAND with occasional debris and organics (charcoal and root hairs) (fill) Loose, fine to medium, gray Silty SAND (fill) Medium dense, gray Silty SAND with occasional fine gravel (fill), oxidation present. Medium dense, gray, Silty Sand with occasional fine gravel (fill), oxidation 11.0 217.0 SS 1 89 6-5-6� - -//�\ - 10 SS 2 100 4-4-4 (8) x 3S 100 (11) MC=16% - - - - 15 , n SS 4 100 3-3-6 (g) SM SM SM SM SM ,:•' present. / Loose, gray, Silty fine SAND Medium dense, light brown, Silty fine SAND •• Medium dense, gray Silty fine SAND -- . Medium dense, gray, Silty fine SAND 1 Medium dense, light brown, Silty fine SAND, with some oxidation `'-' - - 20 S5S 89 474) - _ 25 x 6S 100 4(181 - 30 SS 67 6(17) - 35 X 8 56 5 (30) 8 A-11 (Continued Next Page) CO CD a 0 U) z a 0 z Fr - 0 1- 0 a. a 1- F W m W Z 0 OHO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-4 6747 M.L. King Way South PAGE 2 OF 2 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington (,) DEPTH cn (ft) SAMPLE TYPE NUMBER RECOVERY BLOW COUNTS (N VALUE) TESTS U.S.C.S GRAPHIC LOG MATERIAL DESCRIPTION 9S X 33 2(8-91)1 MC=26 , GSes-49% MC=33% ° MC=29/° SM SM •: ::: ':''::46.3 Medium dense, light brown, Silty fine SAND Loose, bluish -gray, Silty fine SAND Medium dense, bluish -gray, Silty SAND 181.8 _X 45 SOS 33 8--3 (63)MC=23%SM _x -/ 50 \/ \ �S 67 (11) ML ML ' Stiff, bluish -gray, Sandy SILT Very stiff, bluish -gray, SandySILT 51.5 ry 9 y. 176.5 _X 12 100 5(1�) Bottom of hole at 51.5 feet. A-12 0 c? z a. 0 0 c7 0 m 1- 0 0 1 • a 1- W a 1- m W Z 0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-5 6747 M.L. King Way South Seattle, WA 98118 PAGE 1 OF 2 _•___ Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/19/06 COMPLETED 6/19/06 GROUND ELEVATION 243 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING --- LOGGED BY Anthony Coyne P.E. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop 1 24hrs AFTER DRILLING 3.0 ft / Elev 240.0 ft DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui Ci ui GRAPHIC LOG MATERIAL DESCRIPTION - - - 5 MC=10% Fines=7% , GS MC=27% MC=26% Fines=8% , GS MC=30% MC=32% Fines=23% , GS MC=25% MC=33% SM : •`:.:1 5 Loose, dark brown, Silty fine SAND (topsoil) 241.5 SP- SP- SM SP- ML ::-'" : -•• • : .• . r•`'•`� .:: ••••.:.: ; - • : . `'' .7: Loose, light brown, fine to medium SAND with Silt and occasional organics Loose, light brown, fine SAND with Silt Loose, light brown, fine SAND with Silt and occasional interbedded Silt Y Medium dense, light brown, fine SAND with Silt 13.0 230.0 X ;S 100 45 (9)=13% _V - - n SS 2 100 4-4-4 (8) X 3S 100 (13) -� - - 15 SS 4 100 4-6-6 (12) ML Stiff, light brown, Sandy SILT with thin, interbedded fine, dean SAND seams, oxidation present 18.0 225.0 - 20 1/ ]( / \ 5S 100 5� SM SM •. _.. .. :.• • .:- •'•`' Medium dense, light brown, Silty fine SAND Dense, light brown, Silty fine SAND 28.5 214.5 25 X SS 6 89 3-5-6 (11) - _ - -• 30 S X 100 9 �32� 6 SP- SM , ' :'` •` :31.0 Medium dense, gray, fine SAND with SILT 212.0 - - 35 X SS $ 100 9-10-8 (18) Very stiff, gray, Sandy SILT 33.3 209.8 ML A-13 (Continued Next Page) GENERAL BH / TP / WELL TUKWILA PROPERTY_BORINGS.GPJ GINT US.GDT 8/6/07 mansimematimm OHO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-5 6747 M.L. King Way South Seattle, WA 98118 PAGE 2 OF 2 ._ _ Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St. Tukwila, Washington DEPTH cn (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS vi cS ui GRAPHIC LOG MATERIAL DESCRIPTION 40 SS 9 100 9-11-12 (23) ° MC=31 /o MC=30% LL=33 PL=26 Fines=98% , GS, HYD, AL MC=30% SP- SM / • --• 35.8 Medium dense, gray, fine SAND with SILT 207.3 Very stiff, gray SILT Very stiff, gray SILT Very stiff, gray SILT Stiff, gray SILT 51.5 191.5 ML ML ML _ -:X 45 SS 100 5-16� _ 50 x11 SS 100 7 (29) 5 MC=29% _ _ X / \ 12 100 (14) 4146 Bottom of hole at 51.5 feet. A-14 in 0 0 J z a 0 m m 0 w CC0 a D W 0 J 3 a x CO 1 w Z OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-6 6747 M.L. King Way South PAGE 1 OF 1 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA DATE STARTED 4/6/07 COMPLETED 4/6/07 GROUND ELEVATION 232 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Davies Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger V AT TIME OF DRILLING 31.0 ft / Elev 201.0 ft LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 # safety hammer, SPT sampler, rope and cathead, 30 -inch drop AFTER DRILLING --- DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS ui (..i GRAPHIC LOG MATERIAL DESCRIPTION _ _204 10......X31/1013±\_ SS 1003 2 2 MC=14% MC=12% MC=10% MC=7% MC=7% MC=27% MC=28% MC=30% MC=27% MC = 30% SP- SM SP SM SP- SM "- C::, C'::', .• -: ':, .-: . •..• .� : `.:• Loose, light brown, fine SAND with silt (moist) Loose, light brown, fine SAND with silt (moist) Loose, light brown, fine SAND with silt (moist) 12.0 220.0 2 4 4 8 J _6 - 20 3 - 3-3 SP• SP SP •' • ; :5:,• Medium dense, light brown, fine SAND (moist) Medium dense, light brown, fine SAND (moist) Medium dense, light brown, fine SAND (moist) 28.0 204.0 4S 100 4148 J _ _ _ 30 41_/_10(:"\_i_ S 100 _L6-29;11_, SS 6 00 27 8-11-16 SM ': "' • `'• .• . : V Medium dense, light brown, Silty fine SAND (moist to wet) 33.0 199.0 - _X\_5_1/10.9_\_7-11-14 _ 40 SS 7 100 8-10-10 20 25 J SP- SM :' ' �• •ti` '••.. • " ? : : Medium dense, light brown, fine SAND with silt (wet) 38.0 194.0 ML ML ML Very stiff, gray, sandy SILT with interbedded silty sand (wet) Hard, gray SILT (wet) 51.5 Hard, gray SILT (wet) 180.5 _ 50 9S100 9 616 SS \_:_10_./--\_i___,45 100 12-19-26 43t.:_,0_0_,:_,1_,_,_11_19 Bottom of hole at 51.5 feet. A-15 0 0 u; (79 1- a 0 m 0 a 0 D Cr W 0 1- -J J 3 0. a LU w Z 0 OTTO ROSENAU & ASSOCIATES, INC_ BORING NUMBER B-7 6747 M.L. King Way South PAGE 1 OF 2 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA DATE STARTED 4/6/07 COMPLETED 4/6/07 GROUND ELEVATION 226 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Davies Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger V. AT TIME OF DRILLING 15.0 ft / Elev 211.0 ft LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 # safety hammer, SPT sampler, rope and cathead, 30 -inch drop AFTER DRILLING --- o DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS U.S.C.S. GRAPHIC LOG MATERIAL DESCRIPTION SS 1 33 1-1 MC=26% MC=14% MC -16% MC=15% MC=17% MC=16% MC=14% MC=12% MC=14% MC=12 ° /o - 0 MC /° MC=25% SM ::....:.• . � �•. Very loose, brown, Silty SAND with organics (moist, bark) 1.5 224.5 - r SS 2 100 1-1-1 (2) SP- SM �' . i '` • • ` _ Very loose, brown, fine to medium SAND with silt and debris fragments (moist, brick) 223.0 5 SS 3 100 1-2-3-4 (5) SM . _ :...: . Loose, brown, Silty SAND with organics and occasional gravel (moist, roots and charcoal) 4.8 221.3 ML ML ML Very stiff, gray, sandy SILT (moist, heavily oxidized, root hairs and charcoal) Stiff, gray, sandy SILT with organics and occasional gravel (wet) Stiff, gray, sandy SILT with organics and occasional gravel (moist) 9.8 216.3 _ SS 4 100 6-9-11 (20) 5S 100 (13-5-5 ) 10 6S 100 X13) SM SM SM :. ti .• . �• '• •''• f — :.. •.:.. x:.14.5 Medium dense, gray silty SAND with occasional gravel (moist) Dense, gray silty SAND (moist) Medium Medium dense, gray silty SAND with occasional gravel (moist) 211.5 _ - SS 7 100 2-5-6-10 (11) 813 6--18 i3 - - 15 SS 100 12-7-10 ( ) SP- SM SP- SM .' :- •::: ... ' .: ' . , .:. . ` ` ` t� Si Medium dense, gray, fine to medium SAND with occasional gravel (wet) Medium dense, gray, fine to medium SAND (wet) Medium dense, light brown, fine to medium SAND (wet) SS 10 100 15-10-11-8 (21) SS 100 4-6-8 - -1 20 SS 12 100 8-11-15 (26) A-16 (Continued Next Page) co m 0 0 c1 D 0 0 w 0 w J J LU 7 0 J w a x m cc Lu Lu0 OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-7 6611 6747 M.L. King Way South PAGE 2 OF 2 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA F) DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS 6 ci GRAPHIC LOG MATERIAL DESCRIPTION 25 ( SS 13 100 8-17-19 (36) MC=27% ° MC 27 /° MC=27% MC=24% Sp_ SM Sp_ SM SP-• SM :••••••;:`..:• :• r• •::- •. •• = ...•... - : • . •`• ; ��• ., : ' . .• r Dense, light brown, fine to medium SAND with silt (wet) Dense, light brown, fine to medium SAND with silt (wet) Very dense, light brown, fine to medium SAND with silt (wet) 35.5 190.5 - -X 30 SS 14 100 8-16-16 (32) - -X - -• 35 SS 15 100 37-37-28 (65) _ _ SS 16 100 5-11-17 (28) ML 36.5 Very stiff, gray SILT (wet) 189.5 Bottom of hole at 36.5 feet. A-17 co co 0 cri1- z 0 a m 0 uJ 0 0 0 0 W a x CO a w 0 Emszaminammi OTTO ROSENAU & ASSOCIATES, INC. BORING NUMBER B-8 6747 M.L. King Way South PAGE 1 OF 1 Seattle, WA 98118 Telephone: 725-4600 (206) Fax: (206) 723-2221 CLIENT Jawaid Amon PROJECT NAME La Tourelle Plat PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, WA DATE STARTED 4/6/07 COMPLETED 4/6/07 GROUND ELEVATION 224 ft HOLE SIZE 8 -inches DRILLING CONTRACTOR Davies Drilling GROUND WATER LEVELS: DRILLING METHOD Hollow Stem Auger V AT TIME OF DRILLING 7.0 ft / Elev 217.0 ft LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING --- NOTES 140 # safety hammer, SPT sampler, rope and cathead, 30 -inch drop AFTER DRILLING --- DEPTH (ft) SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS vi u0i GRAPHIC LOG MATERIAL DESCRIPTION _ _ - - - - 10 SS 1 22 1-3-9 12 MC=18% MC=9% MC=26% MC=133% MC=446% MC=70% MC=23% MC=19% MC=18% MC=16% MC=18% MC=21 % MC=20% MC=19% MC=26% SM -:. Medium dense, brown silty SAND and gravel and occasional debris (asphalt fragments, and roots) (moist) 6.0 218.0 11-8-5 13 SS 2 2 SS 3 2-3 3 6 JSP- 100 SM "; " •216.0 - Loose, brown fine to medium SAND with silt and organics (moist becomes SS 4 2-2-2 4 100 -qv.-8"0 •�•�•� ..♦• wet at 7.0 feet) Wood.••••• Loose, dark brown, decayed, wood fragments with sand (wet) 11.5 212.5 yl 5S _i 1-31 _ _ _ 20 100 OL _ .. — Soft, black Organic SILT with wood fragments (wet) 14.0 210.0 6S 1-4-2 100 SM : `.' *.; Medium dense, light brown, Silty SAND with organics and occasional gravel (wet) 18.0 206.0 SS 7 4-7-9 16 J,• 100 ML Stiff, gray, sandy SILT with interbedded sand (wet) 23.0 201.0 - _ 30 S 100 4-53-8 ___8___/---- SM :: �•: ti: = Medium dense, light brown, fine Silty SAND with occasional gravel (wet) 28.0 196.0 SSS 100 6-9--10 SP SP SP SP -. :' • • •: : •.48.0 Medium dense, light brown, fine Silty SAND with occasional gravel (wet) Very dense, light brown, fine SAND (wet) Very dense, light brown, fine SAND (wet) Medium dense, light brown, fine SAND (wet) 176.0 _ - 40 SS It 100 5-9-16 25 SS 11 100 6-21-38 59 _ _ - 50 SS 12 100 5-22-33 55 SS 13 100 8-8-10 18 J SP- \ SM / : .. .51.0 Very dense, light brown, fine SAND with silt (wet) 173.0 _ SS 14 101 33-32- 50/6" J 56.5 Hard, gray SILT (wet) 167.5 ML SS 15 100 10-18-22 40 Bottom of hole at 56.5 feet. A-18 BORING LOG NOTES These notes and boring logs are intended for use with this geotechnical report for the purposes and project described therein. The boring logs depict ORA's interpretation of subsurface conditions at the location of the boring on the date noted. Subsurface conditions may vary, and groundwater levels may change because of seasonal or numerous other factors. Accordingly, the boring logs should not be made a part of construction plans or be used to define construction conditions. The approximate locations of the borings are shown on the Site Plan. The borings were located in the field by measuring from existing site features. "Boring Size" refers the diameter and type of auger used. "HSA" denotes hollow -stem auger. "SSA" denotes solid -stem auger. "BA" denotes bucket auger. "Sample Number and Type" refers to the sampling method and equipment used during exploration where: o "SS" indicates split -spoon sampler with 1-3/8" inside diameter and 2" outside diameter. O "ST" indicates sample attempted using a Shelby thin-wall sampling tube with 3" O.D. "N -Values" refer to the Standard Penetration Test which records number of blows from a 140 -pound hammer falling 30 inches required to advance a standard sampler eighteen inches. The blow counts required to drive the sampler through each 6 -inch interval is recorded. The number of blows to drive the sampler for the last 12 inches of driving are added together and is considered to be the N -Value. The N -Value is presented in parentheses on the boring logs. The actual blow count values for each 6 -inch interval is also presented. If the sample is driven less than 6 inches for a given interval, the actual distance driven is recorded. "Moisture Content (MC)" refers to the moisture content of the soil expressed in percent by weight of dry sample as determined in the laboratory. "Grain Size (GS)" refers to a grain size distribution analysis completed in general accordance with the ASTM D422 test procedure. "Hydrometer (HYD)" refers to a grain size distribution analysis completed in general accordance with the ASTM D422 test procedure. "Fines" is an estimate of the portion of a soil sample passing a No. 200 sieve as determined using the ASTM D422 test procedure. A-19 "Atterberg Limits (AL)" refers to a determination of the liquid and plastic limits of a cohesive soil using the ASTM D 4318 test procedure. "Dry Density (DD)" refers to an estimate of the dry density of a soil sample collected using a Shelby thin-wall sampling tube. "Direct Shear (DS)" refers to an estimate of the shear strength of a soil as determined using direct shear test equipment and performed in general accordance with ASTM D 3080. "Description and USCS Classification" refer to the materials encountered in the boring. The descriptions and classifications are generally based on visual examination in the field and laboratory. Where noted, laboratory tests were performed to determine the soil classification. The terms and symbols used in the boring Togs are in general accordance with the Unified Soil Classification System. Laboratory tests are performed in general accordance with applicable procedures described by the American Society for Testing and Materials. "V" Indicates location of groundwater at the time noted. TERMS for RELATIVE DENSITY of NON -COHESIVE SOIL Term Standard Penetration Resistance "N" Very Loose 4 or less Loose 5 to 10 Medium Dense 11 to 30 Dense 31 to 50 Very Dense Over 50 blows/foot TERMS for RELATIVE CONSISTENCY of COHESIVE SOIL Term Unconfined Compressive Strength Very Soft 0 to 0.25 tons/square-foot (tsf) Soft 0.25 to 0.50 tsf Medium Stiff 0.50 to 1.00 tsf Stiff 1.00 to 2.00 tsf Very Stiff 2.00 to 4.00 tsf Hard Over 4.00 tsf A-20 DEFINITION of MATERIAL by DIAMETER of PARTICLE Boulder 8 -inches+ Cobble 3 to 8 inches Gravel 3 inches to 5mm Coarse Sand 5mm to 0.6mm Medium Sand 0.6mm to 0.2mm Fine Sand 0.2mm to 0.074mm Silt 0.074mm to 0.005mm Clay Tess than 0.005mm SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS TYPICAL DESCRIPTIONS GRAPH LETTER COARSE GRAINED SOILS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE THAN 50`)/o OF COARSE FRACTION RETAINED ON NO. 4 SIEVE CLEAN GRAVELS (LITTLE OR NO FINES) PW ' Sr ). �� •• ii w ••11)- �•� . .11''0,, VS 1- �� GW WELL -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES 0Qo )o DO0000 oQoV p�o pC i Gp POORLY -GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES GRAVELS WITH FINES (MORE THAN 12% FINES) pV ° oO 1 a qb 1i o411 ', oC tO GM SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES 7A+ ! �Al o'dp � - � GC CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES SAND AND SANDY=` SOILS MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE CLEAN SANDS (LITTLE OR NO FINES) • �+ SW WELL -GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES =: � � SP POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES SANDS WITH FINES (MORE THAN 12% FINES) SM SILTY SANDS, SAND - SILT MIXTURES . . SCCLAYEY SANDS, SAND - CLAY MIXTURES FINE GRAINED SOILS MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE SILTS AND LIQUID LIMIT LESS THAN 50 CLAYS ML INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY j / / CL INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS __ __ OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY SILTS LIQUID LIMIT AND GREATER THAN 50 CLAYS MH INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS ACH INORGANIC CLAYS OF HIGH PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS `„ „ � i'PEAT, `„ PT HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS NOTE: FINES ARE MATERIALS PASSING THE NO. 200 SIEVE. COARSE GRAINED SOILS RECEIVE DUAL SYMBOLS IF THEY CONTAIN BETWEEN 5% AND 12% FINES. FINE GRAINED SOILS RECEIVE DUAL SYMBOLS IF THEIR LIMITS PLOT LEFT OF THE "A" LINE WITH A PLASTICITY INDEX (PI) OF 4% TO 7%. A-22 PLASTICITY INDEX 50 40 , 30 -- 20 CL -ML 10�_ _..i__ 7 4 0 , _II. __/ i/A/Z/1_ _ ML or OL , , O c'-• o•' I ......>1 .. --- ( J, ,, ... _. - i- - . Q1 V��� _-ryLOI , i • P ,Py ,_f.. Io`o' G • I MH or CH 10 16 20 30 40 50 60 LIQUID LIMIT 0 80 90 100 SYMBOL EXPLORATION NUMBER SAMPLE DEPTH MOISTURE CONTENT (%) LIQUID LIMIT (%) PLASTIC LIMIT (%) PLASTICITY INDEX, PI (%) SOIL DESCRIPTION O B-1 30 - 31.5 feet 32 45 26 19 Very stiff, gray SILT (ML) O B-2 50 - 51.5 feet 29 33 26 7 Hard, gray SILT (ML) O B-3 50 - 51.5 feet 22 39 22 17 Hard, gray, lean CLAY (CL) A 8-5 30 - 31.5 feet 30 33 26 7 Very stiff, gray SILT (ML) Note: Atterberg limits determined in general accordance with the ASTM D 4318 test procedure. ATTERBERG LIMIT TEST RESULTS Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 30, 2007 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-23 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 0 0 0 0 -Y-1- PERCENT FINER 1-- - — -_._ 0.75 in. ---1• --1 it III r 11— -r a.l - li ,I , _t. _- - -- '---- ._"-'1- - ___j_ i, I' i . t- .1_ - I • �. 1 .1.. .I i i }. I , .l 1 1 1 75.8 0.25 in. 1 , l #4 70.1 I Ii J' 1, 65.0 IIJ.i II —I- 52.9 III #100 i!i I I il� � � I I 1I 500 100 10 1 GRAIN SIZE - mm 0.1 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 29.9 44.0 26.1 SIEVE SIZE PERCENT FINER SPEC.` PERCENT PASS? (X=NO) 0.75 in. 100.0 0.625 in. 79.8 0.5 in. 77.0 0.375 in. 75.8 0.25 in. 72.4 #4 70.1 #10 65.0 #40 52.9 #100 33.7 #200 26.1 (no specification provided) Sample No.: 2700 Source of Sample: Location: B I Sample #2 Checked By: A. Coyne Soil Description Sample #2700 - B I Sample #2: Gray Silty Sand with gravel Atterberq Limits (ASTM D 43181 PL= NP LL= NV P1= NP Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 16.9 D60= 0.793 D50= 0.358 D30= 0.113 D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-24 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 1.6 5.0 74.8 18.6 SIEVE SIZE PERCENT FINER SPEC.* PERCENT 1 0.5 in. 100.0 0.375 in. 98.5 0.25 in. 98.5 #4 ' I 1 1 � III; r 11 I I ' ' .I 1-4L L 11 #40 1 7 I ' ' 1 11. J7 1 Jl1 - -1-LF 1 1 111i { I I -' �_ _ __ •- _-, i I ' I I II 1 I 1 1 ,-._ -.,-,_--•_-ii-.1. ./_./-.. 1 Ij j l ' I I 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 1.6 5.0 74.8 18.6 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) 0.5 in. 100.0 0.375 in. 98.5 0.25 in. 98.5 #4 98.4 #10 98.3 #40 98.1 #100 95.2 #200 93.4 (no specification provided) Sample No.: 2700 Source of Sample: Location: Bl Sample #8 Checked By: A. Coyne Soil Description Sample #2700 - B1 Sample #8: Dark Gray Silt Atterberg Limits (ASTM D 43181 PL= 26.3 LL= 45.4 P1= 19.1 Classification USCS= ML AASHTO= A-4(0) Coefficients D85= 0.0290 D60= 0.0116 D50= 0.0098 D30= 0.0068 D15= 0.0043 D10= 0.0029 Cu= 3.99 Cc= 1.38 Date Tested: 7/27/2006 Tested By: A. Duong Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 30 to 31.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-25 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 Particle Size Distribution Report - ASTM D 422 500 100 5 N D 10 GRAIN SIZE - mm 0.001 % COBBLES Vo GRAVEL % SAND % SILT % CLAY 0.0 0.0 1.0 99.0 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 100.0 #100 99.5 #200 99.0 (no specification provided) Sample No.: 2700 Source of Sample: Location: B1 Sample#16 Checked By: A. Coyne Soil Description Sample #2700 - B1 Sample #16: Gray Silt Atterberq Limits (ASTM D 4318) PL= NT LL= NT PI= NT Classification USCS= ML AASHTO= A-4(0) Coefficients 085= D60= 030= 015= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder D50= 010= Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 60 to 61.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-26 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 500 100 10 1 GRAIN SIZE - mm 0 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 55.3 44.0 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 99.3 #10 99.1 #40 98.7 j l11 :. 70.6 #200 44.0 I 1-4 r 1 ti 4 iii+-',--- I 44 f ..... 4 4 - - -._- _1_ f _4..- 1 - _1 - - _ _i�._i �1ii' �- - ---- - -- - - � -t- - I, I. 4 1 -.....,-.-1_,i_ .I I «i ,I, _._L _...L_ .1.... i' -.-L-�L - _._.1 j 1I''I' I 500 100 10 1 GRAIN SIZE - mm 0 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 55.3 44.0 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 99.3 #10 99.1 #40 98.7 #100 70.6 #200 44.0 (no specification provided) Sample No.: 2700 Source of Sample: Location: B2 Sample #1 Checked By: A. Coyne Soil Description Sample #2700 - B2 Sample #1: Light brown Silty Sand Atterberg Limits (ASTM D 43181 PL= NT LL= NT PI= NT Classification USCS= SM AASHTO= A-4(0) Coefficients 085= 0.243 D60= 0.112 D50= 0.0870 D30= D15= 010= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-27 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 9. ao R R # a A": 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 79.9 20.1 SIEVE SIZE PERCENT FINER SPEC.* PERCENT I. #4 100.0 #10 100.0 #40 99.8 #100 68.6 #200 20.1 � it IL I—� ,� I Ili -4— . 1 i. a 4 -j I. i t 7 ; , ,- .1 1 } I ''i . -.. - •'I i +�+ 4 JJ i. i , .. I I I • - t --1 - -t. 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 79.9 20.1 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 99.8 #100 68.6 #200 20.1 (no specification provided) Sample No.: 2700 Source of Sample: Location: B2 Sample #4 Checked By: A. Coyne Soil Description Sample #2700 - 132 Sample #4: Light brown Silty Sand Atterberg Limits (ASTM D 43181 PL= NT LL= NT PI= NT Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 0.221 D60= 0.130 D50= 0.112 D30= 0.0852 D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 15 to 16.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-28 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 Particle Size Distribution Report - ASTM to 422 r -••- I, II i II I I Ii I� I I� it r aoo O 8 - I � i 14+ � I � 500 100 10 1 GRAIN SIZE - mm 0 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 4.2 38.6 57.2 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 99.5 #100 97.4 #200 95.8 (no specification provided) Sample No.: 2700 Source of Sample: Location: B2 Sample #12 Checked By: A. Coyne Soil Description Sample #2700 - B2 Sample #12: Gray Silt Atterberq Limits (ASTM D 43181 PL= 26.5 LL= 33.3 Pl= 6.8 Classification USCS= ML AASHTO= A-4(0) Coefficients D85= 0.0141 D60= 0.0052 D50= 0.0044 D30= 0.0025 D15= D10= Cu= Cc= Date Tested: 7/27/2006 Tested By: A. Duong Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 50 to 51.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-29 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 •t 4 I;; • Ii. I j; 11 a .1 4 - Li_ 1 -t 4- 500 100 10 1 GRAIN SIZE - mm 0.1 0.01 0.001 % COBBLES % GRAVEL 0.0 20.6 % SAND 64.7 % SILT 14.7 % CLAY SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) 0.75 in. 100.0 0.625 in. 88.4 0.5 in. 86.0 0.375 in. 81.1 0.25 in. 79.9 #4 79.4 #10 78.1 #40 63.6 #100 22.3 #200 14.7 (no specification provided) Sample No.: 2700 Source of Sample: Location: B3 Sample #6 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. Soil Description Sample #2700 - B3 Sample #6: Light brown, Silty Sand with gravel Atterberq Limits (ASTM D 43181 PL= NT LL= NT P1= NT Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 11.7 D60= 0.393 D50= 0.317 D30= 0.196 D15= 0.0796 D10= Cu= cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 15 to 16.5 feet Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-30 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 ry 4 ono 8 E ZS 1 PERCENT FINER i, 1, I I 100.0 I' 0.375 in. II I i II 1 I 0.25 in. 90.5 1 l i 1 I I 1 #4 � t t ! i ;1 #10 •I i 1 #40 ; it , #100 88.6 ' #200 87.8 I I II! 1 I. J 1 r1 �--rY --i- It T -, i 1 - - - ..�. r VIII I i I' + — -, . -- +- -• : 1, 1'I 1!' -i I I I 11; I lig I. I I .. 1 }T }.t ' 1 I 1 II I1I r -r--r r _. ..i { _ --1— I 500 100 10 GRAIN SIZE - mm 0.1 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 9.5 2.7 87.8 SIEVE SIZE PERCENT FINER SPEC.' PERCENT PASS? (X=NO) 0.5 in. 100.0 0.375 in. 92.1 0.25 in. 90.5 #4 90.5 #10 90.5 #40 90.1 #100 88.6 #200 87.8 (no specification provided) Sample No.: 2700 Source of Sample: Location: B3 Sample #13 Checked By: A. Coyne Soil Description Sample #2700 - B3 Sample #I3: Gray, lean CLAY Atterberq Limits (ASTM D 43181 PL= 22.3 LL= 38.8 Pl= 16.5 Classification USCS= CL AASHTO= A-4(0) Coefficients D85= D60= D50= D30= D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder, A. Duong Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 50 to 51.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Anion Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-31 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 64.4 25.7 SIEVE SIZE PERCENT FINER SPEC.' PERCENT PASS? (X=NO) 0.75 in. 95.6 0.625 in. 95.6 0.5 in. 94.7 ,i I I I I 0.25 in. I I I #4 90.1 #10 86.9 I,I III I 1 76.2 #I00 II 1 I : 1 ,I #200 25.7 i�; • 1 I I ,, .1 I I ii j1 ! •I ' HI III 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 64.4 25.7 SIEVE SIZE PERCENT FINER SPEC.' PERCENT PASS? (X=NO) 0.75 in. 95.6 0.625 in. 95.6 0.5 in. 94.7 0.375 in. 93.0 0.25 in. 91.3 #4 90.1 #10 86.9 #40 76.2 #I00 36.3 #200 25.7 (no specification provided) Sample No.: 2700 Source of Sample: Location: B4 Sample #2 Checked By: A. Coyne Soil Description Sample #2700 - B4 Sample #2: Gray, Silty sand Atterberq Limits (ASTM D 4318) PL= NT LL= NT Pl= NT Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 1.40 D60= 0.294 D50= 0.230 D30= 0.108 D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-32 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 I I i 11 , 1._- - 1; 500 100 10 O O O O O O O O o O 3t it A it Y h GRAIN SIZE - mm 0.01 0.001 % COBBLES % GRAVEL SAND % SILT % CLAY 0.0 0.0 86.8 13.2 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 99.8 #40 97.5 #100 32.7 #200 13.2 (no specification provided) Sample No.: 2700 Source of Sample: Location: B4 Sample #5 Checked By: A. Coyne Soil Description Sample #2700 - 64 Sample #5: Light brown Silty sand Atterberq Limits (ASTM D 4318) PL= NT LL= NT Pl= NT Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 0.357 D60= 0.248 D50= 0.211 D30= 0.140 D15= 0.0816 D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 15 to 16.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-33 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 111. - 11 :+; ii I I 1. 1 i X11, rrt � � - 4 r-+ 1 --- -i.; _,id 1 1 500 100 10 1 GRAIN SIZE - mm 8 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 51.2 48.8 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 99.9 #40 98.9 #100 84.1 #200 48.8 (no specification provided) Sample No.: 2700 Source of Sample: Location: B4 Sample #9 Checked By: A. Coyne Soil Description Sample #2700 - B4 Sample #9: Light brown Silty sand Atterberq Limits (ASTM D 4318) PL= NT LL= NT P1= NT Classification USCS= SM AASHTO= A-4(0) Coefficients D85= 0.154 D60= 0.0911 D50= 0.0766 D30= D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 35 to 36.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-34 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 92.8 7.2 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 11 I 93.6 i #100 12.4 1 .-. .._... -._.1 I I I I I --a _1,.,-1-1-1.. _ _I -__ -�-- -_ -11-j-� __ _•, -_{ -,--i- 1 j1'I•tl 'I 1 . 0, 1 i i �+ I + I ;• 1i —; I 71 a 1 — 4 hI' t } I H. -H--I--1 • -1-� 1 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 92.8 7.2 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 93.6 #100 12.4 #200 7.2 (no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #2 Checked By: A. Coyne Soil Description Sample #2700 - B5 Sample #2: Light brown, poorly -graded Sand with silt Atterbern Limits (ASTM D 4318) PL= NT LL= NT PI= NT Classification USCS= SP -SM AASHTO= A-3 Coefficients D85= 0.390 D60= 0.300 D50= 0.269 D30= 0.208 D15= 0.160 D10= 0.109 Cu= 2.76 Cc= 1.33 Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-35 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 500 100 10 1 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES GRAVEL SAND % SILT % CLAY 0.0 0.0 91.5 8.5 SIEVE SIZE . - SPEC.* PERCENT i. } I .... r -r-t- 100.0 #10 100.0 #40 1 I- f ♦ I � . �L_- ♦ •• y- I III #200 8.5 � II II I I I I , I ; - - - - --- - -�-- - .u.;��—• !11 I - I - -, -- •I -y--- - - -- -- • ..- �- ---!--f II ---i-f-'--te-- --- -- -_.. ...... - III. ± I I 500 100 10 1 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES GRAVEL SAND % SILT % CLAY 0.0 0.0 91.5 8.5 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 97.6 #100 20.7 #200 8.5 (no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #4 Checked By: A. Coyne Soil Description Sample #2700 - B5 Sample #4: Light brown, poorly -graded Sand with Silt Atterberq Limits (ASTM D 4318) PL= NT LL= NT Pl= NT Classification USCS= SP -SM AASHTO= A-3 Coefficients D85= 0.370 060= 0.277 D50= 0.244 D30= 0.182 D15= 0.126 D10= 0.0920 Cu= 3.01 Cc= 1.29 Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 10 to 11.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Anton Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A -6b PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 - 0 0 n z u A O O O 44 O u u u 500 100 10 1 GRAIN SIZE - mm 0.1 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 77.1 22.9 SIEVE SIZE PERCENT FINER SPEC* PERCENT PASS? (X=NO) #4 100.0 • , 100.0 #40 100.0 #100 86.5 #200 I I I � I I I I I i i I i 1 . I _4_ 1 1._�-...-. I I I - . -4 L ._. j_ , I -. 11 I jl I }_ - .. ! -I 1 1- I - - 1 i -4 i I -t . '44 I -ti-}. 1..}11.,1 .. ,-.J;#: 1. 1 t II I: + L I I I j I ' I I I , j I I I 500 100 10 1 GRAIN SIZE - mm 0.1 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 77.1 22.9 SIEVE SIZE PERCENT FINER SPEC* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 100.0 #100 86.5 #200 22.9 (no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #6 Checked By: A. Coyne Soil Description Sample #2700 - B5 Sample #6: Light brown Silty Sand Atterberq Limits (ASTM D 4318) PL= NP LL= NV P1= NP Classification USCS= SM AASHTO= A-2-4(0) Coefficients D85= 0.148 D60= 0.112 D50= 0.100 D30= 0.0810 D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 20 to 21.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-37 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 II 3t R if V, 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 1.5 98.5 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 99.9 #100 99.3 #200 98.5 I I l ' 1 l I I li ; { t + I . 1 1 500 100 10 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT % CLAY 0.0 0.0 1.5 98.5 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 99.9 #100 99.3 #200 98.5 (no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #10 Checked By: A. Coyne Soil Description Sample #2700 - B5 Sample #10: Gray Silt Atterberq Limits (ASTM D 43181 PL= 26.5 LL= 33.0 PI= 6.5 Classification USCS= ML AASHTO= A-4(8) Coefficients D85= D60= D50= D30= D15= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 40 to 41.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-38 9 9 8 7 U) 8 w Ct 5 1— Q 4 w 3 2 1 0 c = - 0.4 ksf -1 -2 LEGEND: NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-1, Sample 9, Depth = 35 feet Soil Description: Gray Silt (ML) Phi = 4), measured angle of internal friction c = measured cohesion Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 30, 2007 For: Mr. Jawaid Amon 11-1 OTTO ROSENAU & ASSOCIATES, INC. ORA Project Number: 06-373 A-39 SHEAR STRESS (ksf) 9 9 8 7 6 5 4 3 2 0 c = - 0.7 ksf -1 2 LEGEND: NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-1, Sample 14, Depth = 55-56 feet Soil Description: Gray Silt with trace fine gravel (ML) Phi = 4), measured angle of internal friction c = measured cohesion Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 30, 2007 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-40 SHEAR STRESS (ksf) 9 • 9 8 • 7 6 5 4 3 2 c = 0.33 ksf 0 LEGEND: — - ;- • i 1 - .. Phi = 30.3' 7 0 1 2 3 4 5 16 8 9 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 3, Depth = 12 feet Soil Description: Silty fine Sand (SP -SM) Phi = (I), measured angle of internal friction c = measured cohesion 0 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 30, 2007 OTTO ROSENAU & --- ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-41 SHEAR STRESS (ksf) 9 8 7 6 5 4 3 2 c = 0.25 ksf 0 -1 -2 LEGEND: NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 5, Depth = 20 feet Soil Description: Dark gray Silty Sand (SM) Phi = 4), measured angle of internal friction c = measured cohesion Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 30, 2007 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-42 LEGEND: NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 9, Depth = 35 feet Soil Description: Gray Silt (ML) Phi = (I), measured angle of internal friction c = measured cohesion Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 30, 2007 "�`un OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-43 Final site grades should be sloped to drain away from foundation 3% Min. Slope — 12" of impermeable soil cover Roof drain - tightline Minimum 12 -inch wide zone of washed rock, fully - wrapped by geotextile fabric Non -woven geotextile fabric - Mirafi 140N or equivalent 4" diameter, rigid, perforated pipe Not to scale Notes: 0 0 0 • O�O�O o�1.•• • 0 0 00000 ::, 0 0 - i1 . 00000 - 0°000 • o-0 . • it 000 o°o000 1 • • 00000 a •, �1 00000° 0 0 0 �, o°o°o° k1 ., � 000000 • 0 ° 0°°0°0 0 - 1: 000000 '. • 0 0 0:0000000 0 4' - 1 LI bl c 1. • Li . 1 t Foundation Wall If required, extend overexcavation laterally to either side of footing to a width equal to overexcavation depth (e.g. 24" lateral extension for 24" overexcavation depth) 1. The bearing surfaces for all proposed foundation elements should be evaluated by an ORA representative to verify that the foundation subgrade soils are capable of providing the required allowable bearing capacity. 2. All pipes should be sloped to drain to an approved discharge point. 3. Washed rock used as drainage material should consist of inch to 14 inch washed rock. 4. All temporary excavations must be completed in accordance with the recommendations of the geotechnical report for this project. TYPICAL FOUNDATION DETAIL Project Name: La Tourelle Plat Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: August 27, 2007 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-44 Final grade 2' Minimum Overexcavation Depth Overexcavation Width 1 Building Width 18" Min. Width 18" Min Embedment 1H \ Note: The location of all features shown is approximate. TYPICAL BUILDING PAD OVEREXCAVATION Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 27, 2007 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-45 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section A — A' under Static Conditions and the Existing Site Conditions AEXO 8-29-07 6:57 270 _ 240 _ A Section Existing Conditions No EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.629 150 _ 120 0 1 1 ' 1 ' 1 ' 1 1 ' 1 1 30 60 90 120 150 180 210 240 X—AXIS (feet) Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-46 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section A — A' under Seismic Loading Conditions and the Existing Site Conditions AEX2G 8-29-07 6:58 270 _ 240 _ 150 _ 120 A Section Existing Conditions EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.297 -p' — SOIL 1 _P SOIL 2 ,-P1 0 30 60 90 120 150 X—AXIS (feet) 160 210 240 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-47 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section A — A' under Static Conditions and the Proposed Site Conditions APROO 8-29-07 6:59 270 _ 240 _ A Section Proposed Conditions No EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.628 150 _ 120 1 0 1 1 1 1 1 1 1 I 30 60 90 120 150 190 210 240 X—AXIS (feet) Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-48 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section A — A' under Seismic Loading Conditions and the Proposed Site Conditions APRO2G 8-29-07 7:00 270 _ 240 _ A Section Proposed Conditions EQ 90 most critical surfaces, MINIMUM BISHOP FOS = 1.298 150 _ 120 0 30 60 90 120 150 180 210 240 X—AXIS (feet) Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-49 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Static Conditions and the Existing Site Conditions BEXO 8-28-07 10:01 500 400 300 Q 200 100 8 Section Existing Conditions NO EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.462 0 100 200 300 400 500 600 700 800 X—AXIS (feet) Soil Unit Unit Weight Strength Moist (pct) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-50 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Seismic Loading Conditions and the Existing Site Conditions BEXZG 8-28-07 10:06 B Section Existing Conditions EQ 10 most critical surfaces, MINIMUM BISHOP FOS = .998 SOIL 1 0 100 200 300 400 500 X—AXIS (feet) 600 700 800 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-51 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Static Conditions and the Proposed Site Conditions (Upslope Area) BPROOA 8-29-07 7:14 500 _ 400 _ N 300 _ X <200 _ > 100 _ B Sect Prop Upper 2.5H:1 V Slope NOEQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.679 SOIL 3 (at fill slope) SOIL 1 0 I I I I I r I I 0 100 200 300 400 500 600 700 800 X—AXIS (feet) Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 3 125 130 50 34 A-52 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Static Conditions and the Proposed Site Conditions (Downslope Area) BROOD 8-28-07 11:16 500 _ 400 _ m 300 _ (11 Q 200 _ >- 100 _ 0 8 Sect Prop Lower 2H:1 V Slope No EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.459 SOIL 3 (at fill slope) 0 1 1 1 1 1 1 1 i 100 200 300 400 500 600 700 800 X—AXIS (feet) Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 3 125 130 50 34 A-53 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Seismic Conditions and the Proposed Site Conditions (Upslope Area) BPRO2GA 8-29-07 7:18 B Sect Prop Upper 2.5H:1 V Slope EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.260 SOIL 3 (at fill slope) 300 400 500 X—AXIS (feet) 600 700 800 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 3 125 130 50 34 A-54 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Seismic Loading Conditions and the Proposed Site Conditions (Downslope Area) BPRO2GB 8-28-07 10:19 500 400 m 300 N Q 200 100 B Sect Prop Lower 2H:1V Slope EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.211 0 100 200 SOIL 3 (at fill slope) SOIL 1 SOIL 2 1 300 400 500 X—AXIS (feet) 600 700 800 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 3 125 130 50 34 A-55 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section C — C' under Static Conditions and the Existing Site Conditions CEXD 8-2B-07 10:26 C Section Existing Conditions No EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.188 0 30 60 90 120 150 X—AXIS (feet) 180 210 240 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-56 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section C — C' under Seismic Loading Conditions and the Existing Site Conditions CEX2G B-28-07 10:30 270 240 m 210 N Q 180 >- 150 120 C Section Existing Conditions EQ 10 most critical surfaces, MINIMUM BISHOP FOS = .991 0 30 60 90 120 150 X—AXIS (feet) 190 210 240 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-57 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section C — C' under Static Conditions and the Proposed Site Conditions CPROD 8-28-07 10:32 270 240 210 Q 180 150 120 C Section Proposed Conditions No EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.664 0 30 60 90 120 150 X—AXIS (feet) 150 210 240 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-58 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section C — C' under Seismic Loading Conditions and the Proposed Site Conditions CPRO2G 8-2B-07 10:33 270 240 m210 <180 150 120 C Section Proposed Conditions EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.300 0 30 60 90 120 150 X—AXIS (feet) 180 210 240 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 200 28 A-59 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Seismic Loading Conditions and the Proposed Site Conditions (Upslope Area) with Liquefied Soil Conditions BPROLIOA 8-28-07 21:33 500 400 300 m X Q 200 100 B Sect Prop UPPER 2.5:1V SLOP EQ LIQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.657 SOIL 1 SOIL 3 (at fill slope) SOIL 2 SOIL 4 (liquefied) 1 0 100 200 300 400 500 X—AXIS (feet) 1 600 700 800 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 1000 28 3 125 130 50 34 4 105 115 800 0 A-60 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing La Tourelle Project XSTABL ANALYSIS at Section B — B' under Seismic Loading Conditions and the Proposed Site Conditions (Downslope Area) with Liquefied Soil Conditions BPROLIQB B-28-07 21!29 B Sect Prop Lower 2H:1V Slope EQ LIQ 10 most critical surfaces, MINIMUM BISHOP FOS = 1.102 SOIL 1 SOIL 3 (at fill slope) SOIL 4 (liquefied) 0 100 200 300 400 500 600 X—AXIS (feet) 700 800 Soil Unit Unit Weight Strength Moist (pcf) Saturated (pcf) c (psf) ?? (deg) 1 105 115 100 28 2 116 120 1000 28 3 125 130 50 34 4 105 115 800 0 A-61 Depth Below Ground Surface (ft) Factor of Safety Against Liquefaction B-1 0 1 2 3 4 5 6 7 0 10 Loose to medium dense Silty Fine Sand (SM) and Fine Sand with Silt (SP -SM). Becomes wet at about 2.3 feet. Stiff to hard Sit (ML). Moist to wet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983)and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-1 Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 27, 2007 "--1 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-62 Factor of Safety Against Liquefaction B-2 0 1 1 0 10- 20 F co 30 to .0 2 40 C9 0 50 60 - 70 - 80 2 3 4 5 6 L Loose to medium dense Silty Fine Sand (SM) and Fine Sand with Silt (SP -SM). Becomes wet at about 17.5 feet. Stiff to hard Silt (ML). Moist to wet. Note: 1. Liquefaction analysis completed in general accordance with "Seed's Simplified Procedure" as proposed by Seed (1971 and 1983)and updated by Youd et al. (2001). 2. The silt soils (fines content > 50%) are considered to be non -liquefiable. 3. Design PGA assumed to be 0.36 g ( PGA = SDS x 0.4). RESULT OF LIQUEFACTION ANALYSIS AT B-2 Project Name: La Tourelle Plat Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 27, 2007 --6m5-- OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-63 NOTES A-64 City of Tukwila Department of Community Development File Number 01 LAND USE PERMIT ROUTING FORM pq TO: ❑ Building . Planning , Public Works ❑ Fire Dept. ❑ Police Dept. ❑ Parks/Rec Project: t_ T ewl (---- Address: 5 1 6 o c- 4i— Sr D,,,,,,k - S DateResponse transmitted: requested by: i Staff coordinator: b Lj"`-'L. Date response received: Bis �.b‘A� COMMENTS Cv c4AA-k avt-Mc--d 6-\9)b - Site, 'rn 1 11HC l (9-v‘ 5 ❑ DRC review requested ❑ Plan submittal requested ❑ Plan approved Plan check date: Comments prepared by: 03/14/04 Minnie Dhaliwal City of Tukwila Planning Department 6200 Southcenter I3oulevard Tukwila, WA 98188 CIVIL ENGINEERING, LAND PLANNING, SURVEYING, ENVIRONMENTAL SERVICES RE: Second Resubmittal of Sensitive Area Study La Tourelle Property Permit No. L06-089 Our Job No. 12650 Dear Minnie: June 7, 2007 1 5.E aE1 i r" UUIYHVIUNI 1 Y COURIER DELIVERY DEVELOPMENT Per our telephone conversations in early April, ESA Adolfson has revised the Sensitive Area Study for the above-mentioned property. As you suggested, we have omitted the option of off-site mitigation and now propose only on-site mitigation. The site plan has been revised to reflect this change and the number of proposed lots has been changed to 15 lots. Sandra Whiting's concerns regarding groundwater hydrology have also been addressed in Section 5.1.2 of the Sensitive Area Study. We are submitting three copies of the revised study for your continued review and routing. It is our understanding that these revisions address all of the comments City of Tukwila's regarding the on-site and off-site wetlands received to date. Please contact me at this office if you have any questions or require additional information. Sincerely, 61tQQSF°-- Alexia D. Dorsch Assistant Planner ADD/pj 12650c.011.doc enc: As Noted cc: Joe Amon Ilon Logan, ESA Adolfson Tristan Peter-Contesse, ESA Adolfson Tom Barghausen, Barghausen Consulting Engineers, Inc. 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES 1 OLYMPIA, WA 1 TACOMA, WA 1 SACRAMENTO, CA 1 TEMECULA, CA www.barghausen.com LA TOURELLE DEVELOPMENT Sensitive Areas Study Prepared for: Mr. Jawad Amon March 2007 - Revised May 2007 r ESAAdolfson La Tourelle Sensitive Areas Study TABLE OF CONTENTS 1.0 INTRODUCTION 1 1.1 Project Overview 1 1.2 Project Background 1 2.0 METHODS 2 2.1 Review of Existing Information 2 2.2 Wetland Delineation Classification, and Rating 2 2.3 Wetland Classification and Rating 3 2.4 Wetland and Buffer Function Assessment 4 3.0 FINDINGS 5 3.1 Description of Project Area 5 3.1.1 Watershed Setting 5 3.1.2 Topography, Soils, Vegetation, and Land Use 5 3.2 Wetland Descriptions 6 3.2.1 Wetland A 6 3.2.2 Wetland B 7 3.2.3 Wetland C 7 3.3 Wetland Ratings 8 3.4 Corps Jurisdictional Determination 9 3.5 Streams and Other Drainage Features .... 9 3.6 Wildlife Habitat Types and Functions 9 3.7 Wildlife Observations 10 3.8 Listed and Priority Species 10 4.0 IMPACTS 10 4.1 Wetland Impacts 10 4.2 Stream Impacts 11 4.3 Buffer Impacts 11 4.4 Wildlife Habitat Impacts 11 5.0 MITIGATION 12 5.1.1 Avoidance 12 5.1.2 Minimization 13 5.2 Compensatory Mitigation 13 5.2.1 Wetland Creation and Enhancement 14 5.2.2 Wetland Buffer Reduction and Enhancement 15 5.2.3 Goals and Objectives 16 5.2.4 Performance Standards 16 6.0 MONITORING 17 6.1.2 Maintenance 18 6.2 Contingency Plan 18 7.0 LIMITATIONS 19 8.0 REFERENCES 20 FIGURES AND PHOTOGRAPHS 1 ESA Adolfson page -i March 2007 Revised May 2007 La Tourelle Sensitive Areas Study APPENDIX A: METHODS USED TO EVALUATE WETLAND CHARACTERISTICS 1 APPENDIX B: COMMON AND SCIENTIFIC NAMES OF PLANTS AND THEIR WETLAND INDICATOR STATUS 1 APPENDIX C: DATA SHEETS 1 ESA Adolfson page -ii March 2007 Revised May 2007 La Tourelle Sensitive Areas Study 1.0 INTRODUCTION At the request of Mr. Jawaid Amon, ESA Adolfson (Adolfson) performed wetland delineations and prepared this Sensitive Areas Special Study for the La Tourelle Plat Development, located in the City of Tukwila, Washington. All rights -of -entry to the subject property for the purpose of conducting this study were granted by Mr. Amon, who is the property owner. The boundaries of the study area were established based on discussions with Mr. Amon and a parcel map. This report has been written to meet the requirements of the Sensitive Areas Special Studies process described under TMC Chapter 18.45.040. 1.1 Project Overview The proposed La Tourelle development consists of two parcels (#5379200006 and #5379200005) totaling 3.6 acres located within Section 26, Township 23 North, Range 4 East, in Tukwila, Washington. Mr. Amon intends to develop the property with 15 single family lots with a central access road and cul de sac. The triangular-shaped property is bounded by South 160th Street to the south, 53rd Avenue South to the east, and a City of Seattle right-of-way and South 159th Street to the north (Figure 1). The site is situated in a residential area, within the Gilliam Creek Basin of the City of Tukwila. The site is currently undeveloped, containing mostly deciduous forest and shrubs (Photo 1). Steep slopes characterize much of the site's northern area, while the middle and southern portions of the site are generally flat or gently sloping. The southern edge of the site slopes steeply to 53`d Avenue South. 1.2 Project Background Adolfson performed a wetland delineation on the Amon property on October 4, 2005, and produced the Amon Property Wetland Delineation Report in January 2006. Adolfson delineated three wetlands in the vicinity of the proposed project. Two wetlands (Wetlands A and B) were identified on the property. The third wetland, Wetland C, is located north of the property within a City of Seattle right-of-way; a small portion of this wetland extends onto the Amon property. A watercourse associated with Wetland C was also identified. Wetland boundaries were professionally surveyed by Mead, Gilman and Associates of Woodinville. The City of Tukwila Department of Community Development verified the wetland boundary on February 8, 2007, and concurred with the surveyed boundaries. A preliminary plat application for the La Tourelle development is being prepared for submittal to the City. The City of Tukwila requires a Sensitive Areas Special Study for development proposals that may impact a sensitive area and/or its buffer (TMC 18.45.040). ESA Adolfson Page 1 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study 2.0 METHODS 2.1 Review of Existing Information A review of existing literature, maps, and other materials was conducted to identify wetlands or site characteristics indicative of wetlands on the subject property. These sources indicate the likelihood of the presence of wetlands; actual wetland determinations must be based upon data obtained from field investigations. Several documents were reviewed: • The U.S. Geological Survey 7.5 minute Topographic Map, Des Moines quadrangle. 1995. King County GIS revised 2004. • The Soil Survey of King County Area, Washington. U.S. Department of Agriculture Natural Resources Conservation Service. 2003. King County GIS revised 2004. • The National Wetland Inventory, Des Moines. U.S. Fish and Wildlife Service. 1988. • Hydric Soils of the State of Washington. Natural Resources Conservation Service. 1995. • The King County Sensitive Areas Folio. King County Department of Surface Water Management. 1990. • The City of Tukwila Wetland/Watercourse and Buffer Map. City of Tukwila Department of Community Development. July 15, 2004. • The Washington State Department of Fish and Wildlife Priority Habitat and Species Map. 2005. 