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HomeMy WebLinkAboutPermit L92-0065 - FOSTERVIEW ESTATES - PLANNED RESIDENTIAL DEVELOPMENTl92-0065 13400 42nd avenue south fosterview estates Additional information about the Fosterview Estates Project can be found in the following files: L92 -0066 SEPA Determination L93 -0014 Preliminary Plat PW96 -0151 Land Altering Permit L99 -0018 Final Plat .; At the Committee of the Whole meeting on April 24, 2000 the Council deliberated on the evidence and testimony presented at the April 17th public hearing. The record shows that: The City mailed and posted the Notice of Public Hearing for the approval of the CC &Rs on April 3, 2000; and • The Tukwila City Council held a public hearing for the CC &Rs on April 17, 2000 and heard testimony from Staff, the applicant and the citizens of Tukwila. The consensus of the COW was to support the findings, conclusions and recommendation contained in the staff report for the project dated April 4, 2000. They requested that Staff return at the May 1st Council meeting with approval language for final action on the development. Draft Motion: I move that the CC &Rs for the Fosterview Estates Planned Residential Development be approved as presented based on the findings and conclusions contained in the staff report dated April 4, 2000. FOSTERVIEW ESTATES COMPLIANCE WITH THE PRELIMINARY PLAT CONDITIONS Note to Reader: This narrative is provided for purposes of final approval of the land altering permit as- built plans. An additional supporting narrative will be provided during the final plat review process. City Council Preliminary Plat Conditions The following conditions are numbered 1 — 20 as adopted by the Council on May 9, 1994. 1. That south 137t1i Street which bisects the property, have 40 -foot right of ways, 30 -feet of pavement curb to curb, and 5 -foot easements on either side. Comment: The Applicant has met this condition as indicated on the land altering permit civil drawings. The improvements have been installed and are pending inspection by City staff as part of the land altering permit process. (See Civil Drawing Sheet C -1 dated 10 -21 -99 and C -5 dated 10- 21 -99, and the Final Plat) 2. The width of pavement for 43rd Place shall be 24 feet; The width of right of way for 43rd place shall be 24 feet; A 10 -foot wide utility easement shall run along the south side of 43rd Place South and shall contain a five -foot wide sidewalk. Comment: The Applicant has met this condition as indicated on the land altering permit civil drawings. The improvements have been installed and are pending inspection by City staff as part of the land altering permit process. (See Civil Drawing Sheet C -1 dated 10- 21 -99, C-5 dated 10 -21 -99 and the Final Plat) 3. That TMC, Section 17.24.040(g)(4) be implemented: for through lots, a 15 -foot rear yard buffer of native vegetation shall be provided. Comment: The through lots are identified as lots 21,22 and 23 (previously known as lots 22, 23 and 24 on the approved preliminary plat). The Applicant will post a performance bond, prior to the City Council's consideration of the final plat, for planting the required 15-foot rear yard buffer of native vegetation after house construction. The planting will be installed in accordance with the Landscape Plan and will be inspected by the City prior to release of the performance bond. A 36 -inch tall split rail fence, as indicated on the Landscape Plan, will also be installed at the western edge of the buffer to delineate the buffer of native vegetation. The buffer is indicated on the final plat. (See Civil Drawing Sheet C -1 dated 10- 21 -99, C -5 dated 10 -21 -99 and the Final Plat) E:WDMNDATA \laofi nalplatnarr.amn.doc Fosterview Page 1 of 10 October 22, 1999 4. The Applicant shall prepare, and the Directors of the Departments of Community Development and Public Works and the City Attorney shall approve, a performance bond for project phasing prior to Final Plat approval. The purpose of the bond is to protect on and off site properties from unforeseen circumstances related to the development. The performance bond shall last for a two -year period and commence from the completion date of each phase. Comment: On November 24, 1998 Brent Carson, Buck & Gordon, sent a letter to Mr. Lancaster responding to Council Preliminary Plat Condition No. 4 regarding bonding requirements during the home construction phase. On January 12, 1999, Nora Gierloff provided comments on the bonding requirements. In response to City comments, the Applicant has proposed a bond condition to be included as part of the Final Plat approval. Responsive changes have also been provided to the City in the proposed bond language itself. On March 4, 1999, the Applicant submitted the final performance bond language for approval by the Directors of the Departments of Community Development and Public Works and the City Attorney. 5.. Hold harmless language including relationships to future slope instability, shall be prepared by the Applicant and reviewed by the City Attorney, the Departments of Public Works and Community Development. Such language shall be included in the Final Plat documents and in each property deed. Comment: The Applicant prepared hold harmless language including relationships to future slope instability and the proposed language was reviewed and approved by the City Attorney, the Departments of Public Works and Community Development. The language has been included on the Final Plat. 6. The Director of Community Development shall recalculate the bonus density calculations based on the street widths of the Final PRD and require that total density be adjusted accordingly. Comment: The Director of Community Development has reviewed the Final Plat Mylar for compliance with this condition and has approved the density (40 lots) shown on the Final Plat. It should be noted that although this condition references bonus density, bonus provisions are not included in this development. Rather, the development transferred the allowed density from the sensitive areas to the buildable area of the development. The condition was met at preliminary approval and remains unchanged. 7. Lot widths for perimeter lots shall be a minimum of 50 feet. Perimeter lots include: Lots 1 through 9, Lots 14 through 19, Lots 25 through 28; Lots 32 through 35 and Lot 41. Comment: All perimeter lots have been shown on the Final Plat with a minimum width of 50 feet. It should be noted that the Final Plat contains only 40 lots versus the 41 lots approved in the preliminary plat. As such, the lot numbers have been renumbered E:W DMNDATA \Iaofinalplatnarr.amn.doc Fosterview Page 2 of 10 October 22, 1999 and the perimeter lots now include: Lots 1- 8, Lots 13 -18, Lots 24 - 27, Lots 31- 34 and Lot 40. 8. Lots that are on the perimeter of the development have a required front yard setback of 20 feet if the front yard faces the perimeter; side yard setbacks that are equal to Tukwila R -1 Code; and a back yard setback equal to Tukwila R -1 code if the back yard faces the perimeter of the development. Comment: The required setbacks have been shown on the Final Plat. - / 9. The 20 -foot utility access easement proposed along a portion of the north property line beginning at the east edge of the right -of -way to be vacated and running westerly a distance of approximately 124 feet, shall be labeled as: "20 -foot public utility and pedestrian access easement ". Comment: 10. The Comment: A. The required 20 foot public utility and pedestrian access easement has been delineated and labeled on the Final Plat. Final Plat be conditional upon satisfactory BAR review as required to TMC 18.46.060(g). As part of the Council's December 1993 approval, the Council required satisfactory BAR review. The BAR review and recommendation was completed in early 1994 and then considered by the Council in April 1994. Conditions A and B below are a result of this process. That a mixture of Western Red Cedar or some other similar coniferous tree be installed at the rear of lots 22, 23, 24 and at the front of lots 2 and 3, (to replace proposed deciduous trees); and that all additional trees specified in Section I and II (Planning Commission Report) be a representative mixture of either native or introduced, fast growing coniferous trees. B. The maximum achievable ground cover be achieved and that the planting exhibit vigorous growth both at the time of planting and throughout the period of guarantee, which shall become a condition of the Final Plat approval. Comment: The Applicant will post a performance bond, prior to the City Council's consideration of the final plat, for planting the required coniferous trees and ground cover. The ,planting will be installed in accordance with the approved Landscape Plan, which includes the additional landscaping required by this condition, prior to release of the performance bond. 11. That the Final Plat be conditional upon staff providing Council with satisfactory evaluation of the off site perspectives or a modification to the planning requirements as required in Legal Conditions in 18.46.060(0(1). E: ADMNDATA \laofinalplatnaa.amn.doc Fosterview Page 3 of 10 October 22, 1999 Comment: As part of the Council's December 1993 approval, the Council required satisfactory evaluation of the off site perspectives. The Planning Commission review and recommendation of this issue was completed in early 1994 and then considered by the Council in April 1994. Conditions A below is a result of this evaluation process. A. Add 6 trees to meet the coverage requirements per TMC, Section 18.46.060(0(1). Trees shall be planted at the front of lot 2, and at the rear of lots 9, 14, 16, 17 and 18. The tree types shall be specified by the Department of Community Development. Comment: Six trees have been planted to meet the coverage requirements of TMC, Section 18.46.060(/)(1). Red Sunset Maple trees, as specified by the Department of Community Development, have been planted at the front of lot 2 and at the rear of lots 8,13,15,16, and 17 (formerly 9,14,15,16 and 17). 12. A 5 -foot high, black color- coated chain link fence shall be erected along the north property line from the Southgate Park boundary eastward on top of the bulkhead or rockery, and a dense hedge be planted on the property immediately north of the site. Comment: The Applicant met with the property owners along the north property line from the Southgate Park boundary eastward to discuss the improvements along the north property line. At the request of the property owners, a keystone wall has been built north of the subject site on the adjacent owners property (instead of on the shared property line). A dense six foot tall evergreen Pyramidalis hedge has been installed immediately north of the subject site. A 5-foot high, black color - coated chain link fence has been erected along the north property line from the Southgate Park boundary eastward. 13. Landscaping: Street trees shall vary between conifers and deciduous. Minimum sizes will be 2 '/2 " caliper; or 8 -10 feet high. Comment: The street trees on the perimeter of the site have been installed and vary between conifers and deciduous trees. The minimum size requirement has been met. A performance bond for the internal street trees will be posted, prior to the City Council's consideration of the final plat, and installation will occur following construction of the homes on the adjacent lots. The internal street trees will also vary between conifers and deciduous trees. The City will hold the performance bond until the trees are installed and then inspected and approved by the City. 14. Additional trees shall be provided as shown on Exhibit 2 of the City Council packet dated April 25, 1994. Comment: The referenced Exhibit 2 is the same Exhibit 2 as provided in the December 1993 Council packet. The landscape plan was revised following the December 1993 approval to meet this condition. The revised landscape plan was discussed at the Apri11994 Council proceedings and it was determined that the revised landscape plan E:\A DMNDATA \laofinalplatnarr.amn.doc Fosterview Page 4 of 10 October 22, 1999 was consistent with the requirements of this condition. The landscape plan continues to meet this requirement. 15. The Final Wetlands Mitigation/Enhancement Plan is for the roadway crossing and buffer reduction. The plan must be provided to and approved by DCD prior to issuance of Land Altering Permits. Recommended vegetation must include a diversity of trees compatible with existing vegetation. The Final Wetlands Mitigation Plan shall contain the following at a minimum: A. The amount of clearing and grading proposed for the roadway crossing at the watercourse and any grading within the associated wetland/buffer areas including cross - sections showing areas of disturbance; B. A report which describes: (1) The purpose of the enhancement/restoration; (2) The areas to be enhanced/restored; (3) How the areas will-enhanced/restored; (4) The selected plantings for roadway crossing and buffer reductions; (5) When the enhancement will occur; (6) A 2 -year maintenance /monitoring program. Comment: A final wetland mitigation/enhancement plan was prepared by Terra Associates on March 13, 1996 and approved by the City. The City inspected the planting on June 10, 1999. By its June 15, 1999 letter, the City acknowledged that the enhancement plan had bee correctly implemented with a minor exception in regard to some missing plants. These missing plants have been installed and a bond will be posted for maintenance and monitoring prior to the City C'ouncil's consideration of the final plat. Please note that as part of the final plat approval process, the applicant is requesting that the City Council allow deletion of the retaining wall adjacent to the wetland buffer in conjunction with supplemental wetland buffer enhancement. 16. Should a sign be proposed at some future date, the design shall be reviewed by DCD to ensure it is in keeping with the overall design of the project and that it is sited so as not to obstruct visibility to vehicles. Comment: The Applicant has not submitted an application for a sign and acknowledges that a sign proposed at a future date will be reviewed by DCD for compliance with this condition. 17. Street lighting shall be redesigned to be more in keeping with the residential character of the area. The final design shall be administratively approved by DCD. E:'A DMNDATA \Iaofinalplatnarr.amn.doc Fosterview Page 5 of 10 October 22, 1999 Comment: The street lighting has been redesigned and was approved by City staff on June 4, 1998. The electrical design and layout was prepared by Armstrong Engineers for Service Electric and includes "Centrecon Poles and GE Luminaire "fixtures. The streetlights have been installed and were inspected and approved by the State Department of Labor and Industries on October 1, 1998 (L &I project # 1243420). 18. The discrepancy between the Landscape Plan and Grading Plan related to areas to be held in open space easements shall be corrected. The correction shall accurately delineate the boundaries of these areas. The revised Landscape Plan and Grading and Street Plans must be consistent and provided prior to issuance of Land Altering Permits. Comment: The Applicant corrected the discrepancy during the land altering permit review to ensure that the Landscape Plan and Grading and Street Plans accurately delineated the boundaries of the open space easement areas noted as Tract A and B. 19. The developer shall erect a permanent three -foot high split -rail wood fence along the boundaries of all open space easement locations prior to any grading. Comment: Prior to any grading, the Applicant installed a permanent three-foot high split rail wood fence along the boundaries of Tract A and B. The fencing has been maintained and signs have also been posted on the fence approximately every 100 feet to indicate the need to protect the open space. 20. The final Conditions, Covenants, and Restrictions shall be submitted with the Final Plat application and shall include a revised legal description which specifically describes open space easement areas. Comment: The Applicant has prepared the final Conditions, Covenants, and Restrictions (CC&R's) language and has submitted them for the City's review. The February 2, 1999 CC &R's contain legal descriptions and restrictive language regarding the open space easement areas (Section 1.5.3, Section 4.14 and Section 7.1.6 & .7). Amended SEPA Mitigated Determination of Non - significance Fosterview Estates L92 -0066. DRAINAGE Mitigation Conditions: 1. Wet vaults in addition to a biofiltration swale shall be constructed. The bioswale assists in the removal of conventional pollutants while wet vaults provide for some filtering and settlement prior to discharge into the proposed drainage system. The biofiltration swale shall be located within the 43rd Avenue S. right -of -way. Shade - tolerant plant species shall be used to ensure plant survival and function of the biofiltration swale. Wet vaults shall be easily accessible by maintenance vehicles and designed in accordance with the King County Surface Water Design Manual. E:\ADMNDATA\laofinalplatnarr.amn.doc Fosterview Page 6 of 10 October 22, 1999 Comment: Three wet vaults have been constructed as shown on Civil Sheet C -8 and C -9 dated 10- 21 -99. The bioswale is to be built after final plat approval and will be secured by a performance bond prior to the Council's consideration of the final plat. The bioswale is also indicated on Civil Sheet C -8 and C -9 dated 10- 21 -99. Please note that as part of the final plat approval process, the applicant is requesting that the City Council allow deletion of the bioswale as being redundant and inconsistent with geotechnical recommendations. 2. All runoff and drainage from the on -site drainage system shall be discharged directly to the proposed storm drainage improvements proposed on 43rd /44th Ave. S. right -of -way. The spreaders shown on conceptual plans shall be omitted. The final design of the system will be updated to accommodate underground springs volumes uncovered during construction of the roadways. Comment: All runoff and drainage from the on -site drainage system has been designed and - installed to discharge directly to the storm drainage improvements onto 43'1/44rh Avenue South right -of -ways. (See Civil Drawing Sheet C -8, C -9, C- 10,and C -11 dated 10- 21 -99) The run off and drainage from the retaining wall subterranean collection systems is designed to recharge the wetlands and ground water as outlined in memo from the City dated 1- 25 -99. TRAFFIC - VEHICULAR Mitigation Condition: 1. A guardrail shall be installed along 42nd Avenue South immediately north of the S. 137th Street access point into the subdivision as shown on drawings received April 26, 1993. Comment: The guardrail has been installed by Petersen Brothers per the current design manuals of the Washington Department of Transportation TRAFFIC - PEDESTRIAN Mitigation Condition: 1. A pedestrian walkway shall be installed along S. 137th Street from 44th Avenue South to Macadam Road. The City shall be responsible for the design and installation of the walkway and drainage improvements. The Applicant shall reimburse the City for '/2 of the total amount of construction and inspections costs. Based on pedestrian path costs of the last two years, the anticipated cost wold be a total of $60,000. The total amount to be paid by the developer shall be $30,000. Improvements include 750 lineal feet of walkway with drainage (covering the ditch for the pedestrian path) needed for about 2/3 the length. The pedestrian path unit costs have averaged $18 /foot and drainage cost have averaged $33 /foot at 500 feet. E:\ ADMNDATAMaofinalplatnarr .amn.doc Fosterview Page 7 of 10 October 22, 1999 Comment: The Applicant will reimburse the City up to $30,000 (thirty thousand dollars), upon confirmat {on of the improvement cost and that the improvements have been installed. SLOPE STABILITY Mitigation Conditions: Prior to Issuance of Land Altering Permits 1. To avoid future slope instability both during and after site development and to ensure proper construction of cuts and fills, the Applicant shall provide a slope stability analysis which demonstrates that the proposed fills on slopes, to be designed, are stable. The analysis shall accompany applications for land altering permits and shall be evaluated be peer review prior to permit issuance. Should the results of the stability analysis require significant design changes to the Preliminary Plat, the Preliminary Plat must be revised and new hearing shall be required. Comment: Terra Associates provided a slope stability analysis through the land altering permitting process. These reports along with construction monitoring reports are provided in a 3 ring binder dated December 11, 1998 and amended on October 22, 1999. Terra Associates has also prepared a written response to the Shannon & Wilson peer review comments (see October, 1999 letter). The issue of slope stability has been specifically addressed in the Terra Associates letters. 2. A geotechnical engineer of record shall be retained throughout the construction phase(s) of the project and shall monitor earthwork and review the final design and building specifications for all lots to assure conformance to the recommendations contained in the geotechnical reports prepared by Terra and Associates as listed on the previous page. Comment: Terra Associates provided monitoring of the earthwork and provided written findings and recommendations during the grading activity. Terra Associates has also reviewed the final design and building specifications for all of the lots to assure conformance to the recommendations contained in the geotechnical reports. 3. The developer's engineer shall prepare for review by Terra and Associates, and the City, detailed cross sections in all planned fill areas indicating how the fill will be keyed, benched, and drained as recommended in the Terra geotechnical report. A typical detail shall be prepared illustrating the geotechnical engineer's recommended key at the toe of all proposed fills on slope. Calculations supporting adequate safety factors against slope instability shall be provided for review by the City. Comment: The Applicant met this condition during the land altering permit process. The site construction was reconstructed with structural fill and inspected by Terra Associates. Sheet 3.0 shows detailed cross sections indicating how the fill is keyed, benched, and drained as well as a detail illustrating the recommended key at the toe of all proposed fill slopes. Calculations supporting adequate safety factors against slope instability are provided in tab 9 of the Terra Associates findings. dated October 22, 1999. Terra Associates findings are provided in a 3 ring binder dated December 11, 1998 and amended October 22, 1999. E:\ADMNDATA \laofinalplatnarr.amn.doc Fosterview Page 8 of 10 October 22, 1999 4. The developer's engineer in conjunction with the geotechnical engineer shall prepare detailed design cross - sections addressing subdrainage provisions for fills placed on slopes and underlain by lacustrine deposits. Comment: Terra Associates provided the slope stability analysis through the land altering permit process. Sheet 3.0 shows detailed cross sections indicating how the fill is keyed, benched, and drained as well as a detail illustrating the recommended key at the toe of all proposed fill slopes. On site observation was performed by Terra Associates to insure that this procedure was implemented correctly. Terra Associates findings are provided in a 3 ring binder dated December 11, 1998 and amended October 22, 1999. 5. The developer's geotechnical engineer shall review the foundation details and comment on the need for connecting individual footings or supporting the houses on post- tensioned slabs as a possible means of reducing potential for differential settlement of the structures. Comment: Conditions for home construction will be reviewed upon the completion of specific home design foundations. These lot specific packages will be forwarded to the City on an individual lot by lot basis when we submit for a single family home permit. The geotechnical of record will provide lot specific letters for each lot foundation design. The final plat will include a note/condition to address this issue. 6. Construction monitoring by the geotechnical engineer shall be provided, with written confirmation provided to the City that all work has been performed in accordance with the geotechnical recommendations. Comment: Terra Associates provided monitoring during site construction and transmitted written confirmation that all work was performed in accordance with the geotechnical recommendations. In those instances where work was not proceeding according to the geotechnical recommendations, Terra Associates provided recommendations for corrective actions and these have been completed. These documents are included in a 3 ring binder dated December 11, 1998 and amended October 22, 1999. 7. The proposed earth cuts and rockery along the existing road right -of -way for 42nd Ave. S. (behind Lots #1, 2 & 3) shall also be reviewed by the geotechnical engineer to assure lateral stability of the existing roadway and the new road and utility improvements. Comment: Compliance with this condition has been met through the specific permitting process of the keystone wall that was installed at the access driveway for lots 1 and 2 (Permit No. MI 98 0009). Please note that lot 3 has been deleted. Terra Associates provided monitoring during this development improvement construction and submitted written conformation that all work was preformed with the geotechnical recommendations. This letter is dated November 7, 1997. This document is included in a 3 ring binder dated December 11, 1998 and amended October 22, 1999. E:\A DMNDATA \Iaofinalplatnarr.amn.doc Fosterview Page 9 of 10 October 22, 1999 During Construction 8. Boundaries of Tracts A and B (as shown on Exhibit C) shall be flagged and fenced to prevent intrusion during construction. Sloped areas (Exhibit C) shall also be delineated and a barrier fence erected prior to clearing and grading. Fencing locations shall be inspected by the City prior to land clearing. All fencing damaged due to construction shall be immediately replaced during the construction phase. Comment: The boundaries of Tracts A and B were flagged to prevent intrusion during site construction. The boundaries of these tracts are also identified by a permanent split- rail fence to prevent intrusion during construction of the single-family homes. E: W DMNDATA \Iaofinalplatnarr.amn.doc Fosterview Page 10 of 10 October 22, 1999 9. Grading activity shall be outside of the drip line of preserved trees as shown on the approved landscape plan. Comment: During site construction of the approved storm and sewer utility lines, grading activity occurred which resulted in the disturbance and removal of trees that were identified for preservation during the preliminary plat review. The disturbance and removal of these trees could not be avoided due to the proximity of the trees and root structure to the utility lines. In consultation with the City, the Applicant has replaced the trees at a 2 :1 ratio (see SEPA condition 10. below). 10. Vegetation to be retained per the approved landscape plan shall be replaced at a 2:1 ratio if disturbed during any phase of construction. Comment: 74 trees that were to be retained were disturbed during construction. The Applicant has replaced these trees at a 2 :1 ratio (148 new trees - Includes a variety of Cedar, Alder and Big Leaf Maple). Following Construction 11. Permanent visible markers shall be placed to delineate the boundaries of Tracts A and B where adjacent to single - family lots and rights -of -way. Comment: Permanent visible markers have been. placed delineating the boundaries. 0/ tracts .4 & B. These signs have been posted on the fence approximately every 100 feet as well as along the rights of' way indicating the need to protect the open space. E:\ ADMNDATA \laofinalplatnarr.amn.doc Fosterview Page 11 of 10 October 22, 1999 ';iv�•u:i;^niv;.::::Tc;2o: F +i: "rs: ,.,. MEMORANDUM TO: File: Fosterview Estates Final Plat #L99 -0018. FROM: Gary Schulz, Urban Environmentalist • DATE: October 8, 1999 RE: Meeting Record with Anna Nelson; -Buck & Gordon & Garett Munger, Terra Assoc: Wetland Mitigation/Enhancement Phan status. Yesterday afternoon I met with Garett and Anna on the site to look at and discuss sensitive area buffer plantings. The purpose of the meeting was to get my input and Garett's on the success of the plantings and proposed additional enhancement. The proposed additions include enhancing the buffer area along the new portion of S. 137th Street with new shrub plantings. The applicant will present to the City Council the landscape enhancement in order to get relief from building the retaining wall that was approved as a condition for several reasons. I told Anna the required retaining wall came from a combination of issues including 1) final grading standards for homes to be built on the south side of S. 137`' Street, 2) limiting the intrusion into the watercourse buffer, and 3) possible structural needs for the new street. Large rock has been used in the shoulder north of the street I made it clear to them that the integrity of the street is a Public Works issue and additional plantings may not be enough to change the requirement. We did agree that certain native plants will appropriate and could be established on in this area. Some plantings in the buffer have died and will be replaced after a decision is reached on the retaining wall. They commented that existing plantings will be lost if the wall is required. My reply is that the entire wall issue could have been avoided. The question of tree replacement for the north boundary open space area was discussed. It appears that additional trees have been planted recently in this area. We did not attempt to count the trees but I feel it will need to be done soon as leaves will be gone this month. I told Anna I would need to discuss with the Director as to how it would handled in preparation for the final plat hearing. City of O, Tukwila John W Rants, Mayor Department of Community Development Steve Lancaster, Director October 28, 1998 John Kappler Kappler Architects 13400 Northup Way Suite 33 Bellevue, WA 98005 RE: Fosterview CC &Rs and Hold Harmless Language Dear Mr. Kappler, The City Attorney and I have reviewed the CC &Rs for the Fosterview subdivision. Our comments are enclosed, and mainly concern lot renumbering and realignment due to the deletion of Lot 3. City Council condition 20, which requires legal descriptions of the open space easements to be included with the CC &Rs, will also have to be met at final plat. The City Attorney had one clarification to the hold harmless language, which is enclosed. If you have any questions or comments, please call me. Sincerely, It Nora Gierlo Associate Planner cc: Bob Noe, City Attorney 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 4313665 DUJARDINflDEVELOPMENT COMPANY AN ALLEGRE ENTERPRISE October 11, 1996 City of Tukwila 6300 Southcenter Blvd. Tukwila, WA 98188 Re: Fosterview Estates Attn: Ron Cameron Dear Ron: 9623 - 32nd SL S.E., Everett, WA 98205 P.O. Box 5308, Everett, WA 98206 Everett Phone: (208) 334 -5018 From Seattle: (208) 743-6140 FAX: (206) 334 -5041 ■■ On October 9, 1996 our superintendent, Gary Bunistead met with Gary Schulz to review the impact of the tree removal resulting from the installation of our infrastructure lines at the referenced. project. We are in agreement to replace 74 trees at a two-to-one ratio for. a total of 148 trees. The plantings will be distributed throughout the plat and prior to planting we will coordinate the locations with Mr. Schulz. Sincerely, illiam A. Fowler Vice President WAF/lkp Q. • 2 , yZL 5 v,,,� c> vek development / construction / management DUJARD•204L0 RECEIVED MAY 3 01996 KWILA n DEPARTMENT OF FI$M HYDRAULIC PROJECT APPROVAL R.C.W. 75.20.100 R.C.W. 75.20.103 February 9, 1996 t DEPARTMENT OF FISHERIES General Administration Bldg. Olympia, Washington 98504 (206) 753 -6650 E3 iC WORK PPlicant should refer to this date in all correspondence) PAGE 1 OF 2 PAGES 10 LAST NAME FIRST 18 CONTACT PHONE(S) Company (206) 334 1 CONTROL NUMBER 00- 82727 -02 Dujardin Development -6018 19 STREET OR RURAL ROUTE ATTN: William Fowler 7 8 0 WRIA 09.0032 9623 32nd St SE CITY STATE ZIP Everett WA 98025 14 17 MIIATER TRIBUTARY,TO Unnamed (Southgate Cr) Duwamish River 11 TYPE 0 ROJECT Install Culvert 13 UARTER SECTION TOWNSHIP RANGE(E -W) COUNTY SECTION SE 15 23N 04E King TIME LIMITATIONS: 5 THIS PROJECT MAY BEGIN 6 AND MUST BE COMPLETED BY October 15, 1996 June 15, 1996 THIS APPROVAL IS TO BE AVAILABLE ON THE JOB SITE AT ALL TIMES AND ITS PROVISIONS FOLLOWED BY THE PERMITTEE AND OPERATOR PERFORMING THE WORK. ON REVERSE SIDE. OF APPROVAL, a renewal and on June 8, 1995. This by William Fowler, 2, 1996( and it super- for this project. in a location where contractor shall notify fax( at (206) 338 -1066, and Wildlife (WDFW), 16019 of the project start Area Habitat Biologist of construction the permittee's name, and the control number entitled, Estates," dated May 24, by this HPA. These 220 -110 WAC. A copy of construction. structural integrity to of the debris likely to be ext. 107 SEE IMPORTANT GENERA!, PROVISIONS NOTE: This Hydraulic Project Approval (HPA) is modification of the original HPA issued HPA is in response to a written request Duaardin Development Company, on Febrary sedes all previous HPAs and modifications This culvert is proposed for installation fish passage is not a concern. 1. NOTIFICATION REQUIREMENT: The permittee or the Area Habitat Biologist listed below, by or mail, at Washington Department of Fish Mill Creek Blvd, Mill Creek, Washington 98012, date. Notification shall be received by the at least three working days prior to the start activities. The notification shall include fproject location, starting date for work, or this HPA. 2. Work shall be accomplished per plans and specifications "Planned Residential Development Fosterview 1995, and submitted to WDFW( except as modified Tans reflect design criteria per Chapter plans plans shall be available on site during 3. The culvert shall be installed to maintain the 100 -year peak flow with consideration encountered. SEPA: MDNS, City of Tukwila, August 1993 REGIONAL HABITAT MANAGER - Philip Schneider (206) 775-1311 PATROL - Boone 024 [P3] APPLICANT - WILDLIFE - READER - PATROL - HAB. MGR. - WRIA DEPARTMENT OF FISHERIES. DIRECTOR DEPARTMENT OF FISHERIES HYDRAULIC PROJECT APPROVAL R.C.W. 75.20.100 R.C.W. 75.20.103 rj February 9, 1996 (applicant should refer to this date in all PAGEZOF 2 PAGES DEPARTMENT OF FISHERIES General Administration Bldg. Olympia, Washington 98504 (206) 753-6650 correspondence) 10 LAST NAME Dujardin Development Company CONTACT PHONE(S) (206) 334 -6018 CONTROL NUMBER 00- 82727 -02 12 uaret:Unnamed (Southgate Cr) 9 WRIA 09.0032 4. Fill associated with the culvert installation shall be protected from erosion to the 100 -year peak flow. 5. The culvert shall be installed and maintained to avoid inlet scouring and to prevent erosion of stream banks downstream of the project. 6. The culvert shall be installed in the dry or in isolation from the stream flow by the installation of a by -pass flume or culvert or by pumping the stream flow around the work area. 7. A sandbag revetment or similar device shall be installed at the downstream end of the by -pass to prevent backwater from entering the work area. 8. The by -pass shall be of sufficient size to pass all flows and debris for the duration. of the project. 9. A sandbag revetment or similar device shall be installed at the by- pass inlet to divert the entire flow through the by -pass. 10. Alteration or disturbance of the bank and bank ve etation shall be limited to that necessary to construct the project. Within seven calendar days of project completion, all disturbed areas shall be protected from erosion using vegetation or other means. 11. If a pump is used, it shall be large enough to pump the entire stream around the work area. Once the pump is started, it shall run continuously until the streambed and bank in the work area is restored.. 12. The pump discharge shall be placed downstream of the sandbag dam into an area that will not create erosion. LOCATION: Off of 44th Avenue South where the new east extension of South 137th Street crosses 44th Avenue South. bk c: Erich Teitze, 121 5th Ave N, Ste 200, Edmonds, WA 98020 RECEIVED MAY 3 01996 TUKWILA PUBLIC WORKS REV 10/16/88 City of Tukwila John W. Rants, Mayor Department of Public Works January 18, 1996 Bill Fowler Dujardin Development Company P.O. Box 5308 Everett, WA 98206 RE: Fosterview Estates Land Altering Permit Review Dear Mr. Fowler: Ross A. Earnst, P. E., Director The City of Tukwila Public Works and Community Development Departments have completed their initial review of the plans submitted for a land altering permit. Following is our analysis of how the requirements of the approval have or have not been met. Additional submittals are necessary to resolve the outstanding issues identified in this letter. The comments have been developed by reviewing the plans. They are organized in order of conditions imposed by the City Council, SEPA mitigation measures, and recommendations of the consultants and peer reviews. If you feel we've erred in our analysis of any of the conditions below, don't hesitate to contact us to provide an explanation as to how the particular condition has been satisfied. City Council Conditions (minutes attached): 1. That S 137 ST which bisects the property, have 40 -foot right -of -way, 30 -feet of pavement curb to curb, and 5 foot casements on either side. Comment: Revise the plans to show the five foot easement on Tract B. Also, the five foot easement needs to be clearly identified along its' entire length. The paving of S 137 St between 44 Ave S and S 137 PL needs to be reduced from 32 to 30 feet curb to curb. 6300 Southcenter Boulevard, Suite #100 • Tukwila. Washlneton 98188 • Phone: 1206) 433 -0179 • Fax 1206! 4313665 Fosterview Page 2 2. The width of pavement for 43 PI S shall be 24 feet; The width of right -of -way for 43 PI S shall be 24 feet; A 10 -foot wide utility easement shall run along the south side of 43 PI S and shall contain a five -foot wide sidewalk. Comment: The plans are consistent with this requirement. 3. That TMC, Section 17.24.040(g)(4) be implemented: for through lots, a.15 foot rear yard buffer of native vegetation shall be provided. Comment: The plans show a 15 foot native vegetation buffer on Lots 16 -19 and 22- 28. 4. The applicant shall prepare, and the Directors of the Departments of Community Development and Public Works and the City Attorney shall approve, a performance bond for project phasing prior to final plat approval. The purpose of the bond is to protect on and off -site properties from unforeseen circumstances related to the development. The performance bonds shall last for a two -year period and commence from the completion date of each phase. Comment: The performance bond has not been submitted. A performance bond will be required with the land altering permit(s) and final plat. The bond amount will be based on the work of each land altering phase. The Performance Bond should provide for Geotechnical Engineering expertise funding if the City needs this expertise for any unforeseen circumstances. 5. Hold- harmless language including relationships to future slope instability, shall be prepared by the applicant and reviewed by the City Attorney, the Departments of Public Works and Community Development. Such language shall be included in the Final Plat documents and in each property deed. Comment: This hold - harmless language has not been submitted. 6. The Director of Community Development shall recalculate the bonus density calculations based on the street widths of the Final PRD and require that total density be adjusted accordingly. Comment: In order to complete this calculation, the applicant needs to submit the area of road dedication. This recalculation must occur prior to issuing a land altering permit to ensure that grading and improvements are consistent with the allowable number of lots. Fosterview Page 3 7. Lot widths for perimeter lots shall be a minimum of 50 feet. Perimeter lots include: Lots 1 through 9; Lots 14 through 19; Lots 25 through 28; Lots 32 through 35 and Lot 41. Comment: The submittal meets this condition. The plans show that the lots widths of these lots at the perimeter are a minimum of 50 feet wide. . 8. Lots that are on the perimeter of the development have a required front yard setback of 20 feet if the front yard faces the perimeter; side yard setbacks that are equal toTukwila R -1 Code; and a back yard setback equal to Tukwila R -1 code if the back yard faces the perimeter of the development. Comment: Lots 16 -19 do not appear to meet side yard setback requirements of xx feet. A revised plan shall clearly show, both by scale and dimensions, that all of the perimeter lots meet the required setbacks. 9. The 20 -foot utility access easement proposed along a portion of the north property line beginning at the east edge of the right -of -way to be vacated and running westerly a distance of approximately 124 feet, shall be labeled as: "20 -foot public utility and pedestrian access easement." Comment: The plans comply with this requirement. 10. The final plat be conditional upon satisfactory BAR review as required in TMC 18.46.060(g). a. That a mixture of Western Red Cedar or some other similar coniferous tree be installed at the rear of lots 22, 23, 24 and at the front of lots 2 and 3 (to replace proposed deciduous trees); and that all additional trees specified in Section I and Section II (Planning Commission Report) be a representative mixture of either native or introduced, fast - growing coniferous trees. b. The maximum achievable ground cover be achieved and that the plantings exhibit vigorous growth both at the time of planting and throughout the period of guarantee, which shall become a condition of final plat approval. Comment: This issue to be reviewed at the time of final plat. Fosterview Page 4 11. That the final plat be conditional upon staff providing Council with a satisfactory evaluation of the off -site perspectives or a modification to the planning requirements as required in Legal Conditions in 18.46.060(f)(1). a. Add six (6) trees to meet the coverage requirements per TMC, Section 18.46.060(f)(1). Trees shall be planted at the front of lot 2, and at the rear of lots 9, 14,16,17 and 18. The tree types shall be specified by the Department of Community Development. Comment: This issue to be reviewed at the time of final plat. 12. A 5 -foot high, black color- coated chain link fence shall be erected within the north property line from the Southgate park boundary eastward on top of the bulkhead or rockery, and a dense hedge be planted on property immediately north of the site. Comment: This condition must be addressed prior to final plat approval. 13. Landscaping: Street trees shall vary between conifers and deciduous. Minimum sizes will be 2 -1/2" caliper; or 8 -10 feet high. Comment: This issued to be reviewed at the time of final plat. 14. Additional trees shall be provided as shown on Exhibit 2 of the City Council packet dated April 25, 1994. Comment: This needs to be resolved prior to final plat approval. 15. The Final Wetlands Mitigation/Enhancement Plan is for the roadway crossing and buffer reduction. The Plan must be provided to and approved by DCD prior to issuance of Land Altering Permits. Recommended vegetation must include a diversity of trees compatible with existing vegetation. The Final Wetlands Mitigation Plan shall contain the following at a minimum: a. The amount of clearing and grading proposed for the roadway crossing at the watercourse and any grading within the associated wetland /buffer areas including cross - sections showing areas of disturbance; Fosterview Page 5 b. A report is required which describes: 1. The purpose of the enhancement /restoration; 2. The areas to be enhanced /restored; 3. How the areas will be enhanced restored; 4. The selected plantings for roadway crossing and buffer reductions; 5. When the enhancement will occur; and 6. A 2 -year maintenance /monitoring program. c. The report should identify a CCR that provides for homeowner responsibility for the ongoing wetland operation and maintenance. Comment: The Final Plan has not been submitted. This plan must be submitted and approved by the City prior to authorizing any land alterations. 16. Should a sign be proposed at some future date, the design shall be reviewed by DCD to ensure it is in keeping with the overall design of the project and that it is sited so as not to obstruct visibility to vehicles. Comment: Sign will be reviewed at such time it is proposed. 17. Street lighting shall be redesigned to be more in keeping with the residential character of the area. The final design shall be administratively approved by DCD. Comment: A lighting assembly fitting a residential area is requested. 18. The discrepancy between the Landscape Plan and Grading Plan related to areas to be held in open space easements shall be corrected. The correction shall accurately delineate the boundaries of these areas. The revised Landscape Plan and Grading and Street Plans must be consistent and provided prior to issuance of Land Altering Permits. Comment: Clear delineation needs to be clearly identified on the landscape and on the grading plans. 19. The developer shall erect a permanent three -foot high split -rail wood fence along the boundaries of all open space easement locations prior to any grading. Comment: This condition has not been met. The plans (Sheet C -3) do not show the fence located around the entire boundaries of Tracts A and B. The plans also need to show the design of the fence. Fosterview Page 6 20. The final Conditions, Covenants, and Restrictions shall be submitted with the Final Plat application and shall include a revised legal description which specifically describes open space easement areas. Comment: This issue to be reviewed at the time of final plat. SEPA Mitigation Measures SEPA mitigation includes specific conditions imposed by the SEPA responsible official and incorporates the recommendations of several consultants. DRAINAGE 1. Wet vaults in addition to a biofiltration swale shall be constructed. The bioswale assists in the removal of conventional pollutants while wet vaults provide for some filtering and settlement prior to discharge into the proposed drainage system. The biofiltration swale shall be located within the 43rd Avenue S. right -of -way. Shade tolerant plant species shall be used to ensure plant survival and function and biofiltration swale. Wet vaults shall be easily accessible by maintenance vehicles and designed in accordance with the King County Surface Water Design Manual. Comment: Wet vaults are shown on the plans. 2. All runoff and drainage from the on -site drainage system shall be discharged directly to the proposed storm drainage improvements proposed on 43 Ave S & 44 Ave S right -of -way. The spreaders shown on conceptual plans shall be omitted. The final design of the system will be updated to accommodate underground springs volumes uncovered during construction of the roadways. Comment: Plans have been modified to show this. TRAFFIC - VEHICULAR 1. A guardrail shall be installed along 42 Ave S immediately north of the S 137 St access point into the subdivision as shown on drawings received April 26, 1993. Comment: Guardrail is shown. Fosterview Page 7 TRAFFIC - PEDESTRIAN 1. A pedestrian walkway shall be installed along S 137 St from 44 Ave S to Macadam Road. The City shall be responsible for the design and installation of the walkway and drainage improvements. The applicant shall reimburse the City for 1/2 of the total amount of construction and inspection costs. Based on pedestrian path costs of the last two years, the anticipated cost would be a total of $60,000. The total amount to be paid by the developer shall be $30,000. Improvements include 750 lineal feet of walkway with drainage (covering the ditch for the pedestrian path) needed for about 2/3 the length. The pedestrian path unit costs have averaged $18 /foot and drainage costs have averaged $33 /foot at 500 feet. Comment: Actual costs were $61,200; the $30,000 will be required prior to issuing a land altering permit if any land altering traffic is to use S 137 St. SLOPE STABILITY 1. To avoid future instability both during and after site development and to ensure proper construction of cuts and fills, the applicant shall provide a slope stability analysis which demonstrates that the proposed fills on slopes, to be designed, are stable. The analysis shall accompany applications for land altering permits and shall be evaluated by peer review prior to permit issuance. Should the results of the stability analysis require significant design changes to the Preliminary Plat, the Preliminary Plat must be revised and new hearings shall be required. Comment: Slope Stability Analysis was provided by Terra Associates (dated July 25, 1995). Shannon and Wilson was retained to review the analysis and their Geotechnical Review is attached. Each of the 45 comments needs to be addressed either by the designer or geotech. The items are generally by sheet and include items such as 10a, 10b, and 10c with each being a comment. The Shannon and Wilson review was of the plans received May 25, 1995 and made at City expense. Additional reviews of subsequent plans will need to be funded by the developer and will not be made except on complete set of plans, not on plans that are submitted in parts as previously accommodated. s sr Fosterview Page 8 2. A geotechnical engineer of record shall be retained throughout the construction phase(s) of the project and shall monitor earthwork and review the final design and building specifications for all lots to assure conformance to the recommendations contained in the geotechnical reports prepared by Terra and Associates as listed on the previous page. Comment: The scope of work and contract for geotechnical monitoring will need to be approved by the City prior to issuing a land altering permit due to the significant geotechnical concerns of erosion, stability, and runoff during land altering, construction, and construction completion. The City requires daily geotechnical visits and continuos phone call availability at a minimum to assure conformance with recommendations made in the geotechnical reports. 3. The developer's engineer shall prepare for review by Terra and Associates, and the City, detailed cross sections in all planned fill areas indicating how the fill will be keyed, benched, and drained as recommended in the Terra geotechnical report. A typical detail shall be prepared illustrating the geotechnical engineer's recommended key at the toe of all proposed fills on slope. Calculations supporting adequate safety factors against slope instability shall be provided for review by the City. Comment: The detail is shown on sheet C -3, Final Grading Plan. Item 6, page 5 of the September 8, 1995 Shannon and Wilson review needs to be satisfactorily answered. Item 4 states that in the Shannon and Wilson opinion, the key and bench details are inadequate. 4. The developer's engineer in conjunction with the geotechnical engineer shall prepare detailed design cross - sections addressing subdrainage provisions for fills placed on slopes and underlain by lacustrine deposits. Comment: The September 8, 1995 Shannon and Wilson review letter identifies numerous cross section, cut & fill, and drainage items that must be addressed and resolved prior to issuing a land altering permit. 5. The developer's geotechnical engineer shall review the foundation details and comment on the need for connecting individual footings or supporting the houses on post - tensioned slabs as a possible means of reducing potential for differential settlement of the structures. Comment: This requirement to be fulfilled as part of the building permit approval. c.: -.:-rr nraa :Dori r:�- »e.•�.,�n: Fosterview Page 9 6. Construction monitoring by the geotechnical engineer shall be provided, with written confirmation provided to the City that all work has been performed in accordance with the geotechnical recommendations. Comment: The scope of work and contract for the field work will need to be approved by the City prior to issuing a land altering permit due to the significant geotechnical concerns of erosion, stability, and runoff during land altering, construction, and construction completion. The City requires geotechnical daily visits and continuos phone call availability at a minimum to assure stability, erosion control, and runoff control that is expected to require daily engineering direction. 7. The proposed earth cuts and rockery along the existing road right -of -way for 42 Ave S (behind Lots #1, 2.& 3): shall also be reviewed by the geotechnical engineer to assure lateral stability of the existing roadway and the new road and utility improvements. Comment: Terra and Associates places construction requirements on this work on page 2 of their July 25, 1995 report. 8. Boundaries of Tracts A and B (as shown on Exhibit C) shall be flagged and fenced to prevent intrusion during construction. Sloped areas (Exhibit C) shall also be delineated and a barrier fence erected prior to clearing and grading. Fencing locations shall be inspected by the City prior to land clearing. All fencing damaged due to construction shall be immediately replaced during the construction phase. Comment: This condition needs minor refinement. Sheet C -3 contains a note stating that flagging shall occur prior to grading activities. A note on the plan indicating the City must approve the fencing and flagging prior to and grading or clearing activities should be provided. 9. Grading activity shall be outside of the dripline of preserved trees as shown on the approved landscape plan. Comment: Sheet C -3 does not appear to reflect compliance with this requirement. Grading is shown to occur within the dripline of more than 25 of the trees that are to be preserved. The plan needs to be revised accordingly. .., a••n:v:^.� ?.� ..,..x. e;.F:•sr,ar,. .. .3•n:.rr,.n ^mL Fosterview Page 10 10. Vegetation to be retained per the approved landscape plan shall be replaced at a 2:1 ratio if disturbed during any phase of construction. Comment: The note on Sheet C -3 is incorrect. First, it indicates that it is acceptable to grade within the dripline of the preserved trees. This is not correct. See number nine above. Second, it indicates that the 2:1 vegetation remedy applies only to the trees shown the plans. This is not correct. This provision pertains to all of the preserved trees, including those not shown on this plan. The note shall be revised accordingly. 11. Permanent visible markers shall be placed to delineate the boundaries of Tracts A and B where adjacent to single - family lots and rights -of way. Comment: Details of the permanent markers to be approved at the time of final plat. HAMMOND, COLLIER & WADE - LIVINGSTONE ASSOCIATES, INC. (HCW -L) An independent review of the drainage system was conducted and a report prepared by HCW -L dated June 28, 1993 was adopted as a part of the proposal. The SEPA report indicates the recommendations of HCW -L must be adhered to unless otherwise agreed to and approved by the Departments of Public Works and Community Development. The individual recommendations are discussed below. GENERAL TECHNICAL RECOMMENDATIONS A. Private driveways on properties on the downhill side of any road or street should have a trench or slotted drain installed across the entire driveway width. Comment: Slotted drains need to be shown on the plans. B. Vertical curbs be used exclusively on this project, with a minimum 2 -inch lip at the driveway section, that the sidewalk section be pitched to the gutter, and that no reverse slope driveway sections be allowed. Comment: Vertical curbing is shown, a one inch lip is sufficient. Fosterview Page 11 C. Private yards for (Lots 1 -3, 21, 25 -41) have individual french drains installed transverse, across each lot, tied into their individual storm system, which will collect any subsurface drainage flows. Comment: The french drains above and below the street are NOT shown on the plans and will need to be shown and approved prior to issuing a land altering permit. The property owners responsibility for the ongoing operation and maintenance of the french drains needs to be clearly identified and attached to the title reports. D. Street improvements along 42 Ave S should be fully constructed as part of the plat development. Since there is considerable sidehill earthwork along the plat frontage of 42 Ave S, and that positive drainage collection and interception of runoff from the upper street onto the new lower home sites is critical, this curb, gutter, and sidewalk work should be constructed now. Work should include extension of a formal storm system with catch basins at spacing no greater than 300 feet, and at the new street entrance to S 137 St. Comment: Curb, gutter, sidewalk, and drainage on 42 Ave S is shown but needs to show the drainage system and, particularly, the system providing for carrying drainage that is collected south of S 137 St northward past S 137 St to the outfall and how it is to be dispersed. It is not shown on sheet C -8, Fosterview Estates Drainage Plan. E. All catch basins on the project, including the drains along 42 Ave S should be the through curb inlet frame (see King County Standard DWG #44) and utilize the vaned grate configuration (see King County Standard DWG #46). Comment: King County standards are shown as details but not located on the Drainage Plan for 42 Ave S. Final Plans will need to locate pipe, inlets, and other drainage infrastructure. F. All storm drain pipelines shall have full gasketed pipes, equivalent to ASTM C 118 heavy duty concrete drainage pipe, or ASTM -D 3034 PVC sanitary sewer pipe and gasket standards. This pipe criteria should be combined with the highest level of workmanship on catch basins of all types, for plastic pipe, utilizing gasketed catch basin connection collars grouted into the CB's using GPK manhole adapters or equal. All concrete catch basins and drainage structures should have mastic sealant or gasketed sections, and all joints, riser sections, and adjustment bricks should be parged with an APWA portland cement mortar on the interior and exterior. The Fosterview Page 12 new storm system should be pressure tested to insure a minimum of leakage from poor installation practices. Comment: These conditions of gasket installation, pressure testing, and the construction /installation practices are to be met during construction as monitored by the owner's engineer and inspected by the City. G. All driveways should be paved. The item of special concern is the joint driveway serving lots 1, 2 and 3, which is shown as about half paved, and no drainage controls along the wall or rockery edge to the north. This driveway should be fully installed as part of the plat improvements, and constructed with a full width paved surface, together with a curb and drainage system to collect surface drainage off the roadway surface. Comment: A drainage system for the combined driveway (lots 1, 2, and 3) needs to be shown on sheet C -8. H. Unanticipated spring interception may be incurred during the roadway and site earthwork excavation. There are numerous, and yet unidentified, springs roughout the project site, which must be collected and directed to the new storm system. There should be a detail for this proposed work on the project plans, showing in advance the proposed collection system of sub drains, the method of backfilling, and provision of monitoring wells for long -term observation. If large springs are encountered under future building sites, this may preclude construction of homes in the precise location shown on the preliminary development plans. Comment: Typical control measures to be used when springs are encountered need to be provided for cut and fill situations, utility trenching situations, home excavations, and other springs situations. I. The development should strictly follow the geotechnical recommendations of the Terra Associates and Applied Geotechnology Inc. firms, as provided in their letters and technical memorandums. We have listed several of the items we believe are of special concern; however, we have not attempted to list all of the recommendations, nor through omission imply that other items should be ignored or carry less weight. Applied Geotech Recommendations: Fosterview Page 13 1. The developer should prepare for review by Terra and the City detailed cross sections in all planned fill areas indicating how the fill will be keyed, benched, and drained as recommended in the geotech report. A typical detail should be prepared illustrating the geotech engineer's recommended key at the toe of all proposed fills on slopes. Calculations supporting adequate safety factors against slope instability should be provided for review by the City. Comment: Not shown or identified on the plans. 2. We suggest the developer, in conjunction with the geotech engineer, prepare detailed design cross - section addressing subdrainage provisions for fills placed on slopes and underlain by lacustrine deposits. Comment: See Shannon and Wilson and previous comments for direction in providing this information. 3. We suggest Terra be requested to review the foundation details and comment on the need for connecting individual footings or supporting the houses on post - tensioned slabs as a possible means of reducing potential for differential settlement of the structures. Comment: This item to be addressed in building permit approval process and foundation approvals. 4. Construction monitoring by the geotech is recommended, with written confirmation of work performed in accordance with the geotechnical recommendations. Comment: The scope of work and contract for the field work will need to be approved by the City prior to issuing a land altering permit due to the significant geotechnical concerns of erosion, stability, and runoff during land altering, construction, and construction completion. The City requires geotechnical daily visits and continuos phone call availability at a minimum to assure stability, erosion control, and runoff control that is expected to require daily engineering direction. Fosterview Page 14 J. It is HCW -L's recommendation that the proposed cuts and rockery work along the existing roadway right -of -way for 42 Ave S (behind lots 1, 2 and 3) also be examined by the geotechnical engineer to insure lateral stability of the existing roadway together with the new road improvements. Comment: See previous comment, page 9, item 7. Page 4. The project should be constructed in phases, with the initial phase limited to the north margin of the new S 137 St, and a new temporary storm line routed from the S 137 St storm system to the discharge point along the north end of 44 Ave S beyond the slide area. This could be aligned either from the new, large detention tanks in the intersection of S 137 PI and S 137 St and then easterly to the new storm system along 44 Ave S or directly north along the S 137 St cul -de -sac to the connection to the existing storm culvert on 44 Ave S. Comment: The plans submitted do not show phasing or sequencing of the construction work. The sequencing plans need to be submitted in order to assure these are addressed. Page 4. The preservation of a buffer of 100 feet in width along the north property line, during the initial phase of construction will preclude construction of any site grading or utilities for lots 1- 21, until the upper portions of the project are fully graded, all utilities installed, and all streets south of S 137 St are paved. Construction work north of S 137 St must be carefully planned and implemented to control erosion and siltation generation from earthwork and utility construction. Comment: The plans do not show or call out this required sequencing and construction requirement. Page 4. We recommend that the road 1111 along the north side of S 137 St be confined as tightly as possible to the road alignment by the use of a geotextile or geogrid reinforced roadway embankment to limit the road fill extension into the downhill, temporary erosion and siltation control natural buffer area until later phases of construction are implemented. Comment: The plans submitted do not address this recommendation. ,,..r _Yy,,,tr..j....f1, m. ,r��'.�tTi.�.. -0x.�v.�.,vf:r .�'.F.'S.. i.;l•Ir. .'.!L.:tfr Fosterview Page 15 : '+Nr.....t.... Page 5. We recommend that the City of Tukwila implement the King County SWDM Manual Chapter 5, Erosion /Sedimentation Control Plan and Practices requirements, specifically emphasizing Preparation of an erosion and sedimentation control plan, site stabilization via stabilization of the construction entrance and construction road, slope pipe drains, subsurface drains, interceptor dikes or berms directing runoff to a stabilized outlet, protection of existing drain ways by the use of check dams, structural stream bank stabilization and sediment trapping, storm drain inlet protection and filter fabric fencing, and cover measures including seeding, netting and matting, and plastic covering. Comment: The plans do not contain these construction elements. Page 5. We recommend that the Foster View Estates project avoid TESCP techniques that encourage infiltration or ponding without heavy bottom liners, because of the high potential for land sliding. , Comment: The liner shown on sheet C -17 appears to be a pervious liner, not an impervious liner. Page 5. We recommend that the project be phased, with only very limited construction disturbance in any area at one time. The following is provided as a guideline to implement the land altering ordinance. The City should require a phasing and sequencing plan /diagram for the total project construction. This should be submitted for City review and approval prior to construction start. A. Construct S 137 ST and in- street utilities, with temporary storm outfall and temporary sanitary sewer to avoid construction in the 100 foot wide northerly buffer. B. Proceed with construction in the three areas of the site uphill and southerly of the S 137 ST corridor: Lots #36 through #41, and Lots #32 through #35, and after these two areas are constructed and stabilized, allow construction on the section of lots #22 through #31. C. After construction of the uphill areas and stabilization and paving is complete, then the two sections of the development below and northerly of S 137 ST can begin for Lots #1 through #21. Fosterview Page 16 D. Limit individual home construction by phasing so only a limited number of sites are in a disturbed state (all site work, drainage, and landscaping (sodded or established grass) is completed) at one time. We suggest that a limit of 3 home sites be allowed to be under construction at one time, in each area defined in Section B and C above. Comment: This phasing plan must be submitted and approved prior to the issuance of a grading permit. Page 5. We do not recommend relocation of a bioswale into the easterly, slide -prone areas of the site. While it may be technically possible for a bioswale to be constructed in this area, we have very strong concerns for the long -term stability of the existing hillside, and we recommend keeping off this slope. Comment: This condition has been addressed on the plans with the exception of the impervious pond liner. Page 6. We also believe that it will be very difficult to sustain any bioswale grass growth in an artificially constructed channel in the wetlands buffer, the north property line location, and along the abandoned 44 Ave S right -of -way, because of the poor sunlight exposure, high natural trees, and the proposed high walls on the southern exposure. We believe that the proposed bioswales will have performances that are unacceptable for long -term water quality protection, and that other techniques such as wet vaults are more appropriate for this project. Comment: The swale location has been adjusted addressing this concern. Page 6. If bioswale methodology is mandated for this project, we recommend that the bioswale(s) be relocated off -site to the S 133 St right -of -way, where more favorable conditions exist for sustaining plant growth and assuring proper maintenance. Comment: Plans have not been developed for regional biofiltration system on S 133 St sso on site biofiltration by Fosterview Estates is required. The July 25, 1995 Terra and Associates Slope Stability Analysis report addresses filling requirements on page 2 in paragraphs 3, 4, 5, and 6. These construction requirements will be requirements for the filling operations and conditions of the land altering permit. The items identified in the September 8, 1995 Shannon and Wilson review need to be addressed and resolved by each item prior to issuing a land altering permit. ....,.,. a,• xJ: �r�tc:. ,��.ns.�.•rel�t <v.:.i�:.�3:7:•: F: K.. lws.-::,: aaxrw:: u. vzK•;.+ cv_^.rMOZrx.:rs�m.:�.,..w+ >.nan u..«.n,.�•�.ox...•.,..,.,w,w Fosterview Page 17 a.. w,.r r.. x^ +.- xanive:Barnesn•.»v.e.,«a...; yaw.. n< wamR .rtw•o,.uarvn.m..n.,e.�.....n« ,..»....+ .............._. The construction phasing and sequencing plans need to quantify and provide control measures for detention during the each of the construction phases. Items in the CCRs need to include: 1. use of privately owned undeveloped land must comply with the geotechnical findings and recommendations; 2. no additional impervious surfaces may be added without drainage system impacts (private lot, whole system) along with hillside stability evaluation being made and finding that there will be no adverse impacts. With the geotechnical findings and recommendations; 3. Homeowners are responsible for maintenance and operation of the french drains and wetlands as well as other private property amenities shown on the plans such as fences.. Public Works comments will be provided on plans showing the construction phasing and sequencing. Sincerely, Ross A, Earnst, P.E. Director of Public Works City of Tukwila cc: John Jimerson . TERRA ASSOCIATES, Inc. Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences Mr. Bill Fowler Dujardin Development Company P.O. Box 5308 Everett, Washington 98206 Subject: Geotechnical Services During Construction Fosterview Tukwila, Washington Dear Bill: RECEIVED MAY 3:01996 TUKWILA PUBLIC WORKS May 29, 1996 Project No. T -1515 This letter presents our anticipated scope of work during earthwork construction of the Fosterview project in Tukwila. For approximately the last six years, we have provided geotechnical support services related to the design of the project. During construction, we anticipate our work will consist of the following items:. 1. Observation of stripping operations to verify that organic soils are removed from building areas. 2. Examination of excavated areas to evaluate the stability of cut slopes as well as the suitability of excavated materials for use in construction of structural fills. 3. Observation and testing of the placement of structural fills. 4. Examining soil conditions at the site during construction to verify that they are consistent with those anticipated when our previous reports were prepared and to provide supplementary recommendations as needed. 5. Observe groundwater seepage and drainage conditions and develop locations and configurations of subsurface drains, as needed. 6. Examine materials brought on the site for structural fills. 12525 Willows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821 -7777 . Bill Fowler ay 29, 1996 7. Observe and test backfill behind retaining walls as well as installation of subsurface drains at various locations on the site as needed. 8. Observe and test structural fills placed behind Keystone walls and verify placement of drainage materials behind these walls. 9. Geotechnical consultation, as needed. Throughout the duration of the project, we will be available to respond to questions pertaining to the geotechnical aspects of this project that might develop at any time. Prior to starting construction, we recommend holding a pre - construction meeting between the various members of the design team so the critical areas of the project can be clearly outlined, the need /frequency of inspections /testing can be clearly defined, and lines of communication can be properly established. We trust this listing of our proposed scope of services for the Fosterview project is sufficient for your needs at this time. Please call if you have any questions or if you need additional information. Sincerely yours, TERRA ASSOCIATES, INC. Anil Butail, P.E. President AB:eb Project No. T -1515 Page No. 2 geotechnical plan review fosterview estates subdivision shannon & wilson Department : ofPublic Works • ®���'SHANNON�WILSON INC. . mow GEOTECHNICAL AND ENVIRONMENTAL CON�ULT.ANTS ANCHORAGE ' SAINT LOUIS • BOSTON September 8, 1995 City of Tukwila :;- Department of Public Works • . ' 6300 Southcenter Boulevard, Suite 100 T1�kwila, Washington. 98188 • Attn: Mr. Ron Cameron '_ . , :. -. RE: GEOTECHNICAL PLAN REVIEW, FOS'rEKVIEW ESTATES SUBDIVISION, TUKWILA, WASHINGTON . • This letter presents our review comments of the plans for the Fosterview Estates Subdivision development. . Our review consisted of Sheets C -1- through C -10, C -15,' C -17, and C -18 of the undated plans prepared by Erich O. Tietze and Associates, Inc: (received by the City of Tukwila on July 31; 1995). As part of our plan review, we also reviewed numerous documents - provided by the City of Thkwila regarding development on this property; • These documents are summarized below. . • . • • Geotechnical letters and reports from Terra Associates, Inc. (Terra), dated August 11, 1990; December 22, 1992; February 23, 1993; June 30, 1993; and July 25, 1995. Review comments from Applied Geotechnology.Inc., dated May 17, 1993. ► Review comments from Hammond Collier & Wade - Livingstone Associates, Inc. (HC &W -L), dated June 28, 1993. The following paragraphs presents our specific comments. Sheet C -2, Thrnporary Erosion Control 1. The construction schedule is very simplified and does not account for all phases of the project (for instance, construction of interceptor ditches and abandonment of sedimentation ponds). Also, construction scheduling may be different during wet and dry seasonal weather. Ideally, earth disturbing activities would be conducted during the summer and the area seeded and mulched to take advantage of the fall rains and cooler weather. Such details should be stated. 