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Permit L06-036 - HUNDTOFTE AARON - SPECIAL PERMISSION BUFFER REDUCTION
HUNDTOFTE RESIDENCE 3725 & 3727 S 126 ST I,06 -036 Project File Number: Applicants: Type of Permit:: Project Description: Location: Associated Files: City of Tukwila Department of Community Development TO: Aaron Hundtofte and Brie Campbell, Applicants King County Assessor, Accounting Division Washington State Department of Ecology Agencies with Jurisdiction This letter serves as a notice of decision and is issued pursuant to TMC 18.104.170 on the following project and permit approval. I. PROJECT INFORMATION L06 -036 Aaron Hundtofte and Brie Campbell Special Permission, Director Reduction in Wetland Buffer Reduce 80 -foot wide buffer for a Type 2 wetland to 40 -feet in order to construct two single family homes and associated parking. An existing driveway that is within the reduced buffer area will remain. A wetland enhancement plan has been provided for the reduced buffer area, and has been reviewed and approved with conditions by the City's Urban Environmentalist. 3725 and 3727 S. 126 Street NOTICE OF DECISION L06 -035, Boundary Line Adjustment Comprehensive Plan Designation/Zoning Low Density Residential District: II. DECISION July 10, 2006 CL Page 1 of 4 07/07/2006 11:48:00 AM q: \Hundtofte 131,A \1,06-036 Notice of Decision.doc Steven M. Mullet, Mayor Steve Lancaster, Director CRITICAL AREA SENSITIVE AREA SEPA Determination: The City SEPA Responsible Official has previously determined that this application does not regiiire a SEPA threshold determination because it is categorically exempt. Decision on Substantive Permit: The Community Development Director has determined that the application for a reduction in the wetland buffer does comply with applicable City and state code requirements and has approved that application, subject to the conditions set forth below based on the findings and conclusions contained in the staff report. 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • Phone: 206 - 431 -3670 • Fax: 206 - 431 -3665 L06 -036, Hundtofte Sensitive Areas Departure Notice of Decisions Conditions of Approval: 0 o 1. In lieu of spraying herbicide to eliminate the Japanese Knotweed, the plant stems must be injected with herbicide, which is an effective control measure and minimizes potential contamination of the wetland and stream. As with any herbicide, only those approved for this use by the EPA and the State are permitted and only according to the instructions on the label. More information on control of Japanese Knotweed can be found in the document prepared by The Nature Conservancy located on the Internet at: http: / /tncweeds. ucdavis .edu /moredocs /polspp0 I .pdf. 2. The plant list provided in the Conservation District plan must be used in lieu of the plant list provided in the Sensitive Areas Report. Plant substitution is acceptable, provided that native plants are used and the plants are appropriate for the hydrologic regime. 3. A planting plan must be provided for the wetland and buffer area. It is acceptable to provide a simple planting plan that identifies approximate zones for planting the different combinations of plants and the number of plants in each zone. 4. A report summarizing the site inspection after the plantings must be provided. There are two options for providing the City this report: either the King Conservation District staff may inspect the site or a wetland biologist or landscape professional must inspect the plantings. The report must be provided within 15 days of the inspection. 5. Annual maintenance and monitoring reports must be provided to the City for five years as discussed in the Sensitive Areas Study. 6.The performance standards as stated in the Sensitive Areas Study and Mitigation Plan are acceptable for this site: 1) 75% survival of installed plants at the end of the 5 year and 2) 60% areal coverage of tree sapling/shrub stratum. 7.A performance bond in the amount of 150% of the cost of the plant materials must be provided at the time of final City inspection of the implemented planting plan. 8.Record the wetland and buffer delineation with King County Records and Elections and provide a copy to the City. III. YOUR APPEAL RIGHTS The Decision on this Permit Application is a Type 2 decision pursuant to Tukwila Municipal Code §18.104.010. Other land use applications related to this project may still be pending. One administrative appeal to the Planning Commission of the Decision on the Permit itself is permitted. CL Page 2 of 4 07/07/2006 1 I :48:00 AM q: \Hundtofte BLA \L06 -036 Notice of Decision.doc L06 -036, Hundtofte Sensitive Areas Departure Notice of Decisions A party who is not satisfied with the outcome of the administrative appeal process may file an appeal in King County Superior Court from the Planning Commission decision. In order to appeal the Community Development Director's decision on the Permit Application, a written notice of appeal must be filed with the Department of Community Development within 14 days of the issuance of this Decision, that is by July , 2006. The requirements for such appeals are set forth in Tukwila Municipal Code 18.116. All appeal materials shall be submitted to the Department of Community Development. Appeal materials MUST include: 1. The name of the appealing party. 5. A fee of $100.00. • IV. PROCEDURES AND TIME FOR APPEALING 2. The address and phone number of the appealing party; and if the appealing party is a corporation, association or other group, the address and phone number of a contact person authorized to receive notices on the appealing party's behalf 3. A statement identifying the decision being appealed and the alleged errors in the decision, including any specific challenge to an MDNS. 4. The Notice of Appeal shall identify (a) the specific errors of fact or errors in application of the law in the decision being appealed; (b) the harm suffered or anticipated by the appellant, and (c) the relief sought. The scope of an appeal shall be limited to matters or issues raised in the Notice of Appeal. V. APPEAL HEARINGS PROCESS Any administrative appeal regarding the Permit shall be conducted as an open record hearing before the Planning Commission based on the testimony and documentary evidence presented at the open record hearing. The Planning Commission decision on the appeal is the City's final decision. Any party wishing to challenge the Planning Commission decision on this application must file an appeal pursuant to the procedures and time limitations set forth in RCW 36.70C. If no appeal of the Planning Commission decision is properly filed in Superior Court within such time limit, the Decision on this permit will be final. VI. INSPECTION OF INFORMATION ON THE APPLICATION Project materials including the application, any staff reports, and other studies related to the permits are available for inspection at the Tukwila Department of Community Development, 6300 Southcenter Blvd., Suite 100, Tukwila, Washington 98188 from Monday through Friday between 8:30 a.m. and 5:00 p.m. The project planner is Carol Lumb, who may be contacted at 206 - 431 -3661 for further information. CL Page 3 of 4 07/07/2006 11:48:00 AM q: \Hundtofte BI..A \L06 -036 Notice of Decision.doc L06 -036, Hundtofte Sensitive Areas Departure Notice of Decisions I • Property owners affected by this decision may request a change in valuation for their property tax purposes. Contact the King County Assessor's Office for further information regarding property tax valuation changes. Steve Lancaster, Director Department of Community Development City of Tukwila l^t- 7- lo • o(, DATE CL Page 4 of 4 07/07/2006 11:48:00 AM q: \Hundtofte BLA \L06 -036 Notice of Decision.doc Dept. Of Community Development City of Tukwila AFFIDAVIT OF DISTRIBUTION I , 0 HEREBY DECLARE THAT: Notice of Public Hearing Determination of Non - Significance Project Name: /. AL.. Notice of Public Meeting Project Number: Mitigated Determination of Non - Significance Mailer's Signature: Board of Adjustment Agenda Pkt Person requesting mailing: Determination of Significance & Scoping Notice Board of Appeals Agenda Pkt Notice of Action Planning Commission Agenda Pkt Official Notice Short Subdivision Agenda Notice of Application Shoreline Mgmt Permit Notice of Application for Shoreline Mgmt Permit __ FAX To Seattle Times Classifieds Gail Muller Classifieds PO Box 70 - Seattle WA 98111 ther rJ f Q j Mail: Was mailed to each of the addresses listed on this year 20 O(r P:GINAWYNETTA/FORMS /AFFIDAVIT -MAIL 08/29/003:31 PM 1-% day of in the Project Name: /. AL.. el..._At � � [o . � i�' &tumor' --_ Project Number: IP -- ' a S Mailer's Signature: D g/Lfz_v_. Person requesting mailing: bylAnnir) Was mailed to each of the addresses listed on this year 20 O(r P:GINAWYNETTA/FORMS /AFFIDAVIT -MAIL 08/29/003:31 PM 1-% day of in the ( ) U.S. ARMY CORPS OF ENGINEERS ( ) FEDERAL HIGHWAY ADMINISTRATION ( ) DEPT OF FISH & WILDLIFE OFFICE OF ARCHAEOLOGY ) TRANSPORTATION DEPARTMENT DEPT NATURAL RESOURCES OFFICE OF THE GOVERNOR DEPT OF COMM. TRADE & ECONOMIC DEV. DEPT OF FISHERIES & WILDLIFE M KING COUNTY AGENCIES () BOUNDARY REVIEW BOARD () FIRE DISTRICT #11 ( ) FIRE DISTRICT #2 ( ) K.C. WASTEWATER TREATMENT DIVISION iik KC. DEPT OF PARKS & REC KC. ASSESSOR'S OFFICE ( ) TUKWILA SCHOOL DISTRICT ( ) TUKWILA LIBRARY () RENTON LIBRARY () KENT LIBRARY () CITY OF SEATTLE LIBRARY () ()WEST () SEATTLE CITY LIGHT () PUGET SOUND ENERGY () HIGHUNE WATER DISTRICT () SEATTLE WATER DEPARTMENT ( ) AT&T CABLE SERVICES () KENT PLANNING DEPT ( ) TUKWILA CITY DEPARTMENTS: () PUBLIC WORKS () FIRE () POLICE () FINANCE () PLANNING () BUILDING () PARKS & REC. () MAYOR () CITY CLERK ( ) PUGET SOUND REGIONAL COUNCIL ( ) SW K C CHAMBER OF COMMERCE ( ) MUCKLESHOOT INDIAN TRIBE () CULTURAL RESOURCES PROGRAM () FISHERIES PROGRAM ( ) WILDLIFE PROGRAM FEDERAL AGENCIES WASHINGTON STATE AGENCIES SCHOOLS/LIBRARIES UTILITIES CITY AGENCIES OTHER LOCAL AGENCIES MEDIA () U.S. ENVIRONIUENTAL PROTECTION AGENCY () U.S. DEPT OF H.U.D. () NATIONAL MARINE FISHERIES SERVICE () DEPT OF SOCIAL & HEALTH SERV. () DEPT OF ECOLOGY, SHORELAND DIV EPT OF ECOLOGY, SEPA DMSION' ( ) OFFICE OF ATTORNEY GENERAL • SEND CHKLIST W/ DETERMINATIONS • SEND SITE MAPS WITH DECISION ( ) HEALTH DEPT ( ) PORT OF SEATTLE () KC. DEV & ENVIR SERVICES-SEPA INFO CNTR ( ) KC. TRANSIT DIVISION - SEPA OFFICIAL () K.C. LAND & WATER RESOURCES () FOSTER LIBRARY () K C PUBLIC LIBRARY ( ) HIGHLINE SCHOOL DISTRICT () SEATTLE SCHOOL DISTRICT ( ) RENTON SCHOOL DISTRICT ( ) HIGHLINE TIMES ( ) CI.TUKWILA.WA.US.VWWV STu r•etr • Dwlsog. ( ) OLYMPIC PIPELINE ( ) VAL -VUE SEWER DISTRICT ( ) WATER DISTRICT #20 () WATER DISTRICT #125 ( ) CITY OF RENTON PUBLIC WORKS () BRYN MAWR- LAKERIDGE SEWERNVATER DISTRICT ( ) RENTON PLANNING DEPT () CITY OF SEA -TAC () CITY OF BURIEN ( ) TUKWILA PLANNING COMMISSION MEMBERS ( ) TUKWILA CITY COUNCIL MEMBERS () CITY OF SEATTLE - SEPA INFO CENTER - DCLU () STRATEGIC PLANNING OFFICE' ' NOTICE OF ALL SEATTLE RELATED PLNG PROJ. () DUWAMISH INDIAN TRIBE () P.S. AIR POLLUTION CLEAN AGENCY () SOUND TRANSIT () DUWAMISH RIVER CLEAN -UP COALITION 'SEND NOTICE OF ALL APPLICATIONS ON DUWAMISH RIVER ( ) SEATTLE TIMES ( ) SOUTH COUNTY JOURNAL M,�:,¢ -h, •g� lI cam, — 611 41) 14 4* • 4 14°444 ti A� a �ru..: P:WDMiNISTRATTVE \FORMS \CHKLIST.DOC )1( P: IADMINISTRATIVi \\FORMS\CHKLIST.DOC PIFIC NOTICE MAILINGS FOR PS'V ITS SEPA MAILINGS Mail to: (comment period starts on date of mailing) Dept. of Ecology Environmental Review Section *Applicant 'Other agencies as necessary (checked off on attached list) 'Any parties of record ' send only the staff report, site plan and the SEPA Determination KC Transit Division — SEPA Official would like to receive information about all projects that might affect transit demand Send These Documents to DOE: SEPA Determination (3 -part from Sierra) Findings (staff report, usu. with MDNS) SEPA Checklist (filled out by applicant) Drawings/Plans of project (site plan, elevations, etc. from PMT's) Affidavit of Distribution (notice was mailed or sent to newspaper) SHORELINE MAILINGS: Notice of Application for a Substantial Development Permit must be mailed to owners and to property owners within 500 feet of subject property, comments are due 30 days after the notice of application is mailed/posted. The notice of Application for Shoreline Substantial Development Permit must include a statement that any person desiring to submit written comments on the application or desiring to receive notification of the final decision on the application may do so within 30 days of the notice of application. If a hearing will be held on the application, the hearing notice must include the information that written comments may be submitted, or oral presentation made at the hearing. Shoreline Permit Notice of Decision: Mail to: (within 8 days of decision; 21-day appeal period begins date received by DOE) Department of Ecology Shorelands Section State Attorney General *Applicant °Indian Tribes •Other agencies as necessary (checked off on attached list). *Any parties of record ' send only the staff report, site plan and the SEPA Determination Send These Documents to DOE and Attorney General; Permit Data Sheet Shoreline Substantial Development Permit (3 -part from Sierra) Findings (staff report or memo) Shoreline Permit Application Form (filled out by applicant) Drawings/Plans of project (site plan, elevations, etc. from PMT's) Site plan, with mean high water mark & improvements Cross- sections of site with structures & shoreline — Grading Plan — Vicinity map SEPA determination (3 -part from Sierra) Findings (staff report or memo) SEPA Checklist (filled out by applicant) Any background studies related to impacts on shoreline Notice of Application Affidavit of Distribution (notice was mailed) From: Sandra Whiting To: Debbie Meisinger Date: 01/26/2007 12:16 PM Subject: Re: Hundhofte Property S 126th St Mitigation Plan CC: brieaaron @comcast.net; Carol Lumb Carol Lumb - Re: Hundhofte Property S 126th St Mitigation Plan Hi Debbie, Page 1 of 2 I have reviewed the revised planting plan. The proposed planting densities are acceptable. Please feel free to contact me (206- 431 -3663) or Carol Lumb (206- 431 -3661) if you have any questions. Sandra Sandra Whiting Urban Environmentalist City of Tukwila Department of Community Development 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 206 - 431 -3663 »> "Debbie Meisinger" <Debbie.Meisinger @kingcd.org> 01/23/2007 12:24 pm »> Hi Sandra, I am writing to you regarding a mitigation plan that a former coworker of mine at the King Conservation District worked on for the Hundhofte Property on 3727 S 126th St. It has been brought to my attention that the plant numbers specified in the plan submitted to the City by KCD are quite a bit inflated for the actual square footage of plantable area. I visited the property a few months back and immediately recognized the extreme desity of the plantings already installed. I then asked to look at the plans for the rest of the planting area and realized that those plant numbers were extraordinarily high as well for the size of the area to be planted, not to mention that there was already a substantial amount of existing native vegetation. I have been working for the Conservation District and on stream and wetland restoration and enhancement projects such as this one for over 5 years. There is a pretty specific formula used to calculate plant quantities. I'm not so sure what happened in the case of this plan. It somehow passed thru without undergoing our normal review process. I have spoken with the property owners about this and they agree that although they are not experts, they were a bit baffled on how to fit so many plants in such a small area and were relieved to have me out and validate their concerns. I went ahead and recalculated the plant quantities based on plantable area also taking into account exisiting vegetation. Attached is a 4 page spreadsheet. The first 2 pages are the exact plant numbers submitted to you in the mitigation plan while the last 2 pages show the revisions that I made and that I would like for you to accept in place file: / /C: \Documents and Settings \CAROL -L \Local Settings\ Temp\ XPGrpWise \45B9F127tuk- mail6300 -... 