2.2 Wetland Delineation Classification, and Rating Methods defined in the Washington State Wetlands Identification and Delineation Manual (Ecology, 1997), a manual consistent with the U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), were used to determine the presence and extent of wetlands on the subject property. Washington State and all local governments must use the state delineation manual to implement the Shoreline Management Act and/or the local regulations adopted pursuant to the Growth Management Act. The methodology outlined in the manual is based upon three essential characteristics of wetlands: (1) hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three characteristics must all be present in order to determine that an area is a wetland (unless problem areas or atypical situations are encountered). The "routine on-site determination method" was used to determine the wetland boundaries. The routine method is used for areas equal to or less than five acres in size, or for larger areas with relatively homogeneous vegetative, soil, and hydrologic properties. Formal data plots were established in areas of relatively homogeneous vegetation, where information regarding each of the three wetland parameters (vegetation, soils, and hydrology) was recorded. Dominant herbs and saplings/shrubs within a five-foot radius, and dominant trees and woody vines within a 30 -foot radius, from the data plot center were recorded on the data form (Ecology, 1997). This information was used to distinguish wetlands from non -wetlands. If wetlands were determined to be present on the subject property, the wetland boundaries were ESA Adolfson Page 2 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study delineated. Wetland boundaries were identified with sequentially numbered colored flagging imprinted with the words WETLAND DELINEATION. Data plot locations were also marked with colored flagging. The methods used to assess wetland characteristics are described in greater detail in Appendix A. A list of plant species observed on-site is presented in Appendix B. 2.3 Wetland Classification and Rating Two classification systems are commonly used to describe wetlands. The hydrogeomorphic (HGM) system describes wetlands in terms of their position in the landscape and the movement of water in the wetland (Brinson, 1993). The U.S. Fish and Wildlife Service classification system (Cowardin et al., 1979) describes wetlands in terms of their vegetation communities; these include, for example, emergent, scrub -shrub, and forested community types. La Tourelle Sensitive Areas Study 2.4 Wetland and Buffer Function Assessment Wetlands and buffers provide valuable benefits to the environment and society. Because detailed scientific knowledge of wetland functions is limited, evaluations of the functions of individual wetlands are somewhat qualitative and dependent upon professional judgment. For this project, wetland functions were assessed using methods adapted from the Washington State Wetland Function Assessment Method (WFAM) (Hruby et al., 1999). The methods are based on the hydrogeomorphic (HGM) classification for wetlands, which categorizes wetlands into groups that function in similar ways based on the geomorphic and hydrologic characteristics. The following 15 functions were assessed: Functions Related to Water Quality Improvement • Potential for Removing Sediment • Potential for Removing Nutrients • Potential for Removing Heavy Metals and Toxic Organics Functions Related to Hydrology (Water Quantity) • Potential for Reducing Peak Flows • Potential for Decreasing Downstream Erosion • Potential for Recharging Groundwater Functions Related to Habitat Suitability • General Habitat Suitability • Habitat Suitability for Invertebrates • Habitat Suitability for Amphibians • Habitat Suitability for Anadromous Fish • Habitat Suitability for Resident Fish • Habitat Suitability for Wetland - associated Birds • Habitat Suitability for Wetland - associated Mammals • Native Plant Richness • Potential for Primary Production and Organic Export TMC 18.45.080 defines the purpose of buffer areas as protecting the integrity, functions, and values of a wetland area. Buffer functions were also assessed using WFAM methods. Wetland buffers are intended in general to: 1. Minimize long-term impacts of development on properties containing wetlands; 2. Protect wetlands from adverse impacts during development; 3. Preserve the edge of the wetland and its buffer for its critical habitat value; 4. Provide an area to stabilize banks, to absorb overflow during high water events, and to allow for slight variation of aquatic system boundaries over time due to hydrologic or climatic effects; ESA Adolfson Page 4 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study 5. Reduce erosion and increased surface water runoff; 6. Reduce loss of or damage to property; 7. Intercept fine sediments from surface water runoff and serve to minimize water quality impacts; and 8. Protect the sensitive area from human and domestic animal disturbances. 3.0 FINDINGS The following sections describe the results of the field investigation conducted by Ilon Logan and Janice Martin within the Amon property on October 4, 2005. These sections describe the three on-site wetlands, one of which extends off-site, upland habitats, and wildlife observations. Five data plots were established within relatively uniform areas of vegetation on the property. Data sheets for each of the formal data plots evaluated for this project are provided in Appendix C. 3.1 Description of Project Area 3.1.1 Watershed Setting The property is located toward the southern end of the Puget Trough within the Green River drainage basin and Water Resource Inventory Area (WRIA) #09. Within WRIA #09, the project lies in the Gilliam Creek basin (WRIA #09-0032) and within the Crystal Springs subbasin. The Crystal Springs subbasin, covering 242 acres, receives most of its drainage from groundwater seeps on the northeast slope of McMicken Heights near the project area. A culvert conveys Crystal Springs underneath I-5 to a drainage ditch that is located between Southcenter Parkway and I-5. The subbasin is bounded on the north by SR 518, on the south and west by the ridge crest of McMicken Heights, and on the east by Southcenter Mall (Herrera Environmental Consultants Inc., 2001). 3.1.2 Topography, Soils, Vegetation, and Land Use The U.S. Geological Survey (USGS) Des Moines quadrangle (USGS, 1995) shows the moderate to sleep slopes on the property, which slopes down toward the northeast. The property flattens out between steeper areas located on benches or ridges (Figure 2). The National Wetlands Inventory (NWI) map shows no wetlands on the property (Figure 3). Additionally, the City of Tukwila Wetland/Watercourse and Buffer Map (2004) does not indicate any wetlands on-site but does show a watercourse flowing eastward in a City right-of-way north of the property (Figure 4). The Soil Survey of King County (King County GIS, 2004) maps the entire property as Arents, Alderwood material (AmC) (Figure 5). Arents, Alderwood soil has convex slopes from 6 to 15 percent, with some at 30 percent. It is a gravelly sandy loam that is moderately well drained, has variable permeability, and moderate to severe erosion hazard (Snyder, et al., 1973). Arent, Alderwood material is a considered non -hydric (non -wetland) soil (NRCS, 1995). ESA Adolfson Page 5 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study Upland vegetation within the property includes big leaf maple (Acer macrophyllum) in the canopy layer, with English ivy (Hedera helix), and Himalayan blackberry (Rubus discolor) in the understory (Photo 7). Red alder (Alnus rubra), Indian plum (Oemleria cerasiformis), reed canarygrass (Phalaris arundinacea) and other upland grasses such as orchardgrass (Dactylis glomerata) are also present. Salmonberry (Rubus spectabilis), Cooley's hedge -nettle (Stachys cooleyae), giant horsetail (Equisetum telmateia), and Himalayan blackberry are dominant within wetland areas on the property. Land use in the property vicinity includes residential housing and undeveloped land. Crystal Springs Park, a City owned park, is adjacent to the property's northwest corner, and a City of Seattle right-of-way for the Bow Lake water pipeline borders the property to the north. 3.2 Wetland Descriptions Three wetlands (Wetlands A, B, and C) occur on the property. Wetland C lies largely off-site within a City of Seattle utility right-of-way north of the property (Figure 6). The characteristics of the wetlands are summarized in Table 2 and discussed below. 3.2.1 Wetland A Location, Size, and Geomorphic Setting. Wetland A (3,070 sf) is a palustrine scrub -shrub (PSS) wetland with no outlet (Photo 2). It is located on the west -central portion of the property, on a gentle north -facing slope that decreases to a shallow depression. Hydrology, Soils. and Vegetation. Data Plot 3 (DP -3) characterizes Wetland A. The wetland appears to be an isolated wetland that is seasonally saturated and inundated due to high groundwater and precipitation. Indicators of wetland hydrology included saturated soils at the surface of the soil pit, and free water at 11 inches below the surface. Soils investigation found a surface horizon extending to seven inches below ground surface consisting of a black (10YR 2/1) sandy clay loam. From seven to 16 inches in depth, the soils observed were a greenish gray 5/10Y (gleyed) sandy loam with brownish yellow (10YR 6/8) mottles. Giant horsetail (Equisetum telmateia, FACW), Cooley's hedge -nettle (Stachys cooleyae, FACW) and salmonberry (Rubus spectabilis, FAC+) are the dominant plant species present in Wetland A. Other vegetation present included skunk cabbage (Lysichitum americanum, OBL) and lady fem (Athyrium filix femina, FAC+). Functions and Values. Wetland A provides some water quality improvement function because it is a depression with no outlet, and most of the wetland contains persistent vegetation. However, the wetland is generally flat and thus provides minimal detention of surface drainage. The wetland provides some reduction of flood flows and erosion because it is located within a depression with no outlet, but this function is also minimized by the wetland's generally flat topography and small size. The scrub -shrub vegetation and undisturbed upland buffer combine to perform wildlife habitat functions. However, the presence of invasive vegetation (Himalayan blackberry) and lack of habitat features (e.g., snags, downed wood) decrease the wetland's ability to provide higher habitat functions. Overall, this wetland provides low function due to its position on a slope, degraded nature due to invasive species and small size. ESA Adolfson Page 6 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study The buffer of Wetland A is relatively undisturbed and provides a level of function similar to the wetland. The presence of invasive species, primarily Himalayan blackberry, decreases the native plant species richness, and the buffer is lacking dense herbaceous vegetation that would provide water quality improvement functions. 3.2.2 Wetland B Location, Size, and Geomorphic Setting. Wetland B (1,562 sf) is a depressional palustrine scrub -shrub (PSS) wetland with no apparent outlet (Photo 3). This wetland is located in a linear depression near the center of the property, and is seasonally saturated and occasionally inundated. Hydrology, Soils, and Vegetation. Data Plot 1 (DP -1) characterizes Wetland B. The wetland appears to be an isolated wetland that is seasonally saturated due to high groundwater and precipitation. Surface water likely infiltrates after storm events. No standing water or other evidence of surface ponding was observed during the field investigation. Based on the presence of hydrophytic vegetation and hydric soils during our field delineation in October 2005, and due to the wetland's location in a depressional area, wetland hydrology would likely be present during the growing season. Soils in this data plot were a very dark brown (10YR 2/2) sandy loam to a depth of eight inches (Photo 4). From eight to 16 inches below the soil surface, the soils were a dark grayish -brown (2.5Y 4/2) loamy sand with distinct dark yellowish -brown (10YR 4/6) mottles. Wetland vegetation is dominated by Japanese knotweed (Polygonum cuspidatum, FACU*), salmonberry (Rubus spectabilis, FAC+), and Cooley's hedge -nettle (Stachys cooleyae, FACW). Himalayan blackberry (Rubus discolor, FACU) occurs along the hillside and partially within the wetland. Functions and Values. This wetland occurs in a linear depression and is seasonally saturated and occasionally inundated. Wetland B provides similar functions to Wetland A, but at lower levels due to its degraded conditions. Both water quality improvement function and reduction of flooding and erosion are limited due to the small size of the wetland and lack of detention area. Wetland B contains invasive vegetation (Himalayan blackberry, Japanese knotweed, and English ivy) which compromise the ability of the wetland and its buffer to provide native species richness and wildlife habitat function. The presence of English ivy in the wetland buffer results in a lower level of water quality improvement function because the species is aggressive and outcompetes native herb species. Overall, this wetland provides low function due to invasive species, small size and degraded nature. 3.2.3 Wetland C Location, Size, and Geomorphic Setting. Wetland C (4,026 sf) is a palustrine, emergent and scrub -shrub (PEM/PSS) wetland. A narrow drainage channel extends eastward from known springs located northwest of the Amon Property (Photo 5). The majority of the drainage channel is within Wetland C with a portion extending east of the wetland boundary. All but 16 square feet of the wetland are located off-site, within a City of Seattle utility right-of-way for the Bow Lake water pipeline. ESA Adolfson Page 7 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study Hydrology, Soils, and Vegetation. Data Plot 4 (DP -4) characterizes Wetland C. Soils were saturated to the surface within DP -4. A narrow spring -fed drainage channel extends east of this wetland. Soils in DP -4 were a very dark brown (10YR 2/2) sandy clay loam from zero to 10 inches below the soil surface. From 10 to 16 inches in depth, the soils were a black (2.5Y 4/1) sandy loam with mottling. The mottles (medium, common and distinct) were dark yellowish brown (10YR 4/4). The odor of sulphur was present within the data plot, which is also indicative of redoximorphic conditions. Wetland C vegetation is dominated by reed canarygrass (Phalaris arundinacea, FACW) and giant horsetail. Other species observed included small -fruited bulrush (Scirpus microcarpus, OBL), salmonberry, and red alder. Functions and Values. Wetland C provides limited water quality improvement functions because it contains dense herbaceous vegetation that slows surface water flows and traps pollutants. It provides minimal stormwater detention because it is situated on a slope and surface drainage flows through a narrow channel that continues east of the wetland. Much of the wetland vegetation is mowed because it is within a utility right-of-way, which decreases wildlife habitat function. Overall, Wetland C provides limited functions because it is regularly disturbed and contains multiple invasive species. Similarly, the portion of the buffer of Wetland C that is within the right-of-way is regularly mowed and contains low growing grass and herbaceous species. The portion of the buffer on the Amon property is composed of big leaf maple and red alder trees with Himalayan blackberry in the understory. This area provides wildlife habitat function and protects the edge of Wetland C. The buffer also reduces erosion and intercepts fine sediments and pollutants from surface water runoff. 3.3 Wetland Ratings The City's wetland rating criteria are contained in TMC Chapter 18.45.080 and described in Section 2.2. Wetlands A, B and C meet the criteria for Type 3 wetlands because (1) they do not meet the criteria for Type 1 or 2 wetlands, and (2) they are greater than 1,000 square feet and less than one acre in size with two or fewer wetland classes. ESA Adolfson Page 8 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study Table 2. Wetland Classifications and Ratings A 3,070 sf Depressional PSS West central portion of property on north facing slope Type 3 50 feet B 1,562 sf Depressional PSS Near center of property Type 3 50 feet c 4,026 sf Depressional PSS/PEM Mostly off-site (16 sf on applicant property) Type 3 50 feet A Wetland Classifications (Cowardin et. al., 1979 and Brinson 1993): PEM-Palustrine Emergent, PSS-Palustrine Scrub Shrub. 3.4 Corps Jurisdictional Determination As requested by the City during the pre -application meeting, a jurisdictional determination by the US Army Corps of Engineers (Corps) was conducted for Wetlands A and B. Mr. Amon submitted a request for jurisdictional determination to the Corps on February 9, 2007. The Corps conducted a site visit on March 20, 2007 and determined that both Wetlands A and B meet the definition of isolated wetlands and are not under Corps jurisdiction. In 2002, Corps jurisdiction over isolated waters under the Clean Water Act was eliminated in light of the decision of the United States Supreme Court in Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, (the SWANCC decision). 3.5 Streams and Other Drainage Features A small spring -fed stream enters Wetland C from the west via a culvert. The drainage flows east through the wetland, along compacted soils (Photo 6). The majority of the watercourse falls within Wetland C. According to TMC 18.15.100, this is a Type 4 watercourse that requires a 50 - foot buffer. The watercourse buffer falls within the 50 -foot buffer of Wetland C. 3.6 Wildlife Habitat Types and Functions Upland forest habitats occur across the property. Big leaf maple (Acer macrophyllum) is dominant in the canopy layer, with red alder and Indian plum also present. Shrub layers consist primarily of English ivy and Himalayan blackberry. Dominant grasses include reed canarygrass and orchardgrass (Dactylis glomerata). Habitat elements observed in upland areas include large trees, shrub thickets, and snags, although functions of this habitat are reduced due to the dominance of non-native English ivy and Himalayan blackberry. Habitat functions of the on-site wetlands are somewhat compromised by invasive species, as discussed in the wetland descriptions above (Section 3.2). ESA Adolfson Page 9 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study 3.7 Wildlife Observations Species observed during the field investigations included Pacific tree frog, American robin, black -capped chickadee, and Steller's jay. Other species of birds, mammals, reptiles, and amphibians typical of Puget Sound lowland deciduous forest are also expected to use habitats on the property. 3.8 Listed and Priority Species The Washington State Department of Fish and Wildlife (WDFW) provides maps with locations of priority habitats and species. No priority habitats or species are documented on or in the vicinity of the property. Two small open water emergent wetlands occur within one mile of the property, in addition to the Green River and two areas designated as urban natural open space. No priority wildlife species were observed on the site during field investigations in October 2005. 4.0 IMPACTS The La Tourelle development will result in direct impacts to Wetland B and the buffer of Wetlands A and B. The project involves constructing 15 single-family lots, a central access road and cul-de-sac, and associated infrastructure for water, sewer, power, and gas services. 4.1 Wetland Impacts Due to the constraints of steep slopes and upland forest in the western portions of the site, in addition to the shape of the site and location of access points, it is not possible to completely avoid wetland impacts. The proposed project will impact all of Wetland B, which is 1,562 square feet (0.04 acre) (Table 3). This wetland is located near the center of the site, where proposed lots 5, 6, and 7 would be located (Figure 7). Wetland B is a Type 3 PSS depressional wetland with no outlet. Wetland B functions similarly to Wetland A, but at lower levels. Both the water quality improvement function and the capacity for flood reduction are limited in this wetland due to the small size of Wetland B. ESA Adolfson Page 10 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study Table 3. Summary of Wetland Impacts A 3,070 N/A None B 1,562 Lots 5, 6 and 7 1,562 c 4,026 N/A None Total Impact 1,562 4.2 Stream Impacts No impacts to the watercourse associated with Wetland C are proposed as part of the La Tourelle project. In addition, there will be no impacts to Wetland C that might influence the existing hydrology of the watercourse. 4.3 Buffer Impacts In addition to impacting Wetland B and its buffer, the proposed project will impact 5,003 square feet of the buffer associated with Wetland A. The southern and eastern portions of the buffer would be reduced to accommodate construction on lots 10 and 11 (see Figure 8). Wetland A is a Type 3 depressional PSS wetland with a 50 -foot buffer. The buffer of Wetland A provides functions and values similar to those of the wetland itself, including water quality improvement for untreated stormwater runoff. The buffer consists of undeveloped forest that provides habitat for birds, small mammals, and amphibians as well as an undisturbed connection to the wetland. Buffer functions are reduced due to the presence of nonnative, invasive species, including Himalayan blackberry and English ivy, which out compete native plant species. 4.4 Wildlife Habitat Impacts The proposed site design will remove upland forest, wetland, and associated buffers that provide habitat for wildlife. Upland forest and steep slopes on the northwestern portion of the property will be avoided. Wildlife habitat functions currently provided by Wetlands A and B will be replaced by the proposed landscaping and the planting of trees as required by the City of Tukwila tree replacement code requirements. As discussed previously, habitat functions of Wetlands A and B are somewhat compromised due to the presence of invasive species and lack of habitat features. Upland habitats have also been colonized by invasive species and are functioning at a reduced level. Wildlife using impacted areas may be displaced to adjacent suitable habitats within the property that are being preserved as Sensitive Areas. Undisturbed habitats that are not currently developed are also present in the vicinity of the site, such as Crystal Springs Park north of the property. ESA Adolfson Page 11 March 2007 Revised May 2007 ' La Tourelle Sensitive Areas Study 5.0 MITIGATION emergent vegetation; (3) other disturbed wetland; or (4) existing degraded wetland. 5.1.1 Avoidance The site design avoids impacts to Wetland A and the majority of its buffer, as well as Wetland C and the associated watercourse. Project engineers reconfigured the site layout during multiple ESA Adolfson Page 12 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study revisions to avoid wetland and buffer impacts to Wetland A, while retaining project viability. Due to the site constraints, including the property shape, location of access points, and upland forest and steep slopes covering a portion of the property, impacts to Wetland B and its associated buffer cannot be avoided. 5.1.2 Minimization Project engineers have made efforts to further minimize direct impacts to wetlands and buffers after avoiding direct impacts to Wetland A. Lot lines and access road location were configured so as to minimize buffer impacts to the greatest extent possible while still maintaining lot size and dimension requirements established by the City. These alterations will limit buffer impacts to 5,003 square feet and prevent impacts to the rest of the wetland area. Impacts to Tract 999 and its upland forest are also minimized. In terms of indirect impacts, no development is proposed upslope of the Wetland A and thus the current sources of wetland hydrology (groundwater seeps, surface runoff) will not be disturbed. Cross slope and downslope of the mitigation area, the project proposes to maintain the current natural slopes and grade angles. Where cut slope walls are proposed, a PVC moisture barrier, compacted glacial till soils, or other impermeable material, will be installed so not to remove downslope groundwater pressure or drain upslope areas. Measures to be implemented to minimize impacts during construction include: • Conducting a pre -construction meeting on-site with the construction contractor and a professional biologist to discuss the construction sequence. • Clearly marking the limits of the construction area with orange barrier fencing. This type of barrier reduces the potential for heavy equipment to damage vegetation and soil outside the construction area, particularly within the adjacent forest and wetland. • Establishing temporary erosion and sedimentation control measures and BMPs, including silt fences, sediment rolls, and straw bales to prevent suspended particles from leaving the construction zone. The contractor will be responsible for inspection of all erosion control measures and will repair any damage to the erosion control structures, as needed. • Locating staging areas and stockpile sites outside the wetlands and the buffers. • Maintaining erosion control measures throughout the site until bare soils have been successfully vegetated and approved by a professional biologist. 5.2 Compensatory Mitigation To mitigate for the direct impacts to wetlands and buffers caused by site development, the project proposes to enhance 3,070 square feet of existing wetland and create 808 square feet of wetland. The project also proposes to set aside 5,056 square feet of additional buffer area and enhance 2,750 square feet of buffer. Each mitigation element is summarized in Table 4 and described in detail in the following sections. Table 4. On -Site Mitigation Summary ESA Adolfson Page 13 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study b � �4a"✓�a�. a` �+,1' �,y��„�� 2 �Ii1��.1Ai4t� � 'hiY ��„„. � h"4 A 0 1.5:1 (creation) 3:1 (enhancement) Creation of 808 square feet of wetland Enhancement of 3,070 square feet of wetland (Wetland A) B 1,562 Total1 562 5.2.1 Wetland Creation and Enhancement The 1,562 square feet of direct wetland impacts would be mitigated using two methods: wetland creation and wetland enhancement. Wetland creation would be conducted at a mitigation ratio of 1.5:1, as required by the City of Tukwila for Type 3 wetlands (TMC 18.45.090 D2). Wetland enhancement is proposed at a mitigation ratio of 3:1. Figure 8 is a conceptual enhancement and restoration plan that shows the proposed mitigation and planting details. The project would create 808 square feet of additional wetland through minimal grading and planting native species adapted to wet conditions (Table 5). The creation area is downslope, immediately north and northwest of Wetland A and will be an extension of the existing wetland. The intent is to expand the area of Wetland A, which is currently primarily dominated by salmonberry. Table 5: Planting List for Wetland Creation A�C���f{_ h 4 riu r1 '....'3�-F., "r= Thuja plicata western red cedar Tree Cornus sericea red osier dogwood Shrub Rubus spectabilis salmonberry Shrub Salix sitchensis Sitka willow Shrub Rosa pisocarpa clustered wild rose Shrub Tolmeia menziesii pig -a -back plant Emergent Athyrium filix femina lady fern Emergent To protect and improve the functions provided by Wetland A, the wetland would be enhanced (3,070 square feet) (Figure 8). Native vegetation in the wetland is currently composed of salmonberry, lady fern and skunk cabbage. However, these species are gradually becoming out competed by invasive species, including Himalayan blackberry, English ivy, and English holly. These nonnative species are providing dominant cover in much of the wetland. No tree species are present and there are areas of bare ground. Removal of these invasive species and planting native trees and shrubs amongst the existing salmonberry would restore and enhance Wetland A. The enhanced wetland would provide additional water quality improvement function, wildlife habitat value, and increased plant species diversity. A list of plantings is included as Table 6. ESA Adolfson March 2007 Revised May 2007 Page 14 La Tourelle Sensitive Areas Study 5.2.1.1 Grading/Soils Soils in the wetland creation area would be excavated to approximately one foot below existing wetland grade. The top six inches of topsoil would be stockpiled. During construction, the wetland would be over -excavated by six inches to allow for six inches of topsoil to be placed in the created wetland. Grading activities would be conducted in a careful manner so as not to disturb the existing wetland (Wetland A). 5.2.1.2 Hydrology Water supply to the wetland creation and enhancement area would primarily come from existing groundwater seeps on the slope. The seepage is currently expressed at the surface within Wetland A. Surface water runoff from adjacent upland areas and precipitation would also contribute water to the mitigation area. Water is expected to be temporarily detained in the mitigation area and would ultimately infiltrate. Table 6: Planting List for Wetland Enhancement .per p .k f � . V}viE Vs T" 3 9r t"`ac f' Vtiai on Na Thuja plicata western red cedar Tree Cornus sericea red osier dogwood Shrub Rose pisocarpa clustered wild rose Shrub Salix sitchensis Sitka willow Shrub Tolmeia menziesii pig -a -back plant Emergent Within both the creation and enhancement areas, trees and shrubs would be planted from one - gallon or two -gallon containers, except for willow, which would be stakes or whips. A native seed mix would also be applied to stabilize the soils and reduce the potential for weedy species establishment. A temporary irrigation system would be used, if needed, during the dry summer months or during periods of unusually low precipitation for the first one to two years following installation. Non-native plant species would be controlled throughout the monitoring period (discussed below) to allow the planted species to become established. 5.2.2 Wetland Buffer Reduction and Enhancement The 5,003 square feet of buffer impacts would be mitigated through buffer enhancement and buffer addition within the mitigation area identified on Figure 8. Due to site constraints, two of the 15 lots (Lots 10 and 11) must be constructed within a portion of the standard 50 -foot buffer of Wetland A on the eastern side. Every reasonable effort was made by project engineers to configure the lot lines and access road to minimize these impacts. However, in order to meet the City's minimum lot size and dimension limit for Lot 11, retaining walls are required to maintain slope stability. The TMC 18.45.080 G allows up to a 50% reduction of standard buffer width with enhancement, therefore allowing the 50 -foot buffer of Wetland A to be reduced to 25 feet. The project proposes to reduce the buffer along the eastern side of Wetland A and the wetland creation area ESA Adolfson Page 15 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study to 25 feet. However, in one location adjacent to Lot 11, the retaining wall must be located less than 25 feet from the most southeastern point of Wetland A (approximately 13 feet). Project engineers analyzed the site layout in detail and adjusted the wall position and angle to the furthest point possible while maintaining slope stability and lot size. The project proposes to enhance the remaining buffer area by removing invasive species, retaining existing native plants and planting additional native species. The intent is to provide enhanced wildlife habitat for birds, small mammals, and amphibians as well as protect Wetland A from human disturbance. As shown on Figure 8, approximately 2,750 square feet of buffer would be enhanced. A list of plantings is included as Table 7. The project also proposes to offset the 5,003 square feet of reduced buffer with approximately 5,056 square feet of additional buffer set aside in the sensitive area tract as part of the overall mitigation area. The additional buffer areas are located in three locations shown on Figure 8. The buffer of Wetland A and the mitigation area would provide the same functions as the existing buffer, including water quality improvement for untreated stormwater runoff and wildlife habitat. Table 7: Planting List for Buffer Enhancement a - L1 .'";.. T.-..� JC .f` r ^k oLiY on ...,.:.. Pseudotsuga menziesii Douglas -fir Tree Corylus cornuta Beaked hazelnut Shrub Mahonia aquifolium tall Oregon grape Shrub Holodiscus discolor oceanspray Shrub Rubus parviflorus thimbleberry Shrub 5.2.3 Goals and Objectives The goal of this mitigation plan is to offset wetland impacts through creation of wetland adjacent to existing wetland, and enhancement of the existing wetland to restore functions and values. Mitigation for wetland and buffer affected by project construction should increase the overall wildlife habitat within the project area. To compensate for impacts to wetland, wetland area would be created or enhanced at the area ratios required by the City. The proposed creation area is northeast of Wetland A and the enhancement area is within Wetland A. The two areas would be planted with native species that enhance the wildlife habitat value of the wetland. Therefore, the objectives for the wetland buffer enhancement effort are to increase the diversity of native plants and provide wildlife habitat. 5.2.4 Performance Standards Performance standards have been established to meet the mitigation goals. For this project, the mitigation plan will be considered successful if the created and enhanced areas meet the following criteria: • Installed plant survival of 90% through the first growing season; ESA Adolfson Page 16 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study • At least 80% survival of planted trees, shrubs, and herbaceous cover during the second and third monitoring years; • Not more than 15 percent cover of non-native invasive species in the mitigation areas during each year of the five-year monitoring period; and • Water at or near the soil surface for at least 30 days in the growing season in the wetland creation area. Hydric soils, which generally take at least 10-20 years to form, would not be expected to occur in the wetland creation area during the five-year monitoring period. It is assumed that if the hydrologic performance standard is met, hydric soils would begin to form. 6.0 MONITORING The City of Tukwila requires a long-term monitoring program for mitigation areas to determine whether the mitigation plan was successful (TMC 18.45). A contingency plan is also required to identify potential courses of action and corrective measures if monitoring indicates project performance standards have not been met. 6.1.1.1 Methods The main objective for monitoring is to document the level of success in meeting the performance standards. Monitoring will be conducted by a qualified wetland biologist and will begin the first full growing season after construction is complete and the plants have been installed. At that time, permanent sampling points and photopoints will be established in the creation and enhancement areas. The biologist will determine the size and number of sampling points during the initial site visit. Survival of plantings will be based on comparisons with as - built drawings. Data documenting plant survival and health will be collected each time the site is monitored. Photographs will be taken to document site conditions. 6.1.1.2 Monitoring Schedule The mitigation areas will be monitored for five growing seasons post -construction with visits occurring every other year. An initial stem count of the installed plant material will be conducted following construction (an as -built count). A second stem count of installed plantings will be conducted during Year 1 to evaluate survival during the first year. Monitoring during Years 3 and 5 will focus on evaluating the installed vegetation to determine the success of the mitigation plantings. Monitoring will occur before September to catch any problems earlier in the growing season. A general visual inspection will be conducted each year to provide a qualitative evaluation of mitigation area success. 6.1.1.3 Data Collection The following will be recorded during the monitoring site visits: • Survival rates of vegetation; ESA Adolfson Page 17 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study • General plant health assessment; • Documentation of the presence of undesirable plants (weedy and/or non-native species) with estimated percent cover; • Photo documentation of site conditions; and • Recording of any wildlife use of the area. An assessment of wetland hydrology will be made in the spring. This will include determining the depth of inundation or soil saturation. 6.1.1.4 Reporting Monitoring reports will address the items presented in the preceding section and document successes and problems. The reports will recommend plant species replacements, if necessary (see Maintenance section below). Photographs will be included to document site conditions. One monitoring report will be submitted after each monitoring visit to present the monitoring results for that monitoring period. These reports will be submitted to the City of Tukwila DCD the same year in which monitoring is conducted. 6.1.2 Maintenance Maintenance of the mitigation areas will begin after installation of the project and continue for five years. After the initial planting acceptance by the professional biologist, the landscaping contractor will be responsible for plant survival for a period of one year. After that time, a qualified professional contractor will perform maintenance. Maintenance could include, but may not be limited to: • Installing supplemental plantings as needed; • Watering or providing irrigation during unseasonably dry periods or when the soils are unusually dry; • Removing non-native or invasive plant species if invasive cover is greater than 10 percent of the area; • Providing :fencing around plants to prevent animal damage; and • Providing fencing to prevent vandalism or damage caused by humans. 6.2 Contingency Plan If any portion of the mitigation is not successful, a contingency plan will be implemented. Such plans are prepared on a case-by-case basis to remedy any aspects of the mitigation that do not meet the performance standards. The plan, if required, would be developed in cooperation with the City of Tukwila and Mr. Amon. ESA Adolfson Page 18 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study 7.0 LIMITATIONS Within the limitations of schedule, budget, seasonal constraints, and scope -of -work, we warrant that this study was conducted in accordance with generally accepted environmental science practices, including the technical guidelines and criteria in effect at the time this study was performed, as outlined in the Methods section. The results and conclusions of this report represent the authors' best professional judgment, based upon information provided by the project proponent in addition to that obtained during the course of this study. No other warranty, expressed or implied, is made. ESA Adolfson Page 19 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study 8.0 REFERENCES Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of Wetlands and Deepwater Habitats of the United States. FWS/OBS-79/31. U.S. Fish and Wildlife Service. Ecology (Washington State Department of Ecology). 1991. Shoreline Management Handbook: First Edition. Publication No. 90-45. Olympia, Washington. Ecology (Washington State Department of Ecology). 1992. The Growth Management Act and the State Environmental Policy Act: A Guide to Interrelationships. Publication No. 92- 07. Olympia, Washington. Ecology (Washington State Department of Ecology). 1994. Wetlands Regulations Guidebook. Publication No. 88-5. Olympia, Washington. Ecology (Washington State Department of Ecology). 1997. Washington State Wetlands Identification and Delineation Manual. Publication No. 96-94. Olympia, Washington. Ecology (Washington State Department of Ecology). 2004. Washington State Wetland Rating System for Western Washington Revised. Publication No. 04-06-025. Olympia, Washington. Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual. Technical Report Y-87-1. U.S. Army Engineer Waterways Experiment Station, Vicksburg, Massachusetts. Federal Register. 1982. Title 33: Navigation and Navigable Waters; Chapter II, Regulatory Programs of the Corps of Engineers. Vol. 47, No. 138, p. 31810. U.S. Government Printing Office, Washington, DC. Federal Register. 1986. 33 CFR Parts 320 through 330: Regulatory Programs of the Corps of Engineers; Final Rule. Vol. 51, No. 219, pp. 41206-41260. U.S. Government Printing Office, Washington, DC. Federal Register. 1988. 40 CFR Part 230. Guidelines for Specification of Disposal Sites for Dredged or Fill Material. Vol. 45, No. 249, Pages 85336-85357. U.S. Government Printing Office, Washington, DC. Federal Register. 1994. Changes in Hydric Soils of the United States. July 13. Washington, DC. Herrera Environmental Consultants, Inc. 2001. Gilliam Creek Basin Stormwater Management Plan. Prepared for the City of Tukwila Public Works Department, March 9, 2001. Seattle, Washington. Hruby, T, T. Granger, K. Brunner, S. Cooke, K. Dublanica, R. Gersib, L. Reinelt, K. Richter, D. Sheldon, E. Teachout, A. Wald, and F. Weinmann. July 1999. Methods for Assessing ESA Adolfson Page 20 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study Wetland Functions Volume 1: Riverine and Depressional Wetlands in the Lowlands of Western Washington. WA State Department Ecology Publication #99-115. Hitchcock, C.L., and A. Cronquist. 1973. Flora of the Pacific Northwest: An Illustrated Manual. University of Washington Press, Seattle, Washington. King County Department of Surface Water Management. 1990. The King County Sensitive Areas Folio. King County. 2004. The Soil Survey of King County. U.S. Department of Agriculture Natural Resources Conservation Service 2003. King County GIS revised. Munsell Color. 2000. Munsell Soil Color Charts. Greta Macbeth, New Windsor, New York. Snyder, D.E., P.S. Gale, and R.F. Pringle. 1973. Soil Survey of King County Area, Washington. U.S. Soil Conservation Service, Washington, DC. NRCS (Natural Resources Conservation Service). 1995. Hydric Soils List for Washington. Revised December 15, 1995. NRCS (Natural Resources Conservation Service). 1998. Field Indicators of Hydric Soils in the United States, Version 4.0. G.W. Hurt, P.M. Whited, and R.F. Pringle (eds.), United States Department of Agriculture, Ft. Worth, Texas. Tukwila Department of Community Development. 2004. Tukwila Wetland/Watercourse and Buffer Map. USFWS (U.S. Fish and Wildlife Service). 1988. National List of Plant Species that Occur in Wetlands: Northwest (Region 9). Biol. Rpt. 88(26.9). United States Department of Interior, Washington, DC. USFWS (U.S. Fish and Wildlife Service). 1988. The National Wetland Inventory, Des Moines. quadrangle. 1995. King County GIS revised 2004. USFWS (U.S. Fish and Wildlife Service). 1993. 1993 Supplement to List of Plant Species that Occur in Wetlands: Northwest (Region 9). Washington State Department of Fish and Wildlife. 2005. Washington State Department of Fish and Wildlife Priority Habitat and Species Map. Vepraskas, M.J. 1999. Redoximorphic Features for Identifying Aquic Conditions. Technical Bulletin 301. North Carolina Agricultural Research Service, North Carolina State University, Raleigh, North Carolina. ESA Adolfson Page 21 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study FIGURES AND PHOTOGRAPHS ESA Adolfson March 2007 Revised May 2007 PROJECT SITE SOURCE: Rand McNally & Company, 2006. La Tourelle Sensitive Areas Study . 207119 Figure 1 Vicinity Map Tukwila, Washington SOURCE: USGS Topoquad, 1995; King County GIS, 2004. La Tourelle Sensitive Areas Study . 207119 Figure 2 Topographic Map Tukwila, Washington SOURCE: WDFW PHS, 2005; NWI, 1998; King County GIS, 2004. La Tourelle Sensitive Areas Study . 207119 Figure 3 National Wetland Inventory Map Tukwila, Washington N 0 3 i S 160 St 4 S 164 S156St 0) 0 1 S152St rn S152St co i Q 1 S 152 St 5152 PI 1405 Ramp co S162St ▪ • S161St to re 0 fo & ¢ fa S 169 PI Slade Way o y v ep N V Legend — — Project Site _ Typo 3 Wetlands (City Owned Parcels) Typo 3 Wetlands (Privately Owned Parcels) Typo 2 Wetlands (City Owned Parcels) Typo 2 Wetlands (Privately Owned Parcels) I=Typo1 Wetlands Parks ElCity Owned Parcels Basins Streams Q Buffer Type 3 (50) Em Buffer Type 2 (80) Parcels Streets S 166 St re a S 1 t36 st , Y a SOURCE: City of Tukwila, July 2004. La Tourelle Sensitive Areas Study . 207119 Figure 4 City of Tukwila Wetlands/Water Course and Buffer Map Tukwila, Washington SOURCE: NRCS SSURGO Soils, 2003; King County GIS, 2004. La Tourelle Sensitive Areas Study . 207119 Figure 5 Soils Map Tukwila, Washington j JL Feet 0 WETLAND C 4,026 SF WETLAND A 3.070 SF WETLAND B 1,562 SF 50' BUFFER PROPERTY BOUNDARY' LEGEND DP®11 Existing Wetland' Existing Buffer Data Plot SOURCE: Mead Gilman and Associates, 2007 La Tourelle Sensitive Areas Study . D2071190X'' Figure 6, LaTourelle Wetland! Map Tukwila, Washington, SOURCE: Mead Gilman and Associates, 2007 La Tourelle Sensitive Areas Study . D207119.0X Figure 6 La Tourelle Wetland Map Tukwila, Washington 0 41 dw mC ▪ a. y CO N = COW 3^ 0 N f/) Z o, da u .0 p. • 0(' U 0 WETLAND C 4,026 SF 00 • w Feet j L CTl WETLAND A 3.070 SF WETLAND B IMPACT= 1,562 SF LEGEND' Wetland' Impact DR -1 Data Plot SOURCE: Barghausen Consulting Engineers, 2007 La Tourelle Sensitive Area Study'., D207119:0X' Figure' 7' La, Tiourelle,Wetland Impacts Tukwila, Washington' �. SOURCE Barghausen Consulting Engineers, 2007 La Tourelle Sensitive Area Study . D207119.0X Figure 7 La Tourelle Wetland Impacts Tukwila, Washington DP -4 si' q". WF-1FIC3 WETLAND ENHANCEMENT AREA. =3,070 SF ,i, W WF—WL2 DP -5 WETLAND CREATION AREA = 808 SF (GEOTECHNICAL ENGINEER TO VERIFY AVAILABILITY OF WATER SOURCE) 11� '`0100. 1610'4 .reII III .♦ ,--1��1 GO,;�II�,:��Ti— � II1111/0' 41 /4 ' e 4*II IIGI /0'1,1101 'VIII00#A$60 4 Ii01G►0�► ISI `II/ ►III 11'1,1► II►11'1,1/11i �0'1,1I IIIOI a#G1'/11'I,III( 4%'1,6001'1, •401110: III1., I► 3,968 SF ADDITIONAL BUFFER. AVERAGE BUFFER BOUNDARY 0 0 00 Feet' Ir._ "I II% iI�, ,.,%%/! �. iii%%i:1;;�� Wo%%///Ill L%7//�� ✓!I%////t }� �i j / WOMEN/ 'ARCMIRREEP TEEM - I /.//GI JIMM22 WF—WB1 • /4M22%% v /1%%%%% !%%%%// I 1 %///r o` W .y. row ir1%//%. .. �_ /%/// • %%2p—%%%/,!-. I%%%%%%%%;, /%%%r/.%%%"/ Awwwwwrow • Ar/%%%%% 82 SF - ADDITIONAL. BUFFER = I 11 - BUFFER ENHANCEMENT 2,750 SF III BUFFER, REDUCTION 5,003 SF 1,006 SF ADDITIONAL BUFFER 50' STANDARD BUFFER BOUNDARY /// 12 PROPOSED PLANTING SC4E'DULE SCIENTIFIC NAME COMMONNAME. WETLAND CREATION, Th.Ja plicata Cornue eericea Rubue epectabtlle Salix eltchenele Rosa pleocarpa Tolmela menzleeli Athyrlum Felix-remina WETLAND ENHANCEMENT T}uJa,plicate Cornue earicaa Rona pieocarpa' 5alIx eltcheneie Tolerate' menzlaell BUFFER ENHANCEMENT Peeudoteuga menzleell Corylue cornutai Holodlecue discolor Mahonfa aquifolium Rubue parvlrlorue Weeterni Red Cedar Red Twig Dogwood Sa Imorberryi Sitka WtlIou Clueteredl Glild Reee P1ggy7back Plant Lady' Fern W'eetern Red Cedar Red Twig' Dogwood Clustered' Wlld Roea 51tka Wlllbwi Piggy -back Plant Douglas Fir Beaked Hazelnut Oceanepray, Tall Oregon' Grape Thtmbleberry1 SIZE' SPACING, 1 GAL. 1 GAL, 1 GAL. I' GAIL. 11 GAIL. II GAL, II GAL. IIGAL. 1' GAL. I GAL. I GAL. I GAL. 1 GAL. 1 GAL. 1 GAL. 1 GAL.. 1 GAL. SEED MIX SEED ALL WETLAND AREAS OF' DISTURBED' SOIL WITH THE FOLLOWINCs1 MIX Alopecurue geniculatue Neter' Foxt'aII' 60%. Agroetle etolonifera' Redtop 30% Feetuca' rubra' Red1 Feeous' I0%1 APDL (CATION, RATE: 45 L' BSIACRE', BUFFER REDUCTION' AREA = 5,003'SF BUFFER ADDITION AREA= 5,0561SF BUFFER ENHANCEMENT AREA = 2,750 SF 9' O.C. 4' OL.. 4'' O.C. 4" O.C. 4" O.G. 4" O.G. 4'' U.C.. 91 O.C., 6' O.G. b' O.G. 6' O.G. 6" O.C. 9" O.G. 6'' O.G. 6° oz: 6' OL, LEGEND Wetlandl Creation Wetland Enhancement Buffer Reduction Buffer Addition Buffer Enhancement SOURCE: Barghausen'ConsultingiEngineers, 2007 La,Tourelle Sensitive AreaStudy,. 02071119.0X Figure' 8' LalTourelle Wetland Mitigation) Concept Tukwila„ Washington "'"" \ 4, DP -4 w WETLAND ENHANCEMENT AREA =3,070 SF wF-Vt.3 DP -5 WF-WL2 WETLAND CREATION AREA = 808 SF (GEOTECHNICAL ENGINEER TO VERIFY AVAILABILITY OF WATER SOURCE) 353 SF ADDITIONAL BUFFER T 998 11 I T TRA BUFFER REDUCTION 495 SF ADDITIONAL BUFFER 50' AVERAGE BUFFER BOUNDARY T Feet 236' 256 SF ADDITIONAL BUFFER NOTE: LOTS 9, 10 AND 11 COULD NOT BE DEVE ED IF ONSITE MITIGATION IS PURSUED. BUFFER S.F. REDUCTION 1,664 SF 50' STANDARD BUFFER BOUNDARY PROPOSED PLANTING SCHEDULE SCIENTIFIC NAME WETLAND CREATION Thula plicate Cornus &ericea Rubes speetabllio 8ellx sitehensls Rosa pisocarpe Tolmmia men:aeeli Athyrlum Felix -Femme WETLAND Thula plica Cons fees Rosa sorarpa Sall alto -hens!' 6Imele menzl.ali COMMON NAME Western Red - -r Red Tul- >-gwood Selo erry 81 -- Willow tared Wild Rose Lady Fern Plant y Western Red Gedar Rad Twia Dogwood Clustered Wild Rose Sitka Willow Flea -back Piant QTY SIZE SPACING x x x x x x x x $WED MIX SEED ALL AREAS OF DISTURBED SOIL WITH THE FOLLOWING MIX, Alopeeuna genleulatue Water Foxtall 60% Agresti° etolonirere Redtop . 