2. There are several questions regarding the proposed drainage systems: i0J NORTH 34TH STREET • SUITE 100 P.O. EOX 300303 SEATTLE. WASHINGTON 93103 2206.632.6020 FAX 206.033.6777 TDD: 1.800•833•0388 W- 7111 -01 City of Tukwila Attn: Mx. Ron Cameron September 8, 1995 - Page 2 a. b. SHANNON &WILSON. INC. . The schedule indicates that the drainage system along 43rd Avenue S. should be constructed first. This drainage system apparently includes a detention vault, a wet vault, and a storm drain pipe and requires a maximum excavation of.21 feet.. Erosion control methods should be stated for this 'construction sequence, which includes crossing a stream channel north of S. 137th Street. Explorations near the area of the proposed drainage system indicate that slide debris may be present at shallow depths. In addition,: the explorations do not extend to the planned depth of excavation. • Concerns regarding this. • excavation and the possible effects on the stability of the site should be addressed. Temporary excavation requirements should also be addressed, including slope angles and shoring as appropriate, if there are special . subsurface conditions that will dictate such requirements (versus slopes and shoring dictated by general state and federal safety guidelines). A profile of the storm drain down 43rd Avenue S. should be presented. . When are detention system Nos. 2 and 3 installed in the construction sequence? Is it schedule item (9)? Is the existing 18- inch - diameter CMP that crosses under 43rd Avenue S., north of S. 137th Street, sufficient based on current design standards (considering that. a larger arch culvert is being installed upstream)? 4. Why are the clearing for and construction of rockeries and paths, items (5) and (6), scheduled before the clearing and grading of the site and establishment of erosion control features, such as interceptor trenches? 5. Protection of catch basins, item (11), should be provided during construction of the drainage system, item (9). 6. The extension of S. 137th Street will cross a stream channel, yet there are no erosion and sedimentation control measures proposed. This crossing consists of retaining walls, 7 feet of fill' and placement of an arch culvert, requiring in- stream work. It is assumed that the stream flow will be disrupted by berms and pumps during construction of the culvert. This diversion should be clearly detailed. 7. In addition to crowning the rocked surface of the stabilized construction entrance, consideration should be given to crowning the subgrade to promote better drainage. There are no specifications given for the construction entrance geotextile. W- 7111 -01 City of Tukwila Attn: Mr. Ron Cameron September 8, 1995 Page 3 SHANNON &WILSON. INC. 8. There are several questions regarding the proposed sedimentation ponds: a. Have hydrologic and sedimentation calculations been conducted to size the ponds for sufficient volume and residence time and to specify adequate drainage conduits? These calculations should be' done as a check. • • b. The drawing indicates specific sites and sizes of two. sedimentation ponds. The plan shows the ponds are to be excavated such that the northern excavated .slopes are about 5 feet above .the pond floors and the southern excavated slopes are about 15 feet and 9 feet above the pond floor for the upper and lower ponds; respectively. However, a note indicates that the top of the pond is at both the higher and lower elevations and refers to typical detail on Sheet C -15 (renumbered to Sheet C -17). This note is unclear. Where is the proposed water surface elevation for the ponds? c. As a result of past slope instability north and east of the site, there is concern . that additional subsurface water may reactivate slope movement or cause new failures. Because the explorations do not extend to the bottom of the ponds, there is the possibility that permeable deposits could be encountered. Will • the . ponds be lined with an impermeable liner to prevent any infiltration from occurring, or can it be demonstrated that the pond bottom and side slopes will be impermeable? d. Have stability analyses been completed on the proposed excavations for the ponds? These excavations may be the most critical slopes on the site. Considering that 2.5 Horizontal to 1 Vertical (2.5H:1V) slopes are recommended for permanent grading, why have 2H:1V slopes been used? e. The ponds are sited in areas that are also proposed for houses. When and how will the ponds be abandoned? 9. The project will require about 40,000 cubic yards of excavation and 20,000 cubic yards of fill. Will stripped topsoil and other spoils be retained on site for later use? If some spoils are to be stockpiled temporarily, stockpile areas should be designated and methods to control erosion from the spoils stated. Otherwise, it should be stated that all spoils that are not immediately used shall be removed and placed at a stable area offsite. W- 7111 -01 City of Tukwila Attn: Mr. Ron Cameron September 8, 1995 Page 4 SHANNON &WILSON. INC. 10. There are several comments regarding interceptor ditches: a.::..... -. Interceptor ditches should be located so that they intercept water from slopes and discharge it to the . sedimentation ponds at a point opposite from the pond outlet, to increase the residence time of the sediment laden water. (This is • schematically illustrated on Sheet C -17, but not indicated on Sheet C -2). Consideration should be given to installing lateral interceptor ditches across the long, .uninterrupted slope on lots 29 through 35 in the southwest corner of the project site and across .lots 18 through 21.: . . .. . All the ditches are shown discharging onto the upper excavated slope of the ponds. Is this where the pond water surface is? If not, should the ditches continue downslope to the expected pond water surface? c. The interceptor ditches discharge to culverts under street crossings at two sites. •Specifications for culvert diameters and catch basins should be detailed. • The silt fence detail does not provide specifications for the filter fabric. Consideration should be given to adding silt fences in the following locations: along the west edge of lot 36, along the east edge of lot 41, on the upstream side of the S. 137th ,Street stream crossing, and along the east edge of lots 32 to 35. 12. There are no erosion control or drainage measures indicated on the northern, downslope edge of lots 36 to 41. As shown, sediment and water from these disturbed areas may discharge to the ditch along 44th Avenue S. 13. Straw bales are shown in the stream channel downstream of the S. 137th Street stream crossing and as barriers in the sedimentation ponds. Straw bales normally do not perform well when repeatedly or constantly saturated and consideration should be given to not using these devices in these locations. 14. The catch basin protection details are inadequate. Presumably, the catch basins are set in asphalt paved streets. Should silt fence barrier structures be buried through asphalt? A pile of gravel over the catch basin will only divert water around the basin and downslope to the next basin. There is no filter fabric (geotextile) specification provided for the catch basin protection detail. 15. There is no drainage measure indicated for the waterway across the new concrete walkway west of 44th Ave. S. in the southeast corner of the site. W- 7111 -01 City of Tukwila Attn: Mr. Ron Cameron September 8, 1995 Page 5 Sheet C -3, Final Grading Plan and Sheet C -4, Cut and Fill SHANNON &WILSON. INC. 1. , Note (2) under grading procedures indicates that stripped topsoil may be reused as berms. Does this include berms for sedimentation control ponds? In our opinion, this is not a suitable use of topsoil. Also, please refer to our comment number 9 for Sheet C -2, regarding stockpiling of on -site soils. • 2. Is note (4) meant to imply that only clean import fill can be used? Our review comments regarding several of the additional notes and details on the plans are dependent on the gradation of structural fill that will be used. This note is vague and should be reworded to state its precise meaning. 3.. Note (4) indicates keying and benching for slopes greater than 23 percent, whereas notes (5) and (6) indicate keying for slopes greater than 25 percent. These notes should be changed to be consistent. . If structural fill will consist of on -site soils or imported silty soils, it is our opinion ::.that the key and bench details are inadequate. _Based on the documents provided to _-: us, *there appears .to be a great concern for seepage during construction.. If this is the case, additional-drainage measures may be needed, such as blanketing the key. • . Additional-drainage measures should be considered by Terra by backfilling the benches with a similar clean material and providing perforated pipes to collect seepage.•: Regardless, consideration should be given to excavating the benches with a slight downward slope (approximately 0.5 percent). 5. The December 22, 1992, geotechnical report by Terra recommends that, "In the northern portion of the site, fills placed on the steep slopes should be minimized and should not be more than five feet thick." However, Sheet C -3 indicates that up to 17 feet of fill will be placed north of S. 137th Street (lots 1 through 8). Is this • acceptable to Terra? If so, they should provide a written letter indicating acceptance of this change from the recommendations in their referenced geotechnical report. • 6. Has the rockery shown on the "key and bench detail with rockery" been designed to withstand the earth pressures from a 2.5H:1V backslope? 7. Based on our review of the proposed grading plan, it appears that Terra may not have analyzed the most critical slope conditions in their July 25, 1995, report. For instance: the 12- foot -deep maximum excavations in the area of lots 36 through 41 may be more critical, especially considering the proximity to the landslide deposits encountered in nearby explorations; there will be a 20 -foot -deep excavation in the area of lots 22 through 31 that has not been analyzed; and the retaining wall for the W- 7111 -01 City of Tukwila Attn: Mr. Ron Cameron September 8, 1995 Page 6 SHANNON &WILSON. INC. drive to lots 1 through 3 will require the placement of 17 feet of fill in an area Terra noted as containing steep slopes where "fill soils ... should be minimized." Also, Terra should analyze temporary conditions required for 25 -foot maximum excavations for detention systems and sedimentation ponds. In addition, the soil strengths assumed in Terra's analyses appear high. For example: the stability of structural fill' was assigned a friction angle of 39 degrees, which in our opinion is high, especially if on -site soils are used as structural fill; the strength of the silty sands and the sandy silts /lean clays does not consider any lower strength weathered zone's; and assigning cohesion to the hard clays may not be appropriate if they are blocky and fully softened strengths exist. We recommend that Terra provide additional clarification and address these issues to ensure that grading will not decrease site stability. Particular focus should be placed on excavating into the hard, blocky, clay and placing fill on top of weathered native soils or landslide deposits. 8. Sheet C -4 should add a shading in the legend where keying and benching will be required (at slopes greater than 25 percent) so that there is no disagreement between the contractor, the developer, and the City of Tukwila during construction. In their July 25, 1995, report, Terra recommends that granular fill be placed for a _. • distance extending 40 feet back from the toe of the slope along the northern part of .the site. We assume this means using clean, granular soils. Yet there is no such • distinction made on Sheets C -3 and C-4. If clean, granular fill will be used for all structural fill,. there is no need for such a distinction. As mentioned in comment 2 above, additional *clarification is needed regarding structural fill specifications. 10. Details are needed regarding rockery construction, including provisions for drainage behind the walls. 11. Because excavations for sedimentation ponds and detention systems will extend 10 to 15 feet below the bottom of the explorations, it is our opinion that Terra should discuss the implication of the depths of the explorations in regard to the depth of the proposed excavation. . Sheet C -6, Retaining Wall Profiles 1. . What type of retaining walls will be constructed? Have or will shop drawings for these walls be reviewed by the City? City of Tukwila Attn: Mr. Ron Cameron September 8, 1995 Page 7 2. SHANNON F&WILSON. INC. Soft and /or loose soils may be encountered at the base of the wall that crosses over the major stream course. Overexcavation may be required at this location. Will any scour protection be provided around the wall at the culvert crossing? Sheet C -8, Drainage Plan 1. In their rune 28; 1993, letter, HC&W-L recommended that French drains be installed on lots in cut sections. We agree with this recommendation. 2. ' • Will perimeter foundation drains will be installed around each structure? 3. Consideration should be given to lining the biofiltration swale along 43rd Avenue S. to reduce infiltration into the subsurface soils in an area where past landsliding has occurred. Sheet C -9, Detention. System No. 1 Details ferences to detention system No 2 and wet vault No 2 should be changed to No 1. Sheet C -17; Details and Notes 3. The diameter of the pond outlets are not specified. What material are the pipes? Are they buried or on the surface? .;'Sheet. C -17 indicates that emergency spillways should be constructed for each pond. These should be shown on Sheet C -2. Rock that is 2 to 4 inches in diameter is specified as spillway riprap. Is the size of this rock based on the anticipated velocities over the spillway? The developer's geotechnical engineer should check the size of the rock to confirm that it is appropriate. Is the existing culvert at the end of 43rd Avenue S. of sufficient size to carry the flow from both ponds? 4. The erosion control measures at the inlet to the ponds should be expanded and more detailed. Our review comments were prepared for specific application to the project at this site as related to the geotechnical aspects discussed herein. Within the limitations of scope, W- 7111 -01 City of Tukwila Attn: Mr. Ron Cameron •' September 8, 1995 Page 8. SHANNON &WILSON, INC. schedule and budget, our review was completed in accordance with generally accepted .....-,-T:have any questions concerning our comments or require additional clarification, please call -• either of the undersigned. • Sincerely, • • .• SHANNON & WILSON, ]NC.. 't • • 1 .■ ., • 6k- :A0 _ • . • • . . • • • - . • • • • ••• • ",- . . • • • • • • • • • • , • • • . . • . • • • • • • • W7111-01 .LTR/W7111-I kdflkd • .• • W-7111-01 .. • ` 92 -o 8 TERRA ASSOCIATES, Inc. in Geotechnical Engineering, Geology �. and Environmental Earth Sciences Mr. Bill Fowler Dujardin Development Company P.O. Box 5308 Everett, Washington 98206 Subject: Slope Stability Analyses Fosterview Tukwila, Washington Dear Mr. Fowler: July 25, 1995 Project No. T -1515 RECEIVED CITY OF TUKWILA JUL 251995 PERMIT CENTER RECEIVED JUL 2 51995 TUKWILA PUBLIC WORKS As requested, we evaluated slope stability at the Fosterview project. We analyzed conditions at three locations on the site. These locations were selected based on the areas where significant amounts of fills will be placed on sloping portions of the property. A vicinity map of the project is presented on Figure 1 and the locations of the cross - sections analyzed are shown on Figure 2. This figure also shows the planned grading on the site. As shown on the drawing, fills with a maximum height of about 12 feet will be placed. The greatest thickness of fills will be placed in the northern portion of the site. Figures 3 through 6 show the cross - sections analyzed. These cross - sections identify the existing ground surface and the proposed zone of fill placement. In addition, they also show the various soil layers assumed and analyzed in our computations. We previously conducted geotechnical studies for this project and presented discussions of the subsurface conditions in our reports dated August 11, 1990 and December 22, 1992. Since 1990, we have also provided consultation services to you and your other consultants in the planning and design of this project. Based on our review of the subsurface information presented in our previous reports, we assigned properties to the various soil layers underlying the site as well as the structural fills to be placed on the site. These soil properties are shown on Table A. 12525 Willows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821 -7777 Mr. Bill Fowler July 25, 1995 We conducted our analyses using the computer program PCSTABL6. Using this computer program and analysis of numerous potential failure surfaces, we established the safety factors shown on Table B. As shown on Table B, the minimum safety factor obtained was 1.60. Current geotechnical practices in our area suggest a minimum safety factor of 1.5 under static conditions. Considering that the minimum safety factors computed are all greater than 1.5, it is our opinion that the slopes on the site are currently stable and will remain stable after construction, provided our recommendations are incorporated into project design and construction. We also reviewed conditions behind Lots 1 through 3 where rockeries up to about four feet high will be constructed. A sidewalk and the 42nd Avenue South roadway will be constructed adjacent to this rockery. With the planned maximum height of four feet, use of a rockery is appropriate at this location. The rockery must be provided with a continuous subsurface drain and should be constructed in accordance with Association of Rockery Contractors (ARC) standards. The excavated soil face should be examined by our personnel. If unsuitable materials are observed, they should be removed to a depth equal to the wall height and replaced by structural fill. In construction of the fills, we recommend using the more granular soils encountered in the central part of the site as far as possible. Along the northern part of the site, if granular fills can not be obtained from on -site sources, we recommend placing a zone of imported granular fill extending 40 feet back from the toe of the slope. The toes of all fills should be provided with subsurface drains, which should discharge by gravity into the storm sewer system. The on -site materials are moisture - sensitive and will be very difficult to work in wet weather. Therefore, we recommend that earthwork be performed during the dry summer and early fall months. If wet weather occurs during earthwork construction, you should seal all work areas and/or import granular soils to complete the earthwork. Prior to fill placement, the ground surface in proposed fill areas should be stripped of all surface vegetation and near - surface topsoil. A key should be excavated at the toe of all fill areas. The key should have a minimum depth of four feet below grade and should have a minimum width of ten feet. A drain should be incorporated into the upslope portion of this key and should be discharged by gravity to the storm drain system. Upslope of the key, the ground surface should be prepared in horizontal benches. These benches should be roughly as wide as the equipment used to prepare them. The surface of these benches should be scarified and recompacted to the requirements for structural fill. Once this has been done, structural fills may be placed to construct the fill slopes. Structural fills should be placed in layers less than 12 inches thick and each layer should be compacted to a minimum of 95 percent of the maximum density as determined by ASTM Test Designation D -698 (Standard Proctor). Upon completion of the fill placement, all finished slopes should be tamped with a roller. The finished slope surfaces should be planted with an appropriate species of vegetation to provide continuous ground cover and to retard erosion. Project No. T -1515 Page No. 2 I s .1 R Ifi S Wirt_ ,.1_2_,1 _ q; ` 1 I ::14iW R t.l ffir ;1•C‘... 1--[1.1 .115 $ ~I Nil: e.. ,nt■�',jS i v. J, )6 —i '.pul St s Ito �— si(t - _ %t'__1Nst 4. ST 9 a(� S 12DTM •4111 7 "13.,I.1 v S 13: tBLAel< BIVI REFERENCE: THE THOMAS GUIDE, KING COUNTY, WASHINGTON, PAGES 625 AND 655, 1995 EDITION. TERRA ASSOCIATES Geotechnical Consultants VICINITY MAP FOSTERVIEW ESTATES TUKWILA, WASHINGTON Proj. No. 1515 1 Date 7/95 I Figure 1 Anil Butail,'''°•}; President AB:eb EXPIRES 12. / 9 / C? s. 7 -23 0� Encl: Figure 1- Vicinity Map Figure 2 - Exploration Location Plan Figures 3 through 6 - Geologic Sections Table A -Soil Parameters Table B - Results of Stability Analysis Sections - Sections A -A through D -D Calculations - Sections A -A through D -D Project No. T -1515 Page No. 3 TP -16 WACO a r. tql &YAM ,,, t.a. atrutmt • 9411 ti TP -2 APPROXIMATE SCALE loo o loo 200 feet LEGEND; Si APPROXIMATE TEST PIT LOCTION �--- -1 TYPICAL GEOLOGIC SECTION LINE (SEE FIGURES 3 THROUGH 6) REFERENCE: CUT AND FILL PLAN FOR FOSTERVIEW ESTATES PROVIDED BY ERICH 0. TIETZE AND ASSOCIATES, INC., JOB NUMBER UNKNOWN, UNDATED. �� ,I.‘ 0 :err•; i ; TP -9 '°n T—..-L_ •.,' ,TRM..� ....�.. _. \'.11 . TERRA. ASSOCIATES ''otechnicol Consultonts • 4 TERRA ■ ���` "� ASSOCIATES Geotechnical Consultants EXPLORATION LOCATION PLAN FOSTERVIEW ESTATES TUKWILA, WASHINGTON Proj. No. 1515 I Date 7/95 I Figure 2 - ._. •• 0 20 40 60 1 silty fine SAND to fine sandy SILT (loose to medium den; . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 100 • SILT /CLAY, i very hard • 1.20 140 SCALE: 1 inch = 20 feet 160 180 200 r�� ASSOCIATES Geotechnical'Consultants TERRA STRUCTURAL FILL silty fine SAND to fine sandy SILT (loose to medium dense < 6', very dense .> 6') SILT /CLAY,.. very hard • 120 140 • 160 180 200 = 20 feet 220 240 • 260 TERRA ... ASSOCIATES • • 'otechnical 'Consultants GEOLOGIC SECTION A -A' FOSTERVIEW ESTATES TUKWILA, WASHINGTON Proj. 'No. 1515 ; 'Date 7/95 ' I Figure 3 '� .......__... 280 — 260 — a) 240 — z 0 - L221 220 — 200 — 0 • • N • 4— • 0 CO • • • 1— • • STRUCTURAL FILL (loose < 2'•, dense > 2' silty fine SAND hard SILT . . x x 20 40 60 . 80 100 120 140 160 180 20( SCALE: 1 inch = 20 feet • r «. TERRA •..•. ASSOi •�' otechnical U•CTURAL FILL ' ' silty f►ne SA M • (loose < 2'., dense .> 'hard SILT . • • . . . . . ... . . . . • ... • • • • . . ................ .... • • • • • • 140 160 180 inch . = 20 feet 200 220 240 260 280 TERRA ASSOCIATES •Geotechnical Consultants GEOLOGIC SECTION B —B' FOSTERVIEW ESTAT:S TUKWILA, WASHINGTON Proj. No. 1515 1 Dote 7/95 I Fiyure 4 .. .�.�. «.,.....,...._ ELEVATION (feet) 200 -- 180 — 160 — 140 — 100 a) • (D.. .LO . 0 . •I• o Bondy S1� � \O °Se 9' SAND t STRUCTURAL FILL 0 20 40 60 SILT /lean CLAY, hard 80 SCALE: 100 120 140 inch = 20 feet 160 180 TERRA •�� ASSOCIATES 'otechnical Consultants • C a) C• r, •. 4. • 0• dense . e9se . STRUCTURAL FILL 5 to 3 SILT /lean CLAY, hard .; CUT 120 140 160 180 200 inch = 20 feet • TERRA • ASSOCIATES 'otechnical Consultants GEOLOGIC SECTION C —C' FOSTERVIEW ESTATES TUKWILA, WASHINGTON Proj. No 1515 Date 7/95 Figure __... .�_._.............���....,.. 150 — 140 - 130 0 120 w 110 100 90 STRUCTURAL FILL 5 to loose to dense .`loose. 1 to Bondy SI`� silty S�'N° hard SILTS and CLAYS 10 20 30 40 50 60 70 80 SCALE: 1 inch = 10 feet 90 100 TERRA •••..•. ASSOCIATES eotechnical Consultant .. ;, .. — TP- I5(offset) STRUCTURAL FILL 15 t0 3 iti t0 dense 1t s . CIO °se -d SILTS and CLAYS D 60 70 80 1 inch = 10 feet 90 100 110 120 130 140 1 ..: 1.1 • TERRA •ASSOCIATES "otechnical Consultants GEOLOGIC SECTION D -D' FOSTERVIEW ESTATES TUKWILA, WASHINGTON Proj. No. 1515 Date 7/95 1 Figure 6 TABLE A SOIL PARAMETERS USED IN STABILITY ANALYSIS Fosterview Tukwila, Washington Soil Type Unit Weight (pcf) Cohesion (psf) Friction Angle (degrees) Silty Sands 125 0 38 Sandy Silts/ Lean Clays 115 250 28 Structural Fill 125 0 39 Notes: pcf - pounds per cubic foot psf - pounds per square foot TABLE B RESULTS OF STABILITY ANALYSIS Fosterview Tukwila, Washington Notes: A horizontal acceleration of 0.15g was used for the stability analysis for seismic conditions Project No. T -1515 Factors of Safety (Modified Bishop Method) Section Static Seismic (Pseduostatic) A -A' 1.67 1.20 B -B' 2.79 1.65 C -C' 2.92 1.82 D -D' 1.60 1.20 Notes: A horizontal acceleration of 0.15g was used for the stability analysis for seismic conditions Project No. T -1515 4J 9-- X >-- 0 ,0 4 J N N ('1 m 0 U) N (D (t) N s-1 CrI Section A—A 7//%/%1 -. 0 31.25 62.50 93.75 125.00 156.25 187.50 218.75 250.00 X AXIS (ft) (pyl r s 0 39.00 78.00 117.00 156.00 195.00 234.00 273.00 312.00 X -- AXIS (ft) 0 26.00 r- 911M4,034. 52.00 78.00 7/11M--- 104.00 130.00 156.00 182.00 208.00 X - AXIS (ft) r -- 0 Section D -D 7/19 /9 s. �•S =I.6U 17.87 35.75 53.62 71.50 89.37 107.25 125.12 143:00 X -- 'AXIS (ft) , SLOPE STABILITY ANALYSIS SECTION A -A ** PCSTABL6 ** by Purdue University modified by Peter J. Bosscher. University of Wisconsin- Madison - -Slope Stability Analysis- - Simplified Janbu, Simplified Bishop or Spencer's Method of Slices PROBLEM DESCRIPTION Section A -A BOUNDARY COORDINATES 9 Top Boundaries 15 Total Boundaries Boundary X -Left Y -Left X -Right Y -Right Soil Type No. (ft) (ft) (ft) (ft) Below Bnd 1 0.00 14.00 20.00 20.00 1 2 20.00 20.00 28.00 24.00 1 3 28.00 24.00 67.50 35.00 1 4 67.50 35.00 68.00 40.00 1 5 68.00 40.00 100.00 52.00 1 6 100.00 52.00 124.00 58.00 1 7 124.00 58.00 146.00 60.00 1 8 146.00 60.00 228.00 60.00 1 9 228.00 60.00 250.00 62.00 2 10 67.50 35.00 76.00 38.00 2 11 76.00 38.00 120.00 42.00 2 12 120.00 42.00 166.00 50.00 2 13 166.00 50.00 178.00 54.00 2 14 178.00 54.00 228.00 60.00 2 15 28.00 24.00 250.00 24.00 3 ISOTROPIC SOIL PARAMETERS 3 Type(s) of Soil Soil Total Saturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface No. (pcf) (pcf) (psf) (deg) Param. (psf) No. 1 125.0 130.0 0.0 39.0 0.00 0.0 1 2 125.0 130.0 0.0 38.0 0.00 0.0 1 3 115.0 115.0 250.0 28.0 0.00 0.0 1 A Critical Failure Surface Searching Method, Using A Random Technique For Generating Circular Surfaces, Has Been Specified. 100 Trial Surfaces Have Been Generated. 10 Surfaces Initiate From Each Of 10 Points Equally Spaced Along The Ground Surface Between X = 20.00 ft. and X = 60.00 ft. Each Surface Terminates Between X = 77.00 ft. and X = 150.00 ft. Unless Further Limitations Were Imposed, The Minimum Elevation At Which A Surface Extends Is Y = 10.00 ft. 5.00 ft. Line Segments Define Each Trial Failure Surface. Following Are Displayed The Ten Most Critical Of The Trial Failure Surfaces Examined. They Are Ordered - Most Critical First. * * Safety Factors Are Calculated By The Modified Bishop Method * * Failure Surface Specified By 11 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 46.67 29.20 2 51.65 29.62 3 56.58 30.42. 4 61.45 31.59 5 66.21 33.12 6 70.84 35.01 7 75.31 37.24 8 79.60 39.81 9 83.69 42.69 10 87.55 45.87 11 90.05 48.27 Circle Center At X = 43.6 ; Y = 95.3 and Radius, 66.2 * ** 1.668 * ** Failure Surface Specified By 14 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 37.78 26.72 2 42.73 27.44 3 47.64 28.36 4 52.51 29.50 5 57.33 30.83 6 62.09 32.37 7 66.77 34.11 8 71.38 36.05 9 75.91 38.17 10 80.34 40.49 11 84.67 42.99 12 88.89 45.68 13 92.99 48.54 14 95.14 50.18 Circle Center At X = 23.3 ; Y = 144.1 and Radius, 118.3 * ** 1.767 * ** Failure Surface Specified By 13 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 42.22 27.96 2 47.20 28.41 3 52.15 29.14 4 57.05 30.14 5 61.88 31.42 6 66.64 32.96 7 71.30 34.77 8 75.86 36.83 9 80.29 39.14 10 84.59 41.70 11 88.73 44.49 12 92.72 47.51 13 96.44 50.67 Circle Center At X = 36.6 ; Y = 117.5 and Radius, 89.7 * ** 1.768 * ** Failure Surface Specified By 11 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 51.11 30.44 2 56.10 30.07 3 61.09 30.31 4 66.02 31.15 5 70.81 32.59 6 75.39 34.60 7 79.69 37.14 8 83.65 40.19 9 87.22 43.70 10 90.33 47.61 11 90.93 48.60 Circle Center At X = 56.6 ; Y = 71.2 and Radius, 41.1 * ** 1.782 * ** Failure Surface Specified By 12 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 37.78 26.72 2 42.77 26.49 3 47.77 26.72 4 52.72 27.43 5 57.58 28.59 6 62.31 30.21 7 66.87 32.26 8 71.21 34.74 9 75.31 37.61 10 79.11 40.85 11 82.60 44.44 12 83.79 45.92 Circle Center At X = 42.8 ; Y = 79.7 and Radius, 53.2 * ** 1.915 * ** Failure Surface Specified By 12 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 42.22 27.96 2 47.15 27.09 3 52.14 26.80 4 57.13 27.09 5 62.05 27.96 6 66.84 29.41 7 71.42 31.40 8 75.75 33.92 9 79.75 36.92 10 83.37 40.37 11 86.56 44.21 12 88.91 47.84 Circle Center At X = 52.1 ; Y = 69.5 and Radius, 42.7 * ** 1.982 * ** Failure Surface Specified By 19 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 33.33 25.49 2 38.30 26.05 3 43.25 26.76 4 48.18 27.62 5 53.08 28.62 1 1 i 6 57.94 29.76 7 62.77 31.05 8 67.56 32.49 9 72.31 34.06 10 77.01 35.77 11 81.65 37.62 12 86.24 39.61 13 90.77 41.73 14 95.23 43.99 15 99.62 46.38 16 103.94 48.89 17 108.19 51.54 18 112.35 54.30 19 114.07 55.52 Circle Center At X = 16.8 ; Y = 193.6 and Radius, 169.0 * ** 1.985 * ** Failure Surface Specified By 15 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 55.56 31.67 2 60.55 31.88 3 65.53 32.36 4 70.47 33.13 5 75.36 34.17 6 80.18 35.49 7 84.93 37.07 8 89.57 38.92 9 94.11 41.03 10 98.51 43.39 11 102.78 45.99 12 106.90 48.83 13 110.85 51.90 14 114.62 55.18 15 115.27 55.82 Circle Center At X = 54.4 ; Y = 120.5 and Radius, 88.8 * ** 2.041 * ** Failure Surface Specified By 19 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 33.33 25.49 2 38.31 24.98 3 43.30 24.75 4 48.30 24.80 5 53.29 25.13 6 58.26 25.73 7 63.18 26.60 8 68.05 27.75 9 72.84 29.16 10 77.55 30.84 11 82.16 32.77 12 86.66 34.96 13 91.03 37.39 14 95.26 40.06 15 99.33 42.96 16 103.24 46.08 17 106.97 49.41 18 110.51 52.94 19 112.46 55.11 Circle Center At X = 44.9 ; Y = 115.1 and Radius, 90.4 . * ** 2.117 * ** Failure Surface Specified By 19 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 42.22 27.96 2 47.22 27.69 3 52.22 27.68 4 57.21 27.90 5 62.19 28.38 6 67.14 29.10 7 72.04 30.06 8 76.89 31.27 9 81.68 32.71 10 86.39 34.39 11 91.01 36.30 12 95.53 38.44 13 99.94 40.79 14 104.23 43.36 15 108.39 46.14 16 112.40 49.13 17 116.26 52.30 18 119.96 55.67 19 121.71 57.43 Circle Center At X = 50.1 ; Y = 128.8 and Radius, 101.1 * ** 2.147 * ** 1 } 1 4 3 1 SLOPE STABILITY ANALYSIS SECTION B -B ** PCSTABL6 ** by Purdue University modified by Peter J. Bosscher University of Wisconsin- Madison -Slope Stability Analysis- - Simplified Janbu, Simplified Bishop or Spencer's Method of Slices PROBLEM DESCRIPTION B - B BOUNDARY COORDINATES 9 Top Boundaries 14 Total Boundaries Boundary X -Left Y -Left X -Right Y -Right Soil Type No. (ft) (ft) (ft) (ft) Below Bnd 1 0.00 42.00 22.00 48.00 3 2 22.00 48.00 32.00 52.00 2 3 32.00 52.00 58.00 58.00 2 4 58.00 58.00 108.00 70.00 1 5 108.00 70.00 158.00 76.00 1 6 158.00 76.00 196.00 78.00 1 7 196.00 78.00 240.00 84.00 1 8 240.00 84.00 276.00 86.00 1 9 276.00 86.00 312.00 88.00 2 10 58.00 58.00 126.00 66.00 2 11 126.00 66.00 144.00 70.00 2 12 144.00 70.00 268.00 84.00 2 13 268.00 84.00 276.00 86.00 2 14 22.00 48.00 312.00 84.00 3 ISOTROPIC SOIL PARAMETERS 3 Type(s) of Soil Soil Total Saturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface No. (pcf) (pcf) (psf) (deg) Param. (psf) No. 1 125.0 130.0 0.0 32.0 0.00 0.0 1 2 125.0 130.0 0.0 34.0 0.00 0.0 1 3 115.0 115.0 250.0 28.0 0.00 0.0 l A Critical Failure Surface Searching Method, Using A Random Technique For Generating Circular Surfaces, Has Been Specified. 100 Trial Surfaces Have Been Generated. 10 Surfaces Initiate From Each Of 10 Points Equally Spaced Along The Ground Surface Between X = 20.00 ft. and X = 50.00 ft. Each Surface Terminates Between X = 100.00 ft. and X = 140.00 ft. Unless Further Limitations Were Imposed, The Minimum Elevation At Which A Surface Extends Is Y = 5.00 ft. 10.00 ft. Line Segments Define Each Trial Failure Surface. Following Are Displayed The Ten Most Critical Of The Trial Failure Surfaces Examined. They Are Ordered - Most Critical First. * * Safety Factors Are Calculated By The Modified Bishop Method * * Failure Surface Specified By 9 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 43.33 54.62 2 53.28. 55.62 3 63.18 57.02 4 73.02 58.81 5 82.79 60.98 6 92.45 63.53 7 102.01 66.47 8 111.45 69.77 9 113.78 70.69 Circle Center At X = 22.7 ; Y = 307.9 and Radius, 254.1 * ** 2.791 * ** Failure Surface Specified By 11 Coordinate Points Point X -Surf No. (ft) Y -Surf (ft) 1 30.00. 51.20 2 39.88 52.78 3 49.72 54.51 4 59.54 56.40 5 69.33 58.45 6 79.08 60.66 7 88.80 63.02 8 98.48 65.54 9 108.12 68.21 10 117.71 71.04 11 118.38 71.25 Circle Center At X = -63.6 ; Y = 668.8 and Radius, 624.6 * ** 2.818 * ** Failure Surface Specified By 8 Coordinate Points Point X -Surf Y -Surf No. (ft) (fl) 1 46.67 55.38 2 56.63 54.57 3 66.63 54.96 4 76.50 56.53 5 86.12 59.27 6 95.34 63.14 7 104.03 68.08 8 105.97 69.51 Circle Center At X = 58.4 ; Y = 138.2 and Radius, 83.7 * ** 2.967 * ** Failure Surface Specified By 12 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 26.67 49.87 2 36.65 50.38 3 46.62 51.23 4 56.55 52.41 5 66.43 53.92 6 76.26 55.76 7 86.03 57.92 8 95.71 60.41 9 105.31 63.23 10 114.80 66.36 11 124.19 69.81 12 131.67 72.84 Circle Center At X = 16.3 ; Y = 349.1 and Radius, 299.4 * ** 3.049 * ** Failure Surface Specified By 10 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 40.00 53.85 2 49.99 53.31 3 59.98 53.46 4 69.95 54.31 5 79.83 55.84 6 89.58 58.05 7 99.16 60.93 8 108.51 64.47 9 117.60 68.64 10 123.49 71.86 Circle Center At X = 52.8 ; Y = 197.9 and Radius, 144.6 * ** 3.077 * ** Failure Surface Specified By 10 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 50.00 56.15 2 59.96 55.28 3 69.96 55.23 4 79.93 56.01 5 89.81 57.59 6 99.52 59.99 7 109.00 63.17 8 118.18 67.12 9 127.01 71.81 10 127.92 72.39 Circle Center At X = 65.6 ; Y = 176.9 and Radius, 121.7 * ** 3.221 * ** Failure Surface Specified By 11 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 46.67 55.38 2 56.65 55.95 3 66.61 56.84 4 76.54 58.06 5 86.42 59.60 6 96.24 61.46 7 106.00 63.64 8 115.68 66.15 9 125.28 68.96 10 134.78 72.09 11 139.33 73.76 Circle Center At X = 34.4 ; Y = 360.7 and Radius, 305.6 * ** 3.256 * ** Failure Surface Specified By 11 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 26.67 49.87 2 36.66 49.65 3 46.66 50.05 4 56.61 51.05 5 66.48 52.66 6 76.23 54.87 7 85.83 57.67 8 95.24 61.06 9 104.43 65.01 10 113.35 69.51 11 115.80 70.94 Circle Center At X = 35.2 ; Y = 213.4 and Radius, 163.7 * ** 3.390 * ** Failure Surface Specified By 11 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 23.33 48.53 2 33.30 47.67 3 43.30 47.61 4 53.27 48.34 5 63.15 49.88 6 72.88 52.19 7 82.39 55.28 8 91.62 59.12 9 100.52 63.68 10 109.03 68.94 11 110.94 70.35 Circle Center At X = 39.1 ; Y = 172.5 and Radius, 125.0 * ** 3.408 * ** Failure Surface Specified By 12 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 20.00 47.45 2 29.98 48.06 3 39.93 49.06 4 49.84 50.45 5 59.68 52.22 6 69.44 54.38 7 79.12 56.91 8 88.68 59.82 9 98.13 63.11 10 107.44 66.76 11 116.60 70.77 12 117.31 71.12 Circle Center At X = 9.4 ; Y = 303.0 and Radius, 255.8 * ** 3.445 * ** slope stability analysis section c-c * * PCSTABL6 ** by Purdue University modified by Peter J. Bosscher University of Wisconsin- Madison - -Slope Stability Analysis- - Simplified Janbu, Simplified Bishop or Spencer's Method of Slices PROBLEM DESCRIPTION C - C BOUNDARY COORDINATES 8 Top Boundaries 12 Total Boundaries Boundary X -Left Y -Left X -Right Y -Right Soil Type No. (ft) (ft) (ft) (ft) Below Bnd 1 0.00 54.00 34.00 54.00 3 2 34.00 54.00 47.00 64.00 2 3 47.00 64.00 78.00 70.00 2 4 78.00 70.00 132.00 84.00 1 5 132.00 84.00 150.00 84.00 1 6 150.00 84.00 166.00 84.00 2 7 166.00 84.00 180.00 86.00 2 8 180.00 86.00 208.00 90.00 3 9 78.00 70.00 128.00 78.00 2 10 128.00 78.00 150.00 84.00 2 11 34.00 54.00 108.00 68.00 3 12 108.00 68.00 180.00 86.00 3 ISOTROPIC SOIL PARAMETERS 3 Type(s) of Soil Soil Total Saturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface No. (pcf) (pcf) (psf) (deg) Param. (psf) No. 1 125.0 130.0 0.0 39.0 0.00 0.0 1 2 125.0 130.0 0.0 38.0 0.00 0.0 1 3 115.0 115.0 250.0 28.0 0.00 0.0 1 A Critical Failure Surface Searching Method, Using A Random Technique For Generating Circular Surfaces, Has Been Specified. 100 Trial Surfaces Have Been Generated. 10 Surfaces Initiate From Each Of 10 Points Equally Spaced Along The Ground Surface Between X = 0.00 ft. and X = 47.00 ft. Each Surface Terminates Between X = 78.00 ft. and X = 166.00 ft. Unless Further Limitations Were Imposed, The Minimum Elevation At Which A Surface Extends Is Y = 10.00 ft. 5.00 ft. Line Segments Define Each Trial Failure Surface. Following Are Displayed The Ten Most Critical Of The Trial Failure Surfaces Examined. They Are Ordered - Most Critical First. * * Safety Factors Are Calculated By The Modified Bishop Method * * Failure Surface Specified By 12 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 36.56 55.97 2 41.56 55.88 3 46.55 56.15 4 51.51 56.79 5 56.41 57.78 6 61.23 59.12 7 65.93 60.80 8 70.51 62.82 9 74.93 65.16 10 79.16 67.82 11 83.20 70.77 12 84.17 71.60 Circle Center At X = 40.2 ; Y = 125.2 and Radius, 69.3 * ** 2.917 * ** Failure Surface Specified By 27 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 10.44 54.00 2 15.25 52.61 3 20.10 51.42 4 25.01 50.44 5 29.95 49.66 6 34.91 49.10 7 39.90 48.74 8 44.90 48.59 9 49.90 48.66 10 54.89 48.93 11 59.87 49.41 12 64.82 50.11 13 69.74 51.01 14 74.61 52.11 15 79.44 53.42 16 84.21 54.94 17 88.90 56.65 18 93.53 58.55 19 98.06 60.65 20 102.51 62.94 21 106.85 65.42 22 111.09 68.07 23 115.21 70.90 24 119.21 73.90 25 123.08 77.07 26 126.81 80.40 27 129.99 83.48 Circle Center At X = 45.9 ; Y = 167.4 and Radius, 118.8 *** 2.937 * ** Failure Surface Specified By 16 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 26.11 54.00 2 30.84 52.39 3 35.71 51.22 4 40.65 50.50 5 45.65 50.26 6 50.64 50.47 7 55.60 51.15 8 60.47 52.29 9 65.21 53.87 10 69.78 55.89 11 74.15 58.32 12 78.28 61.15 13 82.12 64.35 14 85.65 67.89 15 88.83 71.74 16 89.71 73.04 Circle Center At X = 45.8 ; Y = 104.0 and Radius, 53.8 * ** 2.938 * ** Failure Surface Specified By 17 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 20.89 54.00 2 25.58 52.28 3 30.40 50.95 4 35.32 50.03 5 40.29 49.52 6 45.29 49.44 7 50.28 49.76 8 55.23 50.51 9 60.09 51.66 10 64.84 53.22 11 69.45 55.16 12 73.87 57.49 13 78.09 60.17 14 82.07 63.20 15 85.78 66.55 16 89.20 70.20 17 91.90 73.60 Circle Center At X = 43.9 ; Y = 109.3 and Radius, 59.9 * ** 2.941 * ** Failure Surface Specified By 23 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 20.89 54.00 2 25.63 52.41 3 30.45 51.10 4 35.35 50.07 5 40.29 49.33 6 45.27 48.88 7 50.27 48.73 8 55.27 48.87 9 60.25 49.29 10 65.20 50.01 11 70.10 51.02 12 74.92 52.32 13 79.67 53.89 14 84.32 55.74 15 88.85 57.86 16 93.24 60.24 17 97.49 62.87 18 101.58 65.75 19 105.50 68.86 20 109.22 72.19 21 112.75 75.74 22 116.06 79.49 23 116.43. 79.96 Circle Center At X = 50.4 ; Y = 134.1 and Radius, 85.4 * ** 2.946 * ** Failure Surface Specified By 16 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 15.67 54.00 2 20.20 .51.88 3 24.92 50.24 4 29.79 49.11 5 34.75 48.49 6 39.75 48.39 7 44.73 48.81 8 49.64 49.75 9 54.43 51.19 10 59.04 53.13 11 63.42 55.54 12 67.53 58.39 13 71.32 61.65 14 74.74 65.29 15 77.77 69.27 16 78.26 70.07 Circle Center At X = 38.2 ; Y = 96.2 and Radius, 47.9 * ** 2.946 * ** Failure Surface Specified By 16 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 41.78 59.98 2 46.62 61.24 3 51.46 62.50 4 56.29 63.77 5 61.13 65.05 6 65.96 66.33 7 70.79 67.61 8 75.62 68.90 9 80.45 70.20 10 85.28 71.50 11 90.11 72.80 12 94.93 74.12 13 99.75 75.44 14 104.58 76.76 15 109.40 78.09 16 112.34 78.90 Circle Center At X = * * * * * * ; Y = 4306.0 and Radius, 4386.4 * ** 2.968 * ** Failure Surface Specified By 24 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 20.89 54.00 2 , 25.54 52.17 3 30.30 50.62 4 35.13 49.36 5 40.04 48.38 6 44.99 47.71 7 49.98 47.33 8 54.98 47.25 9 59.97 47.46 10 64.95 47.98 11 69.88 48.79 12 74.76 49.89 13 79.56 51.29 14 84.27 52.97 15 88.87 54.92 16 93.34 57.15. 17 97.68 59.64 18 101.86 62.39 19 105.86 65.38 20 109.69 68.61 21 113.31 72.05 22 . 116.72 75.71 23 119.90 79.57 24 121.07 81.17 Circle Center At X = 53.8 ; Y = 130.9 and Radius, 83.7 * ** 2.969 * ** Failure Surface Specified By 21 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 31.33 54.00 2 36.20 52.84 3 41.12 51.97 4 46.09 51.37 5 51.08 51.06 6 56.08 51.03 7 61.07 51.28 8 66.04 51.82 9 70.97 52.63 10 75.85 53.73 11 80.66 55.10 12 85.38 56:74 13 90.00 58.65 14 94.51 60.82 15 98.89 63.24 16 103.12 65.90 17 107.19 68.80 18 111.10. 71.92 19 114.81 75.26 20 118.34 78.81 21 120.23 80.95 Circle Center At X = 54.1 ; Y = 139.1 and Radius, 88.1 * ** 2.972 * ** Failure Surface Specified By 29 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 20.89 54.00 2 25.63 52.40 3 30.43 51.00 4 35.28 49.81 5 40.19 48.83 6 45.13 48.07 7 50.10 47.51 8 55.08 47.17 9 60.08 47.05 10 65.08 47.14 11 70.07 47.44 12 75.05 47.96 13 79.99 48.70 14 84.90 49.64 15 89.77 50.80 16 94.58 52.16 17 99.32 53.73 18 104.00 55.50 19 108.59 57.48 20 113.10 59.64 21 1 17.51 62.00 22 121.81 64.55 23 126.00 67.28 24 130.07 70.19 25 134.00 73.27 26 137.81 76.52 27 141.47 79.92 28 144.98 83.49 29 145.44 84.00 Circle Center At X = 60.5 ; Y = 163.2 and Radius, 116.2 * ** 2.977 ` * ** SLOPE STABILITY ANALYSIS SECTION D -D ** PCSTABL6 ** by Purdue University modified by Peter J. Bosscher University of Wisconsin- Madison - -Slope Stability Analysis- - Simplified Janbu, Simplified Bishop or Spencer's Method of Slices PROBLEM DESCRIPTION Section D -D BOUNDARY COORDINATES 10 Top Boundaries 21 Total Boundaries Boundary X -Left Y -Left X -Right Y -Right Soil Type No. (ft) (ft) (ft) (ft) Below Bnd 1 0.00 60.00 10.00 62.00 2 2 10.00 62.00 20.00 64.00 2 3 20.00 64.00 30.00 66.00 2 4 30.00 66.00 34.00 66.75 2 5 34.00 66.75 34.50 70.00 1 6 34.50 70.00 70.00 84.00 1 7 70.00 84.00 108.00 84.00 1 8 108.00 84.00 127.00 84.00 2 9 127.00 84.00 140.00 86.00 3 10 140.00 86.00 143.00 87.00 3 11 34.00 66.75 40.00 68.00 2 12 40.00 68.00 49.00 70.00 2 13 49.00 70.00 59.00 72.00 2 14 59.00 72.00 65.00 74.00 2 15 65.00 74.00 75.00 76.00 2 16 75.00 76.00 84.00 78.00 2 • 17 84.00 78.00 92.00 80.00 2 18 92.00 80.00 100.00. 82.00 2 19 100.00 82.00 108.00 84.00 2 20 0.00 60.00 40.00 60.00 3 21 40.00 60.00 127.00 84.00 3 ISOTROPIC SOIL PARAMETERS 3 Type(s) of Soil Soil Total Saturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface No. (pcf) (pcf) (psf) (deg) Param. (psf) No. 1 125.0 130.0 0.0 39.0 0.00 0.0 0 2 125.0 130.0 0.0 38.0 0.00 0.0 0 3 115.0 115.0 250.0 28.0 0.00 0.0 0 A Critical Failure Surface Searching Method, Using A Random Technique For Generating Circular Surfaces, Has Been Specified. 200 Trial Surfaces Have Been Generated. 10 Surfaces Initiate From Each Of 20 Points Equally Spaced • Along The Ground Surface Between X = 0.00 ft. and X = 30.00 ft. Each Surface Terminates Between X = 44.50 ft. and X = 100.00 ft. Unless Further Limitations Were Imposed, The Minimum Elevation At Which A Surface Extends Is Y = 40.00 ft. 5.00 ft. Line Segments Define Each Trial Failure Surface. Following Are Displayed The Ten Most Critical Of The Trial Failure Surfaces Examined. They Are Ordered - Most Critical First. * * Safety Factors Are Calculated By The Modified Bishop Method * * Failure Surface Specified By 5 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 28.42 65.68 2 33.42 65.76 3 38.16 67.37 4 42.17 70.35 5 44.80 74.06 Circle Center At X = 30.7 ; Y = 81.6 and Radius, 16.1 * ** 1.603 * ** Failure Surface Specified By • 5 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 30.00 66.00 2 34.98 66.40 3 39.61 68.31 4 43.42 71.54 5 45.07 74.17 Circle Center At X = 31.2 ; Y = 82.1 and Radius, 16.2 * ** 1.605 * ** Failure Surface Specified By 7 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 25.26 65.05 2 30.25 64.68 3 35.20 65.35 4 39.91 67.03 5 44.17 69.66 6 47.79 73.11 7 49.78 76.03 Circle Center At X = 29.5 ; Y = 88.6 and Radius, 24.0 { * ** 1.817 * ** Failure Surface Specified By 6 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 28.42 65.68 2 33.40. 65.26 3 38.29 66.30 4 42.67 68.72 5 46.16 72.30 6 47.67 75.19 Circle Center At X = 32.3 ; Y = 82.3 and Radius, 17.1 * ** 1.828 * ** Failure Surface Specified By 8 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 22.11 64.42 2 27.10 64.15 3 32.07 64.64 4 36.92 65.89 5 41.51 67.86 6 45.75 70.52 7 49.53 73.79 8 52.26 77.00 Circle Center At X = 26.4 ; Y = 96.7 and Radius, 32.6 * ** 1.858 * ** Failure Surface Specified By 7 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 28.42 65.68 2 33.42 65.58 3 38.35 66.44 4 43.01 68.23 5 47.25 70.89 6 50.90 74.30 7 53.09. 77.33 Circle Center At X = 31.4 ; Y = 91.4 and Radius, 25.9 * ** .1.859 * ** Failure Surface Specified By 7 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 25.26 65.05 2 30.21 64.31 3 35.17 64.93 4 39.79 66.85 5 43.72 69.94 6 46.68 73.96 7 47.05 74.95 Circle Center At X = 30.4 ; Y = 82.8 and Radius, 18.5 * ** 1.860 * ** Failure Surface Specified By 10 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 18.95 63.79 2 23.95 63.67 3 28.93 64.12 4 33.82 65.13 5 38.57 66.70 6 43.11 68.80 7 47.38 71.40 8 51.33 74.46 9 54.90 77.96 10 55.00 78.09 Circle Center At X = 22.5 ; Y = 107.5 and Radius, 43.8 * ** 1.885 * ** Failure Surface Specified By 10 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 22.11 64.42 2 27.10 64.28 3 32.08 64.71 4 36.98 65.73 5 41.72 67.31 6 46.25 69.43 7 50.50 72.07 8 54.42 75.18 9 57.94 78.72 10 58.53 79.48 Circle Center At X = 25.8 ; Y = 107.1 and Radius, 42.8 * ** 1.903 * ** Failure Surface Specified By 6 Coordinate Points Point X -Surf Y -Surf No. (ft) (ft) 1 30.00 66.00 2 34.98 65.57 3 39.83 66.78 4 44.02 69.51 5 47.10 73.45 6 47.71 75.21 Circle Center At X = 33.8 ; Y = 80.7 and Radius, 15.2 * ** 1.907 * ** Plfao i FINDINGS rmions G go.scpve GENERAL. 1. On August 13, 1992, Fosterview Estates applied for a boundary line adjustment, a planned residential development permit, and submitted an environmental checklist. An application for a preliminary plat was submitted on March 15, 1993. 2. Fosterview Estates is a proposed 41 -lot residential development on a 9.7 -acre parcel. The project includes the extension of South 137th Street from the intersection of 44th Avenue S. west across the site to connect with 42nd Ave. S. 3. A Mitigated Determination of Nonsignificance (MDNS) was issued July 22, 1993. Upon appeal, the City Council upheld the SEPA determination on November 1, 1993. 4. On December 6, December 7, and December 20, 1993, and April 25, 1994, the City Council received testimony from the parties listed on Attachment 1. Public notice was given by mail to property owners within 300 feet of the subject property, and by advertisement in the Seattle Times on November 12 and 19, 1993, and March 11, 1994. The public hearings were held to consider information provided as exhibits and testimony given by the applicant, staff and residents. Exhibits entered into the record are listed below and have been renumbered for the sake of clarity: 1. Preliminary Plat /Subdivision a. Site Plan b. Grading and Street Plan c. Landscape Plan d. Utilities Plan e. Tree Survey 2. Planned Residential Development a. Site Plan b. Grading and Street Plan c. Landscape Plan d. Cross Sections e. Eight Architectural Drawings f. Renderings 3. Wetlands Buffer Enhancement Plan Narrative 4. Basic Content of Proposed Conditions, Covenants and Restrictions 5. SEPA Mitigated Determination of Nonsignificance as amended 1 6. Comment Letters Received from Residents 7. Preliminary Plat /Subdivision, Boundary Line Adjustment and PRD Applications 8. Recommended Modifications to Landscape Plan 9. Ordinances: a. SAO b. TPO c. PRD d. Detailed Procedures for Subdivisions 10. Minutes from the City Council dated December 20, 1993. 11. Supplemental Planning Commission Report as Modified on April 18, 1994 12. Planning Commission Minutes dated April 14, 1994 13. Memo from Rick Beeler Dated April 18, 1994 14. Site Plan Showing Perspective Locations 15. Off -site Perspectives with Building Elevations. 16. Revised Landscape Plan. 17. Street Light Standard. 18. Modifications to Landscape Plan Prepared by Staff and Presented at the Public Hearing. 19. Staff report to the Planning Commission dated August 19, 1993 20. Planning Commission Minutes dated Sept. 23, 1993 21. Planning Commission Minutes dated October 14, 1993 22. Memorandum from Jack Pace Dated October 7, 1993 23. Staff report dated November 23, 1993 24. DCD Code Interpretation of November 25, 1991 25. Letter from Amy Kosterlitz dated November 24, 1993 26. Current Copy of TMC 21.04.270 27. Current Copy of RCW 43.21 28. Current Copies of WAC 197.11.350, 197.11.402, 197.11.448 29. Off -Site Drainage Analysis for Fosterview Estates (May 12, 1993) 30. Drainage Basin Maps of Existing and Future Drainage (August 10, 1993) 31. Peer Review of Geotechnology by AGI 32. Copies of the "Wetlands Study" 33. Revised wetlands study 34. Outline of wetlands buffer enhancement plan 35. Tree Survey 36. Copies of "Guidebook for Agencies" and SEPA Handbook 37. Sequence of meeting transcripts and ordinance drafts of adoption of the Sensitive Areas Ordinance 38. Memo from Rick Beeler dated December 1, 1993 5. A Class 2 watercourse and Class 2 wetland have been identified on the site and set 2 • aside in Tracts A and B. 6. TMC, Chapter 18.54, Tree Regulations (TPO) requires a vegetation canopy dominated by trees cover 20% of the site after construction as proposed. 7. The road design includes crossing the watercourse. TMC, Section 18.45.080 (SAO) requires enhancement and restoration for impacted areas and a conceptual plan was provided. A final plan will be approved by staff prior to Final Plat approval. 8. TMC, Section 18.46.112 stipulates eight criteria for PRD review. Testimony was presented that showed the project meets each criterion as follows: a. Compliance with the Subdivision Code, TMC, Chapter 17.20: The project complies with a majority of the Subdivision Code with the exception of lot area and setbacks. Two additional subdivision standards were applied including 15 -foot vegetation buffers for through lots and minimum right of way width for S. 137th St. b. Density bonus: The applicant is not seeking a density bonus. c. Adverse environmental impacts have been mitigated: The MDNS includes fourteen mitigation measures to ensure all identified potential environmental impacts will be adequately mitigated. d. Compliance of the proposal to PRD and Sensitive Area Ordinance: The project proposes the following: 1. identifying, preserving and setting aside sensitive areas and buffers in sensitive area tracts to be held under common ownership; 2. The PRD approach was used; 3. compensation for intrusion into sensitive area buffer through buffer enhancement; 4. peer review of geotechnical studies; 5. construction monitoring; 6. imposing an assurance device to guarantee performance and maintenance of sensitive areas and associated buffers including monitoring and enhancement. e. Time limitations and phasing: The MDNS requires a phasing and sequencing plan to include erosion control measures and limiting construction to the dryer months. 3 f. Compliance with the comprehensive land use policy plan and other relevant plans. The following Comprehensive Land Use Policy Plan policies apply: RESIDENCE/HOUSING Objective 1. Assure a diversified supply of housing in the planning area; Policy 1. Encourage housing developments which provide a diversity of housing types; Objective 2. Maintain a suitable, livable housing supply in the planning area; Objective 4. Policy 1. Encourage housing designs in which building forms and spaces allow residents to adopt proprietary attitudes beyond their normal living spaces. Discourage housing designs which cause anonymity among residents and foster feelings of helpless isolation. Policy 2. Encourage housing designs which provide for the visual surveillance of public spaces both from the dwelling units and the street. Policy 3. Encourage the adequate lighting of residential streets and parking lots. g. Compliance with BAR review guidelines (TMC 18.60.050): The BAR approved the project with conditions (Exhibit 13). h. Appropriate retention and preservation of existing trees and vegetation as recommended by the Director of Community Development: Locations for tree preservation and additional trees are shown in Exhibit 11b. 9. Subdivisions and Short Plats, TMC, Title 17, prescribes thirteen goals for subdivisions. CONCLUSION 1. Proper notice was given in accordance with TMC, 17.12.030. 2. The City Council considered recommendations of the Planning Commission and Board of Architectural Review and concluded the project meets the provisions and intent of the PRD requirements (TMC, Chapter 18.46) and the BAR Design Guidelines (TMC, Section 18.46.050) in the following ways: a. reduction of unnecessary grading to retain trees and topographic features and 4 to minimize large retaining walls; b. avoidance of the dominance of garages along the streetscape where appropriate; c. increase of landscaping in front setbacks; d. provision of a variety of architectural styles; e. insurance that all architectural styles include pitched roofs in keeping with the surrounding neighborhood; and f. emphasis on good pedestrian circulation, access and safety. g. the project meets to objectives and policies of the Comprehensive Land Use Plan as identified in the findings; h. a mixture of deciduous and native coniferous trees on identified lots is necessary to achieve healthy and fast - growing vegetation; i. the off -site perspectives (Exhibit 6) demonstrate that additional landscaping is required to further enhance screening in order to meet the vegetative coverage requirements of TMC, Section 18.46.060(f)(1). 3. The project results in a harmonious streetscape created by uniform building setbacks, massing and height. The similarity of type and placement of landscape materials provides a connection along the streetscape. 5. The landscape plan does not reflect the size required by the Tree Regulations for trees, therefore, the final landscape plan must meet the size requirements. 6. While the PRD provides for deviation to zoning standards, lot widths of perimeter lots for a majority of lots must be increased to achieve compatibility with surrounding development. 7. In response to the adjacent property owner expressing concerns regarding the proposed pedestrian trail to the north and privacy, additional vegetation should be planted on the property to the north to provide screening. 8. The Restrictive Covenants (CC&R's) provide assurance that the sensitive area (SA) tracts and sloped areas will retain the existing vegetation, and be maintained for the enjoyment of the project's residents as well as help mitigate the visual impact of the development to the neighborhood. The CC&R's will address the purpose and maintenance of fencing required along the SA tract boundaries. Based on the above Findings and Conclusions, the following conditions are imposed: 1. That south 137th Street which bisects the property, have 40 -foot right -of -ways, 5 30 -feet of pavement curb to curb, and 5 -foot easements on either side. 2. The width of pavement for 43rd Place shall be 24 feet; The width of right -of- way for 43rd Place shall be 24 feet; A 10 -foot wide utility easement shall run along the south side of 43rd Place South and shall contain a five -foot wide sidewalk. 3. That TMC, Section 17.24.040(g)(4) be implemented : for through lots, a 15- foot rear yard buffer of native vegetation shall be provided. 4. The applicant shall prepare, and the Directors of the Departments of Community Development and Public Works and the City Attorney shall approve, a performance bond for project phasing prior to final plat approval. The purpose of the bond is to protect on and off -site properties from unforseen circumstances related to the development. The performance bond shall last for a two -year period and commence from the completion date of each phase. 5. Hold - harmless language including relationships to future slope instability, shall be prepared by the applicant and reviewed by the City Attorney, the Departments of Public Works and Community Development. Such language shall be included in the Final Plat documents and in each property deed. 6. The Director of Community Development shall recalculate the bonus density calculations based on the street widths of the Final PRD and require that total density be adjusted accordingly. 7. Lot widths for perimeter lots shall be a minimum of 50 feet. Perimeter lots include: Lots 1 through 9; Lots 14 through 19; Lots 25 through 28; Lots 32 through 35 and Lot 41. 8. Lots that are on the perimeter of the development have a required front yard setback of 20 feet if the front yard faces the perimeter; side yard setbacks that are equal to Tukwila R -1 Code; and a back yard setback equal to Tukwila R -1 code if the back yard faces the perimeter of the development. 9. The 20 -foot utility access easement proposed along a portion of the north property line beginning at the east edge of the right -of -way to be vacated and running westerly a distance of approximately 124 feet, shall be labeled as: "20- foot public utility and pedestrian access easement ". 10. The final plat be conditional upon satisfactory BAR review as required in 6 TMC 18.46.060 (g). 10a. That a mixture of Western Red Cedar or some other similar coniferous tree be installed at the rear of lots 22, 23, 24 and at the front of lots 2 and 3 (to replace proposed deciduous trees); and that all additional trees specified in Section I and Section II (Planning Commission Report) be a representative mixture of either native or introduced, fast - growing coniferous trees. 10b. The maximum achievable ground cover be achieved and that the plantings exhibit vigorous growth both at the time of planting and throughout the period of guarantee, which shall become a condition of the final plat approval. 11. That the final plat be conditional upon staff providing Council with a satisfactory evaluation of the off -site perspectives or a modification to the planning requirements as required in Legal Conditions in 18.46.060(f)(1). 11a. Add six (6) trees to meet the coverage requirements per TMC, Section 18.46.060(f)(1). Trees shall be planted at the front of lot 2, and at the rear of lots 9, 14, 16, 17 and 18. The tree types shall be specified by the Department of Community Development. 12. A 5 -foot high, black color - coated chain link fence shall be erected along the north property line from the Southgate park boundary eastward on top of the bulkhead or rockery, and a dense hedge be planted on the property immediately north of the site. 13. Landscaping: Street trees shall vary between conifers and deciduous. Minimum sizes will be 2 -1/2" caliper; or 8 -10 feet high; 14. Additional trees shall be provided as shown on Exhibit 2 of the City Council packet dated April 25, 1994; 15. The Final Wetlands Mitigation/Enhancement Plan is for the roadway crossing and buffer reduction. The Plan must be provided to and approved by DCD prior to issuance of Land Altering Permits. Recommended vegetation must include a diversity of trees compatible with existing vegetation. The Final Wetlands Mitigation Plan shall contain the following at a minimum: a. The amount of clearing and grading proposed for the roadway 7 " :•* crossing at the watercourse and any grading within the associated wetland/buffer areas including cross - sections showing areas of disturbance; b. A report which describes: 1. The purpose of the enhancement /restoration; 2. The areas to be enhanced /restored; 3. How the areas will be enhanced /restored; 4. The selected plantings for roadway crossing and buffer reductions; 5. When the enhancement will occur; 6. A 2 -year maintenance /monitoring program. 16. Should a sign be proposed at some future date, the design shall be reviewed by DCD to ensure it is in keeping with the overall design of the project and that it is sited so as not to obstruct visibility to vehicles. 17. Street lighting shall be redesigned to be more in keeping with the residential character of the area. The final design shall be administratively approved by DCD. 18. The discrepancy between the Landscape Plan and Grading Plan related to areas to be held in open space easements shall be corrected. The correction shall accurately delineate the boundaries of these areas. The revised Landscape Plan and Grading and Street Plans must be consistent and provided prior to issuance of Land Altering Permits. 19. The developer shall erect a permanent three -foot high split -rail wood fence along the boundaries of all open space easement locations prior to any grading. 20. The final Conditions, Covenants, and Restrictions shall be submitted with the Final Plat application and shall include a revised legal description which specifically describes open space easement areas. ; Residents: 1. Ron Lamb 2. Nancy Lamb 3. Elizabeth Springer 4. Pam Carter 5. Fred Sherman 6. Janelle Scarber 7. Marilynn Van Hise 8. Pam Reiss 9. Fred Palmer 10. Janelle Scarber Applicant: 1. Amy Kosterlitz 2. Bill Fowler 3. Jean Bates 4. Erich Tietze 5. Terry Gibson 6. Garrett Munger Staff: ATTACHMENT 1 PARTIES OF RECORD 1. Department of Community Development 2. Public Works Otlrl-IGAT.13 PARK. 1444.-As 94' 3394• giree••■•••• INA•rte._ ktifl 11) 110•4•••• •■••• g••■• M.A. qv...re *mourn,' in.. r•••••••• ■•••Ino Pc••••• 1.47,.••;0•4 Ant 4," TREE LEN' 90C! PL•1471101 4314245 MTN, ..7.7••=•. FIANNA 'WAG OCNIFERIS Noma : • 1104.."1,/ Or.. NOT 011...1101 f fr. d•uKl•••1•41. 94 144 9441444040 tCflI 0.1 /.0,ui..+00 D. 6440 6.7110•11. 144••••r. LANDSCAPING PLAN P.R.D. / PRELIMINARY PLAT / SUBDIVISION FOSTERVIEW ESTATES DUJARDIH U DEVELOPMENT COMPANY === TROD 5IRCIA5 MAY: A • ALAVA e • CAW.. GM Col • COMILWOOD 490. CYPAS5, P. PA w • WILLOW ■.,.• t 1. [Lac CANOPY PAT A •rt-r .••rte Li 41,14. 2, L.., ((W.. .1•006 le• T.O. Oo..49T 90,3 C•••••• to (••••■ e■-•■•..,,•) • •'.,m 449413 0,...414 930.409 01.) • 17 600 raft CO•••••■• 1.•..) • 100 449 A• o.•••••• *A.4. • ( TH LANDSCAPE 'PLAN • I • 30. 4«•••■••"1Af' 00 0004440 ••■•••••• 4 I!13"5 • April 28, 1994 • City of Tukwila John W. Rants, Mayor Department of Community Development Rick Beeler, Director • Mr. Bill Fowler Vice President Dujardin Development Company 9623 32nd Street S.E. Everett, WA 98206 Re: Fosterview Estates Wetland Mitigation/Enhancement Plan. Dear Mr. Fowler: I am writing to clarify the guidelines for preparing a mitigation or enhancement plan. After discussing the situation with the DCD Director, we will require the wetland mitigation plan be completed by a qualified wetland specialist. My primary role is limited to reviewing submitted plans and how they conform to City regulations. Your landscape architect may assist with mitigation drawings but the written report, plant species composition, planting locations, and performance and monitoring aspects should be provided by the wetland specialist. The plan should also include an impact assessment related to the sensitive area buffer reduction (TMC 18.45.040 c.4.A.) and watercourse crossing (TMC 18.45.080 d.2.A. & B.). Please refer to the Fosterview PRD Conditions pertaining to the mitigation plan and the attached standard Wetland & Watercourse Special Studies - Report Criteria. After the plan is submitted, I will review it as quickly as possible and assist you with Fish and Wildlife HPA requirements and Tukwila's Land Altering permit. If you have any questions related to this letter or the requirements of a mitigation /enhancement plan, please contact me at 431 -3662. Sincerely, G y C. Gary S ulz Urban Environmentalist cc: Rick Beeler, DCD Director Denni Shefrin, Associate Planner 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 4313665 . �.�,�.......,.....- _._.._,.._ - City of Tukwila Department of Community Development MEMORANDUM TO: FROM: DATE: SUBJECT: Mayor Rants Rick Beeler, DCD March 31, 1994 Fosterview Estates PRD/Preliminary Subdivision John W. Rants, Mayor Rick Beeler, Director On April 4, 1994, the City Council is to hold a hearing on the Board of Architecture Review (BAR) criteria and the downslope and side yard buffers analysis pursuant to TMC 18.46.060 (PRD chapter). , You may recall that the City Council approved the PRD /preliminary subdivision subject to review of that information. Originally staff felt that the Council could hear and decide on the information without returning the application to the BAR/Planning Commission. Therefore, the April 4 hearing was scheduled. Further examination of TMC 18.46.060 indicates the BAR/Planning Commission should hear the information and forward a recommendation to the City Council before the Council holds its hearing. Accordingly, I am requesting a continuance of the Council's hearing to April 25, 1994. This will enable the BAR/Planning Commission to hold its hearing on April 14, 1994. The applicant is agreeable to the continuance. cc: City. Council 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 41313670. • Fax (206) 431-3665 ► 43'4' �NI.111 -A w'' ,, y, 0 `V %,ifir; ► 2 ', City of Tukwila John W. Rants, Mayor � ®;�� Department of Community Development Rick Beeler, Director 1908 February 16, 1994 Mr. Bill Fowler Dujardin Development Company P.O. Box 5308 Everett, WA 98206 Subject: Fosterview Estates Dear Bill: This letter summarizes the status of the Fosterview Estates PRD /Preliminary Plat. On February 22, 1994, the City Council will adopt the Findings and Conclusions for the SEPA appeal (please see attached). As we have previously discussed, several of the conditions imposed by the City Council at the time the Preliminary Plat/PRD /Boundary Line Adjustment was approved in December, are either in conflict with other City codes and /or regulations, or need clarification in order to implement. As part of staff's evaluation of the conditions, you were asked to prepare and submit a revised plat which reflects the conditions as well as identify questions and concerns you had based upon the conditions. After comparing the revised plat to the approved plat and to other City regulations, staff and the City Attorney have determined that the conditions must be brought back before the City Council to modify for clarity and to resolve conflicts with other codes. The reason to return to Council now rather than later is to provide predictability to you, staff and the City Council and to avoid significant changes to the project at the Final Plat stage. Conditions 10 and 11 both require returning to the BAR or Council prior to final plat approval. Condition #10 requires BAR review and Condition #11 requires off-site perspectives per TMC Section 18.46.060(f) (1). I therefore recommend the following which include changes to the PRD: 1. prepare the elevations and off-site perspectives for downslope and side yard buffers NOW per PRD Section 18.46.060 (f)(1) of the TMC (see attached); 2. staff will prepare a memo to Council which demonstrates how each of the BAR review criteria is met; 3. Lot 13 is not a through lot. Therefore, a 15 -foot landscape buffer is not required and should be deleted; 4. It is not recommended that the full width of the pedestrian trail run through lots 8, 9 and 10. The northern boundary of these lots should terminate at the center of the access easement. This will alter the configuration and increase the lot area for Lot 14. 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431 -3665 • • • ? Page 2 A tentative hearing date has been scheduled for March 21 in order to allow adequate time to prepare the perspective drawings. I would need the 20 sets of perspectives and the revised PRD no later than March 9, 1994. 1 recognize that you or your consultants may have additional questions concerning the interpretation of Section 18.46.060 (f)(1) and clarification of lot line adjustments. Please refer all questions to me directly. For your information, I have attached a draft synopsis of issues and concerns related to the adopted conditions. A memo with a.similar synopsis will be provided to the City Council and will contain specific language to consider for condition revisions. Please notify me at once if you find any errors in the draft synopsis. Lastly, I wanted to confirm that a grading plan is not necessary at this time. Please feel free to contact me at 431 -3663 if you have any questions. I will contact you to confirm that you have received this letter. Thank you. Sincerely, Denni Shefrin Associate Planner Enclosures: 1. SEPA Findings and Conclusions 2. Conditions Synopsis 3. PRD Section 18.46.060(0(1) cc: Jack Pace File FINDINGS: City of Tukwila ........� ..... �... •.. John W. Rants, Mayor Department of Community Development Rick Beeler, Director CITY COUNCIL CITY OF TUKWILA FINDINGS AND CONCLUSIONS SEPA Appeal Fosterview Estates Prepared February 4, 1994 1. On August 13, 1992, Fosterview Estates applied for a boundary line adjustment, a planned residential development permit, and submitted an environmental checklist. An application for a preliminary plat was submitted on March 15, 1993. Fosterview Estates is a single family subdivision of 41 Tots on a 10 -acre parcel zoned R1 -7.2. The checklist was required by the State Environmental Policy Act of 1971 (SEPA) and TMC 21.04. Because the property contains wetlands, a watercourse and steep slopes, development is also regulated by the City's Sensitive Areas Ordinance, TMC 21.45. 2. The City's SEPA Responsible Official determined that based upon several technical studies prepared by and reviewed by experts, the project would not result in a major action which would significantly affect the quality of the environment. On July 22, 1993, a mitigated determination of nonsignificance (MDNS) under RCW 43.21 C.030(2) and WAC 197.11.340(2) was issued. 3. The MDNS identified four potential impacts: (1) Drainage; (2) Traffic (vehicular and pedestrian); (3) Slope stability; and (4) On -site wetlands. The MDNS included 14 mitigation measures to mitigate these specific impacts as identified and explained therein (TMC 21.04.250 (1), (2) and (3). 4. Timely appeals of the Responsible Official's decision were filed by citizens who reside within the vicinity of the project site. The appeal requested that an environmental impact statement (EIS) be prepared. The list of appellants follow: a. Ron and Nancy Lamb b. Pam Carter c. David and Cathryn Sackett d. George Tidwell e. Lynn Sauve f. Elizabeth Springer g. Kathryn and John Stetson h. Tim and Susan Thompson i. Janelle and Bob Scarber 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431-3665 Fosterview Estates Findings & Conclusions Page 2 5. After holding three community meetings, the Responsible Official extended the comment period of the MDNS to August 13, 1993. Several comment letters were received during that period. 6. On August 13, 1993, the Responsible Official issued an amended MDNS with a comment period ending August 23, 1993. No additional appeals were filed. 7. The City Council held a public hearing on the appeal on October 11 and October 18, 1993, wherein twenty five exhibits were entered into the record. Sworn testimony was taken from the appellants, staff, applicants and experts. On November 1, 1993, the Council deliberated on the matter. The proceedings were taped and a transcript prepared pursuant to TMC 21.04.280 (e). The City Council rendered its decision within the time constraints set out in TMC 21.04.280 (c). 8. WAC 197.11 (SEPA) and TMC 21.04 require, in deciding the appeal, that 'substantial weight' be given to the decision of the Responsible Official. 9. The City Council employed a clearly erroneous standard. After hearing all relevant evidence pursuant to TMC 21.04.280 (d), the City Council posed the question of whether the Council was left with the definite and firm conviction that a mistake had been made. 10. The City Council, in deciding whether the Responsible Official erred in the decision to issue a Mitigated Determination of Nonsignificance, considered the following: a. That the Sensitive Areas Overly Zone (SAO) (TMC 18.45) defines sensitive areas as wetlands, watercourses, areas of geologic instability and abandoned coal mine areas; b. The SAO further requires that technical studies be conducted by the applicant and undergo a peer review by a City- appointed technical expert; c. That the Mitigated Determination of Nonsignificance was conditioned, after peer review, upon future studies to complete documentation of slope stability and appropriate handling of underground springs; d. That the use of future studies have been accepted in case law related to SEPA. CONCLUSIONS: 1. After affording substantial weight to the decision of the Responsible Official, the City Council concluded that the Responsible Official did not err in issuing the MDNS instead of requiring preparation of an EIS based upon the following: a. A substantial number of studies, reports and evaluations were prepared; b. That the studies, reports and evaluations were prepared by well - respected highly specialized, outside consultants with no vested interest in this project; c. That the history of this project spans over at least four years; d. That a substantial amount of coordination occurred interdepartmentally and with other agencies to seek additional information, confirmation and conclusions for various studies as demonstrated by correspondence and comments received from staff experts and Fosterview Estates Findings & Conclusions outside consultants. Page 3 e. That the Responsible Official took into account comments solicited at three citizen meetings and written comments before making its decision. 2. The City Council also concludes that the mitigation measures required in the MDNS adequately address the environmental impacts, particularly because future studies will document the slope stability and containment of underground springs. 3. An Environmental Impact Statement will not yield stronger mitigation measures. An error was not made by the Responsible Official in imposing the mitigation measures as identified in the MDNS. 4. The mitigation measures are commensurate with and mitigate the identified, probable, significant, adverse impacts and are reasonable and capable of being accomplished (WAC 197 -11 -660). 5. The MDNS was accurately based on existing policies adopted in the TMC 21.04.250 (1) and (3). 