01/26/2007 Debbie Page 2 of 2 of the originals. Please let me know what you think about this and what other steps might be necesarry in order to get this cleared up. Please do not hesitate to contact me for further information /clarification. Debbie Meisinger King Conservation District 935 Powell Ave SW Renton, WA 98055 te1:425- 277 -5581 x119 fax:425- 277 -5588 file: / /C: \Documents and Settings \CAROL -L \Local Settings\ Temp\ XPGrpWise \45B9F127tuk- mail6300 -... 01/26/2007 Gari?I Lucnb - Hundhofte Property S 126th St Mitigation Plan Page 1 From: "Debbie Meisinger" <Debbie.Meisinger @kingcd.org> To: <swhiting @ci.tukwila.wa.us> Date: 01/23/2007 12:26 pm Subject: Hundhofte Property S 126th St Mitigation Plan CC: <brieaaron @comcast.net> Hi Sandra, I am writing to you regarding a mitigation plan that a former coworker of mine at the King Conservation District worked on for the Hundhofte Property on 3727 S 126th St. It has been brought to my attention that the plant numbers specified in the plan submitted to the City by KCD are quite a bit inflated for the actual square footage of plantable area. I visited the property a few months back and immediately recognized the extreme desity of the plantings already installed. I then asked to look at the plans for the rest of the planting area and realized that those plant numbers were extraordinarily high as well for the size of the area to be planted, not to mention that there was already a substantial amount of existing native vegetation. I have been working for the Conservation District and on stream and wetland restoration and enhancement projects such as this one for over 5 years. There is a pretty specific formula used to calculate plant quantities. I'm not so sure what happened in the case of this plan. It somehow passed thru without undergoing our normal review process. I have spoken with the property owners about this and they agree that although they are not experts, they were a bit baffled on how to fit so many plants in such a small area and were relieved to have me out and validate their concerns. I went ahead and recalculated the plant quantities based on plantable area also taking into account exisiting vegetation. Attached is a 4 page spreadsheet. The first 2 pages are the exact plant numbers submitted to you in the mitigation plan while the last 2 pages show the revisions that I made and that I would like for you to accept in place of the originals. Please let me know what you think about this and what other steps might be necesarry in order to get this cleared up. Please do not hesitate to contact me for further information /clarification. Debbie Debbie Meisinger King Conservation District 935 Powell Ave SW Renton, WA 98055 te1:425- 277 -5581 x119 fax:425- 277 -5588 July 7, 2006 t Cizy of Tukwila MEMORANDUM • Department of Community Development Steve Lancaster, Director TO: Steve Lancaster, Director, Department of Community Development FM: Carol Lumb, Senior Planner RE: L06 -036, Special Permission, Director, Request to Reduce Type 2 Wetland Buffer at 3725 and 3727 S. 126 Street Aaron Hundtofte and Brie Campell, owners of three parcels on S. 126 Street have applied for a 50% reduction in the buffer width for a Type 2 wetland on their property. The wetland, which is approximately 7,500 sq. ft in size, is associated with Riverton Creek, which flows in an open channel just to the east of their property. The portion of the wetland located on the applicant's property (7,500 sq. ft.) will be enhanced along with 4,000 sq. ft. of buffer. Background The site consists of three parcels, one of which is developed with a single family home and a duplex. These structures existed on site prior to the annexation of this area to the City of Tukwila. The applicants also have applied for a boundary line adjustment (L06 -035) to enlarge the parcel on which the two existing structures are located to place the majority of the wetland and locate the parking for the two existing structures on the parcel with the structures. The remaining lot lines would be re- oriented to run east -west to reconfigure the remaining two parcels. Decision Criteria TMC 18.45.080 G. states that the Director may reduce the standard wetland buffer on a case -by- case basis subject to the following criteria. The criteria are identified in italics followed by the response. ° a) The reduced buffer area does not contain slopes over 15 %; The reduced buffer area is primarily flat with a slight slope on the western edge of the buffer. The western-most parcel contains steep slopes on the northwest portion of the parcel, outside of the buffer area. CL q: \Hundtofte BLA \L06 -036 Staff Rpt.doc Page I of 4 07/07/2006 9:56:52 AM Steven M. Mullet, Mayor 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • Phone: 206 - 431 -3670 • Fax: 206 - 431 -3665 Hundtofte Special Permission Director L06 -036 Sensitive Area Departure • b) The buffer reduction is not greater than 50%; The applicant is requesting a buffer of 40 feet for a Type 2 wetland, which is a 50% reduction in the buffer for this type wetland. There is an existing driveway that runs through the proposed reduced buffer area that will remain and continue to provide access to the site from S. 126 Street. The applicants will be using Low Impact Development techniques for most of the driveway, the parking areas for the two new homes and the parking area for the existing homes to reduce . c) Additional protection to wetlands will be provided through the implementation of a buffer enhancement plan; Wetland Resources, Inc. prepared a Sensitive Area Study and Mitigation plan for the applicants in March, 2006. In addition, King Conservation District staff prepared a report, Wetland Mitigation Enhancement project, dated May, 2006, to refine the mitigation plan and provide technical assistance with the planting plan. The City's Urban Environmentalist has reviewed the SAO study, mitigation plan and Conservation District materials and visited the site to meet with the applicants. Taking both reports as a package, the proposed mitigation is acceptable to the Urban Environmentalist, with conditions that are set forth in the Recommendation section below. The implementation of the mitigation plan will result in additional protection to the wetlands and improvement to the functions and habitat value of the wetland. In addition, the applicants have received permission from an adjacent property owner to carry out mitigation off - site, which will provide additional protection to the overall wetland and benefits to the creek. d) The existing condition of the buffer is degraded. The existing wetland is degraded and dominated by Japanese Knotweed, Reed Canarygrass, Himalayan Blackberry and other invasive plants. There are some immature red alder and willow trees as well. The applicant has begun to remove the Himalayan Blackberry and suppress the Reed Canarygrass. The Urban Environmentalist has recommended a different approach applying the herbicide to the control of the Japanese Knotweed. RECOMMENDATION Staff recommends approval of a 50% reduction in the buffer for the Type 2 wetland and the approach for mitigation that is outlined by the King Conservation District report, including the proposed plant spacing, and the approval of a 50% reduction in the buffer for the Type 2 watercourse with the following conditions: 1. In lieu of spraying herbicide to eliminate the Japanese Knotweed, the plant stems must be injected with herbicide, which is an effective control measure and minimizes potential contamination of the wetland and stream. As with any herbicide, only those approved for this use by the EPA and the State are permitted and only according to the instructions on CL Page 2 of 4 07/07/2006 9:56:52 AM q: \Hundtofte BLA \L06 -036 Staff Rpt.doc Hundtofte Special Permission Director L06 -036 Sensitive Area Departure • the label. More information on control of Japanese Knotweed can be found in the document prepared by The Nature Conservancy located on the internet at: http: / /tncweeds. ucdavis .edu /moredocs /polspp01.pdf. 2. The plant list provided in the Conservation District plan must be used in lieu of the plant list provided in the Sensitive Areas Report. Plant substitution is acceptable, provided that native plants are used and the plants are appropriate for the hydrologic regime. 3. A planting plan must be provided for the wetland and buffer area. It is acceptable to provide a simple planting plan that identifies approximate zones for planting the different combinations of plants and the number of plants in each zone. 4. A report summarizing the site inspection after the plantings must be provided. There are two options for providing the City this report: either the King Conservation District staff may inspect the site or a wetland biologist or landscape professional must inspect the plantings. The report must be provided within 15 days of the inspection. 5. Annual maintenance and monitoring reports must be provided to the City for five years as discussed in the Sensitive Areas Study. 6. The performance standards as stated in the Sensitive Areas Study and Mitigation Plan are acceptable for this site: 1) 75% survival of installed plants at the end of the 5 year and 2) 60% areal coverage of tree sapling /shrub stratum. 7. A performance bond in the amount of 150% of the cost of the plant materials must be provided at the time of final City inspection of the implemented planting plan. 8. Record the wetland and buffer delineation with King County Records and Elections and provide a copy to the City. Attachments: o June 16, 2006 Memorandum from Sandra Whiting, Urban Environmentalist. o Sensitive Area Study and Mitigation Plan, prepared by Wetland Resources, Inc. March 6, 2006. o Hundtofte /Campbell Wetland Mitigation Enhancement Project, prepared by Amy Tippery, King Conservation District, May, 2006. CL Page 3 of 4 07/07/2006 9:56:52 AM q: \Hundtofte BLA \L06 -036 Staff Rpt.doc CITY OF TUKWILA NOTICE OF APPLICATION PROJECT_ INFORMATION Aaron Hundtofte has filed a Special Permission, Director application to reduce the wetland buffer for a Type 2 wetland on property located at 3727 S. 126th Street, Tukwila Permits applied for include: L06 -036, Special Permission, Director; L06 -035, Boundary Line Adjustment Other known required permits include: public works permit for site work; building permits for new homes Studies required with the applications include:< Sensitive Area Study and Mitigation Plan prepared by Wetland Resources, Inc. dated March 6, 2006; Wetland Mitigation Enhancement Project, prepared by Amy Tippery, King Conservation District; Storm Water Technical Information Report, prepared by TLP Pacific, LLC. An environmental checklist is not required for this project. FILES AVAILABLE FOR PUBLIC REVIEW The project files are available at the City of Tukwila. To view the files, you may request them at the counter at the Department of Community Development (DCD), located at 6300 Southcenter Boulevard #100. Please call ahead to 206431 -3661 to assure the availability of the files. Project Files include: L06 -036, Special Permission, Director; L06 -035, Boundary Line Adjustment OPPORTUNITY "FORPUBLIC COMMENT Your written comments on the project are requested. They must be delivered to DCD at the address above or postmarked no later than 5:00 P.M., Wednesday, July 5, 2006. APPEALS You may request a copy of any decision, information on hearings, and your appeal rights by calling DCD at (206) 431 -3670. The decision on the boundary line adjustment may be appealed to the City of Tukwila Hearing Examiner; the Special Permission Director decision may be appealed to the Tukwila Planning Commission. For further information on this proposal, contact Carol Lumb at (206) 431 -3661 or visit our offices at 6300 Southcenter Boulevard, Suite #100, Monday through Friday, 8:30 a.m. to 5:00 p.m. Application Filed: May 15, 2006 Notice of Completeness Issued: May 22, 2006 Notice of Application Issued: June 21, 2006 CL Page l of 1 q:\Hundtofe\NOA.doc 06/20/2006 4:35:00 PM Project: Kor•at0 % A Address: 3125 ' 31.1n 6, IV St. Date transmitted: 5 Iq Response requested by: (r - 7 -04 Staff coordinator: GGt ✓Jl Date response received: TO: r-21 Building See Plan check date: ( ((i/o(, • City of Tukwila Department of Community Development LAND USE PERMIT ROUTING 'Sand r• rve Planning Public Works !Fire Dept. • P REVIEWERS: Please specify how the attached plans conflict with your ADOPTED development regulations, including citations. Be specific in describing the types of changes you want made to the plans. When referencing codes, please identify the actual requirement and plan change needed. The Planning Division review does not supplant each department's ability to administer its own regulations and permits. However, project consistency at the Planning review stage is important to minimize significant later design changes. More than minimal design changes require further Planning Commission review, even if alteration is required to satisfy a City requirement. This further review is typically a minimum 60 -day process. Requirements based on SEPA (e.g., not required by an adopted development regulation) MUST identify the impact being mitigated, the policy basis for requiring mitigation, and the method used to calculate the mitigation required. Calculations of project impacts and the mitigation required (e.g., water capacity, road level of service analyses, or turning analyses) may be required of the applicant. COMMENTS (Attach additional comment sheets and/or support materials as needed.) Comments s Update date: prepared by: File Number 1_06- 035 &La, t..0 G - 0 36 Seeciwl Aimisssck bveacr auffrr r2otuc FORM olice Dept. L Parks /Rec MEMORANDUM June 16, 2006 To: Carol From: Sandra Re: Hundtofte BLA, L06- 035/L06 -036, Comments on Wetland /Stream Buffer Mitigation Plans I visited the site on June 15 to confirm the wetland boundaries. The wetland flags are no longer in place, so I could only go on the basis of the drawing provided by the applicant, which shows that the boundary was determined to follow the edge of the toe of the slope that faces east. I agree that these boundaries appear to be correct as shown on the site plan. The applicant has made significant progress on removal of invasive species and planting of native plants both in the buffer and in the wetland adjacent to Riverton Creek. The applicant received permission from one of the adjacent property owners to carry out mitigation on the off -site portion of the wetland. I have the following comments on the " Sensitive Area Study and Mitigation Plan" prepared by Wetland Resources, Inc., dated March 6, 2006; and the Wetland Mitigation Enhancement Project, prepared by the King Conservation District, dated May, 2006. Despite problems in the quality of the Sensitive Area Study and Mitigation Plan, the whole package presented for the wetland and buffer enhancement approach is adequate, with the King Conservation District report as a complement. The approach for mitigation that is outlined by the King Conservation District is acceptable, including the proposed plant spacing, with the following qualifications. 