50% Festuce nitre Red Fescue ID% APPLICATION RATE, 45 LSSJACRE BUFFER REDUCTION AREA= 2,159 SF BUFFER ADDITION AREA = 2,425 SF BUFFER AVERAGE AREA = 28,400 SF BUFFER REQUIRED = 28,100 SF GAL GAL GAL GAL GAL GAL GAL GAL GAL GAL GAL GAL 9' OL. 4' 0.C. 4' OZ. 4' OL. 4' OL. 4' OL. 4' O.C. 9' O.G. b' O.G. b' O.G. 6' O.C. 6' OG LEGEND J, W Wetland Creation Wetland Enhancement Buffer Reduction Buffer Addition SOURCE Sarghausen Consulting Engineers, 2007 Le Tourdle Sensitive Area Study . D207119.OX Figure 8 La Tourelle Wetland Mitigation Concept Tukwila, Washington La Tourelle Sensitive Areas Study Photo 1. Amon property facing northwest from the intersection of South 160th Street and 53`d Avenue South (southeast corner of lot). (October 4, 2005) Photo 2. East -facing view of Wetland A. (February 28, 2007) ESA Adolfson March 2007 La Tourelle Sensitive Areas Study Photo 3. Wetland A. (October 4, 2005) Photo 4. Wetland B soils. (October 4, 2005) ESA Adolfson March 2007 La Tourelle Sensitive Areas Study Photo 5. Wetland C. (October 4, 2005) Photo 6. A spring fed water drainage flowing on top of compacted soils, east of Wetland C. Soil compaction is due to the City of Seattle underground water pipeline. (February 28, 2007) ESA Adolfson March 2007 La Tourelle Sensitive Areas Study Photo 7. Typical upland vegetation within the Amon property site. (October 4, 2005) ESA Adolfson March 2007 La Tourelle Sensitive Areas Study APPENDIX A: METHODS USED TO EVALUATE WETLAND CHARACTERISTICS ESA Adolfson Appendix A March 2007 Revised May 2007 La Tourelle Sensitive Areas Study Wetland Definition Wetlands are formally defined by the U.S. Army Corps of Engineers (Corps) (Federal Register 1982), the Enviromnental Protection Agency (EPA) (Federal Register 1988), the Washington Shoreline Management Act (SMA) of 1971 (Ecology, 1991) and the Washington State Growth Management Act (GMA) (Ecology, 1992) as ... those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas (Federal Register, 1982, 1986). In addition, the SMA and the GMA definitions add: Wetlands do not include those artificial wetlands intentionally created from non - wetland site, including, but not limited to, irrigation and drainage ditches, grass - lined swale,s, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape amenities, or those wetlands created after July 1, 1990 that were unintentionally created as a result of the construction of a road, street, or highway. Wetlands may include those artificially created wetlands intentionally created from non -wetland areas to mitigate the conversion of wetlands. Methods defined in the Washington State Wetlands Identification and Delineation Manual (Ecology, 1997), a manual consistent with the U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), were used to determine the presence and extent of wetlands on the subject property. Washington state and all local governments must use the state delineation manual to implement the SMA and/or the local regulations adopted pursuant to the GMA. The methodology outlined in the manual is based upon three essential characteristics of wetlands: (1) hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three characteristics must all be present in order to determine that an area is a wetland (unless problem areas or atypical situations are encountered). These characteristics are discussed below. Vegetation Plants must be specially adapted for life under saturated or anaerobic conditions to grow in wetlands. The U.S. Fish and Wildlife Service (USFWS) has determined the estimated probability of each plant species' occurrence in wetlands and has accordingly assigned a "wetland indicator status" (WIS) to each species (USFWS, 1997). Plants are categorized as obligate (OBL), facultative wetland (FACW), facultative (FAC), facultative upland (FACU), upland (UPL), not listed (NL), or no indicator status (NI). Definitions for each indicator status are listed in the Glossary. Species with an indicator status of OBL, FACW, or FAC are considered adapted for life in saturated or anaerobic soil conditions. Such species are referred to as "hydrophytic" vegetation. A (+) or (-) sign following the WIS signifies greater or lesser likelihood, respectively, of the species being found in wetland conditions. ESA Adolfson Appendix A-1 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study Areas of relatively homogeneous vegetative composition can be characterized by "dominant" species. The indicator status of the dominant species within each vegetative stratum is used to determine if the plant community may be characterized as hydrophytic. The vegetation of an area is considered to be hydrophytic if more than 50% of the dominant species have an indicator status of OBL, FACW, or FAC. The scientific names and wetland indicator status for each plant discussed in this report are presented in Appendix B. Soils Hydric soils are indicative of wetlands. Hydric soils are defined as soils that are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part of the soil profile (Federal Register, 1994). The Natural Resources Conservation Service (NRCS), in cooperation with the National Technical Committee for Hydric Soils, has compiled lists of hydric soils (NRCS, 1995). These lists identify soil series mapped by the NRCS that meet hydric soil criteria. It is common, however, for a map unit of non -wetland (non - hydric) soil to have inclusions of hydric soil, and vice versa. Therefore, field examination of soil conditions is important to determine if hydric soil conditions exist. The NRCS has developed a guide for identifying field indicators of hydric soils (NRCS, 1998). This list of hydric soil indicators is considered to be dynamic; revisions are anticipated to occur on a regular basis as a result of ongoing studies of hydric soils. Anaerobic conditions create certain characteristics in hydric soils, collectively known as "redoximorphic features," that can be observed in the field (Vepraskas, 1999). Redoximorphic features include high organic content, accumulation of sulfidic material (rotten egg odor), greenish- or bluish -gray color (gley formation), spots or blotches of different color interspersed with the dominant or matrix color (mottling), and dark soil colors (low soil chroma) (NRCS, 1998; Vepraskas, 1999). Soil colors are described both by common color name (for example, "dark brown") and by a numerical description of their hue, value, and chroma (for example, 10YR 2/2) as identified on a Munsell soil color chart (Munsell Color, 2000). Soil color is determined from a moist soil sample. Hydrology Water must be present in order for wetlands to exist; however, it need not be present throughout the entire year. Wetland hydrology is considered to be present when there is permanent or periodic inundation or soil saturation for more than 12.5% of the growing season (typically two weeks in lowland Pacific Northwest areas). Areas that are inundated or saturated for between 5% and 12.5% of the growing season in most years may or may not be wetlands. Areas inundated or saturated for less than 5% of the growing season are non -wetlands (Ecology, 1997). Indicators of wetland hydrology include observation of ponding or soil saturation, water marks, drift lines, drainage patterns, sediment deposits, oxidized rhizospheres, water -stained leaves, and local soil survey data. Where positive indicators of wetland hydrology are observed, it is assumed that wetland hydrology occurs for a sufficient period of the growing season to meet the wetland criteria, as described by Ecology (1997). ESA Adolfson Appendix A-2 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study APPENDIX B: COMMON AND SCIENTIFIC NAMES OF PLANTS AND THEIR WETLAND INDICATOR STATUS ESA Adolfson Appendix B March 2007 Revised May 2007 Amon Property Wetland Delineation PLANT SPECIES LIST FOR THE AMON PROPERTY PROJECT, IDENTIFIED ON OCTOBER 4.2005 COMMON NAME' SCIENTIFIC NAME' WETLAND INDICATOR STATUS2' 3 big -leaf maple Acer macrophyllum FACU Douglas fir Pseudotsuga menziesii FACU* red alder Alnus rubra FAC SHRUBS Douglas spiraea Spiraea douglasii FACW English holly Ilex aquifolium NL evergreen blackberry Rubus laciniatus FACU+ Himalayan blackberry Rubus armeniacus FACU Indian plum Oemleria cerasiformis FACU Japanese knotweed Polygonum cuspidatum FACU* tall Oregon rape Berberis nervosa NL oceanspray Holodiscus discolor NI Pacific blackberry Rubus ursinus FACU salal Gaultheria shallon FACU* salmonberry Rubus spectabilis FAC+ snowberry Symphoricarpos albus FACU vine maple Acer circinatum FAC- bracken fern Pteridium aquilinum FACU cleavers Galium aparine FACU climbing nightshade Solanum dulcamara FAC+ colonial bentgrass Agrostis tenuis FAC Cooley's hedge -nettle Stachys cooleyae FACW creeping buttercup Ranunculus repens FACW curly dock Rumex crispus FAC+ common dandelion Taraxacum officinale FACU English ivy Hedera helix NL English plantain Plantago lanceolata FACU+ field horsetail Equisetum arvense FAC giant horsetail Equisetum telmateia FACW hairy cats -ear Hypochaeris radicata FACU herb Robert Geranium robertanium NL lady fern Athyrium filix femina FAC+ orchardgrass Dactylis glomerata FACU pig -a -back -plant Tolmiea menziesii FAC pineapple weed Matricaria matricarioides FACU red clover Trifolium pratense FACU reed canarygrass Phalaris arundinacea FACW Small -fruited bulrush Scirpus microcarpus NI- OBL skunk cabbage Lysichitum americanum OBL soft rush Juncus effusus FACW sword fern Polystichum munitum FACU tall fescue Festuca arundinacea FAC - ESA Adolfson March 2007 Revised May 2007 Appendix B-1 Amon Property Wetland Delineation 2 Common names are primarily from Flora of the Pacific Northwest (Hitchcock and Cronquist, 1973). Scientific names are as listed in Hitchcock and Cronquist (1973). Scientific names change over time as botanists reevaluate plant species. The scientific name currently listed in the "Washington Flora Project" database (http://flora.ilangainc.com) is given in parentheses if it is different from that listed in Hitchcock and Cronquist (1973). Key to Wetland Indicator Status codes — Northwest Region (Source: USFWS, 1997): OBL late: species that almost always occur wetlands under natural conditions (est. probability >99%). FACW Facultative wetland : species that usually occur in wetlands (est. probability 67 to 99%), but are occasionally found in non -wetlands. FAC Facultative: Species that are equally likely to occur in wetlands or non -wetlands (est. probability 34 to 66%). FACU Facultative upland: species that usually occur in non -wetlands (est. probability 67 to 99%), but are occasionally found in wetlands. UPL Upland: species that almost always occur in non -wetlands under normal conditions (est. probability >99%). NL Not liisted: species that are not listed by USFWS (1997) and are presumed to be upland species. NI No indicator: species for which insufficient information is available to determine status, or which were not evaluated by USFWS. + indicates a species that is more frequently found in wetlands - indicates a species that is less frequently found in wetlands * identifies a tentative assignment based upon either limited information or conflicting reviews 3 Where a range of Wetland Indicator Status ratings are given for a genus, the range reflects the species for which ratings are provided in the USFWS (1997) list. Some species within the genus may be NI or NL. ESA Adolfson Appendix B-2 March 2007 Revised May 2007 La Tourelle Sensitive Areas Study APPENDIX C: DATA SHEETS ESA Adolfson Appendix C March 2007 Revised May 2007 HYDROPHYI'IC VEGETATION INDICATORS °fo of dooainang;•C18L, FAG'W, &FAC: .1/ • PIO Check all indicators that apply & explain below: Visual observation of plant species growing in,. areas of prolonged intmdation/saturation Marphological adaptations Technical Literature Hydrophytlevegetation present? eDi no Rationale for decision/Remadrs: HYDROLOGY 7s it the growing season? '' yes 1- • . ! Physialogical//reproductive adaptations Wetland plant: dabs Personal knowledge of regional plantcoommnnities. Other (explainl Vege,ITA..64 i_sam(riaier \l Based on: soil temp (record other (explain) lilt Dept of inundation: NO pvtc56141- inches Depth to free water in pit NIA f + ' inches Depth to saturated soil: 1001 ibrcik(r inches Check all that apply & explain Below: Stream, Lake or gage data Aerial photographs: • d 6§4) 319aos,. Water Marks: on Drift Lines: . yes ov • Sediment Deposits: yes o� Drainage Patterns: yes (Ito) Oxidized Roca (live mots) Channels <12 in. yes Local Soil Survey: yes no FAC Neutral: yes Water -stained Leaves yes ao Other. Other (explain): Wetland hydrology present? ryes • no " Rationale for decision+a*kr. :1-; •'•• , • Fl t. �M �� I G .e a �cL'�:r)„ 110;0 . t) t iS :: '':10 'Ya•' Gi& 1,G 11 � V rust oI\&O f5 V iSS tyVV- 11icd-YIc 010U cc{ 1 G I 11CPicatfrrS COAL. preved.7 ` tOriwci � ��rc1 'a2or. SOILS ff /cJyjtj000i. Map "Clint Nme Arf? r / •Series & Phase) Taxonomy (subgroup) Drainage Class In0061'72,1e Lci /A )8,11 h ii,vcO • Field observadcros comfrm Yes No mapped type? Profile Description •� Depth (inches) Horizon Matrix color (Munsell moist). Mottle colors (Munsell moist). Mottle abtmdance size & contrast • Texture, concretions, stmccure, etc. ' • 101R 1/2. ooh rAim. hneF • '+ kXtn It Driwing tfsoil prefile (match desctiotian) Hydric Soil Indicators: (check all that apply) S�stosol Histic Epipedoif . Sulfidic Odor Agnic Moisture Regime Reducing Conditions Gleyed or Low-Chroma (=1) matrix x' MapA drama <1 with mottles Mg &Fe Concretions •. High Organic Content ai Surface Layer of Sandy Soils • Organic Streaking in Sandy Sods ' ' Listed on Natioual2aral Hydric Soils List Other (explain in remarks) Hydric sails present?yeses no Rationale for decisian/Remads. nee c F 4)J4.ato{4I o. Wetland Determination (circle) Hydrophytic vegetation present? Hydric soils present? Weiland hydrology present? Rationalegtemarks no no Is the sampling point no ' ' within a wetland? mo • 6, j b Gia rassrowr.� 4 paella.. cP- �o�►t Wc, neck �� ( atf -011 ca • h X010 ' ns� at NOTES: - Ian an& ai% atnelf bl L!/ a€O /pero • SQlrocif l 136 r m" Z tops O {Mote, b\e3 act 1.,;+g►+f d pletssrin.. eac:i!.(j fel - Revised 4197 rojecr/Site: t movk FPlicant/owner: >dtO J Investi;ator(a): Z, DATA FORM 1(Revised) Routine Wetland Determination . (WA State Wetland Delineation Manual or 1987 Corps Wetland Delineation Manual) . ti Alaihan . VA Lo ciieN o Normal Circumstances exist on the site? the site significantly disturbed (atypical situation)? s the area a potential Problem Area? • E laxation of : i . ical or „ . blem•area ' yes .yes GETATTON (For strata,indicate T= tree; S = shrub; H =herb; V = vine) Dominant Plant Species Stratum • % cover Indicator Dominant Plant S Date: 0- .0 sant Cominunitjy ID: p Transect ID: Plot ID: m •Pzat • Indicator INpe.0 HYDROLOGY _ ,) v 111D AIL SedimeatDeposits: yes 411111 Drill Lines:' yea- o ' Drainage Patterns: yes no other (e' .lain , ! : i Dept of inundation: f. pjeSty orches OxidizedRoot (live mo Channels <I2 in. yes (na ) Ah km t.O5 .,d )1 Depth to free water in pit 4Aanf pre) incbes D Fil ,U - - Check all that apply & explain bel • : Stream, Lake or gage data: Other (explain): - • _ Aerial .hoto : Other. • 'hs: Wetland hydrology present? yes • no, Rationale for decision/Remarks: PI- 1 k hvfnihiD4/�• IPdir.aJa P . . . • V j- T . 50 ' FL1 _ . OLlfg s 4 qitifir 5 :•+r MU 1U1 Q.Y1if •A el) S 15 .F1(',•.• 1- FAcu . ..• • )PHYTIC VEGETATION ]NDICAT • % of dominanha.OBL, FACW, & FAC Check all indioators that apply & explain below: Visual observation of plant species growing in areas of prolonged inundationlsaturadon Morphological adaptations Technical Literature Rydrophytie vegetation present? ye Rationale for decision/Rematls: • Physiological/reproductive adaptations Wetland plant database Personal knowledge of regional plant commtmities. Other (a . lain) • I V U WY V -11114Ded urey:'•f�+rW i oprep HYDROLOGY _ ,) v Is it the growing season? -yes: • no . ' Based on: • soil temp (record Water Marks: yes o on SedimeatDeposits: yes 411111 Drill Lines:' yea- o ' Drainage Patterns: yes no other (e' .lain , ! : i Dept of inundation: f. pjeSty orches OxidizedRoot (live mo Channels <I2 in. yes (na ) Local Sod Survey. yes no )1 Depth to free water in pit 4Aanf pre) incbes FAC Neutral: yes . no Water -stained Leaves yesno • Al- Depth to saturated soil: !), i L binehes Check all that apply & explain bel • : Stream, Lake or gage data: Other (explain): - • _ Aerial .hoto : Other. • 'hs: Wetland hydrology present? yes • no, Rationale for decision/Remarks: PI- 1 k hvfnihiD4/�• IPdir.aJa P . . . • V j- SOILS _$^ Map Unit Name J1ryJ{ � Q rW c .(series & Phase) Taxonomy (subgroup) nrainage Class nrta r JeL Field observations confirm Yes mapped type? No , Profile Description Depth (Macs). Horizon Matrix color (Munsell moist) a,5y 16 1-\915M Mottle colors (Munsell moist). .44 ioYato Mottle abundance size & contrast • Text, concretions, structure; etc. 06,n kw unci;) - 100 ID' • ) • D.rdwing of soil .profile • (matrix description) Hydric Soil Indicators: (check all that apply) Efistosal • ,. • HisticEpipednzi Sadie Odor . . Agaic Moisture Regime Reducing Conditions . Oleyed orLow-Chroma (--1) matrix Hydric soils present? yes Rationale for decision/Remarks. 11(4 60ma • • •AiD lpwst#, /90/ (11,60ad-/ _Matrix chraraa 52 with mottles _Mg orFe-Concretions }Ugh organic Content in Surface Layer of Sandy Soils Organic Streaking in Sandy'Soils _ Listed on National/Local Hydric Soils List Other (explain in =marks) Wetland Determination (circle) Hydrophytic vegetation present? yes Hydric soils present? yes Wetland hydrology present yes Radonale/Remarits: NOTES: Is the sampling point within a wetland? 3 fJYeV3 LV( nob Yes Revised 4/97 DATA FORM 1(Reviser° Routine Wetland Determination . (WA State Wetland Delineation Manual or . 1987 Corps Wetland Delineation Munuan Project/Site: g Date: f Aim 0 et, P' -my . 2 7 i3 Applicant/owner: 7G �-P1+i.8't1 Im�esti(s): V IV11 i� /•p i1 ps Cow ay • kl Ne •• Sone: 1414� g/T/g; _, Do Normal Circumstances exist .= the site? • Z••• no . Is the site significantly disturbed (atypical situation)? yes Is the area a potential Problem Area? . .yes • Explanation of atypical or problem area: . Community ID: le eittMc,i/p Transect ID: fg Plot ID: • 1)/;, , 3 - A VEGETATION (For strata, indicate T = tree; S = shrub; H = herb; V = vine) •• Dominant Plant Strattumn % cover Dominant Plant Species • Stra% cover_ Indicator 1Species s 7�/l tt�ia- // 0 , }In-ddiicator P , r i 4/ attu'm %7 .. zo . Jecil.0 hy elm lc& itintil t dN_ • 11 ?-D x FigGY/i% LyiiJn antis; P1 • /5 O 3 Lo • and -7,t. in6i7iG5. e., ,i FAL AlilciP1t3drt JILL . .14 JD. File? Sladys. z,mhyitg I/ • 30 x -e.e1- l%1.r;4, 'Alaik # A • . lekko HYDROPIC VEGETATION INDICATORS " % of dominangt:OEL, FACW, &FAC dr7• O ' r� NO' r+1 (,Q . d. t (�eS f urnc� are, l o It +n arl big Check all Indicators that apply & explain below: litle ClOntrital • • • Visual observe -don of plant species Bowing in . Physiological/reproductive adaptations _ areas of prolonged inundation/saturadon _ Wetlayd"plant dambase Morphological adaptations Personal knowledge of regional phmt conmatmities ' - • Technical Literature Other (explain) Hydrophytic vegetation present? 6' no • �Rationale far decision/Rematkm i7i� s? �J 4,4721:b-844 �� "le', c�tl del_S��i�S Cre•rr� Gn�ci r d /a n <n..6Lrrkerr� drrLt :�i,�n.. /4z•''�,.,n Szlhrl? e,- •, ROLOGY Is it the growing season? yes, no SOILS - Map Unit Name {Series & Phase) Taxonomy (subgroup) Prrr�nf Al�oarwn� , Drainage Class Field observations confirm Yes No mapped type? Profile Description Depth [Inches). Horizon Matrix color (Munsell moist). Mottle colors (Mansell moist). Mottle abundance size & contrast Texture, concretions, . structure, etc. 6-7 A GL.Ey •sja, ; jtl er .n fat,1-%. • DrSWmg of soil . ,profile (match description) Hydric Soil Indicators: (check all that apply) Histcsol • . • 1sd'c••Epipedoa . Sulfidic Odor X .Aquic•Moisture Regime • • - Reducing Conditions Glcyed or Low-Clavma (1) matrix < Matrix chroma S 2 with mottles • Mg or Fe Concretions : • Sigh Organic Content in. Surface Layer of Sandy Soils Organic Streaking in Sandy Soils Listud on National/Local Hydric Solis List Other (explain in remialcs) Hydric sails present? Rationale for decisin�� sAvd •/bAl dear rno nrineY�.r on.. es no Wetland Determination (circle) Hydrophytc vegetation present? agi Hydric sobs present? Wetland bydmlogy presem2 no no la the sampling point no within a wetland? Ra donnl emarks: • f / Cf i itt4,,,, a rd NOTES: De- 3 / 'aI , az PSS / ty��7// . he/ 4.PP�y-,x 7‘ b4 12,1471044.44-/y ` S✓^7"1/yratI/svet'd,?Q t�JLl.el� de .+� L 1kiy d�l� J . A Arra Rje�' ' SFite-147A� iV Q. t ! ' - Q- //' / ;0 1: 'F �L c/'Lr L4-ii4D Soft. rJ I 7),,e71J 'i O�r�C' - aL dire . , .. - 414 /0611 Gni l; be.• 4 `raced • Atfity 5.vnaits 4141 )`Yl. Revised 4197 4404 /fir - etirar44 1 /a Sri rA' ce 44O. pexs , • DATA FORM 1(Reviser° Routine Wetland Determination . (WA State Wetland Delineation Manual or . 1987 Corps Wetland Deiiueatioa Manua]) Project/Site: rn43A, p2g1'J Applicant/owner: 1 ZE A -11-i curt) Investigator(s): «P171,TL . 2 ) z 3 . t . • • Ll• as . •situat'ion)7 yes .yes A . Date: /.d f f/pS County: ',/e./A/6 • ' . State: iill4 : SITIR: . -j Community ID: Ye eifliMiarle0 Transect ID: Plot ID: '' A 3 Do Normal Circumstances exist on tie site? Is the site signiiiesutly disturbed (atypical Is the area a potential Problem Area? . Explanation of atypical or emblem area: VEGETATION (For strait,indicate T = tree; S = shrub; H = herb; V = vine) • ' ' . Stratum % cover Indicator Dominant Plant Species • Stratum % cover_ , Indicator Dominant Plant Species *`46/41/$7 ,airathi4- /5' 0 . y A p14rr1i F.feCil , sr (r arIy/ ty5W) Jan inveri 77. 1-1• Z , IS" FR-Git . OL A , Jin ,/- bk I riimL / '22774., 2AS. 1.., it . 5" ' FWc MIrl'ilttlit c11144 • '14 M. r 1G ty ,91-641.14. Lb/l42 # ' 30 re -e.4— ••Ak ,hekad, if' .•4'i7 - il L • iet,kasir.ki7Z3 `5.' • Sa r• • P411•6•71 .. • _ HYDRO PHTC VEGETATION .:; • ' % of daffinaa�:OHL, FACW, Check an indicators that apply Visual observation of plant species areas ofprolonged inundation/saturation Morphological adaptations Technical Literature INDICATORS 8c FAC 53.T10 • •' Physiological/reproductive - Wetlagdplant fa0(e� r+A 0 Elly %n camp 4) U• 41- C o rnr t adaptations dambase knowledge of regional pleat (explain) Le.dzP,�slt�rnc�.i .• • . • • • . comma antes ' ' •• re i • & explain wowing below: in . K :a Personal • - Other Hydrophytic vegetation present? Rationale for decisioalRemarks: C3 no . Y d a.✓e. P# ,74caI cot_ . 5-p.44 'ids' ere:" ' a' "Prni.4a? / 44 4:`...1410- %n 5'OZi/7fbe,r•• /iprGSd% cj"-.-f)-m)11.1.4 /anq ScajL41"_ 4Ln ROLOGY (record temp no ) Is it the growing season?• Based on: • soil temp Water Merles: yes ro an Sediment Deposits: yesa'7, Drift Lines: yes T1�7 Oxidised Root (live iaots),,zit„ Channels <12 in. k; S no Drainage Patterns: gp no Local Sod Survey yes no !?RIS. other (explain) X. inches Dept of inundation: Depth to free water in pit: W saturated sod: ^ _ L inches FAC Neutral: 41 no 3 •i • Water -stained Leaves yes ' _ c') inches 'Depth Check an that apply & explain Stream, Lake or gage date: Aerial photographs: below: Other (explain): __ Other: � Wetland hydrology .present? �s... ,tno / atzonale for deci S�I�•7`�® 16 5;4,0.4,4. '� •� i ...„...,4 tma. f e /�1-,�1 d r, 71 c /1 l!' GL/'�'Gt r die 7 7 66 t 0.4 YUQ7 Ike' / arro4y , 7(1,:?:-. I i . . !• i.Y.•% ,- . • -'' • - •s 1 SOILS • Map Unit Name PT11' Ol a t d) {Series & Phase) Taxonomy (subgroup) Drainage Class Field observations confirm . Yes No mapped type? Profile Description Depth (inches). Horizon Matrix color (lvlrmsef moist). Mottle colors (Mtmsell moist). Mottle abundance size & contrast • Texture, concretions, . strncrtrre, etc. 6- 7 7-/ , r /tip. 414 y r/ Alm • S'ewkly 1 . Dxgwuig of soil profle (match description) • Hydric Soil Indicators: (check all that apply) Histosal • •Estic•Epipedori . Sulfidic Odor .Agaic•Moisture Regime • • Reduni ng Conditions Gleyed or Low -Chrome (tel) matrix k 'Matrix chroma S 2 with mottles • •• Mg orFe Corneretians • • High Organic Contentin Surface Layer of Sandy Soils Organic Streaking in Sandy Soils Listed on•Natinnal/Lneal Hydric SoBs List • Other (explain in remadrs) Hydric soils present? Rationale for decisi c5*:Ls meg ,Iv ine‘Acf/a14 es no /�� t rn o,�`h'aS,Cs L GC M/a t 1:r 7- , Wetland Determination (circle) Hydraphytic vegetation present? no Hydric sons present? •'tom no la the sampling point Werlaadhydmlogypresen •gr'l no witbinawetland? Rationalemarks: mi zflL 4r htftd— effilt2 Mc -6, • no NOTES: DP3 itka.7'-I ; AIL , tlt- PSS" f14- /a th otirstir.ri b4.pd 49 • /y * �� ��.� sie 1.44 t )I bAJJ Ara bd parksst Sp tl,'? �a. id,�,�J eica., fi hyr��it ,r i f fa; - 4.• 047t a ,�`ar17dL L ��' - •aw444 Z. P.�ds �, 0 it' 1i ; i•+G7 ,1S/1 . q 1E[ 1'e' y,d/ i Al an lila.'4I `arac d • fly 4-n S 4 /F11#/ )`7-L Revised 4197 491404 kit.. E arritr4 ¢d4tei 7• sou• ' cE s g c pr . • jecr/Site: ami pplicant/owner. �Qe X11 esti: s). 3 (A 1 DATA FORM 1(Revisetij Routine Wetland Determination t . • . (WA State Wetland Delineation Mantial'or 1987 Corps Wetland Delineation Manual) Azm . 4 o Normal Circumstances existpa the site? the site significantly disturbed (atypical situation)? s the area n potential Problem Area? . Explanation of a ,'ical or .1 •blem.anea: • yes Yes no GETATION (For strata, indicate T= tree; S = shrub; H = herb; V =vine) Dominant Plant Species Stratum % cover Indicator Dominant Plant Species • Date: - ({,5 County: ' 1{ ' State: • Srr/R: Consmuam: f , !, Transect ID: " J "2 `-d1 e/ Plot ID: ,r-.40 Stratum cov VP:I-DIN.' eq atm. v;.riim N a OE,1... 'klijods 5re.,htkii 3 10 rif f €: r(tc (hull� , 1-1 I D file.13 • - 'I¢ Nla,;is Arortrloaci' 11 . SO FAt t3" 5eefItc 14 15 Q L- .: . E .5fr, _v ��ciii A to - .FA0,63 , _ . Afiaeo ciVoi-6414 .-1 1-C Eii�.. + .. OPHYTIC VEGETATION INDICATORS_, . • % of d muni ,'OBL, PAM& PAC: 1 Check all indicators that apply & explain below: Visual obaerva�ion of plant species growing in . areas of prolonged intmdation/saturadon Morphological adaptations • Technical Literature Hydrophytic vegetation present? ye) no Rationale for decision/Remarks: Th W ctb rtravlei as- HYDROLOGY - Is it the growing season? yes Based on: sod temp (record: temp other (explain) • 4. Vt)ro(t�rt� Ph ysiologicaUseproductive adaptations Wetland plant database Petsonni knowledge of regional plant communities Other (explain) • Water Marks: yes an' Sediment Deposits: yes Drift Lines: yes kliv Drainage Patterns: yes no Dept. ofintmdation: /V0 tOtK3e14-inches' Depth to free water in pit; Pf 541.1- inches Depth to saturated soil: Urap. (winches Oxidized Root (live mots) Channels <12 in.tY ono• FAC Neral: 0 0 Local Soil Survey: yes no Water-stainedLeaves yes nom' ' 1 1 Check all that apply & explain below: Stream, Lake or gage data: Aerial photographs: Wetland hydrology present?, Rationale for decision/Remarks: LtltSG ffitP att,.. ;wail(dv► Ate 6A .04b pp Other: • no Other (explain): �.tlCa urs D a n toy slasim . 'G6InvO " Zo • SOILS Map Unit Name {Series & Phase) Taxonomy (group) rrwf AJOavotb9 ifYitaiefAAti Drainage Class Field observations comf¢m Yes No napped type? Profile Description . Depth ' ('mates) Horizon Matrix color (Munsell moist) Mottle colors (Munsell moist) Mottle. abunjlance size & contrast • Texture, concretions, . structure, etc. . roving Of id ..pru[ile I (match description) 0- 10)0\112. Ili ---•��, �iSwitek `. so, lit ��tyi ` 6 . ----. fi! / L I l`i • Hydric Sail Indicators: Histasol (check all that apply)• Epipedoa . • Odor Moisture Regime Conditions - or Low -ba (-1) matrix )( Matmt - aroma _I 2 with mottles • Content in Face Layer of Sandy Soils .. Streaking in Sandy Solis. : •• NationaULocai Hydric Sas List in remarlts) • Histiq . • Mg-orFeConcretions 5l Sulfidic High Organic Aquic Organic Organic Reducing listed on •- Gleyed Other (explain Hydric soils present? yes no . • Rationale for dec;si • . . ... . ; • ill•S OhN0414. `fes , _r -Ary • S'44 ±I- _ Wetland Determination (circle) ..•: • • Is the sampling pointdriri • no within a wetland? Hydrophytio vegetation present? Hydric sobs present? Wetland hydrology present? yes no no 410ao elReutarks: - • Rational• A/! 3 ' • -• r1?tie(5 fkC.E. • . . • NOTES: 5i1.6a a„ � t ra} t � b t is oak r 44 6Q ntivivuut Ltcrem5 u-si 5O t -t y a fps 6►e L'Li i • cue cod • Revised 4/97 DATA FORM 1 (Revised) Routine Wetland Determination . (WA State Wetland Delineation Manual or 1987 Corps 1�Vet]and DeGneafion ManunIj • •,jecvsite: 1 afyym 0 ytty • .plicant/owner: S.Q. A4Mont,-Sm Investi_ato s : _VVlp�f .A T, ..-o G rl{ • Date: 16 ..9,...- 05- ty; �iiqq w• . 1 aS�r`'G` S/T/R I Do Normal Circumstances existpn the site? yes , • 1 - the site significantly disturbed (atypical situation)? yes • • the area a potential Problem Area? yes :': Ex •lanation of a A. ical or . • blem area: Community ID: 0 -) Transect ID: r". Plot ID: tip _-� j • • , GETATION (For strata,'iifdic:ate T = tee; S = shrub; 11 = herb; V = vine) Do�minant Plant S • ecies Stratum % cover Indicator Dominant Plant Species Stratum % cover • Indicator Pr 1W+ •, aro i taailLt (O FA(;•iii IUue D Y/{ r. ■ �5 in i tri )b FAL • • • HYDROPHYTIC VEGETATION INDICATORS. %.af dominants OBL, FACW, & FAC 1 ea rip ' Check all indicators that apply & explain below:• Visual observation of plant species growing in . Physiological/reproductive adaptations areas of prolonged mundation/saturation Wetland plant database Morphological adaptations Personal knowledge of regional phut communities Technical Literature Other (explain) ' Hydropbytic vegetation present? no Rationale for decision/Remarks: Ord.. ,1orn )....L,11-- ,j-` vv , .• HYDROLOGY Is it the growing season? yes - no • Water Marks: yes �� on Sediment Deposits: yes no .•. Based on: soil temp (record temp ) Drift Lines: yes ao Drainage Patterns• I io 1 • other (e 'lain) . yes Dept. of inundation: ---_ inches Oxidized Root (live roots), Channels <12 in. e (o) Local Soil Survey: yes no Depth to free water in pit >4, inches FAC Neutral: �tio Water -stained Leaves no D - . th to saturated soil: • • . ' > _.flinches. • yes Cheek all that apply & explain below: Stream, Lake or gage data Other (explain): Aerial .hoto j.hs: Other: Wetland honaydroollogyo present?. yes' •. ': .. •.' .... ... tNs, Fortdd_C pcy,•5 71, .f‘6j• tz! /~ -/a Zfa -LI nm; -t (1 1/r C a SOILS • Map Unit Name (Series & Phase) Taxonomy (sulagrouP) AWavt&riri Meaai VeYtal Ikt11 • .„ Drainage Class al* eto Field observations con.fimii.,•; Ys No - mapped type? • Proille.Description Depth ..• (inches) Iforizon., ' Mattix color . (Munsell : Moist) Mottle colors . (Munseil moist) Mottle abundanOe. size & contrast • Textrire, concretions; stracture, etc. Drawing of soil .profile (match description) - • • • • . . - . . • • • i . 1.- , I., ,..,1 ID -lb S . 9.sY ills ....- . . --- 54 /00."--- • • ' .. i.... -1 , • .' . ! , • , .. ., . • .. • - - ... .. • • • -% •-• • . 1 Hydric Soil Indicators: liristosol (cbeck all Pait apply) Epipedmi . - Odor Moisture Regime Conditions - or Low-Chrcana (=I) matrix • - Matrix • clnuroa 52 withmottle Concretions Content in Surface Layer of Sandy Soils Streaking in Sandy Soils ' • • NarionallLocal Hydric Soils List . lain in remitrics . Eilstic Mg or Fe ...SulEdic High Organic Aquic • Organic Reducing Listed on • Gleyed Other(. Hydric soils present? yes Rationale for decision/Remarks: A7-yiel., c1$3e-s pagar4. - . , . • , . . . . . . - . . • . •. • - • . Wetland Determination (circle) C-,) no yes no . Is the sampling point .yes within a -wetland? . .. - ' • Eydrophytic vegetation present? Hydric soils present? Wetland hydmIony present? no yes Ill Rationale/Remarks: ' bn / y ,PYI i r f;:lia. rj 0.— ,- • NOTES: „ !i:.. 1 ,PP 7-5 .2- 4 -4 4L5-71-14"Vi 17 ad . c..42 6/1/ &ZSh/ td-/Apvt, Tc. 75 -41,2,11 ;r1 PP- 9 i'-v-s;d4trpoic pra,„ganv; .-74751t.:: 4197 Minnie Dhaliwal - Fwd: La Tourelle short plat Page 1 1 From: Minnie Dhaliwal To: Alexia Dorsch Date: 04/05/2007 10:59 am Subject: Fwd: La Tourelle short plat CC: Joanna Spencer Hi Alexia, I sent you some additional comments from Sandra regarding your geotech report as it relates to the wetlands on the property. After discussing it internally, there is also some concern about impacting the hydrology for off-site wetlands. Please have your geotech engineer address the attached comments. Minnie Dhaliwal - La Tourelle short plat Page 1 of 1 From: Sandra Whiting To: Joanna Spencer Date: 04/04/2007 12:30 PM Subject: La Tourelle short plat CC: Minnie Dhalivval Hi Joanna, Another concern I have about the groundwater hydrology on this site is that groundwater supports the wetlands down the hill on the Five Rivers property. We would need assurance that the proposed groundwater management on the La Tourelle site would not affect the wetlands off-site and downslope. The geotech should be able to assess this in conjunction with the assessment of the impacts to the on-site wetlands. Sandra file://C:\Documents%20and%20Settings\Minnie\Local%20Settings\Temp\XPGrpWise\4... 04/05/2007 .� Minnie Dhaliwal - Fwd: La Tourelle Shortplat - Geotech Peer Review Page 1 j From: Minnie Dhaliwal To: Alexia Dorsch Date: 04/02/2007 12:18 pm Subject: Fwd: La Tourelle Shortplat - Geotech Peer Review CC: Joanna Spencer Hi Alexia, You have already received peer review comments related to the Geotech report. Attached are some additional review comments from Sandra Whiting related to your geotech report. Please have you Geotech Engineer address the attached comments in additional to the peer review comments already provided to you. Minnie Dhlaliwal Senior Planner City of Tukwila 206-431-3685 Minnie Dhaliwal - La Tourelle Shortplat - Geotech Peer Review Page 1 of 1 From: Sandra Whiting To: Joanna Spencer Date: 03/30/2007 :12:42 PM Subject: La Tourelle Shortplat - Geotech Peer Review CC: Minnie Dhaliwal Hi Joanna, My reading of Shannon and Wilson's report raises some questions. 1. Is it really necessary to put a boring in the middle of the wetland ("sag pond")? If it can't be avoided, then we should require the applicant to do restoration in the event that the project does not go forward. 2. If groundwater levels are to be reduced to 5 feet below the surface across the site, then the applicant must also analyze what impacts this will have on the downgradient wetland that is mostly off-site on the City of Seattle right-of-way and on the wetland that may be retained (the "sag pond") in terms of wetland hydrology. Reducing groundwater levels may result in drying up the wetlands - an impact that would require full mitigation for all the wetlands on and off-site. Perhaps the applicant's geotech consultant can analyze this along with the other analyses required. Thanks! Sandra file://C:\Documents%20and%20Settings\Minnie\Local%20Settings\Temp\XPgrpwise\46... 04/03/2007 Minnie Dhaliwal, RE: La Tourelle short plat, Sensitive Area Study No String -Avai 1 From: "Ilon Logan" <ilogan@adolfson.com> To: "Sandra Whiting" <swhiting@ci.tukwila.wa.us> Date: 03/29/2007 8:53 am Subject: RE: La Tourelle short plat, Sensitive Area Study CC: Hi Sandra, "Alexia Dorsch (E-mail)" <adorsch@barghausen.co... Attached is a revised Figure 6 for the La Tourelle SAS. The wetlands were mislabeled on Figure 6, but are correct on Figure 7, the descriptions, and the data sheets. Please let me know if you have any questions. You can replace your Figure 6 with the attached pdf, or hand write the correct labels as they are shown on Figure 7. I should also note that: while preparing the SAS, I discovered that in the original Amon Property Wetland Delineation Report (January 2006) Wetlands A and B were swapped in the descriptions and the data sheets. The most efficient fix of the report was to change the data sheets. So, you'll see that the data sheets for Wetland B are now for Wetland A and vice versa in the SAS. This should not cause any confusion in your current review. Thanks, Ilon Original Message From: Sandra Whiting [mailto:swhiting@ci.tukwila.wa.us] Sent: Wednesday, March 28, 2007 3:57 PM To: Minnie Dhaliwal Subject: La Tourelle short plat, Sensitive Area Study Minnie, I started to review the Sensitive Area Study today and realized that the descriptions of the wetlands in the text don't match the characteristics of the wetlands observed in the field, nor do they match the figures in the document. I think that either the figure is mislabeled or the description headings are mislabeled. At any rate they don't match and it is very confusing to review. So, I recommend that the report be corrected and resubmitted before proceeding further. Sandra LOWS° 9Yr,311 :POVP3 [OIPZLZO se .AP Polou9 OMP'aY PU PU.Owv: Bl LLOZ SN o, JGWu i� Minnie Dhaliwal - Fwd: La Tourelle short plat, Sensitive Area Study No String Avai 1� From: Minnie Dhaliwal To: Alexia Dorsch Date: 03/28/2007 4:49 pm Subject: Fwd: La Tourelle short plat, Sensitive Area Study Hi Alexia, Please address the attached comments from Sandra Whiting regarding the Sensitive Areas Study. Let me know if you have any questions. Minnie Dhaliwal Senior Planner City of Tukwila 206-431-3685 mdhaliwalC@ci.tukwila.wa, us Minnie Dhaliwal - La Tourelle short plat, Sensitive Area Study Page 1 of 1 From: Sandra Whiting To: Minnie Dhaliwal Date: 03/28/2007 3:56 PM Subject: La Tourelle short plat, Sensitive Area Study Minnie, I started to review the Sensitive Area Study today and realized that the descriptions of the wetlands in the text don't match the characteristics of the wetlands observed in the field, nor do they match the figures in the document. I think that either the figure is mislabeled or the description headings are mislabeled. At any rate they don't match and it is very confusing to review. So, I recommend that the report be corrected and resubmitted before proceeding further. Sandra file://C:\Documents%20and%20Settings\Minnie\Local%20Settings\Temp\XPgrpwise\46... 04/03/2007 Ciiy of Tukwila Department of Community Development File Number L06 - 081 LAND USE PERMIT ROUTING FORM TO: ❑ Building C Planning Q Public (l Works ❑ Fire Dept. ❑ Police Dept. ❑ Parks/Rec Project: q& t 1— ) Address: (6a -1 —V3'v.AS Date transmitted: 3 - 2-1--01 Response requested by: StaffDate coordinator. ``n/'.-� ��11� response received: COMMENTS ❑ DRC review requested ❑ Plan submittal requested ❑ Plan approved Plan check date: Comments prepared by: 03/14/04 r P0' ENG\N-IV Minnie Dhaliwal City of Tukwila Planning Department 6200 Southcenter Boulevard Tukwila, WA 98188 CIVIL ENGINEERING, LAND PLANNING, SURVEYING, ENVIRONMENTAL SERVICES March 27, 2007 COURIER DELIVERY RE: Submittal of Sensitive Area Study La Tourelle Property Permit No. L06-089 King County Parcel Nos. 537920-0005 and -0006 Our Job No. 12650 Dear Minnie: RECEIVED MAR 2 `l 2001 COMMUNITY DEVELOPMENT Per your request, ESA Adolfson has completed the Sensitive Area Study for the above-mentioned property. We are submitting three copies of the study for your continued review and routing. As you are aware, a few months ago we applied to the Army Corps of Engineers for a jurisdictional determination. Since you and I last spoke, the Corps conducted a site visit and has determined that the centrally located wetlands are "isolated" and they will not take jurisdiction. This is discussed further in the Sensitive Area Study. Please contact me at this office if you have any questions or require additional information. Respectfully, Alexia D. Dorsch Assistant Planner ADD/pj [12650c.008] enc: As Noted cc: Joe Amon Ilon Logan, ESA Adolfson Tristan Peter-Contesse, ESA Adolfson Tom Barghausen, Barghausen Consulting Engineers, Inc. 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES • OLYMPIA, WA • TEMECULA, CA • WALNUT CREEK, CA www.barghausen.com LA TOURELLE DEVELOPMENT Sensitive Areas Study Prepared for: Mr. Jawaid Arnon March 2007 r ESAAdoifson La Tourelle Sensitive Areas Study TABLE OF CONTENTS 1.0 INTRODUCTION 1 1.1 Project Overview 1 1.2 Project Background 1 2.0 METHODS 2 2.1 Review of Existing Information 2 2.2 Wetland Delineation Classification, and Rating 2 2.3 Wetland Classification and Rating 3 2.4 Wetland and Buffer Function Assessment 4 3.0 FINDINGS 5 3.1 Description of Project Area 5 3.1.1 Watershed Setting 5 3.1.2 Topography, Soils, Vegetation, and Land Use 5 3.2 Wetland Descriptions 6 3.2.1 Wetland A 6 3.2.2 Wetland B 7 3.2.3 Wetland C 7 3.3 Wetland Ratings 8 3.4 Corps Jurisdictional Determination 9 3.5 Streams and Other Drainage Features 9 3.6 Wildlife Habitat Types and Functions 9 3.7 Wildlife Observations 10 3.8 Listed and. Priority Species 10 4.0 IMPACTS 10 4.1 Wetland Impacts 10 4.2 Stream Impacts 11 4.3 Buffer Impacts 11 4.4 Wildlife Habitat Impacts 11 5.0 MITIGATION 12 5.1.1 Avoidance 12 5.1.2 Minimization 13 5.2 Off-site Miitigation Option 13 5.3 On-site Mitigation Option 14 5.3.1 Wetland Creation and Enhancement 15 5.3.2 Wetland .Buffer Averaging 16 5.3.3 Goals and Objectives 16 5.3.4 Performance Standards 17 6.0 MONITORING 17 6.1.2 Maintenance 18 6.2 Contingency Plan 19 7.0 LIMITATIONS 19 8.0 REFERENCES 20 ESA Adolfson March 2007 page -i La Tourelle Sensitive Areas Study FIGURES AND PHOTOGRAPHS 1 APPENDIX A: METHODS USED TO EVALUATE WETLAND CHARACTERISTICS 1 APPENDIX B: COMMON AND SCIENTIFIC NAMES OF PLANTS AND THEIR WETLAND INDICATOR STATUS 1 APPENDIX C: DATA SHEETS 1 ESA Adolfson March 2007 page -ii La Tourelle Sensitive Areas Study 1.0 INTRODUCTION At the request of Mr. Jawaid Amon, ESA Adolfson (Adolfson) performed wetland delineations and prepared this Sensitive Areas Special Study for the La Tourelle Plat Development, located in the City of Tukwila, Washington. All rights -of -entry to the subject property for the purpose of conducting this study were granted by Mr. Amon, who is the property owner. The boundaries of the study area were established based on discussions with Mr. Amon and a parcel map. This report has been written to meet the requirements of the Sensitive Areas Special Studies process described under TMC Chapter 18.45.040. 1.1 Project Overview The proposed La Tourelle development consists of two parcels (#5379200006 and #5379200005) totaling 3.6 acres located within Section 26, Township 23 North, Range 4 East, in Tukwila, Washington. The triangular-shaped property is bounded by South 160th Street to the south, 53`d Avenue South to the east, and a City of Seattle right-of-way and South 159th Street to the north (Figure 1). The site is situated in a residential area, within the Gilliam Creek Basin of the City of Tukwila. The site is currently undeveloped, containing mostly deciduous forest and shrubs (Photo 1). Steep slopes characterize much of the site's northern area, while the middle and southern portions of the site are generally flat or gently sloping. The southern edge of the site slopes steeply to 53`d Avenue South. It is the applicant's intent to develop the property with 13 single-family lots plus a future development tract to be located in the northwest portion of the site. Upon approval of the off-site mitigation plan as described in this report, the future development tract would be divided into three single-family lots, for a total of 16 lots. Should off-site mitigation not be approved by the City, and on-site mitigation preferred, the future development tract would comprise the wetland mitigation area and would not be developed. Barghausen Consulting Engineers (BCE) and Adolfson have collaborated to ensure that the proposed on-site mitigation area meets City of Tukwila standards while also being sized in such a way as to allow three additional lots. 1.2 Project Background Adolfson performed a wetland delineation on the Amon property on October 4, 2005, and produced the Amon Property Wetland Delineation Report in January 2006. Adolfson delineated three wetlands in the vicinity of the proposed project. Two wetlands (Wetlands A and B) were identified on the property. The third wetland, Wetland C, is located north of the property within a City of Seattle right-of-way; a small portion of this wetland extends onto the Amon property. A watercourse associated with Wetland C was also identified. Wetland boundaries were professionally surveyed by Mead, Gillman and Associates of Woodinville. The City of Tukwila Department of Community Development verified the wetland boundary on February 8, 2007, and concurred with the surveyed boundaries. A preliminary plat application for the La Tourelle development is being prepared for submittal to the City. The City of Tukwila requires a Sensitive Areas Special Study for development proposals that may impact a sensitive area and/or its buffer (TMC 18.45.040). ESA Adolfson March 2007 Page 1 La Tourelle Sensitive Areas Study 2.0 METHODS 2.1 Review of Existing Information A review of existing literature, maps, and other materials was conducted to identify wetlands or site characteristics indicative of wetlands on the subject property. These sources indicate the likelihood of the presence of wetlands; actual wetland determinations must be based upon data obtained from field investigations. Several documents were reviewed: • The U.S. Geological Survey 7.5 minute Topographic Map, Des Moines quadrangle. 1995. King County GIS revised 2004. • The Soil Survey of King County Area, Washington. U.S. Department of Agriculture Natural Resources Conservation Service. 2003. King County GIS revised 2004. • The National Wetland Inventory, Des Moines. U.S. Fish and Wildlife Service. 1988. • Hydric Soils of the State of Washington. Natural Resources Conservation Service. 1995. • The King County Sensitive Areas Folio. King County Department of Surface Water Management. 1990. • The City of Tukwila Wetland/Watercourse and Buffer Map. City of Tukwila Department of Community Development. July 15, 2004. • The Washington State Department of Fish and Wildlife Priority Habitat and Species Map. 2005. 2.2 Wetland Delineation Classification, and Rating Methods defined in the Washington State Wetlands Identification and Delineation Manual (Ecology, 1997), a manual consistent with the U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), were used to determine the presence and extent of wetlands on the subject property. Washington State and all local governments must use the state delineation manual to implement the Shoreline Management Act and/or the local regulations adopted pursuant to the Growth Management Act. The methodology outlined in the manual is based upon three essential characteristics of wetlands: (1) hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three characteristics must all be present in order to determine that an area is a wetland (unless problem areas or atypical situations are encountered). The "routine on-site determination method" was used to determine the wetland boundaries. The routine method is used for areas equal to or less than five acres in size, or for larger areas with relatively homogeneous vegetative, soil, and hydrologic properties. Formal data plots were established in areas of relatively homogeneous vegetation, where information regarding each of the three wetland parameters (vegetation, soils, and hydrology) was recorded. Dominant herbs and saplings/shrubs within a five-foot radius, and dominant trees and woody vines within a 30 -foot radius, from the data plot center were recorded on the data form (Ecology, 1997). This information was used to distinguish wetlands from non -wetlands. If wetlands were determined to be present on the subject property, the wetland boundaries were ESA Adolfson March 2007 Page 2 La Tourelle Sensitive Areas Study delineated. Wetland boundaries were identified with sequentially numbered colored flagging imprinted with the words WETLAND DELINEATION. Data plot locations were also marked with colored flagging. The methods used to assess wetland characteristics are described in greater detail in Appendix A. A list of plant species observed on-site is presented in Appendix B. 2.3 Wetland Classification and Rating Two classification systems are commonly used to describe wetlands. The hydrogeomorphic (1-IGM) system describes wetlands in terms of their position in the landscape and the movement of water in the wetland (Brinson, 1993). The U.S. Fish and Wildlife Service classification system (Cowardin et al., 1979) describes wetlands in terms of their vegetation communities; these include, for example, emergent, scrub -shrub, and forested community types. Wetlands in the City of Tukwila are rated according to TMC 18.45.080. Wetlands are designated as Type 1, 2, or 3 based on the following criteria: 1. Type 1 wetlands are those wetlands that meet any of the following criteria: a. The wetland is characterized by the presence of species listed by the federal government or State as endangered or threatened, or the presence of critical or outstanding habitat for those species; b. The wetland has 40-60% permanent open water in dispersed patches with two or more classes of vegetation; c. The wetland is equal to or greater than five acres in size and has three or more wetland classes, one of which may be substituted by permanent or open water; or. d. The wetland is documented as regionally significant waterfowl or shorebird areas by the State Department of Fish and Wildlife. 2. Type 2 wetlands are those wetlands that meet any of the following criteria: a. The wetland is equal to or greater than one acre in size; b. The wetland has three or more wetland classes and is less than 5 acres; c. The wetland is characterized by the presence of nesting sites for priority species as listed by the Washington State Department of Fish and Wildlife; or, d. The wetland is hydrologically connected (non -isolated) to a Type 1 or Type 2 watercourse. 3. Type 3 wetlands are those wetlands that are greater than 1,000 square feet and less than one acre in size with two or fewer wetland classes. ESA Adolfson March 2007 Page 3 La Tourelle Sensitive Areas Study 2.4 Wetland and Buffer Function Assessment Wetlands and buffers provide valuable benefits to the environment and society. Because detailed scientific knowledge of wetland functions is limited, evaluations of the functions of individual wetlands are somewhat qualitative and dependent upon professional judgment. For this project, wetland functions were assessed using methods adapted from the Washington State Wetland Function Assessment Method (WFAM) (Hruby et al., 1999). The methods are based on the hydrogeomorphic (HGM) classification for wetlands, which categorizes wetlands into groups that function in similar ways based on the geomorphic and hydrologic characteristics. The following 15 functions were assessed: Functions Related to Water Quality Improvement • Potential for Removing Sediment • Potential for Removing Nutrients • Potential for Removing Heavy Metals and Toxic Organics Functions Related to Hydrology (Water Quantity) • Potential for Reducing Peak Flows • Potential for Decreasing Downstream Erosion • Potential for Recharging Groundwater Functions Related to Habitat Suitability • General Habitat Suitability • Habitat Suitability for Invertebrates • Habitat Suitability for Amphibians • Habitat Suitability for Anadromous Fish • Habitat Suitability for Resident Fish • Habitat Suitability for Wetland - associated Birds • Habitat Suitability for Wetland - associated Mammals • Native Plant Richness • Potential for Primary Production and Organic Export TMC 18.45.080 defines the purpose of buffer areas as protecting the integrity, functions, and values of a wetland area. Buffer functions were also assessed using WFAM methods. Wetland buffers are intended in general to: 1. Minimize long-term impacts of development on properties containing wetlands; 2. Protect wetlands from adverse impacts during development; 3. Preserve the edge of the wetland and its buffer for its critical habitat value; 4. Provide an area to stabilize banks, to absorb overflow during high water events, and to allow for slight variation of aquatic system boundaries over time due to hydrologic or climatic effects; ESA Adolfson March 2007 Page 4 La Tourelle Sensitive Areas Study 5. Reduce erosion and increased surface water runoff; 6. Reduce loss of or damage to property; 7. Intercept fine sediments from surface water runoff and serve to minimize water quality impacts; and 8. Protect the sensitive area from human and domestic animal disturbances. 3.0 FINDINGS The following sections describe the results of the field investigation conducted by Ilon Logan and Janice Martin within the Amon property on October 4, 2005. These sections describe the three on-site wetlands, one of which extends off-site, upland habitats, and wildlife observations. Five data plots were established within relatively uniform areas of vegetation on the property. Data sheets for each of the formal data plots evaluated for this project are provided in Appendix C. 3.1 Description of Project Area 3.1.1 Watershed Setting The property is located toward the southern end of the Puget Trough within the Green River drainage basin and Water Resource Inventory Area (WRIA) #09. Within WRIA #09, the project lies in the Gilliam Creek basin (WRIA #09-0032) and within the Crystal Springs subbasin. The Crystal Springs subbasin, covering 242 acres, receives most of its drainage from groundwater seeps on the northeast slope of McMicken Heights near the project area. A culvert conveys Crystal Springs underneath I-5 to a drainage ditch that is located between Southcenter Parkway and 1-5. The subbasin is bounded on the north by SR 518, on the south and west by the ridge crest of McMicken Heights, and on the east by Southcenter Mall (Herrera Environmental Consultants Inc., 2001). 