6. Prior to issuing the amended MDNS, the City reviewed a large and comprehensive array of studies, reports, surveys and documents pertaining to virtually all environmental aspects surrounding this development project. A partial list of these studies include: a 17 May 1993 Geotechnical Evaluation prepared by Applied Geotechnology; b. 12 May 1993 Drainage Report prepared by Erich O. Tietze and Associates; c. 9 March 1993 Development Study prepared by Charles Morgan and Associates; d. 23 April 1993 Departments of Community Development and Public Works internal memorandum and comments; e. 15 March 1993 Drainage Analysis prepared by Erich O. Tietze and Associates; f. 22 Feb. 1993 Geotechnical Studies, Terra and Associates 9. 22 Dec. 1993 Updated Geotechnical Report, Terra and Associates h. 5 May 1993 Report on Roadway Design, Dujardin Development Company i. 1 July 1993 Wetlands Report, Terra and Associates j. 3 Dec. 1990 Wetland Evaluation Report, Terra and Associates k. 11 Aug. 1990 Geotechnical Study, Terra and Associates Also submitted was a host of detailed traffic studies by Gibson Traffic Consultants, driveway profiles, building design drawings, several surface•water analysis, a recent report by Hammond, Collier, Wade, Livingstone, as well as other public reports and documents. 7. The City held three public meetings: 30 July 1993, 3 August 1993 and 10 August 1993. These meetings were well- attended. 8. The potential environmental impacts of the Fosterview Estates proposal were carefully, completely and accurately evaluated, discussed, re- evaluated and fine -tuned such that 15 very specific mitigation measures were identified and incorporated into the MDNS. Fosterview Estates Memo to J. Pace 4 Feb 94 Page 16 Below, Council Conditions are listed verbatim In italics. Issues have also been identified based upon the imposed conditions and the revised plat including concerns raised by the applicant. COUNCIL CONDITIONS : CONDITION #1 That south 137th St. which bisects the property have 40 -foot right -of -ways, 30 feet of pavement curb to curb, and 5 foot easements on either side.' ISSUES: The condition results in adding two feet to the width of pavement. The condition would also cause a 5- foot easement to be extending into the watercourse on the south side. No utilities were proposed at this location. Encroachment into the watercourse is approximately 400 square feet. 1. If the objective of SAO is to avoid sensitive areas, why should this encroachment be necessary, particularly when no utilities are proposed on this side of the right -of -way? 2. Why should the applicant need to compensate SAO encroachment for a utility easement where no utilities will be installed? 3. Why would the crossing need to be the same width as the rest of S. 137th St. rather than narrow the crossing in order to preserve the sensitive areas on both sides? If the objective is to provide parking along the street, parking would still be available on either side of the crossing. This approach would meet the primary objective of preserving sensitive areas. 4. Widening S. 137th impacts Tracts A and B. The combined amount of lost sensitive areas within Tracts A and B is approximately 400 square feet. 5. Impervious surface area is increased by 2,362 square feet. The SAO combined with flexibility allowed under the PRD encourage the reduction of impervious surface area where normal standards would reduce the amount of sensitive area. RECOMMENDATION: 1. Do not increase the width of S. 137th St. in order to maximize the amount of sensitive area to be preserved; 2. If Council maintains that the width of S. 137th St. should not be narrowed, then the Council should consider narrowing the crossing only. CONDITION #2 "...condition 43rd Place should be 24 -foot of pavement, 24 -foot right -of -way, 10 -foot utility easement on the south side, a 5-foot utility easement on the north side and a 5 -foot sidewalk on the south side" [more discussion] 'Amendment would be to modify 43rd as described or allow 43rd Place to be deleted in its Fosterview Estates Memo to J. Pace 4 Feb 94 Page 17 entirety with Lots 25, 26, 27, 28, 29 and 30 fronting on 42nd Avenue. And that's the applicant's choice.• '...either widen this street as we described, or the applicant can delete the street in its entirety and have Lots 25, 26, 27, 28, 29 and 30 on 42nd Avenue. So this would become a back yard then lying essentially between 22, 23 and 24 and the ones described.' ISSUES: The applicant has elected to retain 43rd Place and states that new grades affecting Lots 25, 26, 27 and 28, resulting from this condition, will not exceed those recommended by the geotechnical engineer. RECOMMENDATION 1. Council required a 5 -foot utility easement on the north side of 43rd P., however, no utilities are proposed at this location. Therefore, omit this condition. 2. The phrasing of this condition must be improved for clarity. CONDITION #3 'Subdivision code 17.24.040 be enforced in its entirety to include 15 -foot buffers where there are through lots.' ISSUE: 1. If the intent of Council is to apply this section of the Subdivision Code in its entirety, then the proposal would conflict with 17.24.040(g)(2) Lots. Minimum Size - whereby the PRD proposes lot areas Tess than those required by the underlying zone. Council's action approved deviations to this standard. RECOMMENDATIONS: 1. Condition #3: Revise to read as follows: That TMC 17.24.040(g)(4) be implemented' OR For through Tots, a 15 -foot rear yard buffer of native vegetation shall be provided.' * *The code does not define "native vegetation', therefore, staff has interpreted this to mean either retain existing vegetation in these areas, or install vegetation native to this region. CONDITION #4. "The DCD Department of Community Development Director and the Director of Public Works propose -be authorized to set up performance bonds based upon development phasings- phasing of a development to be reviewed and approved by the City Attorney prior to the final plat approval.' ISSUES: 1. The wording of this condition should be cleaned up; Fosterview Estates Memo to J. Pace 4 Feb 94 . Page 18 2. Condition #15 (the last part of Council's discussion) also pertains to a performance bond. The two conditions should be consolidated. RECOMMENDATION: reword: 'The applicant shall prepare and the Directors of the Departments of Community Development and Public Works and the City Attorney shall approve a performance bond for project phasing prior to final plat approval. The purpose of the bond is to protect on and off-site properties from unforseen circumstances related to the development. The performance bond shall last for a five year period and commence from the completion date of each phase.' CONDITION #5 'Hold Harmless Clause -that the Director of Community Development and the Director of Public Works prepare appropriate home hold harmless clauses to be recorded with appropriate lot deeds as reviewed by the City Attorney.' ISSUES: 1. It is unclear why the City should prepare hold harmless clauses. The Council may have intended to say that the applicant will prepare hold - harmless language to be contained in each deed /land title. The wording of this condition should be cleaned up. RECOMMENDATION: reword: 'Hold - harmless language shall be prepared by the applicant and reviewed by the City Attorney, the Departments of Public Works and Community Development. Such language shall be included in each deed /land title.' CONDITION #6 "Recalculate density bonuses due to different street widths...the Director of Community Development recalculate the bonus density calculations based on the street widths of the Final PRD and require that total density be adjusted accordingly." ISSUES: The wording of this condition should be cleaned up. RECOMMENDATION: reword: 'The Department of Community Development shall recalculate the amount of density allowed based upon changes to street widths per Condition #1 and Condition #2.' Fosterview Estates Memo to J. Pace 4 Feb 94 CONDITION #7 ' M C� 7 Dp Page 19 'The Director of Community Development require that the lot widths of perimeter lost be adjusted to be a minimum of 50 feet at the perimeter -per lot at the perimeter.' RECOMMENDATION: reword: 'Lot widths for perimeter tots shall be a minimum of 50 feet. Perimeter lots include: Lots 1 through 9; Lots 14 through 19; Lots 25 through 28; Lots 32 through 35 and Lot 41.' CONDITION #8 'Lots that are on the perimeter of the development have a required front yard setback of 20 feet if the front yard faces the perimeter; side yard setbacks that are equal to Tukwila R -1 Code; and a back yard setback equal to Tukwila R -1 code if the back yard faces the perimeter of the development.' ISSUES: This condition is unnecessary. Setbacks for the current proposal reflect the condition in the following way: a front setbacks on perimeter lots are not less than 20 feet; b. rear setbacks on perimeter lots are not less than 10 feet as required in TMC for R -1 -7.2 zone; c. side yard setbacks on perimeter Tots meet the R -1 -7.2 zone standard based on lot width. CONDITION #9 'Public access easement and trail at northeast corner.' '...The 20 -foot utility easement be identified as public right -of -way for future trail...public access for future trail improvements...easement.' RECOMMENDATION: reword: The 20 -foot utility access easement proposed along a portion of the north property line beginning at the east edge of the right -of -way to be vacated and running westerly a distance of approximately 124 feet, shall be labeled: 20 -foot public utility and pedestrian access easement.' CONDITION #10 The final plat be conditional upon satisfactory BAR review as required in TMC 18.46.060 (g).' ISSUE: BAR review is not required in the TMC. What IS required is that BAR design review guidelines be applied to a PRD. Addressing compliance in the Findings and Conclusions document avoids going before the BAR when their review is not required in the first place. Therefore, the condition should be reworded. RECOMMENDATION: Fosterview Estates Memo to J. Pace 4 Feb 94 D Page 20 reword: The Department of Community Development, in the Findings and Conclusions for this project, shall demonstrate that the project complies with each of the BAR Design Review Criteria.' CONDITION #11 That the final plat be conditional upon staff providing Council with a satisfactory evaluation of the off -site perspectives or a modification to the planning requirements as required in Legal Conditions in 18.46.060(f)(1).` ISSUE: 1. The code does not specify from where off -site perspectives are to be taken and the applicant has asked for direction. 2. This condition should be reworded for clarity RECOMMENDATION: 1. reword: 'The project shall comply with TMC,. Section 18.46.060(0(1), Landscape and Site Treatment for Sites With Class 2, Class 3 and Class 4 Geologic Hazard Areas. Elevations and off -site perspectives must be submitted to the Department of Community Development and approved by the City Council prior to final plat approval. 2. The Planning Commission should determine guidelines such as from the property boundary, or X- number of feet from the property boundary. CONDITION #12 `The final plat be conditional upon a 5 -foot high, black color - coated chain link fence be erected along the north property line from the Southgate park boundary east on top of the bulkhead or rockery, and a dense hedge be planted on the property immediately north of the site.` ISSUES: This condition should be reworded. RECOMMENDATION: reword: 'A 5 -foot high, black color- coated chain Zink fence shall be erected along the north property line from the Southgate park boundary eastward on top of the bulkhead or rockery, and a dense hedge be planted on the property immediately north of the site." CONDITION #13 "That the items on page 2 and 3 of the memo from Rick Beeler, Director of the Department of Community Development, dated December 1, 1993...7 had a modification...items 5,6,8,9,10,11 and 12 as defined..conditional upon those items." : Fosterview Estates Memo to J. Pace 4 Feb 94 ISSUES: D r Page 21 Council's discussion omitted Condition #7 per Rick's memo, in Condition #13, but added it in Condition #14. Therefore, conditions 13 and 14 should be combined (see below). Also, it is better to list all conditions as part of Council's action. The conditions as shown below have been renumbered to reflect the number sequence established by Council. RECOMMENDATION: reword: 'That the condition No's 5, 6, 7, 8, 9, 10, 11 and 12 as described in the Memo from Rick Beeler dated December 1, 1993, be added as follows, and that Condition #15 ( #7) be modified as shown in underline: Condition No. 13: Landscaping: Street trees shall vary between conifers and deciduous. Minimum sizes will be 2 -1/2' caliper; or 8 -10 feet high; Condition No. 14: Additional trees shall be provided as shown on Attachment H of this packet; Condition No. 15: The Final Wetlands Mitigation /Enhancement Plan is for the roadway crossing and buffer reduction. The Plan must be provided to and approved by DCD prior to issuance of Land Altering Permits. Recommended vegetation must include a diversity of trees compatible with existing vegetating. The Final Wetlands Mitigation Plan shall contain the following at a minimum: a. The amount of clearing and grading proposed for the roadway crossing at the watercourse and any grading within the associated wetland /bufferareas including cross - sections showing areas of disturbance; b. A report which describes: 1. The purpose of the enhancement/restoration; 2. The areas to be enhanced /restored; 3. How the areas will be enhanced /restored; 4. The selected plantings for roadway crossing and buffer reductions; 5. When the enhancement will occur; 6. A 2 -year maintenance /monitoring program. CONDITION #14 'The final plat be conditional upon item 7 on Page 2 of the memo from Rick Beeler to the Mayor and City Council, December 1, 1993, as written, the change at the end of the first paragraph, the word - between the word 'following' and the colon, the three words `at a minimum' be inserted.' . +... >.. Fosterview Estates Memo to J. Pace 4 Feb 94 RECOMMENDATION: Included in Condition #15 above. Omit this condition. CONDITION #15 0 Page 22 'That a performance bond to last a duration of 5 years from completion of all phases of the project to protect on -site and off -site property owners from unforseen circumstances related to this development.' ISSUES: Condition No. 4 also relates to a performance bond. Therefore, the conditions should be combined as modified (see Condition #4). The question was raised at the hearing re: legal duration of a performance bond. The RCW's were compared with Section 18.45.135 of the TMC. The TMC stipulates up to five years. The RCW's stipulate up to two years 'after final approval' according to Mike Waiters. Q: Affirm that the most restrictive regulation supersedes. GENERAL COMMENTS 1. The revised preliminary plat generally reflects the following: a. Increase in width for S. 137th & 43rd Pl. resulted in: 1. reduced lot areas for lots 38, 39, 40 and 41; 2. Tract A as been reduced by 397 square feet 3. Increase of impervious surface area 4. Wetland Mitigation Enhancement Plan must be modified to reflect additional encroachment. b. Lot configurations generally improved: lots 9,10 & 11 follow the curvature of S. 137th creating a more interesting streetscape; c. Spacing between building footprints is minimally increased d. There is no conflict between SEPA mitigation conditions and Council conditions ( ? ? ?) Check wetland mitigation language , • • TITLE 18 — ZONING dwelling units per net acre permitted in the underlying zone shall serve as the criteria to determine basic PRD density. (2) Building Height. Building heights may be modified within a PRD when it assists in maintaining natural resources and significant vegetation, and en- hances views within the site without interfering with the views of adjoining property. For increases in build- ing height, there shall be a commensurate decrease in impervious surface. (3) Setbacks. Yard requirements as described in Chapter 18.50 shall be waived within the PRD; however, setbacks and design of the perimeter of the PRD shall be comparable to or compatible with the bulk and streetscape . of the existing development of adjacent properties or the type of development which may be permitted. (b) Off -street Parking. Off -street parking shall be provided in a PRD in the same ratio for types of build- ings and uses as required in Chapter 18.56. However, for multiple - family zoned sites with sensitive areas, a minimum of two parking stalls per unit will be allowed, with a fifty percent compact stalls allowance, and parking stalls in front of carports or garages will be allowed if the design does not affect circulation. (c) Platting Requirements: The standards of the subdivision code for residential subdivisions shall apply to planned residential developments if such standards are not in conflict with the provisions of this chapter. Upon final approval of the PRD, filing of the PRD shall be in accordance with procedures of the subdivision code if any lots are to be transferred. (d) Impervious Surface. The maximum amount of impervious surface calculated for the total develop- ment allowed on sensitive areas sites will be fifty per- cent for each single - family development and each multifamily development. (e) Recreation Space Requirements. Sensitive areas and stands of significant trees may be counted. as area required to meet the recreation space minimums, if usable passive recreation opportunities within these areas are demonstrated. Opportunities could include connection and continuation of area -wide trail systems, wildlife or scenic viewing opportunities, or picnic areas. (f) Landscape and Site Treatment for Sites with Class 2, Class 3 and Class 4 Geologic Hazard Areas. (1) Downslope and Side Yard Buffers. Eleva- tions and off -site perspectives shall show minimum landscape coverage of twenty -five percent of the structures at time of project completion with anticipated forty percent coverage within fifteen years. This. stan- dard may supplement or be in lieu of the applicable landscape yard requirement. (2) Roads and Access Drives. Any road or access drive which cuts approximately perpendicular to a slope to the ridge line of a hill shall have minimum five -foot planted medians. The tree shall be a species that provides a branch pattern sufficient to provide, at maturity, fifty percent coverage of the pavement area. Roads or drives which require retaining walls parallel to the topographic line shall plant roadside buffers of Northwest native plant species. (g) The Board of Architectural Review shall review guidelines for single- family and multifamily developments. The design and review of the PRD shall also utilize the guidelines of Section 18.60.050. (h) For single - family developments, site plans shall include placement and footprint of the residences, driveways and roads. (Ord 1599 §4(5), 1991; Ord 1289 §4, 1983; Ord 1247 §1(part), 1982) 18.46.070 Density standards. (a) Basic Density. The basic density shall be the same as permitted by the underlying zone district. The dwelling units per net acre for the residential zones are as provided in Chapter 18.50. (b) Single- family. (1) In R -1 single- family residential districts, the Planning Commission may recommend, and the City Council may authorize, a minimum lot size not less than the yard requirements of the R-1-7.2 district, following findings that the amenities or design features listed in subsections (b) (2)(A) through (b)(2) (D) of this section are substantially provided. (2) In R -1 single - family residential districts on sites containing sensitive areas or their buffers, the Planning Commission may recommend, and the City Council may authorize, a minimum lot size less than the yard requirements of the R -1 -7.2 district, following findings that the amenities or design features listed below are substantially provided: (A) At least fifteen percent of the natural vegetation is retained (in cases where significant stands exist). (B) Advantage is taken or enhancement is achieved of unusual or significant site features such as views, watercourses, or other natural characteristics. (C) Separation of auto and pedestrian movement is provided especially in or near areas of recreation. (D) Development aspects of the PRD complement the land use policies of the Comprehen- sive Plan. (c) In multiple- family residential districts, the Planning Commission may recommend, and the City Council may authorize, a dwelling -unit density not more than twenty percent greater than permitted by the underlying zones or an increase equal to the allowable density credits as set forth in subsection (d) of this section, if the site contains sensitive areas. or buffers following findings that the amenities or design features listed below are substantially provided: (1) A variety of housing types is offered. Printed August 4, 1993 Pane 18-53 J City of Tukwila John W. Rants, Mayor Department of Community Development Rick Beeler, Director January 11, 1994 Mr. Bill Fowler Dujardin Development Company P.O. Box 5308 Everett, WA 98206 Subject: Fosterview Estates Dear Bill: The purpose of this letter is to summarize our recent phone conversations. You were faxed a portion of the verbatim transcript from the December 20, 1993 City Council meeting which includes the discussion related specifically to conditions imposed on the project. I indicated that a revised preliminary plat should be prepared to incorporate those conditions which render design changes. The purpose of the revised plat will enable you as the applicant, and the City, to identify impacts design changes may have based upon the approved conditions. Potential impacts may apply to the site and grading plans and with existing regulations and policies of the City. From this exercise, staff will determine the best route to follow to reintroduce these issues to the City Council. It is therefore essential that these issues be accurately identified and resolved quickly. The revised plat should be provided to me no later than January 21st. Please provide four copies for staff distribution. A cover letter should accompany the revised plat which identifies issues and conflicts in a list format which results from the design changes. The letter should also identify those conditions where clarification is needed. You should also be aware of the expiration limits which pertain to both the PRD and Preliminary Plat: Section 18.46.140 of the Tukwila Municipal reads as follows: 'Construction of improvements in the PRD shall begin within twelve months from the date of the filing of the final PRD plan by the City Clerk as provided in Section 18.46.130. An extension of time for beginning construction may be requested in writing by the applicant, and such extension not exceeding six months may be granted by the Planning Commission upon showing of good cause. If construction does not occur within eighteen months from the date of filing of PRD plans by the City Clerk, the PRD zoning suffix shall be dropped from the official zoning map and the zoning shall revert to the underlying designation.' Approval of the Preliminary Plat becomes null and void one year from the date the preliminary plat is approved. The City Council may grant one extension but not to exceed one year. A full set of transcripts from the December 20, 1993 City Council meeting is enclosed for your information. 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431-3665 Fosterview Estates Letter to B. Fowler 1/11/94 If you have any questions, please contact me at 431 -3663. Sincerely, Denni Shefrin Associate Planner cc: Jack Pace . Encl. Page 2 BUCK & GORDON 902 WATERFRONT PLACE • 1011 WESTERN AVENUE SEATTLE, WASHINGTON 98104-1097 (206) 382-9540 • FACSIMILE (206) 626-0675 ATTORNEYS AT LAW PETER L. BUCK BRENT CARSON JAY P. DERR JOEL M. GORDON SHELLEY E. KNEIP AMY L. KOSTERLITZ KEITH E. MOXON Mayor John W. Rants Members of the City Council 6200 Southcenter Boulevard Tukwila, WA 98188 November 24, 1993 Re: Fosterview Estates -- PRD /Subdivision Hearing Dear Mayor Rants and Members of the City Council: OF COUNSEL ALISON D. BIRMINGHAM MADELEINE A.F. BRENNER PROJECT MANAGER KATHRYN A. GARDOVI; P.E. This is the memorandum of the applicant, Dujardin Development (the "Applicant "), in support of the Fosterview Estates Planned Residential Development ( "PRD ") and subdivision, as approved by the Department of Community Development (the "Department "). This memorandum addresses two key issues, one raised by the Planning Commission's recommendation regarding minimum lot size, and the second raised by the DNS Appellants regarding the application of the density transfer provisions. I. INTRODUCTION A. First Issue is the Legality of Planning Commission's Recommendation to Impose A Minimum Lot Size of 5,000 Square Feet and of the Legality of the Commission's Use of this Rationale to Cut Two Lots From the Project The first issue is whether or not the City Council (the "Council ") should approve the 41 lot PRD as recommended by the Department, or whether the Council should accept the Planning Commission's recommendation that a 5,000 square foot minimum lot size be imposed, which resulted in the loss of two lots (leaving 39 lots). Applicant requests that the Council approve the proposed 41 lot PRD /subdivision as recommended by the Department and that it reject the Planning Commission's recommended imposition of a minimum lot size of 5,000 square feet. As set forth in further detail in the legal argument section below, such a minimum lot size is nowhere authorized in Tukwila's ordinances, and thus, is arbitrary and capricious and beyond the City's authority to impose. RFCENED EEC( 1 41993 COMMUNITY nrvri (PMFNT Mayor John W. Rants and Members of the City Council - 2 - November 24, 1993 B. The Second Issue Is Whether the Department and Planning Commission Correctly Applied the Density Transfer Provisions of the PRD Ordinance The second issue is the correctness of the Department's and the Planning Commission's interpretation of the density transfer provisions of the PRD ordinance. The appellants in the DNS hearing suggested that the PRD density transfer provisions precluded the transfer of density to buildable steep slope sensitive areas. However, the language of the entire density transfer section supports the correctness of the Department's interpretation of the density transfer provisions, which interpretation was implicitly accepted by the Planning Commission. (Note: the Planning Commission's reduction of two lots did not reflect a disagreement with the Department's interpretation of the density transfer section but rather a desire to impose a minimum lot size requirement.) The rationale for why the Department correctly interpreted the density transfer section is set forth in detail in the legal argument section below. II. FACTUAL BACKGROUND The description of the Fosterview proposal and the reasons that it meets the PRD and subdivision ordinance criteria for approval are set forth in detail in the Department's August 26, 1993 Report to the Planning Commission, attached hereto as Appendix A. The rationale for approval will be further substantiated by evidence at the hearing. Thus, the proposal's compliance with the PRD and subdivision review criteria will not be repeated here. Rather, this memorandum will concentrate on the two legal issues set forth above. III. LEGAL ARGUMENT A. The Planning Commission Erred in Arbitrarily Imposing a Minimum Lot Size of 5.000 Square Feet. Which Lot Size Limitation Is Nowhere Authorized in Tukwila's Codes. and in Basing a Reduction of the Project Density On This Minimum Lot Size Requirement The PRD ordinance, Tukwila Municipal Code (TMC) Ch. 18.46, like the PRD or PUD provisions of many jurisdictions, allows flexibility to deviate from the usual zoning requirements for lot size, yards, etc., in order to "encourage imaginative site and building design and to create open space." TMC 18.46.010. The PRD is available so long as one has a minimum site size of one acre (TMC 18.46.040), the PRD abuts at least one major, secondary or collector arterial (TMC 18.46.050), and the review criteria of TMC 18.46.112 are met. This proposal has more than an acre, abuts an arterial and, as set forth in the Planning Department report of 8/26/93, it meets all of the relevant review criteria. See Appendix A, pp. 7 -11. Once the PRD is available, the PRD ordinance makes it clear that the lot size provisions of the zoning code, in this case, those of the R-1-7.2 zone are waived, and the density is controlled by the allowable number of units per net acre. TMC 18.46.060. The allowable number of units per acre for sites with undevelopable sensitive areas is controlled by Mayor John W. Rants and Members of the City Council - 3 - November 24, 1993 a density transfer formula (TMC 18.46.070 (d)), which will be discussed in more detail in the second legal argument section below. In this case, the application of the density formula by the Department as approved by the Planning Commission resulted in an allowable density of 41 units. It has been the position of the Department since the earliest meetings with the Applicant that there would be no minimum lot size requirement. A letter from the Department to the applicant's architect, Charles Morgan & Assoc., dated December 27, 1991, attached hereto as Appendix B, stated: In order to preserve and protect sensitive areas, clustering of dwellings and/or lots less than 7,200 square feet in area is encouraged. It is not necessary for a PRD to meet minimum lot sizes or building setbacks as stipulated by zoning regulations. See Appendix B, p. 3. (emphasis added). The Department's position that there is no minimum lot size has been borne out by their approval of Fosterview project with a variety of lot sizes, with no specified minimum. The Council should give deference to the Department's interpretation of the ordinance, as the body with expertise in administering the City's ordinances. In fact, the PRD ordinance is very clear that the Council may authorize a minimum lot size less than the 7,200 square feet normally required in the R -1 -7.2 district. TMC 18.46.070(a). Moreover, that section in subsection (1) provides that in single family districts without sensitive areas "the City Council may authorize a minimum lot size not less than the yard requirements of the R -1 -7.2 District if certain design features are provided, and subsection (2) reads that on sites containing sensitive areas, like the Fosterview site, "the City Council may authorize a minimum lot size less than the yard requirements of the R -1 -7.2 district," if those design features are substantially provided. Computing the area covered by the minimum yard requirements in the R -1 -7.2 district would result in an area of 3,040 square feet. See attached Appendix C. Thus, the code allows the Council to reduce lot size on sites without sensitive areas to not less than the yard requirements, or to a size not less than 3,040 square feet, and allows the Council to reduce lot size on sites with sensitive areas to less than yard requirements or less than 3,040 square feet, provided that the requisite design features are met. Here, the Fosterview project does provide the requisite design features for a lot size reduction, although arguably it is not required to as it does not seek to have lots less than the yard requirements. It is notable that the code only requires that the following amenities or design features be substantially provided: (A) At least fifteen percent of the natural vegetation is retained (in cases where significant stands exist) (B) Advantage is taken or enhancement achieved of unusual or significant site features such as view, watercourses or other natural characteristics Mayor John W. Rants and Members of the City Council - 4 - November 24, 1993 (C) Separation of auto and pedestrian movement is provided especially in or near areas of recreation (D) Development aspects of the PRD compliment the land use policies of the Comprehensive Plan The Fosterview proposal provides these design features as follows. The proposal has (A) significantly more than the requisite fifteen percent of the natural vegetation retained, and in fact retains 45% of the natural tree cover; (B) great advantage is taken of significant site features such as the wetlands, water course and views in the siting of the houses; (C) pedestrian and auto traffic is separated by sidewalks and in some cases there are paths, e.g. to the park; (D) development aspects compliment the land use policies of the Comprehensive Plan which urge both preservation of significant natural features as well as the promotion of housing opportunities in the City. What is notable here is that Fosterview, as a site with sensitive areas, is entitled under the Tukwila code to be considered for lot sizes less than 3,040 square feet. However, Fosterview is not asking the Council to go that far. The project's smallest lot, at 3,949, is in excess of the yard requirements. Thus, the Council should uphold the Department's judgment that the Fosterview lots meet the requirements of the ordinance, and should approve the PRD /subdivision. The only rationale for the Planning Commission's requirements that the lot lines be adjusted to result in 5,000 square foot lots is that they felt that this was "close to the direction expressed in the Vision Tukwila minutes." However, the Vision Tukwila minutes are not adopted regulations, but rather are just the beginning of the GMA process, whose outcome may vary greatly from the initial discussions. Hence, the Vision Tukwila minutes cannot be the basis for imposition of such a minimum lot size or for cutting down the density allowable under the City's adopted PRD ordinance. This is particularly true where the adopted PRD ordinance allows the Council to go below 3,040 square feet on sites with sensitive areas. Thus, the Planning Commission's imposition of a 5,000 square foot limit on lot size, and their corresponding requirements for combination of certain lots and enlargement of another to meet this 5,000 square foot limit, is arbitrary and in excess of their authority under the City's ordinance. If the City now desires a minimum lot size requirement for PRD's and wants to now impose such a requirement through amendment of its PRD ordinance, it may amend its ordinance. However, the City cannot, consistent with the legal doctrine of vested rights, retroactively impose a new minimum lot size requirement on the Fosterview project. This project acquired a vested right to be judged by the ordinances in effect at the time it submitted its subdivision application. Adams v. Thurston County. et al., 70 Wn. App. 471, 855 P.2d 284 (1993). Thus, the vested rights doctrine protects Applicant's investment - backed expectations to have its proposal judged by the ordinances in effect when it vested, and precludes the City from retroactively applying a different set of standards. Applicant has Mayor John W. Rants and Members of the City Council - 5 - November 24, 1993 relied upon the ordinance specifying no minimum lot size and, in fact, envisioning lot sizes as small as the yard requirements in its design of the project and has endured considerable expense and effort to meet the code requirements over more than a two year period. For this reason, the vested rights doctrine prohibits the City from imposing an after - the -fact minimum lot size on a vested project such as Fosterview Estates. 2. The Department Properly Interpreted the Density Transfer Formula The Appellants of the DNS raised an issue that the density transfer provisions were improperly interpreted. Appellants claim that the Department misinterpreted TMC 18.46.070 (5), which states that development of the transferred density shall be confined to buildable areas of the site and shall not intrude on sensitive areas or their buffers. Appellants contend that because steep slopes are technically within the ordinance definition of sensitive areas, this means that density cannot be transferred to steep slopes. However, as the Department has ably pointed out in its recent memo to the Council, the Appellants have misread § 18.46.070 (5) by taking it out of context. When § 18.46.070 (5) is read in the context of the definition of density transfer, and the rest of the density transfer section, it is clear that this section means that development of transferred density shall be confined to buildable areas of the site, as opposed to those undevelopable sensitive areas and their buffers, including wetlands, watercourses and their buffers that the density transfer provision was designed to protect. As the Department points out in its Update, § 18.06.203 defines Density Transfer as: Density transfer is a percentage number which represents a credit for housing units which are not allowed to be built in wetlands, watercourses or their buffers. The density transfer is used in a formula for determining the number of residential units allowed on the buildable portion of a lot containing wetlands, watercourses and their buffers. (emphasis added) It is critical to note that while Areas of Potential Geologic Instability (steep slopes over 15 %) are considered sensitive areas, the above definition makes it clear that the density transfer is to compensate for the fact that building cannot occur in certain wetlands, watercourses or their buffers which are included in the density transfer formula, not buildable steep slope areas which are not included in the formula. Also, the Department correctly notes that the transferred density can be used in the "buildable areas of the site." These "buildable areas of the site" include steep slopes which are determined to be developable based upon geotechnical study, subject to specified conditions. The Department's interpretation is also borne out in Sections (1) and (2) of § 18.46.070, the section on Density Transfer, which state: (1) Density transfers are intended to provide for the protection of wetlands, watercourses and associated buffers while allowing development consistent with the existing zoning to the greatest extent. Mayor John W. Rants and Members of the City Council - 6 - November 24, 1993 (2) Density transfers are the percentage credits o be used in calculating the number of dwelling units for a residential site containing ndevelopable sensitive areas or buffers. These two sections reinforce the Department's interpretation that density transfer was to compensate for disallowing development in " undevelopable" sensitive areas such as wetlands, watercourses and their buffers, not "developable" sensi we areas such as steep slopes approved for development with geotechnical conditions. These • evelopable steep slope areas are considered by the density transfer provisions as " buildable areas" which are appropriate sites for density transfer. This interpretation comports with a formal cod interpretation that was issued by the Department in 1991, interpreting the application of the density transfer provisions. See Appendix D, attached. This interpretation, developed with the Fosterview project in mind, interprets undevelopable sensitive areas to be only the wetlands, watercourse and their buffers, and concludes that the allowable number of units is 4 It is also important to recognize that, contrary o Appellants' implication, the "density transfer" formula is not giving the Applicant a density bonus. In fact, the term "density transfer" is somewhat of a misnomer because it results in a reduction of the allowable density under the traditional zoning approach. For example, i this case the application of the traditional zoning, which would include the sensitive . eas in the site area, would yield a total of approximately 50 units, which could be built s• long as they did not physically intrude on the undevelopable sensitive areas. The Ci y, in its adoption of the SAO, introduced a concept of density transfer into the PRD ordinance to come up with what it felt to be a more appropriate reduced density, given that t e site area is actually reduced by the presence of undevelopable sensitive areas. The Depar ment has recognized this in its 8/26/93 Staff Report, p. 8, explaining the concept of density t ansfer by stating that the normal density calculation "must be reduced in order for a sit to reasonably sustain the development, reasonably preserve SA's and be consist.nt with the objectives contained in the applicable ordinances." Thus, the application of the "density transfer" provisions actually reduces the allowable number of units on this nearly ten acre site from approximately 50 units to 41 units, but compensates for this reduction •y allowing the density to be clustered in buildable areas of the site. For all the reasons set forth above, the Applicant respectfully requests that the Council approve the Fosterview Estates subdivision as initially recommended by the Department in its 8/26/93 staff report. DyjardintL11203.alk Ver m Att truly 4yours, (9 osterlitz r e for Dujardin Development City of Tukwila John W. Rants, Mayor Department of Community Development Rick Beeler, Director September 24, 1993 Mr. Bill Fowler Dujardin Development Company 9623 32nd Street SE Everett, WA 98205 Subject: Fosterview Estates - Planning Commission Dear Bill: As you are aware, on September 23, 1993, the Planning Commission moved to recommend that the City Council approve the proposed subdivision /PRD /Boundary Line Adjustment with the following conditions which are in addition to those specified in the staff report dated August 19, 1993: 1. That the lot line between lots 12 and 13 be shifted so that lot 13 is a minimum of 5,000 square feet in area; 2. That Tots 25, 26, 27 and 28 be changed from four to three lots to increase the lot area for three lots); 3. That lots' 38, 39, 40 and 41 be changed from four to three lots. The total number of lots would 39 as opposed to 41 as originally proposed; 4. That a 5 -foot high, black color- coated chain -link fence be placed along the north property line including atop the proposed rockery. The fence shall extend to the east property line of Southgate Park. A dense evergreen hedge shall also be planted on the property directly north of the subject site as agreed to by the property owners of this parcel. The City Council public hearing for the SEPA appeal has been scheduled for October 11, 1993. Once a determination is made on the SEPA appeal, a hearing will be scheduled before the City Council for the subdivision /PRD /boundary-line adjustment. A resolution to set a future hearing for the street vacation will also occur. Amy had also requested copies of tapes for the September 23rd hearing. Because the tapes are recored on a 4 -track system, the City does not have a recording system, however, we have used the City of Seatac in the past for tape duplications at a cost of $15 per tape. A total of $30.00 for the two tapes must be recieved prior to recording. Please make the check payable to the City of Seatac and submit to me directly. 6300 Southcenter Boulevard, Suite 11100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431 -3665 Fosterview Estates If you have any questions, please feel free to contact me at 431 -3663. Sincerely, Denni Shefrin Associate Planner cc: Amy Kosterlitz Files: L92 -0064 L92 -0065 L93 -0014 Page 2 �., . •' >” BUCK & GORDON 902 WATERFRONT PLACE • 1011 WESTERN AVENUE SEATTLE, WASHINGTON 98104 -1097 (206) 382-9540 • FACSIMILE (206) 626-0675 ATTORNEYS AT LAW PETER L. BUCK BRENT CARSON JAY P. DERR JOEL M. GORDON SHELLEY E. KNEIP AMY L. KOSTERLITZ KEITH E. MOXON August 24, 1993 Ms. Denni Shefrin Associate Planner City of Tukwila Department of Community Development 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 Re: Fosterview Estates: Easements for Access to 42nd Dear Denni: OF COUNSEL ALISON D. BIRMINGHAM MADELEINE A.F. BRENNER PROJECT MANAGER KATHRYN A. GARDOW, P.E. As we discussed on the phone today, there is one item that needs follow up by the City regarding the Fosterview subdivision. This letter is simply a reminder that the City needs to grant to Dujardin access easements for the driveways serving lots 32 -35, which driveways will extend from 42nd Avenue South across the narrow strip of City owned property, to serve these lots. Please let me know if you need any assistance in regard to these easements. Otherwise, Dujardin will assume that the City will be preparing and recording these easements as part of the final plat. We appreciate your attention to this matter. Very truly yours, 6 Amy terlitz cc: Bill Fowler Jean Bates DUJARD /NIL08233.ALK AU3 z 5 9s •DEiiLLOl- PENT 0 -J 1908 APPENDIX A City of Tukwila John W. Rants, Mayor =r1 l Department of Community Development • Rick Beeler, Director HEARING DATE: FILE NUMBERS: STAFF REPORT TO THE PLANNING COMMISSION ' Prepared August 19, 1993 August 26, 1993 . STAFF CONTACT: Denni Shefrin 431 -3663 L92 -0064 - Boundary Line Adjustment L92 -0065 - Planned Residential Development (PRD) - L93 -0014 - Subdivision - Preliminary Plat APPLICANT: Dujardin Development Company .REQUEST: LOCATION: To subdivide a 9.7 acre parcel into 41 residential Tots to include two sensitive area tracts and a pedestrian trail to connect with Southgate Park. • Immediately south of Southgate Park between 42nd Ave. S. and 43rd /44th Ave. South. COMPREHENSIVE PLAN DESIGNATION: Single- Family Residential ZONING DISTRICT: R1 -7.2 SEPA DETERMINATION: Mitigated Determination of Nonsignificance (Amended) - L92 -0066 RECOMMENDATIONS: Approval with Conditions ATTACHMENTS: A. • Preliminary Plat /Subdivision 1. Site Plan 2. Grading and Street Plan . 3. Landscape Plan • 4. Utilities Plan 5. Tree Survey • B. Planned Residential Development 1. Site Plan 2. Grading and Street Plan 3. Landscape Plan • 4. Cross Sections 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 4313670 • Fax (206) 431-3665 Planning Commission Report August 26, 1993 Fosterview Estates FINDINGS VICINITY AND SITE INFORMATION Project Description: Page 3 Fosterview Estates is a proposed 41 -lot residential development on a 9.7 -acre parcel. The project includes the extension of South 137th Street from the intersection of 44th Avenue S. west across the site to connect with 42nd Ave. S. Forty -third Avenue South abuts a portion of the site to the east and has been barricaded and closed to vehicular use due to evidence of land movement. The lot layout is described below: A total of 21 single - family lots (Lots 1 through 21) and a cul- de-sac (South 137th Place) are planned for the north side of South 137th Street. Another 14 single - family residential lots (Lots 22 through 35) and a small north - south residential street (43rd Place South) are planned for the west portion of the site on the south side of South 137th Street. A watercourse and wetland have been identified on the site. The PRD requires delineation of these areas is required as discussed below. Six lots (Lots 36-41) would be situated immediately south of South 137 Street on the east side of the site. These lots are bounded on the west and south by a designated wetland area (Tract A). The watercourse area (Tract B) lies to the north of 137th Ave. S. opposite Lots 36-41. The average lot size would be approximately 6,400 square feet in area (see Site Plan - Attachment 1 a, 2a). As indicated above, the site contains environmentally sensitive areas (SA's). City regulations require that SA's be set aside in sensitive area tracts, (Tracts A and B), which will be discussed later in this report. The project also triggers SEPA review and several City- adopted regulations to ensure the project is designed in a manner sensitive to the natural conditions of the site. A street vacation, land dedication, and a boundary line adjustment are also part of this proposal. The 1,954 sq.ft. area proposed to be vacated lies immediately north of the cul- de-sac bulb. The total area proposed for dedication is 12,943 sq.ft. and includes a triangular- shaped parcel located on the northeast edge of the site, and a 20ft. x 291ft. strip on the west side of 44th Ave. S. for road Right -of -Way. The existing property line at the southeast comer would be adjusted 7.5 feet to remedy the building encroachment (garage) from the adjacent lot to the south. Site Description: The site's topography is variable including moderate to steeply sloping areas. The north and northeast portions of the site excluding proposed Tract B are sloped moderately to steeply downward ranging between 15% to 65% in grade. The west portion of the site slopes gently to moderately north and northeasterly with grades of approximately 15% to 25 %. The site also contains environmentally sensitive areas as defined by the City's Sensitive Areas Ordinance (SAO) discussed further in this report. These areas include a wetland and a watercourse. Planning Commission Report August 26, 1993 Fosterview Estates Page 5 The SAO requires that sensitive areas be identified and delineated. A rating system based upon the type, size and value of wetlands, watercourses and steep slopes was developed. Based upon the rating and to preserve or strictly limit development on or near the SA's, a corresponding buffer requirement was created (see SAO attached). In accordance with the SAO delineation methods, the wetland has been rated Class 2 requiring a 50 -foot wide buffer. The watercourse has been rated Class 2 requiring a 35 -foot wide buffer. The SAO and PRD also requires increased setbacks and areas to be set aside in separate tracts which further protects SA'S. While disturbance to sensitive areas is discouraged, the SAO allows for essential roads and utilities provided SA's are either restored or enhanced. Normally, this is accomplished with new plantings which is diverse and compatible with the existing vegetation. The site also contains Class 3 slopes defined by the SAO 'as having 'high landslide potential and include areas sloping between fifteen and forty percent or more, and areas which are underlain by relatively impermeable soils or by bedrock'. As mentioned above, the project proposes some encroachment into the SA buffers for the road crossing (S. 137th St. /S. 137th Pl. intersection) and at the edges of specific lots (lots 21, 37, 39, 40). The road encroachment would occur at the intersection. These encroachments would be within the buffer areas only. For the roadway, the impact would be minimized due to the 90- degree -angle design. Utilities including drainage improvements, would be installed within the road right -of -way. The lot encroachment occurs in order to reduce the amount of excavation and need for high retaining walls. As indicated, two sensitive areas tracts (Tracts A and B) are proposed. The combined tract'size is 5,138 sq. ft. less than the total amount of sensitive area (109,385 square feet). Enhancement and restoration is therefore required. A conceptual wetlands buffer enhancement plan has been conceptually approved by the City's Urban Environmentalist. A final wetlands buffer enhancement plan will be prepared and approved prior to Final Plat approval. Because the internal street system proposes to cross the watercourse, a Hydraulics Permit (issued by the Department of Fisheries) is also required with this project. Interim Tree Preservation Ordinance (TPO): The TPO was adopted to promote building and site planning practices that are responsive to the community's natural environment, without preventing reasonable development of land. The TPO regulates the clearing of trees and understory vegetation. The TPO requires that a vegetation canopy dominated by trees covers 20- percent of the site at minimum after construction for sites whose existing canopy cover is 20- percent. Preservation priority is given to stands of trees which in turn, must be protected during construction. The project complies with TPO requirements. Planned Residential Development (PRD): The SAO stipulates that new subdivisions comply with the PRD provisions of the zoning code. This requirement is intended to provide for the greatest level of design flexibility in order to preserve SA's. In other words, blanket application of the R1 -7.2 zoning regulations for minimum lot sizes and setbacks may not afford sensitive site design and may conflict with SAO buffer requirements, or preclude development entirely. The PRD process pulls all of the ordinances together. It provides design flexibility while allowing relief to Planning Commission Report August 26, 1993 Fosterview Estates Page 7 discussed in this report because the City Council, not the Planning Commission must act on the appeal. PROCESS: Briefly, the public hearing and permitting process occurs in the following order. 1. Planning Commission Hearing a. Subdivision /Preliminary Plat b. PRD c. Boundary Line Adjustment 2. City Council Hearing a SEPA Appeal b. Subdivision /Preliminary Plat c. PRD d. Boundary Line Adjustment e. Street Vacation 3. Land Altering Permits for infrastructure (administrative): a. streets, curb, gutter, sidewalk b. utilities: sewer, water, street lights, and additional appurtenances. Installation of these items must be completed prior to Final Plat approval. 4. Planning Commission a Final Plat 5. City Council a Final Plat PRD REVIEW CRITERIA: 1. 'Requirements of the subdivision code for the proposed development have been met if appropriate'. Basic provisions of the Subdivision Code have been met, however, certain exceptions as allowed under • the PRD have been incorporated to preserve and protect sensitive areas and are described below. The melding of the SAO with PRD provisions allows for deviations under the R1 -7.2 zone provisions. While the zoning code restricts the land use to single - family residential, the PRD makes it possible for single - family development to accommodate the number of units allowed while preserving SA's at the same time (see discussion on density transfer below). The design strategies employed by the project include unit clustering (to avoid sensitive areas). This is achieved by smaller lots and reduced setbacks. While many of the Tots exceed 7,200 square feet in area, most lots are smaller. The overall average lot size is 6,400 square feet. Normally, homes must be setback 30 -feet from the front property line. A majority of the proposed front - yard setbacks are 22 feet to keep the homes further from sensitive area buffers while maintaining a reasonable lot size. Planning Commission Report August 26, 1993 Fosterview Estates Page 9 Acknowledgements: 1. That the sensitive areas and associate buffers should accommodate existing wildlife; 2. • Improvements on 42nd Ave. S. will be completed by the City beyond the property frontage; 3. That the site distance for motorists on 42nd Ave. s. and proposed S. 137th St. meets engineering safety standards. The PRD requires SA's to be delineated and set aside in sensitive area tracts. The project also delineates four separate areas as 'SLOPES TO BE LEFT UNGRADED'. The four areas include: (1) north and east of Tots 16 -20; (2) north of Tots 14 & 15; (3) north of lots 1 -10; (4) east of lots 33-35. In order to retain existing vegetation, maintain reasonable lot sizes, restrict development and reduce the potential for erosion, areas 1-4 shall be set aside in open space easements. All easements will be recorded with the Final Plat. The PRD requires the applicant provide the basic content of proposed Conditions, Covenants and Restrictions (CC&R's, Attachment D). The CC&R's define tract areas, describe how the SA tracts and open space easements would be used and maintained and include language that the open space easements and SA tracts run with the land. 4. 'Compliance of the proposal to PRD and sensitive area requirements'. See the PRD and SAO discussions above. While•the SAO does not restrict development on steep slopes (defined by 15% or greater), or require buffers, the proponent has agreed to set aside sloped areas which would remain undeveloped as discussed above (see Attachment A2,B2). Developed slopes were subjected to the required geotechnical documentation of suitability for development. 5. 'Time limitations, if any, for the entire development and specified. stages have been documented in the application'. One of the mitigation measures required as part of the SEPA review is submittal of a phasing and sequencing plan to include erosion control measures both during and after construction. This plan will be provided prior to the issuance of Land Altering Permits. Construction would be limited to the dryer months. 6. 'Development in accordance with the comprehensive land use policy plan and other relevant plans•. The project satisfies applicable objectives and policies contained RESIDENCE and HOUSING section of the Comprehensive Land Use Policy Plan as described below: RESIDENCE /HOUSING Objective 1. Policy 1. Objective 2. Assure a diversified supply of housing in the planning area; Encourage housing developments which provide a diversity of housing types; Maintain a suitable, livable housing supply in the planning area In addition to the existing comprehensive plan, the State's Growth Management Act requires cities to accommodate additional housing into the next century. The project would provide 41 additional homes Planning Commission Report August 26, 1993 Fosterview Estates Page 11 sq.ft. of new tree canopy (at 10 -year growth and excluding proposed trees within the public right -of -way). Forty -five percent of the existing tree canopy will remain after development (87,485/191,008). The subdivision code also requires one tree per residence located within the front setback. The PRD requires landscaping along sloped side property tines. The project proposes both. Landscaping in addition to a single tree would be installed in the front yards of all Tots. Also, to maintain uniformity for the 42nd Ave. streetscape, Maple trees would be planted along the entire street frontage. Sweet Gum and Western Hemlock trees are also proposed at the rear of Tots 22 -24 (see Attachment A3,B3). Additional trees will be required along streets to further enhance the aesthetics of the overall streetscape (see Attachment G). SUBDIVISION Access /Roads. As discussed above, access is limited onto 42nd Ave. S. A single driveway would serve three residences (Lots 1-3) on the northwest corner, and two shared driveways would serve four residences at the southwest comer (Lots 3235). The City Engineer has also required the installation of a guardrail north of the 42nd Ave. S. /S. 137th St. intersection to give better definition to the road curvature to protect the homes below. The utilities plan reflects shared locations for utilities and streets. A hammerhead tum will be provided between Lots 2 and 3 for fire access. As stated earlier, essential roads and utilities can encroach into sensitive area buffers. The buffer on the south edge of Tract B will be reduced to accommodate the roadway. While the proposed right -of -way width is 40- feet., the actual width of pavement will be 28 -feet plus 5 feet of sidewalk. This width would accommodate parking on the south side only to prevent intrusion into the Tract B buffer. A retaining wall will separate the road from the sensitive area buffer. Additionally, 43rd PI. S. would be 20 -feet wide. The purpose of this is to reduce the amount of impervious surface area and to in effect, cause traffic to move slowly which is desirable in a residential neighborhood. Lot Pattern. The average lot size is 6,400 square feet. The smallest lot (Lot 28) is 3,949 square feet and the largest (Lot 14) is 11,530 square feet. The PRD provides for reductions to lot areas to allow the greatest amount of design flexibility to protect sensitive areas. Pedestrian Access. • To link the residential development to Southgate Park, a pedestrian walkway is proposed at the north edge of the cul -de -sac bulb which extends northwest to connect with the park. Sidewalks are also proposed throughout the subdivision and along 44th Ave. S. Pedestrians could also gain access northeast of the site (opposite the proposed vacated right -of -way). The developer has also agreed to provide funds to the City for the construction of a walkway along S. 137th St. to Macadam Rd. The sidewalk is to be constructed along the 44th Ave. S. frontage. In order to avoid impacting existing, mature trees, the sidewalk has been designed to meander rather than extend in a straight line. Planning Commission Report August 26, 1993 Fosterview Estates Page 13 Because of the residential nature of the project, staff recommends the street Tight to be redesigned to reflect the residential character of the project. • Based upon the above, staff believes the Fosterview Estates project complies with the following ordinances, policies and regulations: 1. Subdivision 2.PRD 3. SAO 4. TPO 5. Comprehensive Land Use Policy Plan 6. GMA RECOMMENDATIONS: • Staff recommends the Planning Commission approve the PRD, Preliminary Plat and Boundary Line Adjustment with the following conditions: CONDITIONS: 1. Landscaping: Street trees shall vary between conifers and deciduous. Minimum sizes shall be 2 -1/2' cal.; or 8 -10 ft. high. 2. Additional trees shall be provided as shown on Attachment G. . 3. The Final Wetlands Mitigation /Enhancement Plan is for the roadway crossing and buffer reduction. The Plan must be provided to and approved by DCD prior to issuance of Land Altering Permits. Recommended vegetation must include a diversity of trees compatible with existing vegetation. The Final Wetlands Mitigation Plan shall contain the following: a . The amount of clearing and grading proposed for the roadway crossing at the watercourse and any grading within the associated wetland /buffer areas including cross - sections showing areas of disturbance; b. Report which describes: • 1. the purpose of the enhancement/restoration 2. areas to be enhanced /restored 3. how areas would be enhanced /restored; 4. selected plantings for roadway crossing and buffer reductions; 5. when enhancement would occur; 6. 2 -year maintenance /monitoring program. 4. Should a sign be proposed at some future date, the design shall be reviewed by DCD to ensure it is in keeping with the overall design of the project and that it is sited so as not to obstruct visibility to vehicles. 5. Street lighting shall be redesigned to be more in keeping with the residential character of the APPENDIX 13 l cn : Vino ru Qwad k , \ vlh un fie. 'Bac,y.�v.. CAWNSe---2 _ , EPIC- 51- 91:FOSTER VIEW ESTATES GtN�u'eCkS December 27, 1991 Page 3 1. Double- tiered lots should be incorporated per the Subdivision Code. Side lots should be at right angles. 2. Lots. should be located adjacent to 42nd Ave South rather than a frontage street. 3. A Planned Residential Development (PRD) provides for extensive flexibility and creative site planning. In order to preserve and protect sensitive areas, clustering of dwellings and /or lots less than 7,200 square feet in area is encouraged. It is not necessary for a PRD to meet minimum lot sizes or building setbacks as stipulated by zoning regulations. The unique environmental features of the site should be incorporated as natural amenities for the residents to enjoy. The site plan .should achieve a. strong balance between the site's natural features and the built environment. The lot layout should optimize enjoyment of the watercourse and wetland by way of preserving these areas under an easement with access points. Through- access should also be provided to the park directly north of the site. Significant trees should be preserved. Locations of significant trees should be identified on revised plans. 4. As part of the PRD submittal, details for each housing type must be provided including building elevations, colors and exterior materials. The designs should strive for architectural variety and harmony. It is critical that garages not dominate the streetscape. Ideally, garages should be accessed by means of an alley. Where an alley .is not possible, garages should be setback beyond the front portion of the home. ' ..•.....,,,......, •.,• YARD SIZE REQUIREMENTS 50` MIN. WOO{ ` fK0u13ti8AGX efL {0 :OF LDT .zwwTH •5` AVA{L ng DIALCIN& Att4 4160SF 10' 10EAK Oaf Mat • M{N.YALDARM •3aiOSF APPENDIX C f"nnE TNTRRPRETED: ?nnina Cnrie CODE INTERPRETATION FORM APPEDIDIX D SECTION NO. PRD Density standards 18.46.070(D) Data Intorprotation Nadel, 27 1.uguot 1001 Interpretation: 1. Housing density = Dwelling Units (DU) /Acre = units per acre after subtraction of street easement or right -of -way; and 2. buildable area - pareel area - sensitive area and buffer. why was this interpretation developed? Cnnfnsi.nn as to how to calculate number of units allowed in a' PPM in sensitive areas. What is • the juatifieastien asf the i.at,ss:ga.•atati al 1. 18 .-46 : 06U Relationship of this chapter to' other sections says that the number of dwelling units per ngti (emphasis added) acre permitted in the underlying zone, shall serve as the criteria to determine PRD density. 18.06.440 Lot area, "means the total horizontal area within the boundary lines of a lot and exclusive of street right -of -way or street easement." Therefore road area is subtracted for the purpose of determining net density. 2. Absent an adopted definition of buildable acres a literal i nterpratati nn is taken of "hn i 1 dahl e arrP , " For eN,aml4Q; A 14 acre parcel r 15% assumption for road area (actual right -of -way would be used on projects), and 2.6 acres in sensjjy areas and buffers results in the following: nui.laab1e aai�a - 10 -- 2:G - 7.4 ac:A. Net DU /acre =63,560 - (43560(.15)) / 7200 = 5.14 (DU /Acre)(buildable_acres) + (DU /Acre)(SA + Buffers.)(% transfer) (5.14) (7.4) + (5.14) (2:6) (.24) = 41 (without sensitive areas the formula would yield 51 units) Signature of Interpreter: Date: Approved By: Date: /125/4f w ••r, • «w.« +00.00. . 4e...«w,y, .) SOUTHGATE PARK 0 vnll rr••n•4114 as W.:c'5o } / • r, 1.1111. 114.0' I 1y 1•w[ KMI NUNN 0';. i r rtll, 1 0.011 *1,1 ... .. 53M n 5!:0 170 • P4u 11 1 y.w.. ,:.- i•�i':Y.WMw... •. �..,. .,r.�r.r. .- .14.4 ......,...rM1 ••••••••••. .w 1 .•t . . 1 -n •• «•w• t « - i • N N m} r1r1- •.• r.« ,.. r • ... 1•. 1 M 12 11 711 7•71 •�., .:...... ..... 0000..„ M • «.•..•.r 1••.•...�.,•K •.I �..... }... 1 `} 7.1..111 +4 4\ 6 ' 5.010 nl 7 tl 7 8 4 9 1 , I , \III P' 1,911 ,0.0'010* x0.0 4401'77•l rC -- 1 I ■ e• \ \�« 4 I7.p -.47 70 80 I I.0 . " \ Y4C4I[D 70.00 5x9'70'0•E -.\ 1 1 54 /\ 97.04 M I' 77'3r0 1 111 ' �.: 1)7.9x, 1101.7\'E' •�. I I lift: 111'I1' 605110 I ♦ / `4\ • + \ i 1,, 10 / 6.757 .911. 70. 11 5,010 9911 5.5111 441 12 7,711 1111 18 4,707 9911 70 i M tI*Yllf0 10 / 5.001 117 4,110 1111. a Irl 1 V 1 • .tl4t��u rt¢ 101 I.•u' 1 ..3: _ 4. F...*. o1 .1111 L•J -� }�1 ( -1 SITE PLAN /.II . VICINITY MAP ..9.6. - SITE 0.461 W.1 19 11,401 .111 2074 .111 \ TRACT "B" 0002.5 101 WA, 133,0.44 7,111 (9 06 001/75) 111 1 0 Or g:c 470.10 sq 11.. 0 fir 00015 - ENg1701110 AKA IU III. ;II O'0A,ru :o r11'• 01 I44v1'lll /• 17,013 7.111. nre. AI:uIS C::tntU 04410 44 7,045 HMO -4- k -r • to‘. :47 Init (7 35 Ken's) . 75%1 VI }.1175} 101 IS 101 079: 3,340 .0 11 A:I 04/41 101 SI: t. : 0,457 1311 171 DIA11 101 5!,'I • .2,11/0 1111 PRELIMINARY PLAT - SUBDIVISION L93 -00t4 FOS'I'ERVIE11r ESTATES DUJARD91 Q! DEVELOPMENT COMPANY CIIARI.ES MORCAN k ASSOCIATES ,!. RCI(IIECIS t I1 • 5,'1§'^•111. ZJ / 8.1301 111 ' 0 1I }31.111•• I C NoN t. - 33 6,109 1911. 77331 117.18'710,1 WATER COURSE ♦39 117 tIW J]'7!'• •. S. 137th ST._ _ Jam% • 7,144 1111 - } . (3 } 36 /5,1111 9911 ,^ ■ /J / 1,A 11 ,111 ..,;1,1"“ . • 11 It 45... � 37 1 38 1.39q 1 140 c .u,_ i ••• '° rr1, J,.. � � 1 1 TRACT "A" NAN N. 50 1101.71 3rf -. 11.137 117 M.. \• 7000 40'1.7737} WETLANDS • 5. 137ih_5T• 9,738 *411. 10 1 /1 IR 0E0K44C0 in 1, cm a 770:.1. 1 • I1 ;I z 1i I II > In � 14' 110113 .117 11.7x•• �1LR7 I�la7'L►.1CY`. � --•tom, wunv M4 *9 1/5 SOUTHGATE PARK 1.• I W.. goo. Amt. I.WwW rb. to14.7. —.7•79,-7•7" elro•WO •••■■ • •••...1.. PARK BOUNDARY 1.• • ..•••• •nh ••••••• • •••• ...ft.... 0, ••••• 11. •••••• ••••••1*---- .\\,,,••••••••••■• LOPES TO BE LEFT ED7TYP. •-• •••••• • •• .•••"' 1•••• • toi t ItNA4 %MAT 11;:riro .5•F 18 • wo ' -' ' 7, ' • ,... ,...„,, ''' I. " 1. -•:•..- 1' i. . r•••••■ •••• ..- • , ••• ... .1, 1P . - 'I J : • „.....,..... I Eon rpa ••• ! •,. 1, • • ‘• II WY.. • 4,1 •••••• piUL (•C GRADING 8 STREET PLAN p p POSTF:RVIElt ESTATES DUARLIiil 21 01■110PuCti1 COW*ANY • •• • •-••• Z:: *11.41910. 111I11 ANI1 AStOCIAll SAW- •r• ••••• • •••■••■ •108 • H••• In •••• ••••-■•• Woe ...IN ral, ••••-•••- fltlfgaLni.T2L."'. ywo •••••••• • • — •••■• ow woo ;or s woo, oat rm.** 4 2/5 • : 0 4".•••.,-, rt.. orrfl r." ft I,- 1 L.\1 1T 1- C7 54,1 7:: 1 : -I, 7 • . . • • • - - ;;-;•-1 • 4 ..,• • : ': -4•r.... • ..1;...."7.' • • '' ...: '''''' 'z.-..';:.-7.•::'::.:7.,,-4'.7...:...;:: ..........,........... " '•7". •j..,1 1;14'. 6 77: 11 1_ — ill i! irr$..tprerrAlry•$1$tr.q.,,.....,_ !VW* 1,(10.* call, Cilt 1.10.11s: • fre•It I •rs .4,1 11 °.r., .4 •• • •••,...• •••• r• •■••1,•1•35 U.•••[1017., nr•••••41, ••••■•• ot 14•40 ••■•11.•. 11.0,1.• LANDSCAPING PLAN P.R.oLtrattlutncyDALLsptiotvisier. FOSTERVIEN ESTATES 01.1.1440111 it 0(1/((.0r14.111 COUP IIT • —_ ._ TREE !....1"----*C:-EN ,. •■•••••••..1 rag,. 1.1•■••••••■• n••••l• cs,... 4,- ••••• •••••• ,.........,/ 1/4„..±..9..•••••• 4 T•fr elrEC415 .4•4: • • ALOCM C. • cer.t. Co • ....von, G+4 • fArn....:10 [.■• • C'*flSS I. • ruk h. • r • IN • 10.1.1..V. •IP 0.Arf.• ..fteE CANIOPY PTA : •••• ."••••• ••••••-•••.....■••••••4 • 1.44.... • At. 1,1L•ltr....P.._kt/ytt_IINMA.4.••••■••■•)_......._______,..111,•441 It ,,•:•.••nr.4 'Pre r.4•r_41-!..... r..4.1!_v....y.•••_fir•41.1....!4Arr........ 1••••••■•sr!....r.L1,..Ar _ rr ..••• ••• r • 0. 140.6 14 I.e. ••■•••••• 1../4 111 (-At:IC:CAPE, PLAN So' A ; I 3 1 • 4. 1. 4" • • 13/5 ' . I•,. rt..1 I114•vr ;:r;Ull034•rr PARK 1�AI +k u( I J(3'ltr i • • N • .ODES TO HE LEFT ,RAGED -rYP. �.� ffii#2- If -4a wail EkSICIV UTILITIES 11,1.1 11 *101 ,.• ,,•• • . PLAN rnuwwAnr ryq sunof slots FOSTFI,RS'IKW ESTATES MART M 11 N%rLorM[n1 cour*uy r �li'll O. Ill 1/1 AM) As.lIrIAIIA, fwc. 1• • V: 7r ;1� to S. 137th Sr • 1 •� �'N. • .c! r .4 , NW. M•I�i1,1n.n 0 CM lmi•*vI'el Ol op tvY I.. • 4/5• SOUTHGATE PAW • "FOSTERVIEW ESTATES" TUKWILA, WASH. DUJAROIN DEVELOPMENT CO. 11.-n;;;:t1; II \ ' < Mot • ,:i • LEGEND .v...�...� w`M... • R •111 < �I, te N y U 4 0 Z 0 4 - z tl M r o ( 0. y O H O c 4 4 V F 2 7 • .T ...cmnmr.n rwr ..n r.w rwr aI� ,wanr.w, row nr.ro IMO. *M.nfMM 1111 Mw. %0Cnrn 0 ...r rawnr..nl r.. 10. Im1 ar n. rwr.OrY.. TREE SURVEY PRELIMINARY PLAT / SUBDIVISION FOSTERVIEW ESTATES DUJARDIII :: DEVELOPMENT COMPANY L{lI INQfX A -4.444 t+• c/Ntep Or•cwwtJJ O.,• MMIMA n.• r.•.. F . o•,f • N • A4 7M.f�• • -,! MO. lOtLY L ' L.lvltl LAY. UM04N Le LOCOS M -Milt • • /fw• N./.NLLow AP. AI/L • CHARLES MORGAN & ASSOCIATES ARCHITECTS rs, ' uaanrm +rnw.�.Y,r jl f3f:il:' q ti tin 5/5 SOUll iGAT E PARK at. I. 401%1 tir 10 1.00 • 714 01 Y01'707.1:I 2 / 1 r 0.40. / 0 0100 00....v1 If 0.% WM, MIMI - • •- , II, I I I 'MIN 5.0/0 .4111 .41,040 ., • _ ..„..... . 6.0,0 1. n .. -r- c 6 7 :I 8 : -1--. 9 1 110,12 11012113r! -* E371063 Ks! 20030 511).2(256•1 rem% Ame 011,6 1101.21-37.6-1 - 1.256 sill. Of 076 11{.01•01-obt 4030 16%0,140 111,15- 1101.27% 11.310 541 7.104 • 34?? 5,5,2 ,s• 7,00' 37160 5 510 sill ...40101%.%1 • "\ _LA • VICINITY MAP .A.s. w - IV 41 04,441 40.0 - 0,0,01 - 011 :SU "V • 04 .140 • 0040 .0,60 .04 .0.4 . *30.0 0.1 • 1041401 - C4071 73 740 .e1 • S.:34.$ (01 • 1? .S•4-P 1. 100. .5 4.4,40 - (4•1) SITE PLAN 030541, CARS..6110•15 mod ••• mu • 044....• Om Hp en ...11160,•./..7.■41) 000 1174.41 ••• Oa.= 414. • 0.4,4 0 et ••41,1 • • 444 •••• ■••/44 ••■• • •••• •■• ••• • • ...Is.... ••••-• ••• •■•■•• •••••• Non • •• ••31 ••••••• ••••• ..••••It ••■• n• • Y... Yaw.. 4•41 • 44s • OP • It.... ••••04 • OL.201 • 11.8.01,040 • • 14 SITE 11.1/1 ti 1.571 11 --"" • """ 27 4,70 1 ./.1 • W., • TRACT "B" 3,34%, • WATER COURSE 6411 37. 141. CS3S5 (01 Ws 611 to Isl. (603 444,0; • Ul 047 410 4:0.7131 .01 • 946 • NIS - 1.40001.4 441.1 10 IV 4400(10 W 1.4.0 . 17.1111 3.11 .116 00.16 "'ANL; 7,10 44 (077, 106,1', 34, . 104 1.1 sq. 1/ 11 . in sl to? 6 ka, 601 - 1,611 44,1 443141 101 971 0144 4.0 10000 VII 101 410 410 PLANNED RESIDENTIAL DEVELOPMENT FO ST E RV I EW ESTATES L92-0065 DUJARDIN :: DEVELOPMENT COMPANY ChARLES )101IDAN & ASSOCIATES • Km rct s 713 1,70.4 017 40)1 • 110.1 :11 1401.130 TRACT "g /* 4,1 04ft \-700o 43 .7-76Tine./d* IKII.7111T 4•07 *374 *0 01 07141'10 (0 ,UaNIA •S. 1 3.7th ST. 6,,36 6411 10 111 00{0710 IC Cal 40 10•440 1 ....i a 2 39 . 400 . •••• L ...„.••-.1• 1 1.: 1 It La 0 i I 0 l., , : I§ I ...7 1-: 4 61 1.07* '.0.2:41 : I 2 WETLAN,O.S. 1 . ,,,.. r-n-d-331=larzr.vz•-- - . " can 6 7. 67 0... \ -- In11rIZr .1 I 00111101 . 1 / 5 ,-- , 0. 03 ... �\ it va laftewi = ati 40* SOUTHGATE PARK «1 .01.1....x, , +w ' 'xtx, x,.,....,. flog =+ •`�,'matir: y ,. iii' -PAfK nou,nnnY :t LOP S TO BE LEFT GR ED —TYP. j�\ 1 \\/ GRADING & STREET PLAN 1 1, .N - 0 • ._••• / PNCIIUiN.51. P■i.(. SI100'VISIO„ POSTER IEW ESTATKS OuJ.QM,t U 6[VtLOPUP,I COuP.in elf ono' b. Tulip ANOASS(MINIS.INC. tt p or.,t in C3 ~MI u•.rinx I C7 pon. un intuit C] Lail . p tune___.__ • 1,001$T • Aglm t: ,+..1,04.0 1,111 • tux - -• ed�a`u ni:in etlui �r'� Of Mt Mg n glee•'•• —.•.,. moon 61 mi. x 2/5 ••••••,...r•tc•arri rAra ••-•) 11..41 1 T- 1- E..:-... a ti (... r' ...(:).:-:t,....: 7.........T... .........::: ..... ......_.i,..._::.......1......,: .. .......... ...,........, ;:,-....,-.•.7-=-7.-.-...: .. : - . • • .. ;..:1 -- - .•••.-••••.;:..- i ! ' 0 -.;,..„: -,,..,;-"--",..„...:,...t. ,.. ,....,..........,..........,„;.,. 1 r -,ii.:••.........,...-..,. 1.................— .• -,•-•-, - . . . -4:. 1 ...e..i.....,.:.i.-4......... .. r 4... - " " • .ii. - i -4. . -I ...,--. :... 4-........... i,..........;\ .i.• ; ',L.:a:m.4:4 47.:1:: - I ......, ... . - ••• r I • • ' 1 . - . . . - . - ' \ \ ',:/ ,.'...:..•••-4'..-::••:;.7..--t";. ,r.; ,..;--r.:.7.7.1.; - a 7.7',.•.......;;,..: ..4:;:i..;.■%=:..4.".'.::.-:.*• N :a .2..?f, !,'''e, "' "...."‘ .....b:::".....; ":•.'"'!...±"_••••••••. ,••••'.I.:•_ : . _ . . - . - -.I ii.:-......,;.....1 . , •.-: -I ....i•i - . . - ‘. . 11.•••-•.•• . •ir-itt •••! • .;•-+!•• i -•••• ._ .1 •2••••>•••••• .. _ _ •••.• : ' • : -. . .... ....... h.. 4 -1:4,,,.7.......-71....7.1...... I ..... ' - • . i...... 4...• ••••.::....... •-;••• .... ! .=:::•:.-• ...; ..A.! „i-..".. '..' = •;....i::•••- ..::.. •.; 1•Itt!..; : . .....1 --........— .. ,......... ' • t • -• • -- • • • =-"x -Ai 4—C=7 Tr -E •• ---- 7 t-t/ •iVe • trkir. ,r7.444.(4 COM t E/7.- • .14 • 41. I ,•of ••■• ,4 1 14 1 41-.11 •Ig 0. •..a.. rue,. LANDSCAPING PLAN PRCLIMiNARY ILAl ismivtsioti FOSTERVIEW ESTATES DUJARDNI St DtVtLOPILNt COMPANY ••••.. == . ....” 1,..• 11•••• •I• 11••■•••• 11.1•18...■ 0...\ .4, ••••• •••••• Lit•ne, k.Z.;,,,IVIIII e•••••• 4 5r•a•l• 111e •41.Y.381. .t.: 4 • /4-0Crt. e. • CatSol.. CO • C.v.. 0 ••■ • Cnt(11.4.4.400 GT•• C•011•,, Fo 110. •■ • /....1..a. r • m.o. •• • WO.A.ONI ../../.1,•1.11 ' (tam C0.N134.1 .••• •111,160 fe 1..eur..111,/t_fv•e.s. i1.11141.1.e211:1v1_--_____.._!1.444 Pe. Yri••4_!P.1.