1. In lieu of spraying herbicide to eliminate the Japanese Knotweed, it is recommended that the plant stems be injected with herbicide. This has been shown to be an effective control measure and minimizes potential contamination of the wetland and stream. As with any herbicide, only those approved for this use by the EPA and the State are permitted and only according to the instructions on the label. More information on control of Japanese Knotweed can be found in the document prepared by The Nature Conservancy located on the internet at: http://tneweeds.ucdavis.edu/moredocs/polspp0 I .pdf. 2. Using cardboard or other barrier material for Reed Canarygrass control, and then delaying planting until the grass has been killed is a logical approach. I recommended in a prior conversation with the applicant to start this control as soon as possible, and in fact, observed during the site visit that it has already been started. 3. The plant list provided in the Conservation District plan is preferred over that provided in the Sensitive Areas Report. It is important to have an herbaceous layer, which the Sensitive Areas Report lacks. Also, many of the plants recommended by the Conservation District, in addition to being valuable for habitat purposes, are also very ornamental, which would be an additional aesthetic benefit to the proposed development and would hopefully contribute to the appreciation of the wetland and wetland buffer by the future homeowners. Plant substitution is acceptable, provided that native plants are used and the plants are appropriate for the hydrologic regime. 4. To make it easier for the applicant to carry out plant installation, a simple planting plan is recommended (perhaps by the Conservation District). It does not need to show the exact locations of each plant, but rather it should indicate approximate zones for planting the different combinations of plants. 5. It is our understanding that the King Conservation District will visit the site in the late fall after much of the weed control and planting have been done. If this is the case, hiring a wetland biologist or landscape professional to inspect the plantings would not be necessary in my opinion, but the City should get a copy of any report prepared by the Conservation District. The City could also inspect the site after the majority of weed control and planting have been done and again after all planting has been completed. 6. If the applicant is willing to provide annual maintenance and monitoring reports to the City, as discussed in the Sensitive Areas Study, it should not be necessary to hire a professional to do so. The City could inspect periodically to verify the conditions described in the reports. 7. The performance standards as stated in the Sensitive Areas Study and Mitigation Plan are acceptable for this site: 1) 75% survival of installed plants at the end of the 5 year and 2) 60% areal coverage of tree sapling/shrub stratum. From: Sandra Whiting To: Brieaaron@comcast.net Date: 6/16/06 10:15AM Subject: Planting along ditch, knotweed control, contact for LID Hi Aaron and Brie, It was nice meeting you earlier this week and seeing all your progress on the wetland and buffer enhancement. Keep up the good work! I have left a message with our stormwater maintenance person regarding your desire to plant along the ditch on S. 126th. As I said, I wouldn't plant anything on the City's right -of -way until you hear back from us about this. Regarding a contact at the City of Seattle to see if you can get some suggestions for stormwater engineers with LID experience, you might try calling Seattle Public Utilities (general number is 206 - 684 -3000) and asking to speak with Denise Andrews. Here is the Nature Conservancy site for the Knotweed control manual. I don't know if it will give you any more information over what the Conservation District gave you, but it may be useful. There is a lot of information on control of other weeds too, if you go to the main website. http: / /tncweeds. ucdavis .edu /moredocs /polspp01.pdf Good Luck! Sandra Whiting Sandra Whiting Urban Environmentalist City of Tukwila Department of Community Development 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 206 -431 -3663 CC: Carol Lumb May 22, 2006 Mr. Aaron Hundtofte 3727 S. 126 Street Tukwila, WA 98168 RE: L06 -035 Hundtofte Boundary Line Adjustment, and L06 -036 Special Permission Director Applications Dear Aaron: Your applications for a boundary line adjustment and Special Permission Director for a reduction in sensitive area buffer located at 3727 S. 126 Street have been found to be complete on May 22, 2006 for the purposes of meeting state mandated time requirements. I will be the planner for these two project files. This determination of complete application does not preclude the City from requesting additional plans or information, if in our estimation such information is necessary to ensure the project meets the substantive requirements of the City or to complete the review process. The applications have been circulated to the City's Urban Environmentalist, and the Fire and Public Works Departments for review. I expect comments back within 3 weeks and will be in touch with you if there are any questions or comments about the two applications. If you have any questions in the meantime, please feel free to call me at 431 -3661. Sincerely, Carol Lumb Senior Planner cc: Reviewing City Departments CL q: \Hundtofte BLA \Complete.doc s • City of Tukwila Department of Community Development Steve Lancaster, Director NOTICE OF COMPLETE APPLICATION Page 1 of 1 05/22/2006 2:14 PM Steven M. Mullet, Mayor 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • Phone: 206 - 431 -3670 • Fax: 206 - 431 -3665 From: Sandra Whiting To: Brieaaron @comcast.net Date: 6/28/06 4:07PM Subject: Wetland /Stream enhancement along ditch on S 126th Aaron and Brie, I finally was able to talk in person to our stormwater maintenance staff person about your desire to plant along the stormwater ditch. His response was that you should not plant anything in the ditch or immediately on either side, as the city periodically cleans out the ditch and also mows along the City right -of -way. However, you could put down materials to cover the invasive plants. You could also plant trees and shrubs that would shade the ditch, as long as they are not on the right -of -way and the roots don't grow into the ditch. He also suggested that anything you plant near the ditch be flagged to draw attention to it, in the event that the City crew goes out to mow along the right -of -way. I hope this information is helpful. Sandra Whiting Sandra Whiting Urban Environmentalist City of Tukwila Department of Community Development 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 206 -431 -3663 CC: Carol Lumb • • From: Sandra Whiting To: Brieaaron @comcast.net Date: 6/16/06 10:15AM Subject: Planting along ditch, knotweed control, contact for LID Hi Aaron and Brie, It was nice meeting you earlier this week and seeing all your progress on the wetland and buffer enhancement. Keep up the good work! I have left a message with our stormwater maintenance person regarding your desire to plant along the ditch on S. 126th. As I said, I wouldn't plant anything on the City's right -of -way until you hear back from us about this. Regarding a contact at the City of Seattle to see if you can get some suggestions for stormwater engineers with LID experience, you might try calling Seattle Public Utilities (general number is 206- 684 -3000) and asking to speak with Denise Andrews. Here is the Nature Conservancy site for the Knotweed control manual. I don't know if it will give you any more information over what the Conservation District gave you, but it may be useful. There is a lot of information on control of other weeds too, if you go to the main website. http://tncweeds.ucdavis.edu/moredocs/polspp01.pdf Good Luck! Sandra Whiting Sandra Whiting Urban Environmentalist City of Tukwila Department of Community Development 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 206 -431 -3663 CC: Carol Lumb • • June 9, 2005 Mr. Aaron Hundtofte Ms. Brie Campbell 3727 S. 126 Street Tukwila, WA 98168 Dear Aaron and Brie: CL q: \General \Hundtotte.doc • City of Tukwila • Department of Community Development Steve Lancaster, Director RE: Paving Access to Lot 7, Block 9, Riverton Plat Steven M. Mullet, Mayor Thank you for your letter of April 27, 2005, which included a conceptual wetland mitigation plan for your property on South 126 Street. You have requested guidance on the process for improving the existing gravel driveway that provides access to the two houses, as the driveway is located within the buffer of a Type 2 wetland located on the northeastern portion of the site. The process for considering your request to maintain the driveway in its current location would be to submit a Special Permission Director application to request a reduction in the wetland buffers — an application is attached to this letter for your use. For sensitive area deviations, you are to provide the following: 1. Two copies of a site plan as described on the attached application. The site plan should identify the parking area for the current residences and anticipate future parking needs should any additional development take place on the site. 2. Two copies of a complete wetland delineation report and mitigation plan. Chapter 18.45, Sensitive Areas Overlay district provides guidance on the contents of sensitive area studies. Please revise the conceptual mitigation plan to present a clear, detailed proposal for enhancement of the wetland and the buffer. The enhancement plan will include objectives of the mitigation plan, a planting plan with types of plants, sizes and quantity and other habitat features of the proposal. The plant material to be used should be native to the Pacific Northwest. The enhancement plan should also discuss the removal of invasive plants — how that will be accomplished (by hand, with machinery etc) and where the invasive materials will be disposed and ongoing maintenance of the mitigation area. As part of the mitigation plan you will be required to identify the buffer area with split rail fencing and signage to protect the area from encroachment. Page 1 of 2 06/09/2005 4:35 PM 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • Phone: 206 - 431 -3670 • Fax: 206- 431 -3665 Mr. Aaron Hundtofte Ms. Brie Campbell June 9, 2005 CL • You will be required to record the site plan clearly delineating the wetland and buffers with King County Records and Elections, as noted in TMC 18.45.200. You also will be required to monitor the mitigation area for five years and provide a yearly report to the City on how well mitigation plan is working and replace plants that have died. A bond will be posted for the five -year monitoring period to ensure that the enhancement plan will be maintained. 3. Information on the permeable surface proposed to be used to pave the driveway, special installation requirements and a list of qualified installers in the area. 4. Please identify where you anticipate new property lines might be located if you proceed with a boundary line adjustment or short plat. Please call me at 206 -431 -3661 if you have any questions. Sincerely, Carol Lumb Senior Planner Enclosure cc: Nora Gierloff, Planning Manager Sandra Whiting, Urban Environmentalist Jill Mosqueda, Development Engineer, Public Works Dept. q:\Generallfundtofte.cloc Page 2 of 2 06/09/2005 4:35 PM • t 9532 12 Avenue NE May 8, 2006 Project No. 06 -041 Mr. Aaron Hundtofte & Ms. Brie Campbell 3725 South 126 Street Tukwila, WA 98168 • • Subject: Subsurface Exploration and Geotechnical Engineering Study Proposed Short Plat 3725 South 126 Street, Tukwila, Washington This report presents the results of our geological /geotechnical evaluation of the property located at the above referenced address in Tukwila, Washington. It is our understanding that the subject property will be subdivided, creating two additional building lots along the west side of the property. The existing driveway will remain in its approximate location but will be improved to serve the additional lots. Permeable pavement will be used to surface the driveway. Storm water runoff will be handled through the permeable pavement system and the underlying crushed rock base materials. The discussions presented this report address the geotechnical aspects of the planned development and the infiltration potential of the sediments underlying the driveway area. The purpose of our site evaluation was to document existing shallow soil and ground water conditions on the property, and to provide gcotechnical recommendations for design and construction of the proposed improvements. The scope of our study includes; 1) discussion of development scope and details with the owner and project civil engineer, 2) research of geologic and soils mapping information in our files, 3) exploration of subsurface conditions using hand dug exploration pits and probing, 4) geologic and engineering evaluations, and 5) preparation of this report. Development plans include construction of two new single family dwellings on the west side of the property in order to meet setback requirements from the wetland located on the northeast portion of the property. In addition to the houses, a new storm water management system consisting of permeable pavement over the driveway and a bioswale along the east side of the driveway are planned. The two existing homes on the property will rcmain as is. A site plan and topographical survey, by Land Surveying, Planning & Platting, was provided and used for elevation and location datum referenced our study. Gary A. Flowers, PLLC. Shoreline, Washington 98155 -1106 206- 417 -7640 C. la — .au I — O0 T.7 Gary A. Flowers, PLLC Geological & Geotechnical Consulting 19532 12 Avenue NE Shoreline, WA 98155 -1106 P. Surface Conditions Explorations 19532 12 Avenue NE BOH @ 4.0 feet No caving No ground water seepage • • Hundlafle/Camphell Short Plat Geological /Geotechnical Services Report 3725 South 126 Street, Tukwila, Washington The subject property is located in the north area of Tukwila, west of the Green River and east of Highway 99 (Tukwila International Blvd). The parcel is relatively flat lying at the top, southwestern portion of the site and slopes gently downward to the east and northeast. There is also a relatively steep, but short (less than 10 feet) slope downward to the south along the south property line. Total relief on the site is about 18 feet from southwest to northeast. 