3.1.2 Topography, Soils, Vegetation, and Land Use The U.S. Geological Survey (USGS) Des Moines quadrangle (USGS, 1995) shows the moderate to sleep slopes on the property, which slopes down toward the northeast. The property flattens out between steeper areas located on benches or ridges (Figure 2). The National Wetlands Inventory (NWI) map shows no wetlands on the property (Figure 3). Additionally, the City of Tukwila Wetland/Watercourse and Buffer Map (2004) does not indicate any wetlands on-site but does show a watercourse flowing eastward in a City right-of-way north of the property (Figure 4). The Soil Survey of King County (King County GIS, 2004) maps the entire property as Arents, Alderwood material (AmC) (Figure 5). Arents, Alderwood soil has convex slopes from 6 to 15 percent, with some at 30 percent. It is a gravelly sandy loam that is moderately well drained, has variable permeability, and moderate to severe erosion hazard (Snyder, et al., 1973). Arent, Alderwood material is a considered non -hydric (non -wetland) soil (NRCS, 1995). ESA Adolfson March 2007 Page 5 La Tourelle Sensitive Areas Study Upland vegetation within the property includes big leaf maple (Acer macrophyllum) in the canopy layer, with English ivy (Hedera helix), and Himalayan blackberry (Rubus discolor) in the understory (Photo 7). Red alder (Alnus rubra), Indian plum (Oemleria cerasiformis), reed canarygrass (Phalaris arundinacea) and other upland grasses such as orchardgrass (Dactylis glomerata) are also present. Salmonberry (Rubus spectabilis), Cooley's hedge -nettle (Stachys cooleyae), giant horsetail (Equisetum telmateia), and Himalayan blackberry are dominant within wetland areas on the property. Land use in the property vicinity includes residential housing and undeveloped land. Crystal Springs Park, a City owned park, is adjacent to the property's northwest corner, and a City of Seattle right-of-way for the Bow Lake water pipeline borders the property to the north. 3.2 Wetland Descriptions Three wetlands (Wetlands A, B, and C) occur on the property. Wetland C lies largely off-site within a City of Seattle utility right-of-way north of the property (Figure 6). The characteristics of the wetlands are summarized in Table 2 and discussed below. 3.2.1 Wetland A Location, Size, and Geomorphic Setting. Wetland A (3,070 sf) is a palustrine scrub -shrub (PSS) wetland with no outlet (Photo 2). It is located on the west -central portion of the property, on a gentle north -facing slope that decreases to a shallow depression. Hydrology, Soils, and Vegetation. Data Plot 3 (DP -3) characterizes Wetland A. The wetland appears to be an isolated wetland that is seasonally saturated and inundated due to high groundwater and precipitation. Indicators of wetland hydrology included saturated soils at the surface of the soil pit, and free water at 11 inches below the surface. Soils investigation found a surface horizon extending to seven inches below ground surface consisting of a black (10YR 2/1) sandy clay loam. From seven to 16 inches in depth, the soils observed were a greenish gray 5/10Y (gleyed) sandy loam with brownish yellow (10YR 6/8) mottles. Giant horsetail (Equisetum telmateia, FACW), Cooley's hedge -nettle (Stachys cooleyae, FACW) and salmonberry (Rubus spectabilis, FAC+) are the dominant plant species present in Wetland A. Other vegetation present included skunk cabbage (Lysichitum americanum, OBL) and lady fern (Athyrium filix femina, FAC+). Functions and Values. Wetland A provides some water quality improvement function because it is a depression with no outlet, and most of the wetland contains persistent vegetation. However, the wetland is generally flat and thus provides minimal detention of surface drainage. The wetland provides some reduction of flood flows and erosion because it is located within a depression with no outlet, but this function is also minimized by the wetland's generally flat topography and small size. The scrub -shrub vegetation and undisturbed upland buffer combine to perform wildlife habitat functions. However, the presence of invasive vegetation (Himalayan blackberry) and lack of habitat features (e.g., snags, downed wood) decrease the wetland's ability to provide higher habitat functions. Overall, this wetland provides low function due to its position on a slope, degraded nature due to invasive species and small size. ESA Adolfson March 2007 Page 6 La Tourelle Sensitive Areas Study The buffer of Wetland A is relatively undisturbed and provides a level of function similar to the wetland. The presence of invasive species, primarily Himalayan blackberry, decreases the native plant species richness, and the buffer is lacking dense herbaceous vegetation that would provide water quality improvement functions. 3.2.2 Wetland B Location, Size, and Geomorphic Setting. Wetland B (1,562 sf) is a depressional palustrine scrub -shrub (PSS) wetland with no apparent outlet (Photo 3). This wetland is located in a linear depression near the center of the property, and is seasonally saturated and occasionally inundated. Hydrology, Soils, and Vegetation. Data Plot 1 (DP -1) characterizes Wetland B. The wetland appears to be an isolated wetland that is seasonally saturated due to high groundwater and precipitation. Surface water likely infiltrates after storm events. No standing water or other evidence of surface ponding was observed during the field investigation. Based on the presence of hydrophytic vegetation and hydric soils during our field delineation in October 2005, and due to the wetland's location in a depressional area, wetland hydrology would likely be present during the growing season. Soils in this data plot were a very dark brown (10YR 2/2) sandy loam to a depth of eight inches (Photo 4). From eight to 16 inches below the soil surface, the soils were a dark grayish -brown (2.5Y 4/2) loamy sand with distinct dark yellowish -brown (10YR 4/6) mottles. Wetland vegetation is dominated by Japanese knotweed (Polygonum cuspidatum,FACU*), salmonberry (Rubus spectabilis, FAC+), and Cooley's hedge -nettle (Stachys cooleyae, FACW). Himalayan blackberry (Rubus discolor, FACU) occurs along the hillside and partially within the wetland. Functions and Values. This wetland occurs in a linear depression and is seasonally saturated and occasionally inundated. Wetland B provides similar functions to Wetland A, but at lower levels due to its degraded conditions. Both water quality improvement function and reduction of flooding and erosion are limited due to the small size of the wetland and lack of detention area. Wetland B contains invasive vegetation (Himalayan blackberry, Japanese knotweed, and English ivy) which compromise the ability of the wetland and its buffer to provide native species richness and wildlife habitat function. The presence of English ivy in the wetland buffer results in a lower level of water quality improvement function because the species is aggressive and outcompetes native herb species. Overall, this wetland provides low function due to invasive species, small size and degraded nature. 3.2.3 Wetland C Location, Size, and Geomorphic Setting. Wetland C (4,026 sf) is a palustrine, emergent and scrub -shrub (PEM/PSS) wetland. A narrow drainage channel extends eastward from known springs located northwest of the Amon Property (Photo 5). The majority of the drainage channel is within Wetland C with a portion extending east of the wetland boundary. All but 16 square feet of the wetland are located off-site, within a City of Seattle utility right-of-way for the Bow Lake water pipeline. ESA Adolfson March 2007 Page 7 La Tourelle Sensitive Areas Study Hydrology, Soils, and Vegetation. Data Plot 4 (DP -4) characterizes Wetland C. Soils were saturated to the surface within DP -4. A narrow spring -fed drainage channel extends east of this wetland. Soils in DP -4 were a very dark brown (10YR 2/2) sandy clay loam from zero to 10 inches below the soil surface. From 10 to 16 inches in depth, the soils were a black (2.5Y 4/1) sandy loam with mottling. The mottles (medium, common and distinct) were dark yellowish brown (10YR 4/4). The odor of sulphur was present within the data plot, which is also indicative of redoximorphic conditions. Wetland C vegetation is dominated by reed canarygrass (Phalaris arundinacea, FACW) and giant horsetail. Other species observed included small -fruited bulrush (Scirpus microcarpus, OBL), salmonberry, and red alder. Functions and Values. Wetland C provides limited water quality improvement functions because it contains dense herbaceous vegetation that slows surface water flows and traps pollutants. It provides minimal stormwater detention because it is situated on a slope and surface drainage flows through a narrow channel that continues east of the wetland. Much of the wetland vegetation is mowed because it is within a utility right-of-way, which decreases wildlife habitat function. Overall, Wetland C provides limited functions because it is regularly disturbed and contains multiple invasive species. Similarly, the portion of the buffer of Wetland C that is within the right-of-way is regularly mowed and contains low growing grass and herbaceous species. The portion of the buffer on the Amon property is composed of big leaf maple and red alder trees with Himalayan blackberry in the understory. This area provides wildlife habitat function and protects the edge of Wetland C. The buffer also reduces erosion and intercepts fine sediments and pollutants from surface water runoff. 3.3 Wetland Ratings The City's wetland rating criteria are contained in TMC Chapter 18.45.080 and described in Section 2.2. Wetlands A, B and C meet the criteria for Type 3 wetlands because (1) they do not meet the criteria for Type 1 or 2 wetlands, and (2) they are greater than 1,000 square feet and less than one acre in size with two or fewer wetland classes. ESA Adolfson March 2007 Page 8 Wetland' A Size square #set) 3,070 sf La Tourelle Sensitive Areas Study Table 2. Wetland Classifications and Ratings HGMI Ciass / Cowardln Class A Depressional PSS West central portion of property on north facing slope City fiulkwlil Rating Type 3 City of Tukwila Buffer 50 feet B 1,562 sf Depressional PSS Near center of property Type 3 50 feet c 4,026 sf Depressional PSS/PEM Mostly off-site (16 sf on applicant property) Type 3 50 feet A Shrub. Wetland Classifications (Cowardln et. al., 1979 and Brinson 1993): PEM-Palustrine Emergent, PSS-Palustrine Scrub 3.4 Corps Jurisdictional Determination As requested by the City during the pre -application meeting, a jurisdictional determination by the US Army Corps of Engineers (Corps) was conducted for Wetlands A and B. Mr. Amon submitted a request for jurisdictional determination to the Corps on February 9, 2007. The Corps conducted a site visit on March 20, 2007 and determined that both Wetlands A and B meet the definition of isolated wetlands and are not under Corps jurisdiction. In 2002, Corps jurisdiction over isolated waters under the Clean Water Act was eliminated in light of the decision of the United States Supreme Court in Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, (the SWANCC decision). 3.5 Streams and Other Drainage Features During the field delineation in October 2005, a small spring -fed stream was observed entering Wetland C from the west via a culvert. The drainage flows east through the wetland, along compacted soils (Photo 6). The majority of the watercourse falls within Wetland C. According to TMC 18.15.100, this is a Type 4 watercourse that requires a 50 -foot buffer. The watercourse buffer falls within the 50 -foot buffer of Wetland C. 3.6 Wildlife Habitat Types and Functions Upland forest habitats occur across the property. Big leaf maple (Acer macrophyllum) is dominant in the canopy layer, with red alder and Indian plum also present. Shrub layers consist primarily of English ivy and Himalayan blackberry. Dominant grasses include reed canarygrass and orchardgrass (Dactylis glomerata). Habitat elements observed in upland areas include large trees, shrub thickets, and snags, although functions of this habitat are reduced due to the dominance of non-native English ivy and Himalayan blackberry. Habitat functions of the on-site wetlands are somewhat compromised by invasive species, as discussed in the wetland descriptions above (Section 3.2). ESA Adolfson March 2007 Page 9 La Tourelle Sensitive Areas Study 3.7 Wildlife Observations Species observed during the field investigations included Pacific tree frog, American robin, black -capped chickadee, and Steller's jay. Other species of birds, mammals, reptiles, and amphibians typical of Puget Sound lowland deciduous forest are also expected to use habitats on the property. 3.8 Listed and Priority Species The Washington State Department of Fish and Wildlife (WDFW) provides maps with locations of priority habitats and species. No priority habitats or species are documented on or in the vicinity of the property. Two small open water emergent wetlands occur within one mile of the property, in addition to the Green River and two areas designated as urban natural open space. No priority wildlife species were observed on the site during field investigations in October 2005. 4.0 IMPACTS The La Tourelle development will result in direct impacts to Wetland B and the buffer of Wetlands A and B. The project involves constructing 13 single-family lots, a future development tract to be located in the northwest portion of the site, a central access road and cul- de-sac, and associated infrastructure for water, sewer, power, and gas services. Upon approval of off-site mitigation by the City of Tukwila, the future development tract would be divided into three single-family lots, for a total of 16 lots. As described in Section 5.0 below, if the City does not prefer off-site mitigation, the future development tract would comprise the wetland mitigation area and would not be developed. 4.1 Wetland Impacts The proposed project will impact approximately 1,562 square feet (0.04 acre) of Wetland B (Table 3). Due to the constraints of steep slopes and upland forest in the western portions of the site, in addition to the shape of the site and location of access points, it is not possible to completely avoid wetland impacts. A single stormwater detention vault is proposed, which would not impact wetlands. Wetland B will be completely filled (1,562 sf). This wetland is located near the center of the site, where proposed lots 5, 6, and 7 would be located (Figure 7). Wetland B is a Type 3 depressional wetland with no outlet. Wetland B functions similarly to Wetland A, but at lower levels. Both the water quality improvement function and the capacity for flood reduction are limited in this wetland due to the small size of Wetland B. ESA Adolfson March 2007 Page 10 La Tourelle Sensitive Areas Study Table 3. Summary of Wetland Impacts rid Area uare A 3,070 N/A Wetland Impact uare feet' None B 1,562 Lots 5, 6 and 7 1,562 c 4,026 N/A None Total Impact 1,562 4.2 Stream Impacts No impacts to the watercourse associated with Wetland C are proposed as part of the La Tourelle project. In addition, there will be no impacts to Wetland C that might influence the existing hydrology of the watercourse. 4.3 Buffer Impacts In addition to impacting Wetland B and its buffer, the proposed project will impact 2,159 square feet of the buffer associated with Wetland A. The southern portion of the buffer would be reduced (1,664 square feet) to accommodate construction on lot 12 and the eastern portion would be reduced (495 square feet) for construction of the stormwater vault. Wetland A is a Type 3 depressional PSS wetland with a 50 -foot buffer. The buffer of Wetland A provides functions and values similar to those of the wetland itself, including water quality improvement for untreated stormwater runoff. The buffer consists of undeveloped forest that provides habitat for birds, small mammals, and amphibians as well as an undisturbed connection to the wetland. 4.4 Wildlife Habitat Impacts The proposed site design will remove upland forest, wetland, and associated buffers that provide habitat for wildlife. Upland forest and steep slopes on the northwestern portion of the property will be avoided. Wildlife habitat functions currently provided by Wetlands A and B will be replaced by the proposed landscaping and the planting of trees as required by tree replacement code requirements. As discussed previously, habitat functions of Wetlands A and B are somewhat compromised due to the presence of invasive species and lack of habitat features. Upland habitats have also been colonized by invasive species and are likely functioning at a reduced level. Wildlife using impacted areas may be displaced to adjacent suitable habitats within the property that are being preserved as Sensitive Areas. Undisturbed habitats that are not currently developed are also present in the vicinity of the site. ESA Adolfson March 2007 Page 11 La Tourelle Sensitive Areas Study 5.0 MITIGATION Adverse impacts to wetland functions and values as a result of the La Tourelle project must be mitigated under the criteria outlined in TMC 18.45.090. Under TMC 18.45.090(B4), isolated Type 3 wetlands may be altered or relocated with an adequate mitigation or enhancement plan. As described above, on March 20, 2007 the Corps determined that both Wetlands A and B meet the definition of isolated wetlands. Typically, mitigation for impacts to wetlands must be addressed in the following sequence: 1. Avoid wetland and buffer impacts. 2. Minimize wetland and buffer impacts. 3. Mitigate for wetland and buffer impacts in the following order of preference: a. restore wetlands on upland sites that were formerly wetlands; b. enhance significantly degraded wetlands; c. create wetlands on disturbed upland sites such as those with vegetative cover consisting primarily of exotic introduced species or noxious weeds. In addition, TMC 18.45.090 requires mitigation planning to: 1. Clearly demonstrate that changes would be an improvement of wetland and buffer qualitative functions. 2. Provide a restoration or creation plan to compensate for the impacts to the wetland at a ratio of 1.5 to 1. 3. Compensate via wetland enhancement at a ratio of 3 to 1. 4. Provide for on-site mitigation except where such mitigation is not scientifically feasible or practical, the functions created off-site are significantly greater than those lost, or established regional goals strongly justify mitigation off-site. 5. Locate off-site mitigation within the same watershed where the wetland loss occurred. 6. Generally locate mitigation sites within the Tukwila city limits, unless otherwise approved by the Director. 7. Pursue siting in the following order of preference: (1) upland sites that were formerly wetlands; (2) idled upland sites generally having bare ground or vegetative cover consisting primarily of exotic introduced species, weeds, or emergent vegetation; (3) other disturbed wetland; or (4) existing degraded wetland. 5.1.1 Avoidance The site design avoids impacts to Wetland A and the majority of its buffer, as well as Wetland C and the associated watercourse. However, due to the site constraints, including the property ESA Adolfson March 2007 Page 12 La Tourelle Sensitive Areas Study shape, location of access points, and upland forest and steep slopes covering a portion of the property, impacts to Wetland B and its associated buffer cannot be avoided. 5.1.2 Minimization Project engineers have made efforts to minimize impacts to wetlands and buffers. These alterations will limit buffer impacts to 2,159 square feet and prevent impacts to the rest of the wetland area. Impacts to Tract 999 and its upland forest are also minimized. Measures to be implemented to minimize impacts during construction include: • Conducting a pre -construction meeting on-site with the construction contractor and a professional biologist to discuss the construction sequence. • Clearly marking the limits of the construction area with orange barrier fencing. This type of barrier reduces the potential for heavy equipment to damage vegetation and soil outside the construction area, particularly within the adjacent forest and wetland. • Establishing temporary erosion and sedimentation control measures and BMPs, including silt fences, sediment rolls, and straw bales to prevent suspended particles from leaving the construction zone. The contractor will be responsible for inspection of all erosion control measures and will repair any damage to the erosion control structures, as needed. • Locating staging areas and stockpile sites outside the wetlands and the buffers. • Maintaining erosion control measures throughout the site until bare soils have been successfully vegetated and approved by a professional biologist. 5.2 Off-site Mitigation Option The La Tourelle development project proposes off-site mitigation as a preferred alternative to on-site mitigation. Due to site constraints, such as steep slopes, property shape, and high-quality upland forest habitat in the western portion of the property, mitigation of wetland impact within the property boundaries may be less desirable than off-site mitigation. Off-site mitigation must be approved by the City, and if approved, the off-site mitigation location would be determined in cooperation with the City. Off-site mitigation is allowed by the City of Tukwila under certain circumstances and must meet the criteria outlined in TMC 18.45.090.E as discussed below. According to TMC 18.45.090.E (a), off-site mitigation may be allowed if "on-site mitigation is not scientifically feasible due to problems with hydrology, soils, waves or other factors" or "wetland creation opportunities are limited by steep slopes and by hydrology sources." On the La Tourelle project site, wetland creation opportunities are extremely limited by steep slopes in the northwest portion of the site. Wetland A is spring -fed by hillside seeps on a gentle slope. The extent of this subsurface hydrology is not known. TMC 18.45.090.E (b) states off-site mitigation may be allowed if "mitigation is not practical due to potentially adverse impact from surrounding land uses." The area surrounding the La Tourelle project is experiencing increasing residential development, which will likely result in habitat fragmentation and changes in subsurface and surface hydrology patterns as the area urbanizes. TMC 18.45.090.E (c) states off-site mitigation may be allowed if "existing functional values created at the site of the proposed restoration are significantly greater than lost wetland ESA Adolfson March 2007 Page 13 La Tourelle Sensitive Areas Study functional values." With proper site selection and design, off-site mitigation could result in greater functional values than those currently performed by Wetlands A and B or those expected with on-site mitigation. The wetlands provide limited water quality improvement functions because they are located either on a slope or are generally flat and thus provide minimal detention of surface water. The reduction of flood flows and erosion functions are also limited by flat topography and small wetland size. The scrub -shrub vegetation and undisturbed upland buffer perform some wildlife habitat function, but this is limited by the presence of invasive vegetation (Himalayan blackberry, English ivy, Japanese knotweed) and lack of habitat features (e.g. snags, downed wood). In comparison to on-site wetlands, the mitigation wetland could provide increased water quality improvement function, higher flooding and erosion functions, and better wildlife habitat function through increased habitat complexity and dominance of native plant species. Lastly, TMC 18.45.090.E (d) states: "established regional goals for flood storage, flood conveyance, habitat or other wetland functions have been established and strongly justify location of mitigation at another site." The Gilliam Creek Stormwater Management Plan (Herrera Environmental Consultants, Inc., 2001) notes that the lower reach of Gilliam Creek conveys runoff from the entire drainage basin and is prone to frequent flooding. The plan notes that impervious surface resulting from urban development has resulted in scour and erosion in the upper reaches of Gilliam Creek. The lower reaches have high levels of sediment deposition and flooding as the water moves quickly through upper portions of the basin (near the La Tourelle site). In addition, the steep stream channel slopes in the upper basin aggravate the problems of upstream erosion and downstream sedimentation. While on-site wetland creation/enhancement on the La Tourelle property would provide a minor improvement in flood storage functions in the basin, there are likely other mitigation opportunities within the basin that could provide a greater level of flood management function to help address these issues. In conclusion, based on the limited opportunities for and feasibility of on-site mitigation, the anticipated functions and values performed by the mitigation wetland, and the location within the Gilliam Creek watershed, the La Tourelle project appears to be a good candidate for off-site mitigation. Off-site mitigation should be located in the same watershed and the site selected in the following order of preference: (1) upland sites that were formerly wetlands; (2) idled upland sites generally having bare ground or vegetative cover consisting primarily of exotic introduced species, weeds or emergent vegetation; (3) other disturbed upland; and (4) existing degraded wetland. 5.3 On-site Mitigation Option If th off-site mitigation option is not selected by the City of Tukwila, the project proposes the following on-site mitigation concept. To mitigate for the direct impacts to wetlands and buffers caused by site development, the project proposes to enhance 3,070 square feet of existing wetland and create 808 square feet of wetland, if off-site mitigation is not the preferred alternative. Each mitigation element is summarized in Table 4 and described in detail in the following sections. ESA Adolfson March 1007 Page 14 La Tourelle Sensitive Areas Study Table 4. On -Site Mitigation Summary Mitigation 1 A 0 B 1,562 Total 1,562 1.5:1 (creation) 3:1 (enhancement) Creation of 808 square feet of wetland Enhancement of 3,070 square feet of wetland (Wetland A) 5.3.1 Wetland Creation and Enhancement The 1,562 square feet of direct wetland impacts would be mitigated using two methods: wetland creation and wetland enhancement. Wetland creation would be conducted at a mitigation ratio of 1.5:1, as required by the City of Tukwila for Type 3 wetlands. Wetland enhancement is proposed at a mitigation ratio of 3:1. Figure 8 is a conceptual enhancement and restoration plan that shows the proposed mitigation and planting details. The project would create 808 square feet of additional wetland through minimal grading and planting native species adapted to wet conditions (Table 5). The creation area is downslope, immediately north and northwest of Wetland A and will be an extension of the existing wetland. The goal is to expand the area of Wetland A, which is currently primarily dominated by salmonberry. Table 5: Planting List for On -Site Wetland Creation Scientific Name Common Name Layer Thuja plicata western red cedar Tree Cornus sericea red osier dogwood Shrub Rubus spectabilis salmonberry Shrub Salix sitchensis Sitka willow Shrub Rosa pisocarpa clustered wild rose Shrub Tolmeia menziesii pig -a -back plant Emergent Athyrium filix femina lady fern Emergent To protect and improve the functions provided by Wetland A, the wetland would be enhanced (3,070 square feet) (Figure 8). Native vegetation in the wetland is currently composed of salmonberry and lady fern. Invasive species, including Himalayan blackberry, English ivy, and English holly, are outcompeting native species and providing dominant cover. No tree species are present and there are areas of bare ground. Removal of the invasive species and planting native trees and shrubs amongst the existing salmonberry would restore and enhance Wetland A. The enhanced wetland would provide additional water quality improvement function, wildlife habitat value, and increased plant species diversity. A list of plantings is included as Table 6. ESA Adolfson March 2007 Page 15 La Tourelle Sensitive Areas Study Table 6: Planting List for On -Site Wetland Enhancement Scientific Name Common Name Layer Thuja plicata western red cedar Tree Cornus sericea red osier dogwood Shrub Rose pisocarpa clustered wild rose Shrub Salix sitchensis Sitka willow Shrub Tolmeia menziesii pig -a -back plant Emergent Within both the creation and enhancement areas, trees and shrubs would be planted from one - gallon or two -gallon containers, except for willow, which would be stakes or whips. A native seed mix would also be applied to stabilize the soils and reduce the potential for weedy species establishment. A temporary irrigation system would be used, if needed, during the dry summer months or during periods of unusually low precipitation for the first one to two years following installation. Non-native plant species would be controlled throughout the monitoring period (discussed below) to allow the planted species to become established. 5.3.2 Wetland Buffer Averaging Approximately 2,159 square feet of wetland buffer would be reduced to accommodate construction on lot 12 and the on-site stormwater vault. To offset these impacts, approximately 2,425 square feet of additional buffer would be set aside in the sensitive area tract as part of the overall mitigation area. The additional buffer areas are located in three locations shown on Figure 8. The buffer of Wetland A and the mitigation area would provide the same functions as the existing buffer, including water quality improvement for untreated stormwater runoff and wildlife habitat. 5.3.2.1 Grading/Soils Soils in the wetland creation area would be excavated to approximately one foot below existing wetland grade. The top six inches of topsoil would be stockpiled. During construction, the wetland would be over -excavated by six inches to allow for six inches of topsoil to be placed in the created wetland. 5.3.2.2 Hydrology Water supply to the wetland creation and enhancement area would primarily come from existing groundwater seeps on the slope. The seepage is currently expressed at the surface within Wetland A. Surface water runoff from adjacent upland areas and precipitation would also contribute water to the mitigation area. Water is expected to be temporarily detained in the mitigation areas, and would ultimately infiltrate. 5.3.3 Goals and Objectives The goal of this mitigation plan is to offset wetland impacts through creation of wetland adjacent to existing wetland, and enhancement of the existing wetland to restore functions and values. ESA Adolfson March 2007 Page 16 La Tourelle Sensitive Areas Study 6.1.1.2 Monitoring Schedule The mitigation areas will be monitored for five growing seasons post -construction. An initial stem count of the installed plant material will be conducted following construction (an as -built count). A second stem count of installed plantings will be conducted during Year 1 to evaluate survival during the first year. Monitoring during Years 2, 3 and 5 will focus on evaluating the installed vegetation to determine the success of the mitigation plantings. Monitoring will occur before September to catch any problems earlier in the growing season. A general visual inspection will be conducted each year to provide a qualitative evaluation of mitigation area success. 6.1.1.3 Data Collection The following will be recorded during the monitoring site visits: • Survival rates of vegetation; • General plant health assessment; • Documentation of the presence of undesirable plants (weedy and/or non-native species) with estimated percent cover; • Photo documentation of site conditions; and • Recording of any wildlife use of the area. An assessment of wetland hydrology will be made in the spring. This will include determining the depth of inundation or soil saturation. 6.1.1.4 Reporting Monitoring reports will address the items presented in the preceding section and document successes and problems. The reports will recommend plant species replacements, if necessary (see Maintenance section below). Photographs will be included to document site conditions. One monitoring report will be submitted annually to present the monitoring results for that growing season. These reports will be submitted to the City of Tukwila DCD the same year in which monitoring is conducted. 6.1.2 Maintenance Maintenance of the mitigation areas will begin after installation of the project and continue for five years. After the initial planting acceptance by the professional biologist, the landscaping contractor will be responsible for plant survival for a period of one year. After that time, a qualified professional contractor will perform maintenance. Maintenance could include, but may not be limited to: • Installing supplemental plantings as needed; ESA Adolfson March 2007 Page 18 La Tourelle Sensitive Areas Study • Watering or providing irrigation during unseasonably dry periods or when the soils are unusually dry; • Removing non-native or invasive plant species if invasive cover is greater than 10 percent of the area; • Providing fencing around plants to prevent animal damage; and • Providing fencing to prevent vandalism or damage caused by humans. 6.2 Contingency Plan If any portion of the :mitigation is not successful, a contingency plan will be implemented. Such plans are prepared on a case-by-case basis to remedy any aspects of the mitigation that do not meet the performance standards. The plan, if required, would be developed in cooperation with the City of Tukwila and Mr. Amon. 7.0 LIMITATIONS Within the limitations of schedule, budget, seasonal constraints, and scope -of -work, we warrant that this study was conducted in accordance with generally accepted environmental science practices, including the technical guidelines and criteria in effect at the time this study was performed, as outlined in the Methods section. The results and conclusions of this report represent the authors' best professional judgment, based upon information provided by the project proponent in addition to that obtained during the course of this study. No other warranty, expressed or implied, is made. ESA Adolfson March 2007 Page 19 La Tourelle Sensitive Areas Study 8.0 REFERENCES Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of Wetlands and Deepwater Habitats of the United States. FWS/OBS-79/31. U.S. Fish and Wildlife Service. Ecology (Washington State Department of Ecology). 1991. Shoreline Management Handbook: First Edition. Publication No. 90-45. Olympia, Washington. Ecology (Washington State Department of Ecology). 1992. The Growth Management Act and the State Environmental Policy Act: A Guide to Interrelationships. Publication No. 92- 07. Olympia, Washington. Ecology (Washington State Department of Ecology). 1994. Wetlands Regulations Guidebook. Publication No. 88-5. Olympia, Washington. Ecology (Washington State Department of Ecology). 1997. Washington State Wetlands Identification and Delineation Manual. Publication No. 96-94. Olympia, Washington. Ecology (Washington State Department of Ecology). 2004. Washington State Wetland Rating System for Western Washington Revised. Publication No. 04-06-025. Olympia, Washington. Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual. Technical Report Y-87-1. U.S. Army Engineer Waterways Experiment Station, Vicksburg, Massachusetts. Federal Register. 1982. Title 33: Navigation and Navigable Waters; Chapter II, Regulatory Programs of the Corps of Engineers. Vol. 47, No. 138, p. 31810. U.S. Government Printing Office, Washington, DC. Federal Register. 1986. 33 CFR Parts 320 through 330: Regulatory Programs of the Corps of Engineers; Final Rule. Vol. 51, No. 219, pp. 41206-41260. U.S. Government Printing Office, Washington, DC. Federal Register. 1988. 40 CFR Part 230. Guidelines for Specification of Disposal Sites for Dredged or Fill Material. Vol. 45, No. 249, Pages 85336-85357. U.S. Government Printing Office, Washington, DC. Federal Register. 1994. Changes in Hydric Soils of the United States. July 13. Washington, DC. Herrera Environmental Consultants, Inc. 2001. Gilliam Creek Basin Stormwater Management Plan. Prepared for the City of Tukwila Public Works Department, March 9, 2001. Seattle, Washington. Hruby, T, T. Granger, K. Brunner, S. Cooke, K. Dublanica, R. Gersib, L. Reinelt, K. Richter, D. Sheldon, E. Teachout, A. Wald, and F. Weinmann. July 1999. Methods for Assessing ESA Adolfson March 2007 Page 20 La Tourelle Sensitive Areas Study Wetland Functions Volume I: Riverine and Depressional Wetlands in the Lowlands of Western Washington. WA State Department Ecology Publication #99-115. Hitchcock, C.L., and. A. Cronquist. 1973. Flora of the Pacific Northwest: An Illustrated Manual. University of Washington Press, Seattle, Washington. King County Department of Surface Water Management. 1990. The King County Sensitive Areas Folio. King County. 2004. The Soil Survey of King County. U.S. Department of Agriculture Natural Resources Conservation Service 2003. King County GIS revised. Munsell Color. 2000. Munsell Soil Color Charts. Greta Macbeth, New Windsor, New York. Snyder, D.E., P.S. Gale, and R.F. Pringle. 1973. Soil Survey of King County Area, Washington. U.S. Soil Conservation Service, Washington, DC. NRCS (Natural Resources Conservation Service). 1995. Hydric Soils List for Washington. Revised December 15, 1995. NRCS (Natural Resources Conservation Service). 1998. Field Indicators of Hydric Soils in the United States, Version 4.0. G.W. Hurt, P.M. Whited, and R.F. Pringle (eds.), United States Department of Agriculture, Ft. Worth, Texas. Tukwila Department of Community Development. 2004. Tukwila Wetland/Watercourse and Buffer Map. USFWS (U.S. Fish and Wildlife Service). 1988. National List of Plant Species that Occur in Wetlands: Northwest (Region 9). Biol. Rpt. 88(26.9). United States Department of Interior, Washington, DC. USFWS (U.S. Fish and Wildlife Service). 1988. The National Wetland Inventory, Des Moines. quadrangle. 1995..King County GIS revised 2004. USFWS (U.S. Fish and Wildlife Service). 1993. 1993 Supplement to List of Plant Species that Occur in Wetlands: Northwest (Region 9). Washington State Department of Fish and Wildlife. 2005. Washington State Department of Fish and Wildlife Priority Habitat and Species Map. Vepraskas, M.J. 1999. Redoximorphic Features for Identfing Aquic Conditions. Technical Bulletin 301. North Carolina Agricultural Research Service, North Carolina State University, Raleigh, North Carolina. ESA Adolfson March 2007 Page 21 La Tourelle Sensitive Areas Study FIGURES AND PHOTOGRAPHS ESA Adolfson March 2007 - WASHINGTON STATE KITSAP t awr ecfin, PROJECT SITE A 1Y5TN w 5T r,mT S 17611 ST PArvaP SOURCE: Rand McNally & Company, 2006. La Tourelle Sensitive Areas Study . 207119 Figure 1 Vicinity Map Tukwila, Washington RLE NAME: Fl9O2_Wpoal CREATED BY: JAB / DATE LAST UPDATED: 03/05/07 SOURCE: WDFW PHS, 2005; NWI, 1998; King County GIS, 2004. La Tourelle Sensitive Areas Study . 207119 Figure 3 National Wetland Inventory Map Tukwila, Washington S152St S152St S152St S152PI 4405 Ramp S 156 St S160St S162St PROJECT SITE co e V rn a > < to S 163 PI Slade Way n u m e S164 v > v, v a v Legend ...... Project Site 11.1 type 3 Wetlands (City Owned Parcels) IMJ Type 3 Wetlands (Privately Owned Parcels) Type 2 Wetlands (City Owned Parcels) Type 2 Wetlands (Privately Owned Parcels) ®Type 1 Wetlands Parks City Owned Parcels Basins Streams Buffer Type 3 (50') ):(+ Buffer Type 2 (80') Parcels Streets S 166 St SOURCE: City of Tukwila, July 2004. La Tourelle Sensitive Areas Study . 207119 Figure 4 City of Tukwila Wetlands/Water Course and Buffer Map Tukwila, Washington Legend Streams RASO Site NfLCS 6.61JRGO Soils gm Hod. Non -Hydric Soil Key AkF, Aldenvood and Kitsap Soils, Very !Steep AMC, Arenta, Aldetwood Maierlal, 6 to 15 PereentSlope Ng, Newberg Silt Loam • . Ur, Urban Land W, Water VVo, WoodinVille Silt Loam . . SOURCE: NRCS SSURGO Soils, 2003; King County GIS, 2004. La Toureile Sensitive Areas Study . 207119 Figure 5 Soils Map Tukwila, Washington WETLAND A 4,026 SF WETLAND B 3.070 SF WETLAND C 1,562 SF PROPERTY BOUNDARY LEGEND DP®1 Existing Wetland Existing Buffer Data Plot SOURCE Mead Gilman and Associates, 2007 La Tourelle Sensitive Areas Study . D207119.0X Figure 6 La Tourelle Wetland Map Tukwila, Washington NOTE: LOTS 9,10 AND 11 WOULD NOT BE DEVELOPED IF ONSITE MITIGATION IS PURSUED. SOURCE: Barghausen Consulting Engineers. 2007 La Toureile Sensitive Area Study . D207119.0X Figure 7 La Tourelle Wetland Impacts Tukwila, Washington W DP J4 v v. w WF --k3 WETLAND ENHANCEMENT AREA =3,070 SF 4, WF—WL2 DP -5 WETLAND CREATION AREA = 808 SF (GEOTECHNICAL ENGINEER TO VERIFY AVAILABILITY OF WATER SOURCE) 4P7.I 353 SF ADDITIONAL BUFFER TRACT 998 TRA I ) I h' BUFFER REDUCTION 495 SF 1,816 SF ADDITIONAL BUFFER 50' AVERAGE BUFFER BOUNDARY o m L t Feet a 236' 256 SF Ar1111TV1AIAI DI Icon 11✓VI 1 IVI'arm- 100,J1 -11 -CIN BUFFER S.F. . / REDUCTION \ ,%//1,664 SF 50' STANDARD BUFFER BOUNDARY NOTE: LOTS 9, 10 AND 11 COULD NOT BE DEVELOPED IF ONSITE MITIGATION IS PURSUED. C C27 C r PROPOSED PLANTING SCHEDULE SCIENTIFIC NAME COMMON NAME WETLAND CREATION T1uJa plicate Cornus eerieea Rubue epectabllle Salix eltchenele Rosa pleocarpa Tolmeia menzleeII Athyrlum Felix -famine WETLAND ENI-IANCMENT Thuja plicate Comae eerIcea Rosa pleocarpa 6,.'11x ToMela menzleeli Western Red Cedar Red Twlg Dogwood Sa Imonberry Sltka Willow Clustered Wild Rose Piggy -back Plant Lady Fern Western Rad Cedar Red Twig Dogwood Clustered Wild Rose Sltka WIIIau Piggy -back Plant QTY SIZE SPACING SEED MI)( SEED ALL AREAS OF DISTURBED SOIL WITW THE FOLLOWING MIX: Alopecurue geniculetue Water Foxtall 60% Agroette etolonifsrra Redtop 3m1t Feetuca rubra Red Fescue Im% APPLICATION RATE: 45 LBS./ACRE BUFFER REDUCTION AREA = 2,159 SF BUFFER ADDITION AREA = 2,425 SF BUFFER AVERAGE AREA = 28,400 SF BUFFER REQUIRED = 28,100 SF 1 GAL 1GAL 1GAL I GAL. IGAL (GAL. I GAL. IGAL 1 GAL IGAL 1 rdl 1 GAL 9' OC. 4' OC. 4' OC. 4' OC. 4' OC. 4' O. 4' OC. 9' OC. 6' O. 6' O.C. 6' O. 6' O.C. LEGEND Wetland Creation Wetland Enhancement Buffer Reduction Buffer Addition SOURCE Barghausen Consulting Engineers, 2007 La Tourelle Sensitive Area Study. D207119.0X Figure 8 La Tourelle Wetland Mitigation Concept Tukwila, Washington La Tourelle Sensitive Areas Study Photo 1. Amon property facing northwest from the intersection of South 160th Street and 53rd Avenue South (southeast corner of lot). (October 4, 2005) Photo 2. East -facing view of Wetland A. (February 28, 2007) ESA Adolfson March 2007 La Tourelle Sensitive Areas Study Photo 3. Wetland A. (October 4, 2005) Photo 4. Wetland B soils. (October 4, 2005) ESA Adolfson March 2007 La Tourelle Sensitive Areas Study 1,1 ...,' •;•;••,,IV:,•4:' •` • .• ..<. • ' • - . . ,'' 4;f.' ,/"? I - ..'-':. , -; :'".• , .• 4 ,..,-.. * r ... -'. 'r'4, - ' ' '1. " -" '.Ail' • ,..7-'9.• w.;-..• •i.,-.''1...>-.",,,'",I,..t• - ........,. - ,0 _ 1 • ,. , ft„..',..„...7,.'."..' .., "...I " .,..„-"." ' -•,- ,.„•-' y, ";- : .....„.,.,.., „;j.. -.._•-?•,.-: -•.-.7..;...-..:- •,-••,• C.: -.7.-- . /7,...• ... ' , eVtA.t.:- •,..-,, i , . .., • , 1 -, -, • . - IA- • .)\ ,,-Y - is cot s,..,-,-•,- -,..i.,„••<1.- ,. ....... . • -,,, - ,-...'•-,, '. ', ;^ v.,-14•' ,..... , --, .c., i, 4-S-.— .5",,t7., 4; ,,.., •.! \ ,s v.. , ./. P." Photo 5. Wetland C. (October 4, 2005) Photo 6. A spring fed water drainage flowing on top of compacted soils, east of Wetland C. Soil compaction is due to the City of Seattle underground water pipeline. (February 28, 2007) ESA Adollson March 2007 La Tourelle Sensitive Areas Study Photo 7. Typical upland vegetation within the Amon property site. (October 4, 2005) ESA Adolfson March 2007 La Tourelle Sensitive Areas Study APPENDIX A: METHODS USED TO EVALUATE WETLAND CHARACTERISTICS ESA Adolfson March 2007 Appendix A La Tourelle Sensitive Areas Study Wetland Definition Wetlands are formally defined by the U.S. Army Corps of Engineers (Corps) (Federal Register 1982), the Environmental Protection Agency (EPA) (Federal Register 1988), the Washington Shoreline Management Act (SMA) of 1971 (Ecology, 1991) and the Washington State Growth Management Act (GMA) (Ecology, 1992) as ... those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas (Federal Register, 1982, 1986). In addition, the SMA and the GMA definitions add: Wetlands do not include those artificial wetlands intentionally created from non - wetland site, including, but not limited to, irrigation and drainage ditches, grass - lined swales, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape amenities, or those wetlands created after July 1, 1990 that were unintentionally created as a result of the construction of a road, street, or highway. Wetlands may include those artificially created wetlands intentionally created from non -wetland areas to mitigate the conversion of wetlands. Methods defined in the Washington State Wetlands Identification and Delineation Manual (Ecology, 1997), a manual consistent with the U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), were used to determine the presence and extent of wetlands on the subject property. Washington state and all local governments must use the state delineation manual to implement the SMA and/or the local regulations adopted pursuant to the GMA. The methodology outlined in the manual is based upon three essential characteristics of wetlands: (1) hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three characteristics must all be present in order to determine that an area is a wetland (unless problem areas or atypical situations are encountered). These characteristics are discussed below. Vegetation Plants must be specially adapted for life under saturated or anaerobic conditions to grow in wetlands. The U.S. Fish and Wildlife Service (USFWS) has determined the estimated probability of each plant species' occurrence in wetlands and has accordingly assigned a "wetland indicator status" (WIS) to each species (USFWS, 1997). Plants are categorized as obligate (OBL), facultative wetland (FACW), facultative (FAC), facultative upland (FACU), upland (UPL), not listed (NL), or no indicator status (NI). Definitions for each indicator status are listed in the Glossary. Species with an indicator status of OBL, FACW, or FAC are considered adapted for life in saturated or anaerobic soil conditions. Such species are referred to as "hydrophytic" vegetation. A (+) or (-) sign following the WIS signifies greater or lesser likelihood, respectively, of the species being found in wetland conditions. ESA Adolfson March 2007 Appendix A-1 La Tourelle Sensitive Areas Study Areas of relatively homogeneous vegetative composition can be characterized by "dominant" species. The indicator status of the dominant species within each vegetative stratum is used to determine if the plant community may be characterized as hydrophytic. The vegetation of an area is considered to be hydrophytic if more than 50% of the dominant species have an indicator status of OBL, FACW, or FAC. The scientific names and wetland indicator status for each plant discussed in this report are presented in Appendix B. Soils Hydric soils are indicative of wetlands. Hydric soils are defined as soils that are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part of the soil profile (Federal Register, 1994). The Natural Resources Conservation Service (NRCS), in cooperation with the National Technical Committee for Hydric Soils, has compiled lists of hydric soils (NRCS, 1995). These lists identify soil series mapped by the NRCS that meet hydric soil criteria. It is common, however, for a map unit of non -wetland (non - hydric) soil to have inclusions of hydric soil, and vice versa. Therefore, field examination of soil conditions is important to determine if hydric soil conditions exist. The NRCS has developed a guide for identifying field indicators of hydric soils (NRCS, 1998). This list of hydric soil indicators is considered to be dynamic; revisions are anticipated to occur on a regular basis as a result of ongoing studies of hydric soils. Anaerobic conditions create certain characteristics in hydric soils, collectively known as "redoximorphic features," that can be observed in the field (Vepraskas, 1999). Redoximorphic features include high organic content, accumulation of sulfidic material (rotten egg odor), greenish- or bluish -gray color (gley formation), spots or blotches of different color interspersed with the dominant or matrix color (mottling), and dark soil colors (low soil chroma) (NRCS, 1998; Vepraskas, 1999). Soil colors are described both by common color name (for example, "dark brown") and by a numerical description of their hue, value, and chroma (for example, 10YR 2/2) as identified on a Munsell soil color chart (Munsell Color, 2000). Soil color is determined from a moist soil sample. Hydrology Water must be present in order for wetlands to exist; however, it need not be present throughout the entire year. Wetland hydrology is considered to be present when there is permanent or periodic inundation or soil saturation for more than 12.5% of the growing season (typically two weeks in lowland Pacific Northwest areas). Areas that are inundated or saturated for between 5% and 12.5% of the growing season in most years may or may not be wetlands. Areas inundated or saturated for less than 5% of the growing season are non -wetlands (Ecology, 1997). Indicators of wetland hydrology include observation of ponding or soil saturation, water marks, drift lines, drainage patterns, sediment deposits, oxidized rhizospheres, water -stained leaves, and local soil survey data. Where positive indicators of wetland hydrology are observed, it is assumed that wetland hydrology occurs for a sufficient period of the growing season to meet the wetland criteria, as described by Ecology (1997). ESA Adolfson March 2007 Appendix A-2 La Tourelle Sensitive Areas Study APPENDIX B: COMMON AND SCIENTIFIC NAMES OF PLANTS AND THEIR WETLAND INDICATOR STATUS ESA Adolfson March 2007 Appendix B Amon Property Wetland Delineation PLANT SPECIES LIST FOR THE AMON PROPERTY PROJECT, IDENTIFIED ON OCTOBER 4 2005 COMMON NAME1 SCIENTIFIC NAME' WETLAND INDICATOR STATUS2' 3 TREES big -leaf maple Acer macrophyllum FACU Douglas fir Pseudotsuga menziesii FACU* red alder Alnus rubra FAC SHRUBS AND VINES Douglas spiraea Spiraea douglasii FACW English holly Ilex aquifolium NL evergreen blackberry Rubus laciniatus FACU+ Himalayan blackberry Rubus armeniacus FACU Indian plum Oemleria cerasiformis FACU Japanese knotweed Polygonum cuspidatum FACU* tall Oregon rape Berberis nervosa NL oceanspray Holodiscus discolor NI Pacific blackberry Rubus ursinus FACU salal Gaultheria shallon FACU* salmonberry Rubus spectabilis FAC+ snowberry Symphoricarpos albus FACU vine maple Acer circinatum FAC - HERBS bracken fern Pteridium aquilinum FACU cleavers Galium aparine FACU climbing nightshade Solanum dulcamara FAC+ colonial bentgrass Agrostis tenuis FAC Cooley's hedge -nettle Stachys cooleyae FACW creeping buttercup Ranunculus repens FACW curly dock Rumex crispus FAC+ common dandelion Taraxacum officinale FACU English ivy Hedera helix NL English plantain Plantago lanceolata FACU+ field horsetail Equisetum arvense FAC giant horsetail Equisetum telmateia FACW hairy cats -ear Hypochaeris radicata FACU herb Robert Geranium robertanium NL lady fern Athyrium filix femina FAC+ orchardgrass Dactylis glomerata FACU pig -a -back -plant Tolmiea menziesii FAC pineapple weed Matricaria matricarioides FACU red clover Trifoliumpratense FACU reed canarygrass Phalaris arundinacea FACW Small -fruited bulrush Scirpus microcarpus NI- OBL skunk cabbage Lysichitum americanum OBL soft rush Juncus effusus FACW sword fern Polystichum munitum FACU tall fescue Festuca arundinacea FAC - ESA Adolfson March 2007 Appendix B-1 Amon Property Wetland Delineation 2 Common names are primarily from Flora of the Pacific Northwest (Hitchcock and Cronquist, 1973). Scientific names are as listed in Hitchcock and Cronquist (1973). Scientific names change over time as botanists reevaluate plant species. The scientific name currently listed in the "Washington Flora Project" database (http://flora.ilangainc.com) is given in parentheses if it is different from that listed in Hitchcock and Cronquist (1973). Key to Wetland Indicator Status codes — Northwest Region (Source: USF WS, 1997): OBL Obligate: species that almost always occur wetlands under natural conditions (est. probability >99%). FACW Facultative wetland : species that usually occur in wetlands (est. probability 67 to 99%), but are occasionally found in non -wetlands. FAC Facultative: Species that are equally likely to occur in wetlands or non -wetlands (est. probability 34 to 66%). FACU Facultative upland: species that usually occur in non -wetlands (est. probability 67 to 99%), but are occasionally found in wetlands. UPL Upland: species that almost always occur in non -wetlands under :normal conditions (est. probability >99%). NL Not listed: species that are not listed by USFWS (1997) and are presumed to be upland species. NI No indicator: species for which insufficient information is available to determine status, or which were not evaluated by USFWS. + indicates a species that is more frequently found in wetlands indicates a species that,is less frequently found in wetlands * identifies a tentative assignment based upon either limited information or conflicting reviews 3 Where a range of Wetland Indicator Status ratings are given for a genus, the range reflects the species for which ratings are provided in the USFWS (1997) list. Some species within the genus may be NI or NL. ESA Adolfson March 2007 Appendix B-2 La Tourelle Sensitive Areas Study APPENDIX C: DATA SHEETS ESA Adolfson March 2007 Appendix C .Routine Wetland Determination . State Weiland Delineation Manual or 1987 Corps Wetland Delineation Manua]) Dater I -- y- 05 county fe t . state: {�ri�.sk srr/R:• Commtmity ID: r�qt . Transect ID:�! Plot ED: J 1 1 • -g . VEGETATION (For strata, indicate T = tree; S = shrub; H herb; V = vine) Dominant Plant Species Stratum % cover Indicator Dominant Plant Species Stratum CQVer TndicatoI • S 5 50 zo r5 EACH-. 