• 91,* .•••••!!.•4..,t • ttLIJI-K. Y.94 mt91. 9.9f •.9Y Pt _ K Vett At•trf_.(••••••:'?. I ••••• 14 42m •••• .12...1•.1 • LaripcAPE PLAN • 1..50' .1,1: ie4a MIL!. • .21E • a 1;i I. 4 -I I Ili 4 A tt. ,1 :13/ 5 • II i (...; L. \;. • Ja ti WSJ • /II' Y 110 140 me erm • arrei.M1 130 tel• CROSS SECTIONS INV *t.../ 44A0' PLANNED RESIDENTIAL DEVELOPMENT FOSTERVIEW ESTATES DuJARDIN LT DEVELOPMENT COMPANY ..11.•• V•••••■ ERICII 0. TIME AND ASSOCIAILS, MI. Om.. 1•••• •■•• ••••■• MOM. .1 ad MOM 1. '4/5 JUL u 100 00 140 130 • 109 110 1.10 CROSS SECTIONS t!) "AA .04 110 /0[0 640 OM Li 0,4 110 HO ; ; 1 1 NINThal LVOV.% II .0011, II , I 7-4.1 0 tOd rf i M14 1M4 ; oettlow e.a ,.• foe.r AIM .01 I11 Id 140 tlfM,P,;°, 04, 44I • PLANNED RESIDENTIAL DEVELOPMENT FOSTERVIEW ESTATES DUJARDIN TT DEVELOPMENT COMPANY 7.11= (Di 01 ERICII 0.1 AND ASSOCIATIS, INC. LA• Mr.11.11.•■•••,••11. 5/5 FOSTERVIEW ESTATES` HOUSE 'A" LOTS 36 -41 LEFT SIDE ELEVATION ENTRY ELEVATION RIGHT SIDE ELEVATION REAR ELEVATION TYPICAL ELEVATION — OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE 2nd FLOOR PLAN 1,924 sq.ft. (APPROXIMATE) • 2cMCM*( 1 st FLOOR PLAN . BASEMENT PLAN FOS.ERVIEW EST.\TES HOUSE 'B' LOT 24 LEFT SIDE ELEVATION ENTRY ELEVATION RIGHT SIDE ELEVATION REAR ELEVATION TYPICAL ELEVATION — OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE L BASEMENT PLAN 2,085 sq.ft. (APPROXIMATE) 1 st .FLOOR PLAN L 2nd FLOOR PLAN ATTACHMENT B5 FOSTERVIEW ESTATES HOUSE 'C' LOTS 6 -10 LEFT SIDE ELEVATION ENTRY ELEVATION RIGHT SIDE ELEVATION REAR ELEVATION TYPICAL ELEVATION — OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE -L_J 2nd FLOOR PLAN 1,838 sq.ft. (APPROXIMATE) 1st FLOOR PLAN UNFINISHED SPACE BASEMENT PLAN JUL 2 8 1993 C011r mUNITY OEN =LOF. LN • i.. r■ .r-• , U c FC>3TERVIEW ESTATES HOUSE 'D' LOTS 4,5,11,12,14-17,22,23 & 32 LEFT SIDE ELEVATION ENTRY ELEVATION RIGHT SIDE ELEVATION • REAR ELEVATION TYPICAL ELEVATION — OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE 1,390 sq.ft.(APPROXIMATE) BEDROOM #2 BEDROOM 11ASIER BEDROOM BASEMENT PLAN .,,_r -,, JUL 'Z 31993 GEV =LOP ,BEN 1st FLOOR PLAN ATTACHMENT' B5 FOSTLRVIEW ESTa-('ES HOUSE 'E'. LOT 1 ENTRY ELEVATION L_ J REAR ELEVATION J RIGHT SIDE ELEVATION LEFT SIDE ELEVATION TYPICAL ELEVATION — OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE 1,503 sq.ft. (APPROXIMATE) 2 CAR GARAGE C 0 UNFlNISNCD 1st FLOOR PLAN 2nd FLOOR PLAN' s.— • F05TERVIEW ESTATES HOUSE 'F" LOTS 20 & 35 LEFT SIDE ELEVATION ENTRY ELEVATION RIGHT SIDE ELEVATION REAR ELEVATION TYPICAL ELEVATION — OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE 1,449 sq.ft. (APPROXIMATE) L 2nd FLOOR PLAN JUL 2 8 1993 1 st FLOOR PLAN cc `'" ` uNiT' ATTACHMENT B5 FOSTERVIEW ESTATES HOUSE "G" LOTS 18,19,21,33 & 34 LEFT SIDE ELEVATION ENTRY ELEVATION RIGHT SIDE ELEVATION • REAR ELEVATION TYPICAL ELEVATION — OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE 1,365 sq.ft. (APPROXIMATE) BEOROO14 f OPEN TO BELOW J 2nd FLOOR PLAN JUL 2 3 993 1st FLOOR PLAN ATTACHMENT B5 FOS ERVIEW - ESTATES HOUSE 'H' LOTS 2,3,13,25 -31 LEFT SIDE ELEVATION ENTRY ELEVATION RIGHT SIDE ELEVATION REAR ELEVATION TYPICAL ELEVATION -- OTHER ROOF ELEVATIONS AVAILABLE — BRICK WAINSCOTE AVAILABLE 2nd FLOOR PLAN 1,970 sq.ft. (APPROXIMATE) 1st FLOOR PLAN JUL • 2 0 ►90 c�. 11 =5 :�.J� • 2 CM CAW( ..=•- C. . BASEMENT PLAN ATTACHMENT B5 JERALD K. BELL Landscape Architect 2127 NORTH 148TH STREET • SEATTLE, WASHINGTON 98133 • PHONE 362.9137 WETLANDS BUFFER ENHANCEMENT PLAN for Fosterview Estates, Tukwila, Washington CITY OF RECEI KWILA AUG 1 9 1993 PERMIT CENTER A. 1. Areas of Buffer Enhancement are shown on the Landscape Plan and include three small areas where proposed grading will encroach on the edge of the Wetlands Buffer area. 2. Additional Wetlands and Buffer Enhancement will be required to mitigate encroachment of the roadway for S. 137th Street, where it crosses the Wetlands and Buffers. The City has indicated that sizes and locations of this Enhancement are to be determined at a later date when additional information and details are available. B. Enhancement Plantings: 1. Proposed Enhancement Plantings will include a diversity of shrub and tree species planted within the wetland /watercourse buffer area. These species will be chosen for compatibility with the conditions of the site, with existing tree and shrub cover, and as habitat for wildlife. if necessary, it may include removing any existing non - native plants and replacing them with hardy native species. 2. Trees and shrubs to be planted in the enhancement areas could include some of the following species: Trees: Douglas Fir Western Hemlock Western Red Cedar possibly Sitka Spruce in wetter areas along 'the watercourse. also, Oregon Ash and Scouler Willow Shrubs: Oceanspray Vine Maple Indian Plum Salmonberry Red -osier Dogwood Pacific Ninebark Twinflower along the wet edges of the buffer C. Plant Maintenance: The Enhancement Plantings will be watered, fertilized and otherwise cared for, as necessary to keep them healthy and vigorously growing through their establishment period of one year. D. Guarantee: During the first year, or one full growing season, any plants which die or fail to become established and are not vigorously growing will be removed and replaced with tht same size and species as originally planted. BUCK & GORDON REC`IV .: 902 V6ni kmt Kuv PLAt1 • 1J :1 kNue jut 7 ,nry� SEArr:E,WASKINC:1om 96104.1(97 Jut ? ! gcet'1 3$1,954v • FAeSIMI:.t (200.) 626.0675 A:TOruNE''s AT LAW I'ETF.R 1.. RUCK BRENT c:AILSO\ tAYP.DERR IOCL. M. c.)Ultuc:)\ SHELLEY F... )C E;r AMY L. KOSTF.RLTZ KEITH E. 2.IOKON COMMUNITY DEVELOPMENT July 27, 1993 Ms. Denni Shcfrin City of Tukwila Department of Community Development 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 Or cot'ei. ALISON D. E TO11NC;1 -AM )`QAf)F.I.h:INli A.li JlU \N;It P,. licr MIt.N,. fl KATHRYN A OARD . P.E. Re: Fosterview Estates PRD and Plat; Conditions, Covenants and Restrictions Information Dear Denni; You have asked for information about the Conditions, Covenants and Restrictions (CC & R's) that will be adopted for Fosterview Estates, in accordance with your PRD ordinance, Section 18.46.110 (4) of the Tukwila Municipal code. That section requires submittal of "basic content of any restrictive covenants." We construe this to require, at this time, a basic outline of what the CC & R's will cover, rather than specific language provisions addressing all of the details. We believe our interpretation of what is required in terms of "basic content" is correct because your PRD ordinance later requires, in Section 18,46.115, that the specific content of the restrictive covenants intended to be used in a PRD be approved by the City Council and the City Attorney before issuance of a building permit. Your process thus contemplates that the detailed provisions of the CC & R's would be reviewed and approved not prior to PRD approval, but prior to building permit issuance. In this case, where a subdivision is involved, the logical time for City Attorney and City Council review of detailed CC & R provisions would be at the time of the City Council's approval of the final plat. The approach of giving basic information at this time will allow you to make it a condition of final plat approval and/or of building permit issuance, that detailed CC 6; R's, covering certain basic areas, be drafted and approved by the City Attorney and City Council. In addition, as your PRD ordinance recognizes, detailed drafting of the CC & R's at this stage is not possible because we still do not have approval of our design through the PRD and preliminary plat. ATTACHMENT D July 27, 1993 Accordingly, the basic content of CC & R's for the development will include: (1) A definition of common areas or sensitive area tracts and how these are to be utilized, maintained or preserved; (2) The creation of a Homeowner's Association to which the common areas or sensitive area tracts will be conveyed, with responsibilities and restrictions on how these areas will be utilized, maintained or preserved Rights retained by the Declarant regarding administration of the property, with transition provisions to the Association (3) (4) Restrictions on use of the property for residential purposes, with design restrictions regarding fences, landscaping, signs, keeping of animals, disposal of trash, quality of exterior finish of buildings, etc., in order that the development present a uniform and aesthetically pleasing appearance, and the Association's responsibilities regarding enforcement of these restrictions, including the establishment of an Architectural Control Committee (5) Regulations for establishment of the Association and conduct of its business, including voting rights therein, bylaws, meetings, etc. (6) Provisions for monetary assessments by the Association to fulfill its duties of maintenance of common areas and its other responsibilities Provisions to make these requirements covenants running with the land and dealing with enforceability We hope that this is satisfactory. Please give me a call if you have any questions. Very truly yours, (7) cc: Bill Fowler D4lardtn107:73, afk ((slit LX Amy L. K terlitz .CITY OF TUKWILA MITIGATED DETERMINATION OF NONSIGNIF- '.ANCE (MDN'S) IPe» ,DESCRIPTION OF PROPOSAL: FOSTERVIEW ESTATES I5 A PROPOSED 41-LOT •RESIDEN- TIAL DEVELOPMENT ON A 10 -ACRE PARCEL. THE SITE BOUNDED BY 'SOUTHGATE .PPRt': TO THE NORTH, 43RD £w. S. AND 44TH AV. S. TO THE EP.ST AND 42ND AV. S. TO THE WEST. MITIGATION CONDITIONS AND EXHIBIT'S A, B, & C ARE ATTACHED. PROPONENT: DLIJARDIN DEVELOPMENT' EVELOPMEN T ' ,COMPANY- LOCAT ION OF PROPOSAL, INCLUDING STREET ADDRESS, IF ANY: ADDRESS: PARCEL NO:... 152304 -9078 SEC! T WN/RNG: SE 15 23N 04E LEAD AGENCY:: CITY .0F TUfWILA FILE NO: L92 -0066 2 The City,.has ,determined that the proposal. does not have a- probable significant adverse` i mpacr. . on the environment. An environmental impact stateMent (EIS.). :s no, r"equir"ed under RCW 43.21c.0 ?0(2)(c). This ' deec.is;orr was made .after review of a completed environmental checklist and other informat ior;, on file with the lead agency.. This is information is available the ,public on request. The :conditions:to this '_,EPA Determination ..are :attached_ ... Th s DNS is issued under 197 -11- 340(2). Comments must be submitted 'by Rick Beeler, P._cpcnc.ble Official City cf Tukwila, (206) 431 -_'680 _=CC Scuthcenter Boulevard T . Lw i l e. , WA 93288 Data 1.::u may appeal this determination to the City Clerk at City -rail , 62010 Southcenter Boulevard, Tukwila, WA 93188 no late; than 10 day from the above signature date by written appeal stating the basis of the appeal for specific factual objections. You may be required to bear some of the e,.penses fc'. an appeal. _ of ;he prcoedures for SEPA appeals are available with the City :el-i. and Department . . (:C';1ri11un i t y Development. ATTACHMENT E City of Tukwila John W. Rants, Mayor Department of Community Development Rick Beeler, Director AMENDED SEPA MITIGATED DETERMINATION OF NONSIGNIFICANCE FOSTERVIEW ESTATES L92 -0066 Project Description. Fosterview Estates is a proposed 41 -lot residential development on a 10 -acre parcel in the urban City of Tukwila. The project includes the westerly extension of South 137th Street from the intersection of 44th Avenue . South west across the site to connect with 42nd Avenue South. .A total of 21 single -family lots (Lots 1 through 21) and a cul -de -sac (South 137th Place) are planned for the north side of South 137th Street. Another 14 single- family residential lots (Lots 22 through 35) and a small north -south residential street (43rd Place South) are planned for the west portion of the site on the south side of South 137th Street. There would be six lots (Lots 36 -41 situated immediately south of South 137 Street on the east side'of the site. These lots are bounded on the west and south by a designated wetland area (Tract B). A watercourse area (Tract A) lies to the north of 137th Ave. S. opposite Lots 36 -41. The average lot size would be approximately 5,000 square feet in area (see Vicinity Map - Exhibit A attached). Several technical studies have been submitted as part of this project and are referred to later is this report. SEPA conditions as specified below are in addition to conclusions and recommendations contained in these technical studies. The property is not on the State registry of historic significant archeological sites. Community meetings were held on July 30 and August 3 and 10, 1993, to review the proposal and the SEPA process. Additional reports regarding traffic and storm drainage impacts were submitted which are referenced below. The public comment period was extended to August 13. As a result of this additional information this MDNS is hereby amended to read as follows: Site Conditions: The topography is variable. The north and northeast portions of the site excluding proposed Tract B are sloped moderately to steeply downward ranging between 15% to 65% in grade. The west portion of the site slopes gently to moderately north and northeasterly with grades of approximately 15% to 25 %. Lots 36 -41 would be located on moderately to steeply sloping areas of approximately 20% 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • 1206) 431 -3670 • Fax (206) 431-3665 Fosterview Estates Page 2 SEPA - L92 -0066 to 35% grades. Lots 40 and 41 are proposed to be terraced. In addition to slopes in excess of 15% grade, the site also contains a wetland and a watercourse. Forty-fourth Avenue South extends north from S. 139th St. to approximately S. 137th St. At this point, the roadway becomes 43rd Ave. S. Both 43rd Ave. S. and 44th Ave. S. abut the site to the east. Due to land movement evidenced by displaced pavement, 43rd Ave. S. has been barricaded and closed to vehicular use. This abandoned roadway is located along the west side of a narrow, steeply sloping ravine that drains to the north. The City has adopted special ordinances which regulate development in environmentally sensitive areas. These ordinances include the following: 1. The Sensitive Areas Ordinance 2. Planned Residential Development (allows for unit clustering to avoid sensitive areas); 3. The Tree Preservation Ordinance 4. Land Altering Ordinance 5. Building Permits (includes geotechnical review) Under the City's Sensitive Areas Ordinance (SAO), encroachment into designated environmentally sensitive areas as defined by the SAO is permitted for essential roads and utilities provided the impact to these areas is minimized. The proposed subdivision street system would encroach onto the wetland area at the street intersection, however, the impact would be minimized due to the 90- degree -angle design. The roadway would share other utilities including sewer and water. Under the SAO, the impacted area will be restored. A wetlands mitigation plan will be provided to and approved by the City prior to the Preliminary Plat approval by the Planning Commission. Sufficient wildlife habitat will be provided in the proposed sensitive areas and their buffers to accommodate most of the existing wildlife. The mitigation plan will include the following: a. The approximate amount of clearing and grading proposed for the roadway crossing at the watercourse and any grading within the associated wetland/buffer areas; b. Proposed vegetation including trees to maintain or improve the value of the impacted area as recommended by the City's Urban Environmentalist; c. Proposed maintenance plan to assure mitigation success, which could include dedication of sensitive areas and their buffers to the City. Fosterview Estates Page 3 SEPA - L92 -0066 Because the internal street system proposes to cross the watercourse, a Hydraulics Permit (issued by the Department of Fisheries) is also required with this project. Potential impacts to the following have been identified: 1. DRAINAGE; 2. TRAFFIC: vehicular and pedestrian; 3. SLOPE STABILITY; 4. ON -SITE WETLAND. DRAINAGE. The following technical studies prepared by Erich O. Tietze and Associates, Inc. Engineers and Consultants were reviewed by the City: 1. Drainage Analysis Received March 15, 1993 2. Criteria to Be Used in Drainage Design for May 12, 1993 Fosterview Estates 3. Off -Site Drainage Analysis for May 12, 1993 Fosterview Estates 4. Drainage Basins Maps of Existing and Future Drainage Received August 10, 1993 At the City's request, an independent review of the adequacy of the drainage system as proposed, has been conducted by Hammond, Collier & Wade - Livingstone Associates, Inc. (HCW -L). In their memo to the City dated June 28, 1993 (hereto, made part of this record), HCW -L was requested to evaluate whether there would be increased runoff on the property to the north; to provide recommendations for sequencing and phasing for project construction; relocation of the north property swale, and to recommend erosion control measures to control clearing and erosion potential. Recommendations of the June 28, 1993 HCW -L review shall be adhered to in the design and construction of the project unless otherwise agreed to and approved by the Departments of Public Works and Community0 Development. On August 13, 1993 the City Engineer reported that the impact of underground springs on the property can only be determined when construction of the proposed roads occurs. This will require updating the storm drainage system design for 43rd Ave. S. at the time of grading the roads. Fosterview Estates SEPA - L92 -0066 Mitigation Conditions: Page 4 . 1.. Wet vaults in addition to a biofiltration swale shall be constructed. The bioswale assists in the removal of conventional pollutants while wet vaults provide for some filtering and settlement prior to discharge into the proposed drainage system. The biofiltration swale shall be located within the 43rd Avenue S. right -of -way. Shade - tolerant plant species shall be used to ensure plant survival and function of the biofiltration swale. Wet vaults shall be easily accessible by maintenance vehicles and designed in accordance with the King County Surface Water Design Manual. 2. All runoff and drainage from the on -site drainage system shall be discharged directly to the proposed storm drainage improvements proposed on 43rd /44th Ave. S. right - of -way. The spreaders shown on conceptual plans shall be omitted. The final design of the system will be updated to accommodate underground springs volumes uncovered during construction of the roadways. TRAFFIC - VEHICULAR. The following technical studies have been prepared by Gibson Traffic Consultants and submitted with this project: 1. Traffic Study 2. Resolution of Traffic /Access Issues (includes guardrail analysis) 3. LOS. Safety & Livability Impacts of 137th "Through" Street April 27, 1992 December 10, 1992 August 9, 1993 The conceptual site plan proposes three lots to be accessed by a single driveway onto 42nd Avenue South on the northwest corner of the subject property. Forty- second Avenue South curves left and descends along the side of a hill. The City will be improving 42nd Ave. S. to include curb, gutter and sidewalks beyond the project. The sight distance for motorists on 42nd Ave. S. and proposed S. 137th St. meets engineering safety standards. A guardrail analysis for 42nd Avenue S. has been provided at the request of the City Engineer. The analysis concluded that a guardrail would not be required and referenced the American Association of State Highway and Transportation Officials (AASHTO) standards including presence of curb, gutter and sidewalks. However, the City Engineer has concluded that a guard rail is required (per memo from Ron Cameron dated July 1, 1993). The City Engineer has determined that AASHTO standards are superseded based upon the following factors: .� a. The need for the guardrail is based upon the geometric evaluation of the relationship between the project design and 42nd Ave. S.. Fosterview Estates Page 5 SEPA - L92 -0066 b. There is high potential for errant vehicles to cross the sidewalk, jump the bank and hit yards and /or homes below; c. Other examples of homes being hit where adjacent to road curvatures have occurred both in Tukwila (139th Ave. S.) and in Everett, WA. Mitigation Condition: 1. A guardrail shall be installed along 42nd Avenue South immediately north of the S. 137th Street access point into the subdivision as shown on drawings received April 26, 1993. TRAFFIC - PEDESTRIAN. The project proposes the extension of S. 137th St. westward from 43rd Ave. South to 42nd Ave. South. The existing neighborhood consists of 40 homes. The 41 -lot subdivision will generate additional pedestrian traffic along S. 137th St. for both transit and school bus access. The 137th roadway in its current condition is narrow, approximately 18 -20 feet wide, with no provision for pedestrians. Pedestrians use this street to access bus service available on Macadam Road. The increased pedestrian traffic and vehicular traffic along 137th related to the development proposal would result in decreased safety for pedestrian and vehicular traffic Because S. 137th St. does not currently provide adequate pedestrian access for the 40 homes, the City agrees to pay 1/2 the total amount of construction costs for walkway improvements. Because the additional trip distribution is relatively equal (41 homes) to what is existing (40 homes), the developer will be required to pay a fair share contribution as specified below under Mitigation Condition: Mitigation Condition: 1. A pedestrian walkway shall be installed along S. 137th Street from 44th Avenue South to Macadam Road. The City shall be responsible for the design and installation of the walkway and drainage improvements. The applicant shall reimburse the City for 1/2 of the total amount of construction and inspections costs. Based on pedestrian path costs of the last two years, the anticipated cost would be a total of $60,000. The total amount to be paid by the developer shall be $30,000. Improvements include 750 lineal feet of walkway with drainage (covering the ditch for the pedestrian path) needed for about 2/3 the length. The pedestrian path unit costs have averaged $18 /foot and drainage costs have averaged $33 /foot at 500 feet. Fosterview Estates Page 6 SEPA - L92 -0066 SLOPE STABILITY. The following technical studies were prepared by Terra and Associates, Inc. ( Geotechnical Consultants) and submitted as part of this project proposal: 1. Geotechnical Report 2. Geotechnical Report Update 3. Geotechnical Report Update 4. Geotechnical Conditions 5. Provisions for Erosion Control August 11, 1990 May 5, 1992 December 22, 1992 February 23, 1993 June 30, 1993 A site reconnaissance, subsurface exploration and slope stability evaluations regarding the site, and in particular, the existing land movement on 44th Avenue South, and stability issues have been addressed by the applicant's geotechnical engineer in an initial report and subsequent analysis. Due to the sensitive nature of the site and evidence of previous land movement adjacent to and off -site, a peer review of the geotechnical analysis was conducted by Applied Geotechnology, Inc. (AGI). While the original report provided by the applicant indicated the site slopes in their present condition appeared to be generally stable, AGI concluded that these slopes have potential for landslides due to the extensive site grading planned for the proposed development. Mitigation Conditions: Prior to Issuance of Land Altering Permits 1. To avoid future slope instability both during and after site development and to ensure proper construction of cuts and fills, the applicant shall provide a slope stability analysis which demonstrates that the proposed fills on slopes, to be designed, are stable. The analysis shall accompany applications for land altering permits and shall be evaluated by peer review prior to permit issuance. Should the results of the stability analysis require significant design changes to the Preliminary Plat, the Preliminary Plat must be revised and new hearings shall be required. 2. A geotechnical engineer of record shall be retained throughout the construction Fosterview Estates Page 7 SEPA - L92 -0066 phase(s) of the project and shall monitor earthwork and review the final design and building specifications for all lots to assure conformance to the recommendations contained in the geotechnical reports prepared by Terra and Associates as listed on the previous page. 3. The developer's engineer shall prepare for review by Terra and Associates, and the City, detailed cross sections in all planned fill areas indicating how the fill will be keyed, benched, and drained as recommended in the Terra geotechnical report. A typical detail shall be prepared illustrating the geotechnical engineer's recommended key at the toe of all proposed fills on slope. Calculations supporting adequate safety factors against slope instability shall be provided for review by the City. 4. The developer's engineer in conjunction with the geotechnical engineer shall prepare detailed design cross - sections addressing subdrainage provisions for fills placed on slopes and underlain by lacustrine deposits. 5. The developer's geotechnical engineer shall review the foundation details and comment on the need for connecting individual footings or supporting the houses on post- tensioned slabs as a possible means of reducing potential for differential settlement of the structures. 6. Construction monitoring by the geotechnical engineer shall be provided, with written confirmation provided to the City that all work has been performed in accordance with the geotechnical recommendations. 7. The proposed earth cuts and rockery along the existing road right -of -way for 42nd Ave. S. (behind Lots #1, 2 & 3) shall also be reviewed by the geotechnical engineer to assure lateral stability of the existing roadway and the new road and utility improvements. During Construction 8. Boundaries of Tracts A and B (as shown on Exhibit C) shall be flagged and fenced to prevent intrusion during construction. Sloped areas (Exhibit. C) shall also be delineated and a barrier fence erected prior to clearing and grading. Fencing locations shall be inspected by the City prior to land clearing. All fencing damaged due to construction shall be immediately replaced during the construction phase. 9. Grading activity shall be outside of the dripline of preserved trees as shown on the approved landscape plan. 10. Vegetation to be retained per the approved landscape plan shall be replaced at a 2:1 Fosterview Estates SEPA - L92 -0066 ratio if disturbed during any phase of construction. Following Construction Page 8 11. Permanent visible markers shall be placed to delineate the boundaries of Tracts A and B where adjacent to single - family lots and rights -of -way. EXHIBITS: A. Vicinity Map B. Preliminary Plat Map C. Sensitive Areas Delineation Map Planning Commission City of Tukwila. A U 1 (;.::3 . J... •J .. +1 •.�J1 �. Ji..:.V J Aug. 19., 1993 We would like to bring into consideration a matter which has not yet be addressed and is of concern to us as the property owners immediately adjacen to the northern boudary of the proposed Fosterview Estates. The Riess -Loyd property line mans 277 ft. east to west from 43rd Ave. S, to the eastern edE of Southgate Park., and then north along the park for 150 ft. On the propoee Plan a crushed -rock access road, leading to an open concrete walkway are placed immediately next to our property, an area'which is currently densely covered with mixed trees and other natural vegetation. In accordance with the Tukwila Zoning Code 18.46.090 Relationship to Adiicent are ..: "...The perimeter of the PRD shall be eo designed as to minimize any undesirable impact of the PRD on adjacent properties ", we would like to see included in this plan a permanent fence between the path /road an our property. According to the proposed design, up to 7 residences could be located adjacent to our property. The concrete path angles through several of the sites from the cul -de -sac to the approximate mid -point of our property, the latter.which elopes downhill from the sidewalk. (see attached map) This is hot a neutral yard -to -yard boundary, but one in which pedestrian and bicycle traffic will be led along our perimeter. The western part of our property provides a natural setting; there is nothing to distinguish it from park property. Indeed, some maps of the proposed development label the northern off -site area a generic "Southgate Park", which is not the case. We do not want our property to be treated as an extension of the park. The crushed -rock access road that runs along our property line from the sidewalk eastward to•43rd Ave. S. will be covering the main storm drain pipe This will be. approximately 30 ft.. upslope from our house. It will also sery as an extension of the pst.h and could provide access to the park for those park on 43rd Ave. S. The points listed about the sidewalk are especially applicable here. Overall, we are concerned about security, liability, privacy and noise. Introducing the element of public access for 277 ft.. of our property length and 150 ft. bordering Southgate Park, increases the likelihood of trespass, especially when our land is so visible and inviting, being downslope. We wi. have to worry more about casual and planned theft and vandalism. Even the seemingly mundane issues of trampling of vegetation and picking up litter wi: affect us. Our property contains outbuildings, some small garden pools and hot tub. We do not wish to assume liability for errant trespassers_. We currently enjoy a good deal of privacy. Frankly, it is hard enough think of 7 houses overlooking our home, but to guide people along our proper• is overwhelming... ``.. • The negative impact of this on our home would be substantial. In order to provide some amount of security and privacy, we request that a fence be included in the final plan, built to the maximum height allowed, and borderi: our property the full length along which our properties meet. Thank you for your consideration of our concerns. Sincerely. 42/% Pam�'R'is LFP Loyd PAGE.002 TO B*4313665 FRU.' KING CO LIBRARY cr SOUIIICATE PARK pt's- L0.141 proriely trrr- WI • ''••■ .., ,* t'• • 4 ..• • 'S s • ' s , `... ....i.....•. L' : •: ••.7 .: ..'. .1 .4C'"•.••• ;X.• v. • .. . *.I-. ,. -.. - .. .„. i..- : !-. /.• .'.: .'4' . 1.■ ..4 . "4 . C * ..■• -.. . • t.-,i.._ .f„..1 ,, .. . , I,t.A , ./. , ..... . • 1 c & • . - s . • •• It "” -....2 ... 1 1 6. • IV : VI . .1,.10..4 . )1.1 . w .e : gi s.r . . %"It.. .• . . , ..,.. ....AC..,;.! ..1.!. . . .".. .\. • ‘:,.!•,;., • - .: - - .. . - . , 116 .,.. . . 7 .. ::d:;. 44 r - .:4• .1: :.-....'. N . /. 1,I ii 1; . .\ .; :l11 . • — .. .\ .-1 jil , • 4, 1 44) ir ei - - ›N . ,. .,. . ..,.._.,, . . . 4 - .• 1 1 5 1' ,i , z- ' 2 :z 0,4 4 VI. 7: ..• i .,;" .• .::: •,..,.:S.k. •,.,k,,..S.,l . .N. • •Cs •••••• •.11I vsli 44 Off ••• sithl.Cf-Alr 10 II weatilt, •?. ,001 si IC • ...KW's! 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Macadar,, Rd Tukwila, WA =E168 To: Planning C•ommi.s=i.or; /Ci.ty :c.unci.l Re: Fosterview Estates Date: 'august 18th, 19113 I am concerned with the impact the Fostervieww Project will have on my neighborhood, and with how the city address the following issues. It i= not my desire to see the Fosterview Project defected. However, 5S a Foster area resident, living on Macadam road, it is my duty to help ensure the safety and qual i.ty of life for all who .use this street. No development this size can help but impact the neighborhoods surrounding it. The Traffic consultant hired by the developers was not realistic about the utilization of Macadam road. To be sure the residents of Foster View will .find the shortest WE way to the freeway which, from their development, will be to go east on 137th St., north on Mecadar,;, east on 136th Et. and then directly onto the South- bound I5/405 entrance or proceed to the northbound I -5 or I- 599 entrances via Interurban Ave. You should be aware that there is a school bus stop on Macadam road at 1371.h, and a Metro bus route with e.. passenger loading ere= at 136th. There i.= no . ode: tri _n path, no cross-walk and very limited line of site for vehicle operators traveling Et this multi- :tr'e:t intersection. f r e q u e n t l y bee rve automobile: t r y i n g to n e g o t i a t e the sharp r . a .r e _ near t h i s i n t e r s e c t i o n et : j:: p r" :. i. rr, a t e] L% double the legal speec! It is my hope that the Planning Lepe.rtment will be pr.:'- acti := with the c.7 ]lenge= that the Toeterview Fr :;e:.t will create tc these cf us Jiving near This very de.n_er_.us intersection 'with the s:fet. of r. y neighbors in mind, my suc_;ee t i ens include: 1) Ped path or s.idew=.lk should be installed on east side cf J• a sadam gunning from 1:,6th St. to 137th Ft. ") Sidewalk or ped path should line 137i.h Ft. from Fosterview to r'iac_ dam rc._.d 3) Ped crossing should be marked at 137th, crosei;:_ Macadam. �. Ped path :r Sidewalk .houl.d be in-t el led on 136th, e st of M E C E d E Th r o a d :) All bus steps Uie trc and s:h , 1) s.h: uld to well marked ith clear lines and safe z n. ..,r p_i..sr,;7er_ to st.nd h� 6 ) F i. ] n e ' 7 e shoulj i d e n t i f y a t' _ c m i n _,i ped o r e se iris = end bus • , r'" stops. /�� /�(� 11\-1 !' / 1 �\ PRELIMINARY PLAT APPLICATION FOR STAFF USE ONLY Planner: 0, File Number: L-9 DO (4‘ Cross - Reference Files: Pc) Z-00°1 Receipt No.: L97. • o�&5 L`1 z • Oo(v [r 1. Name of Preliminary Plat: Fosterview Estates 2. Date of preliminary plat approval: 3. Describe any proposed deviations from preliminary plat: N/A 4. APPLICANT:* Name: Signatur Dujardin Development Company Address: P.O.Box 5308 Everett, WA 98206 Phone: (206) 334 -5018 Date: 3/12/93 "' The applicant is the person whom the staff will contact regarding the application, and to whom all notices and reports shall be sent, unless otherwise stipulated by applicant. AFFIDAVIT OF OWNERSHIP 5. PROPERTY Name: Dujardin Development Comapny OWNER: Address: P.O. Box 5308 Everett, WA 98206 Address: Phone: (206) 334 -5018 I /We f Signature(s)) " ' . v/� swear that I /we are the owners) or contract purchaser(s) of the property involved in this application and that the foregoing statements and answers contained in this application are true and correct to the best of my /our knowledge and belief. ATTACHMENT G PRELIMINARY PLAT APPLICATION Page 2 6. SIZE OF LAND TO BE SUBDIVIDED: Approximately 10 acres 7. ZONING: R -1 7200 8. NUMBER OF PROPOSED LOTS: 41 lots 9. IS ANY OF THE PROPERTY IN FLOOD ZONE "A "? No 10. ARE THERE ARTY EXISTING STREAMS, WATER BODIES, MARSHES OR BOGS ON OR WITHIN 100 FEET OF THE SUBJECT PROPERTY? Yes, there is a creek that flows from the middle 6 ;the south property line, to the northeast a distance of about 340' then turns to the east and flows off the property. 11. ADJACENT LAND USES: NORTH: SOUTH: EAST: WEST: R -1 (7200) - Southgate park & single family residences RS 7200 - Single family residences R -1 (7200) & RS 7200 - Single family residences R -1 (7200) - Single family residences 12. DO NEIGHBORING PROPERIIES HAVE SUITABLE ACCESS? Yes CITY OF TUKWILA PLANNED RESIC. .4TIAL DEVELOPMEN` APPLICATION DEPARTMENT OF COMMUNITY DEVELOPMENT 6300 Southcenter Boulevard, Tukwila, WA 98188 Telephone: (206) 431 -3680 'r �ww i. � �wr -w�u. •r :. __ _. E! k �.l'!1 /L?':f�_. .:c A:i ence. 00 s 1. NAME OF THE PROPOSED DEVELOPMENT: Fosterview Estates 2. NUMBER OF DWELLING UNITS: 41 single family lots 3. ZONING OF SUBJECT SITE: Single family 4. PROJECT LOCATION: (Give street address or, if vacant, indicate lot(s), block, and sub- division; or tax lot number, access street, and nearest intersection) Approximately 10 acres between 42 Ave. S. & 44th Ave. S. and 137th St. Quarter: SE Section: 15 Township: 23N Range: 04E (This information may be found on your tax statement) 5. APPLICANT:* Name: Duiardin Development Company Address: F. 0. Box 5308, Everett, WA 98206 Phone' (206) 334 -5018 Signature: Date: May 6, 1992 * The applicant is the person whom the staff will contact regarding the application, and to whom all notices and reports shall be sent, unless otherwise stipulated by applicant. 6. PROPERTY Name: OWNER AFFIDAVIT OF OWNERSHIP Dujardin Development Company Address: F. 0. Box 5308, Everett, WA 98206 Phone: o061 134 -5018 I /WE,[signature(s)] RECEIVEE swear that I /we are the owners) or contract purchaser(s) of the property involved in this application and that the foregoing statements and answers contained iis1 3 1992 application are true and correct to the best of my /our knowledge and belief. Date: COMMUNITY May 6, 1992 DEVELOPMENT ATT'Af`HMFNT r= PRD APPLICATION Page 2 7. IF REQUESTED, PLEASE EXPLAIN HOW THE REQUESTED DENSITY BONUS FOR THE SUBJECT PROPOSAL MEETS THE FOLLOWING CRITERIA. A. At least fifteen percent of the natural vegetation is retained (incases where significant stands exist). RESPONSE: All of the wetlands except that portion where the new street crosses the stream and the required buffers shall remain in irs nntnral 1 "eg.etation. This consists of 26% of the site. B. Advantage is taken of unusual or significant site features such as views, streams, or other natural characteristics. RESPONSE: The wetlands and required bu' •ers shall be left in their nntnrn1 state. A nature trail could be put in along the stream. A large portion of the lots are so located that they will have a good view to the east. The development will allow easier access to Southgate Park for residences to the east of 44th Ave. C. Separation of auto and pedestrian movement, especially in or near areas of recreation. RESPONSE: Sidewalks will be provided to give access by pedestrians from the adjacent residential property to the east to Southgate Park. PRD APPLICATION Page 3 D. Development aspects of the PRD complement the land use policies of the Comprehensive Plan. RESPONSE: The development is producing hnuGing similar to that oxictin„ in the adjacent areas. It will give a traffic and pedestrian outlet or inlet to 42nd Ave. South from the area on 137th that lies east of 44th Street and it will assure that the existing wetlands will be retained and made available to the general public as determined adequate by the city. E. Some extraordinary public benefit is derived in exchange for the reduced minimum lot size in the planned residential development. RESPONSE: By the use of smaller lot sizes, it does make it possible to retain the existing wetlands and buffers, yet allows the developer to have enough lots to be able to make the project financially feasible and still keep- the land sales price comparable with existing lots in the area. IN ADDITION, FOR MULTIPLE- FAMILY DENSITY BONUS REQUESTS: F. A variety of housing types are offered. RESPONSE: Nnr applicable PRD APPLICATION • Page4 8. WILL THE PROJECT BE COMPLETED IN PHASES? 0 Yes © No If yes, please describe proposed phases and time frames. 9. PLEASE DESCRIBE THE OWNERSHIP PATTERN FOR THE PROJECT. 41 single family homes will be constructed and sold to individuals. 10. PLEASE DESCRIBE THE DETAILS OR LIST ANY RESTRICTIVE COVENANTS PRO- POSED FOR THE.PROJECT. (This must be incorporated into your proposal and may only be recorded after review and approval by the City Attorney and City Council.) None anticipated 11. HOW WILL THE COMMON OPEN AREAS AND RECREATION AREAS BE MAIN- TAINED? !?e d nern rea3 -ta � meted- -Git -e - �vki.Ti a CtTY OP TUKWILA • DEPARTMENT OF COMMUNl7'Y DEVELOPMENT BOUNDARY LINE ADJUSTMENT OR LOT COQ, )LIDATION APPLICATION i.� '• \,'�.. �kM' of 6.300.3outhcenter Boulevard, Tukwila, WA St 188 Telephone: (206) 431-3660 APPLICANT Name;. Address: Dujardin Development Co pany P. 0. Box 5308, Everett, WA 98206 City, Everett Signature: • LOCATION Street Address: Zip: _ 98206 Phone: V14 -501 R Date:_Auust il, .1992 Approximately 10 acres between 41nd Ave. S. & 44th Ave. and 137th St. If vacant; indicate lot(s), block and subdivision; o.tax lot number, access street, and • nearest intersection, SE PARCELS Zoning District Existing Use • Proposed Use Proposed Lot Size QUARTER A J 1 .15 j i 23N SECTION 8 j R -1 7.2 1 R -1 7.2 residential vacant residential 1 vacant 13,299 ._. ... I] ATE OE LAST PLAT: t ©.� 4 04E ! RANGE C I j ' ! 1 1 1 1 1 r RE sq /ft1 approx. 10 acres subdivided various sizes 1JG .1 3 1992 err. CUvMVNITY r�iTICT1d12v T T►� ATNT t4't'►fi =Arm .nrIXTO. t ' jEV ELOMIEN T c L ' is r ' z A nA� HMENT= G = AFFIDAVIT OF OWNERSHIP DECLARATION: On this day personally appeared before me to me known to be the individual described in and who executed the within and. foregoing in- strument, and acknowledge that signed the same as • free and voluntary act and deed, for the uses and purposes therein mentioned. G1VEN under my hand and official seal this day of ,19 Notary Public in and for the State of Washington, residing at Page o • DEPARTMENT OF COMMUNITY DEVELOPMENT , , ._, PORTION OF GOVERNMENT LOT 2, "' 110N 15, TOWNSHIP 23 NORTH, RANGE 4 EAST. FOR COMPLETE MAP OF PARCEL B l /� SEE HEBRANK AND ASSOCIATES DRAWING ENTITLED " DUJARDIN DEVELOPMENT COMPANY', DATED APRIL 6 1990 AND REVISED AUGUST 3 1992. NORTH 0 10 20 30 60 90 S C A L E 1" = 30' PARCEL B f e "/74- i a rcr /io:l: vc --1y '1 s rS. 8 /NODD ,`Nall\ J.2' f 4f;; CO.PNf.P 1 87' 48' 28' W, etweRtrilezps 140.03' \ 2' r I i 6ARR6l < /q!A'ZINKffHC!-' re) 0) cg SPNAC7 �4fN�Y�e� li - "t t and 1OUSE Augur ,IsoR rt. 214.3 J J(..Irr 11.• loi•i RoCR'Rr Y- - -• r>s 1-0.2'— 1 L501/71/ IJNl 6. C. ,z "*'r�i /E0.03= ____ N 87' 48' 28 W 1W 140.03' C O M M E N T S 566. er QZ' Easements. Lf any, are not shown hereon as no title report was prodded. Ter surrey control and moaumeatation see survey recorded it Book 73 of Surveys at pages 114 and 114A. records of nag County, Washlagtc. Field data for this survey was obtained ►y direct Yield measwreineaL Angular relntiosuhips and dintaaces were measured with a Topcoa CTS-2 aad suppiemented with • 100' steel tape both last calibrated 23 March 1992 at the Sand Point baseline. The area of PARCEL A prior to adjustment Ls 12.041 square feet and after adJustaneat is 13.091 square feel The area of PARCEL B prior to adjust. oeat is 428.560 square feet and after adjustment is 427.510 square feet. Lena Surveyor's Certificate: This boundary line adjustment correctly represents c survey mode by me or under my direction to conformance with the requirements of cppropriate state and county statute and ordlnonce. 4.744.14 /5f2. Dote Certificate No. Signature 7559 .3 A•fv a� /97o. Pope _ of DUJARDIN - OLSON BOUNDARY LINE ADJUSTMENT DESCRIPTIONS Parr_E1 The east 140.02 feet of the west 586.69 feet of the north 86 feet of the south 684 feet of Government Lot 2, Section 15, Township 23 North, Range 4 East, W.M. in the City of Tukwila, County of King, State of Washington. Parcel A afte" adiu'tment The east 140.02 feet of the west 586.69 feet of the north 93.50 feet of the south 691.50 feet of Government Lot 2, Section 15, Township 23 North, Range 4 East, W.M., in the City of Tukwila, County of King, State of Washington. Parcel B prior to ad.iustment That portion of Government Lot 2, Section 15, Township 23 North, Range 4 East, W.M., in King County, Washington, described as follows: Beginning at the northwest corner of said Government Lot; thence easterly along the'north line thereof 586.69 feet; thence southerly parallel with the west line of said Government Lot a distance of 594.05 feet, more or less, to the north line of the south 684.00 feet of said Government Lot; thence westerly along said north line 283.34 feet, more or less, to the northwest corner of a tract of land deeded to Ralph A. Olson and Reatha Olson by deed recorded under Recording.No. 5089251; . thence south along the west line of said deeded tract a distance of 20.00 feet to the north line of the south 664.00 feet of said Government Lot; thence westerly along said north line 303.34 feet, more or less, to the west line of said Government Lot; thence northerly along said west line 606.50 feet, more or less, to the Point of Beginning; EXCEPT that portion thereof condemned for F. J. Folkendahl Road in King County Superior Court Cause No. 21426; AND EXCEPT those portions thereof 'deeded to King County for Charles E. Adams Road (42nd Avenue South) by deeds recorded under Recording Numbers 472354 and 5558464; TOGETHER WITH that portion of Tract 67, Riverside Interurban Tracts, according to the plat thereof recorded in Volume 10 of Plats, page 74, in King County, Washington, lying northeasterly of 42nd Avenue South as deeded to King County by deed recorded under Recording Number 5655246; EXCEPT the east 20 feet thereof deeded to King County by deed recorded under Recording No. 1207877; AND EXCEPT the north 350.00 feet thereof; TOGETHER WITH that portion of Government Lot 3, Section 15, Township 23 North, Range 4 East, W.M., in King County, Washington, lying northeasterly of 42nd Avenue South as deeded to King County by deed recorded under Recording No. 5655246; EXCEPT County Roads; TOGETHER WITH that portion of `.Tract 19, Fostoria Garden Tracts, according to the plat thereof recorded in Volume 9 of Plats, page 95, in King County, Washington, lying southwesterly of F. J. Folkendahl Road (43rd Avenue South) as condemned in King County Superior Court Cause No. 241626. HEBRANK & ASSOCIATES File 92046 3 August 1992 • DUSARDIN - OLSON BOUNDARY LINE ADJUSTi11NT DESCRIPTIONS (continued) Parcel B after ad.iustment That portion of Government Lot 2, Section 15, Township 23 North, Range 4 East, W.M., in King County, Washington, described as follows: Beginning at the northwest corner of said' Government Lot; thence easterly along the north line thereof 586.69 feet; thence southerly parallel with the west line of said Government Lot a distance of 594.05 feet, more or less, to the north line of the south 691.50 feet of said Government Lot; thence westerly along said north line 140.03 feet to the east line of the west 446.67 feet of said Government Lot; thence southerly along said east line 7.50 feet to the north line of the south 684 feet of said Government Lot; thence westerly along said north line 143.34 feet to the northwest corner of a tract of land deeded to Ralph A. Olson and Reatha Olson by deed recorded under Recording No. 5089251; thence south along the west line of said deeded tract a distance of 20.00 feet to the north line of the south 664.00 feet of said Government Lot; thence westerly along said north line 303.34 feet, more or less, to the west line of said Government Lot; thence northerly along said west line 606.50 feet, more or less, to the Point of Beginning; EXCEPT that portion thereof condemned for F. J. Folkendahl Road in King County Superior Court Cause No. 21426; AND EXCEPT those portions thereof deeded to King County for Charles E. Adams Road (42nd Avenue South) by deeds recorded under Recording Numbers 472354 and 5558464; TOGETHER WITH that portion of Tract 67, Riverside Interurban Tracts, according to the plat thereof recorded in Volume 10 of Plats, page 74, in King County, Washington, lying northeasterly of 42nd Avenue South as deeded to King County by deed recorded under Recording Number 5655246; EXCEPT the east 20 feet thereof deeded to King County. by deed recorded under Recording No. 1207877; AND EXCEPT the north 350.00 feet thereof; TOGETHER WITH that portion of Government Lot 3, Section 15, Township 23 North, Range 4 East, W.M., in King County, Washington, lying northeasterly of 42nd Avenue South as deeded to King County by deed recorded under Recording No. 5655246; EXCEPT County Roads; TOGETHER WITH that portion of Tract 19, Fostoria Garden Tracts, according to the plat thereof recorded in Volume 9 of Plats, page 95, in King County, Washington, lying southwesterly of F. J. Folkendahl Road (43rd Avenue South) as condemned in King County Superior Court Cause No. 241626. r 2 August 1992 HEBRANK AND ASSOCIATES File 92046 1 H 1N3WH3V11V rGi T" PAP. K. PLANT- LE-(=5ND t.e. a. .........r. . •••• ••••no 01, mt.. 1,,,.....' el........., e. ..11•••••••• : , , • • , •••••• •••• • •••• •`•••••• •••••••,..: . 4 ,7•=2.:7:Z:;i•----.----71-Z; ••• i i..:: 7::: ' i.:::::'A:.:.:•■••,:7,774,,• : .5 i •••••••••• • •■•••••■ . • •••••:«—is• ...:'' 1 .;-5-•,,,,,,,. -_,./...... t• ...... • . .......... . ••••.....”.....ilAn I. t l';•,'1* • s•11=1 .5 r-s. ..., •s tot . -,......... 'PT ....".,_, ..n....... A............••.• ....,« 1.11.-";:-.41- 4:14...."1"-::•.......7:77-"•17i"..s.-t2Li 4— - 0 -it. ................... • ic........ ,....... ---c,...- . • 14.tt,..-...■,=s3-44_ 2!"..1-t...2....nt: ..!--.1e.---iatt....!--nt.4? .--- . 0.t.ttr-:2..!--.--.--.--.--....---- — , ....7"..,.;4..•....„7,k•• 4 j t i r J •.. ia7_•7..--/.. .r..!' •••••':•_•_.:_.'t•J...t.'_ .•.-e..•:•• .__..__ ''•ro ..*••_.!F":;":7"-=r :74 a .11,---4:7 -: 1. r...4:7•••29....t=fr. - • ...V.::-..••• 1.•••• ' -•••1"-A• ' --"----.' .. 1 i1J-6=:, • .."-;-•• • •••■• • ••••••• •■ .. - - • - . 1-- ' • . • IRE J.- BC-L-7.N t•-. 1ST, 1,7: 4 ; 1111 11/ /7 —:.:-.:n,-..:.. .auiricoutwataw,,..„. =Tr 4 DlA45.0 CONTT rei MOM • to•NLAT iS Nor To 1 of. •m.ms, ••••. et wru•••55 110•••..e.•T M tortrau..., o 'Amt to sAsuawca o• LANDSCAPING PLAN P.R.0,1 PRELIMINARY PLAT / SUBDIVISION FOSTERVIEW ESTATES OUJAROIN 21 DEVELOPMENT COMPANY •72.-74 7011 PPECIII5 NAY: 4 • 4,544. a • at ts.A.. Co■ • CmI/IVI C.', • aarro•asaco 077.Cy*0t50 P.• M • P • ra•a. w • •••.-0.• ■•• • At•,• "'flee C-0■010PY PAT A ow. on VII. •■■•■ •10.••• SIP ..•••••.1 f.•=0 11.2_ff■ • tura. •••• 11• IIINMOV • ir %ft) ,• p •A 4••,.• 0000 '0 f•s•e•• 11.111 5•• f••■•••,. 108 M■la AP mu mum-, •em, MI 47.14. . M.o.. • ••••••:.: =7 I CI! ; (J0 v04 AcornoNAL -MEG iciTALv. 1 el LANDSCAPE PLAN • i'• SO. •.:1F;LZ;1%.::;:•?Vor:VerotArg:2;•4. ?:!:; 1.13/5 " JERALD K. BELL 2127 NORTH 148TH STREET • • Landscape Architect SEATTLE, WASHINGTON 98133 PHONE 362.9137 WETLANDS BUFFER ENHANCEMENT. PLAN for Fosterview Estates, Tukwila; Washington A. 1. Areas of Buffer Enhancement are shown on•the Landscape Plan and include three small areas where proposed grading will encroach-on the edge of the Wetlands Buffer area. 2. Additional Wetlands and Buffer Enhancement will be required to mitigate encroachment of the roadway for S. 137th Street, where it crosses the Wetlands and Buffers. The City has indicated that sizes and locations of this Enhancement are to be determined at a later date when additional information and details are available. B. Enhancement Plantings: 1. Trees to be planted are Thuja Plicata (Western Red Cedar) 6' -7' size•, planted 12 feet apart. These trees are the same species as the Cedars which are now growing on other parts of the site. They will eventually grow 60 to 70 ft. tall and spread 20 to 25 ft. They are a native species and after a year of care, when they will be properly established, they will fend for themselves and will eventually become a part of the tree canopy. 2. Shrubs to be planted are Cornus Stolonifera (Red -osier Dogwood) 2 -gal. size, planted 5 ft. apart. This is a medium sized native dogwood shrub which will eventually grow together into a dense stand about 8 to 10 ft. tall. It is a deciduous species with prominent red branches and twigs,and is an ideal habitat for native birds. This species grows wild throughout the Pacific Northwest and, after proper care for a year, will not require any further attention. 3. At the time of planting, trees and shrubs will be planted with good quality organic soil and slow release fertilizer to help get them properly established. Trees will be staked to keep them firmly held in place until they are established. C. Plant Maintenance: The Enhancement Plantings will be watered, fertilized and otherwise cared for, as necessary to keep them healthy and vigorously growing through their establishment period of one year. D. Guarantee: During the first year, or one full growing season, any plants which die or fail to become established and are not vigorously growing will be removed and replaced with the same size and species as originally planted. AUG 17 '93 22:57 C MORGAN ASSOC 509 P02 rocs paraz.1 Pea 4 33, 62 4. 4 I . (o 0,.c.)/es PsYeA k r C CP Ci+xf 12, ci -4 3 vie( ( 30 act/es P. C avcQ..l. fWea C7'os5 P fc¢.Q fSrea. i ce t2 t (t ite& 433, (044 $5-6 - S ., x(43 scref ,. 4Zo, -df (q. (i,to aseYes R,aw. w ek 4 vca..l krea - 1, 670-7 51 (I IGa.cvcs "% 12• o. w, w tWr 4i fJ k4 Pet.v z( Area 6.12 2.% `Th fa, 5 , - 13(A Pfey pre.' a r + 4L+ (A.) (fit, Y7 P.e - ' I 0 , 3e5 = 2'51 cccre5 -ft--16W4____ ill 'f Pour& Pre Puii tekalcile Pt�ves (C -- 5 3 O 4 ci- U/Acie ( 1 fi.,404o - 4.3,5coo C. 12-) -zoo (Dv/Actz)(euti...0A-6-E- Ac.42) + C P u /cap ='( -1- Bum) C ,a trah r -7 , r 5) 4 (5 3Z) (2.'3' ( 2.4-) - 4V.2_5 • 41.23 lofs + 3,21 -x Tie a-Aveo,. & e/ ltp c f2,Q, w, u-tr t au r va. 4 , i `Th - ' wre.. i t.s rt o eXA1 s i de li a bare eacctAa v�"7-‘o mmdi SA Exc ,rrp Due eor 37/ Lo• 21 9 L =v: t7'S ea)) — r Cm/At/ft 2A Q c j fl %- un� /7....___--.DeAAv\A — -j 1 AAA. ice ../z(A Cot sA4 , PU.m._Q_ GI- .;c0t.4 `T"h.v' L'' wlrka. - U DENSITY CALCULATIONS BUILDABLE . RES -- SENSITIVE AREAS & SUFFER5 6 y 1 100,373 sq.lt. */ -)e€, J - — 2.30 ACRES +7.a5ACRES 92 (C)cclu�� ca c L NET DU /ACRE • (431580 — (43,560 (.15)) / 7200 IN 5,14 /-(2- (0U/ACRE) (BUILDABLE ACRES) + (DU /ACRE) (SA + BBBUFFERS) (x(•2TR4A)NSI�6R) I.OrI� (5.14) (7.65) + (5.14) (2.30) 109,3 73 54 »' i Q- 7f 3 32 2 /43 64/234- -_8,7741( s-heekat /s),„z 6o,0 (� J 3S z,'8 g/ Cg' 5) (e.e) ZOO S60 'ON ( 2, _3 24) A1IO 1 71993 ; DEVELOPMENT ENT G992 T2P 90E - NOC O9 '8 mom OP :21 26/LT/80 :S -- (11%) 1 FOR LOTS 1 -3 — (2%) -- (31%) X) 1 GROSS LOT AREA: 433,644 sq.ft. (9.95 ACRES) NET LOT SZE: 420,701 sq.ft. = 9.66 ACRES -- EXCLUDING AREA TO BE DEDICATED TO CITY OF TUKWItA : 12,943 sq.ft. 9.66 ACRES DMDED INTO 41 LOTS TRACT "A" & "8'" : 103,572 sq.ft. (2.38 ACRES) SMALLEST LOT IS LOT #28 — 3,949 sq.ft, AVERAGE LOT SIZE = 6,452 sq.ft. MEDIAN SIZE LOT = 5,870 sq.ft. ?EVELOPMENT STATES ENT COMPANY EVERETT PHONE: 334 -5018 SEATTLE PHONE 743-6140 CHARLES MORGAN & ASSOCIATES IA'T�S RCHITECTS �1 mown, WASHINGTON 111203 TELEPHONE 2OS- 363..E �n cn 1301 BEVERLY' LANE RCH uq cT. t=j LU 6 46,193 sq.ft. — FOOTPRINT OF ALL HOUSES -- (11%) 23,255 sq.ft. — DRIVEWAYS — (6%) 7,668 sq.ft. — DRIVEWAY & HAMMERHEAD FOR LOTS 1 -3 — (2%) 40,500 sq.ft. — STREETS — (10%) 10,260 sq.ft. — SIDWALKS — (2%) 127,876 sq.ft. -- TOTAL IMPERVIOUS SURFACE — (31X) 0 103,572 sq.ft. — TOTAL TRACT AREA — (25%) S1TE PLAN M a) w N 1" =30' PLANNED RESIDENTIAL DEVELOPMENT FOSTERVIEW ESTATES DUJARDIN :: DEVELOPMENT COMPANY AN ALLEGRE ENTERPRISE EVEREiT PHONE: 334-5018 SEATTLE PHONE: 743 —6140 Gl GROSS LOT AREA: 433,644 sq.ft. (9.1 NET LOT SIZE: 420,701 sq.ft. = 9.56 DEDICATED TO CITY OF TUKWILA : 12,12 9.66 ACRES DIVIDED INTO 41 LOTS N TRACT "A" & ' B"' : 103,572 sq.ft. (2 8 SMALLEST LOT IS LOT #28 = 3,949 AVERAGE LOT SIZE = 6,452 sq.ft. MEDIAN SIZE LOT = 5,870 sq.ft. CHARLES 7301 BEVERLY LIME F m 0 G00 RUG 16 '93 02:28 G60 '0N C MORGAN ASSOC X02 I'M , GUARD RAIL- ,�J/ MEAN DEPTH 'w 122 -0" 1589-0" 159' --2" 148' --4" 142• -6" 143' -0" 147'-9" 128' --2" 110' -10" 168�^ N ' -d' 13V-5" 1081' -1" 199'w� r e, 131'-.O" 18V-1" 179'- -8" 117' -2" 1666' -8" 90-4 80 6" 88' --9" 112' " 134' -9" 127'-11" 123' -7" 125' 10• 132' --1" 123' -8" 146' 1d' 112' -1" 100' --4N 98' --4" 101' -2" 104' -4" 391'-.1 0" 281' -7" LOT 11 ADDR.SS _ LOT AREA MEAN YYIDTN ,_ ft. 122'�-C'" 1 138022 - 2 13806 - 3 13514 4 4302 -' S. 5 4306 - 6 4310 -- 7 4314- 5 4318 -- 9 4323 - 104320-- 11 4330 - 12 4334 -- 13 4336 - S. 144342 -" 15 4344 - " 16 4343 " 1.7 4341 -- 18 4339 " 19 4337 - 204335 -^N 21 4333 - 22 13818 - 23 13812 - 24 13806 - 25 13801 - 26 13807 - 27 13815 - 28 13821 - 29 13827 -- 30 13833 - 31 13839 -- 32 13710 - 33 13716 - " 34 13722 - " 35 13728 -- 36 4349 - S. 137th ST. 37 4353 - 384357 -" " " 39 4361 - 40 4385 --- " 41 4369 - TRACT "A" TRACT "O' w N N 4 ;nd AVE ;. 105,4600 sq. 1g: VS g" N N » 8,747 55' -0" 137th ST. 5,02 7588 1 5,870 w " 5,051 5,040 • " 5,579 " • 8,720 OP 8,252 le • 5,318 137th PL. 4,950 ,530 • 117,652 " ▪ 5,546 N • 5,010 • • 7,241 • 11 ,807 • 8,574 • " 6,181 43rd AVE S. 7,446 5,421 " 4,984 /9 4,85/7 ✓ " N ,525 le it 4 " '4,293 " 3,949 re 5,986 " 8,191 N N " 7,742 42nd AVE S. 7,119 6,109 " 6,270 • • 8,840 7,464 5,705 4,634 • me 4,586 " 4,886 w • 4,772 75, 27,958 813 1- U Y DEVELOPMENT 55'- -? 48' --11" 38' 35,-3" 37'_10" 57' 1" 54' -8" 7X-1" 70' -d' 45' -3" -4'" 48 ,r '+ N 5g' --Q" 41'-0" 64'-2" 48'- 10" 54,-- 53' -10" 52' -g" 47'-1" 48' 52 � ' -5" 539-4" 60'-S" 47, -9" 47'-4 54'" -11" 47' --3• 49' --4" 451-4" ,-7 " 47'" 1�a,_� N G992 T217 902 E- NOG800 > one Sb:2T AUG 04 '93 22:40 C MORGAN ASSOC tree canopy gross lot area impervious surface calculations • • -:.: `: .. 902 WATERFRONT PLACE • 1011 WESTERN AVENUE SEATTLE, WASHINGTON 98104-1097 (206) 382 -9540 • FACSIMILE (206) 626-0675 ATTORNEYS AT LAW PETER L. BUCK BRENT CARSON JAY P. DERR JOEL M. GORDON SHELLEY E. KNEIP AMY L. KOSTERLITZ KEITH E. MOXON July 27, 1993 OF COUNSEL ALISON D. BIRMINGHAM MADELEINE A.F. BRENNER PROJECT MANAGER KATHRYN A. GARDOW, P.E. RECEI JUL 283 Ms. Denni Shefrin COMMUNITY City of Tukwila DEVELOPMENT Department of Community Development 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 Re: Fosterview Estates PRD and Plat; Conditions, Covenants and Restrictions Information Dear Denni: You have asked for information about the Conditions, Covenants and Restrictions (CC & R's) that will be adopted for Fosterview Estates, in accordance with your PRD ordinance, Section 18.46.110 (4) of the Tukwila Municipal code. That section requires submittal of "basic content of any restrictive covenants." We construe this to require, at this time, a basic outline of what the CC & R's will cover, rather than specific language provisions addressing all of the details. We believe our interpretation of what is required in terms of "basic content" is correct because your PRD ordinance later requires, in Section 18.46.115, that the specific content of the restrictive covenants intended to be used in a PRD be approved by the City Council and the City Attorney before issuance of a building permit. Your process thus contemplates that the detailed provisions of the CC & R's would be reviewed and approved not prior to PRD approval, but prior to building permit issuance. In this case, where a subdivision is involved, the logical time for City Attorney and City Council review of detailed CC & R provisions would be at the time of the City Council's approval of the final plat. The approach of giving basic information at this time will allow you to make it a condition of final plat approval and /or of building permit issuance, that detailed CC & R's, covering certain basic areas, be drafted and approved by the City Attorney and City Council. In addition, as your PRD ordinance recognizes, detailed drafting of the CC & R's at this stage is not possible because we still do not have approval of our design through the PRD and preliminary plat. -2 July 27, 1993 Accordingly, the basic content of CC & R's for the development will include: (1) A definition of common areas or sensitive area tracts and how these are to be utilized, maintained or preserved; (2) The creation of a Homeowner's Association to which the common areas or sensitive area tracts will be conveyed, with responsibilities and restrictions on how these areas will be utilized, maintained or preserved (3) Rights retained by the Declarant regarding administration of the property, with transition provisions to the Association (4) Restrictions on use of the property for residential purposes, with design restrictions regarding fences, landscaping, signs, keeping of animals, disposal of trash, quality of exterior finish of buildings, etc., in order that the development present a uniform and aesthetically pleasing appearance, and the Association's responsibilities regarding enforcement of these restrictions, including the establishment of an Architectural Control Committee (5) Regulations for establishment of the Association and conduct of its business, including voting rights therein, bylaws, meetings, etc. (6) Provisions for monetary assessments by the Association to fulfill its duties of maintenance of common areas and its other responsibilities (7) Provisions to make these requirements covenants running with the land and dealing with enforceability We hope that this is satisfactory. Please give me a call if you have any questions. Very truly yours, Amy L. K terlitz cc: Bill Fowler DgfardinVA7273.alk • 46,193 sq.ft. — FOOTPRINT OF ALL HOUSES -- (11%) 23,255 sq.ft. — DRIVEWAYS — (6 %) 7,668 sq.ft. — DRIVEWAY & HAMMERHEAD FOR LOTS 1 -3 — (2%) 40,500 sq.ft. -- STREETS — (10%) 10,260 sq.ft. -- SIDWALKS -- (2 %) 127,876 sq.ft. — TOTAL IMPERVIOUS SURFACE — (31%) 103,572 sq.ft. — TOTAL TRACT AREA — (25 %) SITE PLAN 1" =30' GROSS LOT AREA: 433,644 sq.ft. I LOT SIZE: 420,701 sq.ft. = 9.66 AREA TO BE DEDICATED TO CITY 0 9.66 ACRES DIVIDED INTO 41 ACRE TRACT "A" & "B" : 103,572 sq.ft. SMALLEST LOT IS LOT #8 — 3,804 AVERAGE SIZE LOT: 5,897 sq.ft. MEDIAN SIZE LOT: 5,546 sq.ft. PLANNED RESIDENTIAL DEVELOPMENT FOSTERVIEW ESTATES DUJARDIN :: DEVELOPMENT COMPANY AN ALL£GRE ENTERPRISE EVERE I PHONE 334-018 SEATTLE PHONE: 743 -6140 CHARLES 7301 BEVERLY LANE JUL 27 '93 01:31 • C MORGAN ASSOC . • LOT.# ADDRESS 1 13602- 42nd AVE 2 13608 -- 3 13814 4 4302 5 4306 6 4310 7 4314 8 4318 9 4323 10 4326 11 4330 12 4334 13 4336 14 4342 15 4344 16 4343 17 4341 18 4339 19 4337 20 4335 21 4333 - 22 13818 23 13812 24 13806 25 13801 LOT AREA S. 9,218 sq.ft. 5,726 11 0 7,228 4,917 5,689 4,297 3,814 3,804 3,983 4,843 6,224 5,048 137th PL. 4,950 5,733 6,407 5,546 5,010 7,241 • 11,807 • 8,574 " • 6,161 7,446 5,421 4,984 4,657 4,525 4,293 3,949 5,966 8,191 7,742 7,119 6,109. " " 6,270 " " 6,840 137th ST. 7,464, 5,705' 4,634 4,566 ' 4,886 4,772 75,959 27,613 1S. 137th w " 11 11 11 w „ 0 S. w 11 1► 11 �. 11 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 13807 13815 13821 13827 13833 13839 13710 13716 13722 13728 - 4349 - �S. 4353 -- " 4357 - 4361 " 4365 - " Pt ST. 11 1, 1, 11 1, w w 43rd AVE S. O 0 42nd AVE S. 41 4369 - TRACT "A" TRACT " B" " 11 " 11 n 11 1, " 0 MEAN `1NIDTH: '' N, DEPTH 84'58!-O". 84' -3" 11" 58' -7"` i:;• . 87.' --8' 38'- 4 7T•:.'••112•--10": 105' --9" 12' --8" 73'' 1': =:u 68' -8" 11175" x`..87' --11 ". 51'� -11" ..102-' -5" 53.-4"V4- 13V"...0" ' 58' -9" 77'-. 1w 64'742" : • 92' -9" 117' -2" 48' -10" 66' -6" 54' -8" ; l�.. 90' -4" 47- 1 <-:s,L 48`x- 7".I..if ,..112., -1" • .`.134. ,'• -9" 531,, 4" � '-"127c;;-11" 5;,123"x, 7': 10 " • . 54'• 11 "s'r ": `•123"x-6"•' 1407;107.: • ::1121.1" 100' -4" 46' -5" 471-7" 46' -9" :•.:104.4" 154'- 11 7; ::` 391;?'rs` 1 O" 98'771:. ` 261• ` • 7'.': :60.1r.'6" `88' -9" • 98'_4" 1011frr2" (2 %) w CC z Q 0 Ui =NT cn Q1 ANY J . ti S4 -5018 3 -8140 GROSS LOT AREA: 433,644 sq.ft. (9.95 ...ACRES) . - LOT SIZE: 420,701 sq.ft. = 9.66 ACRES (WITHOUT AREA TO BE DEICATED) AREA TO BE DEDICATED TO CITY OF TUKWILA : 12,943 sq.ft. 9.66 ACRES DNIDED INTO 41 ACRES 4 BOXES - MAILBO U • (TYP) TRACT "A" & "B" : 103,572 sq.ft. (2.38 ACRES) = 25% SMALLEST LOT IS LOT #8 — 3,804 sq.ft. AVERAGE SIZE LOT: 5,897 sq.ft. MEDIAN SIZE LOT: 5,546 sq.ft. CHARLES MORGAN & ASSOCIATES • 7301 BEVERLY LANE RCHITECTS EVERETT, WASHINGTON 98203 TELEPHONE 206 - 353 -2888 IXI: ORB CITY OF TUKWILA 6200 Southcenter Boulevard, Tukwila, Washington 98188 FROM: DATE. MEMORANDUM cart n c; ciry rL _ / / 2,5 SUBJECT. 1 4,/-05"/o/7. 0,0 L. / .) / 2,1-r 7) (-7r o Ivn (O /2 , / (206) 433-1800 • 64_n "n4i CU. A?- S2 1,40 ) 5 , ZA X.Q] ccie4, 72 Au4A density calculation fosterview CODE INTERPRETED: Zoning Code CODE INTERPRETATION FORM SECTION NO. PRD Density standards 18.46.070(D) Date Interpretation Made: 27 August 1991 Interpretation: 1. Housing density = Dwelling Units' (DU) /Acre = units per acre after subtraction of street easement or right -of -way; and 2. Buildable area = parcel area - sensitive area and buffer. Why was this interpretation developed? Confusion as to. how to calculate number of units allowed in a PRD in sensitive areas. What is the justification of the interpretation? 1. 18.46.060 Relationship of this chapter to other sections, says that the number of dwelling units per net (emphasis added) acre permitted in the underlying zone, shall serve•as the criteria to determine PRD density. 18.06.440 Lot area, "means the total horizontal area within the boundary lines of a lot and exclusive of street right -of -way or street easement." Therefore road area is subtracted for the purpose determining Aet density. 2. Absent an adopted definition of buildable acres a literal interpretation is taken of "buildable acre." For example: A 10 acre parcel, 15% assumption for road area (actual right -of -way would be used on projects) , and 2.6 acres in sensitive areas and buffers results in the following: Buildable acres = 10 - 2.6 = 7.4 acres Net DU /acre =(43,560 - (43560(.15)))/ 7200 = 5.14 (DU /Acre)(buildable acres) + (DU /Acre)(SA + Buffers)(% transfer) (5.14) (7.4) + (5.14) (2.6) (.24) = 41 (without sensitive areas the formula would yield 51 units) .Signature of Interpreter: Date: Approved By: Date: /2-577/ ATTACHMENT 1 'rte;• , L�.�i _ HAMMOND, COLLIER & WADE - LIVINGSTONE ASSOCIATES: "INC. CONSULTING ENGINEERS LARRY R. WADE. P.E. BRUCE LVINGSTONE. P.C. FREDERICK G. KERN. P E. HEROLD E. RAYNARD. P.E. JOMN 0. LEE. D.E. JOHN O. NENDRON. P.E. ROBERT E. BERGSTROM. P.E. DON PHELPS. P.E. OEANNE M. REYNOLDS, P E PROFESSIONAL SERVICES SINCE 1943 4010 STONE WAY NORTH SEATTLE, WASHINGTON 98103 -8090 TELEPHONE: (206) 632 -2664 1- 800 -S62 -7707 FAX (2061 632.0947 MEMORANDUM TO: Phil Fraser, City of Tukwila Ron Cameron, City of Tukwila FROM: Bob Bergstrom, HCW -L, Seattle SUBJECT: Foster View Subdivision Peer Review DATE: June 28, 1993 943a 3Z KENNEY,. 1.. EDINGTON, P.L.S. DALE 0. ERDAHL P.L.S. ROBERT G. GREENE. P.L.S. JUDY FREEBORN, ASLA TIM JONES. AIA We have prepared a list of general technical recommendations for the plat of Foster View Estates to be considered by the City of Tukwila. 1 have characterized these comments in two general classes: comments proposed for the SEPA process (E), and comments proposed for the later City PW technical review process (T). These items are listed below: 1 General Technical Recommendations A. Private driveways on properties on the downhill side of any road or street should have a trench or slotted drain installed across the entire driveway width. Currently the development has small area or catch basin drains spotted in front of the homes' garage doors. Qur experience in sev- eral communities has shown this to be inadequate, and the downhill homes have experienced flooding off on the driveways. A full width trench or slotted drain will provide the highest level of protection for the homeowner and keep the City out of future problems. (T) B. The street sections on the preliminary overall street plans show a considerable portion of the road curbing along S. 137th Street, S. 137th PI., and along 43rd PI. S. having rolled curbs. We suggest that vertical curbs be used exclusively on this project, with a minimum 2 -inch lip at the driveway section. that the sidewalk section be pitched to the gutter, and that no reverse slope driveway sections be allowed. This should be a basic requirement for drainage control, to keep street drainage out of private properties. (T) C. On several Tots, #1 through #3, #21, #25 through # 31, # 32 through #35, and #36 through # 41.. the yards are in cut sections with an uphill slope extending to either public streets or wetlands preserves. These yards may get considerable amounts of ground water seepage that make them nuisances and unusable for private use or yard plantings. With the large number of springs expected on this site, we recommend that the private yards for the Tots described have individual French drains installed transverse, across each lot, tied into.their individual storm sys- tem, which will collect any subsurface drainage flows. If these items are not controlled at the time of development, there is a high probability of later homeowner complaints against the City to control subsurface drainage from city streets and city mandated wefland'preserves. (E) 200•39dd 1-MOH WO d b0 :Zi tt'64 22 Had Memorandum June 28, 1993 Page Two D. Street Improvements along 42nd Ave. South should be fully constructed as part of the plat development. Since there is considerable sidehill earthwork along the plat frontage of 42nd Ave. South, and that positive drainage collection and interception of runoff from the upper street onto the new lower home sites is critical, this curb. gutter, and sidewalk work should be constructed now. Work should include extension of a formal storm system with catch basins at spacing no greater than 300 feet, and at the new street entrance to So. 137th Street. (E) ' E. All catch basins on the project, including The drains along 42nd Ave. 5. should be the through curb inlet frame (see King County Standard DWG. #44) and utilize the vaned grate configura- tion (see King County Standard DWG # 46). (T) F. All storm drain pipe lines shall have full gasketed pipes, equivalent to ASTM C 118 heavy duty concrete drainage pipe, or ASTM -D 3034 PVC Sanitary sewer pipe and gasket standards. This pipe criteria should be combined with the highest level of workmanship on catch basins of all types, for plastic pipe, utilizing gasketed catch basin connection collars grouted into the CB's using GPK manhole adapters or equal. All concrete catch basins and drainage structures should have mastic sealant or gasketed sections, and all joints, riser sections, and adjustment bricks should be parged with an APWA portland cement mortar on the interior and exterior. The new storm system should be pressure tested to insure a minimum of leakage from poor installation practices. (T) G. All driveways should be paved. The item of special concern is the joint driveway serving Tots # 1, # 2, and # 3, which is shown as about half paved, and no drainage controls along the wall or rockery edge to the north. This driveway should be should be fully installed as part of the plat improvements, and constructed with a full width paved surface. together with a curb and drainage system to collect surface drainage off the roadway surface. (E) H. Unanticipated spring interception will probably be required during the project roadway and site earthwork excavation. There are numerous, and yet unidentified, springs throughout the project site, which must be collected and directed to the new storm system. There should be a detail for this proposed work on the project plans, showing in advance the proposed collection system of sub drains, the method of backflling, and provision of monitoring wells for long -term observation. If large springs are encountered under future building sites, this may preclude construction of homes in the precise location shown on the preliminary development plans. (E) &(T) The development should strictly follow the geotechnical recommendations of the Terra Associ- ates and Applied Geotechnology Inc. firms, as provided in their numerous letters and technical memorandums. We have listed several of the items we believe are of special concern; how- ever, we have not attempted to list all of the recommendations, nor through omission imply that other items should be ignored or carry less weight. (E) 600'30Hd 1—MOH WOdd S0 :41 P6s 32 E3d Memorandum June 28, 1993 Page Three L (continued) Applied Geotech. Recommendations: 1. "The developer should prepare for review by Terra and the City detailed cross sections in all planned fill areas indicating how the fill will be keyed, benched, and drained as recommended in the geotech report. A typical detail should be prepared illustrating the geotech engineer's recommended key at the toe of all proposed fills on slopes. Calculations supporting adequate safety factors against slope instability should be provided for review by the City." 2. "We suggest the developer, in conjunction with the geotech engineer, prepare detailed design cross- section addressing subdrainage provisions for fills placed on slopes and underlain by lacustrine deposits." 3. "We suggest Terra be requested to review the foundation details and comment on the need for connecting individual footings or supporting the houses on post - tensioned slabs as a possible means of reducing potential for differential settlement of the struc- tures:' 4. Construction monitoring by the geotech is recommended; with written conformation of work performed in accordance with the geotechnical recommendations. (This is a condensed version of the AGT language. Please refer to the full text In the original 5/17/93 letter report) J. It is HCW -L's recommendation that the proposed cuts and rockery work along the existing roadway right -of -way for 42nd Ave. So. (behind lots # 1, 2, and #3 also be examined by the geotechnicol engineer to insure lateral stabTty of the existing roadway together with the new rood improvements. (E) In addition we have addressed the issues directed to us by City Staff for specific examination. Our rec- ommendations are presented below. 