'Total relief in the area of the proposed new lot at the southwest corner is only about 2 feet and for the northwest lot relief is about 6 feet. The existing driveway slopes down to the north to S 126` Street at a gradient of about 11 percent. The property is residential and currently supports two wood framed residences on the southeast portion of the site. Vegetation on the site consists of trees, brush and grass. A wetland is located in the northeast portion of the site. We understand that the wetland has been recently improved by removal of bramble bushes and replanting with native wetland plants east of the existing driveway under the supervision of the city biologist. Field explorations at this site were conducted on April 11, 2006. Subsurface information was obtained in six (6) hand or power auger holes. The explorations were placed to characterize subsurface conditions over the anticipated future development area and the driveway improvement/storm water management area. Hole depths ranged from about 1.5 to 4.0 feet below existing grade. Probing of the pit bases was performed with a 1/2" steel `I' probe to determine the depth to firm, non - yielding soils. Probe refusal depths were approximately the same as the auger depth. Exploration locations were established from available reference points. Records of soil types and conditions encountered in the explorations were maintained in the field and are summarized in the following hand pit logs. Soils observed in the explorations were visually identified in the field by a licensed engineering geologist from this office. HA -1 Located near southwest corner of existing gravel parking pad. Ground surface elevation approx. 116 feet. 0.0 — 4" Crushed rock/recycled concrete mix — approximately 7/8" diameter material (fill) 4" — 8" Medium dense, moist, blackish - brown, sandy silt with occasional gravel (fill) 8" — 4' Medium dense to dense with depth, moist, brown, sandy silt with gravel and occasional cobbles to 4" diameter (glacial till) Cary A. Flowers, PLLC. Shoreline, Washington 98 155 -1 106 206 -417 -7640 r • .3 Hundtofte/Campbell Short Plat (Geological /Geolechnical Services Report 3725 South 126 Street, Tukwila, Washington HA -2 Located in area of proposed house on new lot 1. Ground surface elevation approx. 114 feet. 0.0 - 2.5' Loose, moist, black, very organic, silty loam to sandy loam (topsoil) 2.5' — 3.0' Medium dense to dense, moist, brown, sandy silt with gravel and occasional cobbles to 4" diameter (glacial till) HA -3 Located in area of existing parking on west side of property near south edge of proposed house on new lot 1. Ground surface elevation approx. 115 feet. 0.0 -4" 4" — 4.0' HA -5 0.0 -5" 5" — 16" HA -5 0.0 -5" 5" — 16" 19532 12 Avenue NE —r • • BOH @ 3.0' No caving No ground water seepage Crushed rock/recycled concrete mix — approximately 7/8" diameter material (fill) Medium dense to dense, moist, brown, sandy silt with gravel and occasional cobbles to 4" diameter (glacial till) BOH @ 3.0' No caving No ground water seepage CUO - Jb / - bn'tn HA-4 Located in lawn area just south of existing shed in area of proposed house on new lot 2. Ground surface elevation approx. 117 feet. 0.0 — 2" Grass Sod 2" — 3' Medium dense to dense, moist, brown, sandy silt with gravel and occasional cobbles to 4" diameter (glacial till) BOH @ 3.0' No caving No ground water seepage Located in driveway area. Ground surface elevation approx. 110 feet. Crushed rock/recycled concrete mix — approximately 7/8" diameter material (fill) Dense to very dense, moist, brown. sandy silt with gravel and occasional cobbles to 4" diameter (glacial till) BOH @ 16" No Caving No ground water seepage Natural gas line punctured Located in driveway area. Ground surface elevation approx. 104 feet. Crushed rock/recycled concrete mix — approximately 7/8" diameter material (fill) Dense to very dense, moist, brown, sandy silt with gravel and occasional cobbles to 4" diameter (glacial till) BOH @ 16" No Caving No ground water seepage Gary A. Flowers, PLLC. Shoreline, Washington 98155.11116 206417.7640 3 p.4 • HundtoJle/Campbell Short Plat 3725 South 126th Street, Tukwila, Washington • • Geologic Mapping and Subsurface Conditions GVO - oo / - O.7YA (ieological/Geotechnical Services Report Landforms in this region comprise a system of erosion modified, glacially sculpted features. Deposits of glacial till and outwash sediments from the last glaciation of the area overlie materials from earlier glaciations. The latest occurrence of glacial ice within the vicinity is thought to have taken place during the later stages of the Pleistocene Epoch (some 11,000 to 12,000 years ago), and is referred to as the Vashon Stade of the Fraser Glaciation. Some 3500 to 4500 feet of ice is thought to have overlain the region during this period. According to the Geologic Map Of King County, Washington, by Booth, Ilaugerud and Socket, 2002, the terrain in this vicinity is shown to be formed over Vashon age glacial till deposits. Our explorations and observations find the geology at this site to he generally consistent with the published mapping of the area. Our explorations encountered 30 inches of highly organic silty loam to sandy loam on the west side of the driveway in the area of proposed lot 1. This area appears to have been a garden area in the past and is not representative of the remainder of the site. A layer of crushed rock and recycled concrete mix overlies the native soils in the existing parking and driveway areas. This material was underlain by about 4 inches of blackish brown sandy silt with occasional gravel in HAI. We interpret this soil to he fill materials. Elsewhere on the site, either weathered or unweathered glacial till sediments were encountered. Ground Water Ground water seepage was not encountered in any of the explorations completed for this study. We suspect that the some ground water seepage may be encountered during wet periods of the year as interflow. This condition occurs as surface water migrates through the looser, more permeable artificial fill and weathered zone soils, and "perches" atop the impermeable, dense parent material. Depending on the slope of the ground surface (and soil interface contact) within an area, the collected ground water may remain stationary, or migrate down gradient along the interface atop the dense parent material. Interflow is most active during the winter months, or periods of prolonged rainfall. During these times, infiltration of perched ground water into sandy seams or pockets may occur within the dense parent materials. Interflow is considered to be localized, and is not an indication of a larger (regional) ground water recharge condition. This condition tends to be seasonal, and the level of activity generally decreases significantly (or disappears) during the dry season. 19532 12 Avenue NE Cary A. Flowers, PLLC. Shoreline, Washington 98155 -1106 206- 417 -7640 4 p. b Luu JV I • • Seismic Hazards Hundtofte/Campbell Short Plat CeologicaU(ieotechnicolServices Report 3725 South 126 Street, Tukwila, Washington Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture; 2) seismically induced landslides; 3) liquefaction; and 4) ground motion. The potential for each of these to impact this site is discussed below. The nearest known fault in this region is the Seattle Fault Zone which passes east -west, through Alki Point and the southern extent of Lake Sammamish. The exact locations of all splays of this fault zone are unknown, but are likely within about 6 miles of this site. These faults are being currently studied by the United States Geological Service (USGS), and have been determined to be active and capable of producing large earthquakes. Much is still to he learned about structural details and seismic activity along these fault systems, but it is generally hypothesized that the large earthquake recurrence interval is several thousand years. Due to the suspected long recurrence interval and the distance to the suspected fault zone, the potential for surficial ground rupture is considered to be low during the expected life of the proposed structures. Due to the very high density of the glacial till materials it is our opinion that the potential risk of damage to the proposed structures, by either seismically induced landsliding or liquefaction, is low. In accordance with the 2003 International Building Code, Table 1615.1.1, the subject site is defined as Site Class C. CONCLUSIONS AND RECOMMENDATIONS Based on our observations and explorations the site is underlain at depth by dense or better, glacially consolidated sediments. These materials will provide suitable bearing for proposed residences. The thick layer of highly organic silty loam to sandy loam encountered along the west side of the driveway is unsuitable for foundation or slab support and must he removed from the building site. Site Grading and Subgrade Preparation Based on our understanding of the planned development, we anticipate that significant regrading will not be required on either of the subdivided lots. Removal of the highly organic soils will be required within the building pad of Lot I . This material is excellent topsoil material and should be kept on site for landscaping purposes. This will result in an approximate 4 foot high foundation wall along the west side of the house footprint. Otherwise preparation of building sites will primarily involve removal of any existing fill and very loose, root laden soils in foundation areas and other weight bearing or settlement sensitive areas. Any disturbed soils in the foundation areas should either be removed or recompacted to a dense, unyielding condition. 19532 12 Avenue NE Cary A. Flowers, PLLC. Shoreline, Washington 98155 - 1106 206 - 7640 5 p. b Hundtofte/Campbell Short Plat Gc ological /Geoiechnical Services Report 3725 South /26` Street, Tukwila, Washington Site grading work is best performed during the drier summer months as the native surJiciai soils are very fine grained and will be very moisture sensitive and easily disturbed when wet. Once disturbed, this material will not be easily recompacted and will likely have to be used in non- critical landscaped areas. It will be incumbent upon the contractor to plan site development to minimize subgrade disturbance. Any necessary grading for the driveway portion of the project should he in compliance with City of Tukwila standards. Prior to placement of the required pavement section the subgrade soils should be proofrolled to verify their stability under traffic loads. The proofroll should only be conducted during dry weather conditions and should be conducted with a fully loaded. tandem axle dump truck. Any soft or pumping soils should be removed and replaced with compacted structural fill. Structural Fills Structural fill is defined as non - organic soil, acceptable to the gcotcchnical engineer or engineering geologist, placed in maximum 10 -inch loose lifts, with each lift being compacted to a dense and unyielding condition prior to placement of the succeeding lift. Any yielding material, whether it meets the compaction standard or not, should eithcr be scarified. allowed to dry to optimum moisture content and then recompacted or else removed from the structural fill. Utility trench backfill in any roadway areas should be completed in accordance with the local municipality's standards and specifications. The on -site native soils are very fine grained and moisture sensitive. These materials should not be used in structural fills during rainy weather or in wet subgrade areas. Construction during wet weather or wet subgrade conditions will require use of imported, high quality granular materials for use in structural fills. Wet weather fill should consist of a well graded, free draining pit run sand and gravel material with less than 5 percent fines (minus #200 sieve size Temporary Excavations 19532 12 Avenue NE • • It should be the responsibility of the contractor to maintain safe slope configurations since the contractor is continuously on -site. For planning purposes we anticipate that the dense to very dense glacial till soils can be excavated at approximately .511:1 V (horizontal to vertical) provided that heavy equipment and soil stockpiles are kept away from the edge of the excavation a distance at least one -half the height of the excavation. The upper, weathered sediments will need to be sloped at a maximum inclination of 1 H:1 V. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to he adjusted in the field. It may be necessary to cover the sides of temporary slopes with plastic or otherwise protect them from the elements to minimize sloughing and erosion. 