1 !!t' t4 HYDROPHYTIC VEGETATION IlNDICATORS % of dominanys•OBL, FACW, & FAC 10P/0 Check all indicators that apply- & explain below: Visual observation of plant species growing in--. areas of prolonged inundation/saturation Morphological adaptations • Technical Literature Hydrophytievegetadon present? Rationale for decision/Re matks; • HYDROLOGY Is it the growing season? Based on: no. • , Water Marks: yes on Sediment Deposits: yes CO Drift Lines: yes Drainage Pattens: yes no Dept. of inundation: Mi'1101$6141" inches Depth to free water in pit tM freutqc inches Depth to saturated soil: 1\)01 Or> 5q'1. inches Oxidized Root (live toots) Channels <12 in. yes FAC Neutral.: yes 11 Q Loral Soil Survey: yes no Water -stained Leaves yesno Check an that apply & explain Below: Stream, Lake or gage dam: _ Aerial photographs: Other. Other (explain): Wetland hydrology presenty yes BO Rationale for decisioniR :mi is: 4- 1_:61'1 f� *t.C..e31 14-1' 171.6 a.y6W � 1 t ?aff ro.551 on o d- rs "Ass v,r2,4. a - Gl . t �/tiIo I G / k :ct- s coAL, p 6.o rt wc, c9 l rci seaor, , SOILS rr AlOtaillA/0001 Map Unit Name Ar P •(Series & Phase) Taxonomy (subguup) 0100(arrt.ieC(l Drainage Class /n /e,J l I %# (Illi 110cQ • Field observations canfnn Yes No mapped type? Profile Description Depth {'orches) Horizon Matrix calor (Munsell moist)_ Mottle colors (Mtmsell moist), Mottle abundance size & contrast • • Textnre, concretions, , structure, etc. ' • IOiR 1/i 05y LYz .from dis64 �nd�a loam L Dowing afsoil profile (match description) • Hydric Sall Indicators: (check all that apply) Hiitosol HisticEpipedad . &iIfidic Odor Altaic Moisture Regime Reducing Conditions Gleyed or Low-Chroma (1) matrix Ma ix chrvma 52 with mottles ' _ .. I r Mg orFe Concretions ' ..... -. . High Organic Content in Surface Layer of Sandy Soils • Organic Streaking in Sandy Soils ' • .Listed on National/Local Hydric Sods List Other blain m rcmerks) . Hydric sous present? Rationale for decisianfR.emadcs • no or /et.Jdif so .5 Wetland Determination (circle) Hydrophytic vegetation present? Hydric soils present? Wetland hydrology present? no no Is the sampling point no' ' within a wetland? mo Rationalenzemurks:, VQ A•4{1jl'fVTI�'j ._ _L ... • 5011j }1,1 bxt V • hs419.1051 WseN Got Gtar mriovrat: 4 ieie�,ce. o% �1 c r�0f11- ��e O',riA NOTES:. 501 1 Sof Peet Sht��t Ai j-2-" . LJ no/A et -601' c' • ldt2 sand alien anti b !i saki) ifereo0 Puri< - - kele. a 5 Ctinc w r m olepYgs54. et-vek lits r rain Revised 4197 • Project/Site: Applicant%owner: i� J .� tr Investigator(s): "TY 1 l0,r���11 i -0 ciU1 Do Normal Circumstances exist pa the site? (, Is the site significantly disturbed (atypical situation)? Is the area a potential Problem Area? . Explanation of atypical orproblem.area: • VEGETATION (For somata, indicate T= tree; S = shrub; H = herb; V= vine) DATA FORM 1(Revised) Routine Wetland Determination . (WA State Wetland Delineation Manual or 1987 Corps Wetland Delineation Manual) Altman Date: )o- 05 Cs s - 41,..t_fs. h S/T/R Community' ID: 1 p 1 Transect ]Li: 1 Plot ID: • Dominant Plant Species Stratum _ % cover Indicator • Dominant Plant Species Stratum % cover Indicator top )- rPv' 110L rANNtil fitl& t.,i ` Flt�o T %TT' NL • % of dominant#,OBL, FACW, &FAC Check all indicators that apply & explain below: Visual observation ofplant species growing in areas of prolonged inundation/saturation Morphological adaptations Technical. Literature PAO .Fil�,�. L rig Itittln • Physiological/reproductive adaptations Wetland plant database Personal knowledge of regional plant comaamities . Other (explain) Hydraphytic vegetation present? yes n'o' Rationale for decision/Remarks. Na hi HYDROLOGY Is it the growing season? Based on: r• . yes ' soil temp (record other (explain) ue3t OP, Dept of inundation: t reset orches Depth to free water in pit p liinches Depth to saturated soil: rf I j #j rinohes Chock all that apply & explain beldw: Stream, Lake or gage data: _ Aerial photographs: Wetland Hydrology present? Rationale for decision/Remarks: 1 :i Water Marks: yes no on Sediment Deposits: yes Drift Lmes: ' yes. Drainage Patterns: yes no OxidizedRoot (live coo Charnels <1? in. yes o Local Sod Survey: yes no FAC Neutral: yes . no Walar-stained Leaves yessco ' Other (explain): Other. yes SOILS Map Unit Name l� * J )C)L2 �t,a ?oc {Series & Phase) Taxonomy (subgroup) • Drainage Class Field observations confirm Yes No mapped type? Profile Description Depth (mcbes) • Horizon D-1 A Matrix color (Munsell • moist) Mottle colors (Mansell moist). Mottle abundance sue & conhast Texture, concretions, strum:re; etc. • • oa►1100. -Ft f unci;sr SoraW boa D.rwing of sod .profile (match description) Hydric Sal Indicators: (check all that apply) lEstosoi • ` • ,. • Histiq fipipedad Sadie Odor . • - - Aquic Moisture Regime Reducing Conditions . Gleyed orLow-Ctunma (=1) mairix Hydric soils present? yes Rationale for decisioa/Remarks: Matrix cbrama 2 with mottles •• • • • • • - Mg or"Fe•Concretions • • High Organic Content in Surface Layer of Sandy Soils Organic Sttea!thzgiu SandySofs Listed on NalionaULocal Hydric Sons List Other (explain in remarks1 )1(611.0ren4 • • bio RP v ont 194 . (r =� Wetland Determination (circle) Hydrophytic vegetation present? Hydric sods present? Wetland hydrology presend Rationa le/Remaz ks: 3 yes yes Yes . . Is.the sampling point • yes within a wetland? otvt.elev3- art (tor- lei- • NOTES: Revised_ 4197 SOILS - Map Unit Name Are,In AkrL J (Series & Phase) Taxonomy (subgroup) , Drainage Class Field observations confirm Yes No mapped type? Profile Description Depth .(inches). Horizon Matrix color (Mtmsell moist). Motile colors (Munsell moist). Mottle abundance size & contrast • Texture, concretions, . structure, etc. d-7 ad, 4/avi 7—/6 cLEy 1 •5:/,en Op. 44 �,s -1,ct • Drwing'sorl profile (match description) Hydric Soil indicators: (check all that apply) Histosol • • •E stir Epipedori . Sulfidic Odor x .Agaic•Moisture Regime • • Reducing Conditions Gleyed or Low-Chroma (1) matrix X Matrix chrome 52 with mottles • ••• Mg orPe Coacretiaes • High Organic Content in. Surface Layer of Sandy Soils Organic Streaking in Sandy Soils • Listed on Nadonal/Laca1 Hydric Soils List • Other (explain inn -minks) Hydric sells present? Rationale for decisi • So :Ls 1, Iva .W f2UJt vim.. . e9 no end, /i& nil— el -r4 • a; nhr f (Ply LI Wetland Determination (circle) Hydrophyttc vegetation present? ag ria Hydric soils present? 4va. no Wetland hydrology pres end ,?=" la the sampling point no within a wetland? • ria Ratrona) ernurks: -fig Afit. erdeti'ia .er-rd Mt -C, NOTES: /h `S�La/Suftigo Dlu-al T4 irk,/ aowid ave- ia, Anigi yy, ��rTha jrL4dIi3 �cf �4-#'1•4•P; i2�Scals ei37/•)*c .7L dare'Wr' artl61. .4.''acerce • Ahs/J��s Y,, Revised 4197 / JJ.. �� 4Al f, keit-- Elifar1TI/y jtti/J TMJ Ser• .e'E ,a f°vY/. Dig -3 WL SSS A4E-A- 741.74 tpr ir.. r 7� . I-1 rc \a kk.s Gaols. o, • ft,:i.5 ur'tidr/Leapt • 14 E IVv feclihnit OPHYTIC VEGETATION INDICATORS. of dominen OBL, FACW, & FAC I OD a 10 051. FA til.) F,1)11s Si01424;lS 10 Fes+ 80 15 0.5 .FACS Check all indicators that apply & explain below: Visual observation of plant species growing in areas of prolonged inundation/saturadon Morphological adaptations - Technical Literature • , Dorntr , • • Physiological/reproductive adaptations Wetlagd plant database Personal lozowledge of regional plant communities _ Other (explain) X Hydrophytic vegetation present? y`es no xenon= for decnsronrxcmancs:• ktub e, oedthtitiM f rese-M- • • ::• . . U i HYDROLOGY . " ^ . Is it the growing season? : yes .. 1 Based an: • sail temp (record temp , Water Marks: yes no Sediment Deposits: yes 0 om• Drift Lines: yes no ' Drainage Patterns: yes IIo other (=Plain) /I, y Dept of immdation: Af ptllfzUlA1r inches Oxidized Root (live mots) Channels <12 in. o, no Local Soil Survey: yes o0 _ r•. j Depth to free water in pit: f " i• FrSLI•� itches FAC Neutral: o c 6-: Q Water -stained leaves yes no Depth to saturated soil: u l( L intdnes Check all that apply & explain below: Stream, Lake or gage data: Other (explain): (. I , • I.. ti Y.p� u -iiI fail/ 1 V1 L/ u,/ 5PAStM A.40' Aerial photographs: Other: Wetland liydrology present? yes • no Rationale far decision/Remarks. Lill , SGi OAPCY IA AAt?Ai u r<124c . eul. -l- �c incl SOILS Map Unit Name .(Series & Phase) Taxonomy (group) vcwAIMvcz4 Drainage Class Field observations confirm Yes mapped type? No Profile Description Depth • (inches) Hor72on Matrix color (Mtmsell moist) Mottle colors (Munsell moist) Mottle abnnnian size & contrast Texture, concretions, structure, etc. 0-10 10 — Its )0`112. th, a,6/ r 60/Wm 61-6 TNI t. 1mai • DoSwing of soil .pmfile (match description) • Hydric Soil Indicators: (check all that apply) Histosol • • Histie Epipedari X Sulfide Odor Aquic Moistrae Regime Reducing Conditions Gleyed or Low- u 11 • (=l) matrix Hydric sails present? no Rationale for dec si,i. )< 'Matrix ciroma S a with mottles • Mg -or Fe Concretions High Organic Content in Surface Layer of Sandy Soils Organic Streaking in Sandy Soils . = • Listed on National/Local Hydric Sdils List Other (explain in remarks) 1IJ c�Xovwa. W IA.4145 Sri l dcid Y • Wetland Determination (circle) Hydrophydc vegetation present? Hydric soils present? Wetland hydrology present? Rationale/Retnarks: Ito no Is the sampling point no wiles &wetland? fill 3 faAtilltie6 ALF no NO'T.CS: kt,• 61Gh�cJi rat69 St); $ ext4- ut t Add pbf. 7 6Qot nottMu„i mothstfive,e4 S.'T- 41Q 16y' Ch C Revised 4/97 DATA FORM 1 (Revisad) Routine Wetland Determination (WA State Wetland Delineation Manual or 1987 Corps Wetland Delineation MnnuaI) Project/Site: IAQ QY1 ?taller•. • Applicant/ay/nen �l}Q, J-l�JVO'r.. Investigator(s): tJ -1< Y tO1 q 1.�, . • W Date: 16 . q..- 05- County. Km • � 1 . Slawa sttt,t(r Do Normal Circumstances exist on the site? Is the site significantly disturbed (atypical situnticn)? yes �r. Is the area a potential Problem Area? .yes :': Explanation of atypical orproblem area: Communitlr ID: U •iQ4 . Transect 1D.: P . Plot ID: �Q` �(} ' ' a��� VEGETATION (For stratn,'indicate T =tree; S= shrub;11= herb; V =vine) Dominant Plant Species Stratum % cover Indicator Dominant Plant Species Stratton % cover • Indicator Pr til tli:A OA-041161itde /4• HV FAN�Wj ft011(10 SD • • . 1 Yr{._: • il t I fl tl5 nth rr `r )b FAL • • BYDROPHYTIC VEGETATION INDICATORS• °%,. of dominants OBL, FACW, & FAC r arO fla • • Check all indicators that apply & explain below:- Visual ebseryation of plant species growing in . Physiological/reproductive adaptations • BIM of prolongedinundation/saturation Wetland plant database Morphological adaptations Personal knowledge of regional plant communities Technical Literature Other (explain) • Hydropbytic vegetation present? no Rationale for decision/Remarks:�, ' _ • Opt Flo:m e �-w , ' HYDROLOGY . Is it the growing season? yes....no • Water Marks: yes 19 as Sediment Deposits: yes no Based on: sot? temp (record temp ) Drift Lines: yes no Drainage Patterns: yes i to %JA1 other (explain) I Dept of inundation: -- inches Oxidized Reat (live roots), Local, Soil Survey: yes no Channels <12 in. es. /o' _ Depth to free water in pit; _l_ inches FAC Neutral: {rio Water =stained Leaves yes gm Depth to saturated soil: • ' ; inches Check all that apply & explain below: Stream, Lake or gage data: Other (explain): Aerial photographs: Other: Wetland hydrology present? . yes . ' {, . •, .. ; .. • Rationale for depiaio emark5:'v 1( No 7i 4 C r,,,s. j , ref : ,2pE� �-- v Zia Aa l�a�"FL` (�G c -f C SOILS • Map Unit Name .(Series & Phase) Taxonomy (subgroup) • ,Drainage Class Field observations confirm,,. Yes No mapped type? • ., •,t Profile Description -t. r Depth .. ('orches) Hatizon., . -1D h-16 ft Matrix color (Munsell i moist) Mottle colors (Mtmsell moist) Mottle abundance size & contrast • Textnre, concretions; stJ'mcune, etc, 9.5Y Ys r 511vA4 lQ I• Drawing ascii profile (match description) - • • •. • Hydric Soil Indicators: (check all that apply) Histosol lade Epipedoti . .Sutfidic Odor Agoic Moisture Regime Reducing Conditions Gleyed or Low Chroma (=1) matrix Matrix chrome 5 2 with mottles Mg or Fe Concretions High Organic Content in Surface Layer of Sandy Soils Organic Streaking in Sandy Soils ' • • Listed on NaticnaYLocal Hydric Sods List Other (explain in remarks) Hydric sons present? yes Rationale for decision/Remarks: • A.+4 7rS pa.04. Wetland Determination (circle) Hydrophyac vegetation present? ( ) Hydric sods present? yes Wetland hydrology present? yes Rationale/Remarks: bnl y no Is the sampling point within a wetland? Yes NO +',S: •,•••',. . ,j1 W� Ct del 5-741/,? /Pa/; , P/- 9 .so:es- ate Revised 4/97 =c l� ; prd stn;-/ . r Minnie Dhaliwal - La Tourelle proposal- Ale number L06-089 Page 1 From: To: Date: Subject: CC: Hi Alexia, Minnie Dhaliwal adorsch@barghausen.com 01/30/2007 12:58 pm La Tourelle proposal- File number L06-089 Joanna Spencer As per our phone conversation last week the following information is needed to further review your application: 1. Need to reflag wetlands on site as a lot of the flags are missing. 2.Need functional analysis of the wetlands and the proposed mitigation proposal. 3. Need Corps jurisdictional determination. 4. Please provide $3000 payment made out to the City of Tukwila for the peer review of the geotechnical report. Let me know if you have any questions. Minnie Dhaliwal Senior Planner City of Tukwila 206-431-3685 TO: City of Tukwila Department of Community Development File Number LAND USE PERMIT ROUTING FORM Building Planning Z Public Works L;, Fire Dept. Police Dept. '` Parks/Rec Project: ts%ti 1 rc_ p,reju i y A p Lam— Address: S 160crt., s j.' to v.4_ Iski^c . Date �(O transmitted: , I I �' Response requested by: Staff `�a. coordinator:kti-�" `� Date response received: REVIEWERS: Please specify how the attached plans conflict with your ADOPTED development regulations, including citations. Be specific in describing the types of changes you want made to the plans. When referencing codes, please identify the actual requirement and plan change needed. The Planning Division review does not supplant each department's ability to administer its own regulations and permits. However, project consistency at the Planning review stage is important to minimize significant later design changes. More than minimal design changes require further Planning Commission review, even if alteration is required to satisfy a City requirement. This further review is typically a minimum 60 -day process. Requirements based on SEPA (e.g., not required by an adopted development regulation) MUST identify the impact being mitigated, the policy basis for requiring mitigation, and the method used to calculate the mitigation required. Calculations of project impacts and the mitigation required (e.g., water capacity, road level of service analyses, or turning analyses) may be required of the applicant. COMMENTS (Attach additional comment sheets and/or support materials as needed.) r y- c e e� Uel re -V ri°J wu� -c (61-1c IA1 ttJ- Coe -LO toy — (tea -mac ` e Lw ko„,f2., tAu-' ( PS z -'-u C — Plan check date: Comments prepared by: NP Pd o re-� +G� L Ic„Ad S - r 07 -4 9,,�asPd 4-7 a.4 Update date: -N v .,2x us (-4: � a ,meq l� s_ City of Tukwila Department of Community Development File Number ©Fel LAND USE PERMIT ROUTING FORM TO: y'Building '- Planning Public Works Fire Dept. Police Dept. !_'_ Parks/Rec Project: 1 z ro p„re,it.;i ,L,t. 1 y p (4_ Address: S k %a sI' kr 3 vE S DateResponse transmitted: IO ,6 requested by: Staff coordinator:KIL )>ta `� Date response received: REVIEWERS: Please specify how the attached plans conflict with your ADOPTED development regulations, including citations. Be specific in describing the types of changes you want made to the plans. When referencing codes, please identify the actual requirement and plan change needed. The Planning Division review does not supplant each department's ability to administer its own regulations and permits. However, project consistency at the Planning review stage is important to minimize significant later design changes. More than minimal design changes require further Planning Commission review, even if alteration is required to satisfy a City requirement. This further review is typically a minimum 60 -day process. Requirements based on SEPA (e.g., not required by an adopted development regulation) MUST identify the impact being mitigated, the policy basis for requiring mitigation, and the method used to calculate the mitigation required. Calculations of project impacts and the mitigation required (e.g., water capacity, road level of service analyses, or turning analyses) may be required of the applicant. ILS s S COMMENTS (Attach additional comment sheets and/or support materials as needed.) �i cs i k_ ��do i' <C-3 Ve-ijAd r- W ��-- - T�- til— 4, LL-1-- s. L' b -' to -e-- C' �c —rfeAki Crksi, , ' • 4)- W":1 kru i i :sz Tyv l; c.Ck•E `ti thA. . .GLnJ dLa -i av,_ it-,- V�'l (,,T'l v` `u'`_' 6--A � .0-Le_'-�.J— cx....L<-1 �i` ti.�yv �� 0..4Q. A Q�8-c•� 6-)...1. ( 0,3-41-:<_,L �O-�-Q.Q/v' ?SS Y.e.Ain' tA-L-) CV— 1 "6, Plan check date: ' +t Comments Update date: //4 i /Veprepared by: I 7- Y) /4/? IN 'ROLE f ke:///41),/"V? 27/4.1/40/1 , �,oy. , t 1.('C)f , ede , 'YPE -syTr /47 1/ = ) �-, f 7 /'1/�,+�r,'/ // NL 4 f/t ,rte! ,ter � ` ice¢ 0 r ,,,,.g -e ift?E Pek 1 IN i ' %+ +iii `,..,� eriJ'r tY✓�,L'`' ,L�' /` "{/� .fi'_ .rTi�'Yi° '-�Tr `f ��*'( „`,� C?N / ,:t �G'dy ii , .i ° r t: t ?JN' 1/1 + 66e#7 14C '/77.1 Z!? 4 pf /7 Minnie Dhaliwal, Senior Planner City of Tukwila Planning Department 6200 Southcenter Boulevard Tukwila, WA 98188 CIVIL ENGINEERING. LAND PLANNING. SURVEYING. ENVIRONMENTAL SERVICES February 15, 2007 HAND DELIVERY RE: Submittal of Additional Wetland Information La Tourelle Property Permit No. L06-089 King County Parcel Nos. 537920-0005 and -0006 Our Job No. 12650 Dear Minnie: RECEIVED FEB 1 2JL1 COMMUNITY DEVELOPMENT On behalf of our client, Joe Amon, Barghausen Consulting Engineers, Inc. is submitting additional information for continued review. As you know, on-site sensitive areas include two centrally located isolated Category III wetlands and a very small portion (-16 square feet) of a third Category III wetland located in the northwest corner of the site. Our proposal includes filling two of the wetlands and preserving the northwest wetland and its buffer, as a Sensitive Area Tract. We have applied to the Army Corps of Engineers for a jurisdictional determination for the centrally located wetlands. A Wetland Delineation and Functional Analysis with proposed mitigation have been prepared by Adolfson Associates, Inc., and are enclosed. We understand that you also require a Sensitive Areas Study for the on-site wetlands, and will forward this to you as soon as it has been completed. Please contact me at this office should you require additional information. Thank you. Alexia D. Dorsch Assistant Planner ADD/pj [12650c.007] enc: Two (2) copies of the Wetland Functional Analysis with proposed mitigation prepared by Adolfson Associates, Inc., datcd February 1, 2007 cc: Joe Amon Ilon Logan, Adolfson Associates, Inc. Tom Barghausen, Barghausen Consulting Engineers, Inc. Raymond van der Roest, Barghausen Consulting Engineers, Inc. 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES • OLYMPIA, WA • TEMECULA, CA ♦ WALNUT CREEK, CA www.barghausen.com r SAAdolfson February 1, 2007 Joe Amon 16424 53rd Place South Tukwila, WA 98188 Subject: La Tourelle Subdivision Dear Joe: 333 SW Fifth Avenue Suite 600 Portland, OR 97204 503.226.8018 phone 971.544.0450 fax www.adolfson-corn ESA Adolfson (Adolfson) is pleased to provide you with the following analysis of wetland functions, impacts and mitigation for your 3.5 -acre property located at S 160th Street and 53rd Ave S in Tukwila, Washington. This analysis is based upon the Amon Property Wetland Delineation Report (Adolfson, 2005) that we completed for you under a previous scope of work. We have received the La Tourelle Subdivision Final Site Plan and Grading Plan prepared by Barghausen Consulting Engineers, Inc. (BCE) and reviewed the proposed development plan. The site plan proposes 16 generally rectangular lots around a single 40 -foot wide access road that terminates in a cul de sac near the center of the property. Wetland Functional Assessment Three wetlands (Wetlands A, B and C) occur on the property; however, the third wetland (Wetland C) largely lies offsite within a City of Seattle utility easement north of the property. The small portion (16 sf) of Wetland C that extends onto your property will not be impacted by the proposed development. Wetlands A and B provide low functions overall as described below. These wetlands are not hydrologically connected to each other or other site water features and are considered isolated by Adolfson. Wetland A (3,070 sf) is situated on a gentle north -facing slope that decreases to a shallow depression. The wetland is a palustrine scrub -shrub wetland that is seasonally saturated. No standing water or other evidence of surface ponding was observed during field investigation. The wetland provides some water quality improvement function because it is a depression with no outlet and contains persistent vegetation for rnost of its area. However, the wetland is generally flat and thus provides minimal detention of surface drainage. The wetland provides some reduction of flood flows and erosion because it is a depression with no outlet, but this function is also minimized by the generally flat topography and small size. The scrub -shrub vegetation and undisturbed upland buffer combine to perform wildlife habitat functions, although the presence of invasive vegetation species (Himalayan blackberry) and lack of habitat features (e.g snags, downed wood) decrease the wetland's ability to provide higher habitat functions. Wetland B (1,890 sf) is also a depressional palustrine scrub -shrub wetland with no apparent outlet. This wetland occurs in a linear depression and is seasonally saturated and occasionally inundated. Wetland B provides similar functions as Wetland A, but at lower levels. Both water quality improvement function and reduction of flooding and erosion on downstream aquatic resources are limited due to the small size of the wetland and lack of detention area. Wetland B contains more invasive vegetation species (Himalayan blackberry, Japanese knotweed and English ivy) which compromise the wetland's ability to provide native species richness and wildlife habitat function. I ESA. Joe Amon February 1, 2007 Page 2 Wetland Impacts and Mitigation Wetland A occurs in the west central portion of the property and Wetland B occurs near the center of the property. The location of the two wetlands and their required 50 -foot buffers make wetland impacts during site development unavoidable. Under the preliminary site plan, both Wetland A and Wetland B will be filled and Wetland C will not be impacted. In addition, the 50 -foot buffer of Wetland C will be set aside as a Sensitive Area Tract 999 along with steep slopes in the northwest portion of the property. According to TMC 18.45.090(B4), isolated Type 3 wetlands may be altered or relocated with an adequate mitigation or enhancement plan. Some of the functions currently performed by Wetlands A and B will be replaced on the site by elements of the proposed project. It is anticipated that the limited water quality improvement functions and the reduction of flood flows supplied by Wetlands A and B will be performed by the proposed stormwater facilities to be constructed on the site. As required by the City, all stormwater runoff created by the project will be detained and treated before leaving the site. In addition, site erosion will be minimized by the construction of proposed retaining walls, preservation of steep slopes and vegetation, and through implementation of an erosion and sediment control plan during construction. Wildlife habitat functions currently provided by Wetlands A and B will be replaced by proposed landscaping and tree planting as required by the tree replacement code. Due to site constraints, such as steep slopes, property shape and location of property boundaries, and valuable upland forest in the western portion of the property, mitigation of wetland impact onsite is not feasible or desired. Off-site mitigation will result in a greater functional values than those currently performed by Wetlands A and B. In comparison to onsite wetlands, the mitigation wetland would likely provide increased water quality improvement function, higher flooding and erosion functions, and provide a higher leve] of wildlife habitat function through increased habitat complexity and dominance of native plant species. It is anticipated that off- site mitigation will occur in the same watershed as the property and will be coordinated with the City of Tukwila. Please feel free to give me a call at 206.789.9658 with any questions. If I am not available, you may also speak with Teresa Vanderburg, who can be reached at the same number. Sincerely, ESA ADOLFSON 49/,, �.. Ilon E. Logan Wetland & Wildlife Biologist Cc: Teresa Vanderburg, ESA Adolfson Alexia Dorsch, Barghausen Consulting Engineers, Inc Tom Barghausen, Barghausen Consulting Engineers, Inc. SHANNON FiWILSON, INC. GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS March 8, 2007 Ms. Joanne Spencer City of Tukwila Public Works Department/Engineering Division 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 ECEIVED MAR 0 9 2007 TUKWILA PUBLIC WORKS RE: GEOTECHNICAL PEER REVIEW, LA TOURELLE PLAT, SOUTH 160TH STREET AND 53RD AVENUE SOUTH, TUKWILA, WASHINGTON Dear Ms. Spencer: ALASKA COLORADO FLORIDA MISSOURI OREGON WASHINGTON This letter presents the results of our review of a geotechnical engineering report for the above -referenced development in Tukwila, Washington. The development will be located on undeveloped land northwest of the intersection of South 160th Street and 53rd Avenue South. The purpose of our review is to offer an opinion as to the appropriateness and adequacy of the geotechnical report prepared by Otto Rosenau & Associates, Inc. (ORA). Our opinions are based on information contained in the report, a brief visit to the site, review of available project files and the City of Tukwila Municipal Code, and our experience with other projects in the area. The geotechnical report submitted to the City of Tukwila on August 15, 2006, presents the results of five borings and laboratory testing, and geotechnical recommendations for the proposed development. The borings were advanced to depths of 52 to 102 feet below the existing site grade. In general, the soil conditions observed in the borings consisted of loose to dense, silty sand in the upper 21 to 46 feet below grade, over stiff to hard, sandy silt; silt; and clay. Groundwater was observed at depths of about 3 and 18 feet below the existing grade. Standing water was observed nearby boring B-1 in the southwest area of 1:he site. Laboratory tests included water content determinations, dry density determinations, Atterberg limit determinations, grain size analyses, and direct shear tests. The report provides subsurface and surface site conditions; literature review findings; and conclusions and recommendations pertaining to seismic considerations, foundations, walls, slabs -on -grade, slope stability, drainage, and site preparation. 400 NORTH 34TH STREET • SUITE 100 P.O. BOX 300303 SEATTLE, WASHINGTON 98103 206.632.8020 FAX 206.695.6777 TDD: 1.800.833.6388 www.shannonwilson.com 21-1-20689-001 Ms. Joanne Spencer City of Tukwila March 8, 2007 Page 2 Our services included a brief visit to the project site and review of: SHANNON &WILSON. INC. ► The ORA geotechnical report. ► The Preliminary Plat Map for La Tourelle, dated November 27, 2006, prepared by Barghausen Consulting Engineers, Inc. ► Our files related to the Tukwila Interchange landslide study of 1966; our peer review of the Five Rivers Project, which was proposed near the intersection of South 159th Street and 53`d Avenue South in April 2003; and our peer review of the Hillcrest Residential Development at the intersection of South 160th Street and Slade Way, proposed in 1992. ► A report prepared by Landau Associates, Inc. entitled "Geotechnical Study, 53`' Avenue South and South 160th Street Improvements, Tukwila, Washington," dated March 5, 1991. REVIEW COMMENTS Based on our review of available documents, it is apparent that the project site is located in an area of potential prehistoric landsliding and contains steep slopes with mappable zones of groundwater seepage. As such, it should be classified as a Class 4 area of potential geologic instability, as stated in Section 18.45.120 of the Tukwila Municipal Code. ORA provided recommendations to reduce risk of future slope instability, which we agree are necessary for development on this site. However, we believe the following items should be addressed by ORA: ► During our site visit, we observed the following features, which were discussed in ORA's report: severely leaning trees on steep slopes; a prehistoric slide scarp at the far west end of the site; and near -surface wet soil conditions in a local topographical depression resembling a sag pond, which is labeled Wetland 3 on the ORA Site Plan. It is our opinion that additional explorations should be performed in the sag pond area to investigate for evidence of past landsliding. In our opinion, additional explorations upslope, in the middle, and downslope of the sag pond would be helpful in determining the risk of deep-seated sliding at this location. ► Section 6.0 of the geotechnical report indicates that groundwater was observed at a depth of 18 feet below the ground surface in boring B-1, and standing water was observed in proximity to boring B-1. We recommend that ORA discuss these conflicting observations. We also recommend that due to the presence of near -surface water at the site, the worst-case groundwater conditions (i.e., shallow groundwater levels) should be considered in the evaluation of slope stability and liquefaction potential. 21-1-20689-001-L1 /wp/LKD 21-1-20689-001 Ms. Joanne Spencer City of Tukwila March 8, 2007 Page 3 SHANNON &WILSON. INC. ► Section 10.2 of the geotechnical report presents ORA's opinion that liquefaction was "medium to high along the western portions of the site" and "low to medium along the eastern portions of the site." We tend to agree with ORA's findings; however, it is our opinion that a liquefaction analysis should be performed to quantify the liquefaction potential. The most widely used method in this area is an empirical procedure, termed "Seed's Simplified Procedure," which is based on correlations between standard penetration resistance (Standard Penetration Test [SPT] N -value) and peak ground acceleration (PGA) as proposed by Seed and his colleagues (1971 and 1983) and updated by Youd et al. (2001). ► Section 10.3.1 of the ORA report provides spread footing foundation recommendations. We recommend that seismically -induced settlement (i.e., settlement resulting from liquefaction) be discussed in connection with spread footing foundations and the estimated liquefaction potential at the site. ► Section 10.8 of the ORA report discusses the slope stability analyses that they performed. Their analyses included pre- and post -development cases, analyzed with and without ground shaking considered. In our opinion, the ORA report should address the following slope stability scenarios: - The means by which groundwater levels would be lowered by 5 feet across the site (provide calculations demonstrating this is feasible). Weaker static strength values for the upper silty sand layer. Our experience suggests that the friction angle and cohesion used in slope stability modeling by ORA are unconservative. - Residual strength in the upper soil layer, which would result from liquefaction during/after a seismic event. - Slope failures within the upper layer and through the loose silty sand, rather than through the underlying stiff to hard cohesive soils. - Wedge-shaped slope failure along or near the interface of the upper and lower soil units. - Slope failure along more than one profile, specifically a profile through the sag pond, which appears to present the worst-case condition on the site. ► In the Tukwila Municipal Code Chapter 18.45.120, Areas of Potential Geologic Instability Designation, Rating and Buffers, Part C, it states "The Geotechnical Report shall analyze and make recommendations on the need for and width of any setbacks or buffers necessary" for Class 2 or higher areas. We recommend that ORA address appropriate buffer or setback distances from top and bottom of steep slopes, if necessary. 21-1-20689-001-L1 /wp/LKD 21-1-20689-001 Ms. Joanne Spencer City of Tukwila March 8, 2007 Page 4 CONCLUSION SHANNON FiWILSON. INC. In general, the geotechnical report that we reviewed is preliminary and incomplete at this time. Additional subsurface explorations and technical analyses are needed. We recommend that the permit applicant have the Geotechnical Engineer of Record respond to these comments and submit a final report and calculations, as appropriate. Comments made during the review process do not relieve the project applicant or designer from compliance with code requirements, conditions of approval, or permit requirements; nor is the designer relieved of responsibility for a complete design in accordance with the laws of the State of Washington. This peer review is a check for compliance with generally accepted professional geotechnical engineering principles and practices used by geotechnical engineering firms in this area. We appreciate the opportunity to be of service. If you have any questions or need clarification, we are available at (206) 632-8020. Sincerely, SHANNON & WILSON, INC. aureen M. McKenna, P.E. Senior Engineer LMM:MWP:TMG/lmm 21-1-20689-001-L1 /wp/LKD Martin W. Page, P.E., :L.E.G. Associate 21-1-20689-001 GEOTECHNICAL ENGINEERING. REPORT PROPOSED. RESIDENTIAL DEVELOPMIENT SOUTH 160TH ST AND 53R0 AVE S TUKWILA, WASHINGTON KINGCOUNTY PARCELS # 5379200005 AND #5379.200006 • PREPARED FOR: MR; JAWAID AMON BY: OTTO ROSENAU & ASSOCIATES, INC.: ORA JOB No. 06-373, REPORT No. 1 .OTTO.ROSENAU...& ASSOCIATES;; INC. . __ Geotechnical Engineering, Construction Inspection &'Materials Testing August 15, 2006 OTTO ROSENAU & ASSOCIATES, INC. Geotechnical Engineering, Construction Inspection & Materials Testing 6747 M. L. King Way South, Seattle, Washington 98118-3216 USA Tel: (206) 725-4600 • Toll Free: (888) OTTO-4-US • Fax: (206) 723-2221 WBE W2F5913684 • WABO Registered Agency • Website: www.ottorosenau.com Mr. Jawaid Amon 16424 53rd Place South Tukwila Washington 98168 Re: Geotechnical Engineering Report Proposed Tukwila Residential Development South 160`h Street and 53rd Avenue South Tukwila, Washington King County Parcel # 5379200005 and 5379200006 ORA Project Number: 06-373, Report 1 Dear Mr. Amon: We are pleased to provide this report for the referenced project. E3ased on our subsurface explorations and our analyses, it is our opinion that the proposed residential development can be satisfactorily completed in accordance with the City of Tukwila development standards for an environmentally critical area, such as that present at the site. It is our opinion that it is possible to develop the site, provided that it is completed in accordance with the recommendations presented in this report. The primary concern for development in environmentally sensitive areas such as the project site is to not increase the risk of future slope instability. The primary ways that the risk of future slope instability can be reduced or minimized is to incorporate the following measures into the development of the project site. Careful grading to minimize fills at the upland areas of the site to avoid increasing potential driving forces that could lead to slope instability. Overall, the project should be a net export or balance site. • Installation of subsurface drainage such as an interceptor trenches that will provide drainage in the areas where shallow groundwater was observed, such as along South 160th Street. The intercepted groundwater should be routed away from the site to avoid reintroduction in vulnerable downslope areas. • This site is not suitable for on-site infiltration of stormwater runoff from impermeable surfaces such as roadways, paved surfaces and roofs. As a result, large detention facilities will likely be required. All piping and detention facilities should be designed to reduce exfiltration into the adjacent soils. Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Client: Mr. Jawid Amon Job Name: Tukwila Property, South 160'" Street and 53'" Avenue South, Tukwila, WA Project No.: 06-373 Date: August 15, 2006 • Several of the proposed residential structures, especially in the western side of the development will likely require deep foundation support or significant overexcavations of unsuitable soils to mitigate the presence of loose, wet, sandy soils. • Re -grading of steep slope areas along 53rd Avenue South to provide flatter permanent slope inclinations. Detailed earthwork and foundation recommendations are presented in the attached report. If you have any questions, or if we may be of additional service, please contact us. EXPIRES IO Of t4.(2.64 1 Copies to: Addressee (8) Sincerely, Otto Rosenau & Associates, Inc. d& -7)--c Anthony G. Coyne, P.E. Geotechnical Engineer Otto Rosenau & Associates, Inc. Page 2 of 2 TABLE OF CONTENTS 1. INTRODUCTION 1 2. PROJECT DESCRIPTION 1 3. SCOPE OF SERVICES 1 4. SITE CHARACTERIZATION 2 5. SURFACE CONDITIONS 2 6. SUBSURFACE CONDITIONS 3 7. LABORATORY TESTING 4 8. REVIEW OF LITERATURE 4 9. DISCUSSION 5 10. CONCLUSIONS AND RECOMMENDATIONS 5 10.1 General 5 10.2 Seismic Considerations 6 10.3 Foundations 8 10.3.1 Shallow Foundations 8 10.3.2 Deep Foundations 9 10.4 Below -Grade Walls and Retaining Walls 10 10.5 Slabs -on -Grade 10 10.6 Earthwork 11 10.6.1 Site Clearing 11 10.6.2 Structural Fill — Material, Placement, and Compaction 11 10.7 Site Slopes 12 10.7.1 Permanent Slopes 12 10.7.2 Temporary Slopes 12 10.8 Slope Stability 13 10.9 Erosion and Sedimentation Control 15 10.10 Drainage 15 10.10.1 Construction Dewatering 15 10.10.2 Surface Drainage 15 10.10.3 Subsurface Drainage 15 10.11 Construction Observation and Testing 16 11. REPORT LIMITATIONS 16 APPENDIX Vicinity Map A-1 Site Pian A-2 Geologic Cross Section A -A' A-3 Boring Log A-4 Boring Log Notes A-15 Atterberg Limit Test Results A-18 TABLE OF CONTENTS Particle Size Distribution Report A-19 Direct Shear Test Results A-34 Typical Foundation Detail A-39 Notes A-44 GEOTECHNICAL ENGINEERING REPORT PROPOSED TUKWILA RESIDENTIAL DEVELOPMENT SOUTH 160TH STREET AND 53RD AVENUE SOUTH TUKWILA, WASHINGTON Prepared for Mr. Jawaid Amon by Otto Rosenau & Associates, Inc. August 15, 2006 1. INTRODUCTION This report presents the results of our geotechnical engineering services .for the proposed residential development in Tukwila, Washington. The location of the site is shown on the Vicinity Map on page A-1 of the appendix. 2. PROJECT DESCRIPTION Based on preliminary project information, we understand that the project involves developing two undeveloped Tots to create a gated community of about 13 homes of approximately 3,500 square feet in size. Two wetlands are to be removed and are to be mitigated by extending the existing wetland at the northwest corner of the site. 3. SCOPE OF SERVICES The scope of services included a reconnaissance of the site by the geologist, a review of geologic literature, and witnessing the drilling of five borings (B-1 and B-5) and installation of two ground water monitoring wells at borings B-1 and B-2. The approximate location of the explorations are shown on the Site Plan on page A-2 of the appendix. The geotechnical engineering services were performed by Otto Rosenau and Associates, Inc. (ORA) to provide the following information: • seismic design considerations including liquefaction potential, • allowable bearing capacity and depth of suitable foundation systems with estimated settlements, • lateral earth pressures and friction coefficients, • slope stability analysis, • influence of groundwater on the development, and • site preparation, earthwork and temporary cut slope recommendations. Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 2 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing 4. SITE CHARACTERIZATION We reviewed the "Geologic Map of The Des Moines 7.5' Quadrangle, King County, Washington", 2004 by Booth, Derek B. and Waldron, Howard H. The soils at the project site are predominantly mapped as Deposits of the Vashon Stade of Fraser Age glaciation. These deposits consist of recessional outwash (Qvr), till (Q,t), and recessional Iacustrine deposits (am). (Qvr) typically consist of stratified sand and gravel, moderately, well sorted to well sorted; typically deposited in outwash channels. (Q%,) consist of compact diamict containing sub -rounded to well-rounded clasts in massive, silt or sand rich matrix, which is glacially transported and deposited. (Qvri) consist of very fine grained sand, silt and clay deposited in small lakes during ice recession 5. SURFACE CONDITIONS The site is two parcels which were combined to create an irregular shaped site. The site is bounded on the south and southwest by South 160th Street, along the east side by 53rd Avenue South. The north boundary of the site consists of a Seattle Public Utilities water line easement with South 159th Street immediately to the north of it. The site grades slope downwards to the northeast from approximately Elevation 290 feet near the intersection of 51st Avenue South and South 160th Street to Elevation 196 feet at the northeast property corner the intersection of 53rd Avenue South and South 159th Street. The majority of the elevation change is located at the northeast section of the site (Elevation 196 feet to Elevation 236 feet). The proposed area to be developed is to be located in the eastern two-thirds of the site with access from South 160th Street at the southeast corner of the site. The western one-third of the site is to remain undeveloped. The site is located on a greater slope that extends upwards to the southwest and downwards towards the 1-5 / 1-405 interchange. There is a fairly level area at the southeast corner of the site near the intersection of South 160th Street and 53rd Avenue South. South 160th Street rises to the west and a concrete retaining wall is located along much of the South 160th Street right-of-way that borders the site. The site grades are quite steep in the far western end of the site that is to remain undeveloped. The Seattle Public Utilities water line easement along the north side of the site contains a delineated wetland and a drainage ditch that drains to the northeast under 53rd Avenue South. Steep slopes border the east side of the site along 53rd Avenue South. Portions of the slopes appear to have been built up as an embankment at the approximate location of the historic structures and driveways that used to be present on the site. There are several low-lying areas that have developed into wetlands in the central portion of the site. The site has three delineated wetlands as identified by Mead, Gilman and Associates in their survey dated January 6, 2006. The site is heavily vegetated with holly, ivy and deciduous trees, a combination of mostly maples up to 50 inches in diameter and alders of various sizes. There is evidence of past development on the site based on presence of fill embankments and linear features that appear to have Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 3 of 16 been driveways. The site has also been used, until recent times, as an uncontrolled dump site. The dumped materials include household waste, wood and metal construction debris, soil, rock, and concrete rubble. Based on our review of historical maps, there appeared to have been several structures (likely residential) present on the site with access from the southeast corner of the site. There is evidence of a past slope instability as evidenced by severely leaning trees on the steep slopes along 53rd Avenue South. The slopes in this area are to be flattened and reduced substantially in height as part of the site development. A prehistoric slide scarp was identified by Shannon & Wilson, Inc. in their map of the Tukwila Interchange revised May 1968. The scarp is located on the far west boundary of the lot and is intersected by South 160th Street. Shannon & Wilson's report to the City of Tukwila, November 23, 1992, describes this slide scarp and estimates that displacements of up to 30 to 40 feet have occurred along portions of the 3000 feet estimated length. They indicate that the scarp appears to trend to northwest above the project site and to the southeast towards Slade Way. The presence of several peat deposits in low-lying areas near the slide scarp in nearby off-site areas supports the assertion that the slide has not been activated in historic times. There have been numerous other slope failures identified in the area, both pre -recent and recent. One of the largest is a recent deep-seated slide that occurred just to the southwest of the site in 1960 during the construction of the 1-5 / 1-405 interchange. As a result of this slide, in the 1960's, a network of horizontal drains was installed to relieve artesian pressure within the hillside. 6. SUBSURFACE CONDITIONS We evaluated the subsurface soil and groundwater conditions by completing five borings (B-1 through B-5) at the site using a subcontracted, track -rig mounted, hollow -stem auger, and mud rotary drilling equipment between June 20 and 23, 2006. Only boring B-4 was completed using hollow -stem auger drilling equipment. Borings B-1 through B-3 and B-5 were completed using mud rotary drilling techniques. The following table summarizes the depths of borings completed for this project. BORING DEPTH BELOW EXISTING GRADE (feet) ELEVATION (feet) WELL INSTALLED (screen depths) B-1 101.5 153.5 Yes, screens from 15 to 20 feet B-2 81.5 123.5 Yes, screens from 18 to 23 feet B-3 66.5 158.5 No B-4 51.5 178.5 No B-5 51.5 193.5 No Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 4 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Please refer to the Site Plan on page A-2 of the appendix for the approximate location of the borings. The details and explanations of our explorations are presented on pages A-4 through A-17 of the appendix. Similar soil conditions were observed at each boring location with an upper zone of loose to dense sand with varying silt content ranging from 21 to 46 feet in thickness over stiff to hard sandy silt, silt and lean clay. We did not observe indications of a slide plane in any of our explorations as might be evidenced by slickensides or a highly disturbed zone. A typical profile of the subsurface geology encountered is presented in the figure titled "Geologic Cross Section A -A- on page A-3 of the appendix. We did not observe a well-developed soil horizon or organic soils at the lowest portion of Wetland 1. We observed dense, gray silty sand at a depth of about 12 inches below the existing site grade. We understand that this wetland area is to be eliminated as part of the proposed development. Groundwater was encountered during drilling at each boring location. A 2 -inch diameter PVC standpipe piezometer was installed at borings B-1 and B-2 in the upper sandy soils overlying the stiff to hard silts. Groundwater has been measured at B-1 and B-2 at depths of about 3 feet and 18 feet below the existing adjacent site grade. The groundwater levels at the site will likely vary with season and precipitation. We observed standing water in close proximity to the location of boring B-1. 