11. Does development increase runoff on to property to the north? Yes, the Project's proposed dispersal trench on the South Gate Park property for drainage discharge to the north is sized to limit runoff rates to less than a 25 -year, 24-hour storm. However, storm events with a retum frequency Less than 25 years may discharge at a rate higher than their predeveloped rate. Therefore some increase in storm discharge rates is proposed in the current project configuration. We believe that this could cause an undesirable impact upon the downstream properties. It may enlarge the existing wetland's perceived area. b00'39ed 1-M3H W08J S0 :4I 176, 22 Had • Memorandum June 28, 1993 Page Four We recommend that if the City of Tukwila wishes to implement the proposed dispersal trench .tech - pique, the King County SWDM Manual (Nov. 1992) Core Requirements should be specifically refer- enced: Core Requirement #1 Discharge at the Natural Location (3) Dispersal trench max. rate of discharge shall be 0.5 cfs for a 100 -year, 24-hour storm. Core Requirement # 3 Runoff Control Peak Rate Runoff Control Performance Curve: Show that the release rates will not increase for the 2 -, 10-, and 100 -year, 24-hour design storms. An entirely different approach which we recommend be considered would direct all from the drain- age from the new closed pipe system directly to the proposed storm drainage system improvements in 44th Ave. S. and avoid any future drainage liabilities from overland discharges. We believe this is a superior drainage management approach for this project. (E) • IIIA. Propose Sequencing and Phasing for the Project Construction to Control Clearing and Erosion Potential Problems. The project should be constructed in phases, with the initial phase limited tothe north margin of the new S. 137th Street. and a new temporary storm line routed from the S. 137th Street storm system to the discharge point along the north end of 44th Ave. S. beyond the slide area. This could be aligned either from the new, large detention tanks in the intersection of S. 137th PI. •and S. 137th Street and then easterly to the new storm system'along 44th. Ave. S. or directly north along the S. 137th St. cuI de sac to the connection to the existing storm culvert on 44th Ave. So. The preservation of a buffer of 100 feet in width along the north property line, during the initial phase of construction will preclude construction of any site grading or utilities for lots # 1 through # 21, until the upper portions of the project are fully graded, all utilities installed, and all streets south of S. 137th Street are paved. Construction work north of S. 137th Street must be carefully planned and implemented to control erosion and siltation generation from earthwork and utility construction. We recommend that the road fill along the north side of S. 137th Street be confined as tightly as possi- ble to the road alignment by the use of a geotextile or geogrid reinforced roadway embankment to limit the road fill extension into the downhill, temporary erosion and siltation control natural buffer area until later phases of construction are implemented. In addition to phasing construction of the public utilities and street improvements, building site grading, retaining structure, and foundations must be property sequenced. .constructed, and monitored. As emphasized by the Applied Geotechnology Inc. technical review, there is a considerable potential for slope stability problems to occur both during and'atter construction. We have provided our recommended construction phasing in the following Section IIIB that includes both utility and street construction, together with site work and house construction. S00 ' 39dd 1-MOH WOZId 90 : L T P61 22 Had Memorandum June 28, 1993 Page Five MB. What Erosion Control Measures are Recommended Considering the Closeness of the Natural Streams, and the River, Erosion Prone Slopes and the Slide History of the Area. We recommend that the City of Tukwila implement the King County SWDM Manual Chapter 5, Erosion /Sedimentation Control Plan and Practices requirements, specifically emphasizing: • Preparation of a erosion and sedimentation control plan. • Site Stabilization via stabilization of the construction entrance and construction road. • Slope pipe drains. • Subsurface drains. • interceptor dikes or berms directing runoff to a stabilized outlet. • Protection of existing drain ways by the use of check dams, structural stream bank stabilization and sediment trapping. • Storm drain inlet protection and filter fabric fencing. • Cover measures including seeding, netting and matting, and plastic covering (T) It is our recommendation that the Foster View Estates project avoid TESCP techniques that encourage infiltration or ponding without heavy bottom liners, because of the high potential for land sliding. We recommend that the project be phased, with only very limited construction disturbance in any area at one time. The following is provided as a guideline to implement the land altering ordinance. The City should require a phasing and sequencing plan /diagram for the total project construction. This should be submitted for City review and approval prior to construction start: A. Construct S. 137th Street and in- street utilities, with temporary storm ouffall and temporary sani- tary sewer to avoid construction in 100 feet* wide northerly buffer., (E) B. Proceed with construction in the three areas of the site uphill and 'southerly of the S. 137th Street corridor. Lots # 36 through # 41, and Lots # 32 through # 35, and after these two areas are constructed and stabilized, allow construction on the section of lots # 22 through # 31. (E) C. After construction of the uphill areas and stabilization and paving is complete, then the two sections of the development below and northerly of S. 1 37th St. can begin for Lots #1 through #21. (E) D. limit individual home construction by phasing so only a limited number of sites are in a dis- turbed state (all site work, drainage, and landscaping [sodded or established grass] is completed) at one time. We suggest that a limit of 3 home sites be allowed to be under construction at one time, in each area defined in Section B & C above. (E) IV. The Proposed Swale Along the North Side of the Property is an item of Concern. Can it be Relo- cated Into the Wetlands Buffer N.E. of S. 137th Street and S. 137th PI.? We do not recommend relocation of a bioswale into the easterly, slide -prone areas of the site. While it may be technically possible for a bioswale to be constructed in this area, we have very strong con- cerns for the long -term stability of the existing hillside, and we recommend keeping off this slope. 900 . 3Jtid 1-MOH W0213 90 : L l t76. 23 H33 ** 400 ' 39ed 11i101 ** Memorandum June 28, 1993 Page Six We also believe that It will very difficult to sustain any bioswale grass growth in an artificially con- structed channel in the wetlands buffer, the north properly line location, and along the abandoned 44th Avenue South right -of -way, because of the poor sunlight exposure, high natural trees, and the proposed high walls on the southern exposure. We believe that the proposed bioswales will have performances that are unacceptable for long -term water quality protection, and that other techniques such as wet vaults are more appropriate for this project. • If bioswale methodology is mandated for this project, we recommend that the bioswales be relocated off site to the So. 133rd Street right -of -way, where more favorable condiflons exist for sustaining plant growth and assuring proper maintenance. (E) \worIdng\berosbmVnemo0628,doc Applied Geotechnology Inc. May 17, 1993 15,735.001 Ms. Denni Shefrin Associate Planner City of Tukwila Department of Community Development 6300 Southcenter Boulevard, Suite 100 Tukwila, Washington 98188 Dear Denni: Geotechnical Review Proposed Fosterview Estates Development Tukwila, Washington This letter presents the results of Applied Geotechnology Inc.'s (AGI) geotechnical review of the above - referenced proposed single - family residen- tial development. Our services were performed in accordance with our April 29, 1993 proposal. We received your written authorization to proceed on May 4, 1993. .PURPOSE AND SCOPE OF. SERVICES The purpose of our services was to comment on the geotechnical aspects of the proposed development based on review of relevant technical reports, development plans, and correspondence provided by the City of Tukwila (City). Our scope included the following specific items: ► Item 1: Review the geotechnical reports by Terra & Associates and subsequent correspondence. ► Item 2: Visit the site to observe existing conditions. ► Item 3: Review the City's Sensitive Areas Ordinance (SAO) and the development proposal documents and provide our opinion on the following: - Determine whether the SAO requirements have been fully addressed. - Identify concerns, if any, which should be considered. - Judge the reports' adequacy relative to the proposed development. - Identify the need for additional technical study. ► Item 4: Comment on geotechnical aspects related to planned lot density, proposed biofiltration swale locations, and potential for increased runoff onto adjacent properties to the north of the site. ► Item 5: Provide our opinions and suggestions in a letter. P.O. Box 3885 Bellevue, WA 98009 FAX 206/646-9523 Telephone 206/453.8383 :;T1' Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 2 Applied Geotechnology Inc. The City provided geotechnical reports, correspondence, SAO, and development plans for our review. A specific list of documents provided is attached. UNDERSTANDING OF SITE CONDITIONS (SCOPE ITEMS 1 AND 2) Although we briefly reviewed all the referenced documents, we focused on the geotechnical reports and grading plans. The following paragraphs briefly summarize our understanding of existing site conditions and the proposed development based on our document review and May 7, 1993 site reconnaissance. The approximately 10 -acre undeveloped site is situated between 44th Avenue South and 42nd Avenue South. It is bounded to the north and south by Southgate Park and existing single - family residential lots. The intersection of existing South 137th Street and 44th Avenue South is approximately opposite the middle of the east property line. The portion of 44th Avenue South from opposite the northeast property corner to the intersection with South 137th Street is barricaded (abandoned) because of previous downslope landsliding of the existing roadway. The proposed development includes extending South 137th Street from the intersection with 44th Avenue South west across the site to connect with 42nd Avenue South. A total of 21 single - family residential lots (Lots 1 through 21) and a cul -de -sac (South 137th Place) are planned for the north side of South 137th Street. Another 14 single - family residential lots (Lots 22 through 35) and a small north -south residential street (43rd Place South) are planned for the west portion of the site on the south side of South 137th Street. There will be six lots (Lots 36 through 41) situated immediately south of South 137th Street on the east side of the site. These lots are bounded to the west and south by designated wetland areas (Tract A). Another wetland area (Tract B) is situated on the north side of South 137th Street opposite Lots 36 through 41. We understand the average lot size is about 5,500 square feet. Site topography is variable. For the purposes of this review, we have characterized the site and adjacent 44th Avenue South into the following general areas:'i ► Area 1 - North and Northeast Slope: This area comprises the property north of South 137th Street'except for Tract B, and slopes moderately to steeply downward to the north and northeast. Lots 1 through 21 are within this area. Existing slopes range between about 15 and 65 percent, but are typically between about 25 and 35 percent except for a relatively flat portion near the planned intersection of South 137th Street and South 137th Place. Proposed regrading in this area includes cuts and fills and use of retaining walls to establish roadway and lot grades. Fills along the north side of South 137th Street appear to range between about 4 and 12 feet. Cuts and fills up.to about 6 feet are planned for the South 137th Place cul -de -sac and associated. lots. Final slopes in regraded areas appear to be 40 percent (2.5:1) or flatter. Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 3 Applied Geotechnology Ina • Area 2 - Wetland Tracts A and B: Consists of the wetland area south of Lots 36 through 41 and a Swale that extends north from the south property line to the planned location of South 137th Street, turns east, and drains to a culvert which extends under 44th Avenue South. No regrading is planned for these areas; however, retaining walls are planned along portions of the wetland boundaries in order to establish planned grades in adjacent areas. • Area 3 - South Slope: This area consists of the moderately to steeply north to northeast sloping area where Lots 36 through 41 will be situated. Existing slopes are typically between about 20 to 35 percent. This area is to be terraced using balanced cuts and fills up to 10 to 12 feet and retaining walls in order to reduce topographic relief across the proposed lots and roadway. Regraded areas will be sloped at about 40 percent or flatter. • Area 4 - •West Slope: This area comprises the gently to moderately northeast sloping portion of the site west of Tract A and south of South 137th Street (Lots 22 through 35). Existing slopes in this area are generally between about 15 and 25 percent. Cuts of up to about 12 to 14 feet and fills of up to about 8 feet are planned. Regraded areas will have slopes of 40 percent or flatter. • Area 5 - Abandoned portion of 44th Avenue: This area is situated along the east property line of the site and consists of an existing roadway constructed along the west side of a narrow, steeply sloping ravine that drains to the north. The ravine sides typically slope between about 55 and 65 percent. Evidence of previous landslide movement includes tension cracks and vertical displacement of the existing asphalt pave -I ment north of South 137th Street for about 300 feet. The Terra reports include site reconnaissance, subsurface exploration and slope stability evaluations regarding the existing landslide on 44th Avenue South, and stability issues associated with the planned site development as required by the SAO for Class 3 landslide hazard areas. Recommendations are provided for foundations, basement walls, temporary and permanent slopes, site drainage,•and earthwork. The test pit logs included in the Terra reports indicate the majority of the West Slope (Area 4) and the cul -de -sac (South 137th Place) appear to be underlain by dense to very dense glacial deposits comprising a mixture of silt, sand, and gravel which they interpret to be Till. The upper portion of the Till is typically less dense and weathered. One of the test pits (Test Pit 16) apparently encountered glacially consolidated lacustrine silt and clay underlying the Till, at a depth of about 7 feet. Till was absent in most of the test pits north of South 137th Street (Area 1) and on the northeast slope downhill from the cul -de -sac. These pits typi- cally encountered the lacustrine deposits beneath the topsoil. The upper portion of the lacustrine deposits in this area is typically light brown to tan in color and becomes blue gray at depth. Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 4 Applied Geotechnology Inc. Lacustrine deposits were encountered in all test pits along the abandoned portion of 44th Avenue South and were overlain by several feet of silty sand fill used to construct the road. The upper portion of the lacustrine /-. deposits is noted as being blocky and disturbed as a result of landslide movement, which Terra attributes to improper construction of the road. SENSITIVE AREAS ORDINANCE REQUIREMENTS (SCOPE ITEM 3) Based on our review of the City's SAO and our understanding of site subsur- face conditions, we present the following opinions regarding Areas of Potential Geologic Instability as defined in the SAO: ► The majority of Area 4 underlain by Till appears to meet the criteria for Class 2 landslide hazard areas. ► The majority of Areas 1 and 3, the northern one -third (approximately) one third of Area 5, and the more steeply sloping portions of Area 2 should be considered Class 3 landslide hazard areas. ► The southern two - thirds (approximately) of Area 5 is by definition Class 4 because of previous landslide activity. Based on their stability evaluations, Terra concluded that the site slopes in their present condition appeared to be generally stable. The Terra reports did not indicate that detailed slope stability analyses were performed in formulating their conclusions; however, such analyses are not mandatory under the SAO for Class 3 areas. We conclude that the Terra reports in general appear to have addressed the requirements of the SAO; however, we judge that these slopes have a high potential for landslides because of the extensive site grading planned for the proposed development. We believe this opinion is supported by the instability of 44th Avenue South adjacent to the site. Accordingly, we judge that more detailed stability analyses and design details should be provided to the City to demonstrate that the development can be safely constructed as planned. Our comments and recommendations are discussed further in the following paragraphs. Class 3 landslide hazard areas are areas that, due to topographic and subsur- face conditions, have a high potential for slope instability. Based on our site reconnaissance, we generally concur with Terra's opinion regarding existing slope stability conditions on the site; however, previous cutting and filling on the slope adjacent to the site for construction of 44th Avenue South apparently resulted in landsliding. Accordingly, we judge there is a high potential for future slope instability both during and after site development if cuts and fills are not properly constructed. Specifically, we present the following primary review comments: ■ Based on review of the test pit logs investigating the landslide on 44th Avenue South, it appears the landslide involved movement of the upper, more weathered portion of the lacustrine deposits, likely as a result of Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 5 Applied Geotechnology Inca surcharge by the overlying fill. Other contributing factors likely included lack of adequate subdrainage at the base of the fill and inadequate keying and benching of the fill into the slope. The Terra reports recommend placement of fill soils on the steeper slopes in the northern portion of the site be minimized. Our review indicates fills on the order of 4 to 12 feet are planned along the north side of South 137th Street, and up to about 6 feet around the South 137th Place cul- de -sac. We recommend the developer prepare for review by Terra and the City detailed cross- sections in all planned fill areas indicating existing and proposed grades and illustrating how the fill will be keyed, benched, and drained as recommended in the geotechnical report. A typical detail should also be prepared illustrating the geotechnical engineer's recommended key at the toe of all proposed fills on slopes. Calculations supporting adequate safety factors against slope instabili- ty should be provided for review by the City. • Because of the relatively impermeable nature of the lacustrine deposits and the potential for saturation of fills placed on top of these materials, we judge that permanent subdrainage measures, such as the blanket drain recommended in the Terra report, will be essential for satisfactory long -term performance of the planned engineered fills. We suggest the developer, in conjunction with the geotechnical engineer, prepare detailed design cross - sections addressing subdrainage provisions for fills placed on slopes and underlain by lacustrine deposits. • Substantial earthwork operations will be required for the proposed development and will include significant cuts that may increase the extent of the site where the lacustrine soils will be at or near final grade. In addition, the Terra report indicates the majority of the site soils will be extremely difficult to work in wet weather. Accordingly, we judge it essential that earthwork operations be carefully planned in order to address.erosion and slope stability issues during construction. We recommend the developer prepare a detailed plan for earthwork operations for review by Terra and the City demonstrating how site preparation will be sequenced and performed, and what temporary erosion control measures will be used. Limiting earthwork to the drier summer months is',strongly recommended. If development will be performed in phases over 'a number of years, this should be reflected in the sequenc- ing plan, together with interim site restoration details for erosion control. • The grading plans indicate many of the proposed residences may be supported on a combination of dense or hard native soils and structural fill. We suggest Terra be requested to review the foundation details and comment on the need for connecting individual footings or supporting the houses on post- tensioned slabs as a possible means of reducing potential for differential settlement of the structures. • Because of the potential for slope instability if fills are not properly constructed, we judge it essential that the geotechnical engineer be required to monitor site preparation closely to confirm that earthwork is completed in accordance with their recommendations. Monitoring Ms. Denni Sh-frin City of Tuk ila May 17, 1993 Page 6 should for fi contro should tions' LOT DENSITY Lot Density Because of t that unless is properly slope stabi suggest tha avoiding mo Site Storm Applied Geotechnology Inc. nclude confirmation of stripping depths and keying and benching ls, subdrainage installation monitoring, and fill compaction as recommended in the Terra report. The geotechnical engineer lso confirm competent bearing and adequate embedment of founda- or structures constructed on Class 3 slopes. SITE STORM DRAINAGE (SCOPE ITEM 4) e moderate to steep slcpes and presence of clay soils, we judge he planned extensive grading for the proposed lot layout /density sequenced, constructed, and monitored, there is potential for ity problems to occur both during and after construction. We other layouts aimed at minimizing site cutting and filling and e steeply sloping portions of the site also be considered. raina e We understa d SEPA review comments by other agencies have included consider- ation of on -site infiltration of storm drainage. Terra states that all storm drainage, i cluding roof downspouts, should be tightlined to the storm drain. Because of he underlying relatively impermeable lacustrine soils and the potential f impacting slope stability, we concur with Terra that this site is not suit ble for on -site infiltration of stormwater. Biofiltrati of the aban ing Southga specificall • The swale a an existing or near the increase th south of th this swale The planned portion of retaining w siting a bi because of these lacu proposed sw Terra and t stability a Class 3 slo n swales are planned along the west side of the northern portion ored 44th Avenue South, and along the site property line border - e Park. Design and construction of biofiltration swales is not addressed in the geotechnical report. ong 44th Avenue South apparently will not require grading because.-:=1 'f\ --�,; ditch will be used. Infiltration from the swale could collect at contact between the weathered /unweathered lacustrine clay and potential for slope instability, as apparently occurred to the s swale location. We suggest consideration be given to lining o prevent infiltration. Swale along the north property line is situated on the lower the moderate to steep north slope. A 9 -foot maximum height 11 is shown on the upslope side of the swale. In our opinion, filtration swale at this location should be avoided if possible he slope and inclination, soil types, and need for excavation of trine soils. We recommend Terra review and comment on the le location. The developer should provide details for review by e City illustrating the type of retaining wall planned, including alyses and how it will be safely constructed at the base of this 'e. Ms. Denni Shefrin City of T kwila May 17,1 .93 Page 7 Applied Geotechnology Inc. We unders•and the current plan to reduce potential for increased runoff onto adjacent •roperties to the north will include tightlining all discharge from both biof ltration swales to the storm drain on 44th Avenue South at the northeast corner of the site. A shallow swale along the toe of the north slope could also be included to collect runoff from unpaved areas of the Area 1 lots an direct it to the storm drain system. We hope t is provides the information you require at this time. Please call if you ha e any questions or require clarification. Sincerely, APPLIED G3OTECHNOLOGY INC. • 6aKt Garry H. quires, Senior En•ineer Donald E. Bruggers, P.E. Principal Engineer GHS /DEB /j h attachmen I EXPIRES 10/23/9 3 1 Date August 11, 1990 May 5, 1992 May 5, 1992 October 16, 1992 November 8, 1992 December 22, 1992 February 12, 1993 February 23, 1993 March 15, 1993 April 23, 1993 March 9, 1993 • September 30, 1991 • CITY OF TUKWILA Document List for Review May 5, 1993 Author Terra Associates Dujardin Development Terra Associates Tukwila Public Works Tukwila Department of Community Development Terra Associates Tukwila Community Development Terra Associates Tietze & Associates Tukwila Community Development Charles Morgan & Associates /Erich O. Tietze & Associates Tukwila Ordinance No. 1599 -1 /i:,'. Applied Geotechnology Inc. Subiect Geotechnical Study Residential Plat Roadway Design Stability Evaluation 44th Avenue PRD and BLA Review Comments on development plans Review (initial) comments on development plans Updated Geotechnical Report. Residential Plat Review (additional) Additional comments Geotechnical conditions Additional consultation Drainage analysis Analysis of storm drainage Internal memorandum comments Proposed development Plan Sheets 1 through 7 Sensitive areas RCH ITECTS ..- .,,..- ...,..,. >.. RECEIVED MAR 2 31993 C FA R LE S M O R G 7301 BEVERLY LANE EVERETT, WA. 98203 March 22, 1993 Ms. Denni Shefrin, Associate Planner Department of Community Development City of Tukwila 6300 Southcenter Blvd. Siute #100 Tukwila, WA 98188 AN & ASSOCIATES RE: Fosterview Estates - (L92 -0065 and L92 -0066) Phone (206) 353 -2888 Enclosed are the additional items that you requested for the preliminary subdivision application. Retaining Walls: For the retaining walls we will be using the "Keystone" Reatining Wall System. Between the tract area and the road we will be using the 'Case B' : Constant Surcharge Load Design. Where ever structurally possible we will be using the 'Planter Wall System'. Each section of retaining wall will be designed by Keystone, based on the existing conditions and soil type. Actual design specs will be submitted at a later date, after exact location, length and height have been determined. Rockeries: A typical rockery detain is enclosed. Rockeries will only be used when retaining less than 4 feet in height. Tract Area: Tract "A" 1tBn Lot Size 78,355 sq.ft. 2.5,480 Mean Width 393' 274' Mean Depth 184' 91' If there are any additional items that you still need, please call me at 206 - 353 -2888 and I will get them to you. Sincerely, Jean Bates LICENSED: WASHINGTON • OREGON • CALIFORNIA • IDAHO • UTAH • ARIZONA • MONTANA WYOMING • COLORADO • NEW MEXICO • NEBRASKA • NEVADA MAR 22 '93 13:45 C MORGAN ASSOC 376 P02 TM , v\v _ t i Migkitglar Et�,''' • t1 . 1, - Y • y 1`r 1 III 111►u1.!i r1�11111 1J1 lr //i\� !]iii • � - Y�.`,. yam: `. •'L�:. 't:� ��. ��•� •c•;�. =� % `; cam' ,- V 1� J r. � � • tt jj III l' ll ":;f%i 11 �. .rte 14, vi BASIC PRODUCT STALL . The KeyStone Retaining ' all System w of construction in mind 1. plicity The following steps will guide you from�s t£��7ryt j ' ! ■ P STEP 1: PREPARATION OF SASE LEVELING ••.a ; , �� ' Excavate a shallow trench to the designed length ,w • dl nerisloni for your KeyStone wall. Provide apace behind the KeyStone unit;,to allow 'for,''a granular backflll drainage zone. KeyStone units should be placed pn,se' leveling pad of com• pacted, well draining granular fill [Le., nand, 112 ";to 3/4forut►hed.stone or gravel] at 95% Std. Proctor compaction or equal. Provlde,addltlon N;, renohzdepth for below grade placement of KeyStone unit!: on a ratio O,1" • s$ h 8' of wall height above grade. -; ,:' NOTE: Whin constructing walls leas than 3' high, Keystone unit: din soils. Drainage zone may vary due to set(, soil or engineering u ,,,, ,'� "' �. " MI STEP 2: INSTALLING. THE BASE -,,_-• OURSc ' „' ;.:• install the first course of KeyStone units side by, sidle„ . the prepared bassi. Level each unit side to side and fron(to back. Place the units suop that the kidney shaped void Is on the bottom surfacelr�Line up pins or back .edgs ot.unit,for.;stralght wall alignment. Units should touch, Ids point to side poIntlas:dlagrammidOor layout UICIEU 5 pag..3). Inorganic and alignment of curves see I • STEP 3: INSTALLING THE I ormatlon under DE8IG ERLQCKING PINS) Place the reinforced fiberglass pine Into the paired holes In eactirKsy8tons unit. Provide pins of correct length for appropriate unit size, :Ones in place, the pins will allow an automatic setback when Installing additional course as per STEP 5. ■ STEP 4: INSTALLING BACKFILL & COMPACTION : GL 3 "''' : A - ti..1!'r'V'r :,;,.. Fill all voids In and between KeyStone units and bshir}d', , nits This fill should con- sist of 112' to 314” crushed stone or clean, well draining granuluilll4hls allows for water drainage and compacts easily. Compact toellrriln atootsritlilaattlamatt.:; Backtlll behind gravel drainage zone using existing'soll,i :tNOT�. :Havy.olays or organic Bolls are not recommended due to wet er`,holdlng,,propertI.sJCompact to 95% Std. Proctor, Backtlll In .8' Ilfts on a course. by. *ourea;bislet:(I OIE::Oniy, lightweight walk behind mechanical compaction. • uI '' out Ithln 3' of the back of the units.] ;:tl Upon completion of backilll ind compaction; SWEET the ;unite to remove small pebbles, debris, etc. so the unite rest evenly upon one .. • the ' kill] and compact at every 8" course. S , `' ' .:. ` • ' <;: . ■ STEP 5: INSTALLING ADDITIONAL COURSES;._: Place the next course of KeyStone units over the posit onsd flbsrgtass pins id It Is centered on and bridges two uri is below In a running bond pattern „Pins should fit In- to kidney shaped recesses on ttom of unit. Pull the KeyStone module towards the face of the wall until the modul ekes full contact with dot and 5. ■ STEP 6: INSTALLING KEYST NE CAPS r' Use KeyStone Cap units to complete your wall. Plat efhe KsySttons Cap,ovsrpro- jecting pine on the unit belovl : Pull forward to The automatlo setback position. Backf111 and compact to finish glade. (NOTE: In areas of high public accessibility and vandalism, we recommend a cohstructlon adhesive or epoxy.cem nt,be used around the perimeter underside of the `cap prior to unit place nt, ' f : 'rka•;:'”. ''•,v The above Installation guidelines apply to all KeyStone unit slzaa. Theis 1 on procedures do not take Into account gsologloal variations In sit. and troll conditions and therefore elay'tettuln fYRhsr•inglnssdng con. iiderstton and detail. None of the Information enclosed herein V detail: GEOGRID INSTALLATION (I 4 For taller more critical walls, where geogrid Is pressures, use the following steps for Installation. ■ STEP 1: Follow steps 1 -4 on PRODUCT , :. S STE ' R1 INSTALLATION. • .I•i*pinnsdgjsog to eliminate loose ds. ■ STEP 2: Excavate the relnf `rced ,troll stake or securelfeck' of prior area 10 the maximum embedme t length. ;; • • a rl bsok}III ar�;oofnpas" Mont • INSTEP 3: Cut sections of geog to the specified length. Place proper orientation. [I.e, roll out 1 wards embankment]. Check man criteria for biaxial or uniaxlai ■ STEP 4:• • • Hook geogrld over fiberglass pins, assuring a mu tion between unit and geogrld. ld oft rolt'�".ratalnin�0c wall'uhit r:r :• algrld In ; BTEl�;7>Kcf ooss . M ,cam�paoled wall to backfll overgsogrd In8••IIlts� Prrovldsmini. facturere,,'.' mum d'•soll oars plot to d for equip• rids, •! : �; r, ment::aysr�grld , void tracked: .wheeled e yStone: •r•vshicles'dlrscttOrttirld;ori on Grid. • . Ing walt;la rf _t; fat connsc• • • STEP. CgMlnuo ..7 i fe n• • 9.f.3 cv • 40". („) 1993 COMMUNITY Gec grid quantity DEVELOPMEN The following factors will affect the amount of geogrid required to reinforce the soil behind the wall: Wall and embankment height (H ) • Googrid strength properties • Stiear strength of soil • Hydrostatic loads • Surcharge and slopes Geogrid quantities, embedment lengths (L), and layer frequencies should be adjusted accordingly. Case A: Basic wall without surcharge Let,el grade at top of wall with no surcharge or slope creating additional thrust. Case B: Constant surcharge load Parking lots, truck traffic or buildings affect the geogrid design by increasing the load on the reinforced soil mass. W be_ ()ALA., a, 4' i(1G,ot, 02276/ KEY BuyLine 2802 Geogrid installation cont. Case C: Sloping hillside surcharge In most situations, steeper, longer slopes place greater loads on retaining wall than Case B loads. The greater the degree of slope may mean an increase in geogrid quantities. Case D: Tiered walls Evaluate tiered walls carefully. Closely spaced tiered walls can create higher stresses on the lower wall sec- tion than an equivalent full height wall. The designer must determine the pressures exerted by the higher wall tier on the lower wall when the height of the lower wall is greater than or equal to the depth between terraces (Ht z D). Drainage considerations Poor drainage is a leading cause of retaining wall failui ';. Hydrostatic pressure accumulates, causing a destabilizing force in the reinforced soil mass. Designers and engineers should provide for external and internal drainage to protect the retaining wall structure. See drainage diagram at lower right for locations of drainage provisions. Location 1: Basic drainage Witai its mortarless, interlocking system, KEYSTONE walls drain naturally. No weep holes are needed. Location 2: Surface run -off Divert surface drainage with plastic (clay) soil cap or formed swale (soil or concrete). Redirect run -off by site design where possible. , Location 3: Embankment flow � Use an embankment drain system with outflow pipe at base to stop water flow into reinforced soil zone. Location 4: Ground water flow • Offset the effects of rising ground water with a drain one and outflow pipe beneath the leveling pad and reinforced soil zone. MAR 2 3 1993 Incorporate *specialty items into your next design. •�c�� 90? Corners'y -r I " � Wog Es riiIyiq C ' Eft tiz itil 11:01_:: i t4.;:m41..'7ii. atir _____ I �rI :1 VI ISSINV r Lighting / signage r. �jf • 44r J yyri Ld'�.I� I e NJ ,t� ' /' N'Y7� • I 1 l,l 1.I '111 ;i1;i.1,;i ,l�� 1�1 k �l• c .. I I • I• .I. ` .1 1 (j.� ��� �� ny' �� � It'�'K• KEl'S 1KINE �: ��, ; ,� (Planter WaII Syste RrN M4R 2319 coMMU r PRODUCT PROFILE STANDARD UNIT COMPAC UNIT MINI UNIT COMPAC CAP UNIT MINI CAP UNIT • : • DESIGN FLEXIBILITY. Variations in color, face texture and unit size provide unlimited creative options. Walls easily adapt to the contours of any landscape site •PERFORMANCE. Patented high-strength concrete modules and reinforced fiberglass pins offer permanent, maintenance-free walls. • BEAUTY. Quality manufacturing produces wall textures similar to natural quarried stone. • •ENVIRONMENTALLY RESPONSIBLE. KeyStone protects the en- vironment by using non-corrosive, non-deteriorating materials. •EASY INSTALLATION. Fast, mortarless, dry stack, labor saving construction. •COST EFFICIENT. Quality controlled mass production, national availability, installation ease and maintenance free walls give KeyStone the economic advantage. • GENERAL INFORMATION: • Compressive Strength 3000 psi • Absorption Rate 6 to 8 ibetit, . , • Composition High Strength, High Density Concrete STANDARD UNIT: ' : • Weight 94 It,/ (42.64 kg)" • Slip IrH • 18•W x 24•D (.2032m H x .4572m W x .6098m D)" • Exposed Face Area 1 Square Foot (Erx18').. .093 Square Meters (.2032m x .4572m) COMPAC UNIT AND CAP UNIT: • Weight ibe (35.38 kg)" ' • Size 78 8'H x 18'W x 12'D (.2032m H x .4572m W x ,3048m D)" • Exposed Face Area 1 Square Foot (8•x18).. .093 Square Meters (.2032m x .4572m) MINI UNIT AND CAP UNIT: • Weight 44 lbs (19.96 kg)" • Size 4"H x 18"W x 12'D (.1018m H x .4572m W x .3048m D)" • Exposed Face Area 'It Square Foot (4•x181 . .046 Square Meters (.1018m x .4572m) PINS: • Standard/Compec 1/2 • x91/4 • ' High Strength Pultruelon Fiberglass • Mini Ye x 51/4" High Strength Pultruslon Fiberglass • Tensile Strength 110,000 psi • Tensile Modulus 4 x 10' psi • Flexural Strength 128,000 pal • Flexural Modulus 4 x 101 psi • Short Beam Shear Strength6,400 psi • Specific Gravity 1.83 psi COLOR AND FACE TEXTURE OPTIONS:* • Factory Colors Gray, Tan, Brown • Custom Colors Special Quantity Orders Only - .: • Face Textures Sculptured Rockface, Corduroy s' • • *Verification should be made as to the availability of colore, face textures and product options by region. 'Actual unit weight and depth may vary cy region NOTE: Overall depth of unit varies with sculptured rockface texture. . . Specifications subject to change without aotice. — ZERO SETBACK POSITION [FRONT HOLES) AVAILABLE IN STANDARD, C"lAPAC AND MINI UNITS rr , — ONE INCH SETBACK POSITION [BACK HOLES) DIAGRAM A. AVAILABLE IN MINI CAP AND COMPAC CAP UNITS STRAIGHT SIDE CAP vi ANGLE SIDE CAP DIAGRAM B. 2 STRAIGHT ROCKFACE AVAILABLE IN ALL UNIT TYPES AND OPTIONS DIAGRAM C. PRODUCT OPTIONS* 1. DOUBLE PIN SETBACK (Diagram A) • Zero inch setback allows for vertical walls. Curves (convex/con- cave) can be built without gapping or overlapping procedure. Curves will transition into straight walls having either zero or 1" set- back. Corners, 90° inside and outside, can be easily built with zero setback units. • 1" setback provides am increased wall batta;e.(1 to9)fOjtathetics, and structural considerations. 2. STRAIGHT SIDE CAP (Diagram B) • As an aesthetic option, the triangular spacabetWeeti adjoining cap • units on straight walls is eliminated and reduced • on.•concave curves. Convex curves require angular sIded:unIts.., 4'1;413 3. STRAIGHT FACE (Diagram C) • • Face pattern available for aesthetic consideratiOn. , • • Straight side and face cap units provide beautiful', iesults:When building residential steps with KeyStone units. • RECE VFh MAR 2 3 1993 COMM(JMT., DEVELOPMENT IUYSRJ1NF M DESIGN CRITERIA The elongated tall section provides additional stability tor straight walls as the tall piece rests on the unit below it. GROOVES Remove the extended tall pieces at the grooves to re- turn the block shape to its 300 sides when building tigh convex curves. • GENERAL CONCEPT: The theory for gravity wall systems has been utilized since the building of the pyramids and rubble stone type walls. Through gravity weight and friction resistance based on material shape, the primary principal is to resist lateral earth pressure which develops sliding and over- turning failure potential. The KeyStone Retaining Wall System is a gravity retaining wall that utilizes its' weight and deep embedment shape [3:1 depth to height ratio] to resist lateral earth pressure. The mortarless, pinned connec- tion of units allows for a structurally in- terlocked network while providing free drainage of the hydrostatic loads behind the wall units. • NON-CRITICAL vs CRITICAL WALLS: For tow, noncritical applications, the KeyStone Retaining Wall can be used ef- fectively for gravity wall [non- geogrided] structures to the following heights: Recommended Maximum Wall Heights [w/o Soil Reinforcement.] STANDARD UNITS 6' -0" COMPAC UNITS 3' -0" MINI UNITS 3' -0" STANDARD & MINI COMBO 5' -0" [Use 4" shims at tails of Standards.] COMPAC & MINI COMBO 3' -0" Assumed Parameters For Walls Indicated Above: BASE SOIL Minimum 2500 psf bearing capacity. [Sandy gravel.] RETAINED SOIL Approximately 32° fric- tion angle. [Sandy gravel.] SURCHARGE No additional surcharge. [i.e., Slopes, structures, roadways, etc.] DRAINAGE Site run-off diverted, water table fluctuation or embankment drain -, age properly considered. For taller, more critical applications, the combination of KeyStone wall units and geogrid soil reinforcement allow for larger gravity wall structures capable of walls over 40 feet high. [Refer to GEOGRID CRITERIA.] NOTE: If your project involves one or more of the following... • SLOPING BACKFILL [steeper than 1 to 4]; • SURCHARGE LOADS; •HIGH GROUNDWATER TABLE; • MULTIPLE TIERS; • WALL BUILT ON SLOPE; • LOW SOIL SHEAR STRENGTH < 25 °; ...consider it a Critical Structure. Contact your KeyStone Representative for assistance. • WATER APPLICATIONS: *KeyStone can effectively be used In water situations such as ponds, creeks, lakes rivers and run-off channels. Evaluation of water level conditions, flow velocity, backfill soil type and foundation soils are very important. If a free draining system is maintained with KeyStone wall ,units and backfill soils [i.e., crushed rock] the main Item of consideration is foundation soil and wall base protection. Wave ac- tion and scouring effects should be eval- uated by a qualified hydrological engl. neer. Critical applications may require erosion resistant footing design and rip - rap protection. Consult your KeyStone Representative for further details. 022781KEY BuyLins 2802 • CURVES: •Building curves Into your KeyStone wall requires a few special considerations. Convex curves require a small gap be- tween adjacent units [see diagram For concave curves, touching edge of each unit should be slightly overlapped [see diagram]. Gapping and overlapping will vary somewhat with the degree of cur- vature desired. A general guideline Is as follows: At the base course, set units with gap or overlap so pins of adjoining units are 12" apart [see diagram]. • CREATIVE OPTIONS: •Combination of module sizes [l.e., sizes 8 "•4 " -8 ", and any combination thereof]. •Combination of factory or custom pro- duct colors, geometric patterns, horizon- tal bands, etc. • Face texture combinations [rockface and corduroy]. • SPECIALTIES: • Guard Rails, Highway Barriers, Fences, Etc.: [Vertical posts of steel, wood, con- crete can be placed within the KeyStone retaining wall structure.] • 90° Corners: [Inside and outside.] • Sound Barriers: [Double wall with gravel core fill.] •Steps: [KeyStone units as tread /riser.] • Water Applications. 3 Al: ' Alt0 Qt a• Q . I '` I I �I<I� .Ii ,,� t \�` ;1 ,: :....., Pr I \ 4 / :1* 11 11111 1 e" y - 1 ..• # ��1 r & a 5 II ._ I } 3 • 1 114.1titf• I, y 1:' � 0" ; % ... ___• , , tv;... , ,_ — 6: iiiii4 sorMr:'• fiz,7011r-14-211 NO i t4/1 4 BASIC PRODUCT INSTALLATION The KeyStone Retaining :Wail System was developed with simplicity of construction in mind. The following steps will guide you from start to finish. • STEP 1: PREPARATION OF BASE LEVELING PAD Excavate a shallow trench to the designed length and width dimensions for your KeyStone wall. Provide space behind the KeyStone unit to allow for a granular backfill drainage zone. KeyStone units should be placed on a 6" leveling pad of com- pacted, well draining granular fill [1..., sand, 112" to 314" crushed stone or gravel] at 95% Std. Proctor compaction or equal. Provide additional trench depth for below grade placement of KeyStone units on a ratio of 1" below grade for each 8" of wall height above grade. • NOTE: When constructing walls less than 3' high, KeyStone units can be placed on firm undisturbed, Inorganic soils. Drainage zone may vary due to site, soli or engineering requirements. • STEP 2: INSTALLING THE BASE COURSE Install the first course of KeyStone units side by side over the prepared base. Level each unit side to side and front to back. Place the units such that the kidney shaped void is on the bottom surface. Line up pins or back edge of unit for straight wall alignment. Units should touch side point to side point as diagrammed. For layout and alignment of curves see Information under DESIGN GUIDELINES (page 3). INSTEP 3: INSTALLING THE INTERLOCKING PINS Place the reinforced fiberglass pins Into the paired holes In each KeyStone unit. Provide pins of correct length for appropriate unit size. Once In place, the pins will allow an automatic setback when Installing additional courses as per STEP 5. • STEP 4: INSTALLING BACKFILL & COMPACTION Fill all voids in and between KeyStone units and behind units. This fill should con- sist of 112" to 314" crushed stone or clean, well draining granular fill. This allows for water drainage and compacts easily. Compact to eliminate potential settlement. Backfill behind gravel drainage zone using existing soils. [NOTE: Heavy clays or organic soils are not recommended due to water holding properties.] Compact to 95% Std. Proctor. Backfill in 8" lifts on a course by course basis. [NOTE: Only lightweight walk behind mechanical compaction equipment should be'used within 3' of the back of the units.) Upon completion of backfill and compaction, SWEEP the units to remove small pebbles, debris, etc. so the units rest evenly upon one another. Backfill and compact at every 8" course. • STEP 5: INSTALLING ADDITIONAL COURSES Place the next course of KeyStone units over the positioned fiberglass pins so it is centered on and bridges two units below in a running bond pattern. Pins should fit in- to kidney shaped recesses on bottom of unit. Pull the KeyStone module towards the face of the wall until the module makes full contact with both pins. Repeat STEPS 3, 4 and 5. • STEP 6: INSTALLING KEYSTONE CAPS Use KeyStone Cap units to complete your wall. Place the KeyStone Cap over pro- tecting pins on the unit below. Pull forward to the automatic set back position. Backfill and compact to finish grade. [NOTE: I in areas of high public accessibility and vandalism, we recommend a construction adhesive or epoxy cement be used around the perimeter underside of the cap prior to unit placement.] The above installation guidelines apply to all KeyStone unit sizes. These installation procedures do not take Into account geological variations In site and soli conditions and therefore may require further engineering con. sideration and detail. None of the information enclosed heroin should be construed as a construction detail. GEOGRID INSTALLATION (PATENTED PROCEDURES)*** For taller more critical walls, where geogrid is required to resist greater lateral earth pressures, use the following steps for installation. d. r:'_, • STEP 1: Follow steps 1 -4 on PRODUCT • STEP 5:•" To pretension geogrid, pull INSTALLATION. pinned geogrid taut to eliminate loose folds. IN STEP 2: Excavate the reinforced soil Stake or secure back edge of geogrid prior and area to the maximum embedment length. to STEP 6:ilnsall nfelxt cand comaction. ourse of KeyStorte • STEP 3: Cut sections of geogrid off roll retaining wall units. to the specified length. Place geogrid in STEP 7: Proceed to place compacted proper orientation. [i.e., roll out from wall to backfill over geogrid in 8" lifts. Provide mini- wards embankment). Check manufacturers mum 6" soil coverage prior to driving equip - criteria for biaxial or uniaxial geogrids. ment over grid. Avoid tracked or wheeled • STEP 4:••• Hook geogrid over KeyStone vehicles directly on grid, or turning on grid. fiberglass pins, assuring a secure connec- • STEP 8: Continue steps 3 -7 until retain - tion between unit and geogrid. ,' ing wall is complete. REceiveD HAR 231993 ENT, KEYS-RAE CASE B. SURCHARGE 250 pst GEOGRID CRITERIA • GENERAL CONCEPT The structural principle of reinforced soil retaining wails is quite simple. By com- bining KeyStone concrete wall units, geo- grid reinforcement and compacted soils over the geogrid, a reinforced soil mass Is created to resist calculated destablizing forces from lateral earth pressure and sur- charge loads. Essentially this composite forms a larger gravity wall structure. • GEOGRID REINFORCEMENT Geogrids are manufactured synthetic products of high density polyethylene or polyester materials, formed or woven into a grid like open pattern. With high strength, high modulus features, geogrids are effec- tively used in horizontal layers to create a tensile capacity for shear resistance within the reinforced soil mass. • ADVANTAGES 1.Economic benefits due to utilizing ex- isting site soils in most cases. Saves on balancing of cut and fill sites and elim- inates need for select imported backflll soil. 2.Wall builds up at rate of backflll and compaction process. No waiting on shop drawings, forms, steel, or for concrete to reach cure strength prior to rernoving forms and installing backfill. 3.Safer construction due to wall and back - f 111 proceeding up together. No backfilling behind formed wall and embankment. 4.Flexible vs Rigid System - allows wall to handle differential settlement due to frost, soil consolidation, etc. Distributes weight of structure uniformly over larger area. Avoids localized overstress of foun- dation soils. Walls can be built without structural footing or base frost protection. 5.Geogrids are synthetic materials not af- fected by external factors evident in soils, [/.e. water, micro - organisms, alkali or acid soils]. • DESIGN METHODOLOGY In evaluating the design for a gravity type geogrid reinforced soil retaining wall, the design engineer analyzes the following criteria: •SOIL PROPERTIES — Determine repre- sentative shear strength parameters [an- gle of internal friction] and moist unit weight for each soil zone. Foundation Soil /Retained Embankment Soil /Rein- forced Backfili!Core and Drainage Fill. NOTE: Values for cohesion in soil are not utilized in structural analysis. Qualified Geotechnical Engineer should determine soil properties. •EVALUATE EXTERNAL STABILITY — The four standard modes of failure for ex- ternal stability should be addressed. Slid- ing [1.5 F.S.], Overturning [2.0 F.S.1, Bear- ing Capacity [2.0 F.S.] and Global Stabil- ity [F.S. to be determined by qualified Engineer]. •EVALUATE INTERNAL STABILITY — In order for the Engineer to address the three modes of internal stability, [Pullout, Tensile Overstress and Localized Stress Between Grid Layers], specific geogrid manufacturer material properties must be known. • Long term allowable design strength. •Tensile modulus at low strain levels. •Service life. •Ability to interlock with soil. • Actual design methods, criteria and engineering analysis are beyond the scope of This document. Con. suit your KeyStone Representative for specific geogrld engineering analysis, design strengths and product availability. Design of geogrid soli reinforced walls should be specifically analyzed by a qualified engineer. 02278/KEY BuyLins 2802 • GEOGRID QUANTITY Geogrid quantity, embedment length [L], horizontal layer frequency and place- ment elevation are increased as loading conditions exerting forces on the reinforced soil zone are affected b * Wall heightt /embankme nt the [H] following: •Geogrid strength properties •Shear strength of soil • Hydrostatic loads • Surcharge and slopes [See CASES A- D] • CASE A. BASIC WALL WITHOUT SUR- CHARGE Level grade at top of wall with no sur- charge or slope creating additional thrust. • CASE B. CONSTANT SURCHARGE LOAD Auto parking lots, truck traffic, buildings or structures affect the geogrid design by Increasing the Toad condition on the rein- forced soil mass. • CASE C. SLOPING HILLSIDE SUR- CHARGE Steeper, longer slopes place greater loads on retaining wail, than CASE B. loads in most situations. Greater the degree of slope = increased geogrid quantities. • CASE D. TIERED WALLS Tiered walls must be carefully evalu- ated. Closely spaced tier walls can create higher stresses on the lower wall section than an equivalent full height wail. Design- er must determine the pressures exerted by the higher wall tier on the lower wall when [H z 2L]. DRAINAGE DIAGRAM KEYSTONE RETAINING WALL SYSTEM O r• r MINIM MINN IMM rte. r■ C .4.1's; RENFORCED • 90IL 20N4'•' erki • DRAINAGE CONSIDERATIONS: Most retaining wall failures are caused by poor drainage, leading to the accumula- tion of hydrostatic pressure which causes a destabilizing force In the reinforced soil mass. Proper design and engineering should consider provision for external and internal drainage to protect the entire retaining wall structure. See DRAINAGE DIAGRAM for locations of drainage provisions. Location 1. BASIC WALL DRAINAGE KeyStone wall naturally drains due to mortarless yet Interlocked system and drainage zone. No weep holes needed. Location 2. SURFACE RUN -OFF Provide plastic [clay] soli cap or formed swale [soil or concrete] to divert surface drainage. Redirect surface drainage by site design where possible. Location 3. EMBANKMENT FLOW Use chimney drain system with outflow pipe at base of embankment to eliminate water flow Into reinforced soli zone. Location 4. GROUND WATER FLOW Effects of rising ground water can be offset by using a ground blanket drain zone and outflow pipe beneath leveling pad and reinforced soil zone. 5 RECEIVE MAR 2 3 7993 IDEVELOPIVIENT • RETAINING WALL SYSTEMS • SPECIFICATION GUIDELINES KEYSTONE CONCRETE MODULAR RETAINING WALL SECTION 02276 • PART 1: GENERAL 1.01 DESCRIPTION A. Work Includes furnishing and Installing modular block retaining wall units to the lines and grades designated on the construction drawings and as specified herein. 8. Work includes preparing foundation soil, fur- nishing and Installing leveling pad, unit fill and backllll to the lines and grades designated on the construction drawings. C. Furnishing and Installing all appurtenant mate• vials required for construction of the retaining wall as shown on the construction drawings. 1.02 RELATED WORK A. Section 02275 — Geogrid Soil Reinforcement. 1.03 REFERENCE STANDARDS A. ASTM C90 -85 Hollow Load Bearing Masonry Units. 8. ASTM 6140 -75 Sampling and Testing Con. crate Masonry Units. C. ASTM 6145 -85 Solid Load Bearing Concrete Masonry Units. 1.04 DELIVERY, STORAGE AND HANDLING A. Contractor shall check the materials upon delivery to assure that proper material has been received. 8. Contractor shall prevent excessive mud, wet ce• men/, epoxy, and like materials which may affix themselves, from coming In contact with the materials. C. Contractor shall protect the materials from damage. Damaged material shall not be Incor- porated Into the retaining wall structure. 1.05 SUBMITTALS A. Samples of all products used In the work of this section. B. Latest edition of manufacturers speclflcations for proposed materials, method of Installation and list of material proposed for use. 1.08 QUALITY ASSURANCE A. Soil testing and Inspection service for quality control testing during earthwork operations will be supplied by the owner. • PART 2: PRODUCTS 2.01 CONCRETE UNITS A. Masonry units shall be KeyStonee Retaining Wall Units as manufactured by' B. Concrete wall units shall have a minimum net 28 day compressive strength of 3000 psi. The con- crete shall have a maximum moisture absorption of 6 to 8 Ibslft'. C. Exterior dimensions may vary in accordance with ASTM C90 -85. Standard and Compac units shall have a minimum of 1 square loot lace area each. Mint units shall have a minimum 1/2 square loot face area each. D. KeyStone Standard units shall provide a mini- mum of 150 psf of wall face area. Fill which Is contained within the dimensions of the units may be considered as 80% effective weight. E. Units shall have angled sides capable of con- cave and convex alignment curves with a minimum radius of 3.5 feet. NOTE: Where applicable, for straight walls use non•angled straight side cap units.. F. Units shall be Interlocked with non•corroslve fiberglass pins. G. Units shall be Interlocked as to provide a mini. mum 1/4 Inch setback per each course of wall height. NOTE: Where applicable, zero setback or one Inch setback per course options can be used. 2.02 FIBERGLASS CONNECTING PINS A. Connecting pins shall be 112 Inch diameter ther- moset Isopthalic polyester resin/ pultruded fiberglass reinforcement rods. B. Pins shall have a minimum flexural strength of 128,000 psi and short beam shear of 6400 psi. 2.03 BASE LEVELING PAD MATERIAL A. Material shall consist of compacted sand, gravel, crushed rock or leveling concrete (non. reinforced) as shown on construction drawing. The compacted leveling pad shall bo a minimum 6 Inches thick. When using a non•relnforced leveling concrete option, 1" to 3" thick, maintain the total leveling pad thickness. 2.04 UNIT FILL A. Fill for units shall be free draining crushed stone, 3/8' to 3/4', or coarse gravel (no more than 5% shall pass the No. 200 sieve with a max• Imum size of 3/41. Gradation of the fill shall be approved by the Engineer. B. Place recommended 1111 behind the retaining wall units. 2.05 BACKFILL A. Materiel shall be Insltu soils when approved by the engineer unless otherwloe apeclfled In the drawings. Unsuitable soils for backllll (heavy clays or organic soils) shall not be used In the beckfill or In the reinforced soli mass. B. Where additional fill Is required contractor shall submit sample and specifications to the engl• neer to determine If acceptable. • PART 3: EXECUTION 3.01 EXCAVATION A. Contractor shall excavate to the lines and grades shown on the construction drawings. Over excavation shall not be paid for and replacement with compacted fill and/or wall system components will be required at contrac• tor expense. Contractor shall be careful not to disturb embankment materials beyond lines shown. 3.02 FOUNDATION SOIL PREPARATION A. Foundation soil shall be excavated as required for footing dimensions shown on the construc• tlon drawings, or as directed by the Engineer. B. Foundation soil shall be examined by the Engineer to assure that the actual foundation soli strength meets or exceeds assumed design strength. Solis not meeting required strength shall be removed and replaced with acceptable material. C.Over•excavated areas shall be filled with ap• proved compacted backllll material. 3.03 BASE LEVELING PAD A. Leveling pad materials shall be placed as shown on the construction drawings, upon undisturbed Insltu Bolls, to a minimum thickness of 8 Inches. B. Material shall be compacted so as to provide a level herd surface on which to place the first course of unite. Compaction shall be to 951/4 of standard proctor for sand or gravel type mate. rlals. For crushed rock, material shall be densely compacted. C. Leveling pad shall be prepared to Insure com• piete contact of retaining wall unit with base. D. Leveling pad materials shall be to the depths and widths shown. Contractor may opt for using reduced depth of sands, gravel or cruahed rock using a concrete topping. Concrete shall be un• reinforced and a maximum of 1' to 3' thick. 3.04 UNIT INSTALLATION A. First course of concrete wall units shall be placed on the base leveling pad. The units shall be checked for level and alignment. The first course is the most Important to Insure accurate and acceptable results. B. Insure that units are In full contact with base. C. Units are placed side by side for lull length of wall alignment. Alignment may be done by means of a string line or offset from base line. D. Install fiberglass connecting pine and fill all voids at units with unit 1111 material. Tamp 1111. E. Sweep all excess material from top of units and Install next course. Insure each course Is com• pletely unit filled, backfllled and compacted prior to proceeding to next course. F. Lay up each course Insuring that pins protrude Into adjoining courses above a minimum of one Inch. Two pins are required per unit. Pull each unit forward, away from the embankment, against pine In the previous course and backllll as the course Is completed. Repeat procedure to the extent of wall height. G. As appropriate where the wall changes eleva• lion, units can be stepped with grade or turned Into the embankment with a convex return end. Provide appropriate burled units on compacted leveling pad In area of convex return end. , 3.05 CAP INSTALLATION A. Place KeyStone Cap units over projecting pins from unite below. Pull forward to set back poll. lion. Back 1111 and compact to finished grade. B. As required, provide permanent mechanical con- nection to wall unite with construction adhesive or epoxy. Apply adhesive or epoxy to bottom our• face of cap units and Install on units below. 3.08 GEOGRID INSTALLATION A. Follow the requirement8 of Section 02275, GEOGRID SOIL REINFORCEMENT. RECEIVED MAR 231993 DEVELOPMENT TYPICAL WALL SECTION TERMS MINIMJM AUTOMATIC SETBA.X APES COURSE KEYST•y°E'° CAP UNIT .•N.rtw.IOY,•O 24• 1.. TOPSOIL rt''' Ir_ - 'hee b:; i , � t 4 Ii i I A5' Y r1Tll KEYST )NE'. A1_ I I Il STANDARD UNIT 9'H. TOPSOIL'D 1.1 roPSOa q. swill a;Ywi'Etw { ,O' III1 VARIES "= • APPROX. 1 a" COURSE PER 0'.0; VERTICAL H. I{{ Ill . OMPACTED REINFORCED BACKFILL ZONE o; o; Y, RETAINED BACKFILL oy C. ) CRITICAL FAILURE PLANES BEING ANALYZED GEOGRID ATTACHED TO FIRER GLASS PINS AT UNIT DRAINING GRANULAR COMPACTED BASE AND BACKFILL FOUNDATION SOIL Oi yin SPECIFICATION GUIDELINES GEOGRID SOIL REINFORCEMENT SECTION 02275 • PART 1: GENERAL 1.01 DESCRIPTION A. Work Includes furnishing and Installing geogrid reinforcement, wall fill, and backllll to the lines and grades designated on the con. structton drawings. B. Work Includes furnishing and installing all appurtenant materials required for construc• tion of the geogrld reinforced soil retaining wall as shown on the construction drawings. 1.02 RELATED WORK A. Section 02276 KEYSTONE CONCRETE MODULAR RETAINING WALL. 1.03 REFERENCE STANDARDS A. See specific geogrld manufacturers reference standards. 1.04 DELIVERY, STORAGE AND HANDLING A. Contractor shall check the geogrid upon delivery to assure that the proper material has been received. B. Geogrids shall be stored above —20 °F. C. Contractor shall prevent excessive mud, wet cement, epoxy and like materials which may affix themselves to the gridwork, from coming in contact with the geogrid material. D. Rolled geogrid material may be laid lot or stood on end for storage. 1.05 SUBMITTALS A. Samples of all products used In the work of this section. B. Latest edition of manufacturers specilica• lions for proposed materials, method of in- stallation and list of material proposed for use. 1.08 QUALITY ASSURANCE A. Soli testing and inspection services for quality control testing during earthwork operation will be supplied by the owner. • PART 2 PRODUCTS 2.01 DEFINITIONS A. Geogrld products shall be high density polyethylene expanded sheet or polyester woven fiber materials, specifically fabricated for use as soil reinforcement. B. Concrete retaining wall units are as detailed on the drawings and are specified under Section: 02276 KEYSTONE CONCRETE MODULAR RETAINING WALL. C. Wall 1111 Is a free draining granular material used within the concrete units. D. Backflll is the soil which Is used as 1111 for the reinforced soil mass. E. Foundation soil Is the Insltu soil. 2.02 GEOGRID A. Geogrld shall be the type as shown on the drawings having the property requirements as described within the manufacturers speclflca• lions. 2.03 ACCEPTABLE MANUFACTURERS A. A manufacturer's product shall be approved by the Engineer prior to bid opening. • SPECIAL CONSIDERATIONS: •Geogrid can be interrupted by periodic penetration of column, pier or footing structures. • Alternatives when site conditions wit, not allow geogrid embedment length. 1.KeyStone can be designed and built as a reinforced masonry unit wall. Cores will accept vertical reinforcing and grout. 2.Deadman - tie back anchor option. Reduces or eliminates excavation and backf ill requirements. 3.Increased wall batter by sloping level- ing pad or footing. [i.e. 8 to 1, 4 to 1 etc.] Consult your KeyStone Representative for details. 02278/KEY BuyLln. 2602 • PART 3: EXECUTION 3.01 FOUNDATION SOIL PREPARATION A. Foundation soil shall be excavated to the lines and grades as shown on the construc• Lion drawings or as directed by the Engineer. B. Foundation soil shall be examined by the Engineer 10 assure that the actual foundation soil strength meets or exceeds assumed design strength. C. Over-excavated areas shall be tilled with op- proved compacted backllll material. D. Foundation soli shall be proof rolled prior to 1111 and geogrld placement. 3.02 WALL ERECTION A. Wall erection shall be as specified under Sec- lion: 02276 KEYSTONE CONCRETE MODULAR RETAINING WALL. 3.03 GEOGRID INSTALLATION A. The geogrld soil reinforcement shall be laid horizontally on compacted backflll. Connect to the concrete wall units by hooking geogrld over fiberglass pins. Pull taut, and anchor before backflll Is placed on the geogrld. B. Slack In the geogrld at the wall unit connec- tions shall be removed. C. Geogrld shall be laid at the proper elevation and orientation as shown on the construction drawings or as directed by the Engineer. D. Correct orientation (roll direction) of the geogrld shall be verified by the contractor. E. To pretension geogrld, pull pinned geogrid taut to eliminate loose folds. Stake or secure back edg• of geogrld prlor to and during backllll and compaction. F. Follow manufacturers guidelines relative to overlap requirements of unlaxlal and biaxial geogrids. 3.04 FILL PLACEMENT A. Backflll material shall be placed In 81nch lifts and compacted to 95% of Standard Proctor. B. Backflll shall be placed, spread, and com- pacted In such a manner that minimizes the development of slack or loss of pretension of the geogrid. C. Only hand - operated compaction equipment shall be allowed within 3 feet of the back sur- face of the KeyStone units, D. Backflll shall be placed from the wall rearward Into the embankment to Insure that the geogrid remains taut. E. Tracked construction equipment shall not be operated directly on the geogrld. A minimum backflll thickness o16 Inches Is required prior to operation of tracked vehicles over the geogrid. Turning of tracked vehicles should be kept to a minimum to prevent tracks from displacing the fill and damaging the geogrld. F. Rubber•tIred equipment may pass over the geogrld reinforcement at slow speeds, less than 10 MPH. Sudden braking and sharp turn• Ing shall be avoided. 7 RECEIVED MAR 2 31993 CI O OpMENT ROtcriKERY For Hat backslope, surface should be impervious a sloped to drain. • I to HEIGHT 4-11vcrA'- -See Notes 1 -3 for permit & certification re;uirmerts. !min. 12" 6. STANDP.` 2 (or flatter) ,. Free - draining' backfill 1max:'5' /. fines min. 8" wide 'layer - of 2 "- 4" quarry spoils adjacent to rockery.. - Stable cut face In native, material (see Note `7).• I" (or less).. diameter, :; woshed gravel; min: 6" 'covet over;µ' „pipe`'tihin gravel under: :pipe Firm, • undisturbed soil No aL 1. .Rockeries 4' and over in hcight require • a b. -„ r g r rockeries between 4' and 6' high, t ▪ staller or contractor shall prova,_ letter to the building inspector p •to final inspection certifying that t ubgrade and . drainage have been prepa accord .with these standards. ▪ cries 6' and over in height require e`nf;X ing supervision by special inspector 306b), which at minimum • shall consist o rection and written certification of subgra•-, ac:ement of base course and drainage, and i rockery. _._ Rock••shall be sound.and have minimum ',density of.160 pounds per cubic'foot. S. The long dimension of all rocks shall be placed perpendicular to the wall. Each rock,should bear on two rocks in thetier below. Min. 4" diom. pert pipe; min. 1% continuous slope to outlet; pipe filar cut face lined with filter fabric (Mirafl or equivalent). GENERAL NOTES PLACEMENT: .STRUCTUR >...•: No footings "of :struetw s' . .:; encludinp;othsr :rockeries) may •bawl” stippled area. ASr: 3 - 6. Improved walking surfaces above and ad- j acent to rockeries over 30'!. 'in height shall be protected,by a guardrail conforming to UBC 1711. Y:'' ;, 7. Rockeries are erosion- controlsttructures, not retaining walls.t Native material must be stable and ':free- standing in. cut face: 8. Any deviation in design 'or in placement of adjacent structures must be submit- ted with. the 'seal' of a civil ..engineer currently licensed.:.' in the state of WaShirzton. RECEIVED MAR 2 31993 DEVELOPMENT . , Incorporate specialty items inti),your next design. .!. . , (.; 90:f Lorners Stairsffipi -s • Nirter • lighting / signage K ,•••' 7.%wk-TIP, wyki 4 • . :4, 4 1+,0 )....1%;,/".;/::::, • tot).."'".."•P,?'" • !. 1 -1:E am.A=A:111, viTql oil ni,lifit:s;,. IIII f.st'la Li. Atiktif MN. • , g . y ihr-T...X.t1.. { *.-17.-1.1.( itX. • ,1 II ,..,..ta , ■ Elilt..11 .1-7 4.,'. ill)) .a. .*7- II 1 C Ci!1:, ffstr,i1 "' 1. t.,!,,,,,,. r..e;ie=, ...„.4■1 r, is ,, _ ... _ , if ..,..., .... _ 1 ci ,Mill•-.:1R0;0450, ' :rt ;• Tiri-TriTi: 6.;.17 11 11 1'1 1111.1-11i, •. T ;.T T;.• .Laj.,421, T rif • t?, • 02276 /KEY BuyLine 2802 d installation cont. Geogrid quantity t# The following factors will affect the amount of geogrid required to reinforce the soil behind the gall: • Wall and embankment height (H ) • Geogrid strength properties • Shear strength of soil • Hydrostatic Toads • Surcharge and slopes Geogrid quantities, embedment lengths (L), and layer frequencies should be adjusted accordingly. k 11 H. Geogrid KEYSTONE Case A: Basic wall without surcharge Level grade at top of wall with no surcharge or slope creating additional thrust. Case B: Constant surcharge Toad Parking lots, truck traffic or buildings affect the geogrid design by increasing the load on the reinforced soil mass. •r. A KEYSTONE KEYSTONE Case C: Sloping hillside surcharge In most situations, steeper, longer slopes place greater loads on retaining wall than Case. B loads. The greater the degree of slope may mean an increase in geogrid quantities. Case.. 0: Tiered walls Eva'uate tiered walls carefully. Closely spaced tiered walls can create higher stresses on the lower wall sec: tion than an equivalent full height wall. The designer must determine the pressures exerted: oy the higher wall tier on the lower wall when the height of the lower wall is greater than or equal to the depth between terraces (H t > D). Drainage considerations Poor drainage is a leading cause of retaining wall failure. Hydrostatic pressure accumulates, causing a destabilizing force in the reinforced soil mass. Designers and engineers should provide for external and internal drainage to protect the.;retaining wall structure. See drainage diagram at lower right for locations of drainage provisions. `s Location 1: Basic drainage • Willi its mortarless, interlocking system, KEYSTONE walls drain naturally. No weep holes are deeded. Location 2: Surface run -off i Divert surface drainage with plastic (clay) soil cap or formed swale (soil or concrete). Redirect run -off b', site design where possible. eLocation 3: Embankment flow Use an embankment drain system with outflow pipe at base to stop water flow into reinforced soil zone. Location 4: Ground water flow OfL et the effects of rising ground water with a drain zone and outflow pipe beneath the leveling pad and reinf: reed soil zone. Geogrid KEYSTONE • NETM .I PRODUCT PROFILE ( STANDARD UNIT COMPAC UNIT MINI UNIT COMPAC CAP UNIT MINI CAP UNIT ZERO SETBACK POSITION [FRONT HOLES] AVAILABLE IN STANDARD, C'.IMPAC AND MINI UNITS — 0,1E INCH SETBACK POSITION [BACK HOLES] DIAGRAM A. 2 AVAILABLE IN MINI CAP AND COMPAC CAP UNITS STRAIGHT SIDE CAP va ANGLE SIDE CAP DIAGRAM S. STRAIGHT ROCKFACE AVAILABLE IN ALL UNIT TYPES AND OPTIONS DIAGRAM C. ,r1. ?'',,: • DESIGN FLEXIBILITY. Variations In coloOace•':texture and unit size provide unlimited creative options.`;Walla!' asily`adapt.to the contours of any landscape site. :. ; ri 'At;"' . • PERFORMANCE. Patented high- strengtht:co crete modules,and reinforced fiberglass pins offer permane I al'te ante -free :;f • BEAUTY. Quality manufacturing produces., al texture =.;si far to natural quarried stone. '- , • . _�."A. ,� Oir,, .. • 'ENVIRONMENTALLY RgSPONSIBLE. KeyStone protects the en- vironment by using noncorrosive, non- deter4oratIng materials.' • EASY INSTALLATION. Fast, mortarless, dry •'stack.`labor saving construction. •COST EFFICIENT. Quality controlled massproductionnatlonal availability, installation "ease and maintenance .free walls give KeyStone the economic. advantage. :'.v; t. . 4;,* '`k ,Ia. ,..%, GENERAL INFORMATION: 1, • Compressive Strength 3000 psi • Absorption Rate 8 to 8 Ibsf11, 3. • Composition High Strength, High Density Concrete STANDARD UNIT: -4%,. • Weight 94Ibe (42.64 kg) , .r ;bl + • Size 8•H x 18•W x 24•D (.2032m H x'.4572m W x':t1096m D)•!? • Exposed Face Area 1 Square Foot (8 "x181.. .093 Squarti Meters (.2032m .4572m • Weight COMPAC UNIT AND CAP UNIT: hy':y*Y� y�+�y7y�>'' IYJ"iq' 781be (35.38 kgr a • • Size 8•H x 18•W x 12•D (.2032m H x'.4572m W x .3046m D)•' • Exposed Face Area 1 Square Foot (8'x181.. .093 8quar Meters (.2032m_ft .4872m)!4 MINI UNIT AND CAP UNIT: "_''^., • Weight 441os (19.98kg)•'e• -.1w ' .`� ' ru';8•t • Size 4•H x 18'W x 121D (.1016m H x .4572m W x•.3048m D)•!' • Exposed Face Area V. Square Foot (4•x181. .046 Square Meters (.1010m x .4572m) PINS: i' a;.,,' %�}- ?,14.1A, cs:, 5_ :.^ J '....fp : • Standard (Corneae Y.• X 9 / ' ' High Strength Pultruslon Fiberglass' • Mini V.• x,5' /•' High Strength Fultruslon Flbirglau,;; • Tensile Strength 110,000 psi ` •' r'f ' • ' 't •.W::, • Tensile Modulus 4 x 10' pal � .r l.J ..-, r ; ' "t '` • Flexural Strength 128,000 psi ' • Flexural Modulus 4 x 10' pal • Short Beam Shear Strength8,400 pel • Specific Gravity 1.83 psi , COLOR AND FACE TEXTURE OPTIONS:* • Factory Colors Gray; Tan, Brown • Custom Colors Special Quantity Orders Only4.. , `y..., • Face Textures Sculptured Rockface, Corduroy. • yj: lr,. ±• . k r 'Verification Should be made as to the availability of colors, face textures-And product options by region, ••Actual unit weight and depth may vary by region ± r , 4;.rq ... yM1 �, r NOTE Overall depth of unit varies with sculptured rockface texture.:: ,, • : Specifications subject to change without notice.' }' PRODUCT OPTIONS` 1. DOUBLE PIN SETBACK (Diagram A) i;; I ,;;,. ;`,,,,TMs., .. • Zero inch setback allows for vertical: walla::Curves, (convexlcon- cave) can be built without gapping or;'overlappinVprocedure. Curves will transition Into straight walls having either zero or 1" set- back. Corners, 90° inside and outside ;,ca • II , .ull , 1 zero • 1" setback provides an tincreased waIlbat = $elics' and structural considerations. ?:'r,a j• }, 2. STRAIGHT SIDE CAP Dia ram•B `.':t �, 2, : • As an aesthetic option),the triangular space • = tWeen adJolnIng cap "' units on straight walls Is eliminated::and'treduc: "• f co cave curves. Convex carvesrequire angular Id = • :" . 3. STRAIGHT FACE (Diagram C ),. 1• '.. :;; ;' >' • Face pattern available' for esthetic conslderat on. • Straight side and face cap units provIde .beautiful' uIts ;when` . building residential steps with KeyStone unitsi'` =:... r;'t'. • • setback units. The elongated tall section provides additional stability for atralght walls as the tall piece rests on the unit below It. GROOVES Remove the extended tail pieces at the grooves to re- turn the block shape to Its 30° sides when building tight con/ex curves. i•1, i (,Co' ,, i1.`ry•l. fir. t;.Ut;, 7.1 R F. • ,. �022781KEY ''BuyLine 2802 • DESIGN CRITERIA • GENERAL CONCEPT: The theory for gravity wall systems has been utilized since the building of the pyramids and rubble stone type walls. Through gravity weight and friction resistance based on material shape, the primary principal Is to resist lateral earth pressure which develops sliding and over- turning failure potential. The KeyStone Retaining Wall System Is a gravity retaining wall that utilizes Its' weight and deep embedment shape•[3:1 depth to height ratio] to resist lateral earth pressure. The mortarless, pinned connec- tion of units allows for a structurally in• teriocked network while providing free drainage of the hydrostatic loads behind the wall units. • NON-CRITICAL vs CRITICAL WALLS: For low, noncritical applications; the KeyStone Retaining Wall can be used ef- fectively for gravity wall [non- geogr4ded] structures to the following heights: Recommended Maximum Wall Heights [w /o Soil Reinforcement.] STANDARD UNITS 6' -0" COMPAC UNITS 3' -0" MINI UNITS 3' —O" STANDARD & MINI COMBO 5' —O" [Use 4" shims at tails of Standards.] COMPAC & MINI COMBO 3' -0" Assumed Parameters For Walls Indicated Above: BASE SOIL Minimum 2500 psf bearing capacity. [Sandy gravel.] RETAINED SOIL Approximately 32° fric- tion angle. [Sandy gravel.] SURCHARGE No additional surcharge. [Le., Slopes, structures, roadways, etc.] DRAINAGE Site run -off diverted, water table fluctuation or embankment drain- age properly considered. For taller, more critical applications, the combination of KeyStone wall units and geogrid soil reinforcement allow for larger' gravity wall structures capable of walls over 40 feet high. [Refer to GEOGRID CRITERIA.] NOTE: If your project Involves one or more of the following... •SLOPING BACKFILL [steeper than 1 to • 4]; •SURCHARGE LOADS; •HIGH GROUNDWATER TABLE; • MULTIPLE TIERS; • WALL BUILT ON SLOPE; • LOW SOIL SHEAR STRENGTH < 25 °; ...consider it a Critical Structure. Contact your KeyStone Representative for assistance. • WATER APPLICATIONS: • • KeyStone can effectively be used In water 9; , situations such as ponds, creeks, lakes ' ',:�,. • rivers and run -off channels. Evaluation of,•. ,j,y water level conditions, flow velocity, backfill soil type and foundation soils are5 very important. If a free draining system Is maintained with KeyStone wall tunits ;: , and backfill soils [1.e,, crushed rock] the • main Item of consideration Is foundation;] soil and wall base protection. Ways ac.