6 uo Gary A. Flowers, PLLC. Shoreline. Washington 98155 -11116 206 -417 -7640 P. 7 Nundtofle/Campbell Short Plat Geo logical /Geotechnical Services Report 3725 South 126' Street, Tukwila, Washington Foundation Recommendations Shallow spread footings founded on the dense, natural glacial soils should provide a commonly acceptable level of support for the proposed new dwellings. Disturbed soils must he either removed or recompacted prior to concrete placement. A net allowable design soil bearing pressure of 2500 psf should be used for footings founded on appropriately prepared glacial soils. Ground settlement due to foundation loads should be less than one (1) inch total and one -half (1/2) inch differential over the building areas. For short term dynamic loads, a reduction of the factor of safety would be appropriate at this site, and a resultant increase of one -third for the above recommended bearing pressures may be used. The suggested soil bearing pressures are based on the following conditions: Footing areas should be inspected by this office prior to placement of concrete to verify that the type and condition of the bearing soils are consistent with the recommendations of this report. Lateral loads may be resisted by friction at the base of the footings, and as passive pressure on the sides of adequately embedded footings. We recommend that an allowable coefficient of friction of 0.35 be used to calculate friction between the concrete and the underlying soil. Passive pressure may be determined using an allowable equivalent fluid density of 300 pcf when the footings are backfilled with compacted structural fill. These values are allowable and include a factor of safety of at least L5. 19532 12 Avenue NE • • 1. All footings should be founded into the natural glacial soils as described above. 2. All footing excavations should be prepared such that a dense, non - yielding, uniform soil condition has been established prior to placement of footing concrete. 3. All footings should extend through any existing artificial fills or modified zones and exterior footings should be placed to bear a minimum of 18 inches below finished adjacent exterior grade for frost protection. 4. All footings should be sized according to the anticipated wall or column loadings, and the above soil bearing value. Minimum footing widths should comply with current International Building Code (IBC), or City of Tukwila standards. 5. All footings should be free of ponded water and sloughed or water loosened soils prior to placement of footing concrete. Cary A. Flowers, PLLC. Shoreline. Washington 98155 - 1106 206 - 417 - 7640 7 LVO - J0 / - 00 . TO P.a llundtof e/Camphell Short Plat Geological /Geotechnicul Services Report 3725 South 126 Street, Tukwila, Washington Retaining Walls We are unaware of any retaining walls that proposed for the project. For planning purposes retaining walls up to 8 feet in height that are free to rotate may be designed for an active equivalent fluid pressure of 35 pcf with a level backfill. If the walls are restrained and unable to rotate they should be designed for an at rest pressure of 55 pcf for level backfill. "Traffic, equipment, residential footings or slope surcharges should be added to these values by the design engineer. Any retaining walls or landscape walls over 3 feet in height must be lined with a minimum of 12 inches of washed rock to within 1 foot of finish grade or an approved drainage mat such a MiraDrain or IncaDrain. The washed rock or drainage mat must hydraulically connect to the footing drain. Floor Slabs • • Slab -on -grade concrete floors may be placed atop suitably prepared and compacted natural site soils other than the highly organic soils observed along the west side of the driveway. Any material that has been disturbed and is not dense or non - yielding should either he recompactcd or removed and replaced with structural fill. A capillary break layer consisting of 4 inches of washed pea gravel and a heavy duty (minimum 10 mil), polyethylene plastic vapor barrier should be provided under any floor slabs where moisture intrusion is a concern. if the vapor barrier becomes compromised in any way during construction it should he replaced or an additional layer added. Penetrations through the vapor barrier should be wrapped and taped. Site Drainage We understand permeable pavement will be utilized for the driveway enhancement. Permeable pavement allows storm water to penetrate through the pavement into the underlying crushed rock support section. Storm water is thus stored both within the permeable pavement and the crushed rock section and slowly infiltrates into the underlying natural sediments on the site, if suitable. Our explorations indicated that the underlying natural sediments arc not suitable for infiltration of storm water. The sediments contain a significant percentage of fine grained material and arc dense to very dense. As such the design engineer must accommodate the design storm water event runoff without relying on infiltration into the subgrade soils. The subgradc soils in the area of the driveway also may become unstable when saturated and subjected to traffic loading. As such, a suitable thickness of crushed rock should be placed beneath the permeable pavement to provide separation and stability from the underlying soils. In addition, we recommend that a geotextile filter fabric or subgrade stabilization fabric he placed atop the subgrade soils prior to placement of the crushed rock. 19532 12 Avenue NF Gary A. Flowers, PLLC Shoreline. Washington 98155 206 - 417.7640 8 F+ • • Hundtofte/Campbell Short Plat Geolox'icauGeolechnical Services Report 3725 South 126" Street, Tukwila, Washington Manufacturer's installation instructions should always be followed for permeable pavement. However, typical installations for pavement in this area would include a minimum of 4 inches of compacted crushed rock for concrete pavement and 6 inches for asphalt pavement on a stable subgrade. For permeable pavements on a potentially unstable subgrade the crushed rock section should be increased. The design engineer should also determine if additional storage capacity is required within the crushed rock and increase the section accordingly. All permeable pavements require that the surface of the pavement he kept clean such that fine grained sediment does not plug up the pore spaces of the pavement_ Regular routine maintenance (sweeping and pressure cleaning) should be performed. All perimeter foundations should be provided with a drain at the footing level. Drains should consist of rigid, perforated, PVC pipe surrounded by washed pea gravel. The pipes should always be placed such that the perforations are located on the lower one -third of the pipe section. The level of the perforations in the pipe should be set approximately 2 inches below the bottom of the footing at the highest point and the drains should be constructed with sufficient gradient to allow gravity discharge away from the buildings. Roof and surface runoff should not discharge into the footing drain system but should be handled by a separate, rigid, tightline drain that discharges into an approved storm water conveyance system. In planning, exterior grades adjacent to walls should be sloped downward away from the structure to achieve surface drainage. Erosion Protection The weathered till soils contain a significant amount of fines and arc considered to be moisture sensitive and may be prone to erosion if exposed to channelized flow. Erosion control measures should include silt fences along the lower portions of the development areas. The silt fences should be placed as per local municipal specifications and properly maintained. Soil stockpiles should be covered with plastic during periods of inclement weather. Areas stripped of vegetation and exposed backfill should be covered with plastic when not being worked. The construction entrance should be rocked to minimize off -site soil transport. SUMMARY cuo i -004.0 P. lU, 19532 l2` Avenue NF . • Based on our observations and subsurface explorations, this site appears to be suitable for the proposed development provided the recommendations presented herein are properly implemented. We recommend that we be retained to review those portions of the plans and specifications that pertain to grading or foundation installations to determine that they are consistent with the recommendations of this report. Construction monitoring and consultation services should also be provided to verify that subsurface conditions arc as expected. Should conditions be revealed during construction that differs from the anticipated ground conditions, we will evaluate those conditions and provide alternative recommendations where appropriate. Gary A. Flowers, PLLC. Shoreline, Washington 95155 -I 1(16 206 -417 -76411 9 Hunt/ toile/Campbell Short Plat Geological /Geotechnical Services Report 3725 South 12e Street, Tukwila, Washington Field construction monitoring and observation services should be considered as an extension of this initial geotechnical evaluation, and are essential to the determination of compliance with the project drawings and specifications. Such activities would include observation of excavations, subgrade preparation for foundations, subsurface drainage, fill placement and compaction. Our fmdings and recommendations provided in this report were prepared in accordance with generally accepted principles of engineering geology and geotechnical engineering as practiced in the Puget Sound area at the time this report was submitted. We make no other warranty, either express or implied. Sincerely, I Gary A. Flowers Gary A. Flowers, P.G., P.E.G. Principal Engineering Geologist 19532 12 Avenue NE • Gary A. Flowers, PLLC. Shoreline. Washington 98155 - 1106 206417 - 7640 I0 � uu u aa 1 — o.a� U P. 11 Aaron Hundtofte and Brie Campbell 3727 S.126 St. Tukwila, WA 98168 • . April 27 2005 Re: Improving lot 7, Block 9 Riverton Plat (S. 126 St.) Dear Planning Department, As per our conversations please find enclosed the following: RECEWF !APR 2 7 2005 COMMUNITY DEVELOPMENT - a letter from Wetlands Resources with improvement suggestions that minimizes the impact of the required improved driveway (Low Impact Development) and applies Best Available Science. Please note the suggestion of an intense Buffer enhancement along the eastern border of the driveway and the suggestion of using a permeable product for paving. - a map with an 80 foot buffer and 40 foot buffer marked. - an informational pamphlet on one particular pervious product that is currently being used in Washington. We look forward to your input and reply. Thank you for your assistance and time thus far. Regards, Wt/awdRp,sorces,/rnc. f • Delineation / Mitigation / Restoration / Habitat Creation / Permit Assistance BRIEF CONCEPTUAL MITIGATION PLAN FoR HUNDHOFTE PROPERTY - S. 126'" STREET City of Tukwila, Washington Wetland Resources, Inc. Project #05041 Prepared By: Wetland Resources, Inc. 9505 19th Ave. SE Suite 106 Everett, WA 98208 (425) 337-3174 For: Mr. Aaron Hundhofte 3727 S. 126 Street Tukwila, WA 98168 April 26, 2005 RECEIVED rA ?R 2 7 2005 D.EVELOPMENT 9505 - 19th Avenue SE Suite 106 Everett, Washington 98208 (425) 337 - 3174 Fax (425) 337 -3045 INTRODUCTION Wetland Resources, Inc. was contracted by Mr. Aaron Hundhofte to identify and delineate jurisdictional wetlands for the approximate one -acre site located at 3725 S. 126"' Street in the city of Tukwila, Washington. The property is further located as a portion of Section 10, Township 23N, Range 4E, W.M. Access to the site is via S. 126 Street along the northern property boundary. The on -site fieldwork was conducted on February 22, 2005. Anticipated development will include construction of one single- family home. The Washington State Department of Ecology Wetlands Identification and Delineation Manual, 1997, was used to identify and define wetland conditions. The City of Tukwila Municipal Code (TMC) Chapter 18.45 was used to classify wetland and stream systems. The study area is comprised of three existing legal lots, each rectangular with a long north -south axis. Topography on the site is comprised of an east aspect slope. Surrounding land uses are comprised of a combination of commercial development and single- family residences. The majority of the site has been historically cleared. The property currently contains an existing gravel driveway and two existing houses in the southern portion of the eastern lot. The southwestern portion of the site is currently comprised of a fenced maintained lawn. Vegetation within the remaining northern portion of the site is comprised of a combination of maintained grasses, red alder, Japanese knotweed, Himalayan blackberry, reed canarygrass, salmonberry, and willows. The property contains a Type 2 wetland and as Riverton Creek is located immediately off -si Type ,stream. The strea the east. Th known stream flows north, and eventually drains into the Duwamish River. It is classiffied as a Type 2 watercourse because it is smaller than a Type 1 stream and is used by salmonid fish. The on -site wetland is hydrologically connected to the off -site stream, and therefore meets the criteria for a Type 2 wetland. The on -site portion of the wetland has been historically disturbed. The outer western portion of the wetland is cleared, and dominated by maintained grasses. Vegetation within the eastern on -site portions of the wetland is dominated by invasive /non - native species with a red alder canopy. Pursuant to the City of Tukwila Municipal Code (TMC), Chapter 18.45.080, Type 2 wetlands typically receive 80 -foot buffers and Type 2 streams typically receive 100 - foot buffers. The existing use of the single- family homes and associated lawns are allowed, pursuant to TMC 18.45.070. Therefore, under this chapter the wetland buffer in the northern portion of the site would be regulated and would cover virtually the northern half of the site. This regulated buffer would therefore prohibit a reasonable economic use for the property. BRIEF CONCEPTUAL Burn MmcancN Puw 1 Am. 26, 2005 Hu+n►OFIE PRopern —S. 126 STREET WRI# 04176 CONCEPTUAL MITIGATION PLAN Pursuant to TMC 18.45.080, up to 50 percent buffer reduction is allowed if the applicant demonstrates that the existing buffer conditions are degraded and that increased wetland protection and buffer enhancement would be provided. This would result in a 40 foot buffer width along the wetland in the northern portion of the site. Despite this reduction, the outer part of the reduced buffer width would also include the existing location of the access driveway. Typical development standards would call for relocating the access driveway so that it is outside of the minimum wetland buffer area. Relocating the driveway would result in a variety of impacts on this site, however. The work would require extensive excavation along the slope in the western part of the site for creation of an appropriate road grade and associated side slopes. Exposed soils could increase potential