7. LABORATORY TESTING We performed a wide range of laboratory tests on representative soil samples at the ORA soils laboratory. The tests performed include the following: • Moisture content determinations. Results are presented on the boring logs. • Atterberg Limit Determinations (ASTM D 4318). Results are presented on pages A-18 of the appendix. • Grain size analyses (ASTM D 422). Results are presented on pages A-19 through A-33 of the appendix. • Direct shear test results (ASTM D 3080). Results are presented on pages A-34 through A-38 of the appendix. Direct shear tests were performed by HWA Geosciences in Lynnwood, Washington. 8. REVIEW OF LITERATURE We reviewed several geotechnical reports that were completed in the vicinity of the project site. These included the following projects: • Hillcrest Residential Development located upslope and south of the project site. Cascade Geotechnical Inc. completed a geotechnical investigation and a series of subsequent responses to the City of Tukwila's review comments. Shannon & Wilson, Inc. provided geotechnical review services for the City of Tukwila. The correspondence that we reviewed is dated between 1992 and 1993. The location of the Hillcrest Residential Development is very close to the scarp of the Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 5 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Targe landslides that occurred in the 1960s during the construction of the 1-5 / 1-405 Interchange. The landslide was remediated partially by installing horizontal drains on WSDOT right-of-way. It appears that the horizontal drains have not been maintained by WSDOT and that several consultants have indicated that the factor of safety against slope failure at this site will continue to decrease as long as maintenance is not performed on the horizontal drains. • Five Rivers Development located downslope to the northeast of the project site. LSI Adapt, Inc. completed a geotechnical investigation and presented the results of their investigation in "Geotechnical Engineering Report, Five Rivers Preliminary Plat, 53rd Avenue S. and S. 159th Street, Tukwila, Washington" dated August 2001. LSI Adapt, Inc. prepared several subsequent engineering design supplements to address slope stability issues that were not initially addressed. Shannon & Wilson, Inc. provided geotechnical review services for the City of Tukwila on this project and concurred that LSI Adapt Inc.'s design approach satisfies the City of Tukwila's requirement for development in an environmentally -sensitive area. • 53rd Avenue South and South 160th Street Improvements project located along the south border of the site and extending to the west. Landau Associates, Inc. completed a geotechnical investigation for this project and presented their recommendations in "Geotechnical Study, 53rd Avenue South and South 160'h Street Improvements, Tukwila, Washington" dated March 5, 1991. We also reviewed the project plans prepared by the City of Tukwila Public Works. We were able to determine that the cast -in-place concrete retaining wall that is present along South 160th Street is a cantilevered retaining wall and is supported on conventional spread footings. 9. DISCUSSION The recommendations presented in this report are based on our understanding of the project as presented in the Project Description Section and on the assumption that the subsurface conditions are as assumed herein. Project conditions, regarding type and location of structures and foundation Toads can change, and subsurface conditions are not always similar to those encountered during the subsurface exploration. Therefore, if discrepancies are noticed, the geotechnical engineer must be contacted for review and for possible revision of the recommendations. 10.1 GENERAL The engineering recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical engineering practices in the area. The recommendations are based on our understanding of the geology of the area and on experience with similar projects. It is our opinion that it is possible to develop the site, provided that it is completed in accordance with the recommendations presented in this report. The primary concern for development in environmentally sensitive areas such as the project site is to not increase the risk of future slope instability. 10. CONCLUSIONS AND RECOMMENDATIONS Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 6 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing The primary ways that the risk of future slope instability can be reduced or minimized is to incorporate the following measures into the development of the project site. • Careful grading to minimize fills at the upland areas of the site to avoid increasing potential driving forces that could lead to slope instability. Overall, the project should be a net export or balance site. • Installation of subsurface drainage such as an interceptor trenches that will provide drainage in the areas where shallow groundwater was observed, such as along South 160th Street. The intercepted groundwater should be routed away from the site to avoid reintroduction in vulnerable downslope areas. • This site is not suitable for on-site infiltration of stormwater runoff from impermeable surfaces such as roadways, paved surfaces and roofs. As a result, Targe detention facilities will likely be required. All piping and detention facilities should be designed to reduce exfiltration into the adjacent soils. • Several of the proposed residential structures, especially in the western side of the development will likely require deep foundation support or significant overexcavations of unsuitable soils to mitigate the presence of loose, wet, sandy soils. • Re -grading of steep slope areas along 53rd Avenue South to provide flatter permanent slope inclinations. 10.2 SEISMIC CONSIDERATIONS The seismic design of structures in the City of Tukwila is governed by the requirements of the 2003 International Building Code (IBC). The IBC requires that the site be classified into a site class. Based on the results of the soil exploration completed at the project site, it is our opinion that the observed conditions most closely meet the described conditions of Site Class D (IBC Table 1615.1.1). Site specific criteria can be obtained from maps in the IBC (Figures 1615(1) and 1615(2)) for short period (SS) and 1 -second -period (S1) spectral accelerations. The values for SS and S1 are spectral response accelerations (SRA) for a maximum considered earthquake event with a 2,500 year return period or a 2% probability of exceedance (PE) in 50 years. Values for Ss and S1 are also available from the United States Geological Survey (USGS) National Seismic Hazard Mapping Project website. The values recommended for use in this report were obtained from the USGS website by inputting latitude and longitude for the project site (N 47.45943°, W 122.26734°). The 1996 data set from the USGS website was used for consistence with the relevant figures in the 2003 IBC. The following table presents recommended values from the 2003 IBC for seismic design: Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 7 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing 2003 International Building Code (IBC) Seismic Design Values (2% PE in 50 years) Mapped max. earthquake SRA at short periods, Ss, % g 135.1 Mapped max. earthquake SRA at 1 -second period, S1, % g 46.5 Peak Ground Acceleration, % g 61.4 Site Class Definition (Table 1615.1.1) D Site Coefficient Fa (Table1615.1.2(1)) 1.0 Site Coefficient F„(Table1615.1.2(2)) 1.5 Max. considered earthquake SRA for short periods, SMS 135.1 Max. considered earthquake SRA for 1 -second periods, SM1 69.8 Design SRA at short periods, SDS 90.1 Design SRA at 1 -second period, SD1 46.5 Liquefaction may be defined as the sudden Toss of strength of soil as the soil is subjected to a rapid cyclic loading, such as during an earthquake. The mechanism that allows this to occur is that excess pore water pressures are generated between the soil particles. This excess pore water pressure reduces the frictional contact between the soil particles and reduces the shear strength of the soil. If the earthquake is of Targe magnitude and duration, the soil can begin to behave more like a liquid than solid and "liquefy". In order for liquefaction to occur, several conditions must typically be present. These include the following: • Saturated soil. • Fine to medium sand matrix containing less than about 10 percent fines (soil that can pass a No. 200 sieve. • Very loose to medium dense soil conditions. This is usually defined as soils that have N - values of 15 or less. Based on the results of our explorations and our observation of the soil and groundwater conditions at the site, it is our opinion that the potential for liquefaction at the site is medium to high along the western portions of the site to be developed and low to medium along the eastern portions of the site to be developed. The most recent, significant, seismic event was the Nisqually earthquake which occurred on February 28, 2001 with a Richter magnitude of 6.8 and a peak ground accelerations in the Seattle area approaching 20% g. Little to no slope instability was reported in the Seattle area as a result of the earthquake. Significant structural damage did occur to buildings where the existing subsurface conditions tended to amplify the ground motion, such as in the area south of downtown Seattle, where Targe areas of hydraulically -placed fill are present over former tidal mudflats. Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 8 or 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing 10.3 FOUNDATIONS Several of the proposed residential structures, especially in the western side of the development will likely require deep foundation support or deep overexcavations of unsuitable soils to mitigate the presence of loose, wet sandy soils. It is anticipated that the residences to be built along the eastern side of the development will likely be able to be supported on conventional spread footings. 10.3.1 Shallow Foundations: The residential structures to be located in the eastern portion of the development will likely be able to be supported on shallow foundation elements that bear on re - compacted, existing sandy subgrade. We recommend that an overexcavation be completed at the location of all future foundation elements to a depth at least 2 feet below the design bottom of footing elevation. The overexcavation should extend laterally at least 2 feet on all sides of the future foundation elements. Please refer to the Typical Foundation Detail on page A-39 of the appendix for a summary of these recommendations. We recommend that the following allowable bearing capacities be used for the design of conventional spread footings: Foundation bearing on 2 -foot thick zone of structural fill that extends to the native, re -compacted sandy soil: 2,000 psf The allowable bearing capacities may be increased by one-third for wired and seismic loads. If the recommendations in this report are followed, we estimate that maximum post -construction settlements will be Tess than three-quarters (3/4) of an inch and differential settlements will be less than one-half (1/2) of an inch between comparably loaded column footings or along a 25 -foot long section of continuous wall footing. We recommend that the minimum width of continuous footings be 1.5 feet and that the minimum size of column footings be 2 -foot by 2 -foot. All foundation elements shall be embedded at least 18 inches below the lowest adjacent finished grade for frost protection and to meet the minimum code requirements as presented in Section 1805 — Footings and Foundations of the 2003 International Building Code (IBC). Passive resistance should be evaluated using an equivalent fluid pressure of 250 pounds per cubic foot (pcf) where grade beams are cast on structural fill or dense native soils and backfilled on both sides with structural fill compacted to at least 95 percent of maximum dry density (MDD). This value of passive pressure includes a factor of safety of 1.5. An ultimate coefficient of friction between footings and bearing soils of 0.35 may be used to resist lateral foundation Toads. If passive earth pressures are used in conjunction with base friction to resist Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 9of16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing lateral Toads, reduce the ultimate coefficient of friction to 0.30. A factor of safety of 1.2 should be applied to these values. 10.3.2 Deep Foundations: The residential structures to be located in the western portion of the development will likely need to be supported on deep foundation elements. 3-, 4-, or 6 -inch diameter steel pipe piles driven to refusal would be suitable for use to provide downward axial support for the future residences. Small -diameter steel pipe piles should not be relied upon to provide uplift or lateral resistance. The pipe piles should consist of Schedule 40, Grade A53 steel pipe. The piles should be driven by an experienced contractor, using a hydraulic hammer weighing between 850 and 3,000 pounds depending on the pile size to be installed. ORA should be contacted once a pile driving contractor is selected to provide appropriate driving refusal criteria for the equipment being used. In general, the pipe piles must be driven through the upper loose to medium dense sandy layers and shall be embedded at least 5 feet into the stiff to hard clay layers, or the depth required to achieve refusal, whichever is greater. Pipe piles driven to refusal as described will have the following allowable downward pile capacities: Pile Diameter (inches) Allowable Downward Pile Capacity (tons) 3 6 4 10 6 15 Pile Toad testing will be required for this project to verify that the design loads are appropriate for the soil conditions at the site. A minimum of 5% of the total number of piles installed should be load tested for this project. The pile Toad tests should be monitored by an ORA representative. If the pile Toad test program indicates that higher loads are achievable on the project than presented above, ORA can provide revised recommendations for design pile capacities with an appropriate factor of safety. If the recommendations in this report are followed, we estimate that maximum post -construction settlements will be less than three-quarters (3/4) of an inch and differential settlements will be less than one-half (1/2) of an inch over a 50 -foot length of continuous grade beam or pile cap. Grade beams, pile caps, and any retaining walls should be reinforced to reduce the potential for distress caused by differential foundation movements. A qualified engineer should determine the size, quantity, and location of reinforcement. Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 10 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing 10.4 BELOW -GRADE WALLS AND RETAINING WALLS Lateral earth pressures for design of below—grade walls, retaining walls, ;and foundation elements with level backfill and with no hydrostatic pressures or surcharge Toads, may be calculated using the following equivalent fluid pressures: Active (unrestrained and drained conditions): Compacted granular soils 36 psf/fl. Active (restrained and drained conditions): Compacted granular soils 57 psf/ft. Passive: Continuous footings Column footings 250 psf/ft. 250 psf/ft. The geotechnical engineer should be contacted to determine appropriate lateral earth pressures for situations not described above. Seismic earth pressures were estimated using the Mononobe-Okabe pseudo -static method. We recommend that seismic earth pressures be estimated using a rectangular pressure distribution equal to 10H, where H is the height of the retained soil behind the wall. A total soil unit -weight of 125 pounds per cubic foot should be used in design of any permanent below - grade wall or retaining structures. 10.5 SLABS -ON -GRADE Based on our understanding of the project construction, we anticipate that the only slab -on -grade will be in the garage and we expect that only small amounts of fill will be required to raise the grades for floor slab support. Slabs -on grade should be at least 4 inches in thickness. The slab -on -grade should be supported on a minimum 4 -inch -thick, free -draining, gravel base as described in the Structural Fill section of this report. A vapor retarder such as 6 -mil polyethylene sheeting shall be included beneath the slab to minimize transmission of moisture through the concrete floor. A minimum, two-inch thick layer of clean sand with less than 3 percent fines may be placed on top of the polyethylene sheeting to protect the sheeting and to enhance the curing of the concrete slabs. The sand must not be saturated at the time of concrete placement to provide a drainage path for bleed water from the curing concrete. A more robust vapor barrier system may be required for the residences to be located in the western portion of the development where ground water levels are significantly higher. Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 11 of 16 Otto Rosenau II Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing 10.6 EARTHWORK The recommendations presented in this report are predicated on fulfillment of the following earthwork recommendations. 10.6.1 Site Clearing: Any existing vegetation, loose soil, and any other deleterious materials including asphalt pavements and old foundation elements household shall be removed from the future building area prior to construction. After site clearing and stripping, the exposed surfaces should be graded to allow good surface drainage during construction. The near -surface soils at the site are moisture -sensitive and easily disturbed during periods of wet weather. A gravel or quarry spall work surface may be built to protect the underlying native soils and to reduce the amount of soil disturbance during periods of wet weather. 10.6.2 Structural Fill: Material, Placement and Compaction: In general, the native soils on site that consist of sand with silt (SP -SM) or silty sand (SM) should only be used as structural fill during drier periods, provided that the soil is moisture -conditioned to within three (3) percent of optimum moisture. All fill and backfill materials should be placed in relatively horizontal loose lifts, not exceeding 10 inches in thickness, and compacted to at least 95 percent of the maximum dry density (MDD) as determined by the modified Proctor test (ASTM D1557). If manually -operated equipment such as a jumping jack compactor is used, the thickness of each loose lift should be no greater than 6 inches. Light vibratory plate compactors are not suitable for the compaction of structural fill. Soils consisting of clay, silt, peat, or containing deleterious matter are generally not suitable for use as structural fill. Structural fill material should be approved by ORA prior to use. The following table summarizes our recommendations and compaction requirements in reference to the 2006 edition of Washington State Department of Transportation's (WSDOT) Standard Specifications for Road, Bridge, and Municipal Construction for various types of aggregates. Intended Use Specification Compaction Requirements Structural fill for overexcavation backfill below foundation elements 2- to 4 -inch quarry spalls, or washed crushed rock with a typical particle size between 1.25 and 2 inches and less than 5 percent fines Quarry spalls or clean crushed rock must be placed in lifts no greater than 12 inches in thickness, with each lift thoroughly compacted with a vibratory roller, or hoepack mounted on an excavator. Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 12 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engneering, Construction Inspection & Materials Testing Intended Use Specification Compaction Requirements Structural fill below pavements or sidewalks Suitable native soil, Gravel Borrow (WSDOT 9-03.14(1), Select Borrow (WSDOT 9-03.14(2), Crushed Surfacing Base Course (WSDOT 9- 03.9(3) Fill placed at depths greater than 2 feet below finish subgrade elevation must be compacted to 90 percent of MDD. Fill placed at depths within 2 feet of finish subgrade elevation must be compacted to 95 percent of MDD. Free -draining wall drainage material behind below -grade walls and retaining walls Gravel Backfill for Walls (WSDOT 9- 03.12(2), Gravel Backfill for Drains (WSDOT 9-03.12(4) Fill placed within 5 feet of below - grade walls or retaining walls shall be compacted with manually -operated compaction equipment. Fill placed at depths greater than 2 feet below finish subgrade elevation compacted to 90 percent of MDD. Fill placed at depths within 2 feet of finish subgrade elevation must be compacted to 95 percent of MDD, if the area will be supporting pavements or roadway. Capillary break material below slabs Pea gravel with a maximum particle size of about 3/8" and Tess than 3 percent fines. Washed, crushed rock with a maximum particle size of about 5/8" Washed, crushed rock shall be mechanically compacted prior to placing concrete. Structural fill to be compacted to 95 percent of MDD should be moisture -conditioned to within three (3) percent of optimum moisture. Structural fill to be compacted to 90 percent of MDD should be moisture - conditioned to within six (6) percent of optimum moisture content. Placement of frozen soils or placement of soils on frozen ground should not be attempted. 10.7 SITE SLOPES 10.7.1 Permanent Slopes: We recommend that permanent slopes be inclined no steeper than 3H:1V (horizontal to vertical). All embankment fills should be placed as structural fill in accordance with WSDOT specifications. 10.7.2 Temporary Slopes: We anticipate that temporary cut slopes will be used at portions of the site to complete roadway and utility trench excavations. We recommend that the inclination of the Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 13 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing temporary cut slopes be no greater than 1.5H:1V in the upper loose, sandy soils. Flatter slope inclinations will be required if groundwater seepage is encountered in excavations. All temporary cut slopes and excavations must comply with the provisions of Washington Administrative Code (WAC) Chapter 296-155, Part N, "Excavation, Trenching and Shoring." The contractor performing the work has the primary responsibility for protection of workers and adjacent improvements. However, we recommend that the contractor submit a work plan and excavation support plan for our review prior to beginning work on the site. 10.8 SLOPE STABILITY We performed a visual reconnaissance of the slopes at the site to evaluate the current slope stability conditions at the site. We observed indications of recent slope instability at the steep slope areas along 53rd Avenue South as evidenced by severely leaning trees. However, many of the trees are covered with English ivy, which can adversely affect the health of the trees. Areas with near -surface wet soil conditions are present along South 160th Street, which is possibly similar to a sag pond feature that is common in areas where past slope instability has occurred. This area should be drained using permanent subsurface interceptor trenches to help draw down the water level and reduce the weight of the soil and driving forces that could lead to slope instability in this area. ORA performed a computer-based slope stability analysis using the XSTAE3L Version 5.206. XSTABL uses the Bishop Method of Slices to estimate factors of safety and forces. We used the information from the field -generated cross-sections A -A' indicated on the Site Plan on page A-2 of the appendix and from the subsurface explorations as a basis for input into the slope stability analysis. We evaluated the following two cases for the pre -developed and developed conditions at the site. The pre -developed condition assumes current site grades and no subsurface drainage. The post -developed condition assumes the current site grades are unchanged but that subsurface drainage is provided to reduce the groundwater elevation to at least 5 feet below the existing site grade. Two loading conditions were modeled: 1. Static Loading Conditions — No earthquake forces applied, existing sii:e conditions. 2. Seismic Loading Conditions — 0.2 g peak ground acceleration, modeled as a horizontal coefficient, ah of 0.1 in the pseudo -static analysis. The existing slope was modeled assuming the presence of two soil layers — the upper loose to medium dense sand layer and the stiff to hard silt and lean clay layer. The following soil parameters were used and are based on direct shear test results completed for this project: Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 14 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing Cohesion (psf) 250 300 A graphical presentation of the results of our slope stability analysis are presented on pages A-40 through A-43 of the appendix. A summary of the results under the various loading conditions is presented in the following table: Site Condition Soil Unit Description Assumed Unit Weight, 'y, (pcf) Angle of Internal Friction, 4), (degrees) Upper Sandy Soil Unit (SP -SM and SM) 105 pcf dry 33 115 pcf saturated Lower Silt and Clay Unit (ML and CL) 116 pcf dry 32 120 pcf saturated Cohesion (psf) 250 300 A graphical presentation of the results of our slope stability analysis are presented on pages A-40 through A-43 of the appendix. A summary of the results under the various loading conditions is presented in the following table: Site Condition Loading Condition Estimated Minimum Factor of Safety Recommended Minimum Factor of Safety Pre -development Case 1 - Static 2.0 1.5 Pre -development Case 2 — Seismic 0.2 g 1.3 1.1 Post -development Case 1 - Static 2.1 1.5 Post -development Case 2 — Seismic 0.2 g 1.4 1.1 A factor of safety of 1 indicates that the forces that cause instability are in equilibrium with the forces that are resisting instability. A factor of safety of Tess than 1 indicates that the forces that cause instability are greater than the forces resisting instability and that the slope will fail. Conversely, factors of safety greater than 1 indicates that the forces resisting instability are greater than those causing instability and that the slope is stable. Based on the results of the slope stability analyses, we anticipate that the site is stable under static and seismic loading conditions (peak ground acceleration = 0.2g). The primary failure method anticipated by the slope stability analysis is a deep-seated failure with an initiation point at approximately the location of the assumed, ancient slide scarp on the uphill side of South 160th Street. It can be expected that seismic events with larger peak ground accelerations, and longer recurrence intervals, will result in a lower estimated factor of safety for slopes at the site. In order to reduce the risk of slope instability after construction, we recommend the following practices: • All roof drains, footing drains, and other drains should be gathered and tightlined to a discharge location approved by City of Tukwila. • No on-site infiltration of stormwater runoff should be used. Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 15 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineering, Construction Inspection & Materials Testing • Any accumulations of yard waste and biodegradable construction waste (cut branches, lawn clippings, and lumber) that are present should be removed from the slope face and adjacent areas. • Yard waste should not be placed on any of the existing slopes. • Vegetative cover should be continuously maintained on overall steep slope areas to reduce erosion potential and to stabilize surficial soils. 10.9 EROSION AND SEDIMENTATION CONTROL The migration of sediments from the site must be installed and controlled in accordance with City of Tukwila requirements. We recommend that the following minimum erosion control measures be employed at the site: • Provide silt fencing around the construction area to delineate the construction limits. No construction or soil disturbance should take place outside of the construction limits. • Stockpiled soil at the site should be kept to a minimum. Any stockpiled soils should be covered with carefully secured plastic sheeting. Additional erosion control measures may be required as construction progresses. 10.10 DRAINAGE 10.10.1 Construction Dewatering: Ground water seepage will likely be encountered during construction. However, we anticipate that dewatering could be satisfactorily completed by routing water through ditches to a low spot or sump in the excavation. Water collected M the excavation should be removed as soon as possible and should be discharged to a location approved by the City of Tukwila and in accordance with City of Tukwila requirements. 10.10.2 Surface Drainage: Good surface drainage is an integral part of the performance of earth - supported structures such as foundations, retaining walls, and pavements. Therefore, construction grades and final site grades should be designed to prevent water from entering the foundations or gravel drains behind any retaining walls, or from ponding on or next to pavements. Where pavement does not immediately abut structures, the ground surface should be sloped with an outfall of at least three (3) percent for a minimum distance of five (5) feet from exterior footings. These slopes should be capped with relatively impervious soils to prevent infiltration of water into the foundation soils. Runoff water should be collected from all impervious surfaces on the project and should be routed away from steep slope area on the west side of the site to a discharge location approved by the City of Tukwila. We strongly recommend that no on-site infiltration of runoff water be performed to minimize the flow of additional groundwater and to help minimize the risk of future slope instability. 10.10.3 Subsurface Drainage: We recommend that subsurface drainage be provided around each structure and that subsurface interceptor trenches be built at the site to draw down the high Tukwila Property ORA Project No.: 06-373 August 15, 2006 Page 16 of 16 Otto Rosenau & Associates, Incorporated Geotechnical Engineerinc, Construction Inspection & Materials Testing groundwater levels that are present at the site. The foundation drains for the residential structures should be built in accordance with the Typical Foundation Detail shown on page A-39 of the appendix. The foundation drains should be sloped to drain to a suitable discharge point. Roof downspout drains and footing drains must be kept separate. Below -slab drainage may need to be considered if high groundwater levels will appear to be problematic. We recommend that interceptor drains be built in upland areas of the site downslope of the existing cast -in-place concrete retaining wall along South 160th Street, and other areas where it is desirable to draw down the high groundwater level. The interceptor drains should consist of a gravel -filled trench with a perforated, rigid, PVC pipe. The gravel -filled drain should be fully -surrounded with a non -woven geotextile fabric, such as Mirafi, 140N or equivalent. Permanent interceptor drains should be two to three feet in width. 10.11 CONSTRUCTION OBSERVATION AND TESTING The recommendations presented in this report rely on adequate observation and testing of construction materials and procedures by the geotechnical engineer or his qualified representative. At a minimum, the testing program should include: • Observation and review of site preparation, structural fill placement, drainage installation, pile driving and pile load testing to evaluate whether actual conditions are consistent with those encountered during exploration and used for design. 11. REPORT LIMITATIONS The recommendations presented in this report are for the exclusive use of Mr. Jawaid Amon and other members of the design team for the proposed residential development at South 160th Street and 53rd Avenue South in Tukwila, Washington (King County Parcels # 5379200005 and 5379200006). The recommendations are based on the readily -available geologic literature and five borings completed on June 2006. The recommendations of this report are not transferable to any other site. If there are any revisions to the plans or if deviations from the subsurface conditions noted in this report are encountered during construction, Otto Rosenau & Associates, Inc. (ORA) should be notified immediately to determine whether changes to the design recommendations are required. oOo X 0 z W a a Q Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: July 18, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-1 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 E_ T 4) Na C >. 0) y U C l0 ` 3 'C CO O N C 7C- 0) Q 0) y f0 E y X N Q o as 0. Q m iV 0 CO Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. Scale: 1" = 40 feet 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 GEOLOGIC CROSS SECTION A -A' Project Name: Tukwila Property Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: July 17, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-3 6 cis 0) ,d c .c 0 ,./ Ar Loose to med. dense v sands and med. stiff silts C 0 03 # i I''__/�//I�r� �At. 0 Stiff to Hard and Lean Silt I���.����i���.������������� co Clay ���/������������������ Loose to med. dense Stiff to Hard Silt � ��ily///�� sands and med. stiff silts '�I_ and Lean Clay----���i���/���ii......__ -- A.��i/////dr j' Stiff to Hard Silt and Lean Clay Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. Scale: 1" = 40 feet 280 270 260 250 240 230 220 210 200 190 180 170 160 150 140 GEOLOGIC CROSS SECTION A -A' Project Name: Tukwila Property Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: July 17, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-3 '---,� e0 \ \ _ 290 ,=- X30 . 1 . - i -- ...'............................. \ : 7 IV '''. \ .. \ • S \ \ \ `3 `1 0 B-5 \ , gt 260 � . . \ \ ..\ _- N \ \ 1 'WETLAND 21- `1 \K -'- (WETLAND 11 Curb line �— Property line -"\---- -- \=---\ o ��o. B-4 LEGEND B-1 Boring completed by ORA 2• 0 1\ � \'I \ \N _. NW 190 0. A B-1 B-2 \• r-\ \ \C (WETLAND at I Note: The location of all features shown is approximate. Reference: Drawing titled "BOUNDARY & TOPOGRAPHIC SURVEY" prepared by Mead Gilman and Associates for Mr. Joe Amon dated 1/3/2006. Scale: 1" = 70 feet NA % N O \ B-3 • SITE PLAN Project Name: Tukwila Property Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: July 17, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-2 OTTO ROSENAU & ASSOCIATES, INC. �.. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/20/06 COMPLETED 6/20/06 GROUND ELEVATION 255 ft HOLE SIZE 6 -Inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING — BORING NUMBER B-1 PAGE 1 OF 3 PROJECT NUMBER 06-373 LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING -- NOTES 140 -pound automatic hammer, SPT sampler, 30 -Inch drop 24hrs AFTER DRILLING 18.0 ft / Elev 237.0 ft a ° w iii wca oD Wv a O ....< o 2z w too -- a N x TESTS MATERIAL DESCRIPTION 10 5-6-6 (12) 4-2-2 (4) 5-7-6 (13) 15 20 SS 5 44 4-8-13 (21) SS56 2-3-5 6 (8) 25 SS 56 8-11=15 7 (26) 30 SS 8 100 7-12-18 (30) 35 MC=15% MC=19% Fines=26% , GS MC=13% MC=18% MC=22% MC=32% MC=27% MC=32% LL=45 PL=26 Fines=93% , GS, HYD, AL SP - SM SM SM SM SM SM ML ML • •4.5 Medium dense, fine to medium, gray -brown SAND with SILT with some oxidation Very loose, gray Silty SAND with Gravel Medium dense, gray Silty SAND with gravel In tip of sampler Loose, gray Silty SAND with gravel In tip of sampler Medium dense, brown, Silty SAND with a 1 inch layer of oxidized sand at approximately 16 feet 3t 250.5 '•20.5 Loose, brown, interbedded Silty SAND and medium stiff SILT, lowest 2 234.3 \Inches gray SILT Very stiff, dark gray SILT Very stiff, dark gray SILT A-4 (Continued Next Page) 6 t9 Q. t9 z z a 0 D. D. O a. 2_5 OTTO ROSENAU & ASSOCIATES, INC. t 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawald Amon PROJECT NUMBER 06-373 w 35 RECOVERY tow m0> OZ TESTS rn 0 = C7 a0 0 BORING NUMBER B-1 PAGE 2 OF 3 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington MATERIAL DESCRIPTION 40 ST 9 SS 10 100 100 8-15-19 (34) 45 SS 11 100 9-16-21 (37) 50 X SS 12 100 7-11-14 (25) 55 VI S3 13 100 7-10-14 (24) 60 ST 14 SS 15 100 100 9-17-18 (35) 65 X SS 16 100 12-17-21 (38) 70 Xss 17 17 100 10-23-28 (51) X SS 18 100 12-26-35 (61) 75 MC=27% DD=93pcf ,DS MC=25% MC=27% MC=28% MC=28% MC=34% DD=87pcf ,DS MC=30% MC=32% Fines=99% , GS MC=33% MC=28% ML ML ML ML ML ML ML ML ML ML Very stiff, dark gray SILT Hard, dark gray SILT Hard, gray SILT Very stiff, gray SILT Very stiff, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT with 1 -Inch thick seam of fine SAND at 71 feet A-5 (Continued Next Page) OTTO ROSENAU & ASSOCIATES, INC. o- 6747 M.L. King Way South BORING NUMBER B-1 Seattle, WA 98118 PAGE 3 OF 3 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawatd Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila. Washington a. F 75 SAMPLE TYPE NUMBER RECOVERY % BLOW COUNTS (N VALUE) TESTS vi ai GRAPHIC LOG MATERIAL DESCRIPTION - -X S 19 00 16-26-31 MC=30% ML Hard, gray SILT with medium SAND in tip 80 SS 0 50/6" ML No - -?� 1 20 i recovery 85 - -XSS 21 100 16-26-38 (64) MC=26% ML Hard, gray SILT with distinct 1/4 -Inch lamination dark gray to black SILT - - 90 at 86.25 feet. Inclined bedding orientation. Massive silt present above and below sand lamination. - - SS 22 100 15-27-43 (70) MC=26% ML Hard, gray SILT 95 - -v n SS 23 100 20-30-39 69 MC=27% ML Hard, gray SILT - i 100 - xi 24 101 23-50/6" MC=30% ML • • 101.5 Hard, dark gray SILT 153.5 Bottom of hole at 101.5 feet. A,R 0. ga OTTO ROSENAU &ASSOCIATES, INC. BORING NUMBER B-2 6747 M.L. King Way South t _ Seattle, WA 98118 PAGE 1 OF 3 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawald Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/21/06 COMPLETED 6/21/06 GROUND ELEVATION 205 ft HOLE SIZE 6 -Inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING — LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING -- NOTES 140 -pound automatic hammer, SPT sampler, 30 -Inch drop AFTER DRILLING — 1 w$ 0 0 I -w w wm dD z N RECOVERY o TESTS U vi D �O MATERIAL DESCRIPTION 10 SS 2-3-4 (7) 100 20 25 SS 6 100 100 67 4-11-13 (24) 3-4-6 (10) SS56 5-7-8 7 (15) 30 35 SS 8 100 3-8-9 (17) MC=21% Fines=44% , GS MC=12% MC=20% DD=86pcf ,DS MC=16% FInes=20% , GS MC=27% DD=93pcf , DS MC=29% MC=30% MC=29% SM SM SP- SM :- • SP - SM Gravelly drilling from 1.5 feet to 5 feet Loose, Tight brown Silty fine SAND -11.0 ,Medium dense. Tight brown Silty fine SAND • 18.0 Medium dense, light brown Silty fine SAND with Silt Medium dense, light brown fine SAND with Silt occasional thin oxidized layers 194.0 S ML ML ML Loose to medium dense, Silty fine SAND • 23.0 ,Loose to medium dense, Silty fine SAND Stiff, gray Sandy SILT Very stiff, gray SILT Very stiff, gray SILT 187.0 182.0 A-7 (Continued Next Page) OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Anion PROJECT NUMBER 06-373 a r:3v 35 w a �w w 2z RECOVERY % cog mo— oz TESTS vi ui D SO gO O BORING NUMBER B-2 PAGE 2 OF 3 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington MATERIAL DESCRIPTION 40 45 ST 9 100 X 50 55 SS 10 67 5-12-12 (24) x SS 11 100 7-13-17 (30) k SS 12 78 10-18-23 (41) 60 65 X SS 13 100 9-16-22 (38) X SS 14 100 15-25-23 (48) 70 X SS 15 100 16-26-26 (52) X SS 16 100 15-31-52 (83) 75 MC=27% DD=97pcf ,DS MC=25% MC=30% . MC=29% LL=33 PL=26 Flnes=96% , GS, HYD, AL MC=30% MC=29% MC=31% MC=24% ML ML ML ML ML ML ML Very stiff, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT Hard, gray SILT with distinct 1/4 -Inch lamination black SILT at 71 feet. Inclined bedding orientation. A-8 • (Continued Next Page) OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawald Amon PROJECT NUMBER 06-373 0- w - C) 0 75 RECOVERY BORING NUMBER B-2 PAGE 3 OF 3 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington (Or11 mO OZ TESTS (U U) MATERIAL DESCRIPTION 80 SS 17 100 17-42-47 (89) SS 18 100 22-34-40 (74) 0 a. a 5 MC=24% MC=22% ML ML Hard, gray SILT 81.5 Hard, gray SILT Bottom of hole at 81.5 feet. 123.5 A-9 OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NUMBER 06-373 BORING NUMBER B-3 PAGE 1 OF 2 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/22/06 COMPLETED 6/22/06 GROUND ELEVATION 225 ft HOLE SIZE 6 -Inches GROUND WATER LEVELS: AT TIME OF DRILLING — LOGGED BY Craig Bechtold L.G. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING — NOTES 140 -pound automatic hammer, SPT sampler, 30 -Inch drop DRILLING CONTRACTOR Gregory Drilling DRILLING METHOD Mud Rotary a w 0 0 5 w a �� w w -12 Qz co RECOVERY �w -J mOZ SS 1 100 3-4-8 (12) 10 S 89 6-9-9 (18) SS 3 33 8-8-9 (17) SS 4 0 10-13-17 (30) x SS 5 22 12-9-8 (17) SS 6 33 6-5-7 (12) 20 SS _IX7 25 100 8-21-12 (33) • 30 SS 8 44 7-6-18 (24) SS 9 0 17-15-17 (32) tg • 35 TESTS 0 V a0 0 AFTER DRILLING — MATERIAL DESCRIPTION MC=16% MC=33% MC=14% MC=15% MC=21% Fines=15% , GS MC=14% MC=20% 6.5 9.5 29.0 Medium dense, brown, flno to medium SAND with SILT, some oxidation evident Medium dense, Tight brown, fine to medium SAND with Silt Medium dense, Tight brown, well -graded Silty SAND No recovery with trace fine sand in sampler Medium dense, Tight brown„ fine to medium, SAND with Silt and gravel Medium dense, Tight brown, fine to medium SAND with Silt and gravel Dense, Tight brown, fine to medium SAND with Slit and occasional gravel with some oxidation evident Medium dense, light brown, fine to medium SAND with Silt and occasional gravel with some oxidation evident No recovery A-10 (Continued Next Page) 218.5 215.5 196.0 D a. 0 z a res w ®® OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NUMBER 06-373 BORING NUMBER B-3 PAGE 2 OF 2 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington a. w� 0 35 w �w W C° CL2 N RECOVERY (0 tri OZ; m0Z TESTS MATERIAL DESCRIPTION 40 SS - 10 100 11-10-10 (20) 45 SS 11 56 14-14-23 (37) 50 X SS 12 0 24-18-21 (39) 55 X SS 13 56 15-21-23 (44) 60 x SS 14 100 13-24-23 (47) 65 ,x SS 15 100 15-28-25 (53) SS 16 100 14-26-58 (84) MC=28% MC=26% MC=22% LL=39 PL=22 Fines=88% , GS, HYD, AL MC=31% MC=29% MC=30% SM ML SM Medium dense, light brown, fine to medium, Silty flne to medium SAND with interbedded Sandy SILT 38.0 44.0 Dense, light brown, Silty fine SAND CL CL CL CL / CL% No recovery with trace day in sampler Hard, gray lean CLAY Hard, gray lean CLAY Hard, gray lean CLAY 66.5 Hard, gray lean CLAY Bottom of hole at 66.5 feet. 187.0 181.0 158.5 A-11` OTTO ROSENAU & ASSOCIATES, INC. �.-_. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Amon PROJECT NUMBER 06-373 BORING NUMBER B-4 PAGE 1 OF 2 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/19/06 COMPLETED 6/19/06 GROUND ELEVATION 230 ft HOLE SIZE 8 -Inches GROUND WATER LEVELS: Q AT TIME OF DRILLING 11.0 ft / Elev 219.0 ft LOGGED BY Anthony Coyne P.E. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING -- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop AFTER DRILLING — DRILLING CONTRACTOR Gregory Drilling DRILLING METHOD Hollow Stem Auger Q.. ul " O 0 RECOVERY row OzQ m0z TESTS 0 vi _O _ (7 <0 n J U' MATERIAL DESCRIPTION 5 10 X X SS 1 89 6-5-6 (11) SS 2 100 4-4-4 (8) SS 3 100 3-5-6 (11) 15 X SS 4 100 3-3-6 (9) SS 5 89 4-7-7 (14) o- 0 20 - -X a. $ 25 SS 6 100 4-7-11 (18) S S 7 67 6-7-10 (17) SS 8 56 5-12-18 (30) MC=15% MC=13% Fines=26% , GS MC=16% MC=15% MC=25% Fines=13% , GS MC=30% MC=24% MC=26% SM SM SM SM SM SM SM SM SM SM • • • • • • • • • • • • • • • • • • • • • • • ..• :. ,•. Medium dense, gray, Silty fine to medium SAND with occasional debris and organics (charcoal and root hairs) (fill) Loose, fine to medium, gray Silty SAND (fill) Medium dense, gray Silty SAND with occasional fine gravel (fill), oxidation present. 11.0 v7 Medium dense, gray, Silty Sand with occasional fine gravel (fill), oxidation present. 219.0 Loose, gray, Silty fine SAND Medium dense, Tight brown, Silty fine SAND Medium dense, gray Silty fine SAND Medium dense, gray, Silty fine SAND Medium dense, light brown, Silty fine SAND, with some oxidation A-12 (Continued Next Page) OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawald Amon PROJECT NUMBER 06-373 FF= w 0 35 40 X RECOVERY TESTS ui U ui U a c3 BORING NUMBER B-4 PAGE 2 OF 2 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington MATERIAL DESCRIPTION SS 9 33 2-8-11 (19) 45 X SS 10 33 8-3-3 (6) 50 X SS 11 67 3-5-6 (11) SS 12 100 5-7-10 (17) MC=26% Fines=49% , GS MC=23% MC=33% MC=29% SM SM SM . ,•. ML ML Medium dense, light brown, Silty fine SAND Loose, bluish -gray, Silty fine SAND 46.3 Medium dense, bluish -gray, Silty SAND Stiff, blulsh-gray, Sandy SILT 51.5 Very stiff, bluish -gray, Sandy SILT Bottom of hole at 51.5 feet. 183.8 178.5 A-13 OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawald Amon PROJECT NAME Tukwila Property PROJECT NUMBER 06-373 PROJECT LOCATION 53rd Ave. S. and S. 160th St., Tukwila, Washington DATE STARTED 6/19/06 COMPLETED 6/19/06 GROUND ELEVATION 245 ft HOLE SIZE 6 -inches DRILLING CONTRACTOR Gregory Drilling GROUND WATER LEVELS: DRILLING METHOD Mud Rotary AT TIME OF DRILLING — BORING NUMBER B-5 PAGE 1 OF 2 LOGGED BY Anthony Coyne P.E. CHECKED BY Anthony Coyne P.E. AT END OF DRILLING -- NOTES 140 -pound automatic hammer, SPT sampler, 30 -inch drop 24hrs AFTER DRILLING 3.0 ft / Elev 242.0 ft TESTS U_ 20 0 0 MATERIAL DESCRIPTION MC=13% Loose, dark brown, Silty fine SAND (topsoil) Q. Loose, Tight brown, fine to medium SAND with Silt and occasional organics MC=10% Fines=7% , GS MC=27% MC=26% Fines=8% Loose, Tight brown, fine SAND with Silt Loose, Tight brown, fine SAND with Silt and occasional Interbedded Silt layers Medium dense, light brown, fine SAND with Silt MC=30% Stiff, Tight brown, Sandy SILT with thin, interbedded fine, clean SAND seams, oxidation present MC=32% Fines=23% , GS Medium dense, light brown, Silty fine SAND 9-16-16 MC=25% a Dense, light brown, Silty fine SAND MC=33% 31.0 Medium dense, gray, fine SAND with SILT Very stiff, gray, Sandy SILT 33.3 A-14 (Continued Next Page) 214.0 211.8 OTTO ROSENAU & ASSOCIATES, INC. 6747 M.L. King Way South Seattle, WA 98118 Telephone: (206) 725-4600 Fax: (206) 723-2221 CLIENT Mr. Jawaid Anion PROJECT NUMBER 06-373 BORING NUMBER B-5 PAGE 2 OF 2 PROJECT NAME Tukwila Property PROJECT LOCATION 53rd Ave. S. and S. 160th St. Tukwila, Washington 35 RECOVERY TESTS vi 0 ui 0 =C7 0. 0 0 MATERIAL DESCRIPTION 40 S9 BORING 9 100 9-11-12 (23) 45 SS 10 100 5-8-8 (16) 50 X SS 11 100 7-14-15 (29) X SS 12 100 4-8-6 (14) MC=31% MC=30% LL=33 PL=26 Fines=98% , GS, HYD, AL MC=29% MC=30% SP - SM ML ML ML ML 35.8 Medium dense, gray, fine SAND with SILT 209.3 Very stiff, gray SILT Very stiff, gray SILT Very stiff, gray SILT 51.5 Stiff, gray SILT 193.5 A-14 Bottom of hole at 51.5 feet. BORING LOG NOTES These notes and boring logs are intended for use with this geotechnical report for the purposes and project described therein. The boring logs depict ORA's interpretation of subsurface conditions at the location of the boring on the date noted. Subsurface conditions may vary, and groundwater levels may change because of seasonal or numerous other factors. Accordingly, the boring logs should not be made a part of construction plans or be used to define construction conditions. The approximate locations of the borings are shown on the Site Plan. The borings were located in the field by measuring from existing site features. "Boring Size" refers the diameter and type of auger used. "HSA" denotes hollow -stem auger. "SSA" denotes solid -stem auger. "BA" denotes bucket auger. "Sample Number and Type" refers to the sampling method and equipment used during exploration where: • "SS" indicates split -spoon sampler with 1-3/8" inside diameter and 2" outside diameter. • "ST" indicates sample attempted using a Shelby thin-wall sampling tube with 3" O.D. "N -Values" refer to the Standard Penetration Test which records number of blows from a 140 -pound hammer falling 30 inches required to advance a standard sampler eighteen inches. The blow counts required to drive the sampler through each 6 -inch interval is recorded. The number of blows to drive the sampler for the last 12 inches of driving are added together and is considered to be the N -Value. The N -Value is presented in parentheses on the boring logs. The actual blow count values for each 6 -inch interval is also presented. If the sample is driven less than 6 inches for a given interval, the actual distance driven is recorded. "Moisture Content (MC)" refers to the moisture content of the soil expressed in percent by weight of dry sample as determined in the laboratory. "Grain Size (GS)" refers to a grain size distribution analysis completed in general accordance with the ASTM D422 test procedure. "Hydrometer (HYD)" refers to a grain size distribution analysis completed in general accordance with the ASTM D422 test procedure. "Fines" is an estimate of the portion of a soil sample passing a No. 200 sieve as determined using the ASTM D422 test procedure. A-15 "Atterberg Limits (AL)" refers to a determination of the liquid and plastic limits of a cohesive soil using the ASTM D 4318 test procedure. "Dry Density (DD)" refers to an estimate of the dry density of a soil sample collected using a Shelby thin-wall sampling tube. "Direct Shear (DS)" refers to an estimate of the shear strength of a soil as determined using direct shear test equipment and performed in general accordance with ASTM D 3080. "Description and USCS Classification" refer to the materials encountered in the boring. The descriptions and classifications are generally based on visual examination in the field and laboratory. Where noted, laboratory tests were performed to determine the soil classification. The terms and symbols used in the boring Togs are in general accordance with the Unified Soil Classification System. Laboratory tests are performed in general accordance with applicable procedures described by the American Society for Testing and Materials. "7" Indicates location of groundwater at the time noted. TERMS for RELATIVE DENSITY of NON -COHESIVE SOIL Term Very Loose Loose Medium Dense Dense Very Dense Standard Penetration Resistance "N" 4 or Tess 5 to 10 11 to 30 31 to 50 Over 50 blows/foot TERMS for RELATIVE CONSISTENCY of COHESIVE SOIL Term Very Soft Soft Medium Stiff Stiff Very Stiff Hard Unconfined Compressive Strength 0 to 0.25 toffs/square-foot (tsf) 0.25 to 0.50 tsf 0.50 to 1.00 tsf 1.00 to 2.00''tsf 2.00 to 4.00 tsf Over 4.00 tsf A-16 DEFINITION of MATERIAL by DIAMETER of PARTICLE Boulder 8 -inches+ Cobble 3 to 8 inches Gravel 3 inches to 5mm Coarse Sand 5mm to 0.6mm Medium Sand 0.6mm to 0.2mm Fine Sand 0.2mm to 0.074mm Silt 0.074mm to 0.005mm Clay less than 0.005mm A-17 PLASTICITY INDEX 6 5 40 30 20 10 7 4 0 40 LIQUID LIMIT 90 100 SYMBOL EXPLORATION NUMBER SAMPLE DEPTH MOISTURE CONTENT (%) UOUID UMIT (%) PLASTIC OMIT (%) PLASTICITY INDEX. PI (%) SOIL DESCRIPTION 0 13-1 30 - 31.5 feet 32 45 26 19 Very stiff, gray SILT (ML) ■..