��j tion and scouring effects should be evai =+: uated by a qualified hydrological tengl; neer. Critical applications may reqGuire.•; • ca erosion resistant footing design and rips'' rap protection. Consult your KeyStone`. ;' Representative for further details. `i• ..' • CURVES: • Building curves IntoyourKeyStone wall requires a •few., epeclal,nconslderatlons. Convex curves. .requlreYa' small gap be- tween adjacent :units [see diagram). For concave curves ;touching edge of each unit should be slightly'overiapped [see diagram]. Gapping and overlapping will vary somewhat with the .degree of cur - vature desired: A general guideline Is as follows: At the base course, set units with gap or overlap so pins of adjoining . units' are 12 "apart see diagram). ' r••' fat Jar CONCAVE CURVES;.:: .. 4• • • • CREATIVE OPTIONS: -' =,i r: *Combination of module sizes [Le., sizes 8 "- 4 " -8 ", and any combination thereof]. • Combination•of factory: or 'Custom pro- duct colors,'geometri• patterns,:horizon- tat bands, etc.f) AI ; ;•:; W :. • • Face texture combinations [rockface and corduroy]; ":4 .: • SPECIALTIES '• ;k ;:;tip c •r'f '` •Guard Rails; Highway' Barriers, Fences, Etc.: (Vertical posts of steel, wood, con- crete can be placed within the KeyStone retaining wall structure.] _ • 90° Corners: (Inside and outside.] •Sound Barriers: [Double wallwith''gravel core 1111.] eT:'.:•:' .,,:. ;�,.r'.j;�yr:; .,, . :J •Steps: [KeyStone units,astread /riser.] *Water Applications.:':': ,1 � 4 \ /`. Illiti;r7.....thk, 114" , 11 11 'tt , \ st y ' 1. ��,��1 it 4-u � , � .fi # A 1401;:- � G ' 444t17r r : f ill �� _�/ • BASIC PRODUCT tSTALLATIO t1..ii,. _:,t.Vr'' €>, '''•,- The KeyStone Retaining.W all System was developedtwith simplicity of construction in mind. 4 The following steps will guide you from start'.to°fInlsh. • STEP 1: PREPARATION OF BASE LEVELING PAD Excavate a shallow trench to the designed length and width dimensions for your KeyStone wall, Provide space behind the KeyStone unit to allow for a granular backflli drainage zone. KeyStone units should be placed on a 8' leveling pad of com- pacted, well draining granular fill [I.e., sand, 1/2" to 3/4. ",•crushed atone or gravel] at 95% Std. Proctor compaction or equal. Provide additlonal.trench.depth for below grade placement of KeyStone units on a ratio of 1.',.• below grade for each 8' of wall height above grade , „,.,,,.;.1*:(;: , fl'ot.V.;'f+ NOTE: When constructing walla less than 3' high, KeyStone unit. can be plaoad on.firfn undisturbed, Inorganic soils, Drainage zone may vary due to site, soli or engineering requirement ;;t • 'r.z,.: � ;a:i ,, . ‘I . at..'t yr ,. Y,• r,•. • STEP 2: INSTALLING THE BASE COURSE • .,,v,'; /4 ,. t ' - c ..r,, Install the first course of Keystone units side by side over the prepared base. Level each unit side to side and front to back. Place the units such that the kidney shaped void Is on the bottom surface.. Line up pins or back edge of unit .for straight wall alignment. Units should touch side point to side polnt'as diagrammed For layout and alignment of curves see information under DESIGN GUIDELINES (page•3). • STEP 3: INSTALLING THE INTERLOCKING PINS •?t: ":54? Place the reinforced fiberglass pins Into the paired holes In each Keystone unit. Provide pins of correct length for appropriate unit size. Once In place, the pins will allow an automatic setback when Installing additional courses as per STEP 5. • STEP 4: INSTALLING BACKFILL & COMPACTION °' Fill all voids in and between KeyStone units and behind. units. This fill should con- sist of 1/2" to 3/4” crushed stone or clean, well draining granular fill. This allows for water drainage and compacts easily. Compact to eliminate potential settlement. Backflll behind gravel drainage zone using existing soils. (NOTE: Heavy'clays or organic soils are not recommended due to water holding properties.] Compact to 95% Std. Proctor. Backflll In 8" lifts on a course by course basis: [NOTE: Only lightweight walk behind mechanical compaction equipm nt should be used,wtthln 3' of the back of the units•] . •#? F 1.0;4;'J:.::. ^ :, ':` e.; ° Upon completion of backflll and compaction, SWEEP the units to remove small pebbles, debris, etc. so the units rest evenly upon one another. Backflll and compact at every 8" course, F 1' .)Yt c' • , • STEP 5: INSTALLING ADDITIONAL COURSES ' : ;?s;r =;' ' >rs; • • Place the next course of KeyStone units over the positioned fiberglass pins so It Is centered on and bridges two units below in a running bond pattern. Pins should fit in- to kidney shaped recesses on bottom of unit. Pull the KeyStone module towards the face of the wall until the module•makes full contact with both pins. Repeat STEPS 3, 4 and 5. ■ STEP 6: INSTALLING KEYSTONE CAPS ;.c':' , . . Use KeyStone Cap units to complete your wall. Place the Keystone Cap over pro- Jecting pins on the unit below. Pull forward to the automatic set back position. Backflll and compact to finish grade. [NOTE: In areas of high public accessibility and vandalism, we recommend a construction adhesive or epoxy cement be used around the perimeter underside of the cap prior to unit placement.]. :, ; , :' . ,,,• c .; The above installation guidelines apply to-all KeyStone unit sizes. These Installation procedures do not take Into account geological variations In alts and soli conditions and therefore may require further engineering con- sideration and detail. None of the Information enclosed herein should be construed sere construotlon detail. GEOGRID INSTALLATION : (PATN RACE D. D RES)'•• For taller more critical walls, where geogrid is req Ir let, rea a ateral earth pressures, use the following steps for instailation.£0 `• k , • STEP 1: Follow steps 1 -4 on PRODUCT IN STEP,5:. .y o' retension'geogrid ppull INSTALLATION. pinned geog taut to eliminate loose folds. • STEP 2: Excavate the reinforced , soil Stake or secure back edge of geogrid prior area to the maximum embedment length. ; . to and during backflli and compaction. • STEP 8: Install next Course C,f KeyStofle • STEP 3: Cut sections of geog'fld oft roll TNT 4 y < retaining wall unite..: , �i ��4 �.; to the specified length. Place gpogrld in : STEP 7: :Proceed':to�'placi. compacted proper orientation. [/,e. roll out from wail to- backf III over geogrid In 8" lifts. Provide mini- wards embankmentl. Check man' facturers ' mum 8" soil coverage prior to driving equip - criteria for biaxial or uniaxial geb�grids. ment over • "grid Avold tracked orwheeled • STEP 4:• • • Hook geogrid over eystone • vehicles directly on grid, or turning on grid. fiberglass pins, assuring a secur� connec- • STEP 8: Continue Steps 3�7,untll retain• tion between unit and geogrid, f' Ing wall Is complete: • x:: .:;t; ;; . ; CASE B. SURCHARGE 250 psf CASE C. SLOPE GEOGRID CRITERIA • GENERAL CONCEPT • The structural principle of reinforced soil retaining walls Is quite simple. By com- bining KeyStone concrete wall units, geo- grid reinforcement and compacted soils over the geogrid, a reinforced soil mass Is created to resist calculated destablizing forces from lateral earth pressure and sur- charge loads. Essentially this composite forms a larger gravity wall structure. • GEOGRID REINFORCEMENT Geogrids are manufactured synthetic products of high density polyethylene or polyester materials, formed or woven into a grid like open pattern. With high strength, high modulus features, geogrids are effec- tively used in horizontal layers to create a tensile capacity for shear resistance within the reinforced soli mass. • ADVANTAGES 1.Economic benefits due to utilizing ex- isting site soils In most cases. Saves on balancing of cut and fill sites and ern- . inates need for select Imported •backflll soil. 2.Wa11 builds up at rate of backflll and compaction process. No waiting on shop drawings, forms, steel, or for concrete to reach cure strength prior to removing forms and installing backfill. ''' 3.Safer construction due to wall and back- fill proceeding up together. No backfllling behind formed wall and embankment. 4.Flexibie vs Rigid System - allows wall to handle differential settlement due to frost, soil consolidation, etc. Distributes weight of structure uniformly over larger area. Avoids localized overstress of foun- dation soils. Walls can be built without structural footing or base frost protection. 5.Geogrids are synthetic materials not af- fected by external factors evident In soils, [/.e. water, micro - organisms, alkali or acid soils). 7 • DESIGN METHODOLOGY In evaluating the design for a gravity type geogrid reinforced soli retaining wall, the design engineer analyzes the following criteria: •SOIL PROPERTIES — Determine„repre- sentative shear strength parameters [an- gle of internal friction] and moist unit weight for each soil zone. Foundation Soil /Retained Embankment Soii /Rein- forced Backfill /Core and Drainage Fili. NOTE: Values for cohesion in soil are not utilized in structural analysis. Qualified Geotechnical Engineer should determine soil properties. •EVALUATE EXTERNAL STABILITY — The four standard modes of failure for ex- ternal stability should be addressed. Slid- ing [1.5 F.S.), Overturning [2.0 F.S.), Bear- ing Capacity [2.0 F.S.] and Global Stabil- ity [F.S. to be determined by qualified Engineer]. •EVALUATE INTERNAL STABILITY — In order for the Engineer to address the three modes of internal stability, [Pullout, Tensile Overstress and Localized Stress Between Grid Layers], specific geogrid manufacturer material properties must be known. •Long term allowable design strength. •Tensile modulus at low strain levels. •Service life. •Ability to interlock with soil. . Actual design methods, criteria and end$e'ering analysis are beyond the scope of thle document. Con. , cult your KeyStone Representative for ;specific geogrid engineering analysis, design strengths and product availability. Design of geogrid soli relhforced walls should be specifically analyzed by a qualified engineer. 3i: 022781KEY BuyLlne•2802 • • GEOGRID QUANTITY. ,- Geogrid quantity,'H em bed men t length [L], horizontal layer frequency and place- ment elevation are Increased as loading conditions exerting forces on the reinforced soil zone are affected by the following: • Wall height /embankment height [H] •Geogrid strength properties • Shear strength of soli • Hydrostatic loads • •Surcharge and slopes [See CASES A -DJ k; ; ;.,. ■ CASE A. BASIC WALL'WJTHOUT SUR- CHARG c;,t;af„ Level grade attop'of wall "wlth•no sur- charge or slope creating additional thrust. • CASE B. CON T NNT�StjRCHARGg LOAD -g � �6 tz r4•L:'H: Auto parking ote, trucktraffic, buildings or structures affect the geogrid design by Increasing the Toad condition on•the rein- forced soil mass.-' • CASE C. SLOPING' HILLSIDE SUR -:: CHARGE . ;.:�;r `:nlv •,:.ri�et6 ;�� 1 Steeper, longer ''slopes' place greater loads on retaining wall, than CASE B. loads In most situations. Greater the degree of slope = increased geogrid quantities. • CASE D. TIERED WALLS Tiered walls must be carefully evalu- ated. Closely spaced tier walls can create higher stresses on the lower wall section than an equivalent full height wall. Design- er must determine the pressures exerted by the higher wall tier on the lower wall when [I-1 Z 2L].i ,;J k.; :: :f.. . • • IMMO NEIN r . • DRAINAGE CONSIDERATIONS: Most retaining wall failures are caused by poor drainage leading to the accumula- tion of hydrostatic pressure which causes a destabilizing force In the reinforced soil mass. Proper design and engineering should consider provision for external and internal drainage to protect the entire retaining wall structure. See DRAINAGE DIAGRAM for locations of drainage provisions. Location 1, BASIC WALL, DRAINAGE KeyStone wall naturally-drains due to . mortarless yet'! Interlocked' system and drainage zone. No weep holes needed. Location 2. SURFACE RUN -OFF 4: ' Provide plastic (clay] soil cap or formed , swale [soli or concrete] to divert surface drainage. Redirect surface drainage by site '• design where possible. • ;i >•; a4 Locaatlon 3. EMOAI� KMENT FLOW.' Use chimney ran system with outflow pipe at base of embankment to eliminate water flow Into reinforced soil zone. . Location . ROUND WATER FLOW rising Effects ground' water can be . offset by usingp; kground blanket drain' zone and outflow; pipe beneath, leveling pad and reinforced soil zone.::;.. • KEY NETM 6 SPECIFICATION GUIDELINES :. -• KEYSTONE CONCRETE MODULAR,RE .AININQ,WALL:~ SECTION 02276 • PART 1: GENERAL j. 1.01 DESCRIPTION A. Work Includes furnishing and Installing modular block retaining wall unite to the lines and grades designated on the construction drawings and as specified herein. B. Work Includes preparing foundation soil, fur- nishing and Installing leveling pad, unit fill and backflli to the lines and grades designated on the construction drawings, C. Furnishing and Installing all appurtenant mate- rials required for construction of the retaining wall as shown on the construction drawings. 1.02 RELATED WORK A. Section 02275 — Geogrld Soil Reinforcement. 1.03 REFERENCE STANDARDS A. ASTM C90 -85 Hollow Load Bearing Masonry Units. B. ASTM C140 -75 Sampling and Testing Con- crete Masonry Units. C. ASTM C145 -85 Solid Load Bearing Concrete Masonry Units. 1.04 DELIVERY, STORAGE AND HANDLING A. Contractor shall check the materials upon delivery to assure that proper material has been received. B. Contractor shall prevent excessive mud, wet ce- ment, epoxy, and like materials which may affix themselves, from coming In contact with the materials. C. Contractor shall protect the materials from damage. Damaged material shall not be Incor- porated Into the retaining wall structure. 1.05 SUBMITTALS A. Samples of all products used In the work of this section. B. Latest edition of manufacturers spcclllcatlons for proposed materiels, method of installation and Ilst of material proposed for ute. 1.06 OUALITY ASSURANCE A. Soil testing and Inspection service for quality control testing during earthwork operations will be supplied by the owner. • PART 2: PRODUCTS 2.01 CONCRETE UNITS A. Masonry units shall be KeyStonee Retaining Wall Units as manufactured by' B. Concrete wall units shall have a minimum net 28 day compressive strength of 3000 pal. The con- crete shall have a maximum moisture absorption of 6 to 8 IbslfN. C. Exterior dimensions may vary In -accordance with ASTM C90 -85. Standard and Compac units shall have a minimum of 1 square loot face area each. Mini units shall have a minimum 112 square foot face area each. D. KayStone Standard units shall provide a mini- mum of 150 psf of wall lace area. Fill which is contained within the dimensions Of the unite may be considered as 80% effective weight. E. Units shall have angled sides capable of con- cave and convex alignment curVes with a minimum radius of 3.5 feet, NOTE: Where applicable, for straight walls use non - angled straight side cap units.:, F. Units shall be Interlocked with non - corrosive fiberglass pins, ,I G. Units shall be Interlocked as 10 provide a mini- mum 114 Inch setback per each course of wall height. NOTE: Where applicable, zero setback or one Inch setback per course options can be used. 2.02 FIBERGLASS CONNECTING PINS A. Connecting pins shall be 112 Inch diameter ther- moset Isoplhallc polyester reeinlpultruded fiberglass reinforcement rods. B. Pins shall have a minimum flexural strength of 128,000 psi and short beam shear of 6400 pal. 2.03 BASE LEVELING PAD MATERIAL A. Material shall consist of compacted sand, gravel, crushed rock or leveling concrete (non- reinforced) as shown on construction drawing. The compacted leveling pad shall be a minimum 8 Inches thick, When using • non-reinforced leveling concrete option, 1" to 3" thick, maintain the total leveling pad thickness. i• 2.04 UNIT FILL • A. FIII for units shall be free draining crushed stone, 3l8" to 3/4', or coarse gravel (no more than 5% shall pass the No. 200 siev with a max- Imum size of 3/41. Gradation of th 1111 shall be approved by the Engineer. 6. Place recommended 1111 behind the retaining well unite, ' 2.05 BACKFILL,):.'r+•' ij4:, A. Material shall be Ineltu soils when approved by • the engineer unless otherwlse specified In the drawings: Unsuitable 'tolls for backlit' (heavy clays or organio soils) shall not be used In the backflli or In the reinforced loll mass. B. Where additional fill Is required contractor shall submit sample and specifications to the engl- ..: nNr to dettermine,lf acceptable. '''t .'�rkiJt�'61 i.' V,l.:13,C: 1 1: . •.' • • PART 3; EXECUTIONS *, ;°'' 3.01 EXCAVATION.'; �k�, :t • ;` A. Contractor. 'Shall.excavate "to the 1Ines end grades shown on the construction drawings. Over excavation shall not be paid for and replacement with compacted 1111 and/or wall ' system components will be required at contrac- tor expense. Contractor shall be careful not to . disturb embankment •, materials beyond lines :• : • 3.02 FOUNDATION 5011. PREPARATION ; • A. Foundation soil shall be excavated as required • for footing dimensions shown on the construc- tlon drawings, or as directed by the Engineer. B. Foundation . soil shall be examined by the Engineer to assure that the actual foundation soli strength meets or exceeds assumed design strength. Solis not meeting required strength shall be removed and replaced with acceptable material. . C. Over-excavated areas shall be lilted with ap- proved compacted backlit' material. 3.03 BASE LEVELING PAD • ' A. Leveling pad materials shall be placed as shown on the construction drawings, upon undisturbed Ineltu soils, to • minimum thickness of 6 Inches. B. Material shall be compacted so as to provide a . level hard surface on which to place the first course of units: Compaction shall be to 95% of 'standard proctor for sand or gravel type mate- ,. =dais. For crushed rook, material shall be densely compacted.' .._ .. C. Leveling pad shall be prepared to insure com- plete contact of retaining wall unit with base. D. Leveling pad materials shall be to the depths and widths shown. Contractor may opt for using • • reduced depth of sands, gravel or crushed rock using • concrete topping. Concrete shall be un- ° reinforced and a maximum of 1' to 3' thick. 3.04 UNIT INSTALLATION A. Flret course of concrete wall units shall be placed on the bass leveling pad. The units shall be checked for level and alignment. The first course Is the most Important to Insure accurate and acceptable results. • B. Insure that units are In full contact with bane. C. Units are placed side by side for full length of wall alignment. Alignment may be done by means of • string line or offset from base line. D. Install fiberglass connecting pins and 1111 all voids at units with unit fill material. Tamp MI. E. Sweep all excess material from top of units and •. Install next course. Insure each course Is come pletely'unit filled, backfllled and compacted • prior 10 proceeding to next course.. • F. Lay up each course Insuring that pins protrude Into adjoining courses above* minimum of one Inch. Two pins are required per unit. Pull each unit forward, away from the embankment, ' ' against pin..ln the previous course and backlit' as the course Is completed. Repeat procedure to the extant of wall height. G. As appropriate .where the wall changes slava- tlon, units can be stepped with grade or turned Into the embankment with a convex return end. '-'-'Provide appropriate burled units on compacted leveling pad In area ofa0flvex return 3.05 CAP INSTALLATION 'f�t!?4''��i�" A. Place Key8to• Cap' units over projecting pins • . from units below. Pull forward to Set back post- lion. Back 1111 and compact to finished grade. B. As required, provide permanent mechanical con - ;•i nation to wall units with construction adhesive , or epoxy. Apply adhesive or epoxy to bottom sure face of cap unite and Install on units below. 3.06 GEOGRID INSTALLATION ' �,'• 4: A. Follow the requIrementa' of Section 02275, • ' GEOGRID SOIL REINFORCEMENT. I. TYPICAL WALL SECTION TERMS MINIMUM AUTON/ TITTh SETBACK 'A • PER COURSE KEYSTONE'. CAP UNIT 491.11111N.LOWD. 2 TOPSOIL niii-,.. 1 UMW , / .r- 1 , fl'HAIVW.124 'D. KEYS ONE'. 411/611111 STANDARD UNIT re um =.1...1 OPSOIL Mal ram 11 1141 II ••••:•*111.11.?. 1111111111111 Vat,t4"TET ) !an ••••..• ...... .•. MA ES .,b , ." :. t I ' , ./.9., . V4ii"lq1411f'0 i I, COMPACTED REINFORCED BACKFILL ZONE RETAINED BACKFILL • ;, Y., CRITICAL FAILURE PLANES BEING ANALYZED GEOGRID ATTACHED TO FIBER GLASS PINS AT UNIT DRAINING GRANULAR COMPACTED BASE AND BACKFILL FOUNDATION SOIL 0.1 •i SPECIFICATION GUIDELINES GEOGRID SOIL REINFORCEM SECTION 02275 • PART 1: GENERAL 1.01 DESCRIPTION A. Work Includes f urnishing and installing geogrld reinforcement, wall fill, and backfill to the linos and grades designated on the;con• struction drawings. B. Work Includes furnishing and Inetalling all appurtenant materials required for construe. lion of the world reinforced soil retaining wall as shown on the construction drawings. 1.02 RELATED WORK A. Section 02276 KEYSTONE CONCRETE MODULAR RETAINING WALL, 1.03 REFERENCE STANDARDS A. See specific geogrld manufacturers reference standards. 1.04 DELIVERY, STORAGE AND HANDLING A. Contractor shall check the geogrld upon delivery to assure that the proper material has boon received. B. Googrids shall be stored above —20.F. C. Contractor shall prevent excessive mud, wet cement, epoxy and like materials which may affix themselves to the pridwork, Irom coming In contact wlth the geogrld material. D. Rolled geogrld material may be laid flat or stood on end for storage. 1.06 SUBMITTALS A. Samples of all products used In the work of this section. B. Latest edition ol manufacturers specifIca. tions for proposed materials, method of In• sit:illation and list of material proposed for use. 1.08 QUALITY ASSURANCE A. Soil testing and Inspection services for quality control testing during earthwork operation will bo supplied by the owner. • PART 2 PRODUCTS 2.01 DEFINITIONS A. Geogrid products shall be high density polyethylene expanded aheet or polyester woven fiber materials, specifically fabricated for use as 8011 reinforcement. B. Concrete retaining wall units are as detailed on the drawings and are specified under Section: 02276 KEYSTONE CONCRETE MODULAR RETAINING WALL. C. Wall fill Is a free draining granular material used within the concrete units. D. Backfill Is the soil which Is used as fill for the reinforced soli mass. E. Foundation soll Is the InsItu soli. 2.02 GEOGRID A. Geogrld shall be the type as shown on the drawings having the property requirements as described within the manufacturers apecitica• ' lions. 2.03 ACCEPTABLE MANUFACTURERS A. A manufacturer's product shall be approVed by the Engineer prior to bld opening. • SPECIAL CONSIDERATIONS: •Geogrid can be interrupted by periodic penetration of column, pier or footing structures. •Alternatives when site conditions will not allow geogrld embedment length. 1.KeyStone can be designed and built as a reinforced masonry unit wall. :„ , • Cores will accept vertical reinforcing ,,•:;; and grout. 2.Deadman - tie back anchor option.'•:: Reduces or eliminates excavation and backfill requirements. a Increased wall batter by sloping level- ing pad or footing. V.e. 8 to 1, 4 to 1 etc.] Consult your KeyStone Representative for details. ENT • . •• • PART 3: EXECUTION 3.01 FOUNDATION SOIL PREPARATION A. Foundation soil shall be excavated to the lines and grades as shown on the construe. Don drawly or Se directed by the Engineer. B. Foundation 4011'0811 be examined by the Engineer to assure that the actual foundation deoesiligsntrietnrepth 9gthmill of !timed C. Over-excavated areas shall be Riled with al> proved compacted inapt material. D. Foundation soil shall be proof roiled prior to fill and geogrld placement 3.02 WALL ERECTION A. Wall erection shall be ss Specified under Sec. lion: 02278 KEYSTONE CONCRETE MODULAR RETAINING WALL 3.03 GEOGRID INSTALLATION; A. The geogrld soli reinforcement shall be laid horizontally on compacted backfill. Connect to the concrete wail units by hooking googrid over fiberglass pins. Pull taut, and anchor before backfill is placed on the (world. B. Slack In the geogrld at the Wail unit connec- tions shall be removed. )t.0,;14 C. Geogrld shall be told at the proper elevation and orientation as shown on the construction drawings or, as directed by the Engineer. D. Correct orientation (roll direction) of the geogrld shall be verified by the contractor. E. To pretension world, pull pinned geogrld taut to eliminate loose folds. Stake or secure back edge of geogrld prior to and during backlitl and compaction. F. Follow manufacturers guidelines relative to overlap requirements of unlaxlal and biaxial geogride, 3.04 FILL PLACEMENT • A. Backlitl material shall be placed In 8 inch lifts and compacted to 951/4 of Standard Proctor. B. Backlit' shall be placed, spread, and corn- pacted In such a manner that minimizes the development of slack or loss of pretension of the geogrld. C. Only hand-operafed compaction equipment shall be allowed within 3 feet of the back aur. face of the KeyStone units. • D. Backlit] shall be placed Irom the wall rearward into the embankment . to Insure that the geogrld remains taut , E. Tracked construction equipment shall not be operated directly on the geogrid. A minimum backlit] thickness of 6 inches le required prlor to operation of tracked vehicles over the geogrld. Turning of tracked vehicioe should be kept to a minimum to prevent tracks from displacing the fill and damaging the ;world. F. Rubber-tired equipment may pass over the geogrld reinforcement at slow simedit leas than 10 MPH. Sudden braking and sharp turn- , Ing shall be avoided. . •!‘ s, '241,1tr;v;-11.- 7 R • ifftgie' ,,KERY STAN' •• For fie.' backslope, surface should be impervious & sloped to drain. ' I to2 • rot . 2 for flatterr;`,.1;T;, • I I .." 6. ' , +. e , . Free-drainingbackfill.,i''im'ax.'5% fine min 13 wide,' layer-olt(2 eluarrY ". 4 21'4.V.tt, ;).y dog .s , • • :palls cidlocen09focker Stable iitfac�. .n i�tIv�. • ••• _ „„-•,. 4, el 1/4 material Aselel01V...i'v • plax ;.(me--See Notes 1-3 for permit a certification . requirements. , 1 • I • . min 12." tt washedgroveli p t. 1 ‘,. it. ji • Flynt,. Undisturbed soil • • Min. 4" dim. perf. pipe; min. 1% continuous slope to outlet; pipe flior cut face lined with filter fabric (Miran or equivalent). _,.„qT45,40osoostomWo0.41.4100140 0 o(JeAr Rockeries 4' irt-hci-ght ‘.. r‘rockeries between 4' and 6' high, staller or contractor shall letter to the building is.,to final inspeCtion ubgrade and accord GENERAL NdTES prov; _ inspector p certifying that t drainage have been preps with these standards. .111sc4eries 6' and over in height require ing supervision by special 306b), which at minimum ection and written acement of • env. inspector • shall consist o certification of subgra • base course and drainage, and 1-.1 • rockery. •Rock'shall be sound.and have minimum rnderisity of. 160 pounds per cubic foot. The 1png dimension of all rocks shall be placed perpendicular to the wall. Each rock ,should bear on two rocks in • theLtier • • • 6 Improved walking'sUi44Wabovtan4..ad- jacent to zooke4,41,044,rOggurheight shall be protecteoWle ' rdrail. .. ; e.,. , . conforming.to.UBgr 7. Rockeries-are eroqlor• not`.retaining*aLl must be stablein cut face: 'i ' :'4,4-40. 4 ,ell, - .0 1 .,...'}N • 'I. 04 v ' $ , ' ' * 8. Any. deyiationiqn*iskorlg ' lacement oradjacent structureOst iubmit te&with:these41;414,1,430 Angineer currentlY'liceaeC 'qhel.Tsiqteof , Washinzton. ,-,ITC ' ii' 4't 4 , 4 ,..4, • mop ./,,, ... v.... t . OJOKIIFtl.wes' ai ong .144, RCN ITECTS CHARLES MORGAN 8( ASSOCIATES 7301 BEVERLY LANE EVERETT, WA. 98203 Phone (206) 353.2888 March 15, 1993 Ms. Denni Shefrin, Associate Planner Department of Community Development City of Tukwila 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 Re: Fosterview Estates (L92 -0065 and L92 -0066) Dear Denni: Enclosed you will find 10 copies of the drawings that we are submitting for the preliminary subdivision application. We were not able to get all the required information needed on one sheet and still be able to read it, so we have broken it down into 8 pages. Sheet 1 - Shows the existing and proposed contour lines, the lot size, lot dimensions, legal description and tract area. Sheet 2 - Shows the existing property lines within 300 feet of our property, the street light locations and detail, the street sign location and the vicinity map. Sheet 3 - Shows the street layout and grading. Sheet 4 - Shows the drainage basin analysis. Sheet 5 - Shows the utility plan, sewer layout for alternative #1. Sheet 6 - Shows the utility plan, sewer layout for alternative #2. Sheet 7 - Shows the existing rees to be retained, the tree canopy calculations and landscaping. Sheet 7a - Shows the exising trees. Also.included are 3 copies of the stamped geotechnical analysis of 44th Av. South and the hydrology analysis for the project. Sincerely, JA n M. Bates cc: Bill Fowler LICEN3ED: 0 �tWASHINGTON • OREGON • CALIFORNIA • IDAHO • UTAH • ARIZONA • MONTANA WYOMING • COLORADO • NEW MEXICO • NEBRASKA • NEVADA RIT ARCHITECTS r HAR LES MO CHARLES MORGAN 8c ASSOCIATES 7301 BEVERLY LANE EVERETT, WA. 98203 Phone (206) 353-2888 Lot Number Lot Size Mean Width Mean Depth #1 10,918 sq.ft. 64' -1" 56' -0" 9 4,012 37' -11" 78' -1" 3 6,634 47' -11" 104' -10" 4 6,137 76' -11" 61' -0" 5 5,033 49' -4" 120' -S" 6 3,997 35' -4" 112' -2" 7 3,810 35' -4" 107' -6" 8 3,833 35' -3" 107' -6" 9 3,471 30' -7" 112' -5" 10 3,473 '29' -11" 110' -8" 11 5,136 101' -6" 45' -0" 12 4,663 70' -10" 69' -2" 13 7,772 52' -5" 121' -1" 14 5,733 51' -5" 91' -9" 15 6,407 .43' -11" 88' -4" 16 5,546 49' -11" 101' -0" 17 5,010 46' -10" 100' -2" 18 7,241 52' -O" 127' -6" 19 '13,152 59' -6" 198' -0" 20 10,751 37' -2" 212' -7" 21 5,224 53' -7" 821-2" 22 7,446 69' -7" 119' -6" 23 5,421 49' -3" 108' -7" 24 4,984 60' -9" 82' -4" 25 4,657 54' -6" 91' -8" 26 4,525 53' -4" 83' -2" 27 4,293 52' -4" 81' -8" 28 3,949 47' -R" 89' -4" 29 5,966 45' -8" 113' -3" 30 8,191 52' -10" 133' -7" 31 7,742 51' -2" 126' -2" 32 7,119 60' -6" 123' -7" 33 6,109 48' -6" 125' -2" 34 6,270 47' -2" 132' -0" 35 6,840 55' -0" 124' -5" 36 6,764 41' -4" 151' -8" 37 6,033 48' -3" 121' -4" 38 5,875 56' -10" 103' -5" 39 4,211 51' -6" 79' -6" 40 3,831 48' -0" 81'- 1 "_., 41 3,825 45' -8" 83',-.92'.. LICENSED:. WASHINGTON • OREGON • CALIFORNIA • IDAHO • UTAH • ARIZONA • MONTANA WYOMING • COLORADO • NEW MEXICO • NEBRASKA • NEVADA ACHARLES MORGAN 8. ASSOCIATES RCN ITECTS E? 1 r Z • 7301 BEVERLY LANE EVERETT, WA. 98203 March 8, 1993 Ms. Denni Shefrin,:Associate Planner Department of Community Development City of Tukwila 6300 Southcenter Blvd. Suite 100 Tukwila, WA 98188 Re: Fosterview Estates (L92 -0065 and L92 -0066) Dear Denni: Phone (206) 353 -2888 We were unable to submit the subdivision application and the additional items requested in your letter of February 12, 1993, on March 5, 1993 as originally set up for the following reasons: 1. You have said that you didn't want to address the unresolved house layout situation until the drainage issues have been resolved. The house layout issue directly impacts the hydrology analysis, in that, the impervious surface calculations are based partly on the footprint of the house, driveway and walkway layouts. Due to the fact that this issue still is unresolved, we had to determine that the site plan would stay as it was so that we had a base map to start with. It is on this site plan that the landscaper, Erich Tietze and I have based all of our calculations. 2. It has taken Erich Tietze longer than originally anticipated to complete his work due to the fact that he is still doing everything based on the two alternatives for sewer and drainage. The landscaper and I have had to do our work also based on these two alternatives. We are requesting an appointment to submit the additional items requested, the tree ordinance plan, landscaping plan and the subdivision application on Monday, March 15 at 1 :30 P.M. If you have any questions, please call me at 353 -2888. n M. Bates : Bill' Fowler Amy Kosterlitz LICENSED: WASHINGTON • OREGON • CALIFORNIA • IDAHO • UTAH • ARIZONA • MONTANA WYOMING • COLORADO • NEW MEXICO • NEBRASKA • NEVADA City of Tukwila John W. Rants, Mayor Department of Community Development Rick Beeler, Director February 12, 1993 Mr. Bill Fowler Dujardin Development Company 9623 32nd Street S.E. Everett, WA 98205 Subject: Fosterview Estates (L92 -0065 and L92 -0066) Dear Bill: Background Due to the natural constraints of the site, and at your request, the City agreed in June of 1992, to accept a PRD application prior to submittal of the subdivision preliminary plat. Proposed street alignments, access, wetlands, watercourses and associated buffer delineations have been generally accepted by the City Department of Public Works and the Planning Division. A SEPA Checklist was originally submitted October 8, 1991, and revised August 13, 1992, to respond to the PRD proposal. Issues yet to be resolved include the surface water analysis, soils (geotech) analysis, utilities plan, PRD and subdivision items. This letter is broken into our sections: surface water, geotechnical, utilities and subdivision. Each section specifies additional information necessary for the City to complete its review. I. Surface Water a. Provide an engineering analysis which discusses the relocation for surface water detention and biofittration to 44th Av. S. b. Address whether there will be an increase of groundwater or surface water runoff to the downhill properties north of the site resulting from the development. c. Discuss whether peak flows of the creek will be increased. d. Indicate whether the wetland north of the site (Poirot's property) will be affected. Identified impacts to wetlands may result in an environmental analysis. II. Geotechnical The City has requested a stamped geotechnical analysis of 44th Ave. S. The Department of Public Works' decision to forego further consideration of improving 44th Av. S north of S. 137th has been based on discussions in the PRD meetings. Dujardin representatives in those meetings stated that the geotechnical analysis suggests these areas are unstalbe, but the study only discusses the extreme cost to correct the unstable condition. The City is aware of the existing sloughage and agrees with the identified causes of instability and the costs for correction. However, the City still must have additional geotechnical analyses to determine whether corrections are appropriate. The ravine stability mitigation measures to prevent over - scouring need to be defined with their limits within 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431-3665 the ravine. These are the measures discussed January 28, 1993, with Senior Engineer Phil Fraser, Urban Environmentalist Gary Schulz, and Terra & Associates geotechnical engineer, Anil Butail. III. Utilities a. Provide a utility plan for water, sewer and storm water. b. Identify the access road location which connects the park for sewer and storm needs c. Show easements d. The plan must show the cul -de- sac /right -of -way transfer IV. Subdivision A copy of the City of Tukwila Subdivision Code (Title 17, Subdivisions and Plats) and subdivision application is enclosed. Please be aware that the PRD application, although accepted by the City was not complete because no landscape plan was included with the submittal. The landscape plan is expected to be submitted along with the subdivision application. Conclusion On or about September 1992, the City confirmed that an Environmental Impact Statement would not be required, however, adequate information has not been provided to date in order for the City to make a SEPA determination, specifically the hydrological and geotechnical analysis. This analysis was originally requested July 7, 1991 at the pre - application meeting and was to accompany the SEPA checklist. While it is assumed that a Mitigated Determination of Nonsignificance will be issued for the project, the City cannot commit to a schedule related to an environmental determination. This determination must occur prior to consideration of the PRD /Subdivision application by the Planning Commission and City Council. I recognize that issues related to architectural design of the residences, home entries and lot orientation, driveway widths, and sensitive area tract delineatino have not been completely resolved. A draft homeowner's agreement should also be provided with the subdivision application. Please refer to the Subdivision Code. You should also be aware that the city requires that the tracts be 'held in common ownership by multiple owners who shall collectively be responsible for 'maintenance of the tract (Section 18.45.090 (b)(2). The agreement must make provisions for this arrangement. i The additional analyses and plans should be provided no later than February 24. Please notify as Concurrent with the City's review of the information identified above, I will schedule a meeting to discuss any unresolved issue related to the PRD and subdivision. Feel free to contact Phil Fraser or Gary Schulz if you have further questions or need clarification concerning items I -III above. They can be reached at 433 -1641 or 431 -3662 respectively. Questions related to the PRD or subdivision can be addressed to me directly. Sincerely, ! r5A» (1,9 !.•�j/N, f� tL cliatit �-(C Denni Shefrin (Y44; IL Ef7✓ 1);B. Associate Planner Ron Cameron Phil Fraser Gary . Schulz - Erich Tietze Anil Butail Terre Harris Jean Bates . Enclosures. Applied Geotechnology Inc. June 25, 1993 15,735.001 Ms. Denni Shefrin Associate Planner City of Tukwila Department of Community Development 6300 Southcenter Boulevard, Suite 100 . Tukwila, Washington 98188 Dear Ms. Shefrin: Followup Comments Geotechnical Review Meeting Proposed Fosterview Estates Development Tukwila, Washington This letter is to follow up and confirm what we see as the essence of our June 23, 1993 telephone conference meeting regarding Terra's response to your June 17, 1993 revi. %w comments on the proposed Fosterview development. • Applied Geoiechnology Inc. does not feel it is unreasonable for the City at some point in the design /permitting process to require the developer to perform numerical slope stability analyses to demonstrate that the proposed fills on slopes, as designed, are stable. • In view of the site slope stability concerns, we judge it appropriate for the City to require a written•commitment from the developer that Terra will be retained to review final design plans and monitor the geotechnical aspects of the construction. • We judge that it is also appropriate at this time for the City to require the developer to submit a conceptual erosion control plan describing, in general terms, what measures they anticipate will likely be necessary for the final site erosion control plan. Please call if you have any further questions. Sincerely, APPLIED GEOTECHNOLOGY INC. Garry H. Squires, P.E. Senior Engineer Donald E. Bruggers, P.E. Principal Engineer GHS /DEB /jlh P.O. Box 3885 ' Bellevue, WA 98009 FAX 206/646 -9523 • • JUN 2 8 1993 C UN ! ''i OE-VI1_OFMENT -.r Telephone 206/453-8383 Applied Geotechnology Inc. May 17, 1993 15,735.001 Ms. Denni Shefrin Associate Planner City of Tukwila Department of Community Development 6300 Southcenter Boulevard, Suite 100 Tukwila, Washington 98188 Dear Denni: Geotechnical Review Proposed Fosterview Estates Development Tukwila, Washington This letter presents the results of Applied Geotechnology Inc.'s (AGI) geotechnical review of the above - referenced proposed single - family residen- tial development. Our services were performed in accordance with our April 29, 1993 proposal. We received your written authorization to proceed on May 4, 1993. PURPOSE AND SCOPE OF' SERVICES The purpose of our services was to comment on the geotechnical.aspects of the proposed development based on review of relevant technical reports, development plans, and correspondence provided by the City of Tukwila (City). Our scope included the following specific items: ■ Item 1: Review the geotechnical reports by Terra & Associates and subsequent correspondence. ■ Item 2: Visit the site to observe existing conditions. ■ Item 3: Review the City's Sensitive Areas Ordinance (SAO) and the development proposal documents and provide our opinion on the following: - Determine whether the SAO requirements have been fully addressed. - Identify concerns, if any, which should be considered. - Judge the reports' adequacy relative to the proposed development. - Identify the need for additional technical study. ■ Item 4: Comment on geotechnical aspects related to planned lot density, proposed biofiltration swale locations, and potential for increased runoff onto adjacent properties to the north of the site. ■ Item 5: Provide our opinions and suggestions in a letter. P.O. Box 3885 Bellevue, WA 98009 FAX 206/646 -9523 Telephone 206/453.8383 "'." ZiTY Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 2 Applied Geotechnology Inc. The City provided geotechnical reports, correspondence, SAO, and development plans for our review. A specific list of documents provided is attached. UNDERSTANDING OF SITE CONDITIONS (SCOPE ITEMS 1 AND 2) Although we briefly reviewed all the referenced documents, we focused on the geotechnical reports and grading plans. The following paragraphs briefly summarize our understanding of existing site conditions and the proposed development based on our document review and May 7, 1993 site reconnaissance. The approximately 10 -acre undeveloped site is situated between 44th Avenue South and 42nd Avenue South. It is bounded to the north and south by Southgate Park and existing single - family residential lots. The intersection of existing South 137th Street and 44th Avenue South is approximately opposite the middle of the east property line. The portion of 44th Avenue South from opposite the northeast property corner to the intersection with South 137th Street is barricaded (abandoned) because of previous downslope landsliding of the existing roadway. The proposed development includes extending South 137th Street from the intersection with 44th Avenue South west across the site to connect with 42nd Avenue South. A total of 21 single - family residential lots (Lots 1 through 21) and a cul -de -sac (South 137th Place) are planned for the north side of South 137th Street. Another 14 single - family residential lots (Lots 22 through 35) and a small north -south residential street (43rd Place South) are planned for the west portion of the site on the south side of South 137th Street. There will be six lots (Lots 36 through 41) situated immediately south of South 137th Street on the east side of the site. These lots are bounded to the west and south by designated wetland areas (Tract A). Another wetland area (Tract B) is situated on the north side of South 137th Street opposite Lots 36 through 41. We understand the average lot size is about 5,500 square feet. Site topography is variable. For the purposes of this review, we have characterized the site and adjacent 44th Avenue South into the following general areas: .1 ► Area 1 - North and Northeast Slope: This area comprises the property north of South 137th Street'except for Tract B, and slopes moderately to steeply downward to the north and northeast. Lots 1 through 21 are within this area. Existing slopes range between about 15 and 65 percent, but are typically between about 25 and 35 percent except for a relatively flat portion near the planned intersection of South 137th Street and South 137th Place. Proposed regrading in this area includes cuts and fills and use of retaining walls to establish roadway and lot grades. Fills along the north side of South 137th Street appear to range between about 4 and 12 feet. Cuts and fills up to about 6 feet are planned for the South 137th Place cul -de -sac and associated lots. Final slopes in regraded areas appear to be 40 percent (2.5:1) or flatter. Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 3 Applied Geotechnology Inc. ► Area 2 - Wetland Tracts A and B: Consists of the wetland area south of Lots 36 through 41 and a Swale that extends north from the south property line to the planned location of South 137th Street, turns east, and drains to a culvert which extends under 44th Avenue South. No regrading is planned for these areas; however, retaining walls are planned along portions of the wetland boundaries in order to establish planned grades in adjacent areas. ► Area 3 - South Slope: This area consists of the moderately to steeply north to northeast sloping area where Lots 36 through 41 will be situated. Existing slopes are typically between about 20 to 35 percent. This area is to be terraced using balanced cuts and fills up to 10 to 12 feet and retaining walls in order to reduce topographic relief across the proposed lots and roadway. Regraded areas will be sloped at about 40 percent or flatter. ► Area 4 — West Slope: This area comprises the gently to moderately northeast sloping portion of the site west of Tract A and south of South 137th Street (Lots 22 through 35). Existing slopes in this area are generally between about 15 and 25 percent. Cuts of up to about 12 to 14 feet and fills of up to about 8 feet are planned. Regraded areas will have slopes of 40 percent or flatter. ► Area 5 - Abandoned portion of 44th Avenue: This area is situated along the east property line of the site and consists of an existing roadway constructed along the west side of a narrow, steeply sloping ravine that drains to the north. The ravine sides typically slope between about 55", and 65 percent. Evidence of previous landslide movement includes tension cracks and vertical displacement of the existing asphalt pave- ment north of South 137th Street for about 300 feet. The Terra reports include site reconnaissance, subsurface exploration and slope stability evaluations regarding the existing landslide on 44th Avenue South, and stability issues associated with the planned site development as required by the SAO for Class 3 landslide hazard areas. Recommendations are provided for foundations, basement walls, temporary and permanent slopes, site drainage,•and earthwork. The test pit. logs included in the Terra reports indicate the majority of the West Slope (Area 4) and the cul -de -sac (South 137th Place) appear to be underlain by dense to very dense glacial deposits comprising a mixture of silt, sand, and gravel which they interpret to be Till. The upper portion of the Till is typically less dense and weathered. One of the test pits (Test Pit 16) apparently encountered glacially consolidated lacustrine silt and clay underlying the Till, at a depth of about 7 feet. Till was absent in most of the test pits north of South 137th Street (Area 1) and on the northeast slope downhill from the cul -de -sac. These pits typi- cally encountered the lacustrine deposits beneath the topsoil. The upper portion of the lacustrine deposits in this area is typically light brown to tan in color and becomes blue gray at depth. Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 4 Applied Geotechnology Inc. Lacustrine deposits were encountered in all test pits along the abandoned portion of 44th Avenue South and were overlain by several feet of silty sand fill used to construct the road. The upper portion of the lacustrine /' deposits is noted as being blocky and disturbed as a result of landslide movement, which Terra attributes to improper construction of the road. SENSITIVE AREAS ORDINANCE REQUIREMENTS (SCOPE ITEM 3) Based on our review of the City's SAO and our understanding of site subsur- face conditions, we present the following opinions regarding Areas of Potential Geologic Instability as defined in the SAO: • The majority of Area 4 underlain by Till appears to meet the criteria for Class 2 landslide hazard areas. • The majority of Areas 1 and 3, the northern one -third (approximately) one third of Area 5, and the more steeply sloping portions of Area 2 should be considered Class 3 landslide hazard areas. • The southern two - thirds (approximately) of Area 5 is by definition Class 4 because of previous landslide activity. Based on their stability evaluations, Terra concluded that the site slopes in their present condition appeared to be generally stable. The Terra reports did not indicate that detailed slope stability analyses were performed in formulating their conclusions; however, such analyses are not mandatory under the SAO for Class 3 areas. We conclude that the Terra reports in general appear to have addressed the requirements of the SAO; however, we judge that these slopes have a high potential for landslides because of the extensive site grading planned for the proposed development. We believe this opinion is supported by the instability of 44th Avenue South adjacent to the site. Accordingly, we judge that more detailed stability analyses and design details should be provided to the City to demonstrate that the development can be safely constructed as planned. Our comments and recommendations are discussed further in the following paragraphs. Class 3 landslide hazard areas are areas that, due to topographic and subsur- face conditions, have a high potential for slope instability. Based on our site reconnaissance, we generally concur with Terra's opinion regarding existing slope stability conditions on the site; however, previous cutting and filling on the slope adjacent to the site for construction of 44th Avenue South apparently resulted in landsliding. Accordingly, we judge there is a high potential for future slope instability both during and after site development if cuts and fills are not properly constructed. Specifically, we present the following primary review comments: ► Based on review of the test pit logs investigating the landslide on 44th Avenue South, it appears the landslide involved movement of the upper, more weathered portion of the lacustrine deposits, likely as a result of Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 5 Applied Geotechnology Inc. surcharge by the overlying fill. Other contributing factors likely included lack of adequate subdrainage at the base of the fill and inadequate keying and benching.of the fill into the slope. The Terra reports recommend placement of fill soils on the steeper slopes in the northern portion of the site be minimized. Our review indicates fills on the order of 4 to 12 feet are planned along the north side of South 137th Street, and up to about 6 feet around the South 137th Place cul- de -sac. We recommend the developer prepare for review by Terra and the City detailed cross - sections in all planned fill areas indicating existing and proposed grades and illustrating how the fill will be keyed, benched, and drained as recommended in the geotechnical report. A typical detail should also be prepared illustrating the geotechnical engineer's recommended key at the toe of all proposed fills on slopes. Calculations supporting adequate safety factors against slope instabili- ty should be provided for review by the City. ► Because of the relatively impermeable nature of the lacustrine deposits and the potential for saturation of fills placed on top of these materials, we judge that permanent subdrainage measures, such as the blanket drain recommended in the Terra report, will be essential for satisfactory long -term performance of the planned engineered fills. We suggest the developer, in conjunction with the geotechnical engineer, prepare detailed design cross- sections addressing subdrainage provisions for fills placed on slopes and underlain by lacustrine deposits. ► Substantial earthwork operations will be required for the proposed development and will include significant cuts that may increase the extent of the site where the lacustrine soils will be at or near final grade. In addition, the Terra report indicates the majority of the site soils will be extremely difficult to work in wet weather. Accordingly, we judge it essential that earthwork operations be carefully planned in order to address.erosion and slope stability issues during construction. We recommend the developer prepare a detailed plan for earthwork operations for review by Terra and the City demonstrating how site preparation will be sequenced and performed, and what temporary erosion control measures will be used. Limiting earthwork to the drier summer months is'Istrongly recommended. If development will be performed in phases over 's. number of years, this should be reflected in the sequenc- ing plan, together with interim site restoration details for erosion control. ► The grading plans indicate many of the proposed residences may be supported on a combination of dense or hard native soils and structural fill. We suggest Terra be requested to review the foundation details and comment on the need for connecting individual footings or supporting the houses on post- tensioned slabs as a possible means of reducing potential for differential settlement of the structures. ► Because of the potential for slope instability if fills are not properly constructed, we judge it essential that the geotechnical engineer be required to monitor site preparation closely to confirm that earthwork is completed in accordance with their recommendations. Monitoring Ms. Denni Shefrin City of Tukwila May 17, 1993 Page 6 Applied Geotechnology Inc. should include confirmation of stripping depths and keying and benching for fills, subdrainage installation monitoring, and fill compaction control as recommended in the Terra report. The geotechnical engineer should also confirm competent bearing and adequate embedment of founda- tions•for structures constructed on Class 3 slopes. LOT DENSITY AND SITE STORM DRAINAGE (SCOPE ITEM 4) Lot Density Because of the moderate to steep slcpes and presence of clay soils, we judge that unless the planned extensive grading for the proposed lot layout /density is properly sequenced, constructed, and monitored, there is potential for slope stability problems to occur both during and after construction. We suggest that other layouts aimed at minimizing site cutting and filling and avoiding more steeply sloping portions of the site also be considered. Site Storm Drainage We understand SEPA review comments by other agencies have included consider- ation of on -site infiltration of storm drainage. Terra states that all storm drainage, including roof downspouts, should be tightlined to the storm drain. Because of the underlying relatively impermeable lacustrine soils and the' potential for impacting slope stability, we concur with Terra that this site is not suitable for on -site infiltration of stormwater. Biofiltration swales are planned along the west side of the northern portion of the abandoned 44th Avenue South, and along the site property line border- ing Southgate Park. Design and construction of biofiltration swales is not specifically addressed in the geotechnical report. The swale along 44th Avenue South apparently will not require grading becausej�`tS \d- ur an existing ditch will be used. Infiltration from the Swale could collect at c,ev0 00 or near the contact between the weathered /unweathered lacustrine clay and increase the potential for slope instability, as apparently occurred to the south of this Swale location. We suggest consideration be given to lining this swale to prevent infiltration. The planned swale along the north property line is situated on the lower portion of the moderate to steep north slope. A 9 -foot maximum height retaining wall is shown on the upslope side of the Swale. In our opinion, siting a biofiltration Swale at this location should be avoided if possible because of the slope and inclination, soil types, and need for excavation of these lacustrine soils. We recommend Terra review and comment on the proposed Swale location. The developer should provide details for review by Terra and the City illustrating the type of retaining wall planned, including stability analyses and how it will be safely constructed at the base of this Class 3 slope. Ma. Denni Shefrin City of Tukwila May 17, 1993 Page 7 Applied Geotechnology Inc. :4 We understand the current plan to reduce potential for increased runoff onto adjacent properties to the north will include tightlining all discharge from both biofiltration swales to the storm drain on 44th Avenue South at the northeast corner of the site. A shallow swale.along the toe of the north slope could also be included to collect runoff from unpaved areas of the Area 1 lots and direct it to the storm drain system. We hope this provides the information you require at this time. Please call if you have any questions or require clarification. Sincerely, APPLIED GEOTECHNOLOGY INC. aK( /1. Garry H. Squires, P Senior Engineer Donald E. Bruggers, P.E. Principal Engineer. GHS /DEB /jlh attachment IExiiaes 10/23/9 3 ate August 11, 1990 May 5, 1997. ,,May 5, 1992_ October 16, 1992 November 8, 1992 December 22, 1992 February 12, 1993 February 23, 1993 March 15, 1993 April 23, 1993 March 9, 1993 September 30, 1991 CITY OF TUKWILA Document List for Review May 5, 1993 Author Terra Associates Dujardin Development Terra Associates Tukwila Public Works ,Tukwila Department of Community Development Terra Associates Tukwila Community Development Terra Associates Tietze & Associates Tukwila Community Development Charles Morgan & Associates /Erich O. Tietze & Associates Tukwila Ordinance No. 1599 02 !.)RAilurl N. LL t') miNiJrJ `; Applied Geotechnology Inc. Subiect Geotechnical Study ' Residential Plat Roadway Design Stability Evaluation 44th Avenue PRD and BLA Review Comments on development plans Review (initial) comments on development plans Updated Geotechnical Report. Residential. Plat Review (additional) Additional comments Geotechnical conditions Additional consultation Drainage analysis Analysis of storm drainage Internal memorandum comments Proposed development Plan Sheets 1 through 7 Sensitive areas • ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants Mr. Bill Fowler Dujardin Development Company f • , 9623 32nd Street SE Everett, WA 98205 r . SUBJECT: Drainage Analysis for Fosterview Estates Dear Bill: As requested by the City in its letter of February 12, 1993, the following is an analysis of the drainage conditions for the site before and after development. The City specifically asked us to address the following: the relocation of the eastern biofiltration system to the northern end of the abandoned 44th Avenue South road. whether there will be an increase of groundwater or surface water runoff to the downhill properties north of the site as a result of the development. whether peak flows of the creek will be increased. whether the wetland north of the site (Poirot's property) will be affected. BACKGROUND On January 28, 1993, we met with representatives from the City staff and Terra Associates, Inc, your geotechnical representatives for the project. At that onsite meeting, erosion of the adjacent creek was discussed as well as the fact that it appeared as if the site divides into three natural basins, each draining to a different location. The City staff made a point that in our analysis, we should determine the runoff from each basin and determine the after- development impacts. Concern about additional flows to the creek wcre expressed by the City staff. It was requested that we look into the feasibility of diverting peak flows from the creek. In addition to these matters, we walked the abandoned roadway on 44th Avenue South and discussed the potential location of a biofiltration swale. The matter of constructing a wet pond in the area of the abandoned road was raised, but Anil Butail of Terra Associates, once again expressed his concerns about constructing a major facility in that area. It was agreed that a small biofiltration swale should be considered at the northern end of the abandoned roadway where it is furthest from the creek and is in the most flat area. Flows to the swale from the developed site would reach the swale by means of a tightline pipe laid in the existing drainage ditch of the abandoned road. The pipe would not be buried, but would be covered with riprap for protection. The reason for not burying the pipe was to protect it from potential land movement and to reduce the amount of disturbance to the earth. The biofiltration swale was proposed in a manner that would not excavate into or below the toe of the exiting uphill sideslope of the road. The base of the swale would be at the approximate base of the existing drainage ditch for the abandoned road. The analysis of the drainage conditions utilized the King County computer programs for determining rainfall runoff and for sizing detention systems. Due to the steep topography of the site, wet ponds are not a feasible option for detention solutions. Underground detention tanks are proposed. The analysis that is presented is based on a preliminary design and may be further revised in the future after the City has had a chance to evaluate the results and our proposals. For purposes of sizing detention facilities, all downspouts will be tightlined to the detention systems, as recommended by Terra Associates. The detention systems were sized for ERICH 0. TIETZE AND ASSOCIATES, INC. .,, r Engineers and Consultants one half of the two -year storm and the twenty -five year storm as required by the Washington State Department of Fisheries. In addition, the systems were sized for the ten -year and 100 -year storms BASIN DESCRIPTION The analysis that is presented is limited to the site only. No offsite flow approximations have been made since the amount of offsite runoff traveling through the site is minimal and will be unaffected by the development and vice versa. BASIN 1. The site has three natural drainage basins as shown on Figure 4/7. The easternmost basin has been labeled Basin 1 and consists of a drainage course and a wetland area. The wetland area drains east toward 44th Avenue South where it enters an existing drainage swale. It then travels north along the west edge of 44th Avenue South where it ultimately is discharged through an 18 -inch cmp to the creek located on the northeast edge of the site. It is this creek that is of concern to the City. The remainder of Basin 1 travels directly to the 18 -inch cmp through the drainage course and through overland flow across the higher elevations of the Basin. After development, existing Basin 1 will be divided into three sub - basins. Area 1A will include the existing drainage course and wetland. This portion of Basin 1 will be left undisturbed and will continue to discharge to the creek through the 18 -inch cmp. Area 1B will be developed and its flows will be detained in Detention System No. 2. The detained flow will be treated in the biofiltration swale located at the north end of the abandoned road on 44th Avenue South. Flow from this area will be diverted from the creek to a culvert system located at the northern end of the abandoned road. Area 1C will also be developed and will be detained in Detention System No. 3 as shown on Figure 4/7. Runoff from the detention system will be treated in a biofiltration swale located along the northern property line next to Southgate Park. Flow from this area will be diverted from the creek to the park property in order to recharge the existing wetland located north of the park. BASIN 2. Existing Basin 2 is shown on Figure 4/7. It drains in a northeasterly direction toward the ditch on the west side of the abandoned road. Ultimately, the ditch discharges to the culvert system at the north end of the abandoned road. BASIN 4. Existing Basin 4 also drains in a northeasterly direction and ultimately enters the same culvert system of Basin 2, although one or two catch basins further north. Existing Basins 2 and 4 both drain to the same culvert system, it is just that Basin 2 flows through the drainage ditch where the biofiltration swale is located. For that reason, flows from Basin 2 had to be calculated separately in order to incorporate them into the biofiltration swale design. Since Basin 4 does not drain to the ditch (biofiltration swale), it was considered separately. Existing Basins 2 and 4 will be divided into 4 sub - basins in the developed site. The upper portion of Area 2A will be detained in Detention System 3. The lower portion of Area 2A will be detained in Detention System 1. Flows from both detention systems will then be treated in the northern biofiltration swale. Area 2B consists of house on Lots 14, 15, 16, 17, and 18. Runoff from this area will be discharged directly to the culvert at the northern end of the abandoned road. Since the runoff does not include any pavement areas, it will not biofiltration treatment prior to discharge. Area 2C will be undeveloped except for some landscaping. It will continue to drain to the ditch along the abandoned road. Flows from this sub -basin will be treated in the biofiltration swale. Area 2D will be undeveloped, except for some landscaping. Its flows will continue to drain to the culvert system to which it presently drains. BASIN 3. Existing Basin 3 presently drains to the north of the site, across the Southgate Park, to the wetland on the Poirot property. The developed basin will consist of 4 sub - basins. Area 3A will drain to Detention System 3, as previously described. Area 3B will drain to Detention System 1. Both systems will be treated in the northern biofiltration swale. Area 3C will mostly be undeveloped except for some landscaping and the biofiltration swale. Since this small area will drain to the biofiltration swale, its flows were calculated in order ERICH 0. TIETZE AND ASSOCIATES, INC. ,a. • Engineers and Consultants to size the biofiltration swale. Area 3D will be undeveloped except for the gravel path and will drain north to the Park as it presently does. A summary of the existing basin characteristics follows: BASIN NUMBER IMPERVIOUS AREA PERVIOUS AREA 1 0.1 4.70 2 0.0 3.12 3 4 ANALYSIS 0.0 2.53 0.0 0.56 For purpose of this analysis, it was presumed that Areas 1B and 1C in existing Basin 1 would be diverted from the creek to which they presently discharge in order to reduce the peak flows in the creek and the subsequent potential for erosion. The undeveloped portions of existing Basins 2, 3, and 4 will continue to discharge to their respective natural discharge areas. The developed portions of existing Basins 2, 3, and 4 will be detained and treated in the northern biofiltration swale. From the swale outlet, the detained and treated runoff will be discharged across the park property by means of a level spreader. The level spreader is used to produce a sheet flow effect rather than a point source discharge. The level spreader is shown on park property but that can be moved onto the site if its location presents a problem. A facility is shown on Figure 4/7 to divert flow from the level spreader to the culvert system to which existing Basins 2 and 4 discharge. The diversion structure will ultimately be designed to discharge a set amount of water to the park property and ultimately to the wetland on the Poirot property. For purposes of this analysis and to provide the City with analysis data, it was presumed that all flow from Detention Systems 1 and 3 will be diverted to the park and wetland. Ultimately, the City may determine that a lesser quantity of flow should drain to the wetland and, thus some could be diverted to the culvert system at the north end of the abandoned road. The following is a table of basin characteristics, before and after development: STORM RUNOFF INFIL TOTAL BASIN NUMBER FREQUENCY PEAK FLOW VOLUME VOLUME VOLUME (cfs) (cf) (cf) (cf) 1 2 -yr 0.45 10783 24065 34848 (to creek) 10 -yr 0.63 20152 30378 50530 25 -yr 1.68 30001 30983 60984 100 -yr 2.16 37183 32513 69696 2 2 -yr 0.20 6814 15837 22651 10 -yr 0.53 13915 18929 32844 25 -yr 0.78 19226 20414 39640 100 -yr 1.01 23830 21472 45302 STORM RUNOFF INFIL TOTAL ERICH O. TIETZE AND ASSOCIATES, INC. Engineers and Consultants STORM RUNOFF INFIL TOTAL BASIN NUMBER FREQUENCY PEAK FLOW VOLUME VOLUME VOLUME (cfs) (cf) (cf) (cf) 3 2 -yr 0.18 5525 12843 18368 (to park and 10 -yr 0.47 11297 15336 26633 wetland) 25 -yr 0.70 15608 16535 32144 100 -yr 0.90 19347 17389 36736 4 2 -yr 0.04 1223 2843 4066 (to property 10 -yr 0.10 2499 3396 5895 northeast 25 -yr 0.14 3453 3661 7114 of site) 100 -yr 0.18 4280 3851 8131 IA 2 -yr 0.29 6816 22950 29766 (equates to 10 -yr 0.72 13583 29577 43160 Existing 25 -yr 1.05 18612 33480 52092 Basin 1) 100 -yr 1.34 23009 36523 59532 1B, 2C & 2B 2 -yr 0.22 8490 3634 12124 (equates to 10 -yr 0.44 • 14094 3486 17580 Existing 25 -yr 0.71 18083 3135 21218 Basin 2) 100 -yr 0.91 21510 2738 24248 2D 2 -yr 0.08 1219 1685 2904 (equates to 10 -yr 0.16 2219 1992 4211 Existing 25 -yr 0.21 2930 2152 5082 Basin 4) 100 -yr 0.26 3538 2270 5808 1C, 2A, 3A 2 -yr 0.21 19803 14319 30492 3B, 3C & 3D 10 -yr 0.39 32823 16654 49477 (equates to 25 -yr 0.54 41889 17825 59714 Existing 100 -yr 0.84 49833 18411 68244 Basin 3) In the table above, the runoff volume is the quantity of surface runoff that can be expected under the various conditions. The peak flow is the rate of surface runoff that can be expected. The infiltration volume is the quantity of rainfall that is expected to percolate into the ground. The total volume is the sum of the runoff quantity and the infiltration quantity and represents the total rainfall on the areas. Foe purposes of estimating infiltration drainage patterns, it was presumed that the groundwater hydrology follows the surface topography. Regardless of the direction that the surface water may be diverted by the developed site drainage system, pervious areas in the existing basins that remain after development will continue to infiltrate to the same areas that they feed prior to development. CONCLUSIONS Examination of the table above indicates that the proposed concept will: reduce the peak flows from the site to the creek by about 35 %. ETA ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants 121 519 Avenue Sune 205 Eamonos. WA 98020 206.771.6212 FAX 206.775.0236 the peak flows to the culvert system at the north end of the abandoned road are about 12% less for the 100 -yr storm. the peak rate of runoff to property northeast of the site will increase by a maximum of 0.07 cfs (27 gallons per minute). Although the peak runoff will increase slightly, the volume of surface runoff will be reduced by about 30 %. Groundwater flows should also be reduced by about 40 %. the park property and the downstream wetland located on the Poirot property could experience an increase in total volume of runoff and infiltration depending on the amount of runoff that is diverted to the culvert system at the north end of the abandoned road. For purposes of this analysis, it was presumed no runoff will be diverted to the culvert system; consequently, all runoff from the northern swale will discharge to the park /wetland. This allocation of runoff can be changed to some other ratio as the City deems necessary. The concept as presented indicates that the wetland can be provided with sufficient water to sustain its viability. If less water is deemed to be more suitable, then water can be discharged through the culvert system at the end of the road. Detention system storage volumes and allowable discharge rates may need to be modified during final design to obtain the specific balance that is desired between the various basins. The conclusion of this analysis is that through a series of detention systems and diversions it is possible to alter the flow rates to the existing basins without jeopardizing the existing viability of the basins. In the case of Basin 1, reduced peak flows to the creek could actually reduce the erosion potential of the creek. We will need to work with the City staff during the final design phase of the project to accomplish the specific goals that the City may have for the basins. This initial presentation indicates that the concept for onsite detention as presented is a viable solution and the preliminary design indicates the extent of the facilities that are likely to be needed to develop the site. Very truly yours, ERICH O. TIETZE AND ASSOCIATES, INC. Erich O. Tietzc, P.E. President k_,4 fTA ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants 121 5th Avenue Suite 205 Edmonds, WA 98020 206-771-6212 FAX 206-775-0236 Ms. Denni Shefrin, Associate Planner Department of Community Development City of Tukwila 6300 South Center Blvd. Tukwila, WA 98188 SUBJECT: Criteria to Be Used in Drainage Design for Fosterview Estates Dear Ms. Shefrin: May 12, 1993 J The following is a presentation of the criteria and parameters that will be used in the design of drainage facilities for Foster View Estates. The approach that is presented represents a culmination of discussions and meetings that we have had with the City over the course of development of this project. The engineering procedures that will be used will conform to those described in the latest edition of the King County, Washington, Surface Water Design Manual which we have been required by the City to use for the design of drainage facilities for the site. Evaluations will be made for the 2 -year, 10 -year, 25- year, and 100 -year storm events. These evaluations are in excess of the City's usual requirement for evaluation of only the 10 -year and 25 -year storm events. Detention facilities will be designed in order to limit the total runoff rate from the developed site as a whole to that of the total runoff rate from the undeveloped site for each of the evaluated storm events. Where specific concerns have been expressed for some of the sub - basins that receive runoff from the site, runoff volume from the developed site will be limited or eliminated from problem sub - basins (refer to Off-site Drainage Analysis for Fosterview Estates). Presently, runoff from the site discharges to three separate sub - basins bordering the site; namely, (1) the creek located north of South 137th Street near the northeast boundary of the site, (2) a culvert system located at the south end of 43rd Avenue South, at the site's north boundary, which discharges to private property northeast of the site, and (3) the wetland located north of the site and north of Southgate Park, on the Poirot property. Runoff from the site reaches the wetland by sheet flow across the park property rather than in a defined channel. All of the sub - basins ultimately combine at the approximate intersection of South 132nd Street and 42nd Avenue. The runoff from the wetland on the Poirot property travels north to South 133rd Street where it joins with Southgate Creek and travels crosses South 133rd Street and travels north through a channel to South 132nd Street and 42nd Avenue South. The runoff from the culvert at the end of South 43rd Avenue and the creek northeast of the site separately cross South 135th Street (Macadam Road South) where they ultimately join in a drainage course located on the southwest boundary of Fostoria Park. This drainage course crosses the commercial /industrial site through a series of large culvert pipes (5 feet and 3 feet diameter) and swales to the intersection of South 133rd Street and South 132nd Street. The following is a discussion of the approach that will be taken for each of the specific sub - basins that receive runoff from the site. Please refer to the Off -site Drainage Analysis for the Fosterview Estates. As part of the design of runoff control facilities for the project, the City has requested that runoff to the creek located northeast of the site be reduced in order to reduce the potential for erosion in the drainage course from South 137th Street to South 135th Street (Macadam Road South). The City has ETA ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants .. A.enue Su.ie 2.5 Ecmonae Y.A 90020. 