for erosion and siltation into the adjacent wetland and stream areas. Additionally, a newly graded driveway with associated side slopes would require removal of several established trees along the western property boundary. The existing trees occur along the outer portion of the standard 80 -foot wetland buffer line. These trees offer very limited buffer functions, due to the heavily disturbed, unvegetated area between them and the wetland boundary. However, this stand of trees provides an excellent visual barrier between the subject property and the adjacent property to the west, as well as potential habitat for avian species. Based on the existing conditions of this site, it is our opinion that construction of a new access driveway outside of the minimum wetland buffer line would result in severe on -site impacts, and an unnecessary expense and hardship for the applicant. In lieu of the standard buffer reduction and relocation of the driveway, the applicant would like to propose an alternative development plan. The proposed alternative plan would call for retaining and improving the existing access driveway, while improving the functions and values of the on -site wetland and buffer areas. Proposed driveway improvements would include a slight widening (approximately 2 feet) along the eastern side, and then conversion of the existing gravel road to permeable concrete material. The intention of retaining and improving the existing access driveway is to reduce the amount of impacts on this site to the greatest extent possible. The resulting wetland buffer widths would be a minimum of 22.5 feet and a maximum of 65 feet. As mitigation for reducing the buffer line to below 50 percent of the standard buffer width, a full wetland and buffer enhancement plan would be implemented on this site. This activity is the minimum necessary to allow a reasonable use for the property. It is allowed pursuant to Reasonable Use Exceptions, TMC Chapter 18.45.180 because it would result in fewer adverse impacts to adjacent sensitive areas and buffers and it would not threaten public health, safety or welfare. BRIEF CONCEPTUAL BUFFER MITIGATION PLAN HuNdarrE PROPERTY-S. 126 STRE r • B 2 APRIL 26, 2005 WRI# 04176 • 0 Plans for wetland and buffer enhancement would include removal of invasive /non- native species and then planting the designated areas to a diversity of native trees and shrubs. Suggested buffer enhancement plantings would include Douglas fir (Pseudotsuga menziesii), big leaf maple (Acer macrphyllum), vine maple (Acer circinatum), Nootka rose (Rosa nutkana), thimbleberry (Rubus parviflorus), and snowberry (Symphoricarpos albus). Suggested wetland enhancement plantings would include western red cedar (Thuja plicata), Sitka spruce (Picea sitchensis), pacific willow (Salix sitchensis), black twinberry (Lonicera involicrata), and salmonberry (Rubus spectabilis). ANALYSIS OF EXISTING FUNCTIONS AND VALUES The methodology for this biological functions assessment is based on professional opinion developed through past field analyses and interpretations. This assessment pertains specifically to the on -site wetland buffers. Generally, vegetation on this site has been highly impacted by historic land use. The outer western portion of the wetland is cleared, and dominated by maintained grasses. Vegetation within the eastern on -site portions of the wetland is dominated by invasive /non- native species with a red alder canopy. The buffer associated with the on -site wetland is comprised of an existing gravel driveway and maintained grasses. Hydrologic Control Hydrologic control (flood control and water supply) is a very important function provided by wetlands and buffers. Due to their depressional characteristics, wetlands effectively function as natural water storage areas during periods of high precipitation, and are able to accumulate stormwater runoff. Wetlands with limited outlets store greater amounts of water than wetlands with unrestricted flow outlets. Forested areas retain much of the stormwater and help prevent soil erosion through hydrologic flows. The vegetation in the wetland stores any excess stormwater that reaches the wetlands. Conifer forested wetlands and buffers have potential to retain more stormwater and help prevent soil erosion to a greater degree than immature deciduous forests or scrub shrub areas. Areas dominated by invasive species are less effective for the function of hydrologic control. Water Quality Improvements Water quality improvement is another evaluated function. Surface runoff during periods of precipitation increases the potential for sediments and pollutants to enter surface water. Wetlands improve water quality by acting as filters as water passes through them, trapping sediments and pollutants from surface water. Ponded areas within depressional wetlands also allow sediments to drop out of suspension, thereby increasing water quality. As development increases, the potential for polluted water to reach wetlands and streams also increases. Vegetated buffers helps to slow overland flows and allows sediment to settle before entering the watercourse. Conifer forests with a layering canopy of native trees, BRIEF CONCEPTUAL BUFFER MmGATION PLAN HuNDNOFiE PROPERTY -S. 126"' STREET 3 APRIL 26, 2005 WRI# 04176 • • shrubs and forbs provide the highest potential for this function. Unnaturally high inputs of pollutants, which are often found in urbanized areas, along with the size of the wetlands and the vegetation structure within them are the main limiting factors of this function. Wildlife Habitat Wetlands have potential to provide diverse habitat for aquatic, terrestrial, and avian species for nesting, rearing, resting, cover, and foraging. Wetland buffers with multi canopy environments have potential to provide resources such as food, water, thermal cover, and hiding cover in close proximity, which wildlife species need to thrive. Wildlife species are commonly dependent upon a variety of intermingled habitat types, including wetlands, adjacent uplands, large bodies of water, and movement corridors between them. Vertical habitat diversity provides greater potential wildlife function than single canopy environments. Species diversity in a similar manner provides greater potential wildlife function than homogeneous plant communities. In addition, stream systems and their associated buffers allow for movement corridors, which become increasingly important as areas become developed. Human intrusion, including development within and adjacent to wetlands, and impacts to movement corridors are the most limiting factors for wildlife habitat functions. Analysis The subject wetland is a riparian wetland connected through surface flow to Riverton Creek. This wetland has moderately low potential to serve important functions to the surrounding environment such as hydrologic control, water quality improvement, and low flow recharge. Limiting factors to greater function and value of this wetland are associated with the lack of a viable buffer, historic human disturbance, and dense understory of invasive species. Being surrounded by dense urbanization has contributed to the limited wildlife habitat potential on this site. Based on these conditions this wetland provides moderately low function and value in the critical area landscape. Planting a diversity of native trees and shrubs would greatly improve the functions of this wetland over time. The on -site wetland buffer currently has a very low potential for providing typical buffer function. Its lack of a tree or shrub canopy represents the limiting factors for this function. Planting a diversity of native trees and shrubs would greatly improve functions of this buffer over time. BRIEF CONCEPTUAL BUFFER MmGATION PUN • HUNOHOFTE PROPERTY -S. 126"' SIPEEF 4 ARR. 26, 2005 WRI# 04176 POST - CONSTRUCTION FUNCTIONS AND VALUES This development plan would result in significant improvements of functions of previously degraded wetland and buffer. The overall mitigation concept is to increase native species density and diversity on this site. Over time, the newly planted species will provide a mixed forest of both deciduous and conifer trees and a dense understory of native scrub -shrub species. The enhanced wetland and buffer areas will provide additional hydrologic control, water quality benefits, and a dense vegetative barrier between the new development and the on -site wetland. Therefore, through proper implementation of the proposed enhancement plan, the intentions to sufficiently replace and improve the functions and values offered by this site shall be achieved. USE OF THIS REPORT This Brief Conceptual Mitigation Plan is supplied to Mr. Aaron Hundhofte as a means of determining on -site sensitive area conditions. This report is based largely on readily observable conditions and, to a lesser extent, on readily ascertainable conditions. No attempt has been made to determine hidden or concealed conditions. Reports may be adversely affected due to the physical condition of the site and the difficulty of access, which may lead to observation or probing difficulties. The laws applicable to wetlands are subject to varying interpretations and may be changed at any time by the courts or legislative bodies. This report is intended to provide information deemed relevant in the applicants attempt to comply with the laws now in effect. The work for this report h as conformed to the standard of care employed by wetland ecologists. No other representation or warranty is made concerning the work or this report and any implied representation or warranty is disclaimed. If you should need any further information regarding the sensitive areas and buffers on this property, please contact our office at (425) 337 -3174. Wetland Resources, Inc. Andrea Bachman Senior Wetland Ecologist BRIEF CONCEPTUAL BUFFER MmGAT70N PUN HUNDHOffE PROPERTY-S. 126" STRUT • • 5 APRU.26, 2005 WRI# 04176 SCALE: 1" = 40' 0 40 i T i 80 PLEASE NOTE: THE STREAM LOCATION DEPICTED ON THIS MAP IS APPROXIMATE, AND DOES NOT REPRESENT AN ACTUAL STREAM SURVEY. APPROXIMATE STREAM LOCATION WAS BASED ON AERIAL PHOTOGRAPHY. LEGEND WETLAND EXISTING GRAVEL • CONCEPTUAL WETLAND MITIGATION PLAN MA, HUNDHOFTE PROPERTY - S 126TH STREET Section 10, Township 23 North, Range 4 East, W.M. EXISTING LAWN 140 126th St. PROPOSED BUFFER LINE • BUFFER ENHANCEMENT . -4.300 SF PROPOSED BUFFER LINE 1 �� A -4 EXIST, LAWN: \: • A5 -- --- - - ---- -- WE D _ — ENH ENT— .1.7.100SF,. ,,. . i. i o '• EX. HOUSE EX. HOUSE ea nein* Wall "'k — 'l` — �` — • — ,1, 1 z2>_ ' CX 96- - — . II YARD ,�ARDX • \i• I —.1.,_ _,lc_ j o —e—r e— � E ,, C1'-- r� T T T T T T T I CONCEPTUAL WETLAND MITIGATION PLAN MAP HUNDHOFTE PROPERTY - S. 126TH ST. City of Tukwila, Washington Mr. Aaron Hund,ofte 3727 S. 126th St. Tukwila, WA 98168 Sheet 1/1 Job 605041 Drawn by A Bachman Date: A4i1126, 2025 950519th Avee,e S.[. Site 106 Everett,WeYm5tm 90700 Phone (425) 337.3174 Fax (425) 337 -3045 E-mail: mallboxelwetlandresources.com r Home 00 0 About WACA S WASHINGTON AGGREGATES & CONCRETE ASSOCIATION Pervious Pavement Consumer Info Industry Info Salmon Listing Requires New Stormwater Management Strategy O By BRUCE T. CHATTIN With the recent listing of Puget Sound Chinook and the uncertainty of what the new ground rules will be, one thing is for certain - things will change and the use of impervious surfaces and the current methods to manage stormwater appear to be themselves endangered. This was the clear message of the Governor's task force report, "Extinction is Not an Option," published in late 1998. The undesirable effects and harm caused by stormwater runoff and lack of infiltration of impervious surfaces is harmful to fish, water quality and habitat. Traditional hard paving methods will need to be reviewed. Since March of 1994, the ready mixed concrete industry locally and nationally has renewed its interest in the very old technology of "no fines" concrete. Also known as K- Crete, EnviroCrete, EcoCrete and pervious /porous pavement - this pavement surface traditionally reserved for greenhouses, soil stabilization, erosion control and subgrade drainage, appears to be a bona fide solution for current surface stormwater management needs. The Washington State Aggregates and Concrete Association constructed test panels in 1994 to evaluate the use of "no fines" pavement potential in Western Washington, and evaluated how such as material could be used commercially. Testing included evaluation of the acceptable Florida models and construction methods. While, this isn't Florida, the concept transfers well to the Northwest where temperatures and freeze -thaw cycles are nominal and stormwater management concerns are equally as acute. With the recent attention towards salmon, habitat and stormwater management, the association and its local members have been preparing the product for more widespread use. 1.44... ....... .... .....L ,,.4 ...... �.�. ...� /:.. �,...�.., /a.......,� ...,..a...os ..1.4...1 Links Members Area WACA Contact Info ADDRESS: 22223 7th Des Moines, WA 98198 PHONE: 206 - 878 -162; FAX: 206 - 878 -6282 Email: admin @washingtoncon A /)7/'nnc • "No fines" concrete quickly soaks up liquid. "No fines" concrete is exactly what it seems. The use of cement, coarse aggregates and water to provide sufficient paste and bonding ability to glue the coarse aggregates together in a structural pavement that essentially "drinks" liquid. Water filters through the pavement to a secondary drainage /filter layer in the ground. This allows for natural recharge of groundwater much like the natural filtering effects desired in bioswales. The pavement also eliminates untreated stormwater from leaving the site. An improved and more successful stormwater management strategy is not to collect and then dispose of runoff, but to address stormwater much earlier in the development process and not generate any runoff. The future focus for public works and planning departments will move rapidly towards zero runoff. According to the concrete industry, the potential benefits for the use of "no fines" concrete fits well with the direction public works departments and developers are considering to meet the new standards for stormwater management. The immediate benefits of using "no fines" concrete result in no water leaving the site, eliminates the need for stormwater collection and detention systems, and increases the pervious to impervious ration ratio of a property. The multiple layer pavement and drainage system will naturally provide water retention and will essentially mimic the drainage and filtration action of naturally unpaved surfaces. Tests conducted indicate the use of 5/8 -inch crushed material is desirable, as the use of any smaller aggregates produces a strain on already marginal supplies of 3/8 -inch pea gravel. One of the considerations for a viable porous pavement is not to strain existing aggregate products by using or creating specialty blends of aggregates. 