■■■■■ B-2 50 - 51.5 feet 29 r:4 v,9NV41 7 Hard, gray SILT (ML) • B-3 50 - 51.5 feet 22 39 22 17 Hard, gray, lean CLAY (CL) A B-5 30 - 31.5 feet ■■■.. 33 28 ■ .J 41 0 V>‘* tiol . ■. ■ II.II Pi.r ': MH or CH VI,/ ocot . •ISI/I��J A', d ML or OL %�// I/I mr./AKO:i1I/.rArZ r 1f1 16 ,2� 1n I I �.. ..,. 40 LIQUID LIMIT 90 100 SYMBOL EXPLORATION NUMBER SAMPLE DEPTH MOISTURE CONTENT (%) UOUID UMIT (%) PLASTIC OMIT (%) PLASTICITY INDEX. PI (%) SOIL DESCRIPTION 0 13-1 30 - 31.5 feet 32 45 26 19 Very stiff, gray SILT (ML) ■ B-2 50 - 51.5 feet 29 33 26 7 Hard, gray SILT (ML) • B-3 50 - 51.5 feet 22 39 22 17 Hard, gray, lean CLAY (CL) A B-5 30 - 31.5 feet 30 33 28 7 Very stiff, gray SILT (ML) Note: Atterberg limits determined in general accordance with the ASTM D 4318 test procedure. ATTERBERG LIMIT TEST RESULTS Project Name: Tukwila Property Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 11, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-18 100 90 80 70 Z 60 Z 50 W U tY W 40 0. 30 20 10 0 Particle Size Distribution Report ASTM D 422 A V- I, N 4 .g A A 3 a g • p g • • • • 500 100 U 10 I % COBBLES I • % GRAVEL 0.0 29.9 1 GRAIN SIZE - mm 0.1 0.01 0.001 % SAND 44.0 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) 0.75 in. 100.0 0.625 in. 79.8 0.5 in. 77.0 0.375 in. 75.8 0.25 in. 72.4 #4 70.1 #10 65.0 #40 52.9 #100 33.7 #200 26.1 *. no specification provided) Sample No.: 2700 Source of Sample: Location: B1 Sample #2 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. % SILT 1 % CLAY I 26.1 Soil Description Sample #2700 - B1 Sample #2: Gray Silty Sand with gravel Atterberq Limits (ASTM D 4318) PL= NT LI .= NT • PI= NT Classification AASHTO= A-2-4(0) Coefficients D60= 0.793 D50= 0.358 D16= D10= Cc=: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 USCS= SM 085= 16.9 D80= 0.113 Cu' Date Tested: Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Protect No: 06-373 A-19 PERCENT FINER 100 90 80 70 60 50 40 30 Particle Size Distribution Report - ASTM D 422 n n A A o g s & 1 0 20 10 0 500 100 % COBBLES 10 1 GRAIN SIZE - mm 0.1 0.01 0.001 % GRAVEL % SAND 0.0 1.6 5.0 % SILT SIEVE SIZE PERCENT FINER SPEC.* PERCENT • PASS? (X=NO) 0.5 in. 100.0 0.375 in. 98.5 0.25 in. 98.5 #4 98.4 #10 98.3 #40 98.1 #100 95.2 #200 93.4 • *. no specification provided) Sample No.: 2700 Source of Sample: Location: B1 Sample #8 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. 74.8 % CLAY 18.6 Soil Description Sample #2700 - B1 Sample #8: Dark Gray Silt Atterberp Limits (ASTM D 43181 PL= 26.3 L.L= 45.4 PI= 19.1 Classification USCS= ML AASHTO A-4(0) Coefficients 085= 0.0290 D80= 0.0116 D50= 0.0098 D30= 0.0068 D15= 0.0043 D10= 0.0029 Cu= 3.99 Cc= 1.38 Date Tested: 7/27/2006 Tested By: A. Duong Remarks Classification (ASTM I)2487) Test Equipment ID: 5 Title: P.E. Client: Jawaid Amon Project:. Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 30 to 31.5 feet A-20 PERCENT FINER 100 90 80 70 60 50 40 30 Particle Size Distribution Report - ASTM D 422 5 N '.A r ft A I s -1, I I i 1 • 20 10 0 500 100 % COBBLES 10 GRAIN SIZE - mm 0.1 0.01 0.001 % GRAVEL % SAND 0.0 0.0 1.0 % SILT 1 % CLAY SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 100.0 #100 99.5 #200 99.0 no specification provided) Sample No.: 2700 Source of Sample: Location: 131 Sample#16 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. 99.0 Soil Description Sample 112700 - B1 Sample #16: Gray Silt Atterberci Limits (ASTM D 43181 PL= NT LL= NT P1= NT Classification USCS= ML AASHTO= A-4(0) Coefficients D85= 080= D50=. D30= D15= D10= Cu= cc= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM I)2487) Test Equipment ID: 5 Title: P.E. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Protect No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 60 to 61.5 feet A-21 PERCENT FINER 100 90 80 70 60 50 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 b n N r'gg a a &ea !III 0 1 J 500 100 10 1 4«' 0.1 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT #4 I % CLAY #10 55.3 44.0 #40 98.7 SIEVE SIZE PERCENT FINER SPEC.' PERCENT PASS? (X=NO) #4 99.3 #10 99.1 #40 98.7 #100 70.6 #200 44.0 (no specification provided) Sample No.: 2700 Source of Sample: Location: B2 Sample #1 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. Soil Description Sample #2700 - B2 Sample #1: Light brown Silty Sand Atterbercl Limits (ASTM D 4318) PL= NT L.L= NT PI= NT Classification USCS= SM AASHTO= A-4(0) Coefficients D85= 0.243 Deo= 0.112 D50= 0.0870 D30= D15= D10= Cu= Cc Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM 1)2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-22 100 90 80 70 CC W 80 Z z 50 W U W 40 30 20 10 0 Particle Size .Distribution Report - ASTM D 422 m n N - A g • • G 1 500 100 10 J SI7F - 0.1 0.01 0.001 % COBBLES % GRAVEL _ % SAND % SILT #4 1 % CLAY 0.0 0.0 79.9 20.1 #40 99.8 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 99.8 #100 68.6 #200 20.1 no specification provided) Sample No,: 2700 Source of Sample: Location: B2 Sample #4 Checked By: A. Coyne SO[l Description Sample #2700 - B2 Sample #4: Light brown Silty Sand t7►tterbera Limits JASTM D 4318) PL= NT LL= NT . Pl= NT USCS= SM Classification AASHTO= A-2-4(0) Coefficients D85= 0.221 D(0= 0.130 D50= 0.112 D30= 0.0852 D15= D10= Cu= Cc Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM ]D2487) Test Equipment ID: 5 Title: P.E. OTTO ROSS E NAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 15 to 16.5 feet A-23 • Particle Size Distribution Report - ASTM D 422 - S PI 100 90 80 � oI Ea' �t � � 70 Ce W 60 z 1- z 50 W 0 a 40 30 20 10 0 500 100 % COBBLES 0.0 10 GRAINSZE - mm 0.1 0.01 0.001 % GRAVEL %SAND 0.0 4.2 %SILT SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 #10 100.0 #40 99.5 #100 97.4 #200 95.8 * - no spec ifical ion provided) Sample No.: 2700 Source of Sample: Location: B2 Sample #12 Checked By: A. Coyne QTTO ROSENAU & ASSOCIATES, INC. 38.6 % CLAY 57.2 Soill Description Sample #2700 -132 Sample #12: Gray Silt Atterberq Limits (ASTM D 43181 PL= 26.5 LL= 33.3 PI= 6.8 Classification AASHTO= A-4(0) Coefficients D85= 0.0141 D60= 0.0052 D50= 0.0044 D30= 0.0025 D15= D10= Cc= Date Tested: 7/27/2006 Tested By: A. Duong Remarks Classification (ASTM D2487) Test Equipment ID: 5 USCS= ML Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 50 to 51.5 Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 feet A-24 100 90 80 70 re I.1,1 60 Z Z 50 W cc U a 40 a. 30 Particle Size Distribution Report - ASTM D 422 5 .S N a H i w 8& 20 10 0 500 100 10 } 0.1 0.01 0.001 % COBBLES % GRAVEL % SAND % SILT 0.75 in. I % CLAY 0.0 20.6 64.7 14.7 0.5 in. 86.0 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) 0.75 in. 100.0 0.625 in. 88.4 0.5 in. 86.0 0.375 in. 81.1 0.25 in. 79.9 #4 79.4 #10 78.1 #40 63.6 #100 22.3 #200 14.7 (no specification provided) Sample No.: 2700 Source of Sample: Location: B3 Sample #6 Checked By: A. Coyne Sb11 Description Sample #2700 -133 Sample #6: Light brow, Silty Sand with gravel Atterberq Llmfts (ASTM D 43181 PL= NT LL= NT PI= NT Classification AASHTO= A-2-4(0) Coeffi6lents DEi0= 0.393 D50= 0317 C 1� 5= 0.0796 D10= c.— 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM 1)2487) Test Equipment Ib: 5 USCS= SM D85= 11.7 030= 0.196 Cu- Date Tested: Title: P.E. OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 15 to 16.5 feet A-25 100 90 80 70 W 60 Z Z 50 w U re W 40 30 20 Particle Size Distribution Report - ASTM D 422 • .4• A r� a ` &a1 • 0 • 10 0 500 100 % COBBLES I 0.0 10 GRAIN SIZE - mm 0.1 0.01 0.001 % GRAVEL 9.5 SAND 2.7 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) 0.5 in. 100.0 0.375 in. 92.1 0.25 in. 90.5 #4 90.5 #10 90.5 #100 0 80.1 8.6 #200 87.8 no specification provided) Sample No.: 2700 Source of Sample: Location: B3 Sample #13 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. %SILT %CLAY . l 87.8 ., Soil Description Sample #2700 - B3 Satnple #13: Gray lean CLAY Atterberq Limits (ASTM D 43181 PL= 22.3 LL= 38.8 PI= 16.5 Classification USCS= CL AASHTO= A-4(0) Coefficients D85= Der D30= D145= D10= Cu= Cc= Date Tested: 7/25/2006 Tested By: J. Reeder, A. Duong D50= Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 50 to 51.5 Client: Jawaid Amon Protect: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 feet A-26 100 90 80 70 Ix W 60 Z LL � Z 50 uJ U WW 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 S $ A n !A _ 3 s C a i i3 III 500 100 10 1 GRAIN SIZE - mm 01 0.01 0.001 % COBBLES % GRAVEL % SANG % SILT 0.75 in. [ % CLAY 0.625 in. 64.4 25.7 0.5 in. 94.7 SIEVE SIZE PERCENT FINER SPEC.' PERCENT PASS? (X=NO) 0.75 in. 95.6 0.625 in. 95.6 0.5 in. 94.7 0.375 in. 93.0 0.25 in. 91.3 #4 90.1 #10 86.9 #40 76.2 #100 36.3 #200 25.7 (no specification provided) Sample No.: 2700 Source of Sample: Location: B4 Sample #2 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. Soli Description Sample #2700 -134 Sample #2: Gray, Silty sand Atterberp Limits (ASTM D 4318) PL= NT LLQ NT Pl= N'1� t; assiflcation USCS= SM AASHTO= A-2-4(0) Coefficients D85= 1.40 15,30= 0.294 050= 0.230 D30= 0.108 D 15= D10= u-. c Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet Client: Jawald Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-27 100 90 80 70 ZGb ti , 1— z 60 U CC nw. 40 30 20 10 Particle Size Distribution Report - ASTM D 422 c0 m 600 100 1 11 • lboul 0.1 0.01 0.001 COBBLES % GRAVEL _.... ... . /° SAND ....., ° % SILT 114 (� % CLAY 0.0 0.0 86.8 13.2 #40 97.5 SIEVE SIZE PERCENT FINER • SPEC.* PERCENT PASS? (X=NO) 114 100.0 #10 99.8 #40 97.5 #100 32.7 #200 13.2 * no specification provided) Sample No.: 2700 Source of Sample: Location: B4 Sample 115 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. Soil Description Sample #2700 - B4 Sample #5: Light broivn Silty sand Atterberq Limits (ASTM D 43181 PL= NT LL= NT PI= NT Classification USCS= SM • AASHTO= A-2-4(0) C.oefficlents D= 0.248 D= 0.0816 Cc= D85= 0.357 gp D50= 0.211 D30= 0.140 15 D10= Cu= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM (12487) Test Equipment ID: 5 Title: P.E. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 15 to 16.5 feet A-28 100 90 80 70 Cr W 60 LL .� 50 0 0 40 30 20 Particle Size Distribution Report - ASTM D 422 m N. a • 10 0 500 100 10 1 0.1 0.01 0.001 %.COBBLES % GRAVEL % SAND % SILT • 1 % CLAY 0.0 0.0 51.2 98.9 48.8 SIEVE SIZE PERCENT FINER SPEC." PERCENT PASS? (X=NO) #4 #10 100.0 99.9 • #40 98.9 #100 84.1 #200 48.8 " no specification provided) Sample No.: 2700 Source of Sample: Location: B4 Sample #9 Checked By: A. Coyne Soil DescrIptlbt) Sample #2700 - B4 Sample #9: Light brown Silty sand Atterberg Limits (ASTM D 4318 PL= NT LL= NT PI= NT Classification USCS= SM AASHTO= A-4(0) D85= 0.154 D30= Cu-. Coefficjents 060= 0.0911 D15= Cc= D50= 0.0766 D10= Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. OTTO ROSENAU & ASSOCIATES, INC. Client: • Jawaid Amon Projgct: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 35 to 36.5 feed_ A-29 100 90 80 70 W • 60 Z ti. Z 60 W ILI U 0 • 40 30 20 10 0 Particle Size Distribution Report - ASTM D 422 m n r. - e3 C d all 500 100 10 JSI7P- 0.1 0.01 0.001 COBBLES % GRAVEL --- hSAND ° PASS? (X=NO) ( % SILT 100.0 I % CLAY 0.0 0.0 92.8 l 7.2 #40 93.6 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 • #10 100.0 #40 93.6 #100 12.4 #200 7.2 no specification provided) Sample No.: 2700 Source of Sample: Location: -B5 Sample #2 Checked By: A. Coyne I! Description Sample #2700 - B5 Sample #2: Light brown, poorly -graded Sand with silt Atterbera LImlts (ASTM D 4318) PL= NT LL NT Pi= NT Classification USCS= SP -SM AASHTO= A-3 . )efflclents D85= 0.390 D60= 0.300 D50= 0.269 D30= 0.208 Di 5= 0.160 010= 0.109 Cu= 2.76 Cc= 1.33 Date Tested: 7/25/2006 Tested By: J. Reeder jlemarks Classification (ASTM I)2487) Test Equipment ID: 5 Title: P.E. Date Sampled: 6/22/2006 Elev./Depth: 5 to 6.5 feet OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 A-30 100 90 80 Particle Size Distribution Report - ASTM D 422 m n V- N «aa § !II 70 C W 60 Z Z 50 W 0 re L11 40 30 20 10 0 500 100 % coBi3LES 0.0 10 GRAIN SIZE - mm 0.1 0.01 0.001 % GRAVEL % SAND 0.0 91.5 % SILT I % CLAY SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 • #10 100.0 #40 97.6 #100 20.7 #200 8.5 • * no specification provided). Sample No.: 2700 Source of Sample: Location: B5 Sample #4 Checked By: A. Coyne 8.5 Soil Description Sample #2706 - B5 Sample #4: Light brown, poorly -graded Sand with Silt Atterberp Limits (ASTM D 43181 PL= NT LL= NT PI= NT Classification AASHTO= A-3 USCS= SP -SM D35 0.182 Cu= 3.01 Coefficients D60= 0.277 015= 0.126 Cc= 1.29 D50= 0.244 D10= 0.0920 Date Tested: 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 Title: P.E. OTTO ROSENAU & ASSOCIATES, INC. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 10 to 11.5 feet A-31 100 90 80 70 CC W 60 Z L 50 W U CC 40 30 20 10 0 600 Particle Size Distribution Report ASTM D 422 100 „ r gg a a 10 $ a 6 1 e 8 0 4 i it 0.01 0.001 % COBBLES % GRAVEL %SAND PASS? (X=NO) % SILT 100.0 1 (A CLAY 0.0 0.0 77.1• 22.9 #40 100.0 #100 86.5 SIEVE SIZE PERCENT FINER SPEC.* PERCENT PASS? (X=NO) #4 100.0 • #10 100.0 #40 100.0 #100 86.5 #200 22.9 * no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #6 Checked By: A. Coyne OTTO ROSENAU & ASSOCIATES, INC. Soil Description Sample #2700 - B5 Sample #6: Light brown Silty Sand Atterberq Limits ASTM D 43181 PL= NT 'LL= NT PI= NT Classification AASHTO= A-2.4(0) Coefficients D60= 0.112 D50= 0.100 D15= D10= Cc= 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D2487) Test Equipment ID: 5 USCS= SM D85= 0.148 D80= 0.0810 Cu= Date Tested: Title: P.E. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 20 to 21.5 feet A-32 100 90 80 70 30 20 10 b Particle Size Distribution Report - ASTM D 422 m n &x. 500 100 10 0.1 0.01 0.001 % COBBLES % GRAVEL %SAND %SILT #4 1 % CLAY 0.0 0.0 1.598.5 #40 . #100 99.3 SIEVE SIZE PERCENT FINER SPEC.' PERCENT PASS? (X=NO) #4 100.0 #10 100:0 #40 99.9 #100 99.3 #200 98.5 . no specification provided) Sample No.: 2700 Source of Sample: Location: B5 Sample #10 Checked By: A. Coyne OTTO ROS E NAU & ASSOCIATES, INC. Soli Description Sample #2700 -135 Sample #10: Gray Silt Atterberq limits (ASTM D 43181 PLS 26.5 LL.= 33.6 PI= 6.5 C4aissificatlon USCS= ML ' AASHTO= A-4(8) Coefficients D60= 7/25/2006 Tested By: J. Reeder Remarks Classification (ASTM D24$7) Test Equipment ID: 5 D85= D30= Cu= Date Tested: D50= D10= Title: P.E. Client: Jawaid Amon Project: Tukwila Property 16424 53rd Place S, Tukwila Project No: 06-373 Date Sampled: 6/22/2006 Elev./Depth: 40 to 41.5 feet A-33 8 8 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-1, Sample 9, Depth T 35 feet Soil Description: Gray Silt (ML) LEGEND: Phi = 4, measured angle of internal friction c = measured cohesion 0 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: Tukwila Property Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 11, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-34 SHEAR STRESS (ksfl 5 c=-0.7ksf 1 LEGEND: )81 Phi = 34.5' 8 9 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-1, Sample 14, Depth = 55-56 feet Soil Description: Gray Silt with trace fine gravel (ML) Phi = 4), measured angle of internal friction c = measured cohesion 0 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: Tukwila Property Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 11, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon CERA Protect Number: 06-373 A-35 SHEAR STRESS (ksfl 9 8 7 6 5 4 3 2 c = 0.33 ksf 0 -2 LEGEND: Phi = 30.3' 0 1 2 3 4 5 8 7 8 9 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 3, Depth = 12 feet Soil Description: Silty fine Sand (SP -SM) Phi = 4, measured angle of internal friction c = measured cohesion 10 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: Tukwila Property Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 11, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-36 SHEAR STRESS (ksfl c = 0.25 ksf 0 LEGEND: 8 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 5, Depth = 20 feet Soil Description: Dark gray Silty Sand (SM) Phi = ¢, measured angle of internal friction c = measured cohesion 9 10 Note: Direct shear test performed by HWA Geosciences In general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: Tukwila Property Location: 53rd Ave. S. and S 160th St. Tukwila, Washington Date: August 11, 2006 OTTO ROSENAU & ASSOCIATES, INC. -For+ Mr.,lawaid Amon - ORA Project Number: 06-373 A-37 9 8 7 N 6 0) 0) W 5 0) Q 4 W 2 0) 3 2 7 c = 0.3 ksf 0 -2 LEGEND: Phi = 3:.3' 0 2 3 4 5 6 7 8 9 NORMAL STRESS (ksf) DIRECT SHEAR TEST RESULTS Boring B-2, Sample 9, Depth = 35 feet Soil Description: Gray Silt (ML) Phi = 4), measured angle of internal friction c = measured cohesion 10 Note: Direct shear test performed by HWA Geosciences in general accordance with ASTM D 3080 test procedure. DIRECT SHEAR TEST RESULTS Project Name: Tukwila Property Location: 53rd Ave. S. and S 160th St., Tukwila, Washington Date: August 11, 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon C)RA Project Number: 06-373 A-38 Final site grades should be sloped to drain away from foundation 3% Min. Slope Roof drain - tightline Minimum 12 -inch wide zone of washed rock, fully - wrapped by geotextile fabric Non -woven geotextile fabric - Mirafi 140N or equivalent 4" diameter, rigid, perforated pipe Not to scale Notes: — 12" of impermeable soil cover 0 O o-oo o oo o oo 00000 00000 0 0 0 0 0 O o 00000 •Oo0 ••0 0 O 0°0 .00000 O 000 O 0000 O °O0 O O°O° O O°0° 00 0°0°00 0 0 0000000 0°0000 O 0 c► • .1 • es• 11 , . • . 1 . Foundation Wall If required, extend overexcavation laterally to either side of footing to a width equal to overexcavation depth (e.g. 12" lateral extension for 12" overexcavation depth) 1. The bearing surfaces for all proposed foundation elements should be evaluated by an ORA representative to verify that the foundation subgrade soils are capable of providing the required allowable bearing capacity. 2. AH pipes should be sloped to drain to an approved discharge point. 3. Washed rock used as drainage material should consist of 3 inch to 1-4 inch washed rock. 4. All temporary excavations must be completed in accordance with the recommendations of the geotechnical report for this project. TYPICAL FOUNDATION DETAIL Project Name: Tukwila Property Location: 53rd Ave. S and S 160th St., Tukwila, Washington Date: July 18. 2006 OTTO ROSENAU & ASSOCIATES, INC. For: Mr. Jawaid Amon ORA Project Number: 06-373 A-39 TKWPRENO 8-14-06 8:49 500 _ 400 _ a Tukwila Prop. Predevelop NO EQ 10 most critical surfaces, MINIMUM BISHOP FOS = 2.009 --'P1 100 _ 0 1 1 1 0 100 200 •300 400 500 X—AXIS (feet) 600 1 1 700 800 TKWPREEQ 8-14-06 8:55 Tukwila Prop. Predevelop PGA = 0.2g 10 most critical surfaces, MINIMUM BISHOP FOS = 1.318 0 100 200 300 400 500 600 X—AXIS (feet) 700 800 TKWPSTNO 8-14-06 9:02 Tukwila Prop. Postdevelp NO EQ Drain 500 10 most critical surfaces, MINIMUM BISHOP FOS = 2.057 400 ID 300 a) 4— N < 200 100 0 100 200 300 400 500 X—AXIS (feet) A-42 1 1 i ' 1 600 700 800 TKWPSTEQ 8-14-06 9:04 500 _ 400 _ Tukwila Prop. PGA=0.2 DRAINS 10 most critical surfaces, MINIMUM BISHOP FOS = 1.347 100 _ 0 0 I ' 100 200 300 400 500 600 700 800 X—AXIS (feet) A-43 RECEllfEb DEVE`pka AMON PROPERTY WETLAND DELINEATION PREPARED FOR: JOE ANION 1 6424 53RD PLACE SOUTH TUKWILA, WA 98188 JANUARY 2006 Amon Property Wetland Delineation SUMMARY At the request of Mr. Joe Amon, Adolfson Associates, Inc. (Adolfson) conducted wetland delineations and prepared this technical report for the Amon property, located in Tukwila Washington. The Amon property consists of two parcels (#5379200006 and #5379200005), on 3.64 acres. It is located within Section 26, Township 23 North, Range 4 East, in Tukwila, Washington (Figure 1). The site is triangular in shape bounded by South 160th Street to the south, 515t Ave South to the west, 53rd Avenue South to the east, a City of Seattle right-of-way and South 159th Street to the north. The applicant is proposing to develop the property. The project site was investigated for the presence of wetlands on October 4, 2005 by Adolfson biologists Ilon Logan and Janice Martin. Wetlands were delineated according to the methods outlined in the Washington State Wetlands Identification and Delineation Manual (Washington State Department of Ecology [Ecology], 1997), a manual consistent with the U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987). The project site is situated in a residential area, within the Gilliam Creek Basin of the City of Tukwila. The site is undeveloped containing mostly pioneer deciduous forest and shrubs (Photo 1). The property slopes down to the northeast in three locations and flattens out in between those steeper areas. Two wetlands were identified in the central portion of the property (Figure 6). Vegetation, soils, and hydrology were examined at five sample plots established on the project site. These two wetlands are considered Type 3 wetlands according to Title 18.45 of the City of Tukwila Municipal Code (TMC). Wetland A covers approximately 3,070 square feet (0.07 acre) and is a palustrine scrub -shrub wetland dominated by salmonberry and Cooley's hedge -nettle (Photo 2). Wetland B is more linear and encompasses 1,890 square feet (0.04 acre). Wetland B is a palustrine scrub -shrub wetland dominated by salmonberry, giant horsetail and Cooley's hedge - nettle (Photos 3 and 4). A third wetland, Wetland C, occurs on property owned by the City of Seattle, as well as the City of Tukwila and is a City of Seattle right-of-way for an underground water pipeline (Figure 6). A small portion, approximately 16 square feet, of Wetland C is located on the Amon property. Wetland C is a palustrine emergent and scrub -shrub wetland, dominated by reed canarygrass, salmonberry and giant horsetail (Photos 5, 6 and 7). Wetland C at 4,026 square feet (0.09 acre) is considered a Type 3 wetland according to TMC. A spring fed drainage runs through Wetland C, flowing west to east. According to TMC 18.15.100 this is a Type 4 watercourse that requires a 50 -foot wide buffer. Type 3 wetlands require a 15 -foot building set back, and a 50 -foot buffer from the wetland edge according to TMC 18.45.080. Adolfson Associates, Inc. Page i January 2006 Amon Property Wetland Delineation TABLE OF CONTENTS SUMMARY 1.0 PROJECT AUTHORIZATION AND SCOPE OF WORK 1 2.0 SITE DESCRIPTION 1 3.0 WETLAND DEFINITION AND REGULATIONS 1 4.0 METHODS 1 4.1 REVIEW OF EXISTING INFORMATION 2 4.2 ON-SITE INVESTIGATION 2 4.2.1 Determining the Presence of Wetlands and Delineating Wetland Boundaries 2 4.2.2 Classing Wetlands 3 5.0 FINDINGS 3 5.1 EXISTING INFORMATION 3 5.2 WETLANDS DETERMINATIONS 4 5.2.1 Wetland A 4 5.2.2 Wetland B 4 5.2.3 Wetland C 5 5.3 STREAMS AND OTHER DRAINAGE FEATURES 5 5.4 UPLAND DESCRIPTION 6 5.5 WILDLIFE HABITATS 6 5.5.1 Site Observations 6 5.5.2 Previously Identified Species and Habitats in Project Area 6 6.0 REGULATORY IMPLICATIONS 6 6.1 FEDERAL REGULATIONS 6 6.2 STATE REGULATIONS 7 6.3 LOCAL REGULATIONS 7 7.0 LIMITATIONS 8 8.0 REFERENCES 9 9.0 GLOSSARY 11 FiGURES AND PHOTOGRAPHS 16 APPENDIX A: METHODS USED TO EVALUATE WETLAND CHARACTERISTICS A-1 APPENDIX B: COMMON AND SCIENTIFIC NAMES OF PLANTS AND THEIR WETLAND INDICATOR STATUS B-1 APPENDIX C: DATA SHEETS C-1 Adolfson Associates, Inc. Page ii January 2006 Amon Property Wetland Delineation 1.0 PROJECT AUTHORIZATION AND SCOPE OF WORK At the request of Mr. Joe Amon, Adolfson Associates, Inc. (Adolfson) performed wetland delineations and prepared this technical report for the Amon Property site, located in the City of Tukwila, Washington. All rights -of -entry to the subject property for the purpose of conducting this study was granted by Mr. Amon. The boundaries of the study area were established based on several discussions with Mr. Amon and a parcel map. The Scope of Work for this project included wetland determinations and delineations, which are summarized in this technical report. A brief discussion of regulatory implications and permitting considerations is also included in this report. An analysis of potential wetland impacts and the development of a mitigation plan were not included in this Scope of Work.. The applicant is proposing to develop the project site. In the event there are impacts to on-site wetlands due to the proposed development activity, a mitigation report will be prepared based on City of Tukwila requirements. 2.0 SITE DESCRIPTION The Amon property consists of two parcels totaling 3.64 acres located within Section 26, Township 23 North, Range 4 East, in Tukwila, Washington (Figure 1). The triangular-shaped site is bounded by South 160th Street to the south, 51st Avenue South to the west, 53`d Avenue South to the east, a City of Seattle right-of-way and South 159th Street to the north. The project site is situated in a residential area, within the Gilliam Creek Basin of the City of Tukwila. The site is undeveloped containing mostly pioneer deciduous forest and shrubs (Photo 1). The property slopes down to the northeast in three locations and flattens out in between those steeper areas. 3.0 WETLAND DEFINITION AND REGULATIONS The characteristics of an area that result in its classification as "wetland" have been formally defined by federal and state agencies, as described in Appendix A. Numerous federal, state, and local regulations govern development and other activities in or near wetlands; at each level, there are typically several agencies charged with such powers (Ecology, 1994). Specific regulatory implications concerning the subject property are summarized later in this report. 4.0 METHODS Two levels of investigation were conducted for the analysis of wetlands on the subject property: a review of existing information and an on-site investigation. Adolfson Associates, Inc. Page 1 January 2006 Amon Property Wetland Delineation 4.1 Review of Existing Information A review of existing literature, maps, and other materials was conducted 1:o identify wetlands or site characteristics indicative of wetlands on the subject property. These sources can only indicate the likelihood of the presence of wetlands; actual wetland determinations must be based upon data obtained from field investigations. Several documents were reviewed: • The U.S. Geological Survey 7.5 minute Topographic Map, Des Moines quadrangle. 1995. King County GIS revised 2004. • The Soil Survey of King County Area, Washington. U.S. Department of Agriculture Natural Resources Conservation Service 2003. King County GIS revised 2004. • The National Wetland Inventory, Des Moines. U.S. Fish and Wildlife Service. 1988. • Hydric Soils of the State of Washington. Natural Resources Conservation Service, 1995. • The King County Sensitive Areas Folio. King County Department of Surface Water Management. 1990. • The City of Tukwila Wetland/Watercourse and Buffer Map. City of Tukwila Department of Community Development. July 15, 2004. • The Washington State Department of Fish and Wildlife Priority Habitat and Species Map. 2005. 4.2 On-site Investigation 4.2.1 Determining the Presence of Wetlands and Delineating Wetland Boundaries Methods defined in the Washington State Wetlands Identification and Delineation Manual (Ecology, 1997), a manual consistent with the U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), were used to determine the presence and extent of wetlands on the subject property. Washington state and all local governments must use the state delineation manual to implement the Shoreline Management Act and/or the local regulations adopted pursuant to the Growth Management Act. The methodology outlined in the manual is based upon three essential characteristics of wetlands: (1) hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three characteristics must all be present in order to determine that an area is a wetland (unless problem areas or atypical situations are encountered). The "routine on-site determination method" was used to determine the wetland boundaries. The routine method is used for areas equal to or less than five acres in size, or for larger areas with relatively homogeneous vegetative, soil, and hydrologic properties. Formal data plots were established in areas of relatively homogeneous vegetation, where information regarding each of the three -wetland parameters (vegetation, soils, and hydrology) Adolfson Associates, Inc. Page 2 January 2006 Amon Property Wetland Delineation was recorded. Dominant herbs and saplings/shrubs within a five-foot radius, and dominant trees and woody vines within a 30 -foot radius from the data plot center were recorded on the data form (Ecology, 1997). This information was used to distinguish wetlands from non -wetlands. If wetlands were determined to be present on the subject property, the wetland boundaries were delineated. Wetland boundaries were identified with sequentially numbered colored flagging imprinted with the words WETLAND DELINEATION. Data plot locations were also marked with colored flagging. The methods used to assess wetland characteristics are described in greater detail in Appendix A. Please note that common plant names are used throughout this text; the scientific names are presented in Appendix B. 4.2.2 Classifying Wetlands Two classification systems are commonly used to describe wetlands. The hydrogeomorphic (HGM) system describes wetlands in terms of their position in the landscape and the movement of water in the wetland (Brinson, 1993). The U.S. Fish and Wildlife Service classification system (Cowardin et al., 1979) describes wetlands in terms of their vegetation communities; these include, for example, emergent, scrub -shrub, and forested community types. 5.0 FINDINGS The following sections describe the results of the field investigation conducted by Ilon Logan and Janice Martin within the Amon property site on October 4, 2005. These sections describe the three on-site wetlands, one of which extends off site, upland habitats, and wildlife observations. Five data plots were established within relatively uniform areas of vegetation on the site. Data sheets for each of the formal data plots evaluated for this project are provided in Appendix C. 5.1 Existing Information The U.S. Geological Survey (USGS) Topographic Map does not indicate that wetlands occur on the project site (Figure 2). The USGS map shows the moderate to steep slopes found on the project site, decreasing in elevation towards the northeast. According to the National Wetlands Inventory (NWI) map there are no wetlands mapped on the project site (Figure 3). In contrast, the City of Tukwila Wetland/Watercourse and Buffer Map (2004) documents a wetland on property owned by the City of Seattle, located north of the project property boundary, and within the City of Seattle right-of-way, (Figure 4). In addition, the Tukwila map shows a stream flowing through the wetland. The Soil Survey of King County (King County GIS, 2004) maps the entire project site as Arents, Alderwood material (AmC) (Figure 5). Arents, Alderwood soil has convexslopes from six to 15 percent, with some at 30 percent. It is a gravelly sandy loam that is moderately, well drained, Adolfson Associates, Inc. Page 3 January 2006 Amon Property Wetland Delineation has variable permeability, and moderate to severe erosion hazard (Snyder, et al., 1973). Arent, Alderwood material is considered non -hydric (NRCS, 1995). 5.2 Wetlands Determinations Three wetlands were delineated during the field visit on October 4, 2005. The three wetlands (Wetlands A, B and C) were identified on the property. The third wetland, Wetland C extends offsite on property owned by the City of Tukwila, as well as, the City of Seattle and is within the City of Seattle right-of-way. The following describes each of the wetlands and the upland habitats found on the site. Figure 6 shows the locations of the wetlands on. the Amon property. Mead, Gillman and Associates, of Woodinville, Washington, have professionally surveyed the wetland boundaries. Wetland delineation data sheets are included in this report, in Appendix C. 5.2.1 Wetland A Location and Geomorphic Setting. Wetland A is 3,070 square feet (0.07 acre), palustrine scrub - shrub wetland located in the west central portion of the project site (Figure 6). Located between two hillsides that slope down towards the wetland, the wetland is located within a depressional area that appears to have no outlet (Photo 2). Data Plot 1 (DP -1) characterizes Wetland A. Soils. Soils in this data plot were very dark brown (1OYR 2/2) sandy loam to a depth of eight inches. From eight to 16 inches below the soil surface, the soils were a dark grayish -brown (2.5Y 4/2) loamy sand, with mottling. The mottles (medium, common and distinct) were dark yellowish -brown (1 OYR 4/6). Vegetation. Wetland vegetation is dominated by salmonberry and Cooley's hedge -nettle. Himalayan blackberry occurs along the hillside and partially within the wetland. The salmonberry and Cooley's hedge -nettle occur in wetlands. Hydrology. Wetland A appears to be an isolated wetland that is seasonally saturated due to high groundwater and precipitation. Based on the presence of hydrophytic vegetation and hydric soils during our field delineation in October 2005, and due to its location in a depressional area, Adolfson concluded that hydrologic conditions would likely be present during the growing season. 5.2.2 Wetland B Location and Geomorphic Setting. Wetland B is 1,890 square feet (0.04 acre) in size and linear in shape. It is a palustrine scrub -shrub wetland located near the center of the project site (Figure 6). It is also located within a depressional area between two hillsides that slope down towards the wetland (Photo 3). No outlet was observed in the wetland. Data Plot 3 (DP -3) characterizes Wetland B. Adolfson Associates. Inc. Page 4 January 2006 Amon Property Wetland Delineation Soils. Soils in this data plot, from zero to seven inches below ground surface, were a black (10YR 2/1) sandy clay loam (Photo 4). From seven to 16 inches in depth, the soils observed were a greenish gray 5/10Y (gleyed) sandy loam. Vegetation. Giant horsetail, Cooley's hedge -nettle and salmonberry were the dominant vegetation present within DP -3. Other vegetation present included skunk cabbage and lady fem. These species occur in wetlands. Hydrology. Wetland C appears to be an isolated wetland that is permanently saturated and seasonally inundated due to high groundwater and precipitation. Indicators of wetland hydrology included saturated soils at the surface of the soil pit, and free water at 11 inches below surface depth. Based on the presence of hydrophytic vegetation, hydric soils and hydrology during our field delineation in October 2005, in addition to the topography of the depressional area, Adolfson concluded that this area was wetland. 5.2.3 Wetland C Location and Geomorphic Setting. The majority of Wetland C is located within the City of Seattle right-of-way, and a portion is within the City of Tukwila both are to the north of the Amon property boundary (Figure 6). However, a very small portion, 16 square feet of Wetland C is within the Amon property. Wetland C is a palustrine, emergent and scrub -shrub wetland, with a total area of 4,026 square feet (0.09 acre). The City of Tukwila owns the property that encompasses most of Wetland C. Data Plot 4 (DP -4) characterizes this wetland. Soils. Soils in this data plot from zero to 10 inches below soil surface, were a very dark brown (10YR 2/2) sandy clay loam. From 10 to 16 inches in depth, the soils observed were a black (2.5Y 4/1) sandy loam with mottling. The mottles (medium, common and distinct) were dark yellowish brown (10YR 4/4). The odor of sulphur was present within the data plot, which is also indicative of redoximorphic conditions. Vegetation. Wetland C vegetation is dominated by reed canarygrass and giant horsetail (Photo 5). These species occur in wetlands. Hydrology. Soils were saturated to the surface within DP -4. A small spring fed drainage channel extends east of Wetland C. Flow was observed in Wetland C from the west to the east and eventually infiltrating into the ground surface. The drainage channel is further described in Section 5.3. Based on the presence of hydrophytic vegetation and hydric soils, Adolfson concluded that hydrologic indicators would be present during the growing season. 5.3 Streams and Other Drainage Features During the field delineation in October 2005, a small spring fed stream was observed entering Wetland C from the west via a culvert (Photo 6). The drainage flows east through the wetland, along compacted soils (Photo 7). According to TMC 18.15.100 this is a Type 4 watercourse that requires a 50 -foot wide buffer. Adolfson Associates, Inc. Page 5 January 2006 Amon Property Wetland Delineation 5.4 Upland Description Through out the project area upland vegetation includes big leaf maple in the canopy layer, with English ivy, and Himalayan blackberry in the understory (Photo 8). Other vegetation included red alder, Indian plum, reed canarygrass and other upland grasses such as orchard grass. There were no indicators of wetland hydrology or hydric soils within the upland areas. Soils were dry sandy loam to a depth of at least 16 inches below surface. No redoximorphic features were found in the soil profiles during the site visit in October 2005. 5.5 Wildlife Habitats 5.5.1 Site Observations The on-site wetlands and surrounding buffers support wildlife habitat, such as large trees, shrub thickets, and snags. Species observed during the field investigations included the Pacific tree frog, American robin, black -capped chickadee, and Steller's jay. Other species of birds, mammals, reptiles, and amphibians in addition to those observed are expected to use habitat on the project site. For example, nocturnal species may be present that were not active during the site visit, or other species may only be highly visible or present in this area during certain seasons. 5.5.2 Previously Identified Species and Habitats in Project Area The Washington State Department of Fish and Wildlife (WDFW) provides maps with locations of priority habitat species. Based on these maps, Adolfson noted a few open water emergent wetlands within one mile of the project area, as well as, the Green River and two urban natural open space designations. This information suggests that priority habitats are located near the project site. However, priority species were not observed during our site visit in October 2005. 6.0 REGULATORY IMPLICATIONS Wetlands are regulated at the federal, state, and local level. Agencies withjurisdiction include the U.S. Army Corps of Engineers (Corps), Washington State Department of Ecology (Ecology), and the City of Tukwila. The Washington Department of Fish and Wildlife regulates work within streams. Regulatory implications associated with development in wetlands include, but may not be limited to, those discussed in this section. All applicable permits should be obtained prior to developing or otherwise altering streams or wetlands. 6.1 Federal Regulations The Corps regulates discharges of dredged or fill materials into waters of the United States, including wetlands, under Section 404 of the Clean Water Act. The purpose of the Clean Water Act is to "restore and maintain the chemical, physical, and biological integrity of the Nation's Adolfson Associates, Inc. Page 6 January 2006 Amon Property Wetland Delineation waters." A Section 404 permit may be required if a proposed project involves filling wetlands or altering streambeds or other waters of the U.S. The Corps has established two types of permit programs under Section 404: nationwide and individual. Nationwide permits are issued when a proposed activity will have minimal adverse impacts to wetlands. All other projects are evaluated under the individual permitting process. The Corps determines which permitting process is used for a proposed project. The Corps will require that wetland impacts be avoided or minimized to the extent practicable, and mitigation will likely be required for unavoidable wetland impacts. 6.2 State Regulations The state certification process under Section 401 of the federal Clean Water Act is usually triggered through a Section 404 permit application. Section 401 directs each state to certify that proposed in -water activities will not adversely affect water quality or violate state aquatic protection laws. In Washington State, Ecology is responsible for administering the state certification program. Ecology may issue approval, approval with conditions, denial, or a request for delay due to lack of information. Any conditions attached to the 401 certification become part of the Section 404 permit. King County is one of the 15 coastal counties in Washington regulated under the Washington State Coastal Zone Management (CZM) Program. Activities that would affect coastal resources and involve approvals from the federal government (such as a Section 404 permit) must be evaluated for CZM compliance through a process called "federal consistency." The Washington State Department of Ecology administers the CZM program in this state. If relocation or alteration of stream culverts or other in -stream work is proposed as part of the project, a Hydraulic Project Approval (HPA) would be required from the Washington Department of Fish and Wildlife under the state Hydraulic Code (RCW 77.55, WAC 220-110) 6.3 Local Regulations Sensitive areas in the City are defined and regulated through Chapter 18.45: Environmentally Sensitive Areas of the Tukwila Municipal Code (TMC). As part of the 2004 Comprehensive Plan Update, the City of Tukwila updated its Sensitive Areas Ordinance to ensure that it meets statewide planning regulations. Key topics included reviewing policies and development codes for environmentally sensitive areas, as well as adopting new countywide housing and employment targets. At that time the City decided not to use the revised Washington State Wetlands Rating System for Western Washington (2004). Therefore, the current rating system remains in effect at this time and there are no future plans to adopt the Ecology rating system. The two wetlands (Wetland A and B), located in the central portion of the property are considered Type 3 wetlands according to Title 18.45 of the TMC (Figure 6). The third wetland, Wetland C, owned by the City of Tukwila, and located within the City of Seattle right-of-way is also considered a Type 3 wetland according to Title 18.45 of the TMC. Type 3 wetlands require a 15 -foot building set back, and a 50 -foot buffer from the wetland edge according to TMC 18.45.080. Adolfson Associates, Inc. Page 7 January 2006 Amon Property Wetland Delineation The spring fed drainage flowing through Wetland C, is a Type 4 watercourse according to TMC 18.15.100 and therefore, requires a 50 -foot wide buffer as well. A mitigation plan for any effects to on-site wetlands, the off-site watercoutrse, or to sensitive area buffers, will be required by the City for approval under TMC 18.45.090. 7.0 LIMITATIONS Within the limitations of schedule, budget, and scope -of -work, we warrant that this study was conducted in accordance with generally accepted environmental science practices, including the technical guidelines and criteria in effect at the time this study was perfonned, as outlined in the Methods section. The results and conclusions of this report represent the authors' best professional judgment, based upon information provided by the project proponent in addition to that obtained during the course of this study. No other warranty, expressed or implied, is made. Adolfson Associates, Inc. Page 8 January 2006 Amon Property Wetland Delineation 8.0 REFERENCES Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of Wetlands and Deepwater Habitats of the United States. FWS/OBS-79/31. U.S. Fish and Wildlife Service. Ecology (Washington State Department of Ecology). 1991. Shoreline Management Handbook: First Edition. Publication No. 90-45. Olympia, Washington. Ecology (Washington State Department of Ecology). 1992. The Growth .Management Act and the State Environmental Policy Act: A Guide to Interrelationships. Publication No. 92- 07. Olympia, Washington. Ecology (Washington State Department of Ecology). 1994. Wetlands Regulations Guidebook. Publication No. 88-5. Olympia, Washington. Ecology (Washington State Department of Ecology). 1997. Washington State Wetlands Identification and Delineation Manual. Publication No. 96-94. Olympia, Washington. Ecology (Washington State Department of Ecology). 2004. Washington State Wetland Rating System for Western Washington Revised. Publication No. 04-06-025. Olympia, Washington. Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual. Technical Report Y-87-1. U.S. Army Engineer Waterways Experiment Station, Vicksburg, Massachusetts. Federal Register. 1982. Title 33: Navigation and Navigable Waters; Chapter II, Regulatory Programs of the Corps of Engineers. Vol. 47, No. 138, p. 31810. U.S. Government Printing Office, Washington, DC. Federal Register. 1986. 33 CFR Parts 320 through 330: Regulatory Programs of the Corps of Engineers; Final Rule. Vol. 51, No. 219, pp. 41206-41260. U.S. Government Printing Office, Washington, DC. Federal Register. 1988. 40 CFR Part 230. Guidelines for Specification of Disposal Sites for Dredged or Fill Material. Vol. 45, No. 249, Pages 85336-85357. U.S. Government Printing Office, Washington, DC. Federal Register. 1994. Changes in Hydric Soils of the United States. July 13. Washington, DC. Hitchcock, C.L., and A. Cronquist. 1973. Flora of the Pacific Northwest: An Illustrated Manual. University of Washington Press, Seattle, Washington. King County Department of Surface Water Management. 1990. The King County Sensitive Areas Folio. Adolfson Associates, Inc. Page 9 January 2006 Amon Property Wetland Delineation King County. 2004. The Soil Survey of King County. U.S. Department of Agriculture Natural Resources Conservation Service 2003. King County GIS revised. Munsell Color. 2000. Munsell Soil Color Charts. Greta Macbeth, New Windsor, New York. Snyder, D.E., P.S. Gale, and R.F. Pringle. 1973. Soil Survey of King County Area, Washington. U.S. Soil Conservation Service, Washington, DC. NRCS (Natural Resources Conservation Service). 1995. Hydric Soils List for Washington. Revised December 15, 1995. NRCS (Natural Resources Conservation Service). 1998. Field Indicators of Hydric Soils in the United States, Version 4.0. G.W. Hurt, P.M. Whited, and R.F. Pringle (eds.), United States Department of Agriculture, Ft. Worth, Texas. Tukwila Department of Community Development. 2004. Tukwila Wetland/Watercourse and Buffer Map. USFWS (U.S. Fish and Wildlife Service). 1997. National List of Vascular Plant Species that Occur in Wetlands: 1996 National Summary. Biol. Rpt. 88(26.9). A draft revision of P.B. Reed, Jr., 1988, National List of Plant Species That Occur in Wetlands: Northwest (Region 9). United States Department of Interior, Washington, DC. USFWS (U.S. Fish and Wildlife Service). 1988. The National Wetland Inventory, Des Moines. quadrangle. 1995. King County GIS revised 2004. Washington State Department of Fish and Wildlife. 2005. Washington State Department of Fish and Wildlife Priority Habitat and Species Map. Vepraskas, M.J. 1999. Redoximorphic Features for Identfing Aquic Conditions. Technical Bulletin 301. North Carolina Agricultural Research Service, North. Carolina State University, Raleigh, North Carolina. Adolfson Associates, Inc. Page 10 January 2006 Amon Property Wetland Delineation 9.0 GLOSSARY agricultural wetland - Areas where wetland soils and hydrology remain, but hydrophytic vegetation has been removed to allow a crop to be grown. anaerobic - A situation in which molecular oxygen is absent (or effectively so) from the environment. atypical situation - Areas in which one or more wetland parameters (vegetation, soil, and/or hydrology) have been sufficiently altered by recent human activities or natural events to preclude the presence of wetland indicators of the parameter. "Recent" is intended t:o mean that period of time since legal jurisdiction of an applicable law began. best management practices (BMPs) — The physical, structural, and/or managerial practices that, when used singly or in combination, prevent or reduce pollutant discharges. buffer - A designated area along the perimeter of a stream or wetland that is regulated to control the negative effects of adjacent development from intruding into the aquatic resource. concretion - A local concentration of chemical compounds such as calcium carbonate or iron oxide in the soil that forms a grain or nodule of varying size, shape, hardness, and color. Concretions of significance in hydric soil are usually iron and/or manganese oxides occurring at or near the soil surface that develop under conditions of prolonged soil saturation. dominant species - A plant species that exerts a controlling influence on or defines the character of a community. emergent - A plant that grows rooted in shallow water, the bulk of which emerges from the water and stands vertically. Usually applied to non -woody vegetation. emergent wetland - In the USFWS classification system (Cowardin et al., 1979), a wetland characterized by erect, rooted, herbaceous hydrophytes, excluding mosses and lichens. enhancement - An improvement in the functions and values of an existing wetland. fill material - Any material placed in an area to increase the surface elevation. forested wetland - In the USFWS classification system (Cowardin et al., ].979), a wetland characterized by woody vegetation that is six meters (20 feet) tall or taller. 