206•7•.02:2 FAX 206.775.0235 plans to construct a sediment - control facility at South 135th Street to remove sediment from the creek before it enters the commercial /industrial area of Fostoria Park. In order to meet the City's objective for this sub - basin, all runoff from the developed portion of the site that presently discharges to the creek will be diverted to the culvert at the end of 43rd Avenue South. By diverting this flow, the resulting runoff to the creek will be less than presently occurs from the undeveloped site. The reduced flowrate will reduce the erosion potential in the creek. The undeveloped wetland portion of the site as well as a drainage course on the site that presently discharge to the creek will remain undeveloped and will continue to discharge to the creek as they presently do. It is estimated that the existing runoff rate to the creek for the 100 -year storm is 2.2 cubic feet per second (cfs),. After development, the estimated 100 -year runoff rate to the creek will be 1.3 cfs. V /tj p . 1L.C-S. crt +>J's= 1.:1c In addition to the specific concern expressed for erosion in the creek, the City has expressed a general requirement to preclude flooding of downstream property as a result of development of the site. The City has also expressed the need to maintain the viability of the wetland located north of the site on the Poirot property. In instances where wetland viability may compete with the avoidance of downstream flooding, the City has opted for a preference to control downstream flooding. In consideration of these parameters, the following approach will be taken with regard to runoff discharge to downstream property in general and the viability of the Poirot wetland in particular. -6,,;ik:i .j 4 Presently, the wetland on the Poirot property receives surface runoff fr m the site as well as surface runoff from Southgate Park and surrounding private property. In additi , the wetland is recharged by subsurface flow from these same properties. Of the area tributary to th wetland (about 12 acres), it is estimated that the site represents approximately 14 percent of the tot As a result of developing the site, some recharge from subsurface flow will be eliminated. It is estimated that subsurface recharge of the wetland will be reduced by approximately 6 percent due to construction of impervious surfaces /Of the total volume of water received by the wetland from both surface and subsurface sources, the reduction of subsurface flow represents less than 4 percent. This reduction should have little impact on the wetland. In order to minimize flooding impacts to the wetland and the surrounding area, the design will limit the volume of surface runoff from the site to the equivalent volume of runoff that presently discharges from the undeveloped site during the 25 -year, 24 -hour storm. In order to accomplish this, the runoff rate from the developed site may actually be less than from the undeveloped site since the duration of runoff from the developed site will be longer than presently occurs due to detention of the site runoff. The runoff from the developed site that does not discharge to the Poirot wetland or the creek northeast of the site, which have both been previously described, will discharge to the culvert that is located at the southern end of 43rd Avenue South, at the northern boundary of the site. The culvert is 12- inches in diameter and travels north on the west side of 43rd Avenue South for approximately 170 feet. At that point, the culvert turns east and discharges to private property located northeast of 43rd Avenue South. The runoff travels across the private property by sheet flow rather than in a defined drainage course. The flow then travels north to the ditch on the south side of South 135th Street (Macadam Road South) where it turns northwest for about 100 feet. It then enters a 24 -inch culvert that crosses South 135th Street in a northerly direction and joins with the creek flow on the Fostoria Park property. Since the private property does not have a defined drainage course, the site would be subject to inundation from runoff from the developed site. The property owner is reluctant to permit construction of a piped system across his property since its location could affect future subdivision of the site. An alternative discharge route was suggested to the City and has received preliminary approval, subject to improvements by the developer to insure that the system has the capacity to carry the runoff from the site. The proposed route would begin at the point where the existing culvert system turns east to discharge to the private property northeast of 43rd Avenue South. The outlet pipe at the C C L. ETA ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants :21 5th avenue SuJe 20 A ?6C2C ne.7" W212 catch basin that discharges to the private property would be plugged so that no runoff would discharge to the private site. The culvert system would be extended north approximately 350 feet to connect with the existing terminus of the culvert system on 43rd Avenue South. Approximately 200 feet of 8 -inch �" culvert would be replaced with 12 -inch culvert pipe. The system continues north on 43rd Avenue South to the intersection with South 135th Street where it travels northerly along the west side of South 135th Street (42nd Avenue South). Approximately 150 feet from the intersection, the system increases in size to 18 inches. The system continues north to the south end of an overpass at South 133rd Street. There, the system turns east and crosses 42nd Avenue South where the flow continues down the hillside in half of a corrugated metal pipe to the swale system located on the south side of South 133rd Street. The flow continues east to South 132nd Street where it crosses north in a pipe separate from the rest of the flow from the industrial park and upstream areas. As part of the drainage system design, an Off -site Drainage Analysis for Fosterview Estates was required to evaluate the capacity of downstream systems to carry runoff from the developed site. Since the project proposes discharge of site runoff to a different system than at present, evaluation of the downstream system was required as part of the off -site analysis. The downstream system was found to have the capacity to carry diverted runoff from the developed site. In addition to the off -site considerations previously described, the following describes the approach that was used in locating the biofiltration swales. Biofiltration swales may be located upstream or downstream of detention facilities. Swales are typically designed for the 2 -year runoff rate with regard to its biofiltration function. The hydraulic capacity of the swale is then checked for the 100 -year runoff to insure that overflow will not occur. Only runoff from paved areas requires biofiltration. Roof runoff and runoff from landscaped areas do not need biofiltration. One option of providing biofiltration is to treat only the runoff from paved areas before detention is provided. A second option is to provide biofiltration after detention has been provided. By providing biofiltration after detention, the swale is sized for the total runoff from the site, including roof runoff, since all runoff from the site will have been combined in the detention facility. However, because the flows have been detained, the peak flow rates will be reduced considerably from the undetained rates. In the case of upstream biofiltration swales, even though only runoff from paved areas requires treatment, the undetained peak flow rates from paved areas are often as great or greater than the detained flowrates for runoff from the entire site. We propose use of biofiltration swales downstream of detention facilities since the variation in flowrates is less and the swales are thus better able to function as biofiltration systems over a greater range of flows. Furthermore, the site topography is better suited to such a system. Since runoff from all paved areas requires biofiltration, potential biofiltration swale locations must be located downhill from the lowest paved areas. Furthermore, potential biofiltration swale areas should be located in areas where the transverse slope is relatively flat since the maximum transverse slope for a swale is 6 percent. With these parameters in mind, the locations that are shown on our submittals were selected. The City staff has proposed locations for consideration. One of those proposed has been incorporated into the design plan along the abandoned road on 43rd Avenue South. Although the other locations that the City proposed have the parameters required for function as a biofiltration swale, their elevation on the site precludes them from consideration since they are at elevations that are higher than the pavement that they must serve and /or the detention facilities. A concern that the City has with regard to the biofiltration swale shown on the north boundary of the site is the fact that a wall of approximately 9 feet high is required to allow for grade adjustments between the proposed swale and the existing topography. In the final design, we will endeavor to ERICH 0. TIETZE AND ASSOCIATES, INC. Eng Inaers and Consultants reduce the swale width which will have the effect of reducing the wall 11 -ft ettei height. We will also consider other options such as landscape treatment to soften the visual effect of th I hope that this documentation satisfies the needs of the City. If you additional information, please feel free to call. Very truly yours, ERICH 0. TIETZE AND ASSOCIATES, INC. ( • Erich 0. Tietze, P.E. • President 4.,.\ •4_,..___. ) e wall. have any questions or require ERICH 0. TIETZE AND ASSOCIATES, INC. . Engineers and Consultants OFF -SITE DRAINAGE ANALYSIS FOR FOSTERVIEW ESTATES MAY 12, 1993 • .1 Fn I J;r : { I ._ • . , C,_ 'a DEV LCh:-..iENT INTRODUCTION AND RESOURCE REVIEW. As part of the Fosterview Estates submittal to the City, an off -site analysis of upstream tributary drainage areas and downstream runoff receiving areas is required. This is a requirement for all projects that propose the construction of on -site drainage facilities as part of a site's development. Any potential downstream problems that are identified as a result of the analysis must be documented and mitigation measures to correct the problems must be recommended. Mitigation may include construction of additional on -site detention facilities to reduce runoff rates from the developed site or may include enlargement of the downstream drainage facilities to correct the identified problems. Any combination of on -site and downstream mitigation measures may be recommended. The procedures that were used in conducting this off -site drainage analysis are provided in the King County, Washington, Surface Water Drainage Manual, as updated November 23, 1992. The manual requires that a downstream analysis be conducted to a point where the site area represents 15 percent or less of the upstream tributary area or a point one - quarter mile downstream, whichever is farthest from the site. For this analysis, evaluation was performed for a distance of one - quarter mile downstream of the site. The Fosterview Estates site lies within the Fostoria Basin (the Basin). The site is approximately 10 acres in size and represents only a small portion of the Basin's total 1,623 acres. The City of Tukwila Fostoria Basin Drainage Study (the Fostoria Study), prepared by KCM in May 1986, has already studied the entire Fostoria Basin and its sub - basins. This off -site analysis has incorporated the relevant findings of that study in this report. The Fostoria Study describes various sub - basins within the Basin and documents problems within the sub - basins and the Basin as a whole. The study recommends solutions to the sub -basin problems and a regional solution for the entire Basin. The study identifies the sub - basins that are tributary to the Fosterview Estates site and the sub - basins to which the site drains. The study identifies predicted peak flows for the 25 -year storm for each sub - basin at full development, based on current zoning information at the time of the study. Although the Fostoria Study analyzed the larger sub - basins in the Basin, it did not analyze in detail the upper reaches of the sub - basins that are relevant to development of the Fosterview Estates site. For that reason, the Fostoria Study has been used to document only the problems that are relevant to the Fosterview Estates site in terms of the larger scope of the region, while the emphasis of this investigation concentrates on an evaluation of potential impacts to the upper portions of the sub - basins that are specific to the Fosterview Estates site. During the process of identifying potential downstream impacts, both runoff volume and runoff rates must be considered. Both of these factors were considered in this investigation and in the Fostoria Study. Both the Fostoria Study and this investigation used computer 1 EA ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants 121 51n Avenue Suwte 225 Edmonds ''.A 95020 206 - 771.6212 FAX 206. 775.0236 analyses to predict runoff rates and volumes in the sub - basins and the region as a whole. According to the methodology section of the Fostoria Study, "the 25 -year, 6 -hour storm event was selected to represent the most appropriate storm event for the major drainage courses. The six-hour storm event was selected to ensure that the entire basin would achieve its time of concentration prior to the occurrence of the peak rainfall intensities. Furthermore, situating the peak rainfall intensities, as was done, would allow the soil to become sufficiently saturated prior to the peak rainfall occurrence. Thus, peak runoff would occur since the soil would have very limited infiltration capacity. Selecting a longer duration storm event would not influence the peak rainfall intensities which produces the peak runoff rate. Rather, only the total storm volume would be altered. This would not alter the recommended drainage pipe diameters since they are sized to accommodate peak flow rates. A longer duration storm may influence the size of a detention facility. However, this would depend upon the configuration of the particular storm event and the limiting discharge allowed to pass through the detention facility." King County's computer programs were used in this investigation to estimate runoff rates from the undeveloped and developed site. The procedures for the analysis are documented in the King County, Washington Surface Water Design Manual. Runoff rates and volumes were calculated for the 2 -year, 10 -year, 25 -year, and 100 -year storms, having a duration of 24- hours. In comparison to the values developed in the Fostoria Study, these values should be more conservative, especially with regard to runoff volume since this analysis considered the 24 -hour storm events. Various alternatives were developed in the Fostoria Study to solve the identified problems. Some solutions were specific to particular sub - basins and are needed independently of the regional solution. For the Basin as a whole, four specific regional alternatives were considered. Some of the regional alternatives proposed regional detention facilities in order to reduce the size of replacement facilities where existing facilities are overloaded. Other variations of the regional alternatives proposed larger replacement facilities without use of regional detention facilities. It was stated in the report that the larger replacement facility variations would "offer slightly greater degrees of reliability." The recommended regional plan selected one of the larger replacement facility variations rather than a regional detention alternative. Since it has been stated in the Fostoria Study that runoff volume will not impact the recommended facilities, it follows that an increase in runoff volume from the Fosterview Estates site will not impact the facilities that have been recommended in the Fostoria Study. Furthermore, since peak runoff rates from the developed site will be limited by on -site detention to match the runoff rates from the undeveloped site, peak runoff rates from the development will not impact the recommended regional facilities. For these reasons, it was concluded that development of the site will not impact the findings or the recommendations that were made in the Fostoria Study. The findings and recommendations of the Fostoria study, as they relate to development of the site, are documented later in this report for each relevant sub - basin. With regard to the upper reaches of the sub - basins, this investigation considered both runoff volume and peak runoff rates. The evaluation of potential impacts on the upper reaches of the relevant sub - basins and the mitigation measures that are recommended are documented later in this report. STUDY AREA DEFINITION AND MAPS. The study area for this investigation is shown on Figure 1. It consists of Sub - basins 15, 16 and 18, as identified in the Fostoria Study. 2 ETn ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants :21 51n ..venue Su.le 2:5 Eamands 1.: ?6020 206.77—.6212 F4% 206-775.0236 The Fosterview Estates site is also shown on Figure 1. Table 1 indicates the overall size of each sub - basin, the portion represented by the Fosterview Estates site, and the percentage of the sub -basin occupied by the site. TABLE 1. COMPARISON OF SUB -BASIN SIZES TO CONTRIBUTING AREAS FROM FOSTERVIEW ESTATES SUB -BASIN NUMBER SUB -BASIN AREA FOSTERVIEW ESTATES AREA PERCENT OF SUB -BASIN AREA 18 45.3 2.3 5.1 15 74.5 4.3 5.8 16 18.5 3.3 17.8 FIELD INSPECTION AND PROBLEM IDENTIFICATION. The following description is based on a review of topographic maps, information provided in the Fostoria Study, and field investigations that were conducted for the specific purpose of preparing this analysis. Each of the Fostoria Study sub - basins have been divided into smaller sub - basins for purposes of this analysis. These are shown on Figure 1. Figure 2 presents the relevant conveyance features in each sub - basin. In addition to the existing facilities, the improvements proposed by the Fostoria Study are also presented. Sub -basin 18. Sub -basin 18 has been divided into four smaller sub - basins as shown on Figure 1. The western portion of the sub -basin bypasses the site and is represented on Figure 1 as Sub -basin 18A. The upper portion of Sub -basin 18A consists of residential development. At approximately South 137th Street, west of Pacific Highway South, a drainage course begins. The drainage course travels northerly, through undeveloped woods, to 40th Avenue South. It crosses 40th Avenue South and travels through relatively undeveloped woods to South 133rd Street where it enters a 36 -inch culvert (Figure 2). Element 3 of the Fostoria Study indicates that Sub -basin 18A suffers from erosion and sedimentation problems in the Iower reaches of the drainage course. The Fostoria Study recommends stabilization of 700 feet of a natural channel between 40th Avenue South and 42nd Avenue South and construction of a sediment trap upstream of the 36 -inch culvert. Since runoff from the Fosterview Estates site does not drain to Sub -basin 18A, the Fosterview Estates site does not now, nor will it after development, create a problem in Sub -basin 18A and, therefore, is independent of the recommended solutions that are presented in the Fostoria Study for Sub -basin 18A. For this reason, the improvements that have been proposed for this sub -basin are not shown on Figure 2. The runoff from Sub -basin 18A continues in the 36 -inch culvert, approximately 150 feet, along the south edge of South 133rd Street, to a catch basin where it joins with flow from Sub - basins 18B, 18C, and 18D (Figure 2). It is at this point that flow from the Fosterview Estates site first joins with runoff from Sub -basin 18A. 3 FIGURE 1: STUDY AREA MAP \ • • • • FIGURE 2: EXISTING FACILITIES. ANQ, ..FOSTORIA' IMPROVEMENTS._ s� 13 /Sr sr t' • NT •T Tn • I• i 1 DIVERSI •. • ttog5 17 "�'.1• s• m ,s ° _ r _V""'�.,.ue ...� ` ; _ GRAS S! „ALE •sy .p,i 4A26 • s5 I1 O ly.,,w e•(3) u•� • .•'��sr,'v•'� tl..+.' 4 • • • r ,•- - :�• • 180 — i�f • ► Q` 1 SOU Lot Acres ^tW /Y!4 S •.; -, , t • . 15D.' - ETH ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants 121 51h Avenue Suite 205 =- Cmonos. WA 98020 206. 771.6212 FAX 206- 775.0236 Sub -basin 18B represents that portion of Sub -basin 18 that is located on the site and together with Sub - basins 18C .and 18D represent the eastern portion of Sub -basin 18 (Figure 1). There are no upstream areas tributary to Sub -basin 18B. Runoff from Sub -basin 18B presently leaves the undeveloped site by sheet flow across the Southgate Park property. This runoff, together with runoff from Sub -basin 18C, constitutes the drainage to a wetland shown on Figure 1. The City has expressed a desire to maintain the viability of this wetland, but to also consider the impact that additional flow volume may have on these downstream properties. To the extent that maintaining the viability of the wetland may cause flooding, the City has stated that flooding mitigation should be given the highest priority. The wetland acts as a storage reservoir to retain runoff. The wetland water surface rises in response to runoff from the upstream tributary areas (Sub - basins 18B and 18C). As more runoff volume is received, the water level rises in the wetland. Thus, the level of water in the wetland is higher for the 100 -year storm than for the 25 -year storm or the 2 -year storm, etc., since a greater volume of runoff results from larger storms. If the volume of runoff from the developed site is allowed to increase, then an increase in the wetland's water level may occur for that particular storm event. This could be considered an adverse impact if a significant increase in water level results in flooding damage. Wetlands, however, not only receive surface water runoff, but also receive subsurface recharge from groundwater. Consideration of changes in the groundwater recharge due to development of the site complicates the analysis. When a site is developed, typically, the impervious areas that are created usually reduce the site's ability to infiltrate rainfall into the soil. Thus the amount of groundwater that is available to feed wetlands is reduced. Potentially, two offsetting changes may occur as a result of site development. First, unless controlled, the volume of surface runoff to the wetland will increase due to an increase in impervious area. Second, the increase in surface runoff volume is at the expense of groundwater recharge. The net change in total volume of discharge to the wetlands should be minimal since the total volume of rainfall for a particular storm event is unchanged, i.e the total volume of rainfall received on a site is divided between surface runoff and groundwater infiltration. An increase in runoff should equal a decrease in infiltration. The benefit of groundwater recharge is that the wetland continues to receive water for several days after a rainfall event. This tends to sustain the wetland between rainfall events. The primary change caused by development is a decrease in the time for runoff to reach the wetland. The effort needed to establish a relationship between runoff volume and wetland water level is beyond the level of analysis required for this investigation. A practical solution that was used in this investigation was to presume that the amount of runoff volume which will be allowed to discharge from the developed site will be equal to the volume of runoff that is currently discharged from the undeveloped site during the 25 -year, 24 -hour storm. This storm event was selected as the design storm event. This presumes that the current water level in the wetlands during the 25 -year storm is acceptable in terms of flooding. Typically, flooding thresholds are analyzed for the 25 -year storm, so the assumption made in this analysis is consistent with practice. By establishing such a design criteria, the extent of flooding that now occurs for storms larger than the 25 -year storm will be reduced after development. This should be a benefit ETn ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants 121 5th Are "ue Suite 205 ^once. 1',A .,... 226•%7:•7.22 FAX 206.775.036 to the downstream property. Conversely, depending on the means that are used to control the amount of runoff volume, it is possible that the amount of runoff volume discharged from the site may be greater than at present for storms smaller than the 25 -year storm. If this is the case, water levels in the wetland may be somewhat higher than at present for storms less than the 25 -year storm. If the present wetland water level is presumed to be at an acceptable Ievel of "flooding" during the 25 -year storm, then wetland water levels less than this level should also be acceptable, even if they are higher than presently occurs for the smaller storms. In an attempt to quantify the conditions before and after development, estimates of runoff and infiltration were made for the storm events and are presented in Table 2. For the developed conditions, it is presumed that the runoff volume for any storm event will be equal to the volume of water that presently discharges from the undeveloped site during the 25 -year storm. An estimate of the reduction in infiltration due to development is also shown in Table 2. In addition, to the contribution from the developed site, the contribution from the remainder of the wetland drainage area (Sub -basin 18C) is also shown. TABLE 2. ESTIMATED RUNOFF AND SEEPAGE TO WETLAND IN SUB -BASIN 18C EXISTING CONDITIONS Storm Fret uencv From Site (Sub -basin 1813) From Sub -basin 18C Combined Total to Wetland Runoff Infiltration Runoff Infiltration Runoff Infiltration Total (cf) (cf) (cf) (cf) (cf) (ct) (cf) 2 -year 5,500 12,800 34,400 79,900 39,900 92,700 132,600 10 -year 11,300 15,300 70,300 95,400 81,600 110,700 192,300 25 -year 15,600 16,500 97,100 102,900 112,700 119,400 232,100 100 -year 19,300 17,400 120,400 108,200 139,700 125,600 265,300 DEVELOPED CONDITIONS Storm Frequency From Site (Sub -basin 18B) From Sub -basin 18C Combined Total to Wetland Runoff Infiltration Runoff Infiltration Runoff Infiltration Total (cf) (ct) (cf) (cf) (cf) (cf) (cf) 2 -year 15,600 7,200 34,400 79,900 50,000 87,100 137,100 10 -year 15,600 8,600 70,300 95,400 85,900 104,000 189,900 25 -year 15,600 9,300 97,100 102,900 112,700 112,200 224,900 100 -year 15,600 9,800 120,400 108,200 136,000 118,000 254,000 One conclusion that can be drawn from Table 2 is that the site currently contributes only about fourteen percent of the total volume of water received by the wetland. Of the total amount of water received by the wetland, groundwater recharge currently represents about forty seven percent during the 100 -year storm and seventy percent during the 2 -year storm. These numbers indicate the importance of groundwater recharge to maintaining a 5 ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants continuous inflow to the wetland. During smaller storms, the majority of water received by the wetlands is from groundwater. Table 2 also indicates the current variations in runoff and infiltration for the various storm events. The variation in runoff is considerable, while the variation in infiltration is less significant. The total infiltration to the wetland currently varies by only about thirty five percent between the 2 -year storm and the 100 -year storm. Conversely, the runoff currently increases by almost three hundred fifty percent between the 2 -year storm and the 100 -year storm. Table 2 indicates that development will reduce the variation in runoff extremes. Table 2 also shows that the net decrease in groundwater infiltration to the wetlands as a result of site development is only about 6 percent. If surface runoff is considered, the net change in total volume to the wetland between developed and undeveloped conditions ranges from a 3 percent increase for the 2 -year storm to a 4 percent decrease for the 100 - year storm. In conclusion, it does not appear that the site development will significantly affect the wetlands. Furthermore, it appears as if the decision to limit surface runoff volume to that from the existing site during the 25 -year storm will not have any adverse impact on flooding and will actually reduce the flooding potential for the 100 -year storm. Discharge to the wetlands from the developed site will be by sheet flow from a level spreader located on the north boundary of Southgate Park. Continuing with the description of Sub -basin 18, the wetland discharges to Sub -basin 18D (Figure 1). The runoff from the wetland and Sub -basin 18D, together, join with the runoff from Sub -basin 18A in the catch basin previously described (Figure 2). The runoff from Sub - basins 18B, 18C, and 18D enter the catch basin through an 18 -inch pipe. A 36 -inch culvert leaves this catch basin and continues east, crossing under 42nd Avenue South to the north side of South 133rd Street. On the north side of South 133rd Street, a drainage channel carries runoff north through Sub -basin 17 to South 132nd Street, where it joins with the other Fosterview Estates runoff from Sub - basins 15 and 16 (Figure 2). Element 3 of the Fostoria Study indicates that about 500 feet of the channel between South 133rd Street and South 132nd Street requires enlargement and riprapping due to erosion potential. In addition, a sediment trap is proposed at the entrance to a 48 -inch culvert at South 132nd Street (Figure 2). Since the channel and 48 -inch culvert carry runoff from Sub -basin 18B, which is located on the Fosterview Estates site, runoff from the undeveloped site presently contributes to the problems in this portion of Sub -basin 17. However, since the volume and peak runoff from Sub -basin 18B will be limited so as not to exceed the pre - development volume and peak runoff rate, the proposed development will not add to the existing problems in Sub -basin 17. Sub -basin 15. Sub -basin 15 has been divided into four sub - basins (Figure 1). Sub -basin 15A is the eastern portion of Sub -basin 15 and begins at the Foster Senior High School. Runoff from the area eventually forms a drainage course south of South 137th Street and between 44th Avenue South and 45th Avenue South (Figure 1). The drainage course continues north under South 137th Street, entirely bypassing the site, where a natural stream continues north to South 135th Street. The stream crosses under South 135th Street through a 48 -inch culvert and discharges to Sub -basin 16B. 6 ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants The Fostoria Study did not identify any problems in any portion of Sub -basin 15; however, the City has indicated that erosion of the channel in Sub -basin 15A has been a problem from north of South 137th Street to South 135th Street. Sub -basin 15B is upstream of the site and is the only sub -basin that discharges runoff to the site. Sub -basin 15B consists of low - density, single family development and a landscape nursery. Runoff from this sub -basin is discharged to the Fosterview Estates site at the upstream side of Sub -basin 15C, which is located entirely on the site. At the southern edge of the site (Sub -basin 15C), a drainage course begins (Figure 1) which carries runoff through the Sub -basin to an 18 -inch culvert, located just north of South 137th Street and east of 44th Avenue South. The culvert discharges to the stream in Sub -basin 15A (Figure 2) which has been identified by the City as having erosion problems. In addition to the drainage course on the site, Sub -basin 15C also has a wetland which is shown on Figure 1. Except as allowed by the City for purposes of street construction and to reduce the impact of grading on the site, development will be limited to areas outside of the drainage course, the wetland, and their buffer areas. Any impacts on the drainage course, the wetlands, or their buffers will be offset by an enhancement of the wetlands and /or buffer. Sub -basin 15D, which is located almost entirely on the site, drains northeast to a ditch on the west side of the abandoned road that connected 43rd Avenue South and 44th Avenue South. The ditch travels northwest to the northern end of the abandoned street where it enters a 12 -inch culvert (Figure 2). The culvert continues north along the west side of 43rd Avenue South, approximately 170 feet, to a catch basin where the 12 -inch culvert turns east and discharges onto private property in Sub -basin 16A. Although on -site detention will insure that peak runoff rates from the developed site will not be any greater than currently discharge to this property, the development will discharge a greater volume of runoff. This increased runoff volume would have impacts on the property receiving the runoff. Flooding could occur and the site would become much wetter than at present. Sub -basin 16. Sub -basin 16 was divided into four smaller sub - basins for this investigation (Figure 1). As previously indicated, Sub -basin 16A receives runoff from Sub -basin 15D through a 12 -inch culvert. At the downstream end of the culvert, which is almost completely buried, the runoff disperses as sheetflow across the privately -owned property of Sub -basin 16A. (The property owner is not interested in granting an easement to pipe flow across his property). The flow continues north to a ditch located on the south side of South 135th Street (Macadam Road). The ditch continues north to a 24 -inch culvert (Figure 2) that carries the flow north, across South 135th Street, to Sub -basin 16B. At this point, runoff from Sub -basin 16A joins with the runoff from Sub - basins 15A, 15B, and 1SC and the upper reaches of Sub -basin 16B. Together, runoff from these sub - basins crosses through Sub -basin 16B to the intersection of South 133rd Street and South 132nd Street, where it crosses South 133rd Street and discharges to Sub -basin 17. Sub -basin 16B begins at the downstream end of Sub -basin 15A, where the flow from Sub - basin 15A, as well as the tributary flow to it from Sub - basins 15B and 15C, is diverted from its natural course by construction of an asphalt -lined swale. This swale is on the south edge of the commercial /industrial park that is located between South 135th Street, South 133rd Street, and South 132nd Street (Figure 2). The swale continues in a northwesterly direction, where it picks up flow from Sub -basin 16A. The swale then takes on the characteristics of a natural stream. It continues northerly until it enters a 5 -foot culvert 7 ERICH 0. TIETZE AND ASSOCIATES, INC. „, Engineers and Consultants which turns in a northeasterly direction. The culvert discharges to a grass -lined swale, where it continues between two commercial /industrial buildings. The swale enters a 36- inch culvert which crosses under a parking lot before emptying into the drainage channel at the south side of South 132nd Street, at the intersection with South 133rd Street. Sub -basin 16C (Figure 1) collects runoff from the east side of 43rd Avenue, north of Sub - basin 16A. The runoff is collected in a ditch on the west side of South 135th Street (Figure 2). The ditch crosses 43rd Avenue South in a 12 -inch culvert to the west side of the intersection of 43rd Avenue South, 42nd Avenue South, and South 135th Street, where it joins the runoff from Sub -basin 16D (Figure 2). Sub -basin 16D collects runoff from the west side of 43rd Avenue South. The drainage system consists of an 8 -inch culvert at its upstream end. Although the upstream end of the system could not be found, the 8 -inch culvert discharges to the catch basin shown on Figure 2. From that catch basin, the culvert becomes 12- inches in size and continues north along the west side of 43rd Avenue South. It eventually collects the runoff from Sub -basin 16C and turns north along the west side of 42nd Avenue South (Figure 2). The 12 -inch culvert increases to 18- inches about 110 feet south of the overpass across South 133rd Street. The 18 -inch culvert continues north to the south end of the overpass. At the overpass, the culvert turns east and crosses 42nd Avenue South. The culvert turns north for about 22 feet before discharging to a half- round, 24 -inch CMP that carries the runoff down the slope to a swale on the south side of South 133rd Street. The swale continues along South 133rd Street in combination with a series of 18 -inch culverts to the intersection of South 132nd Street. At the end of the swale, the flow is collected in a catch basin, having a 24 -inch by 48 -inch grate, located in the bottom of the swale. The runoff is carried across South 133rd Street, in a northerly direction, where it enters a 30 -inch pipe, carrying runoff from Sub - basins 15, 16A, and 16B, as well as runoff from Sub - basins 13 and 14, which are not shown on Figures 1 or 2. Although the Fosterview Estates site does not currently drain to Sub - basins 16C or 16D, they have been investigated since they will play a part in the mitigations that are proposed. Together, Sub - basins 16C and 16D are the smallest sub - basins associated with this investigation. The flows in these sub - basins are small in comparison to the size of the culvert that serves the tributary area. Furthermore, except for the Fosterview Estates site, there are no other areas that can potentially discharge to this system in the future. Therefore, the culvert system in these sub - basins is ideal for accepting diverted flow from other sub -basins on the site. This is discussed later in this report. PROBLEM MITIGATION. This section of the report is divided into a discussion of the mitigations recommended in the Fostoria Study and a discussion of the site - specific mitigations that are required for development of the Fosterview Estates site. The discussion begins with the mitigation recommendations presented in the Fostoria Study. The recommendations address impacts that exist in the Basin as a whole, regardless of whether Fosterview Estates should develop or not. As previously noted, the development of Fosterview Estates will not require enlargement of the facilities recommended in the Fostoria Study. The only sub -basin of relevance to the Fosterview Estates site is Sub -basin 17. The Fostoria Study mitigation for this sub -basin was presented in the discussion of Field Inspection and Problem Identification for Sub -basin 18. 8 ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants Fostoria Study Mitigation Plan. Reference is made to Figure 2 for the location of the facilities that are described in the following. The regional mitigation plan presented in the Fostoria Study proposes construction of a diversion structure at the upstream end of the existing 36 -inch culvert serving Sub -basin 18A. From this point, a 42 -inch culvert would be constructed to the intersection of South 133rd Street and South 132nd Street (Figure 2). Some flow would continue in the existing 36 -inch culvert to the north side of South 133rd Street and on through Sub -basin 17. The new 42 -inch culvert would presumably pick up runoff from Sub - basins 18B, 18C, and 18 D. It is not clear if runoff from Sub - basins 16C and 16D would be picked up by this culvert or whether the flow from these two sub - basins would continue to flow through the swale on the south side of South 133rd Street. Continued use of the swale would provide biofiltration of the street runoff from Sub - basins 16C and 16D and the diverted flow from the Fosterview Estates site, as described later. It is presumed that flow from Sub - basins 16C and 16D will not be collected in the new 42 -inch culvert. In addition, the Fostoria Study recommends construction of a 66 -inch pipe and 4 -foot by 8- foot box culvert from the intersection of South 133rd Street and South 132nd Street, across Interurban Avenue and into the existing ditch paralleling Interurban Avenue (Figure 2). The ditch would be improved to provide 64 square feet of cross - section. Mitigation Recommendations From the Off -site Drainage Analysis. The discussion of mitigations that follows addresses the problems that have been identified as a result of this off -site drainage analysis and are specific to the development of the Fosterview Estates site. In order to evaluate the impact of runoff from the developed site and to prepare recommended mitigation measures, it was first necessary to determine the quantity of runoff from the existing, undeveloped site during various storm events. These quantities served as a baseline for determining the extent of runoff impact from the developed site. They also provided a threshold for the SEPA evaluation for the project. An estimate of runoff from the sub - basins of the existing site is presented in Table 3 for various storm events. The estimates were developed using the computer modeling program in the King County, Washington, Surface Water Design Manual. As previously mentioned, three problems have been identified during the investigation phase of this analysis. They are: 1. Potential flooding of the wetland area and viability of the wetland in Sub -basin 18C. 2. Potential flooding and saturation of private property in Sub -basin 16A. 3. Increased erosion potential in the stream located in the downstream portion of Sub -basin 15A. Having identified the drainage problems associated with development of the site, an overall concept was derived to mitigate these off -site problems within the context of the overall drainage plan for the developed Fosterview Estates site. 9 ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants TABLE 3. RUNOFF DATA FOR UNDEVELOPED CONDITIONS OF FOSTERVIEW ESTATES SITE STORM RUNOFF BASIN NUMBER FREOUENCY PEAK FLOW VOLUME (cfs) (cf) 18B 2 -yr 0.18 5,525 10 -yr 0.47 11,297 25 -yr 0.70 15,608 100 -yr 0.90 19,347 15C 15D 2 -yr 0.45 10,783 10 -yr 0.63 20,152 25 -yr 1.68 30,001 100 -yr 2.16 37,183 2 -yr 0.24 8,037 10 -yr 0.63 16,414 25 -yr 0.92 22,679 100 -yr 1.19 28,110 TOTAL SITE 2 -yr 0.87 24,345 10 -yr 1.73 47,863 25 -yr 3.30 68,288 100 -yr 4.25 84,640 A general requirement of all site development plans is that peak runoff rates from the developed site as a whole cannot exceed the peak runoff rates from the undeveloped site. Peak runoff will be controlled by construction of on -site detention facilities. Design and analysis of specific detention facilities is not part of this analysis. Even though peak runoff rates will not exceed the peak rates from the undeveloped site, the volume of runoff from the developed site will be greater than from the undeveloped site since the developed site will have more impervious area. By realizing that the volume of runoff will be greater after development, and realizing that some sub - basins are sensitive to an increase in runoff volume (Sub- basins 18C and 16A), the drainage plan concept that was formulated will mitigate the impacts in the volume- sensitive sub - basins by diverting runoff to other sub - basins that are not volume- sensitive. Before the drainage plan concept could be accepted, it was necessary to analyze those sub - basins that would receive diverted runoff to determine if their drainage facilities will be impacted. The analysis of the proposed concept is documented below. The following is a summary of the concepts that were used in the evaluation of the mitigation proposals. These concepts will be used in the development of the final design of the on -site drainage system and the off -site improvements that are proposed. 10 ERICH 0. TIETZE AND ASSOCIATES, INC. Engineers and Consultants 1. Design on -site detention systems to limit peak runoff rates from the site as a whole to no more than the peak rates from the undeveloped site. 2 Limit runoff volume to Sub -basin 16C to that presently discharged from the undeveloped site in Sub -basin 18B during the 25 -year, 24 -hour storm. This will maintain the viability of the wetland and insure that ponding in the wetland is no greater than presently occurs during the 25 -year storm. Such a limitation will actually produce a lower water level during larger storms than presently occurs. This will be a net benefit. Flow volume will be limited by diverting excess flows to Sub - basin 16D. 3. Eliminate all runoff to Sub -basin 16A, thus eliminating the potential for flooding and /or soil saturation of downstream private property. This will be a net benefit. Runoff that currently discharges to Sub -basin 16A will be diverted to Sub - basin 16D. 3. Divert flow to Sub -basin 16D from the portion of Sub - basin 15C that is to be developed. The portions of Sub -basin 15C that are to remain undeveloped, such as the wetland and the drainage course and their buffers, will continue to discharge to Sub -basin 15A. Diversion of flow from Sub -basin 15A will reduce the erosion potential in the stream in Sub - basin 15A. This is a net benefit. 4. Extend the existing culvert system in Sub -basin 16D to the northern boundary of the site and replace the existing 8- inch culvert portion of the system with 12 -inch culvert. Divert flows from Sub - basins 18B, 15C and 15D to this improved culvert system. Analyze the system to insure that its capacity is not exceeded by the diverted flow. The proposed changes to the downstream systems are shown in Figure 3. The proposed plan not only mitigates potential downstream impacts caused by development of the site, but actually improves the existing conditions. Potential flooding in the wetland in Sub - basin 18C will be limited to the existing condition for the 25 -year storm. Flooding during larger storms will be reduced. The potential for flooding of property in Sub -basin 16A will be eliminated completely. Finally, the potential for erosion in the stream in Sub -basin 15A will be reduced. All of these benefits will only be acceptable if the diversion of flow to Sub - basin 16D does not cause offsetting impacts. The analysis of the culvert system in Sub - basin 16D is documented below. The first step in the analysis of the culvert's capacity was to determine the peak runoff rate that will be carried in the system. Table 4 is a summary of existing and developed runoff rates for the 100 -year storm. Runoff rates were determined using the computer programs found in the King County, Washington, Surface Water Drainage Manual. 11 FIGURE 3. RECOMMENDED MITIGATION PLAN n Co/ (3) F 0 . S' T 0 P A �JC i -1. 19 X15 1 -,. _, .F C. c 4�Ws ERICH 0. TIETZE AND ASSOCIATES, INC. • Engineers and Consultants TABLE 4. • 100 -YEAR, 24 -HOUR PEAK FLOW RATES FOR EXISTING AND DEVELOPED CONDITIONS Sub -basin Existing Peak Receiving Point Discharge Peak (cfs) (cfs) 18B 0.9 Wetlands (Sub -basin 18C) 0.7 15C 2.16 Stream (Sub -basin 15A) 1.34 15D 1.19 Private Property 0.0 (Sub -basin 16A) 16D 1.8 (12 -inch) Culvert (Sub -basin 16D) 2.1 16D 2.1 (18 -inch) Culvert (Sub -basin 16D) 2.4 The total peak runoff in the culvert system of Sub -basin 16D was determined by summing the 100 -year hydrographs for the diverted flow from the site and the current flow in the culvert system. Typically, 25 -year storm events are used to analyze conveyance facilities. A 100 -year storm was used to be conservative. Flow rates for the 12 -inch portion and the 18- inch portion of the culvert system were calculated and are shown in Table 4. As noted from Table 4, the combined flow rates in the culvert system for the developed condition are not much greater than the rates for the existing conditions without any diverted flow. The reason for this is that by the time the diverted flow reaches the culvert system, the peak flow from Sub - basins 16D and 16C has already passed through the system. The limiting condition in the culvert system of Sub -basin 16D are the 12 -inch culverts along the west side of 42nd Avenue South. Inlet conditions control in these pipes. The estimated water depth in the catch basins for a flow rate of 2.1 cfs is 0.95 feet. Since the invert depth in these catch basins is at least 2.0 feet, no overflow conditions should result by diverting flow from the site to this system. In addition to analyzing the culvert system, the swale on the South side of South 133rd Street was also analyzed. The swale is grass -lined with dense vegetation. A Manning's "n" value of 0.08 was used for the analysis. The swale bottom is approximately 2 feet wide. The side slope are steeper than 1:1. The swale slope is estimated to be 0.06 percent at the intersection at South 132nd Street. Under these conditions, the combined flow from Sub - basin 16D and the diverted flow from the site will have a water depth of approximately 1 foot. Since the swale is at least 1.5 feet deep, diversion of the site flow to this swale will not cause overflow. In conclusion, the system presented in Figure 3 and previously described will mitigate the off -site problems that have been identified in this analysis withou ev- oading any of the existing downstream systems. 12 IEXPIRES . )i 1 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL FIGURE 3.5.1A 24 -HOUR DESIGN STORM HYETOGRAPH PERCENT OF TOTAL PRECIPITATION 8 5 4 3 2 1 0 0 180 360 540 720 900 1080 100 YEAR - 24 HOUR HYETOGRAPH SCS TYPE 1A DISTRIBUTION RESOLVED TO 10 MINUTE TIME STEPS 1260 1440 KING COUNTY, WASHINGTON, SURFACE..WATER DESIGN MANUAL FIGURE 3.5.4E SIMPLIFIED EXAMPLE OF INFLOW AND OUTFLOW HYDROGRAPH INFLOW (cfs) 7 INFLOW PEAK • 6.94cfs VOLUME = 100,000 cu ft Total Flow Reduction ../4 AO = (6.94 - 3.60) 334 cis VOLUME TO BE STORED = 34,490 cf . 4.0 cfs (maximum outflow desired) ..••■ Ow•• 7Itrrn.75-W-15tAK RATE = 3.60 cfs 1 I 1 1 i 1 I I 7 6 1 1 1 I 0 1 2 3 9 TIME (hours) 12 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL FIGURE 4.4.5A TYPICAL DETENTION TANK Optional Parallel Tank Access Risers (max spacing shown below) _ , �� - J _� %Type 2C6 Req'd for flow Inlet Pipe through System 2''mi'i' I I Only 't- _ t 1- - --d ..�' - -' r. 1----d Outlet Pipe Control Structure See Sectionl.4.7 • Plan View Access Riser Sae Figura4.4.58 NO SCALE "Flow Back Up" System Shown Optional Designs for "Flow Through" System and Parallel Tanks Shown Dashed 100' max. I 4 Access Risers See Figure4.4.5B 2" min. dia. air vent. Pipe welded Fo let k. r —u�a 0.5' Dead Storage LLtLtJJJJJ 2' max. Level 36" min. dia. (typ) Control Structure (PROP • T shown) min, 54" dia.. Type 2 CB See Sectionf .4.7 Detention Tank Size as req'd Section A —A NO SCALE ti 11 ) 1 -- 1 ..... • L j 2 max — -� NOTE, All metal parts corrosion resistant. Steel parts galvanized and asphalt coated (Treatment I or better) Type 2 CB Req'd for Flow Through System only 4.4.5 -3 11/92 FOSTERVIEW ESTATES PEAK RUNOFF SUMMARY* EXISTING CONDITIONS DEVELOPED CONDITIONS 2 -YR 10 -YR 25 -YR 100 -YR 2 -YR 1 Q -YR 25 -YR 100 -YR AREA 2 (to Southgate Park) 0.14 0.37 0.56 0.72 0.14 0.30 0.42 0.52 AREA 3 (to 43rd Ave culvert) n/a n/a n/a n/a 0.29 0.76 1.02 1.23 AREA 4 (to Borden property) 0.31 0.72 1.03 1.30 0 0 0 AREA 5A (to ravine) 0.23 0.60 0.90 1.18 0.24 0.56 0.82 1.04 TOTAL 0.68 1.69 2.49 3.20 0.67 1.62 2.26 2.79 *In cubic feet per second FUTURE IRA'NAGE EXISTING IOW INAGE --vata � 446 10 • TERRA ASSOCIATES, Inc. Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences Mr. Bill Fowler Dujardin Development Company P.O. Box 5308 9623 - 32nd Street SE Everett, Washington 98206 Subject: Updated Geotechnical Report Fosterview Estates Residential Plat South 137th Street and 44th Avenue South Tukwila, Washington Dear Mr. Fowler: December 22, 1992 Project No. T -1515 RECEIVED JUt4 ' 2 1995 COMMUNITY DEVELOPMENT As requested, we conducted a geotechnical engineering study for the proposed Fosterview Estates residential plat to be developed in Tukwila, Washington. The site is located west of the intersection of 44th Avenue South and South 137th Street and east of 42nd Avenue South. The approximate location of the project site is shown on the attached Vicinity Map, Figure 1. We initially conducted a study in 1990 and summarized our findings and recommendations in our report dated August 11, 1990. The purpose for the initial phase of our work was to explore subsurface soil conditions on the property in order to develop preliminary recommendations for: design, construction and grading of roadways; residential foundations; site preparation and earthwork construction. The purpose of our additional work was to explore subsurface conditions along the northern sloping margin of the site to provide geotechnical recommendations for development in this area. In a letter dated March 18, 1992, we had evaluated the stability of the closed portion of 44th Avenue and has provided conceptual means for stabilizing this part of the street alignment. In conducting the current study, we further evaluated the soil conditions along this alignment and examined alternative means of stabilization. We also conducted a wetland evaluation and the results were submitted in a separate report. 12525 Willows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821 -7777 Mr. Bill Fowler December 22, 1992 The scope of our recent work included observation of general site features, excavation of several test pits, laboratory tests, geotechnical engineering analyses and the updating of our initial geotechnical report (August 11, 1990). This updated report presents the results of both phases of our study, including recent findings, and summarizes our conclusions and recommendations. SUMMARY OF FINDINGS Our study indicates that the majority of the site is underlain by dense, glacially consolidated silts and till -like soils at depths of three to five feet below the ground surface. Near surface soils are loose to medium dense silty sands overlain by topsoil, duff and some peat in wetter portions of the site. In our recent test pits excavated along the northern margin of the site, hard and laminated silts and clays were encountered at depths below the surficial, overburden silty sand soils. Variable amounts of loose old fills and slide debris material were encountered in the four test pits excavated along the abandoned portion of 44th Avenue South. We anticipate that single - family residences to be constructed on the site can be supported on conventional spread footings bearing on the firm native soils existing at relatively shallow depths throughout the site or on structural fill placed over competent, native soils. Fill placement adjacent to the steeper slopes in the northern portion of the site should be minimized. If the work is to be performed during periods of heavy precipitation, shallow perched groundwater seepage is likely in areas where cuts of more than three or four feet are to be made. Hence, adequate measures for surface and subsurface drainage should be provided. Side debris and disturbed materials are present along the east edge of 44th Avenue. Our examination of conditions in this area confirmed the findings of our March 18, 1992 report. This report further discusses our conclusions and options for stabilizing this part of the roadway. The following sections of this report describe our initial and recent studies and present our recommendations in greater detail. PROJECT DESCRIPTION The site is located south of Southgate Park in Tukwila, Washington, between 42nd and 44th Avenues South. The approximate location is shown on the Vicinity Map, Figure 1. Based on the plans prepared by Charles Morgan and Associates, access for the residences will be provided by a main entry from 42nd Avenue South from the west side of the project which will extend and connect to existing S. 137th Street on the east side. Several residences along the western margin of the property will be accessed directly with driveways off the existing 42nd Avenue South. Project No. T -1515 Page No. 2 Mr. Bill Fowler December 22, 1992 Presently, it is planned to sub - divide the site into 41 single - family residential lots with associated roadways. Several areas along the southern half of the property have been designated as wetlands and no development is planned in these portions of the site. Based on the grading plans dated August 12, 1992, and the building finish floor elevation shown for the residences, significant grading work will be necessary to construct the plat roadways and building pads. Cuts and fills of up to fifteen feet will be required for the residences, roadways and driveways to be constructed on the site. The exact configurations or structural loads for the residences were not known at the time of our study. However, based on our previous experience with similar projects, we expect that perimeter load- bearing walls will carry one to two kips per lineal foot and that isolated spread footings will carry loads of 15 to 25 kips. Consideration is being given by the City of Tukwila to stabilizing and reopening the abandoned 44th Avenue alignment along the east side of the site. If any changes are made in the proposed construction as described above, and as project plans are being finalized, Terra Associates should be notified so that we can prepare supplementary recommendations, if necessary. FIELD EXPLORATION AND LABORATORY TESTING The initial phase of our field exploration was performed on July 25 and 26, 1990. Subsurface site conditions at that time were explored by excavating ten test pits using a trackhoe operated by Perkins Excavating of Woodinville, Washington. We also excavated eleven additional test pits on December 3, 1992 using a trackhoe operated by All Seasons Construction of Redmond. These additional test pits were excavated to explore the soil conditions along the northern margin of the property and the existing abandoned 44th Avenue South right -of -way. The approximate locations of all test pits are shown on the attached Exploration Location Plan, Figure 2. This figure is based on a Grading Plan prepared by Charles Morgan and Associates dated August 12, 1992. The locations of these test pits were determined by belt chain measurements and pacing from known points and site features shown on the survey plan and should be considered approximate only. Elevations of the test pits were determined by interpolation between contours shown on the plan, and are also approximate. The field explorations were monitored continuously by a geotechnical engineer from our firm who classified the soils encountered, maintained a log of each test pit, obtained representative soil samples and observed pertinent site features. All samples were visually classified in accordance with the Unified Soil Classification System described on Figure 3. The test pit logs are attached to this report as Figures 4 through 14. The soil classifications shown on these logs represent our interpretations of the field logs and reflect the results of visual examinations as well as laboratory tests performed on samples obtained from the test pits. Project No. T -1515 Page No. 3 Mr. Bill Fowler December 22, 1992 Representative soil samples collected from the test pits were placed in closed containers and returned to our laboratory for further examination and testing. Moisture content determinations were performed on all samples. In addition, we conducted sieve analyses and plasticity index tests on representative soil samples. The results of our laboratory tests are shown on the attached test pit logs and on Figures 15 through 17. SITE CONDITIONS Surface The nearly 10 acre property is located west of the intersection of 44th Avenue South and South 137th Street and east of 42nd Avenue South in Tukwila, Washington. The approximate location of the site is shown on Figure 1. The property is irregularly shaped, comprises an area of approximately 10 acres and is generally undeveloped. The site is moderately to heavily wooded and forested with second growth deciduous trees. There are also coniferous trees, generally consisting of alders, cottonwoods, cedars, and miscellaneous trees. There is also an open area in the central portion of the site which is presently covered by dense blackberries and nettles. The center of the property is bisected by a small, seasonal stream corridor which enters the property's southern boundary at approximately mid - point. This stream runs in a northeasterly direction and exits near the center of the eastern property line. There is also a small stream near the southeast property corner. Wetlands exist in each of the above drainage corridors and will remain undeveloped. The larger stream in the central portion of the site is flanked by moderately steep ravine slopes. A nursery is located directly south of the property, and several residences and Southgate Park are situated north of the site. The abandoned portion of 44th Avenue South runs in a northwesterly direction along the northern half of the east property boundary. Presently, this portion of the roadway is blocked off with guardrails at both ends, due to the ground movements that occurred several years ago in approximately the southern 300 feet. The site generally slopes down in a northeasterly direction with the exception of a ravine in the south - central portion of the site. The site slopes range between inclinations of approximately 25 to 30 percent. Elevations on the property range from about Elev. +234 near the southwest property corner to a low depression at about Elev. +110 near the northeast property corner. We noted evidence of standing water within the lower portions of the ravine and the area near the east - central portion of the site during our initial and recent site visits. The above topographic features are shown on the attached Figure 2. This figure is based on a Grading Plan by Charles Morgan and Associates dated August 12, 1992. Project No. T -1515 Page No. 4 Mr. Bill Fowler December 22, 1992 Subsurface As indicated by the test pits and visual observations, dense and hard silty till -like soils are present in the central and southern portions of the site at relatively shallow depths ranging between three and five feet. Above the till -like soils, there is a two to three foot thick layer of loose to medium dense overburden silty sand and a topsoil and duff layer. In Test Pits TP -8 and TP -9, which were excavated near the wet area of the site, the test pits encountered approximately two feet or so of peat -like soils. The total thickness of topsoil and loose silty sand overburden soils ranged between three and five feet. Hard, laminated silty clays and clayey silts were encountered below the till -like soils in Test Pits TP -1, TP-8, and TP -10. In our recent test pits excavated along the sloping, northern margin of the property, Test Pits TP -15 through TP -21, hard and very stiff silts and clays or a mixture of the two were encountered in all test pits, below the topsoil horizon and the underlying overburden silty sands. In Test Pits TP -11 through TP -14, which were excavated along the downhill side of the abandoned 44th Avenue South, variable amounts of fill were encountered, underlain by blocky and disturbed silts and clays which represent old landslide debris soils. The fill thickness ranged three to eight feet in these test pits and generally consisted of relatively loose and wet, silty sands. The test pits indicated that the depth of the slide debris ranged from about 11 feet to more than 14 feet. Hard clays were encountered near the bottom in Test Pits TP -13 and TP -14 below the blocky and disturbed soils. The cemented glacial till and till-like soils which were encountered in test pits excavated in the upper, southern portion of the site generally consisted of an unsorted mixture of silt, sand and gravel. The till is a relatively impermeable glacial soil deposited about 12,000 to 15,000 years ago, during the last glacial advance through the Puget Sound basin. Approximately 3,000 to 5,000 feet of glacial ice deposited the till and overlaid a succession of glacial sediments consolidating them to their present day dense consistencies. The approximate locations of the test pits are shown on Figure 2. More detailed information on subsurface conditions is presented on Figures 4 through 14. Groundwater No groundwater seepage was noted in any of our test pits during both phases of our field explorations. However, under wet weather conditions and during the rainy season, perched groundwater tables are likely to develop above the dense till -like soils and the hard relatively impermeable silts and clays observed on the site. Project No. T -1515 Page No. 5 Mr. Bill Fowler December 22, 1992 Slope Stability In their present configuration and with the native vegetative cover, the natural slope areas on the property are moderate and appeared to be generally stable. We did not observe any signs of slope instability on the site. The slopes are quite steep on the northern margins of the site and in an area along the east- central part of the site, just north of the designated wetland area. All grading work on site, particularly cut and fill operations where steep slopes are present, should be performed in conformance with recommendations given in this report to maintain stable conditions during and after construction. In particular, placement of fill soils on the steeper slopes in the northern portion of the site should be minimized. There is no evidence of movement on the slopes within the property itself, with exception of some minor surface erosion and sloughing within some of the steeper site slopes along the northern property margins. However, significant ground movements have occurred within recent years downhill from the northeastern margin of the property along the existing abandoned 44th Avenue South. Our observations and evaluation indicates that the portion of the road that has undergone movements was most likely constructed by cutting into the uphill side of the road and placing fills on the downhill portion of the roadway. It appears that the movement which occurred along the eastern edge of this road was caused by the fills placed to construct the roadway. The observed movements represent surficial movements of the fills placed during roadway construction and the underlying silt and clay soils which have become disturbed and blocky as a result of the movements. A more detailed discussion of our evaluation regarding the movements and repair alternatives are presented later in this report. Surface soils across the property will be subject to erosion where the ground surface is unprotected by vegetation or other physical erosion control devices. DISCUSSION AND RECOMMENDATIONS General Based on our study, it is our opinion that the proposed Fosterview Estates residential plat may be developed as planned, provided the recommendations presented in this report are incorporated into the project design and construction. The primary geotechnical feature which will influence the development and construction of the site is the significant grading that will be required on the site to construct roadways and building pads. Based on the grading plan, the roadways and the proposed building pads will require significant cuts and fills to achieve the desired final grades. Based on the finish grades and the finish floor elevations for buildings shown on the grading plan, we anticipate that cuts and fills of up to fifteen feet will be necessary to achieve the planned grades. Where cuts are needed to construct the roads, they must be made at stable inclinations. Project No. T -1515 Page No. 6 • Mr. Bill Fowler December 22, 1992 Native vegetation on the slopes should be protected from disturbance during construction. Permanent cut slopes up to eight feet high in the native undisturbed soils should be made at an inclination no steeper than 2:1 (Horizontal:Vertical). Cut slopes more than eight feet should not be steeper than 2.5:1. Fill slopes should also be made no steeper than 2:1. All fills placed over slopes greater than 25 percent in inclination (4:1) should also be keyed and benched into the slope. Fills in the northern portion of the site should be minimized but should be generally less than five feet thick. Surface water should be carefully controlled along the roadways and diverted away from the slopes. . The 44th Avenue alignment along the east side of the site has undergone movements along the southern 300 feet or so. The depths of the movements appear to exceed 14 feet. In our March 18, 1992 letter, we discussed various options for stabilizing this portion of the alignment. The conclusions presented in that letter continue to be valid. In our opinion, stabilization can be most effectively achieved by installing a row of soldier piles or drilled piers along the south side edge of the roadway. The following sections of this report present more detailed recommendations for the various geotechnical engineering aspects of this project. These recommendations should be incorporated into the project design and construction. Foundations The proposed residences may be supported on continuous and /or isolated spread footings bearing on the competent native soils present below the topsoil layers or on compacted structural fill. The near surface soils below the topsoil are loose in some areas. Hence, depending on the depth of excavation required to reach design footing grade, the native soils may need to be recompacted in place, or minor over - excavations may be needed for some foundations. Foundations for the residences on lots where slopes are greater than 25 percent should be embedded so that a minimum horizontal distance of ten feet is available between the outside edge of the footings and the adjacent slope face. Footings should extend to a minimum depth of 18 inches below the lowest adjacent outside finish grade. Continuous and individual spread footings may be designed for an allowable bearing pressure of 2,000 pounds per square foot (psf). A minimum width of 12 inches should be used for continuous footings and individual spread footings should have a minimum size of 18 inches. A one -third increase in the above bearing pressures may be used when considering wind or seismic loads. All footings should be provided with steel reinforcement in accordance with structural requirements. Project No. T -1515 Page No. 7 # • Mr. Bill Fowler December 22, 1992 Retaining and Lower Level Basement Walls Lower level basement walls should be designed as structural retaining walls supporting the pressure imposed by an equivalent fluid weighing 40 pounds per cubic foot (pcf). Walls restrained from free movement at the top should be designed for an additional uniform pressure of 100 psf. Lateral pressures may be resisted by passive pressures acting against foundations. An equivalent fluid weight of 300 pcf may be used when footings are poured neat against undisturbed native soils or against structural fill. In addition, a friction factor of 0.35 between concrete and soil may be used. These are ultimate values. An appropriate safety factor should be used in the computations. We recommend a safety factor of at least 1.5. Settlements We anticipate that the total settlements for structures supported on the competent native soils or on adequately compacted structural fill will be less than one -half inch. The anticipated long -term differential settlement should be less than one - quarter inch. The majority of the settlements should occur during construction. Slabs -On -Grade Concrete floor slabs, where used, may be constructed as slabs -on -grade supported either on the competent native soils or on structural fill. We recommend that four inches of a free- draining gravel such as 1/4 to 3/8 inch pea - gravel be placed below the slab to act as a capillary break. In addition, a plastic membrane with a thickness of ten to twelve mils may be placed above the gravel to act as a vapor barrier for additional moisture protection. Lot Drainage Surface gradients on the individual lots should be created to direct runoff away from the residences and away from slopes toward suitable discharge facilities. Perimeter foundation drains should be installed and tightlined away from the buildings. Drains should be at the levels of footing bottoms or below the crawl space level, whichever is lower. Roof gutter drains should be separately tightlined away from the structures. All drains should be discharged into the storm drain system. All drains should be provided with cleanouts at easily accessible locations. These cleanouts should be serviced at least once every year. Project No. T -1515 Page No. 8 Mr. Bill Fowler December 22, 1992 Roadway Construction Roadways for the proposed development may be constructed on the recompacted native soils below the surficial vegetation and topsoil, or on compacted structural fill. Structural fill should be placed after stripping the pavement areas of vegetation, topsoil and any debris, depending on the depth of cuts or fills required to reach design grades. Where structural fill is placed, the upper twelve inches of the subgrade should be compacted to 95% of the maximum dry density as determined by ASTM D -698 (Standard Proctor). Recommendations for cut and fill slopes are included later in this report. All subgrade areas should be in a stable, non - yielding condition prior to paving. The use of a layer of Asphalt Treated Base (ATB) to protect the subgrade during construction should be considered if the work will be performed during wet weather. As a minimum, we recommend that pavements on the site consist of 2 inches of asphalt over 6 inches of crushed rock base. Where fills are placed in roadways crossing slopes steeper than 25 percent, a "key" should be excavated at the toe of the sides of the roadway fills and should extend at least two feet into competent native soils. The key should also extend laterally at least two feet outside the limits of fill placement. This keyway excavation should be proofrolled. However, if water is noted, proofrolling should be avoided. If groundwater or water from the existing stream at the bottom of the ravine is noted during excavation of the key, a free- draining blanket of clean crushed rock should be provided at the bottom of this excavation in order to allow a firm working surface and allow future drainage. The final slope face on the roadsides should be densified by compaction with a dozer or roller and should not be any steeper than the recommended 2:1. We recommend planting or hydroseeding the face of both cut and fill slopes in order to reduce the erosion potential of the slope areas. Slopes Permanent cut slopes less than eight feet high and fill slopes elsewhere at the site should also be constructed with a finish inclination of 2:1 or flatter. In the northern portion of the site, fills placed on the steep slopes should be minimized and should not be more than five feet thick. Cuts greater than eight feet in height should be at an inclination of 2.5:1 or less. Fills should be placed in thin layers and compacted to at least 95% relative compaction as determined by ASTM Test Designation D -698 (Standard Proctor). Each layer should be "benched" into the native soil slope where slopes exceed 25 percent. Surface water should not be allowed to flow over the face of any slope. As soon as possible after construction, permanent exposed slopes should be planted with an appropriate plant mix or provided with physical protection from erosion. Temporary slopes may be made at an inclination of 1:1. Project No. T -1515 Page No. 9 Mr. Bill Fowler December 22, 1992 Site Preparation and Grading The building and pavement areas should be stripped and cleared of vegetation, topsoil and debris. The stripped topsoils may be used as berms, for landscaping or in non - structural areas, if desired. Following stripping, any loose areas noted should be over - excavated and replaced with structural fill or clean crushed rock to a depth that will provide a stable base. Adequate erosion control measures should be implemented during earthwork construction on the site. Structural fill should be placed in thin layers and compacted to at least 95 percent of the maximum dry density in accordance with ASTM Test Designation D -698 (Standard Proctor). The majority of the site native soils are high in fines content making them impossible to compact during rainy weather or when placed over existing moist conditions. Any import soils to be utilized should first be examined by the soils engineer for use as a structural fill. We suggest that clean import fills contain no more than 2 percent "fines" passing through No. 200 sieve on the portion passing the 3/4 inch screen. Structural fill should be placed in horizontal layers not exceeding twelve inches in loose thickness. Fills placed on the slopes greater than 25 percent should be keyed and benched into the slopes. Utilities Where utility lines are to be excavated and installed in the roadways, we recommend that all bedding and utility construction be in accordance with APWA and City of Tukwila specifications. Fill and backfill placement and compaction should be in accordance with the recommendations given earlier in this report. It is likely that trenches made over four feet in depth during winter will encounter perched groundwater conditions. The site soils contain significant amounts of fines and are considered to be moisture sensitive. It is recommended that clean granular fill material be imported for use as backfill in the utility trenches, particularly if work is performed in wet weather. Evaluation of Stability - Abandoned Portion of 44th Avenue South We evaluated the existing subsurface conditions along the abandoned portion of 44th Avenue South by excavating four test pits along the downhill side of this roadway. Our evaluation indicates that this part of the roadway was constructed by making excavations along the uphill side of the road and placement of excavated soils on the downhill side of the road. Placement of these soils apparently caused movements of the underlying fine grained soils. Evidence of this movement is clearly visible at the site along the east edge of the roadway. Project No. T -1515 Page No. 10 Mr. Bill Fowler December 22, 1992 Native soils on the hillside in this area are clayey in nature and the upper portion of these materials exhibits a disturbed and blocky nature of a result of the above movements. The depth of the apparent landslide debris encountered in our test pits ranged from about 11 feet in Test Pit TP -13 to more than 14 feet in Test Pits TP -11 and TP -12. We also observed conditions along the drainage ravine which exists along the east side of the roadway. Near the southern end, a culvert discharges into the ravine and has obviously caused considerable amounts of erosion in the ravine bottom. This erosion can result in long term undercutting of the slope which could be further detrimental to slope stability. In our earlier letter dated March 18, 1992, we discussed the conditions existing in this area and discussed conceptual means for repair /stabilization based on our visual observations and our estimates of depth of slide debris. Our recent explorations in this area by excavating test pits confirmed our estimates of the depths and types of slide debris. Therefore, the conclusions presented in our earlier report continue to be applicable. In discussion with the developer, we have been advised that excessive costs and risk of development to re -open 4-4th Avenue South are not feasible for the project and should not be recommended. Additional Services It is recommended that we be provided the opportunity for a general review of the final design and specifications in order that earthwork and foundation recommendations may be properly interpreted and implemented in design and construction. The analyses and recommendations submitted in this report are based upon the data obtained from the test pits excavated on the site. The nature and extent of variations in the test pits may not become evident until construction. If variations then appear evident, we should be requested to reevaluate the recommendations presented in this report prior to proceeding with construction. It is also recommended that we be retained to provide geotechnical services during construction. This is to observe compliance with the design concepts, specifications, and recommendations; and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. We recommend that Terra Associates, Inc. provide the following services during construction: 1. Examine all stripped subgrade areas and the proofrolling operations prior to the start of fill placement or earthwork. 