0 htt'r / /www wachinotnnennerete nra/inrinctry /nervirmc navement chtml a/17/1nns Permeability tests conducted with 5/8 -inch aggregates indicate more than sufficient drainable capacity in a well graded 5/8 -inch aggregate mix with approximately 20 percent voids for anticipated precipitation in 24 -hour, and 10- and 25 -year storm events received in the Northwest. Recent testing is evaluating the use of recycled aggregates for secondary drainage /filter sections and other filtering options. The concrete industry has been initially reluctant to push the pavement into the market because of the special considerations in its manufacture and equally important construction. Manufacture of the mix design places new considerations in batching, discharge and aggregate gradations. Placement and curing of the pavement requires expertise and few local contractors have the experience to place the new material. This can be overcome with proper instruction and a commitment to quality. The concrete association and local members are working on a specification and recommended guidelines to provide specifiers direction and clear construction practices to insure successful applications. Concrete industry quality control personnel and contractors are working on a complete "system" that will allow for maximum stormwater management and many new applications. The potential for "no fines" concrete applications are seen in parking lots, driveways, sidewalks and low -speed residential - volume roads or any situation where drainage review is required and /or near -zero runoff is desirable. Industry representatives are considering design practices on use of the material for whole site pavement management and for perimeter or edge drainage for parking lots and road shoulders. "No fines" or "Portland cement pervious pavement" is acknowledged and suggested as a best management practice in the Puget Sound Stormwater Management Manual (February 1992), Chapter III -3 -63. Bruce Chattin is the executive director of the Washington Aggregates and Concrete Association. He can be reached at (206) 878-1622 or by htin• / /uninhr rvaehirnCrtnnnnn•rofP nrrr/iniliictry /TPrclini a navPniPnt chtml A/17 17(1(15 Home; .'. r WASHINGTON AGGREGATES & CONCRETE ASSOCIATION About!:WACA' Pervious Pavement • Imagine this ... No Storm Water runoff Pervious Concrete Pavement allows storm water to pass directly through your concrete pavement. This allows water to infiltrate naturally, recharging local watershed systems, and replenishing ground water supplies while protecting salmon habitat. Pervious Concrete provides an excellent alternative to expensive storm water collection and detention systems with the strength and performance of conventional concrete paving. onsumer; Info AN ALTERNATIVE STRATEGY ... FOR CREATING, CAPTURING, TREATING, AND DISCHARGING STORM WATER What is Pervious Concrete? `, Industry Info Links Mem Area Industry Information PERVIOUS AR1 :.'Salmon Listing Require ;Storm water ManagemE By BRUCE 'ZBruce Chattin is the Ex Director of the WACA. reached at (206) 878 -: {e -mai . :3. DOWNLOAE Pervious Concrete Broc i Vavailable to download A 11P)Anc Traditionally reserved for greenhouses and erosion control, Pervious Concrete is a concrete pavement consisting of cement, coarse aggregates, water, and other specialty components to produce sufficient paste and bonding ability to glue coarse aggregates together. This creates an in -place void structure of approximately 14 to 18 %. Essentially, Pervious Concrete is a structural concrete pavement that "drinks" water. • Eliminates untreated storm water and creates zero runoff • Directly recharges groundwater • Mitigates first flush pollution • Protects streams, watersheds, and ecosystems. • Mimics the drainage and filtration of bioswales and natural soils • Reduces surface temperatures & heat island effects • Provides a higher albedo surface reflectivity index (0.35 or higher) • Eliminates need for expensive collection and detention systems Designing with Pervious Concrete Pervious Concrete may be used for: sidewalks, trails, residential driveways, residential streets, general parking areas or areas where storm water management is an issue. Generally, Pervious Concrete Pavement depths can range from 4 inches for sidewalks and trails, 5 -6 inches for residential driveways and parking lots, and 8 -10 inches for heavier truck traffic areas. Depending on the usage, consult: ACI 330 - "Guide for Design & Construction of Concrete Parking Lots ". • Why is Pervious Concrete a Sustainable Solution? Design of the Retention / Recharge Layer & Subgrade top of page top of page Pervious Concrete is a 2 part on site storm water management system consisting of the concrete pavement and a coarse gravel retention layer for storm water storage. Design of the retention / recharge area is a site specific task and should take into account, percability and characteristics of native soils, volume of storm water anticipated, rate 1.0+.,•/Aaninv v7oel,inrrtnnrnnrratP nrn/inrlrnctry /nPrvinnc /r .rviroic navPmPnt chtml d /,,7 / -,(HK • of flow, and duration. An initial soils site survey, and site specific storm water calculations should be performed by a storm water management engineer. What About Freeze / Thaw? Pervious Concrete is not designed nor intended as a storage area. Water passes directly through the pavement and into the retention layer below. Freeze/Thaw is not a concern in western Washington as our temperatures and freeze / thaw conditions are nominal. What About Clogging? Clogging of any pervious surface can be a concern. It is highly unlikely a majority of any pervious surface will become 100% clogged. Water will always seek the next point of infiltration. What About Maintenance? • Good common sense approaches to prevent placement of landscape ' materials and cleaning of any pervious surface are recommended practices. For parking areas, your regular parking lot sweeping / vacuuming program should be sufficient. PERVIOUS CONCRETE WORKS WITH THE ENVIRONMENT » Salmon, F..riendly » eliminate °IZun:Off ' w.i, » Di ;ect Rechargeto Ground » Mlrnics°Natura'IIn top of page To learn more about Pervious Concrete Pavement or other concrete and aggregate needs, please contact your local ready mix supplier. top of page l J A /11/7AA From: Nora Gierloff To: Carol Lumb Date: 3/22/05 11:49AM Subject: SAO Question Hi Carol, I received a call from a property owner at 3725 126th (East Marginal), lots 5 -6 -7, LDR zoning. He would like to set up a time to meet and discuss his options on how to work around the wetland and stream buffers on his property. Please give him call to set up a time. Aaron Hundtofte (206)850 -5535 Thanks, Nora LAAA-A dAigio 6 11 7 14 1 t 0 d C LA- A - 5f e 3 Hundhofte /Campbell Wetland Mitigation Enhancemet Project • Technical Assistance Packet Prepared by Amy Tippery Ptsoject Specialist 0/2006 KaD RECEIVED • MAY 15 2006 DOMUNDY DEVELOPMENT • • Hundhofte /Campbell Wetland Buffer Enhancement Technical Assistance Packet Table of Contents Section 1 - Overview • Project Summary • Species Recommended for the Hundhofte /Cambell Wetland Planting • Estimated Cost Sheet, Planting Areas 1- 4 • Site Map Section 2 — Restoring Streams and Wetlands • Streamside Planting Guide for Western Washington Landowners (Harza Engineering and Cowlitz Conservation District) • Stream and Wetland Buffers, Planning and Planting a Buffer Enhancement Project (The King Conservation District, Buffer Class exercise #2) Section 3 — Wildlife Habitat Enhancement • Landscape Design for Wildlife (Dept. of Fish and Wildlife, 1997) • Mason Bees, Fact Sheet (Knox Cellers, 2002) • Butterflies and How to Attract Them (Dept. of Fish and Wildlife, 2000) • Birds in the City and Suburbs (Dept. of Fish and Wildlife) • Nest Boxes for Birds (Dept. of Fish and Wildlife, 2000) • Attract Reptiles and Amphibians to your yard (OSU Extension Service) • Hedgerows, Living Fences for Western WA (King Conservation District) Section 4 — Native Plant Sources • Native Plant Nursery List (King Conservation District, 2003) • Restoration Growers Association Brochure and Order Form (King Conservation District, 2003) • Sample Bareroot Tree and Shrub Sale Flyer and Order Form (King Conservation District, 1999) • Wetland Plant Cooperative Brochure (King Conservation District, 2000) • • Section 5 — Site Preparation, the Technical Toolkit • KCD Information Sheet: Site Preparation • KCD Information Sheet: Sheet Mulch • Selected Noxious Weeds of King County (Washington State Noxious Weed Board) • Brochure: Removing Blackberry through Integrated Pest Management (Thorton Creek Alliance) • Nonchemical Methods for Removing Unwanted Blackberry Plants (Caroline Cox, Journal of Pesticide Reform, Spring 2003, Vol.23, No. 1) • Controlling Knotweed (Polygunom cuspidatum Sieb.& Zucc.) (Ron P. Crockett, PhD Technical Development, Monsanto County, Vancouver WA) • KCD Information Sheet: Reed Canary Grass Section 6 — Installing a Planting Plan • ISA Brochure: New Tree Planting • KCD Information Sheet: Planting Containerized Plants (King Conservation District) • KCD Fact Sheet: Planting Live Hardwood Stakes (King Conservation District) • KCD Information Sheet: Erosion Control Seed Mixes (King Conservation District) • KCD Fact Sheet: Planting Bare root Trees (King Conservation District) District) • KCD Information Sheet: Seedling and Sapling Protection (King Conservation District) • Treesentials Protective Products (Treesentials Company) Section 7 — Maintenance and Monitoring • KCD Information Sheet: Restoration Project Maintenance (King Conservation District) • KCD Information Sheet: Monitoring Plant Survival (King Conservation District) Section 1- Overview • Project Summary • Species Recommended for the Hundhofte /Campbell Wetland Planting • Project Photo Album • • Project Summary The purpose of this packet is to provide the knowledge and planning tools necessary to carry out the Hundhofle-Campbell wetland buffer enhancement project as mandated by the City of Tukwila Department of Community Planning. While planning a development on their property, Aaron and Brie found that they were within the buffer of Riverton Creek, a type 2 stream, and its associated wetland. Due to the City's land use regulations, the project could only be carried out with a buffer reduction and reasonable use exception from the City of Tukwila. To compensate for the impact of the development and an existing driveway, some form of mitigate is required wetland delineation and brief conceptual mitigation plan were created for them by Wetland Resources Inc, a private contractor, and will be implemented to satisfy the mitigation requirements of the City. In order to best carry out the mitigation plan, the couple has sought technical advice and expertise from the King Conservation District. The KCD collaborates with property owners to help them implement restoration and enhancement of stream and wetland resources. In their efforts to improve the buffer between the driveway and Riverton Creek KCD will assist Aaron and Brie with step -by -step resources and strategies to get the job done. This plan will detail their role as stewards of the planting project and introduce tools and techniques that will be useful in making their efforts prosperous. Theplan includes planting procedures, native plant resources, maintenance techniques, and wildlife enhancement measures. Given the magnitude of their enhancement objectives, this TA packet is also meant to be a helpful timeline to prioritize tasks and set reasonable goals for project completion. Management Recommendations The recommendations included in this Technical Assistance Packet focus on enhancing the Hundhofte - Campbell property wetland buffer and wetland areas. Activities to be completed include the following: 1. Control Invasive Plants and Remove Garbage from Wetland and Buffer Areas 2. Install Native Plants in the Buffer Enhancement Area 3. Install Native Plants in the Wetland Area 4. Create Habitat Structures for Wildlife. 5. Stewardship and Maintenance of planted areas Control Invasive Plants and Remove Garbage from Wetland and Buffer Areas Possibly the most important step for project success, the planting site must be prepared to give incoming plants a competitive edge. Weed removal is key in this process. Non- native, aggressive plants can form extensive monocultures that severely limit diversity of habitat. Currently, the list of invasive weeds includes Japanese Knotweed, Reed Canary Page 1 of 6 • • Grass, and Himalayan Blackberry. Each of these weeds is capable of overtaking a newly planted section of native plants, and must be controlled and eventually exterminated from the site if plant diversity is ever to be established. This is especially true in the primary wetland area, which has a modest infestation of Japanese Knotweed (Polygonum cuspidatum). Only a licensed herbicide applicator may recommend the use of chemical control of weeds, and the King Conservation District's aim in this technical assistance packet is to present a suite of available tools to be used in the control of noxious weeds. If chemical control of this class "C" weed is employed, a native planting must wait until all herbicide treatment cycles are complete. The wetland area must also be prepared to plant by controlling Reed Canary grass through large -scale shading with cardboard or landscape fabric. Lastly, Himalayan Blackberry must be extirpated from the site to lessen any competition for native plants. See section on Site Preparation for details. As invasive plants are removed from the landscape, other problematic species can become "released" as a new influx of light and nutrients are made available. Be on the lookout for other noxious species so they can be eradicated before becoming large -scale infestations. Install Native Plants Natives will be installed at a density called for in the mitigation plan or better, depending on type of plant material. The district recommends a tree density of 12 to 15 feet on center, a shrub density of 4 feet on center and the addition of an herbaceous and emergent plant layer (See Section 2, Stream and Wetland Buffers, Planning and Planting a Buffer Enhancement Project). Planting areas will be installed in phases for appropriate weed control timing and consideration of limited resources. All plants will be of appropriate northwest native genetic stock and from the same watershed association if possible. Buffer Enhancement Area This area will be installed first to act as a protective filter for the wetland