404 permit - A permit issued by the U.S. Army Corps of Engineers under Section 404 of the federal Clean Water Act that allows an activity (filling) within a wetland. A 404 permit usually requires compensation or mitigation for the wetland impacts. gleyed - A soil condition resulting from prolonged soil saturation, manifested by the presence of bluish or greenish colors throughout the soil or in mottles (spots or streaks) among other colors. Adolfson Associates, Inc. Page 11 January 2006 Amon Property Wetland Delineation groundwater — That portion of the water below the ground surface that is under greater than atmospheric pressure. herbaceous - Having the characteristics of an herb; a plant with no persistent woody stem above the ground. hydric soil — A soil that formed under conditions of saturation, flooding, or ponding long enough to develop anaerobic conditions in the upper part. hydrogeomorphic (HGM) classification — A system of classifying wetlands based on their position in the landscape and the movement of water within the wetland. hydrology — The science dealing with the properties, distribution, and circulation of water. hydrophyte - Any plant growing in water or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content. The sum total of hydrophytes in an area is known as "hydrophytic vegetation." in-kind compensation - Compensation for lost wetland habitat with a replacement wetland of the same habitat type. inundation — A condition in which water from any source temporarily or permanently covers a land surface. invasive plant species - Plant species that become established easily in disturbed conditions, reproduce readily, and often establish monocultures. Most invasive plants are non-native species; they were introduced to the Northwest intentionally or unintentionally by humans. Examples of common invasive species in the Pacific Northwest are Scot's broom, Canada thistle, hedge bindweed, English ivy, reed canarygrass, purple loosestrife, and soft rush. lacustrine - In the USFWS classification system (Cowardin et al., 1979), .a freshwater area has all of the following characteristics: (1) situated in a topographic depression or a dammed river channel; (2) has less than 30% coverage of trees, shrubs, persistent emergent plants, mosses, or lichens; and (3) total area exceeds eight hectares (20 acres). For areas less than 20 acres, an area is considered lacustrine if it has an active wave -formed or bedrock shoreline or is deeper than 6.6 feet in the deepest part. "Freshwater" means less than 0.5 parts per thousand ocean -derived salts. mitigation — Defined in WAC 197-11-766 as: (1) Avoiding the impact altogether by not taking a certain action or parts of an action; (2) Minimizing impacts by limiting the degree or magnitude of the action and its implementation, by using appropriate technology, or by taking affirmative steps to avoid or reduce impacts; (3) Rectifying the impact by repairing, rehabilitating, or restoring the affected environment; Adolfson Associates, Inc. Page 12 January 2006 Amon Property Wetland Delineation (4) Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action; (5) Compensating for the impact by replacing, enhancing or providing substitute resources or environments: and/or (6) Monitoring the impact and taking appropriate corrective measures. mottles - Spots or blotches of different color or shades of color interspersed within the dominant color in a soil layer. This usually results from periodic anaerobic conditions in the soil. 100 -year floodplain - The flood with a 100 -year recurrence interval; those areas identified as Zones A, A1-30, AE, AH, AO, A99, V, V1-30, and VE on most current Federal Emergency Management Agency (FEMA) Flood Rate Insurance Maps, or areas identified as 100 -year floodplain on applicable local Flood Management Program maps. ordinary high-water mark - The line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank; changes in the character of soil or vegetation; topographic shelves; or the presence of a line of litter or debris. out -of -kind compensation - Compensation for lost wetland habitat with a replacement wetland of a different habitat type. palustrine - In the USFWS classification system (Cowardin et al., 1979), freshwater areas dominated by trees, shrubs, persistent emergent plants, mosses, or lichens. They can be non - tidal or tidal. Palustrine also includes wetlands lacking this vegetation but with the following characteristics: (1) area less than 20 acres; (2) no active wave -formed or bedrock shoreline; (3) water depth in the deepest part is less than 6.6 feet at low water. "Freshwater" means having less than 0.5 parts per thousand ocean -derived salts. persistent emergents — Emergent plants that remain standing at least until the beginning of the next growing season. reach - A length of stream channel with uniform characteristics. restoration - To improve a disturbed or altered wetland by returning wetland parameters that may be missing. rhizosphere - The zone of soil surrounding a plant root in which interactions between the living root and microorganisms occur. riverine - In the USFWS classification system (Cowardin et al., 1979), freshwater areas that are contained within a channel and are not dominated by trees, shrubs, and persistent emergent plants. Examples include rivers and streams. "Freshwater" means having less than 0.5 parts per thousand ocean -derived salts. Adolfson Associates, Inc. Page 13 January 2006 Amon Property Wetland Delineation 123.11(m) which also meet the criteria of this definition) are not waters of the United States. 8. Waters of the United States do not include prior converted cropland. Notwithstanding the determination of an area's status as prior converted cropland by any other federal agency, for the purposes of the Clean Water Act, the final authority regarding Clean Water Act jurisdiction remains with the EPA. wetland - Transitional lands between terrestrial and aquatic systems, where the water table is usually at or near the surface or the land is covered by shallow water. Wetlands must have one or more of the following attributes: (1) at least periodically, the land supports predominantly hydrophytes; (2) the substrate is predominantly undrained hydric soil; and (3) the substrate is non -soil and is saturated with water or covered by shallow water at some time during the growing season of each year. wetland boundary — The point on the ground at which a shift from wetlands to non -wetlands or aquatic habitat occurs. wetland hydrology - Wetland hydrology is considered to be present when there is permanent or periodic inundation or soil saturation for more than 12.5% of the growing season (typically two weeks in lowland Pacific Northwest areas). Areas that are inundated or saturated for between 5% and 12.5% of the growing season in most years may or may not be wetlands. Areas inundated or saturated for less than 5% of the growing season are non -wetlands (Ecology, 1997). wetland indicator status (WIS) - Categories assigned to plant species based upon the estimated probabilities (expressed as a frequency of occurrence) of the species occurring in a wetland or a non -wetland. Wetland indicator status categories include the following: Obligate (OBL): species that almost always occur in wetlands under natural conditions (estimated probability >99%). Facultative wetland (FACW): species that usually occur in wetlands (estimated probability 67 to 99%), but are occasionally found in non -wetland areas. Facultative (FAC): species that are equally likely to occur in wetlands (estimated probability 34 to 66%) or non -wetland areas. Facultative upland (FACU): species that usually occur in non -wetland areas (estimated probability 67 to 99%), but are occasionally found in wetlands. Upland (UPL): species that almost always occur in non -wetland areas under normal conditions (estimated probability >99%). A (+) or (-) following the WIS signifies a greater or lesser likelihood, respectively, of the species being found in wetland conditions. Adolfson Associates, Inc. Page 15 January 2006 Amon Property Wetland Delineation FIGURES AND PHOTOGRAPHS Adolfson Associates, Inc. Page 16 January 2006 KING COUNTY A o 0 .. File name: Fig01 vidnity.al Created/last edited by: JAB Date last updated: 10/03705 Reference: 25132 N NOT TO SCALE Map data ere the property of the sources listed below. Inaccuracies may exist, end Adolfson Associates, Inc. implies no warranties or guarantees regarding any aspect of data depiction. SOURCE: Thomas Bros. Maps. 2004. FIGURE 1 VICINITY MAP AAMON PROPERTY WETLAND DELINEATION TUKWILLA, WASHINGTON Sauthceritor Malt E nJ Legend Project Site Wel File name. Fig2.pdf Created/last edited by: DNE Date last updated: 1/20/06 H Feet 0 000 1,200 1:14,400 Map data are the property of the sources listed below. Inaccuracies may exist, and Adolfson Associates. Inc. implies no warranties or guarantees regarding any aspect of dela depiction. SOURCE: USGS Topoquad, 1995; King County GIS, 2004 FIGURE 2 TOPOGRAPHIC MAP AAMON PROPERTY WETLAND DELINEATION TUKWILLA, WASHINGTON • Legend • Q Project Site Q NWI City Boufidary --- Streams 1(711 CirnCTa i. F F II File name. Fig3.pdf CreatedAast edited by: DNE Date lest updated- l/20x08 N =Feet D 900 1,200 1:14,400 Map data are the property of the sources listed below. Inaccuracies may exist, and Adolfson Associates, Inc. implies no warranties or guarantees regarding any aspect of date dipiction. SOURCE: WDFW PHS, 2005; NWI, 1988; King County GIS, 2004 FIGURE 3 NATIONAL WETLANDS INVENTORY MAP AAMON PROPERTY WETLAND DELINEATION TUKWILLA, WASHINGTON S152S1 3 9 S152St 4, 4 i S160St S156St m N S,46,79 ^ _3"�____ SR A 6,1,9 o3 O S152St E cc 0 v S152PI 1405 Ramp ,AoS Fr, d 47. 414 r rte• =;.. .mmm. • 0 S 161 St %44, a. E cc PROJECT SITE S 164 rr m a rn a • 07 (n N S 163 PI Slade Way Legend co Type 3 Wetlands (City Owned Parcels) `'• Type 3 Wetlands (Privately Owned Parcels) inti _ Type 2 Wetlands (City Owned Parcels) Type 2 Wetlands (Privately Owned Parcels) ®Type 1 Wetlands Parks City Owned Parcels Basins Streams Buffer Type 3 (50') Buffer Type 2 (80') Parcels — Streets I 1 (n E S166St N Fib name: Fige4_buftermap.ai Created4ant edited by: JAB Date last updated: 01/20/06 Reference: 25132.1 NOT TO SCALE Map data are the property of the sources bled below. Inaccuracies may exist, and Addison Associates, Inc. Implies no warranties or guarantees regarding any aspect of data depiction. SOURCE: City of Tukwila, July 2004. FIGURE 4 CITY OF TUKWILA WETLANDS/WATER COURSE AND BUFFER MAP AARON PROPERTY WETLAND DELINEATION TUKWILA, WASHINGTON a 2 Legend - Streams Project Site NRCS SSURGO Soils Hydric Non -Hydric Soil Key AkF, ALDERWOOD AND KITSAP SOILS. VERY STEEP AmC, ARENTS, ALDERWOOD MATERIAL, 6 TO 15 PERCENT SLOPES Ng, NEWBERG SILT LOAM Ur, URBAN LAND W, Water Wo, WOODINVILLE SILT LOAM File name: Fig5.pdf Creetedfast edited by DNE Date lest updated: 1/20/06 Feel 600 1.200 1:14,400 Map data aro the property of the sources listed below Inaccuracies may exist, and Adolfson Associates, Inc. implies no warranties or guarantees regarding any aspect of dna dipictlon SOURCE: NRCS SSURGO Soils, 2003; King County GIS, 2004 FIGURE 5 SOILS MAP AAIIAON PROPERTY WETLAND DELINEATION TUKWILLA, WASHINGTON Photo 1. Amon property facing northwest from the intersection of South 160 Street and 53rd Avenue South (southeast corner of lot). (October 4, 2005) Photo 2. Wetland A. (October 4, 2005) Photo 3. Wetland B. (October 4, 2005) Photo 4. Wetland B soils. (October 4, 2005) Photo 5. Wetland C. (October 4, 2005) Photo 6. Wetland B, culvert drains spring fed water through the wetland towards the east. (October 4, 2005) Photo 7. This is the east end of Wetland C. Note the spring fed water drainage flowing on top of the compacted soils. Soil compaction is due to the City of Seattle underground water pipeline. (October 4, 2005) Photo 8. Typical upland vegetation within the Amon property site. (October 4, 2005) Amon Property Wetland Delineation APPENDIX A: METHODS USED TO EVALUATE WETLAND CHARACTERISTICS Adolfson Associates, Inc. Appendix A January 2006 Amon Property Wetland Delineation Wetland Definition Wetlands are formally defined by the U.S. Army Corps of Engineers (Corps) (Federal Register 1982), the Environmental Protection Agency (EPA) (Federal Register 1988), the Washington Shoreline Management Act (SMA) of 1971 (Ecology, 1991) and the Washington State Growth Management Act (GMA) (Ecology, 1992) as ... those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas (Federal Register, 1982, 1986). In addition, the SMA and the GMA definitions add: Wetlands do not include those artificial wetlands intentionally created from non - wetland site, including, but not limited to, irrigation and drainage ditches, grass - lined swales, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape amenities, or those wetlands created after July 1, 1990 that were unintentionally created as a result of the construction of a road, street, or highway. Wetlands may include those artificially created wetlands intentionally created from non -wetland areas to mitigate the conversion of wetlands. Methods defined in the Washington State Wetlands Identification and Delineation Manual (Ecology, 1997), a manual consistent with the U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), were used to determine the presence and extent of wetlands on the subject property. Washington state and all local governments must use the state delineation manual to implement the SMA and/or the local regulations adopted pursuant to the GMA. The methodology outlined in the manual is based upon three essential characteristics of wetlands: (1) hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three characteristics must all be present in order to determine that an area is a wetland (unless problem areas or atypical situations are encountered). These characteristics are discussed below. Vegetation Plants must be specially adapted for life under saturated or anaerobic conditions to grow in wetlands. The U.S. Fish and Wildlife Service (USFWS) has determined the estimated probability of each plant species' occurrence in wetlands and has accordingly assigned a "wetland indicator status" (WIS) to each species (USFWS, 1997). Plants are categorized as obligate (OBL), facultative wetland (FACW), facultative (FAC), facultative upland (FACU), upland (UPL), not listed (NL), or no indicator status (NI). Definitions for each indicator status are listed in the Glossary. Species with an indicator status of OBL, FACW, or FAC are considered adapted for life in saturated or anaerobic soil conditions. Such species are referred to as "hydrophytic" vegetation. A (+) or (-) sign following the WIS signifies greater or lesser likelihood, respectively, of the species being found in wetland conditions. Adolfson Associates. Inc. Appendix A-1 January 2006 Amon Property Wetland Delineation Areas of relatively homogeneous vegetative composition can be characterized by "dominant" species. The indicator status of the dominant species within each vegetative stratum is used to determine if the plant community may be characterized as hydrophytic. The vegetation of an area is considered to be hydrophytic if more than 50% of the dominant species have an indicator status of OBL, FACW, or FAC. The scientific names and wetland indicator status for each plant discussed in this report are presented in Appendix B. Soils Hydric soils are indicative of wetlands. Hydric soils are defined as soils that are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part of the soil profile (Federal Register, 1994). The Natural Resources Conservation Service (NRCS), in cooperation with the National Technical Committee for Hydric Soils, has compiled lists of hydric soils (NRCS, 1995). These lists identify soil series mapped by the NRCS that meet hydric soil criteria. It is common, however, for a map unit of non -wetland (non -hydric) soil to have inclusions of hydric soil, and vice versa. Therefore, field examination of soil conditions is important to determine if hydric soil conditions exist. The NRCS has developed a guide for identifying field indicators of hydric soils (NRCS, 1998). This list of hydric soil indicators is considered to be dynamic; revisions are anticipated to occur on a regular basis as a result of ongoing studies of hydric soils. Anaerobic conditions create certain characteristics in hydric soils, collectively known as "redoximorphic features," that can be observed in the field (Vepraskas, 1999). Redoximorphic features include high organic content, accumulation of sulfidic material (rotten egg odor), greenish- or bluish -gray color (gley formation), spots or blotches of different color interspersed with the dominant or matrix color (mottling), and dark soil colors (low soil chroma) (NRCS, 1998; Vepraskas, 1999). Soil colors are described both by common color name (for example, "dark brown") and by a numerical description of their hue, value, and chroma (for example, 10YR 2/2) as identified on a Munsell soil color chart (Munsell Color, 2000). Soil color is determined from a moist soil sample. Hydrology Water must be present in order for wetlands to exist; however, it need not be present throughout the entire year. Wetland hydrology is considered to be present when there is permanent or periodic inundation or soil saturation for more than 12.5% of the growing season (typically two weeks in lowland Pacific Northwest areas). Areas that are inundated or saturated for between 5% and 12.5% of the growing season in most years may or may not be wetlands. Areas inundated or saturated for less than 5% of the growing season are non -wetlands (Ecology, 1997). Indicators of wetland hydrology include observation of ponding or soil saturation, water marks, drift lines, drainage patterns, sediment deposits, oxidized rhizospheres, water -stained leaves, and local soil survey data. Where positive indicators of wetland hydrology are observed, it is assumed that wetland hydrology occurs for a sufficient period of the growing season to meet the wetland criteria, as described by Ecology (1997). Adolfson Associates, Inc. Appendix A-2 January 2006 Amon Property Wetland Delineation APPENDIX B: COMMON AND SCIENTIFIC NAMES OF PLANTS AND THEIR WETLAND INDICATOR STATUS Adolfson Associates, Inc. Appendix 1 January 2006 Amon Property Wetland Delineation PLANT SPECIES LIST FOR THE AMON PROPERTY PROJECT, IDENTIFIED ON October 4, 2005 COMMON NAME' SCIENTIFIC NAME' WETLAND INDICATOR STATUS2' 3 x big -leaf maple Acer macrophyllum FACU Douglas fir Pseudotsuga menziesii FACU* red alder Alnus rubra FAC Douglas' spiraea Spiraea douglasii FACW English holly Ilex aquifolium NL evergreen blackberry Rubus laciniatus FACU+ hedge bindweed Convolvulus sepium (Calystegia sepium) FAC Himalayan blackberry Rubus discolor (Rubus armenicus) FACU Indian plum (osoberry) Oemleria cerasiformis FACU Japanese knotweed Polygonum cuspidatum FACU* dull Oregongrape Berberis nervosa NL creambush oceanspray Holodiscus discolor NI Pacific blackberry (dewberry) Rubus ursinus FACU salal Gaultheria shallon FACU* salmonberry Rubus spectabilis FAC+ common snowberry Symphoricarpos albus FACU thimbleberry Rubus parviflorus FAC - vine maple Acer circinatum FAC - western snowberry Symphoricarpos occidentalis NI =t e Adolfson Associates, Inc. January 2006 Appendix B-1 Amon Property Wetland Delineation COMMON NAME' SCIENTIFIC NAME' WETLAND INDICATOR STATUS2'3 American speedwell (Veronica Americana) OBL bracken fern Pteridium aquilinum FACU bull thistle Cirsium vulgare FACU cleavers Galium aparine FACU climbing nightshade (bittersweet) Solanum dulcamara FAC+ colonial bentgrass Agrostis tenuis (Agrostis capillaris) FAC common plantain Plantago major FAC Cooley's hedge -nettle Stachys cooleyae FACW creeping buttercup Ranunculus repens FACW curly dock Rumex crispus FAC+ common dandelion Taraxacum officinale FACU common scouring -rush Equisetum hyemale FACW dock (Rumex sp.) UPL-NL English ivy Hedera helix NL English plantain Plantago lanceolata FACU+ field horsetail Equisetum arvense FAC fireweed Epilobium angustifolium FACU+ foxglove Digitalis purpurea FACU* foxtail timothy (heleochloa) Heleochloa alopecuroides (Crypsis alopecuroides) OBL* giant horsetail Equisetum telmateia FACW ground ivy Glecoma hederacea (Glechoma hederacea) FACU+ hairy cats -ear Hypochaeris radicata FACU hare's -foot Trifolium arvense NL herb Robert Geranium robertanium NL Adolfson Associates, Inc. January 2006 Appendix B-2 Amon Property Wetland Delineation COMMON NAME' SCIENTIFIC NAME' WETLAND INDICATOR STATUS 2' 3 inch -high rush Juncus uncialis FACW+ lady fern Athyrium filix-femina FAC+ meadow foxtail Alopecurus pratensis FACW orchard -grass Dactylis glomerata FACU Oregon bentgrass Agrostis oregonensis FAC oxeye -daisy Chrysanthemum leucanthemum (Leucanthemum vulgare) NI Pacific bedstraw Galium cymosum (Galium trifidum) FACW pathfinder Adenocaulon bicolor NL pearly everlasting Anaphalis margaritacea NL perennial ryegrass Lolium perenne FAC* pig -a -back -plant Tolmiea menziesii FAC pineapple weed Matricaria matricarioides (Matricaria discoidea) FACU quackgrass Agropyron repens FAC - red clover Trifolium pratense FACU red fescue Festuca rubra FAC+ redtop Agrostis alba (Agrostis stolonifera) FACW* reed canarygrass Phalaris arundinacea FACW Richardson's crane's bill Geranium richardsonii FAC - rush (Scirpus sp) NI- OBL Siberian spring beauty Montia sibirica (Claytonia sibirica) FAC- skunk cabbage Lysichitum americanum (Lysichiton americanus) OBL small bedstraw Galium trifidum FACW+ soft rush Juncus effusus FACW Adolfson Associates. Inc. January 2006 Appendix B-3 Amon Property Wetland Delineation COMMON NAME' SCIENTIFIC NAME' WETLAND INDICATOR STATUS2'3 Solomon -plume, common groundsel Senecio vulgaris FACU spreading bentgrass Agrostis stolonifera FAC+ stinging nettle Urtica dioica FAC+ sword fern Polystichum munitum FACU tall fescue Festuca arundinacea (Lolium arundinaceum) FAC- western St. John's wort Hypericum formosum (Hypericum scouleri ssp. scouleri) NL western starflower Trientalis latifolia (Trientalis borealis ssp. latifolia) FAC- western touch-me-not Impatiens noli-tangere FACW white clover Trifolium repens FAC - Common names are primarily from Flora of the Pacific Northwest (Hitchcock and Cronquist, 1973). Scientific names are as listed in Hitchcock and Cronquist (1973). Scientific names change over time as botanists reevaluate plant species. The scientific name currently listed in the "Washington Flora Project" database (http://flora.ilangainc.com) is given in parentheses if it is different from that listed in Hitchcock and Cronquist (1973). 2 Key to Wetland Indicator Status codes — Northwest Region (Source: USFWS, 1997): OBL Obligate: species that almost always occur wetlands under natural conditions (est. probability >99%). FACW Facultative wetland : species that usually occur in wetlands (est. probability 67 to 99%), but are occasionally found in non -wetlands. FAC Facultative: Species that are equally likely to occur in wetlands or non -wetlands (est. probability 34 to 66%). FACU Facultative upland: species that usually occur in non -wetlands (est. probability 67 to 99%), but are occasionally found in wetlands. UPL Upland: species that almost always occur in non -wetlands under normal conditions (est. probability >99%). NL Not listed: species that are not listed by USFWS (1997) and are presumed to be upland species. NI No indicator: species for which insufficient information is available to determine status, or which were not evaluated by USFWS. + indicates a species that is more frequently found in wetlands Adolfson Associates. Inc. Appendix B-4 January 2006 Amon Property Wetland Delineation - indicates a species that is less frequently found in wetlands * identifies a tentative assignment based upon either limited information or conflicting reviews 3 Where a range of Wetland Indicator Status ratings are given for a genus, the range reflects the species for which ratings are provided in the USFWS (1997) list. Some species within the genus may be NI or NL. Adoljson Associates, Inc. Appendix 8-5 January 2006 Amon Property Wetland Delineation APPENDIX C: DATA SHEETS Adolfson Associates, Inc. Appendix C January 2006 DATA FORM 1 (Revised) 4 Routine Wetland Determination --(WA State Wetland Delineation Manual or 1987 Corps Wetland Delineation Manuan Project/Site: 1Qatndyl r ltp - • . • ' Applicant/owner. 570 d fpr. Aa i -, /� ` • - Investigator(s): ,1_ i la�rhr i I 1...9ml ce.n .. Date: l D - 9- 05 Stat• t.Qiit !V Slf/R: , Do Normal Circumstances exist on the site? 1 ' ` ' Is the site significantly disturbed (atypical situation)? yes Is the area a potential Problem Area? .yes no • Explanation of atypical or problem area: , Commmziry ID: � r( A Transect ID: Plot ID: .Dp - VEGETATION (For strata, indicate T = tree; S = shrub; H = herb; V = vine) Dominant Plant Species Stratum % cover Indicator Dominant Plant Species Stratum % cover Indicator S (.k4tsOAD�rct \A 5.0 TACO `R$r 5OD r l 14 . .-3 0 F -C f - o iz, o.ls ilnitome s 5 15 F tittA. HYDROPHYTIC VEGETATION INDICATORS % of dominano•OBL, FACW, & FAC • Check all indicators that apply & explain below: Visual observation of plant species growing in-. Physiological/reproductive adaptations areas of prolonged inundation/saturation Wetland plant database Morphological adaptations Personal knowledge of regional plant communities ' Technical Literature Other (explain) Hydrophyde•Vegetadon present? Rationale for decision/Remarks: VeCte no ,h04!s ; , vi k b3 Ativvpa etes. HYDROLOGY ; ' - '" _ Is it the growing season? ; yes .: ao Water Marks: yes( on Sediment Deposits: yes Based on: • sort temp (record tern - ) Drift Lines: yesx • :Drainage Patterns: other (explain) • oto yes no Dept of inundation: MO f tektilk inches Oxidized Root (live roots) :Local Soil Survey: t�4 Channels <I2 in. yes o yes no Depth to free water in pit 1" inches �6 FAC Neutral: y no Water -stained Leaves Depth to saturated soil: Not orpiwt, inches - yes no ) Check all that apply & explain Below: Stream, Lake or gage data: Other (explain): Aerial photographs: Other Wetland hydrology present? yes no - Rationale for decision/Remarks:. . ' - gale dye regii� 043.144'0 431 4 'a b"^ tit e art. t • , no �o1lS. i;;�-Acif 1 a i f t)1 11 b5 61,0ftwc eivotittelct 5efiLOyi. r$'ung) ‘1-- rs "Assam- dGiai- •iy! is 'caws at per` SOILS Map Unit Name {Series & Phase) Arm 1416Immo°, Taxonomy (subgroup) Profile Description Drainage Class triodarrkie Lc1 fr ngcO Field observations confirm Yes No mapped type? Depth .(inches) Horizon Matrix color (Munsell moist). Mottle colors (Munsell moist). Mottle abimdance size & contrast Texture, concretions, structure, etc..R Drawing of soil rofrle (match description) (c)-?) A • tolgiii 5a loani, . ( f 9; Y 1/z royg. q/ oal rtovt .i d6ftsli. n6 I- 1Oarll solt Hydric Soil Indicators: Histosol (check all that apply). . Odor Moisture Regime • Conditions - or Low-Cbroma (=1) matrix x Matrix chroma 5 2 with mottles : ..,) j : ) Concretions " Content in Surface Layer of Sandy Soils Streaking in Sandy Soils - National/Local Hydric Soils List in remaj±s) Histie Epipedori Mg orFe Sulfidic High Organic Aquic Organic Reducing Listed on Gleyed Other (explain Hydric soils present?? yes no Rationale for decision/Remarks. tlgre6 0 /t di 50;1.5 60 fill Atogia Wetland Determination (circle) _ • no • no Is the sampling point la 10 no Yes no - ' within a wetland? Hydrophytic vegetation present? Hydric soils present? Wetland hydrology present? Rationale/R- emarks• V aA)lliiV (:S • h•L�Ei fh Fi 50 D arm hq 11 V 48rolob nstd�' at daresrr + flesettetcF .tikoi G,� (fe�tlett t.�. b LIVIA Sols-011.ctn aAL`-'h utd c. NOTES: •‘-50115 (NA 3t1 SoffatC `fir._ ()al SLh vr+ ,u I -2.4 . �,j also 021,11- - Ida sunb Alias ape( b iii D!h l) /peo kat bits ctitw i m de f vess;14- AA ask Revised 4/97 DATA FORM 1 (Revised) Routine Wetland Determination . (WA State Wetland Delineation Manual or 1987 Corps Wetland Delineation Manual) Project/Site: A..Qm„i e"Gr �- Applicant/owner: .)OtJ 3-454, Aa jVtaf � Investigator(s): Z. ! Rbr1 `1 !r 6r� aA Date: )Q— County: State: SIT/R.:,. (1' 0 45 . i� t"•)`AS k1 . Do Normal Circumstances exist on the site? ( yes . ' Is the site significantly disturbed (atypical situation)? yes Is the area a potential Problem Area? .yes no Explanation of atypical orproblem•area ' Community ID: v )4/1 Transect ID: ( . Plot ID: DP�Z 1, VEGETATION (For strata, indicate T = tree; S = shrub; H = herb; V = vine) , Dominant Plant Species Stratum % cover Indicator Dominant Plant Species Stratum % cover Indicator Ho'tPrIt )(10,1t.y C5 1f20 ," N room ustium..co Li 0 FII(M1 - A�e� ,��,�t�,t, T 50 F C 0e116 c t % 5 .f FISC,U golks Onion.a P.us s 15 .Fli .t • 19f1,'A .6:14110A4 riim.lvih 5 ! FACu • . HY1�tOPHYTIC VEGETATION INDICATORS % of dominangs•OBL, FACW, & FAC 0 °A Check all indicators that apply & explain below:' Visual observation of plant species growing in . Physiological/reproductive adaptations areas of prolongedinundation/saturation Wetland plant database Morphological adaptations Personal knowledge of regional plant commumities Technical Literature Other (explain) Hydrophytie vegetation present? yes (no' Rationale for . • /va h LSP P,�2 . Vose4lI- v ityk., HYDROLOGY d _ Is it the growing season? yes ` no Water Marks: yes no on Sediment Deposits: yes al Based on: soil temp (record t-4.. p ) Drift Lines:' yrs Drainage Patterns: yes no other ( lain) , 0 '; .; Dept. of inundation: t 1 c _ inches Oxidized Root (live too Local Soil Survey. yes no f Channels <12 in. yes n Depth to free water in pit 104 -inches FAC Neutral: yes no Water -stained Leaves yes no Depth to saturated soil: p rhes : Check all that apply & explain bell Stream, Lake or gage data: Other (explain): Aerial photographs: Other. • Wetland hydrology present? yes no Rationale for decision/Remarks: • Ain ) ail fibJD44 in -die. alma Pt f..wt' SOILS Map Unit Name Arepf- L. •(Series & Phase) Taxonomy (subgroup) Drainage Class f - Field observations confine Yes No mapped type? Profile Description • Depth (inches) Horizon : ' -' Matrix color (Munsell moist) Mottle colors (Munsell moist). Mottle abundance size & contrast - Texture, concretions, structure; etc. Dra"vving Of soil • Profile (match description) Di -A Qt5Y k . oobAletann . 1.11D B 5 lh to Yi %0 kw mid anis(s loco iY) • Hydric Soil Indicators: Histosol (check all that apply) Odor Moisture Regime Conditions . - or Low-Chroma (=1) matrix .• Matrix chrome S 2 with mottles Concretions Content in Surface Layer of Sandy Soils Streaking in Sandy 'Soils National/Local Hydric Soils List 4. lain in remarks) - Histic. Epipedon _ .Mg or Fe Sulfidic • • High Organic Aquic Organic Reducing Listed on Gleyed Other Hydric soils present? yes ap Rationale for decision/Remarks• hiAll 610014 • fit") 'MOtftp �IVYStW PO� . (ti. Itll ON = 1 •' Wetland Determination (circle) yes • o • yes Is the sampling point yes no within a wetland? yes no Hydrophytic vegetation present? Hydric soils present? Wetland hydrology present? Rationale/Remarks: • !� 5 Gt }evs art AO• • NOTES: Revised 4/97 DATA FORM 1 (Revised) Routine Wetland Determination (WA State Wetland Delineation Manual or 1987 Corps Wetland DeIineatioe Munnnll Project/Site: illiorri 0,, Applicant/owner. ZThC A11 Investigator(s): a"iv% • 2 3 _ Date: / a/ lip c". County: 'kiNG . State: hi/2 . S/T/R; pfzer, � 25% -01_e71/ l Z Do Normal Circumstances exist on the site? 4s' no Is the site significantly disturbed (atypical situation)? yes c Is the area a potential Problem Area? yes gi. Explanation of atypical or problem area: Community ID: Ye uytnizt.ilo g Transect ID: Plot ID: pp, .: VEGETATION (For strata, indicate T = tree; S = shrub; H = herb; V = vine) Stratum % cover Indicator Dominant Plant Species Stratum % cover.. Indicator Dominant Plant Species s id�;u C/v , Ppit'1) i�er r�acronild ,T. ZO f4Ctl mt,„, 'fix . tna_ .. /1 20 x mew Lys;iiiLnr; 1-1 15 0SL .7d,774:;,. fazn2;bs.e. V 5 Fik, r,-MIL/H r 14 )D. S-1.ci• w,l,. ja.d // 3o x focd11 `J //dd.-A. •hal,le // . y, - NL . Reis . eikh s • 3d , Poe -7' . . .. HYDROPIC VEGETATION of dominanSs:OBL, FACW, Check all indicators that apply Visual observation of plant species areas of prolonged inundation/saturation Morphological adaptations Technical Literature Th1DICATORS• Q� & FAC CJS Q Physiological/reproductive _ Wetlagd p L �'+ I v�'1 notch I A 0t %i1 ec iop4 V i f... GlolivN ,,, adaptations plant database knowledge of regional plant (explain) '�(,2.0�. t�! t'CS i taYl o) . - communities : 1 QI"Q�i 1 f & explain growing below: in K Personal Other Hydrophytic vegetation present? L7' no Rationale for decision/Remarks: . �ia.s cc•Pia•l unite /)7 *rte Sv? te r �a.-ar P' . f 9c�r/ O.s'L .52 7 ¢/dknq 4'o Lr i� iYi�i_ndm /4 -t . %n .502&Olt,•, HYDROLOGY yes. (record temp no ) Is it the growing season? Based on: soli temp Water Merits: yes 0 on Sediment Deposits: yes . Drift Lines: yes ti Drainage Patterns: no 12 7 ' other (explain) X. Dept of inundation: Depth to free water in pit Depth to saturated soil: — inches Oxidized Root (live roots)6/1 , Channels <12 in. ®, no Local Sot? Survey. yes no 1L inches e) inches FAC Neutral: cysf no 3:o • Water -stained Leaves yes Check all that apply & explain Stream, Lake or gage data: Aerial photographs: below: Other (explain): Other: Wetland hydrology present? no Rfa:ple for r<cisi5oMi 71 fGr�G , fLz Nr /resee / Cell � �GLrQQ S' S'�it.vu g wit/dam 46t -4y , .� ; ;-. , ..:y,.. -, r'-- SOILS Map Unit Name -(Series & Phase) Taxonomy (subgroup) remit fIc1O,vLtbc 1/4 Drainage Class GjPJ .( d,b,,eC Field observations confirm Yes No mapped type? Profile Description . Depth (inches) Horizon Matrix color (Munsell moist) Mottle colors (Munsell moist) Mottle. abundance size & contrast • Texture, concretions, structure, etc; Drdvs►ing of soil . profile (match description) 0 ' 10 • )0\ig iii; ------- .� • -_. ID -16 a.5i / 1011k `� " ut Wm cj 5•� i 1ani Hydric Soil Indicators: Histosol (check all that apply) Epipedod . - Odor Moisture Regime_ Conditions or Low (al) matrix i< •Matrix chrome 5 2 with mottles Concretions Content in Surface Layer of Sandy Saris Streaking in Sandy'Soils National/Local Hydric Soils List in renra:rks) Histic Mg or Fe Y Sulfidic Hiigh Organic Aquic Organic Reducing 7--- Gleyed Listed on Other (explain Hydric soils present? yes no Rationale for decisio dIlloYtotik. t.,-)1 P14110 , , s sigh d et dV' . . • . Wetland Determination (circle) yes no Is the sampling point no within a wetland? Hydrophytic vegetation present? Hydric soils present?es Wetland hydrology present? no drib no Radonale/Remarks:• L 3 fa-ran/deo k ti (- . A/!� P• NOTES: dol 5 motSv lOi • ` Ji rat a sod; extsr /14tlt.Q 4x14481 bay nov444,t @('cu 5 ►ws S IS e �" r� lo' Revised 4/97 DATA FORM 1 (Revised) Routine Wetland Determination (WA State Wetland Delineation Manual or 1987 Corps Wetland Delineation Mannal) • Project/Site: ({arnm t1 • Applicant/owner: St 114 mmn • Investigator(s): illtW4\t 4 Date: 1 b (-1.-- Q5- County: K I. ST R: I�Jas�t��q` Do Normal Circumstances exist on the site? yes , Is the site significantly disturbed (atypical situation)? yes Is the area a potential Problem Area? .yes Explanation of atypical or problem area: Community ID: Transco:.ti. Transect ID: r Plot ID: ��5 VEGETATION (For strata, indicate T = tree; S = shrub; H = herb; V = vine) SStratum9 covervIndicator Dominant Plant Species Stratum % cover Indicator Dominant Plant Species Phaf6Or,S (40(1 netae /4 . 10 V 1 Mb.) ?ONO 5f 1) - - P 7 --t-ri-77 • fill105 roh rG T ib Fi\ i, • • • HYDROPHYTIC VEGETATION of dominants.OBL, FACW, Check all indicators that apply Visual observation of plant species 1 areas of prolonged inundation/saturation Morphological adaptations Technical Literature INDICATORS & FAC D Physiological/reproductive Wetland adaptations • plant database knowledge of regional plant communities (explain) & explain growing below: in Personal Other Hydropbytic vegetation present? Rationale for decision/Remarks: Ont "nal .e 72 no • • X11/. HYDROLOGY yes, (record temp no ) Is it the growing season? Based on: soli temp Water Marks: yes (..1....D on Sediment Deposits: yes no •�. Drift Lines: yes iiii ) Drainage Patterns: yes to Op -a- other (explain) Dept of inundation: Depth to free water in pit Depth to saturated soil: -- inches Oxidized Root (live toots), Channels <12 in. el. inol Local Sot? Survey. yes no >11 inches /inches FAC Neutral: y o Water -stained Leaves yes no `cam Check all that apply & explain Stream, Lake or gage data: Aerial photographs: below: Other. Other (explain): Wetland hydrology present? yes no Ratio�e for deOsio emarks• / / /(01// No for �% o n5 •l�S,40- . A6e4 • , eek/' Tv ct /a 1 � / �d�� �� Y���� ��� SOILS Map Unit Name {Series & Phase) Taxonomy (subgroup) ill Drainage Class dblfi" P. Field observations confimnt Yes No mapped type? - Profe.Description r 1 . Depth . (inches) Horizon., • Matrix color (Munsell : moist) Mottle colors (Munsell moist) Mottle abundance size & contrast Texture, concretions, structure, etc. Drawing of soil profile (match description) 0 ,I0 .f- • Ne -34,- !- — 2,7-1)-y„;,,,Y,_ • /0.1b S ”y Y/” _ • - SeL.dy l00„-.___ • Hydric Soil Indicators: Histosol (check all that apply) Epipedoti Odor Moisture Regime Conditions or Low-Cbroma (=I) matrix Matrix chroma 5 2 with mottles Concretions Content in Surface Layer of Sandy Soils Streaking in Sandy Soils National/Local Hydric Soils List in remathcs) Histic Mg or Fe Sulfidic High Organic Aquic Organic Reducing Listed on Gleyed Other (explain Hydric soils present? yes , . Rationale for decision/Remarks: Xo d cG78rs pasat . Wetland Determination (circle) . ® no yes no Is the sampling point yes o within a wetland? Hydrophytic vegetation present? Hydric soils present? Wetland hydrology present? Rationale/Remarks: Un! y /1,1 1 e- (cid, 1‘10.— Ili 61 . NOTES: DP — 5 %s /44,../z1 c2 111/ C. G' &a r74/_/./? Ach.:5 5-/ /l /7P 7 , SSo . C S CIG 17 f Revised 4/97 Ms. Minnie Dhaliwal, Senior Planner City of Tukwila Planning Department 6200 Southcenter Boulevard Tukwila, WA 98188 CIVIL ENGINEERING. LAND PLANNING, SURVEYING, ENVIRONMENTAL SERVICES December 14, 2006 COURIER DELIVERY to(a - bgl RECEIVED DEC ?00'15 COMMUNITY DEVELOPMENT RE: Special Permission Director for Wetland and Geotech Review LaTourelle Subdivision King County Assessor's Tax Parcel Nos. 537920-0005 and 537920-0006 Our Job No. 12650 Dear Ms. Dhaliwal: We are submitting a Special Permission Director application for review of the wetland and geotech reports associated with the La Tourelle preliminary plat. A full preliminary plat application will follow at a later date. We recognize that the City will not issue approval of the preliminary plat until it has reviewed the SEPA checklist for this project and is not held to a 120 -day review upon receipt of this application. We also recognize that this application does not allow the proposed plat to be vested to current Tukwila Municipal Code standards. It is our understanding that the enclosed application is sufficient for the City to begin its peer review of the wetland delineation and geotech report. We request that review of the enclosed be expedited and authorize any overtime that may be billed as a result. Thank you. Respectfully, Thomas A. Barghausen, P.F.. President ADD/pj 12650c.003.doc enc: One (1) copy of the Special Permission Director application Four (4) copies of the Wetland Delineation prepared by Adolfsen Associates, Inc. Four (4) copies of the Geotechnical Report prepared by Otto Rosenau and Associates, Inc. One (1) check in the amount of $230.00 cc: Mr. Jawaid Amon Ms. Ivana Halvorsen, Barghausen Consulting Engineers, Inc. Mr. Raymond van der Roest, Barghausen Consulting Engineers, Inc. Ms. Alexia D. Dorsch, Barghausen Consulting Engineers, Inc. 18215 72ND AVENUE SOUTH KENT, WA 98032 (425) 251-6222 (425) 251-8782 FAX BRANCH OFFICES • OLYMPIA, WA • TACOMA, WA • SACRAMENTO, CA 4' TEMECULA, CA www.barghausen.com CITY OF TUKWILA Department of Community Development 6300 Southcenter Boulevard, Tukwila, WA 98188 Telephone: (206) 431-3670 FAX (206) 431-3665 E-mail: tukplan(a�ci.tukwila.wa.us RECEIVED DI,,1: ) CMMUTY DEVELOPS NT AFFIDAVIT OF OWNERSHIP AND HOLD HARMLESS PERMISSION TO ENTER PROPERTY STATE OF WASHINGTON ss COUNTY OF KING The undersigned being duly sworn and upon oath states as follows: 1. I am the current owner of the property which is the subject of this application. 2. All statements contained in the applications have been prepared by me or my agents and are true and correct to the best of my knowledge. 3. The application is being submitted with my knowledge and consent. 4. Owner grants the City, its employees, agents, engineers, contractors or other representatives the right to enter upon Owner's real property, located at South 160th Street and 53rd Avenue South for the purpose of application review, for the limited time necessary to complete that purpose. 5. Owner agrees to hold the City harmless for any loss or damage to persons or property occurring on the private property during the City's entry upon the property, unless the loss or damage is the result of the sole negligence of the City. 6. Non -responsiveness to a City information request for ninety (90) or more days, shall be cause to cancel the application(s) without refund of fees. (� (� EXECUTED at (� (city), `– (state), on 1 C Q k (-- , 20\s Print Name Jawa i d Amon Address 16424 – 53rd Place South Phone Number (206) 856-4255 Signature On this day personally appeared before me -1-0, 400 \ to me known to be the individual who executed the foregoing instrument and acknowledged that he/she signed the same as hislbec voluntary act and deed for the uses and purposes mentioned therein. SUBSCRIBED AND SW(Y ME ON THIS 1 DAY OF CO I t \) Qr , 20°LQ Q TA4, LIC , 1 118 larrI �^ �� u O R.174. r? �'QR LIC in d for the State of Washington N AU - 0 5� residing at Q� B\c, = °— 4010 II > i., 09, 4,4 , My Commission expires on `¢�� \wike P:Planning Forms \Applications\SPDirector-12-06.doc December 4, 2006 12680.00) .pdf CITY OF TUKWILA Department of Community Development 6300 Southcenter Boulevard, Tukwila, WA 98188 Telephone: (206) 431-3670 FAX (206) 431-3665 E-mail: tukplan@ci.tukwila.wa.us RECEIVED IR 1 7006SPECIAL Dal% 'AV PERMISSION DIRECTOR APPLICATION FOR STAFF USE ONLY Permits Plus Type: P -SP Planner: File Number: L 06 — o S 9 Application Complete (Date: ) Project File Number: Application Incomplete (Date: ) Other File Numbers: NAME OF PROJECT/DEVELOPMENT: La Tourelle Preliminary Plat LOCATION OF PROJECT/DEVELOPMENT: Give street address or, if vacant, indicate lot(s), block and subdivision, access street, and nearest intersection. South 160th Street and 53rd Avenue South LIST ALL TAX LOT NUMBERS (this information may be found on your tax statement). 537920-0005, -0006 DEVELOPMENT COORDINATOR : The individual who: • has decision making authority on behalf of the owner/applicant in meetings with City staff, • has full responsibility for identifying and satisfying all relevant and sometimes overlapping development standards, and • is the primary contact with the City to whom all notices and reports will be sent. Name: Tom Barghausen, Barghausen Consulting Engineers, Inc. Address: 18215 - 72nd Avenue South, Ke t, WA 98032 Phone: (425) 251-6222 E-mail: tbarghausen@ Signature: FAX: (425) 251-8782 rgha; e -om ' P:\Planning Forms \Applications\SPDirector-12-06.doc Date: / 4 '3 /oG December 4, 2006 12680.001.pdf Page 1 of 1 1[ , N CItyG]:S 150ft Copyright 02006 All Rights Reserved. The information contained herein is the proprietary property of the contributor supplied under license and may not be approved except as licensed by Digital Map Products. http://maps.digitalmapcentral.com/production/CityGIS/v07_01_036/indexA.html 12/18/2007 P-40' 0 20 40 80 PRET JMNARY SHORT PLAT MAP FOR LA TOURELLE A PORTION OF THE NW 1/4 OF SECTION 26, TOWNSHIP 23 N., RANGE 4 E, WM TUKWILA, WASHINGTON L 4 ..r CF• '?"rC' r_ r"� 0 \>�q - SOII�i 159TH SiRE_ET J •• A.,' rc)Xs - e., - .Y ` J �` yr YJv DESCRIPTION "`\\\\\ \\\\'\\\\ \ \\ �) \ \�\\\\\ \ \ \N N \ \ \\\ \� Q•�( \ %�\ 0 0) 'Yc.J <'\` (\ c"-, ,(,vim 1 BEGINNING AT A POINT ON THE NORM LINE OF SECTION 26. TOWNSHIP 23 NORTH, RANGE 4 EAST. WILLAMETTE MERIDIAN, N KING COUNTY, WASHINGTON, A DISTANT SOUTH 89'31'13' EAST 23.86 FEET FROM THE NOR1NWEST CORNER OF SAID SECTION: THENCE CONTINUING SOUTH 89.31'lF FAST 601.67 FEET TO THE WEST UNE OF 5380 AVENUE SOIRHI; THENCE SOUTH 2110'20' EASE 262.37 FEET: 11ENCE SOUTH 3'24'20' EAST 16295 FEET TO T140 NORTHEASTERLY MARGIN OF 50U114 160114 THENCE ALONG THE SAID NORTHEASTERLY MARGIN NORTH 7E07'40' WEST 109.97 FEET: THENCE NORTH 70.55'05' WEST 305.05 FEET: THENCE NORTH 40'2510' WEST 170.49 FEET; THENCE NORTH 52'20'00' WEST 254.38 FEET TO THE POINT OF BEGINNING: (ALSO KNOWN A5 A PORTION OF IDT 1. BLOCK 1, MC MICKEN HEIGHTS (=SION N0. 1. ACCORDING TO TIE UNRECORDED PUT THEREOF): EXCEPT THAT PORTION BEGINNING AT THE SOUTHEAST CORNER OF THE ABOVE DESCRIBED TRACT: THENCE NORTH ALONG THE EAST UNE OF SAID DESCRIBED TRACT 104.30 FEET; THENCE SOUTHWESTERLY ON A SOUGHT UNE 100 FEET. MORE OR LESS. TO A PONT ON THE SOUTHERLY UNE OF SAID DESCRIBED TRACT WHICH IS 40 FEET WESTERLY OF THE POINT OF BEGNNNG THENCE SOUTHEASTERLY ALONG THE SOUTHERLY UNE OF SAID DESCRIBED TRACT 40 FEET TO THE PONT OF BEGINN140: EXCEPT THAT PORTON OF THE NORIPNEST QUARTER OF SECTION 26. TOWNSHIP 23 NORM. RANGE 4 EAST. WAIL, N KNc COUNTY, WAs16/1G108. DESCRIBED AS FOLLOWS: COMMENCING AT THE SOUTHEAST CORNER OF PROPERTY DESCRIBED IN A DELA DATED FEBRUARY 24, 1953, AND RECORDED WIDER RECORDING NUMBER 4317609: THENCE 'NORTH 76.0740" WEST ALONG THE PORT/EASTERLY RIGHT -0F -WAY UNE OF SOUTH 110TH suet( A DISTANCE OF 10997 FEET: THENCE NORTH 70'55.05' WEST HONG SAID RIGHT-OF-WAY UNE A DISTANCE OF 216.50 FEET TO 114E TRUE POINT OF BEGINNING THENCE CONTINUING NORM 70'55.05' WEST' AIDNO.SAID RIGHT-OF-WAY UNE A DISTANCE OF 88.55 FEET: THENCE NORM 4025.10' WEST ALONG SMD RIGHT-OF-WAY UNE A DISTANCE OF 137.58 FEET; THENCE SOUTH 4721'59' FAST. 60.55 FEET TO A POM ON A CURVE THROUGH. WHICH A RADWL UNE OF SAO CURVE RENTS SOUTH 43.10.11' WEST FROM 114E RADIUS PONT: 1140400 SOUTHEASTERLY ALONG SAID CURVE TO THE LEFT HAVING A RADIUS OF 520.00 FEET THROUGH A CENTRAL ANGLE OF 14'40'09' MID All ARC INSTANCE OF 158.74 FEET TO THE TRUE POINT OF 8Efi1NNG LOT AREA TABLE LOT / AREA (SF.) LOT 1 AREA (S.F.) 1 6,627 5 6,599 2 6,511 6 6,505 3 6.500 7 7.359 4 6,500 6 10.656 TOTAL IDT AREA 57,257 SF 1.31 AC. MIERAfE IDT AREA 7,157 SF • `J\ J ("C; TRACT TABLE TRACT USE AREA (5F.) 999 OPEN SPACE 103.531 TOEM. AREA 103.531 SF 2.38 AC 1 MSA OF CE131.000 SU0ERY 4C.) VICINITY MAP 619 Rte NOTES 1. TAX /: 537920-0005, -0006 2.. SITE AREA 160.896 S.F. (3.69 PC) 7. EXISTING 115E SINGLE FAMILY RESID0N1Ml (VACANT) 4. PROPOSED use 9-131 SINGLE FAMILY RFS10O411N1 s. E10SRNG ZONING: IOW DE1611Y RESIDENTIAL (LDR) 6. PROPOSED z0I6NG: IOW DENSITY RE90ENf*1 Oa) 7. EXISTING COMPRDIFNSNE PLAN DESlGNA1101t LOW DENSITY RESIDENTIAL (IDR) 6. PROPOSED COMPREHE/6NE. PUN OESIGNAION: LOW DENSITY RESIDENTIAL (LDR) 9. REQUIRED M91. LOT WIDTH: 50 FEET 10. PROPOSED 1101 IDT WIDTH: 50 FEET 11. REQUIRED 11H. LOT AREA: 6,500 5F 12. PROJECT DENSITY: 2.17 DU/ACRE 13. REQUIRED MIN. SETBACKS: FRONT: 20 FEET INTERIOR: 5 FEET REAL& 10 FEET \ � > /\\ 14. MAXBASE HEIGHT OF BURONGS 30 FEET 15. MAX LOT COVERAGE 35 PERCENT 16. STORM DRAINAGE FACILITES TO BE PRIVATELY OWNED AND MAINTAINED BY HOME OWNERS A550CIAn0M. 17. SOURCE OF 9019I1AR1': MEAD GILMAN AND ASSOC., JANUARY, 2006 DATUM NAW 88 80104544 105 ORIG0IAL IBM -BRASS DISC W/PUNCH N CONC FILLED PVC PIPE OMAN 0.51' IN CASE WESTERLY OF 2 LUIS N INTERSECTION OF S 160111 ST. & 51ST AVE 5. ELEV. - 297.89' T8 - 1: 'X' ON NORTHERLY CAP 813.T OF FIRE HYDRANT ON THE HAST 510E OF S 16001 ST. ±50 FEET FAST OF CONCRETE STARS ELEV. - 242.39' 18. SOURCE OF TOPOGRAPHY. . MFM GILAN AND ASSOC-. JANUARY, 2006 UTILMES/SERVICES WATER HIGHIUNE WATER DISTRICT 23828 30111 AVE S KENT, WA 98032 (206) 824-0375 SEWER: VALLEY VIEW SEWER DISTRICT 14816 MILITARY RD S P.O. BOX 69550 SEATTLE, WA 98168 (206) 242-1527 POWER/CAS PUSET SOUND ENERGY 105 156TH AVE NE BELLEVUE WA 98005 1.0388) 321-7779 PHONE:. 00405 COMMUNICATIONS P.O. BOX 91073 SEATTLE WA 98111 1 (800) 244-1111 CABLE CONCAST 4020 A1211811 WAY NORTH AUBURN, WA 98002 1 (877) 824-2288 FIRE: 1UKWIIA FIE OEPARTL1ENT 444 ANDOVER PARK EAST TUKWDA WA 98188 (206) 575-4404. SCHOOL 16GH104E NOLO SCHOOLS 15675 ANNUM BLVD SW BUREN. WA 98168 (206) 433-2141 OWNER/DEVELOPER JAWAO (JOE) AVON 16424 53R0 RACE SOUTH 111KW0/V WA 98168 PHONE (206) 858-4255 ENGINEER/PLANNER/SURVEYOR BARG/OUSE/4 CONSULTING DIGINEIIS, NC. 18215 72ND AVE 50UTT4 (25) 251-62222 FAX (425) 251-6782 CONTACT: TOM 8,ARONUSEN/ACTIN DORSCH 1 01 01 LL EXPIRES 89712/09 1 1 0 W' v 00103 z a z � zcoNN 55 10 4003 N �NNN•. N MS 03 Stvv I§ i r E JSTEMPICIX Xrsk , z12650—pbd•y, z 12650—ptdwq, z12 N ci. N \ N \ \ 1 \ \ \ \‘ J / \--,:--------7 . ,,,,-.:•\ 12-7.-olsrps.250.52 ., 1 --- 1 -:-.......12-ZP041101E-249.61 f\ ''" --... ...,„ .....--- 7-1.. ....---- --- -.... -...,--. -- -.... '4° ...........:-.... „--. --......:;:, ----- ,:_----: ,-',•-•.',. •-/ ,:'. • ---. . •.- ••.....,N,.. •••<-..., ..9•10 __ '"- ............. N '. -.....--... N. ..., - -..„ • N N" NN „N. -...N \ N.:N. ..,..„-....."-. • .....„ N. NcN------•••'i, \ N \\ :•:-7\ NNNN \ .4p.,44c.,".. \ '••• ',II \ \ \ \ Us.4•-. PREUMINARY PLAT MAP FOR LA TOURELLE A PORTION OF THE NW 1/4 OF SECTION 26, TOWNSHIP 23 N., RANGE 4 E., W.M. TUKVVILA, WASHINGTON 5)1E-232.37 1 2.CPIE-232.57 12.CP 16.232.47 12 -CON E 1E-232.27 FULL- OF wATER 0 C8-2269 14- 12-CP(17(S)I5-212.07 . .42:1120N(7)1;.211 97 1I:, atiTHE 13"16014C(Nleig-4- 2'CONC(EX.1135.86 8-00i [M71E4.185.78 0 es_ 64 114-1 9.1 12'COrcwC T-175.21 17' E 1E-175.21 12 -CPE 1E-174.81 12-CONC(w 1E-174.81 X(SE)1E. ( 12*C6EPf.SytE • .298. • "./1 MA..290.9 1 C,11. -235.07 mIr • . -At ••• "TT-- \ \ N r • -__ \\, \ „ ye\ \ 226.Z.t.i. .s. \ \ ) • ri-!..sfT77 . \ \ 2-Z(":411,1.4799,, 4 co m.q.3-11-.. :_-_-22-tRoPTk-$72.60 . 8 r 13' 1;w 12 71)1E11.0k, 1'-30' 0 15 30 so =1"11.:. DIAN- 284 12.0104ASK- 170 15 12180746g. 70 05 i:IP:(61M111:1;t:50 i 74.26_ :".."CCNC(W)IE, 172 90 221:›9 N [1E1211.29 \ • VF -2 6 CPEP(14691(- 74.09 \ 2-CONC,(NWPE 172.66 c<1. olm-2 6..\\\ s.,s• \ c: NNf\...... . .1.1\ ,RE1O'criEWE4 717 \ 2 \ • N • \ .\*\•\ \ \ r13.20 121RON(4 -"...12:CPE 1(.211.19 25149-2220 1814-179.42 1 OVVC(N & 5)16172.72 504414-7277 11114-1796 !e0431:333..7.4 MOLT \ \\\\\ /.- - \* l'‘ 4r1-414.070 41.4....7.218 .6.F. \ \ . \ \ s . ...... . ..,..„. N „ N. \ • ---.... ..-..., . ay. .--. '•• \ N. NN.N.N _ ---- --- -- \\ \ -..... •„ , . .., ...., ."., . • 9 I I / -.---`:-------- . r` \ ,, .• ' \\ \\\ \ \ \\ s_ _ .-- 1 \ •-... \ \ \ \ \\\ \\ `", . ' ' • .:..• 7.115 S.F. • • 17'C.'6(5)16-201.70 1 94 501.01 -2195 TYPE 1 / 18E1.03 / 2471E-184.03 24CONC S 1E-182.33 24-0071E-111.73 6(6)16-10.3 95 \ \ \\\ \ \ \ • \ \ • \ 4 \ 5 N \\ \\ \\\ , \\ 4 \ 7,88851. \ )\`-' >)\ \'\\\\' \ • v • . , /, / v •1, 15.1_ 03.60 E)16.201.50 R64-203.89 74.CONC(S6)1(.199.17 24'CON6(N)16.199.04 4.199.87 06149 45)3I60---- 27;Ti6 (O9 417116127 20.00 traTiogswg GI .0 §: RECEIVE9 DEC 01 Hi 0EvELOP1IF. 1 4 A g Q z z 0 0w1- -500 zi a a cr a 2 uf cn - 3 g ;„, Z ai 0Cs4 C4 Oa 2 ,:o cf, h."Z N ,r,",-; C6 § 8 v.,. 0 2 T-1 DJEDEL Xrel: , ,12650-pb.dwp, ,12650-pt.dwg. :12650-ps.thvg