2. Examine all cut slopes and excavations to verify that conditions are as anticipated. 3. Examine all foundation and slab areas prior to forming and concrete placement to evaluate that adequate foundation support is available. Project No. T -1515 Page No. 11 • ■ Mr. Bill Fowler December 22, 1992 ' 4. Perform field density testing of structural fills as needed during placement and observe the grading and earthwork operations. We request that a minimum of two working days' notice be given to schedule our services during construction. The following figures are included and complete this report: Figure 1 Figure 2 Figure 3 Figures 4 through 14 Figure 15 Figures 16 and 17 Vicinity Map Exploration Location Plan Soil Classification Test Pit Logs Grain Size Analysis Plasticity Index Test Results This report has been prepared in accordance with generally accepted geotechnical engineering practices and has been revised to reflect our recent findings. It is the property of Terra Associates, Inc. No other warranty, expressed or implied, is made. It is intended for specific application to this project and for the exclusive use of the Dujardin Development Company and their representatives. We trust the information presented herein is adequate for your requirements. If you need additional information or clarification, please call. Sincerely yours, TERRA ASSOCIATES, INC. Mehrdad Moini Geotechnical Engineer Anil Butail, P.E. President MM /AB:tw / /2 /92 • cc: Charles Morgan and Associates Project No. T -1515 Page No. 12 .SICWIIF 4! 3 3 t,1 47" • 4,,L. KV.1.. • .• t11414i 'f7.1 4WW1 I • • I • I Itiilet4I :all f .11 • glreuR, V 4114' 1 • •• 'TT La. S 10EloW SW 1141. tf1 V.—ST - • t:r• Sr 111711 PL -7 • _ Br441S ST Txitv EJ' h z2.0 WitOGrOw• 1444 St. 1 BT. ST 13414 SW • 351% S 135,“ ST F, laST).14 IT. 1014 X et t THIS FIGURE IS COPIED FROM PAGE 33 OF THOMAS BROTHERS MAP OF KING COUNTY. TERRA ASSOCIATES Geotechnical Consultants VICINITY MAP Fosterview Estates Tukwila Washington Proj. No. 1515 I Date 12/92 I Figure 1 REFERENCE : GRADING PLAN BY CHARLES MORGAN & ASSOCIATES DATED AUGUST 12. 1992. ,.i1 TERRA ASSOC Geotechnica LEGEND : APPROXIMATE TEST PIT LOCATION & NUMBER SCALE : 0 50 100 200 FEET TERRA ASSOCIATES Geotechnical Consultants EXPLORATION LOCATION PLAN Fosterview Estates Tukwila Washington Proj. No. 1515 Date 12/92 Figure 2 I. MAJOR DIVISIONS LETTER SYMBOL GRAPH SYMBOL TYPICAL DESCRIPTION COARSE GRAINED SOILS More than 50% material larger than No. 200 sieve size. GRAVELS 50% More than of fraction is larger than No. 4 sieve. Clean Gravels (less than 5% fines) GW 'Q: O.•. •Q•p• . Well-graded gravels, gravel -sand mixtures, little or no fines. GP 1 1 ` Poorly- graded gravels, gravel -sand mixtures, little or no fines. Gravels with fines GM ~ • , • 3 . .1 rr Silty gravels, gravel- sand -silt mixtures, non - • plastic fines. F. 'i Clayey gravels, gravel- sand -clay mixtures, plastic ,e,, %^ fines. SANDS More than 50% of coarse fraction is smaller than No. 4 sieve. Clean Sands (less than 5% fines) SW ' •'" ''` Well raced sands, ;t ;7_, : ;., ,� $ gravelly sands, little or _4_ "- ,-� %' 4'; no fines. SP Poorly- graded sands or gravelly sands, little or no fines. Sands with fines SM a .. . ,: '. ii t / Silty sands, sand -silt mixtures, non - plastic fines. SC : " F; ,.{,r Clayey sands, sand-clay mixtures, plastic fines. FINE GRAINED SOILS More than 50% material smaller than No. 200 sieve size. SILTS AND CLAYS Liquid limit is Tess than 50% ML Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey sifts with slight plasticity. CL Inorganic clays of low to medium plasticity, gravelly �� / / / / clays, sandy clays, silty clays, lean clays. / /i OL 1 I I 1 Organic silts and organic clays of low plasticity. SILTS AND CLAYS Liquid limit is greater than 50% MH III Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic. CH 0/. Inorganic clays of high plasticity, fat clays. OH I I Organic clays' of medium to high plasticity, organic silts. HIGHLY ORGANIC SOILS PT A Peat and other highly organic soils. DEFINITION OF TERMS AND SYMBOLS SAND or GRAVEL 1 Standard Penetration Density Resistance in Blows /Foot 2" OUTSIDE DIAMETER SPLIT I SPOON SAMPLER I 2.4" INSIDE DIAMETER RING SAMPLER OR SHELBY TUBE SAMPLER P SAMPLER PUSHED ' * SAMPLE NOT RECOVERED Q WATER LEVEL (DATE) Lj WATER OBSERVATION STANDPIPE C TORVANE READINGS, tsf qu PENETROMETER READING, tsf W MOISTURE, percent of dry weight pcf DRY DENSITY, pounds per cubic foot LL LIQUID LIMIT, percent PI PLASTIC INDEX N STANDARD PENETRATION, blows per foot Very loose 0-4 Loose 4-10 Medium dense 10-30 Dense 30-50 Very dense >50 SILT or CLAY Standard Penetration Density Resistance in Blows /Foot Very soft 0-2 Soft 2-4 Medium stiff 4-8 Stiff 8-16 Very stiff 16-32 Hard >32 SOIL CLASSIFICATION SYSTEM Fosterview Estates Tukwila, Washington TERRA et,-:--Pr, ..), ,�.,,,,, ■ ���� ASSOCIATES Geotechnical Consultants Proj. No. T -1515 Date 12/92 Figure 3 Logged By MM Date 7 -25 -90 Depth (ft.) 1 USCS TEST PIT NO. TP -1 Soil Description El0v +158± — __ __ — _ — — - -- — _• 12 to 14 inches Topsoil and Duff, damp, very loose. 36.2 31.0 _, S SM Reddish-tan, silty fine SAND with many roots, damp, loose becomes medium dense. Tan, silty SAND with sane roots, damp, loose SA/ ML Tan, fine sandy SILT, damp, medium dense. • Grades into: ML Tan -gray, fine sandy SILT to SILT with sane stains, moist, dense and hard. ML/ CL Blue—gray, clayey SILT, moist, very hard. Test Pit terminated at 12.2 feet. No groundwater seepage encountered. TEST PIT NO. TP -2 Logged By M1 Date 7-25 -90 1 1 Elev +174± 5— SM/ Tan -gray, silty fine SAND to fine sandy SILT at Lower — ML depths, cemented, damp, dense to very dense (7W -like). 19.2 • i— (becomes less cemented at bottom) —, Test Pit terminated at 11.1 feet. — No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants • TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 Date 8/90 Figure 4 Brown, silty Topsoil and Duff, damp, very loose. _, S SA T Tan, silty SAND with sane roots, damp, loose TERRA ASSOCIATES Geotechnical Consultants • TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 Date 8/90 Figure 4 1 Logged By T1 Date 7 -25-90 Depth (ft.) USCS 1 TEST PIT NO. TP -3 Soil Description Elev +164± w ( %) 0- Test Pit terminated at 10.4 feet. — No groundwater seepage encountered. Logged By MI Date 7-25 -90 1 TEST PIT NO. TP -4 Elev +171± 12 inches silty Topsoil and Duff, damp, very loose. S,1 Tan - brown, silty fine SAND, damp to dry, loose. — SM Red- tan, silty the SAND, damp, median dense. Grades into: i— S`1/ Tan -gray, silty fine SAND to fine sandy SILT, damp, —' ML becanes Hoist, slightly cemented, dense (Till like). 23.4 0— Test Pit ternrinated at 8.9 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 Date 8/90 Figure 5 Dark brown Topsoil and Duff, damp, very loose. 22.3 __ S SM B Brown becomes red-tan, silty fine SAND with score roots, damp, loose becanes medium dense. i M SM/ T Tan, silty fine SAND, slightly cemented, damp to moist, Logged By MI Date 7-25 -90 1 TEST PIT NO. TP -4 Elev +171± 12 inches silty Topsoil and Duff, damp, very loose. S,1 Tan - brown, silty fine SAND, damp to dry, loose. — SM Red- tan, silty the SAND, damp, median dense. Grades into: i— S`1/ Tan -gray, silty fine SAND to fine sandy SILT, damp, —' ML becanes Hoist, slightly cemented, dense (Till like). 23.4 0— Test Pit ternrinated at 8.9 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 Date 8/90 Figure 5 TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 Date 8/90 Figure 5 • Logged By nil Date 7-26-90 Depth (ft.) USCS 1 TEST PIT NO. TP -5 Soil Description Elev +181± W. ( %) -" v lb inches dark brown '.l'opsoil and silty 'Topsoil, clamp, 20.7 Q.1 R Red -tan, silty fine SAND, damp, loose to medium dense. Sill T Tan -gray, silty fine SAND to fine sandy SILT with SMV G Gray, fine sandy SILT with few scattered gravels and 2 Logged By M4 Date 7- 26-90 1 TEST PIT NO. TP -6 Bev ._ +204+ 12 inches dark brown Topsoil and Duff, damp, very loose. - 9K Tan, silty fine SAND with some roots, damp, loose. - al Tan with red stains, silty SAND with gravel, damp, �� slightly cemented, medium dense (Weathered Till). - Sy/ Tan- gray, silty, gravelly SAND with some cobbles, -` SW highly cemented, dame, very dense (1i11) 8.4 - SM/ Tan, fine sandy SILT with few gravel on top, and a - `'� ML pocket of blue -gray SILT, damp to moist, dense to p -- --- very dense (1111-like). - Test Pit terminated at 10.8 feet. - No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 I Date 8/90 I Figure 6 TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 I Date 8/90 I Figure 6 Logged By At1 Date 7 -26-90 Depth (ft.) 1 USCS TEST PIT NO. TP -7 Soil Description Elev +1$2± W ( %) __ 1 12 co 14 inches dark brown Topsoil and Duff, moist, v. loose. 18.4 — s --- g sm T Tan -red, silty fine SAND with some roots and few ' -. 1 SP1 T Tan, gravelly, silty SAND with stains and few cobbles, SM T Tan -gray, gravelly, silty fine SAND to fine sandy SILT with scattered cobbles, cemented, moist, very dense (Till). Test Pit terminated at 8.6 feet. TEST PIT NO. TP -8 Logged By PT1 Date 7-26 --90 1 1 Elev +210± — pT winch dark brown PEAT, wet,. very soft-. — SM Reddish -tan, silty fine SAND with many Iron -Oxide stairs, ....... moist, loose. 5— SM Tan-brown to tan, mottled, gravelly, silty fine SAND to 15.3 _, to fine sandy SILT, becomes tan-gray in color, moist, dense. — SMA,IL . _~ ML Blue gray, fine sandy SILT to SILT, moist, dense and 24.5 I- - Test Pit tenxxnated at 9.7 feet. — No groundwater seepage encountered. TERRA sa . ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 1 Date 8/90 I Figure 7 TERRA sa . ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 1 Date 8/90 I Figure 7 Logged By NM Date 7 -26-90 Depth (ft.) 1 USCS TEST PIT NO. TP -9 Soil Description Bev +21n w (o/u) __ P PT 1 16 -inch peat -like Topsoil, wet to moist, very soft. 22.5 S'1 T Tan - brown, silty fine SAND with roots, moist, loose. SCl/ML T Tan -red, silty fine SAND to fine sandy SILT with stains, yy/ B Blue -gray; silty fine SAND to fine sandy SILT with TEST PIT NO. TP -10 Logged By NM Date 7- 2&-9f1 1 1 Elev +201+ 12 inches dark brown silty Topsoil, damp, loose. _ S1 Tan - brown, silty fine SAND with some roots, damp, t loose. S1/ Tan, silty fine SAND became fine sandy SILT, damp, 5— ML median dense becomes dense (Weathered Till. to Till -like) . 18.0 -,� HL — ML/(L Blue-r-ay STET to clayey SILT, damp to moist, hard. _, 25.0 P— Test Pit terminated at 8.4 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 I Date 8/90 l Figure 8 TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. 1515 I Date 8/90 l Figure 8 • Logged by: MM Date: 12 -3-92 Depth USCS/ (ft.) Graph 0 5 10 15 Test Pit No. TP -11 Soil Description Approximate Elev. +142 W Logged by: MM Date: 12 -3-92 Depth (ft.) USCS/ 0 Graph 5 10 No groundwater seepage encountered. Test Pit No. TP -12 Soil Description Approximate Elev. +137 W ( %) 15 Dark brown, silty SAND with occasional gravel, moist, loose (Fill). 12.6 Tan, silty SAND with scattered small gravel, moist, medium dense. Tan, mottled, blocky silty CLAY, moist to wet, medium stiff (slide debris). Test pit terminated at 14.0 feet. N dw o groun ater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T-1.515 1- Date 12/92 Figure 9 s sM1 • Brown, gravelly, silty SAND to silty SAND, moist, loose (1911). 33.3 qu =2.0 tsf . SM ; Tan, silty SAND with old branches, etc., moist, _ 49 5, loose to medium dense (1911). . ML CL ` Tan, mottled, clayey SILT becomes silty CLAY, blocky and disturbed, moist becomes wet, /ll CL //, medium stiff (Old slide debris). (becomes more moist and clayey) Test pit terminated at 14.0 feet, Logged by: MM Date: 12 -3-92 Depth (ft.) USCS/ 0 Graph 5 10 No groundwater seepage encountered. Test Pit No. TP -12 Soil Description Approximate Elev. +137 W ( %) 15 Dark brown, silty SAND with occasional gravel, moist, loose (Fill). 12.6 Tan, silty SAND with scattered small gravel, moist, medium dense. Tan, mottled, blocky silty CLAY, moist to wet, medium stiff (slide debris). Test pit terminated at 14.0 feet. N dw o groun ater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T-1.515 1- Date 12/92 Figure 9 Logged by: MM Date: 12 -3-92 Depth USCS/ (ft.) 0 Graph 0 5 10 15 Test Pit No. TP -13 Soil Description Approximate Elev. +129 W ,,.... .— ,".' � 7 I- •f. Lii h i 4 } Brown, silty SAND, damp to moist, loose (FiII). (Topsoil on top) 33.6 to tsf to 3 ts qu=4,5tsf ;s• SM hill ; 4 Brown and tan, gravelly, silty SAND, moist, loose (Fill). Red-brown to tan, silty fine SAND, moist, medium dense. 't ia Tan -gray, mottled, blocky, silty CLAY, moist, medium stiff (slide debris). / /�� /// ACL f// Tan, silty CLAY, bedded, moist becomes damp, hard. Test pit terminated at 14.0 feet. Logged by: MM Date: 12 -3-92 Depth USCS/ i 0 Graph 0 5 10 15 No groundwater seepage encountered. Caving within upper 7 feet. Test Pit No. TP -14 Soil Description Approximate Elev. +120 W Test pit terminated at 15.0 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T -1515 I Date 12/92 Figure 10 c q i. SM t£ kS Brown, silty SAND, damp to moist, loose (FiII). (Topsoil on top) 26.7 36.7 27.0 qu >4.5 tsf qu >4.5 tsf Dark brown, old silty Topsoil, moist, loose. g SM Red-brown to tan, silty fine SAND, moist, medium dense. 't ia Tan, mottled, fine sandy SILT, with stains, damp, medium dense. Grades into: Tan, clayey SILT becomes silty CLAY, moist, bedded, very stiff and hard. / � ) Cr� L / Blue -gray, silty CLAY, damp to moist, bedded, hard. Test pit terminated at 15.0 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T -1515 I Date 12/92 Figure 10 • • Logged by: MM Date: 12 -3-92 Depth USCS/ (ft.) 0 Graph 0 5 10 15 Test Pit No. TP -15 Soil Description Approximate Elev. +142 W Logged by: MM Date: 12 -3-92 Depth USCS/ (ft.) Graph 0 5 10 15 Test Pit No. TP -16 Soil Description Approximate Elev. +128 W 12- inches dark brown Topsoil and Duff, moist, very loose. 18.7 28.2 25.2 qu=4.5 tsf y - I t, � it Red - brown, silty SAND with roots, damp to moist, loose. y,.,; i'4 •i a . Tan -gray, mottled, silty SAND with occasional gravel, Iron -Oxide stains, slight cementation, moist, medium dense and dense (Weathered Till - like). n% Tan -brown, mottled, silty SAND with occasional gravel, moist, medium dense. - Tan, SILT becomes clayey SILT, moist to damp, hard. Tan, fine sandy SILT to SILT, damp, dense and hard. Rev Blue -gray, silty CLAY, moist, hard. Test pit terminated at 13.0 feet. No groundwater seepage encountered. Logged by: MM Date: 12 -3-92 Depth USCS/ (ft.) Graph 0 5 10 15 Test Pit No. TP -16 Soil Description Approximate Elev. +128 W TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T -1515 I Date 12/92 Figure 11. 14-inches dark brown, Topsoil and Duff, moist, soft. 13.6 27.5 qu >4.5 tsf . J R.., i 4q, Red -brown, silty SAND with roots, moist, loose. (Occasional angular cobbles) IR. 1. .,p. ta :IE,;; "--"' , i ,° i%i l- a . Tan -gray, mottled, silty SAND with occasional gravel, Iron -Oxide stains, slight cementation, moist, medium dense and dense (Weathered Till - like). e// CL � - Tan, SILT becomes clayey SILT, moist to damp, hard. Test pit terminated at 12.0 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T -1515 I Date 12/92 Figure 11. by: MM Date: 12 -3-92 Depth USCS/ (0 Graph 0 Test Pit No. TP -17 Soil Description Approximate Elev. +138 W ( %) 14 to 16- inches dark brown , Topsoil and Forest Duff, moist, soft. 5— 10 15 Brown, silty fine SAND with many large roots, moist, loose. ML Tan, laminated SILT with trace of clay, becomes clayey SILT, damp, very hard. (Grades into:) Tan, mottled, silty CLAY, blocky with stains, moist, hard. 31.6 31.5 qu >4.5 tsf qu >4.5 tsf Test pit terminated at 11.2 feet. No groundwater seepage encountered. Logged by: MM Date: 12 -3-92 Depth (ft.) USCS/ 0 Graph 5 10 15 Test Pit No. TP -18 Soil Description Approximate Elev. +158 W - _ - — - • 14-inches dark brown, Topsoil and Forest Duff, moist and wet, very soft.. 31.9 30.6 qu >4.5 tsf qu>4.5 tsf ` SM ' me uiI! FrAA tY . >! Brown, silty fine SAND with many large roots, moist, loose. Tan, mottled, clayey SILT, massive, damp, very hard. (becomes more moist) 1 ML II Blue -gray SILT with trace of clay, damp to moist, hard. - - • Test pit terminated at 12.0 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T -1515 Date 12/92 Figure 12 Logged by: MM Date: 12 -3-92 Depth USCS/ (0 Graph 0 5 10 15 Test Pit No. TP -19 Soil Description Approximate Elev. +166 W ( %) 14 to 16- inches dark brown Topsoil and Forest Duff, moist, soft. IML) Red -brown becomes tan, fine sandy SILT to silty fine SAND with many roots, moist, loose. Light -tan, SILT with trace of fine sand becomes SILT, with stains, damp, medium stiff. . Tan, SILT with trace of fine sand, damp, very hard. Dark gray, silty CLAY to CLAY, with dark brown, Iron -Oxide stains, moist, hard. 14.3 21.3 29.5 qu"4.5 tsf Test pit terminated at 12.5 feet. No groundwater seepage encountered. Logged by: MM Date: 12 -3 -92 Depth USCS/ (ft.) Graph 0 Test Pit No. TP -20 Soil Description Approximate Elev. +174 W ( %) 16 to 18- Inches dark brown, Topsoil and Forest Duff, moist, very soft. 15 Red-brown and brown, silty fine SAND with many roots, moist, loose. Tan, mottled, fine sandy SILT, damp, loose becomes medium dense. Tan, SILT with trace of fine sand, damp, hard and dense. Blue -gray, clayey SILT becomes silty CLAY, moist, very stiff to hard. 18.0 18.0 29.1 qu -3.5 to 4 tsf Test pit terminated at 13.5 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consuttants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T-1515 I Date 12/92 Figure 13 Logged by: MM Date: 12-3-92 Depth (ft.) USCS/ 0 Graph 5 10 15 Test Pit No. TP-21 Approximate Elev. +170 Soil Description 1Sr TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T-1515 Date 12/92 Figure 14 164nches dark brown-black Topsoil and Forest Duff, moist, very soft. 16.9 30.6 SM • lir Brown, silty fine SAND with many large roots, moist, loose. griu- IrOOP .411141111 Tan-brown, mottled, fine sandy SILT to silty fine SAND with stains, moist, loose to medium dense. 1 Tan, SILT, damp, hard. ML l. CL f Blue-gray, silty CLAY to CLAY, moist, very stiff. Test pit terminated at 12.0 feet. No groundwater seepage encoutnered. 1Sr TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS Fosterview Estates Tukwila, Washington Proj. No. T-1515 Date 12/92 Figure 14 N 100 SIEVE ANALYSIS HYDROMETER ANALYSIS SIZE OF OPENING IN INCHES 1 NUMBER OF MESH PER INCH, U.S. STANDARD 1D V C) N 90 80 0 m N ((D c -n O C ▪ ♦V CD y m 7 N ED o � CD Cn .o m 73 70 n m z --I -n z m 50 X1 w 40 m_ 5 30 2 60 20 10 r w n V o o 0 0 8 N V 1D GRAIN SIZE IN MM o �b § 0 O $ o O t N O CO 103 V t0') N 0 CO t3 V M 1 1 1— 0 10 20 30 N m 43 V CSI N GRAIN SIZE IN MILLIMETERS I COBBLES I COARSE f FINE GRAVEL t [ COARSE 1 MEDIUM I SAND FINE Key Boring or Test Pit TP -16 Depth (ft.) 5.0 USCS S CO 0 1 13 0 O O O O O O FINES 0 Description sandy SILT with gravel Moisture Content ( %) 13.6 40 50 60 70 80 90 LL 100 HOI3M A8 d3SE VO0 1N3 - PL PLASTICITY CHART O . CH PLASTICITI o 0 0 c "PV OH CI or MH CL ML '4l • -tit •4 '''•'`' ML L ' �■ v 0 10 20 30 40 50 60 70 80 90 100 110 120 LIQUID LIMIT ( %) • PLASTICITY DATA KEY SYMBOL HOLE NUMBER DEPTH ( feel) NATURAL WATER CONTENT W( %) PLASTIC LIMIT ( %) LIQUID LIMIT ( %) PLASTICITY INDEX ( %) LIQUIDITY INDEX ( - PL UNIFIED SOIL CLASSIFICATION SYMBOL LL-PL i • R TP -11 TP -13 TP -15 9.5 10.0 8.0 33.3 33.6 28.2 25.0 23.0 0. 35.5 34.5 26.0 10.5 11.5 26.0 0.7905 0.9217 1.0846 ML /CL CL ML Fosterview Estates Tukwila Washington TERRA ASSOCIATES Consultants ::::..irsesi IZIAOr Geotechnical Proj. No. 1515 1 Date 12/92 Figure 16 • • PLASTICITY CHART CH PLASTIC ITl o 0 fi w OH CL or MH CL ■ ML L. • v _ 0 10 20 30 40 50 60 70 80 90 100 110 120 LIQUID LIMIT ( %) . jI PLASTICITY DATA KEY SYMBOL HOLE NUMBER DEPTH (feet) NATURAL WATER CONTENT w( %) PLASTIC LIMIT ( %) LIQUID LIMIT ( %) PLASTICITY INDEX ( %) LIQUIDITY INDEX ( - PL UNIFIED SOIL CLASSIFICATION SYMBOL LL -PL) • A . • TP -18 TP -20 TP -21 11.0 4.0 11.0 30.6 18.0 30.6 26.5 22.0 22.0 35.0 25.0 37.0 8.5 3.0 15.0 0.4824 — 1.3333 0.5733 ML ML CL TERRA ASSOCIATES Fosterview Estates Tukwila Washington :' `��mami \i► Proj. No. 1515 I Date 12/92 J Figure 17 Geotechnical Consultants -.__1 TERRA ASSOCIATES, Inc. Consultants in Geotechnical Engineering, Geology and Environmental Earth Sciences Mr. Bill Fowler Dujardin Development Company P.O. Box 5308 9623 - 32nd Street SE Everett, Washington 98206 Subject: Geotechnical Engineering Study Proposed 10 Acre Residential Plat South 137th Street and 44th Avenue South Tukwila, Washington Dear Mr. Fowler: August 11, 1990 Project No. T -1515 RECEIVED JUN `2 1995 COMMUNITY DEVELOPMENT As requested and in accordance with our proposal dated June 30, 1990, we have conducted a geotechnical engineering study for your proposed residential plat to be developed in Tukwila, Washington. The site is located west of the intersection of 44th Avenue South and 137th Street and east of 42nd Avenue South. The approximate location of the project site is shown on the Vicinity Map, Figure 1. The purpose of our work was to explore subsurface soil conditions on the property in order to develop recommendations for design and construction and grading of roadways, residential foundations, site preparation and earthwork construction. We are also conducting a wetland evaluation and the results will be submitted in a separate report. The scope of our work included observation of general site features, backhoe excavated test pits, laboratory tests, geotechnical engineering analyses and the preparation of this report. This report presents the results of our study and summarizes our conclusions and recommendations. SUMMARY OF FINDINGS Our study indicates that the majority of the site is underlain by dense, glacially consolidated silts and till -like soils at depths of three to five feet below the ground surface. Near surface soils are loose to medium dense, silty sands overlain by topsoil and duff and some peat in wetter portions of the site. 12525 Willows Road, Suite 101, Kirkland, Washington 98034 • Phone (206) 821 -7777 . REFERENCE : BOUNDARY & TOPOGRAPHIC SURVEY PLAN BY HEBRANK & ASSOCIATES DATED APRL 8, 1990. TE AS Geote • "Je/'t -97•! J'•a -o 0 ,r•..,.s, ••.r• not - ..,•.• ...4•99.5 !t' J••••a a.. • ., s.:;;t � •II a'M•wL 990. •J.. •- '•t/. o/•tJ.e1C r••••c.00' • LEGEND : APPROXIMATE TEST PIT LOCATION AND NUMBER SCALE : 0 50 100 200 FEET APPROXIMATE TERRA ASSOCIATES Geotechnical Consultants EXPLORATION LOCATION PLAN 10. Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 Figure 2 MAJOR DIVISIONS GRAVELS 0) J O a 0 r N a) L7) 7a 0 CC o 'En- o 0 o 0 W c c'j CC - z° a 0 o More than 50 °k of coarse fraction is larger than No. 4 sier _. SOIL CLASSIFICATION SYSTEM LETTER GRAPH SYMBOL SYMBOL TYPICAL DESCRIPTION GW a' Weli- graded gravels, gravel -sand mixtures, �'`•�'; little or no fines. Clean Gravels (less than 5% fines). GP Poorly- graded gravels, gravel -sand mixtures, little or no fines. Gravels with fines. GM GC Silty gravels, gravel- sand -silt mixtures non- plastic fines. Clayey gravels, gravel-sand-clay mixtu; es. plastic fines. SANDS More than 50% Of coarse fraction is smaller than No. 4 sieve. Clean Sands (less than 5% fines). SW Weil- graded sands, gravelly sands, little or no fines. SP Poorly- graded sanas or rr aveliy sands, little or no fines. Sands with fines. SM Silty sands, sand -silt mixtures, • non - plastic fines. SC FINE GRAINED SOILS ci N e�• N SILTS AND CLAYS Liquid limit is less than 50 %. ML CL Clayey sands, sand -clay mixtures, /t plastic fines. Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or ciayey silts with sliont plasticity. Inorganic clays of low to,medium plasticity, oravelly clays, sandy clays, silty clays, lean lays. SILTS AND CLAYS Liquid limit is greater than 50 %. HIGHLY ORGANIC SOILS • Organic silts and organic clays of low plasticity. Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic. . Inorganic clays of high plasticity; fat clays. ' �i�i�ii {i Organic clays of medium to high piasticry, ! ; organic silts. • " Peat and other highly organic soils. DEFINITION OF TERMS AND SYMBOLS I 11 P 7 1 2" OUTER DIAMETER SPLIT SPOON SAMPLER 2.4" INNER DIAMETER RING SAMPLER OR SHELBY TUBE SAMPLER SAMPLER PUSHED SAMPLE NOT RECOVERED WATER LEVEL (DATE) WATER OBSERVATION WELL C TORVANE READING,-tsf 0',U PENETROMETER READING, tsf W MOISTURE, percent of dry weight pCf DRY DENSITY, pounds per cubic foot LL LIQUID LIMIT,percent PI' PLASTIC INDEX N STANDARD PENETRATION, blows per foot. ..r..,11 TERRA 4W2 ASSOCIATES C., Giv:_11r ti Cot isultants 10 Acre Residential Plat Tukwila Washington IProj. t lc . 1515 1Dair: 8/90 1Fiwurc. 3 Logged By MM Date 7 -25 -90 Depth (ft.) USCS TEST PIT NO. TP -1 Soil Description Elev +158± __ 1 12 to 14 inches Topsoil and Duff, damp, very loose. 36.2 SM R Reddish -tan, silty fine SAND with many roots, damp, S'1/ r ran, fine sandy SILT, damp, medium dense. ML T Tan -gray, fine sandy SILT to SILT with sae stains, 3 10 TEST PIT NO. TP -2 Logged By 111 Date 7-25 -90 1 1 Elev. +174± Drown, sitly Topsoil and Duff, damp, very loose. — S"4 '�, silty SAND with sane roots, damp, loose becomes medium dense. ,—. Sri/ Tan-gray, silty fine SAND to fine sandy SILT at lower — ML depths, cemented, damp, dense to very dense (Till- like). 19.2 1— (becomes less cemented at bottom) -- Test Pit terminated at 11.1 feet. — No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants • TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 I Figure 4 TERRA ASSOCIATES Geotechnical Consultants • TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 I Figure 4 Logged By ?T4 Date 7-25-90 Depth USCS TEST PIT NO. TP-3 Soil Description Elev. +164± - (%) 1C 1 TEST PIT NO. TP-4 Logged By 1,11 Date 7-25-90 Elev +171± Dark brown Topsoil and Duff, damp, very loose. 22.3 .... ___ r-----. S'1 Brown becanes red-tan, silty fine SAND with some roots, damp, loose becares medium dense. i--- SM SMI/ ML Tan, silty fine SAND, slightly cemented, damp to moist, dense. Grades into: Tan, fine sandy SILT, moist, dense. __ -- -- )--- __ -- .-- i--- ..._ ; - Test Pit terminated at 10.4 feet. No groundwater seepage encountered. Test Pit terminated at 8.9 feet. No groundwater seepage encountered. • • 1C 1 TEST PIT NO. TP-4 Logged By 1,11 Date 7-25-90 Elev +171± 1C 1 TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 Figure 5 12 inches silty Topsoil and Euff, damp, very loose. 23.4 -- --,----...- ;--- SK Tan-brown, silty fine SAND, damp to dry, loose. SM Red-tan, silty fine SAND, damp, medium dense. Grades into: SW ML Tan-gray, silty fine SAND to fine sandy SILT, damp, becomes moist, slightly cemented, dense (Till-like). -- .-- i--- ..._ ; - Test Pit terminated at 8.9 feet. No groundwater seepage encountered. • 1C 1 TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 Figure 5 Logged By - Date 7-2 .Depth (ft.) 0 10 15 TEST PIT NO. TP -5 • •S SCS s�u ML Soil Description rown ..opsoli an ty lops° , Elev +180± • w ( %) very 1 Red-tan, silty fine SAND, damp, loose to medium dense. Grades into: Tan-gray, silty fine SAND to fine sandy SILT with few gravels, damp to moist, medium dense. Sri ML ML Gray, fine sandy SILT with few scattered gravels and same cobbles, damp to moist, dense to very dense (Till- like). (becomes more silty with trace of clay) Test Pit terminated at 11.4 feet. No groundwater seepage encountered. TEST PIT NO. TP -6 Logged By Mgt Date 7-2 0 10 at SPI 20.7 Elev. +204± 12 inches dark brain Topsoil and Duff, damp, very loose. St V S14 SMV NIL 15 Tan, silty fine SAND With some roots, damp, loose. Tan with red stains, silty SAND with gravel, damp, slightly cemented, medium dense (Weathered Till) . Tan -gray, silty, gravelly SAND with same cobbles, highly cemented, damp, very dense (Till). Tan, fine sandy SILT with few gravel on top, and a pocket of blue -gray SILT, damp to moist., dense to very dense Call-like). 8.4 Test Pit terminated at 10.8 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 Figure 6 Logged By NM Date 7-26-90 Depth (ft.) 1 USCS TEST PIT NO. TP -7 Soil Description Efev +182+ •W (%) 1 12 to 14 inches dark brown Topsoil and Duff, moist, v. ]nose. 18.4 __ g -` r csm T Tan-red, silty fine SAND with sane roots and few g 1 T Tan, gravelly, silty SAND with stains and few cobbles, at T Tan -gray, gravelly, silty fine SAND to fine sandy SILT Test Pit terminated at 8.6 feet. Logged By AT1 Date 7 -26-90 TEST PIT NO, TP -8 Elev +210± _ pr 2fYi.nc 1 dark brown PEAT, wet, very soft. —• SI Reddish -tan, silty fine SAND with many Iron -Cxide stains, — moist, loose. • ■— Si Tan-brawn to tan, mottled, gravelly, silty fine SAND to 15.3 — to fine sandy SILT, becomes tan-gray in color, moist, dense. - SP1JI�iL __ ML Blue e•gray, fine sandy SILT to SILT, moist, dense and 24.5 11— • — Test Pit terminated at 9.7 feet. — No groundwater seepage encountered. 'ema ASSOCIATES TERRA Geotechnical Consultants TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington 1 Figure 7 Proj. No. 1515 [ate 8/90 'ema ASSOCIATES TERRA Geotechnical Consultants TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington 1 Figure 7 Proj. No. 1515 [ate 8/90 Logged By NM Date 7 -26-90 Depth (ft.) 1 USCS TEST PIT. NO. TP -9 Soil Description Elev +210± W (%) _, P PT 1 16-inch peat like Topsoil, wet to moist, very soft. 22.5 S4 T Tan-brown, silty fine SAND with roots, moist, loose. SOIL T Tan -red, silty fine SAND to fine sandy SILT with stains, Blue -gray, silty fine SAND to fine sandy SILT with TEST PIT NO. TP -10 Logged By MI Date 7-26-90 1 1 Elev +201± 12 inches dark brown silty Topsoil, damp, loose. _ Sti1 ''fan- brown, silty fine SAND with some roots, damp, .1 loose. _, SM/ Tan, silty fine SAND becomes fine sandy SILT, damp, 5— ML medium dense becomes dense (Weathered Till to 1111-like). 18.0 —`` ML — 1L/CL Blue -gray SILT to clayey SILT, damp to moist, hard. — 25.0 i— Test Pit terminated at 8.4 feet. No groundwater seepage encountered. TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 Figure 8 TERRA ASSOCIATES Geotechnical Consultants TEST PIT LOGS 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 Date 8/90 Figure 8 Mr. Bill Fowler August 11, 1990 In some of our test pits excavated on the site, hard and laminated silts and clays were encountered at depths below the till -like silty soils. The following sections of this report describe our study and present our recommendations in greater detail. PROJECT DESCRIPTION The site is located between 42nd and 44th Avenues South with access from South 137th Street, 42nd and 44th Avenues South just to the south of Southgate Park. The approximate location is shown on the Vicinity Map, Figure 1. Based on a conceptual site plan provided to us by Barghausen Consulting Engineers, dated June 13, 1990, access for the residences will be provided by a main entry from 42nd Avenue South from the west side. Access will also be provided by two secondary access roads through the east side from the existing 43rd Avenue South. Presently, it is planned to sub - divide the site into 43 single family residential lots with associated roadways and several open space areas around several possible wetland areas on the property. No grading plans were available at the time our study was conducted. However, based on the sloping nature of the site and proposed preliminary lot and roadway configurations, we anticipate that significant cuts and fills will be necessary to construct the plat roadways and develop the single family residential lots. Cuts and fills of up to fifteen feet may be required for the residences and roadways to be constructed on the site. The exact configurations or structural loads for the residences were not known at the time of our study. However, based on our previous experience with similar projects, we expect that perimeter load- bearing walls will carry one to two kips per lineal foot and that isolated spread footings may carry loads on the order of 15 to 25 kips. If any changes are made in the proposed construction as described above, and as project plans are being finalized, Terra Associates should be notified so that we can prepare supplementary recommendations, if necessary. Project No. T -1515 Page No. 2 Mr. Bill Fowler August 11, 1990 FIELD EXPLORATION AND LABORATORY TESTING Our field explorations were performed on July 25 and 26, 1990. Subsurface conditions on the site were explored by excavating test pits using a track -hoe operated by Perkins Excavating of Woodinville, Washington. A total of 10 test pits were excavated at the approximate locations shown on Figure 2. This plan is based on a Boundary Topographic Survey Plan prepared by Hebrank and Associates dated April 6, 1990. The locations of these test pits were determined by belt chain measurements and pacing from known points and site features shown on the property survey and should be considered approximate only. Elevations of the test pits were determined by interpolation between contours shown on the plan, and are also approximate. The field exploration was monitored continuously by a geotechnical engineer from our firm who classified the soils encountered, maintained a log of each test pit, obtained representative soil samples and observed pertinent site features. All samples were visually classified in accordance with the Unified Soil Classification System described on Figure 3. The logs of the test pits are attached to this report _as Figures 4 through 8. The soil classifications shown on these logs represent our interpretations of the field logs and reflect the results of visual examinations as well as laboratory tests performed on samples obtained from the test pits. Representative soil samples collected from the test pits were placed in closed containers and returned to our laboratory for further examination and testing. Moisture content determinations were performed on all samples. The results of our laboratory testing are shown on the attached test pit logs. SITE CONDITIONS Surface The nearly 10 acre property is located west of the intersections of 44th Avenue South and South 137th Street just east of 42nd Avenue South in Tukwila, Washington. The approximate location of the site is shown on Figure 1. The property is irregularly shaped and comprise an area of approximately 10 acres; two acres of which will remain as open space. At present, the site is generally undeveloped. The site is moderately to heavily wooded and forested, predominantly with second growth deciduous trees mixed with coniferous trees, generally consisting of alders, cottonwoods, and cedars, and scattered miscellaneous trees. There is also an open area in the central portion of the site which is presently covered by dense blackberries and nettles. The center of the property is bisected by a small, seasonal stream corridor which enters the property's southern boundary at approximately mid - point. This stream runs in a northeasterly direction and exits at near the center of the eastern property line. There is also a small stream near the southeast property corner. Project No. T -1515 Page No. 3 Mr. Bill Fowler August 11, 1990 Wetlands exist in each drainage corridor. The larger stream in the central portion of the site is flanked by moderately steep ravine slopes. A nursery is Iocated directly south of the property and several residences and Southgate Park are situated north of the site. The site generally slopes down in a northeasterly direction with the exception of a ravine in the south - central portion of the site. The site slopes range between inclinations of approximately 25 to 30 percent. Elevations on the property range from about Elev. +232 near the southwest property corner to a low depression at about Elev. + 110 near the northeast property corner. We noted evidence of standing water within the lower portions of the ravine and the area near the east- central portion of the site. The above features are shown on the attached Figure 2. This figure is based on a Boundary and Topographic Survey Plan prepared by Hebrank and Associates dated April 6, 1990. Subsurface As indicated by the test pits and visual observations, dense and hard silty till -like soils are present at relatively shallow depths ranging between three and five feet. Above the till - like soils, there is a two to three foot thick layer of loose to medium dense overburden silty sand and a topsoil and duff layer. In Test Pits TP -8 and TP -9, which were excavated near the wet area of the site, encountered approximately two feet or so of peat -like soils. The total thickness of topsoil and loose silty sand overburden soils ranged between approximately three and five feet. Hard, laminated silty clays and clayey silts were encountered below the till -like soils in Test Pits TP -1, TP -8, and TP -10. The cemented till and till -like which were encountered in most of our test pits consisted of unsorted mixture of silt, sand and gravel. The till is a relatively impermeable glacial soil deposited about 12,000 to 15,000 years ago, during the last glacial advance through the Puget Sound basin. Approximately 3,000 to 5,000 -feet of glacial ice deposited the till and overlaid a succession of glacial sediments consolidating them to their present day dense consistencies. The approximate locations of the test pits are shown on Figure 2. More detailed information on subsurface conditions is presented on Figures 4 through 8. Groundwater No groundwater seepage was noted in any of our test pits. However, under wet weather conditions and during the rainy season, perched groundwater tables are likely to develop above the dense till -like and relatively impermeable silts and clays observed on the site. Slope Stability In their present configuration and with the native vegetative cover, the natural slope areas on the property are generally moderate and are stable. We did not observe any signs of slope instability on the site. The slopes are quite steep in the northwest portion of the site and an area along the east- central part of the site along the designated wet area. However, no construction and development is planned for these portions of the site and they will remain as open spaces. Project No. T -1515 Page No. 4 Mr. Bill Fowler August 11, 1990 There is no evidence of movement on the site slopes. However, minor surface erosion and sloughing may occur on the steeper slopes over time. Surface soils across the property will be subject to erosion where the ground surface is unprotected by vegetation or other physical erosion control devices. DISCUSSION AND RECOMMENDATIONS General Based on our study, it is our opinion that the proposed residential plat may be developed as planned, provided the recommendations presented in this report are incorporated into the project design and construction. The primary geotechnical feature which will influence the development and construction of the site is the significant grading that will be required on the site to construct roadways and building pads. The roadways will require significant cuts and fills to achieve the desired final grades. Where cuts are needed to construct the roads, they must be made at stable inclinations. Native vegetation on the slopes should be protected from disturbance during construction. Permanent cut slopes in the native undisturbed soils.should be made at an inclination no steeper than 2:1 (horizontal:vertical). Fill slopes should also be made no steeper than 2:1. Surface water should be carefully, controlled along the roadways and diverted away from the slopes. This report has been prepared in accordance with generally accepted geotechnical engineering practices and is the property of Terra Associates, Inc. No other warranty, expressed or implied, is made. It is intended for specific application to this project and for the exclusive use of the Dujardin Development Company and their representatives. The following sections of this report present more detailed recommendations for the various geotechnical engineering aspects of this project. These recommendations should be incorporated into the project design and construction. Foundations The proposed residences may be supported on continuous and /or isolated spread footings bearing on the competent native soils present below the topsoil layers or on compacted structural fill. The near surface soils below the topsoil in some areas are loose. Hence, depending on the depth of excavation required to reach design footing grade, the native soils may need to be recompacted in place or minor over - excavations may be needed for some foundations. Project No. T -1515 Page No. 5 Mr. Bill Fowler August 11, 1990 Footings shoul outside finish g allowable bean inches should b a minimum size used when cons reinforcement extend to a minimum depth of 18 inches below the lowest adjacent ade. Continuous and individual spread footings may be designed for an g pressure of 2,000 pounds per square foot. A minimum width of 12 used for continuous footings and individual spread footings should have of 18 inches. A one -third increase in the above bearing pressures may be dering wind or seismic loads. All footings should be provided with steel accordance with structural requirements. Retaining and •wer Level Basement Walls Lower level b the pressure restrained from pressure of 100 Lateral pressur equivalent flui poured neat a friction factor An appropriat safety factor of Settlements We anticipate t soils or on ad anticipated Ion majority of the ement walls should be designed as structural retaining walls supporting osed by an equivalent fluid weighing 35 pounds per cubic foot. Walls free movement at the top should be designed for an additional uniform ounds per square foot. s may be resisted by passive pressures acting against foundations. An • weight of 350 pounds per cubic foot may be used when footings are ainst undisturbed native soils or against structural fill. In addition, a f 0.4 between concrete and soil may be used. These are ultimate values. safety factor should be used in the computations. We recommend a t least 1.5. at the total settlements for structures supported .on the competent native quately compacted structural fill will be less than one -half inch. The -term differential settlement should be less than one - quarter inch. The ettlements should occur during construction. Slabs -On -Grad Concrete floor .labs, where used, may be constructed as slabs on grade supported either on the compet =nt native soils or on structural fill. We recommend that four inches of a free - draining : avel such as 1/4 to 3/8 inch pea - gravel be placed below the slab to act as a capillary bre k. In addition, a plastic membrane with a thickness of ten to twelve mils may be place above the gravel to act as a vapor barrier for additional moisture protection. Lot Drainage Surface gradie is on the individual lots should be created to direct runoff away from the residences and . way from slopes toward suitable discharge facilities. Perimeter fout.idation drains should be installed and tightlined away from the buildings. Drains should be at the levels of footing bottoms or below the crawlspace level, whichever is lower. Roof gutter drains should be separately tightlined away from the structures. All drains should be discharged into the storm drain system. Project No. T -1515 Page No. 6 Mr. Bill Fowler August 11, 1990 Roadway Construction Roadways for the proposed development may be constructed on the recompacted native soils below the surficial vegetation and topsoil or on compacted structural fill placed after stripping the areas of vegetation, topsoil and any debris, depending on the depth of cuts or fills required to reach design grades: Where structural fill is placed, the upper twelve inches of the subgrade should be compacted to 95% of the maximum dry density as determined by ASTM D -698 (Standard Proctor). Recommendations for cut and fill slopes are included later in this report. All subgrade areas should be in a stable, non - yielding condition prior to paving. The use of a coarse layer of Asphalt Treated Base (ATB) to protect the subgrade during construction should be considered if the work will be performed during wet weather. As a minimum, we recommend that pavements on the site consist of 2 inches of asphalt over 6 inches of crushed rock base. Approximately fifteen feet of so of fill may be necessary to construct the road crossing over the swale and stream in the south - central portion of the site. A "key" should be excavated at the toe of the sides of the roadway fills and should extend at least two feet into competent native soils. The key should also extend laterally at least two feet outside the limits of fill placement. This keyway excavation should be proofrolled. However, if water is noted, proofrolling should be avoided. If groundwater or water from the existing stream at the bottom of the ravine is noted during excavation of the key, a free draining blanket of clean crushed rock should be provided at the bottom of this excavation in order to allow a firm working surface and allow future drainage. The final slope face on the road sides should be densified by compaction with a dozer or roller and should not be any steeper than the recommended 2:1 (H:V). We recommend planting or hydroseeding of the face of both cut and fill slopes in order to reduce the erosion potential of the slope areas. Cut and fill slopes elsewhere at the site should also be constructed with a finish inclination of 2:1 or flatter. Fills should be placed in thin layers and compacted to at least 95% relative compaction as determined by ASTM Test Designation D -698 (Standard Proctor). Each layer should be "benched" into the native soil slope where slopes exceed 25 percent. Surface water should not be allowed to flow over the face of any slope. As soon as possible after construction, permanent exposed slopes should be planted with an appropriate plant mix or provided with physical protection from erosion. Site Preparation and Grading The building and pavement areas should be stripped and cleared of vegetation, topsoil and debris. The stripped topsoils may be used as berms, landscaping or in non - structural areas, if desired. Adequate erosion control measures will be needed during earthwork construction on the site. Project No. T -1515 Page No. 7 Mr. Bill Fowler August 11, 1990 Following stripping, any loose areas noted should be over excavated and replaced with structural fill or clean crushed rock to a depth that will provide a stable base. Structural fill should be placed in thin layers and compacted to at least 95 percent of the maximum dry density in accordance with ASTM Test Designation D -698 (Standard Proctor). The majority of the site native soils are high in fines content making them difficult to compact during rainy weather or when placed over existing wet conditions. Any import soils to be utilized should first be examined by the soils engineer for use as a structural fill. We suggest that clean import fills contain no more than 2 percent "fines" passing through No. 200 sieve on the portion passing the 3/4 inch screen. Structural fill should be placed in horizontal layers not exceeding twelve inches in uncompacted thickness. Fills placed on the swale with slopes greater than 25 percent should be keyed and benched into the slopes All permanent cut and fill slopes should be made at an inclination no steeper than 2:1. Permanent slopes should be vegetated to reduce future erosion. Temporary slopes may be made at an inclination of 1:1. Utilities Where utility lines are to be excavated and installed in the roadways, we recommend that all bedding and backfill be placed in accordance with APWA specifications. Fill placement and compaction should be in accordance with the recommendations given earlier in this report. It is likely that trenches made over four feet in depth during winter will encounter perched groundwater conditions. The site soils contain significant amounts of fines and are considered to be moisture sensitive. It is recommended that clean granular fill material be imported for use as backfill in the utility trenches, particularly if work is performed in wet weather. Additional Services It is recommended that we be provided the opportunity for a general review of the final design and specifications in order that earthwork and foundation recommendations may be properly interpreted and implemented in the design and construction. The analyses and recommendations submitted in this report are based upon the data obtained from the test pits excavated on the site. The nature and extent of variations in the test pits may not become evident until construction. If variations then appear evident, we should be requested to re- evaluate the recommendations presented in this report prior to proceeding with the construction. It is also recommended that we be retained to provide geotechnical services during construction. This is to observe compliance with the design concepts, specifications, and recommendations; and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. Project No. T -1515 Page No. 8 -r •s 'r '1 ., Mr. Bill Fowler August 11, 1990 We recommend that Terra Associates, Inc. provide the following services during construction: 1. Examine all stripped subgrade areas and the proofrolling operations prior to the start of fill placement or earthwork. 2. Examine all cut slopes and excavations to verify conditions are as anticipated. 3. Examine all foundation and slab areas prior to forming and concrete placement to evaluate that adequate foundation support is available. 4. Perform field density testing of structural fills as needed during placement and observe the grading and earthwork operation. We request that a minimum of two working days' notice be given to schedule our services during construction. The following figures are included and complete this report: Figure 1 Figure 2 Figure 3 Figures 4 through 8 Vicinity Map Exploration Location Plan Soil Classification Chart Test Pit Logs We trust the information presented herein is adequate for your requirements. If you need additional information or clarification, please call. Sincerely yours, TERRA ASSOCIATES, INC. Mehrdad Moini Geotechnical Engineer 7`\ Anil : utail, P.E. President MM /AB:tc cc: Barghausen Consulting Engineers, Inc. Project No. T -1515 Page No. 9 Lartik S7 S a 1••T II I • 5 /f•••• I0IS. r. 5 103.5ST 1 /Oil SW 1141• ST 1n*j 1.4 m It1Jl 7 t4 RAY•t• bw f 4 '11 TI • COUNTRY. C" 5 ST ®® Cl y = MEL1 67H. • .t '.1 S 1171w�, S 1201w SI 1 \_ p/Ih1 •M b iGr/IJ `` •1• +� W0 ItifC 1351" ST /1 i ©c221ii>ea PROJECT SITE 1 •1Vt•IOM.,. ST ®® + . I U Mgr rrN�o; . . 11711 +tl w cc[• : z ST z �: •. `tc S wN 1 15 s 133mo 5T 5 1351. ST 1MT" THIS FIGURE IS COPIED FROM PAGE 33 OF THE THOMAS BROS. MAP OF KING COUNTY. TERRA ASSOCIATES Geotechnical Consultants VICINITY MAP 10 Acre Residential Plat Tukwila Washington Proj. No. 1515 I Date 8/90 1 Figure 1 PRESERVATIVE PAINTS Dina Lange 355 -7879 RECEIVED AUG 1 31992 COMMUNITY DEVELOPMENT We have developed a number system on the various color schemes. To help ease any confusion, we have labeled each set of colors with a designation number. For example: Body will be B-1 = J17Z Trim will be T-1 = OW -9 Door will be D-1 = S -35 -3 Enclosed is a cross reference sheet indicating which order numbers equal which color numbers. Color Scheme #1 Body - B-1 = J -17 -2 Trim - T-1 = OW -9 Door - D-1 = S35 -3 Color Scheme #2 B -2 = B -37 -1 T -2 = B -38 -2 D -2 = B -34-3 Color Scheme #3 B -3 = T -37 -2 T -3 = T -36 -1 D -3 = T -35 -3 Color Scheme #4 B -4 = E -37 -2 T -4 = OW -1 D -4 =AA6 Color Scheme #5 B -5 = N -36-1 T -5 = N -38 -2 D -5 = AA50 Color Scheme #6 B -6 = J -16 -1 T -6 = J -18 -2 D -6 = J -16 -1 Color Scheme #7 B -7 = N -37 -1 T -7 = X -38 -2 D -7 = X -14 -3 Color Scheme #8 B -8 = B -17 -2 T -8 = N -39 -3 D -8 = B -17 -.2 Color Scheme #9 B -9 = B -16 -1 T -9 = X -37 -2 D -9 = W -35 -3 Color Scheme #10 B -10 = E -36 -1 T -10 = E -38 -2 D -10 = AA41 » ,...„,.......,,_ CHARLES MORGAN 8: ASSOCIATES 7301 BEVERLY LANE EVERETT, WA. 98203 Phone (206) 353.2888 August 10, 1992 Department of Community Development City of Tukwila 6300 Southcenter Boulevard Tukwila, WA 98188 Re: Fosterview Estates, EPIC -51 -91 Gentlemen: We are submitting an application for a PRD for the Fosterview Estates development proposal. We are also submitting a BLA at this time. The enclosed drawings and information are not the final engineered drawings. These drawings are a concept of what is believed to be what the Public Works and Planning Department are looking for in an overall design. The developer does not want to proceed further with drawings, until these conceptual drawings are reviewed and the road pattern and disposition of the sewer and storm drainage are felt to be what will be approved for final drawings. The final drawings are at considerable expense and we do not wish to prepare these drawings until a conceptual plan is approved. The fact that this is a submittal for conceptual approval only, we are not submitting the sub - division plot. We are showing conceptual lot lines, with home sites located on the lots. We have 5 zero lot -line lots, they are sites 6 through 10. The final landscaping plan giving full details of each lot will be submitted when final drawings of the engineers are presented and full final approval is being requested. RECE1VEC AUG 1 31992 COMMUNITY DEVELOPMENT LICENSED: WASHINGTON • OREGON • CALIFORNIA • IDAHO • UTAH • ARIZONA • MONTANA WYOMING • COLORADO • NEW MEXICO • NEBRASKA • NEVADA Department of Community Development City of Tukwila Re: Fosterview Estates, EPIC -51 -91 August 10, 1992 Page 2 Ten color and material sample boards are enclosed with this submittal. These will be the sample boards that will be offered to the prospective home owners. Also enclosed are copies of typical home plans that would be offered to the prospective home owners. Sincerely, Charles E. CEM /bjm NORTH !%0 1'3© P'J J . PTP /PIKE :rBAI A'.CCEh•9• RO PrDJ Ct 3531. 4P9.AVENUE. 1 4 HOt19E I NEW (Z' IIEWOIKE f AJL 4 Acet h RD HDl19 # 13901. A-00 EGTION A -A EX.. TRADE eravinvinivf 140 9CALE -H:1 11- 0';.v :I'-0 I ba Ex. TREES: To �MAIN: :: • Pf�JECt:::: :::.6 31: 430•AvENUE h• NEW: P.EP %P(KE SAIL:::.: :: .:. . NEW )11 PED /pia '(RAID 4 •ACCEff R.9 NORTH MiJ r:P/PII4 MAI Accw RP P Jecr 4 HaUPe I f(romi. Apwr "A- 135.31. 4P9.AVENLJe. NW (11 n9/6.1Ke UAL. ACethh e 160 H.011 4 13hN KeM'Affkl. NEW: P.EW:ENKE iKAIL ACChh • KR ECTION A-A ex._ arc412e fraVEYCI•IPZIa hCAL.E.-H:1" ;i1:1"-A91 PROJECT .13h31 430.AVE4EUE, A Nt4 PEP/f5 KE MAIL 4 .Acce0 R9 FIN1hHEV liKAn NOTE : ROG EC EKI eh. W ILL. MAX.. 411-116.H: KOC10EKIEhOVEK ZW:HUH WILL. 1-1AVE Md• HANPRAIIr. 1649 l• RoCKeRY . U.slItA ECT ION EX..GRAVEI, RKII/E 100 heALE-R•1".-0;1/.1"-,01 S F SEP 7 199,r, COMMUNIT; DEVELOPMEls r. 1• .,//, tf 1,0 •■• \ 1.11 F I 1110 I ) 44th AVE. S. 1 I S i; CTI CHARLES MORGAN & ASSOCIATES ARCHITECTS ttttt It ■•••••11).0 letInioNe 1101 101•11.1, C 11 (,L\3I1d CHARLES MORGA ARCHITECTS ASSOCIATES 4 1H r-. MHVd 31VSHIf10S !.1 etc 23 8 CHARLES MORGAN & ASSOCIATES ARCHITECTS salsbmWON .10.N. PM III 1.44 11.01 ....... ONO :. I .. ti: "FOSTERVIEW ESTATES" -- , ` ; �-��. TUKWILA. WASH. — —_- __— _ __s' .�' SOUTNGATE PARK =:.:. i l ; �,, i s ` - • , wt'S • \+• ��_ IJey .. _ �� __ .(.'.,.'Lc 7 =J ..'.'1�.1b\ o - - ' -ir °_ •;, /:eta° 1` . . \p .`� ` T' 'fJ_ 1. f s �; jSi �-- %� ^'! -�"- -". J f - --� % l r /` /•r`- i�/ fi / ,.r,'. y� `\ �n _'."`ter= co..�c.,t �• ff J�- i `= '� ` — = ){ �f!' /< / /yam /y �/ / ,may // .. % �� _. __ 4 •)' j! _ /7- yl- j �^ .. `'._.�' �• 7 ,. ,jj_-s-,r'_- -- /.:4 •i :'. / ! /'. •- t�"y'.' _:1.t f..'•' °! _ ' }�^ _.• r - \\~ --F,� -FBI FJ'�/ - !'l '/j f •:T' /r, '_'._./ ••� , ..ff•,'`/ �/ ,/.. /�r\ ti% %/ ` � / i/ _.. :a - -�'-�;` l li i r s mfr /R. // �/ J.. :�1 �_ '/� J'%'� .. r: - L_ .c.4= / ^ `,' :_ 1r -r %. r.'' ' _ // jT/ / /.' ''rs- �/ r r `!' • • - `Sf� o �ti -- -:.� - '�i/ _ \_ -� ,rte`. ,• : - �- �/ / 7 % %` ==-'S` "/ j %N+- _ '� ..i }af 1-" •� •_.`jam' <yJ >..N j / /.'/ , : 1 N D U J A R D I N DEVELOPMENT C O M P A N Y BOUNDARY AND TOPOGRAPHIC SURVEY :- 1 0 .4 C R f S I T E •�- DOM 11111r '): 0.mn4 S.01••• Mz.nn419n 94104 (106) 447 • 1114 33 FOSTERVIEW ESTATES HOUSE "A" -ENTRY ELEVAT ION LEFT SIDE ELEVATION REAR ELEVATION RIGHT SIDE ELEVATION TYPICAL ELEVATION - OTHER ROOF ELEVATIONS AVAIABLE BRICK WAINSCOTE AVAILABLE MAX HEIGHT 35' 1924 sq.ft. (APP OX.) lid ILO. PUN L92 -cobs IN PIM PLAN WAN 1111111111 RAN FOSTERVIEW ESTATES HOUSE "B" ENTRY ELEVATION =VAT MI 1101111011 01 RIGHT SIDE ELEVATION REAR ELEVATION LEFT SIDE ELEVATION TYPICAL ELEVATION - OTHER ROOF ELEVATIONS AVAILABLE BRICK WAINSCOTE AVAILABLE MAX HEIGHT 27' 1495 sq.ft. (APPROX.) .1■1111101_.e. BASEMENT Lgt2.-ooss 24' ‘: 9 F OSTERVIEW ESTATES HOUSE "C" RIGHT SIDE ELEVATION 24' LEFT SIDE ELEVATION TYPICAL ELEVATION - OTHER ROOF ELEVATIONS AVAIL/WI.. BRICK WAINSCOTE AVAIL BLE MAX HEIGHT 271 1838 sq.ft. (APPROX.) 1-612--coros FOSTERVIEW ESTATES HOUSE "D" ENTRY ELEVATION LEFT SIDE ELEVATION REAR ELEVATION RIGHT SIDE ELEVATION 26' TYPICAL ELEVATION - OTHER ROOF ELEVATIONS AVAILABLE BRICK WAINSCOTE AVAILABLE MAX HEIGHT 29' 1390 sq.ft. (APPROX.) Mtoswr RPM MI PIM OM m11. NM IMO 0101. Lq.-cRxos I J lit /LOON MAN 28' FOSTERVIEW ESTATES HOUSE "E" LEFT SIDE ELEVATION RIGHT SIDE ELEVATION ENTRY ELEVAT I ON varies f1 TYPICAL ELEVATION - OTHER ROOF ELEVATIONS AVAILABLE BRICK WAINSCOTE AVAILABLE MAX HEIGHT 31' 1639 sq.ft. (APPROX.) BASEMENT FLOOR PLAN L(12.-0065 let FLOOR PLAN t!.„FO$TERVIEW ESTATES .HOUSE "P , t 24' ENTRY ELEVATION REAR ELEVATION ttJEVATIONI fI RIGHT S I DE ELEVATION LE IDE EL TA 1 TYPICAL ELEVATION - OTHER ROOF ELEVATIONS AVAILABLE BRICK WAINSCOTE AVAILABLE MAX HEIGHT 27' 1449 sq.ft.(APPROX.) 2nd FLOOR LAT-oof45 11Pxlm luDhll 1,1, *1 II41 I fib L_ t FLOOR 24' • • . FOSTERVIEW ESTATES HOUSE "G" ENTRY ELEVATION via ION 01 LEFT SIDE ELEVATION REAR ELEVAT I ON RIGHT SIDE ELEVATION TYPICAL ELEVATION - OTHER ROOF ELEVATIONS AVAILABLE BRICK WAINSCOTE AVAILABLE MAX 'HEIGHT 27' 1365 sq.ft. (APPROX.) 2nd FLOOR Pli.AN Viz-oo65 I et FLOOR PLAN FOSTERVIEW ESTATES HOUSE "H" '4 ENTRY ELEVATION LEFT SIDE ELEVATION 32' REAR ELEVATION RIGHT SIDE ELEVATION TYPICAL ELEVATIONS - OTHER ROOF ELEVATIONS AVAILABLE BRICK WAINSCOTE AVAILABLE MAX HEIGHT 35' 1970 sq.ft. (APPROX.) NM RAM RM w•• r L OEM (. PLANNED RESIDE!: ilAL DEVELOPMENT APPLICATION CHECKLIST CITY OF TUKWILA DEPARTMENT OF COMMUNITY DEVELOPMENT 6300 Southcenter Boulevard, Tukwila, WA 98188 Telephone: (206) 431 -3680 The following materials must be submitted with your application. This checklist is to assist you in submitting a complete application. Please do not turn in your application until all items which apply to your proposal are attached to your application. If you have any questions, contact the Department of Community Development at 431 -3680. GENERAL Application Form . PRD Fee — $800.00, plus $100.00 /acre Environmental Checklist Environmental Checklist Fee $225.00 . PLANS Seven (7) copies of the set of plans are required. The scale shall not exceed 1 " =30', with the north arrow, graphic, scale and date all identified on the plans. Also, the license stamps of the architect and landscape architect shall be on each appropriate plan. RECEIVED AUG 1 4 1992 COMMUNITY DEVELOPMENT The following information should be contained within the plan: A. Vicinity map showing location of site and surrounding prominent landmarks. Property dimensions and names of adjacent roads:- 0166 a `" t z r tateduL. ozljor m7i -6o atiftlpfl- Lot size and im • ervious (paved and building areas) surface calculations. -- 4,40 - auk.__ I• (., IF c Oz D. Existing and finished gra• es at 2' contours with the precise slope of any area in excess of 15 %. E. Location and dimensions of existing and proposed structure(s), accessory structures with appropriate setbacks, parking and loading area dimensions, and driveways. o 5 '0-0) cicUA C 26W gRiA igi ,/* "630 4 /ma, Existing (6" in diameter) trees by species and an indication of which will be saved. Proposed landscaping: size, species, location and spacing. M0�- l Na CYvi fit icAroo -sating 1 Mviti" 43 ittaao PR- RD APPLICATION CH LKLIST `- Page 2 -ocatio and di- ension g and propo structures, parking areas, driveways, Show parking stall totals. G. E • • ng trees (6" ill be ed. ►ropose distance apart. cture(s) sor s, and tras - closure areas. \ujA —d-kwatv pan ameter) by and an i dica on of w 'ch nds • - ping: si spe ' es, locati s - • d Location, dimensions and nature of any proposed easements or dedications for utilities and access. Lzst.a c ° len (3 �`? , I. Building elevations sufficient to convey exteriochitectural intent, maxi- mum heights, type and density of dwelling units. For multiple residential, location, dimensions and description of recreation areas. '---� K. Sign and street light elevations and locations. L. Color and material sample board of exterior paint and materials. One (1) Photomaterial Transfer (PMT) of each plan reduced to 8.5" by 11" (most printing companies can make PMT's). PUBLIC NOTICE A mailing label matrix of property owners and residents 300 feet of your property. (See attached "Address Label Requirements") ) A King County Assessor's Map which identifies the location of each property ownership and residence listed. The maps may be ordered from the King County Public Works Map Counter at 296 -6548. 0 4 IONAL d spective drawings, photographs, color renderings or other graphics which may needed to adequately evaluate your application. Oth- required information: .).1-5•691 ale (((lJl 6 cApo �.. • Ibtb ® m8bb a.,c.63 511. 17° n> 4 QA'U c&n Nw W ce, 5-ivt7Diok 674'?` -Tiara?) r gown ccnZo-e FhAAAI/RAA pai-rdett .007f,"jaL Qt.c.C�. IaLtecoo pc y)02 cam, OCIt'16 4 co. 1 ` 7` C t4tklo c,cJ eYJ — pootett PLANNED RESIDL.4TIAL DEVELOPMENT APPLICATION CITY OF TUKWILA DEPARTMENT OF COMMUNITY DEVELOPMENT 6300 Southcenter Boulevard, Tukwila, WA 98188 Telephone: (206) 431 -3680 1. 2. 3. 4. 5. NAME OF THE PROPOSED DEVELOPMENT: Fosterview Estates NUMBER OF DWELLING UNITS: 41 single family lots ZONING OF SUBJECT SITE: Single family PROJECT LOCATION: (Give street address or, if vacant, indicate lot(s), block, and sub- division; or tax lot number, access street, and nearest intersection) Approximately 10 acres between 42 Ave. S. & 44th Ave. S. and 137th St. Quarter: SE Section: 15 Township: 23N Range: 04 E (This information may be found on your tax statement) APPLICANT:* Name: Duiardin Development Company Address' P. 0. Box 5308, Everett, WA 98206 Phone: (206)334 -5018 Signature: (" /f Date: May 6, 1992 * The applicant is the person whom the staff will contact regarding the application, and to whom all notices and reports shall be sent, unless otherwise stipulated by applicant. 6. PROPERTY Name: OWNER AFFIDAVIT OF OWNERSHIP Dujardin Development Company Address: P. 0. Box 5308, Everett, WA 98206 Phone: (200 334 -5018 I/ WE,[signature(s)]i`,,,�— —' - �. j, C E l V E swear that I /we are the owner(s) or contract purchaser(s) of the property involved _ 1982 in this application and that the foregoing statements and answers contained iAis application are true and correct to the best of my /our knowledge and belief. COMMUNITY DEVELOPMENT Date: May 6, 1992 PRD APPLICATION Page 2 7. IF REQUESTED, PLEASE EXPLAIN HOW THE REQUESTED DENSITY BONUS FOR THE SUBJECT PROPOSAL MEETS THE FOLLOWING CRITERIA. A. At least fifteen percent of the natural vegetation is retained (in cases where significant stands exist). RESPONSE: All of the wetlands except that portion where the new street crosses the stream and the required buffers shall remain in its natural vagatarinn This consists of 26% of the site. B. Advantage is taken of unusual or significant site features such as views, streams, or other natural characteristics. RESPONSE: The wetlands and required bu" ;grs shall be left in their natural state. A nature trail could be put in along the stream. A large portion of the lots are so located that they will have a good view to the east. The development will allow easier access to Southgate Park for residences to the east of 44th Ave. C. Separation of auto and pedestrian movement, especially in or near areas of recreation. RESPONSE: Sidewalks will be provided to give access by pedestrians from the adjacent residential property to the east to Southgate Park. PRD APPLICATION ...- `" Page 3 D. Development aspects of the PRD complement the land use policies of the Comprehensive Plan. RESPONSE. The develonment_is produrttg housing simitar to that oxicting in the adjacent areas. It will give a traffic and pedestrian outlet or inlet to 42nd Ave. South from the area on 137th that lies east of 44th Street and it will assure that the existing wetlands will be retained and made available to the general public as determined adequate by the city. E. Some extraordinary public benefit is derived in exchange for the reduced minimum lot size in the planned residential development. RESPONSE: By the use of smaller lot sizes, it does make it possible to retain the existing wetlands and buffers, yet allows the developer to have enough lots to be able to make the project financially feasible and still keep the land sales price comparable with existing lots in the area. IN ADDITION, FOR MULTIPLE- FAMILY DENSITY BONUS REQUESTS: F. A variety of housing types are offered. RESPONSE: Not applicable PRD APPLICATION Page 4, 8. WILL THE PROJECT BE COMPLETED IN PHASES? 0 Yes 1 No If yes, please describe proposed phases and time frames. TR 9. PLEASE DESCRIBE THE OWNERSHIP PATTERN FOR THE PROJECT. 41 single family homes will be constructed and sold to individuals. 10. PLEASE DESCRIBE THE DETAILS OR LIST ANY RESTRICTIVE COVENANTS PRO- POSED FOR THE.PROJECT1. (This must be incorporated into your proposal and may only be recorded after review and approval by the City Attorney and City Council.) None anticipated 11. HOW WILL THE COMMON OPEN AREAS AND RECREATION AREAS BE MAIN- TAINED? Vre-t-terf--7-aas--tiD---bde Al 6 ODM 1(2figEA) ...g.1 Tg/. ip. pipriirpl RO, / 11 h 3x pa 11 gYa i,,alii . iR1 '1,4 Rr!w Ira 11!iii;lilill ii D gsi ql! 3 b. g ,.-.: li teitgll li ..!, / 1 — qV "IT I igti lr?Oei6rq li il 1 k Aw !!-V „//'/?,/1' 11 !:4 1 ri i bP1 103i iwg ---/- .' ---tir 'I no ti w 1 2 )1; a 1 -.:. i P4vg NI g! 11; i 11 - S a w 1 w Zi'l,r';I° . / - '"'•1-/ 41 \ 10 ,' ■!' lk ;.t.f. i, 1,. ':'kr 7,',;1;,,, ii,.1 '4,1111 :,,...z. .; ":..fiy.. :i..._:._.:1_,:::,...1i,::' '1 . r.,... 'i'4' ?At. ,,' , .e _____ • , • , •-.17 ..,,,,, 2 ,......:...--: .r.,..„,,---":-.;,,;•, ...--- ---,•'- --c- ,..---,- •v- :',-- - e,- ........ .--\-. X-1' 77'7,4'17,- .1-..-51-7...,,,,..- '' -.:"4/.%-.. 04' )*fVd 31VJN1f1OS !". ZN. CJ 0 r 33 a ____. 53 N m D c 11 m ni cn • •" _ _ L.,— .4 tt =>,•=1. t I rig •,..• a, ia. DUJ TDIN DEVELOPMENT COMPANY 7 0 A C S r C U .:-;r SRVEY ;- • 90020 �' mil};.-_ �� \\ � 1 � / / � .Mexw axe.. t. n.. wwnx. u�u�.�- r- n.v�..+.��n.•.:sti.�iti lrll !!.x'ft'KVCaC^J W5141! bMT.' nU+ 4e rtswc}Y.�AYSI.cYtmvbu�.e»�e:r.m �L+u�aw�rs�aM�an grt.a City of Tukwila. John W. Rants, Mayor Department of Community Development Rick Beeler, Director . April 22, 1992 Mr. Terre Harris 535 Broderick Building 615 Second Avenue Seattle, WA 98104 RE: Fosterview Estates, EPIC -51 -91 Dear Terre:. The purpose of this letter to request from you a follow -up on the status for submittal of the subdivision and PRD applications for the Fosterview Estates development proposal. y�. Submittal of the above two applications must occur by May 6, 1992 in order to keep the current project. file (EPICf- 51 -91) open and to tentatively schedule a public hearing by June. Feel free to contact me at 431 -3663 if you have further questions. Sincerely, Denni Shefrin Associate Planner cc: File EPIC -51 -91 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206)4313665