and stream from the impacts of the driveway. Wetland Area This area will be planted after the Knotweed infestation has been controlled to prevent herbicide damage to native plantings. Create Habitat Structures for Wildlife Creating habitat structures is discussed extensively in Section 3 - Wildlife Habitat Enhancement. The addition of one or several habitat piles, either of rocks or woody debris, will add dimension and living space for many more species much in the same way as condominiums do for humans in high density living areas. Wood in the form of logs, stumps, and even fence posts (non- treated) is an important element for wildlife. Rotting logs and fallen branches provides shelter for many animals including beneficial insects, which in turn provide food for many species of wildlife. Snags are especially key as they decay over time and provide prime cavity nester material. It is recommended that large and small pieces of wood be left around the wetland area and even imported and placed both in and around the area. Page 2 of 6 • • Brush piles are made with the simple idea of creating cover for small animals. They are most effective in areas lacking cover in the form of ground debris, tall grass or shrubs. Brush piles typically harbor mammals, amphibians and reptiles, the only limit to use being the size of entrance holes and inner cavity size. For example, bunny sized holes and inner spaces will capacitate anything the size of a bunny to enter and use the inside space. Rock piles differ in the material used, which can be rocks of any size, pottery shards, concrete or pavement chunks, etc. The best places for rock piles will depend on what species you want to attract. Full or partial sunny areas will attract reptiles, which use the cooler inside of the pile during the day, and regulate their temperatures with the absorbed ambient heat from the rocks during cooler evenings. Amphibians are more likely to use rock piles located near a water source, as they need cool, moist refuge areas. :Stewardship and Maintenance of Planted Areas - As called for in the mitigation plan, monitoring shall be done for five years to assess survivorship of the plants. Stewardship shall include maintaining a weed free space around each plant, watering for the first two summers at a minimum, and protecting plants from damage by other animals or human impact. See section on Maintenance and Monitoring for details. Project Implementation Timeline The following is a proposed implementation timeline for the management recommendations listed above: ❑ Winter, 2006 — Site prep and install bareroot plantings in the Wetland Buffer Area with appropriate sheet mulching. • April- September 2006 — Water and weed around new plantings as needed. Do baseline monitoring for Wetland Buffer Area. ❑ Spring/Summer, 2006 — Control Reed Canary grass by laying cardboard or landscape fabric over the area to be planted in the fall. ❑ Summer, 2006 — Control weedy Himalayan Blackberries by hand. ❑ September- October, 2006 — Control Japanese Knotweed while it is translocating energy into the roots and before it senesces for the winter. ❑ Winter -early Spring 2007 — Plant Wetland Area, possibly reserving some areas still infested with noxious weeds to plant in the following year. ❑ Ongoing until 2011 — maintenance and monitoring. Plant Installation Instructions Planting Site: Planting shall take place on the Hundhofte /Campbell property, 3727 S. 126 St. Tukwila, WA 98168. Planting Date: Winter thru early Spring, 2006 and Winter thru early Spring, 2007. Other plantings will be installed in the same season according to replacement planting needs. Page 3 of 6 • • Species list and plant spacing: Refer to the table titled Species Recommended for the Hundhofte /Cambell Wetland Planting included in Section 1- Overview. Seedlin sapling care: Plant material will be native species adapted to the site to minimize maintenance and care. Plant material can be potted nursery stock or bare -root plants. All plant material will be well watered prior to planting and stored in a cool location. In the case of ban root plants, plants will be stored in a refrigerated facility prior to installation. Bare root plants be stored in the field for up to one week prior to planting by placing them in a shaded location and covering them with a tarp. Such a location should prevent freezing, exposure to warm temperatures, and drying of roots. Site Preparation Weed control methods for the different types of invasive plants are briefly described here. For additional documents discussing these weeds see Section 5-Site Preparatic the Technical Toolkit. Reed Canary Grass is a problem weed on this site. Control of this weed is necessary prior to planting the site. To prepare the site for planting, control the Reed Canary Grass by covering t] planting area a geo- textile fabric, weed mat, or some other permeable but durable material Placing a covering will reduce the population of Reed Canary Grass by starving the individual plants. Prior to placing a covering on the ground, cut the grass back to ground level (1" — 3" in height). Overlap the covering 6 - 12 inches to minimize the amount of light reaching the grass. Leave the covering for one growing season before planting the site. An alternative control method involves heavily planting the site with willows or conifer tree species to establish shade on the site. The site is also currently vegetated with a weed called Himalayan Blackberry. Control of this weed is necessary prior to planting the site. To prepare the site for planting, mow or cut the blackberry canes to less than 1 foot in height, then grub /dig out the roots attached to the cut canes. Thorough removal of blackberry roots in this manner, while labor intensive can reduce the blackberry population in the prepared area by 90 — 95 %. An alternative control method involves cutting/mowing the canes and swabbing the freshly cut canes with an approved herbicide. The Wetland Area is also infested with Japanese Knotweed. Control of this weed is necessary prior to planting the site. Mechanical control by mowing, digging out rhizomes or shading has proven very laborious and can take years of intense effort. Chemical control has proven more effective, especially for large populations. Planting Method: Planting methods for the different types of nursery stock are described here and in additional documents included in the section titled Installing a Planting Plan. Bare root seedlings will be shovel planted to the same depth that they grew in the nursery. Roots will remain moist once they are removed from the shipping bundles until they are planted. Roots will be placed in a natural position in the ground without being crowded or turned up. Soil will be packed firmly around the root system, leaving no air pockets. Prior to digging a hole for the plant, prepare the planting location by removing all grass sod within a 1.5 foot diameter circle, Page 4 of 6 • • being careful to remove roots as well as above ground grass. Dig a hole for the bare root plant in the center of this cleared circle. Refer also to the fact sheet titled Planting Bare Root Trees and Shrubs. Live Stakes and whips will be planted using a planting bar. Stakes and whips are to be 3 to 4 feet long, and a minimum of %2 inch in diameter. Stakes will be soaked until planted, placed with buds facing up in a bucket of water. Soaking before planting greatly increases the survival of live stakes and whips. At least half of the length of the stake or whip will be below ground after planting. Refer also to the fact sheet titled Planting Live Hardwood Stakes. Potted plant material should be shovel planted to the same depth that they grew in the pot. Plants will be well watered prior to planting. Prior to digging a hole for the plant, prepare the planting location by removing a grass sod within a 1.5 feet diameter circle, being careful to remove roots as well as above ground portions of the plant. Dig a hole for the container in the center of this cleared circle twice the size of the plant's pot. Backfill the hole, being careful to fill any air pockets in the soil. Refer also to the fact sheet titled Planting Containerized Trees and Shrubs. Basal Wrapping (for sites where vole /mice herbivory is excepted): Grass stands tend to harbor large populations of meadow mice that will girdle the planted seedlings and saplings. To protect plants from girdling by herbivores, wrap the base of each plant with aluminum foil, or with a manufactured basal wrapping material. The wrapping will begin just below the soil line and will extend up the trunk for 8 inches, or to the level of the first main lateral branch, whichever is less. When using aluminum foil as a basal wrapping material, secure it around the base of the trunk with filament- reinforced strapping tape or staples. Sheet Mulching Prepare the area around each plant for mulching by placing a barrier of newspaper, cardboard, or commercial weed mat product around the plant. Newspaper or cardboard should be applied to a thickness of 1 /4 inch. Apply commercial weed mat products to the manufacturer's specification. After placing a barrier, apply a layer of mulch at a depth of 4 -6 inches over the weed barrier. Mulching materials can include wood chips, fully composted organic material such as a commercial compost product, or weed free straw. Mulch shall be weed free, if possible, to avoid introducing new weeds to the project site. Sheet mulch is an important part of the stewardship process. A large amount of mulch has already been applied to some of the planting areas and will greatly aid in the breakdown and availability of nutrients in the soil. Mulch in the form of shredded wood chips, leaves, and bark adds exactly what is needed to encourage a typical array of nutrients and microorganisms needed by northwest native plants. In the Pacific Northwest, forest soils are rocky and contain relatively few nutrients. Forest productivity is often limited by lack of nutrients or water. Despite the lack of resources, the fungal flora of the Pacific Northwest is extremely diverse. Fungi are neither plants nor animals but are recognized as a separate kingdom of organisms both in structure and function. The large number of fungi in late - successional and old - growth forests, especially those of uneven -aged structure, reflects the complexity of these ecosystems. Estimates indicate there are at least six species of fungi for every vascular plant species in a given temperate ecosystem. Page 5 of 6 Much of this is due to woody debris and detritus on the forest floor that hosts different types of fungi. Saprophic fungi are a major component of all forest ecosystems, growing on a variety of substrates (e.g., recently fallen trees to well- decayed logs, litter, dung, and other fungi). They play an important role in decomposition and recycling of nutrients. Saprobes release nutrients bound in dead plant, fungus, and animal tissues that later become incorporated into the soil. Refer also to the fact sheet titled Sheet Mulching in Section 5 of this packet. Temporary Erosion Control: In the event that unplanted areas in and around the planted buffer are disturbed during the plant installation process, control soil erosion by seeding these areas with an erosion control seed mix. The District recommends use of a sterile wheat product called ® Regreen. ® Regreen is a commercial brand of sterile wheat that will form a cover crop and die back within approximately one year to three years. ® Regreen shall be applied a rate of 60 lbs per acre when hydro seeded, and 120 lbs per acre when broadcast seeded. Maintenance: Water planted trees, shrubs and herbs for a minimum of 2 summers following planting. However, the District recommends watering 3 consecutive summers for optimal survival. Because young bare root, container, and ball/burlap plants have a greatly reduced root system, they have a limited ability to survive during the dry months (July through October). Watering a minimum of once every two weeks during the dry summer months will ensure greater odds for survival. Watering once per week is preferable. Weed the cleared areas around each plant for a minimum of one summer. This cleared area will provide a competition free zone for the newly planted seedlings. However, the District recommends weeding for 3 consecutive summers so that the planted trees and shrubs can become tall enough to compete with the grass (usually a height of 4 -5 feet in most cases). Control grass and weed height in and around the planted trees and shrubs by hand cutting or using a weed mower. Grass mowing and weeding should take place a minimum of 2 times per summer, once in mid June and again at the end of the growing season. Care should be taken when using a weed mower to avoid damaging or killing planted trees and shrubs. For more information, refer to Section 7- Maintenance and Monitoring. Page 6 of 6 * ** *Amendments made 11/2006 see pages 3 -4 Size of Plant Number of Plants Common Name (Scientific Name) Site Requirements I Plant Spacing Recommended 2 Recommended Needed by Species Materials Source 3 Notes Species Recommended for Wetland Buffer Area * ** *Wetland Buffer Area: This zone is characterized by fill soils and low slopes of varying steepness of which boarder the stream and associated seasonally innundated areas. The buffer is dominated by turf grasses and has already been planted with salvaged conifers, ferns, and a recent native bare root installation. Its nutrient poor, well drained soils at the top of the slope are partially shaded by mature decidious trees and the richer, more frequently saturated native soils are mostly shaded by the adjoining wetland's decidious trees. Native plant species currently present on the site suggest a Red alder /Salmonberry plant association for the wet benches along the stream and wetland, and a Douglas Fir /Sword fern plant association for the upland slope. Some dry fringe and groundcover plants should be installed as highlights after all construction is finished to aviod impact. This zone occupies approximately 4,000 square feet. Trees Douglas fir (Pseudotsuga menziesiz) Big Leaf Maple (4cer macrophyllum) Cascara (Rhamnus purshiana) Sub - Trees/Multi- Stemmed Trees/Tall Shrubs Vine Maple (4cer circinatum) Mock Orange (Phyladelphus lewisii) Shrubs Salal (Gaultheria shallon) Low Oregon Grape (llahonia nervosa) Indian plum (Oemleria cerasiformis) Red Flowering Current Vibes sanguineum) Nootka Rose (Rosa nutkana) Thimbleberry Qiubus parvora) Snowberry (Symphoricarpos albus) Groundcover Fringecup (Telima grandiflorc) Kinnikinnick (Arctostaphylos uva -ursi) Woodland Strawberry (Fragaria vesca) Ferns Sword Fern (Polystichum munitum) Lady Fern (4thyrium felix femina) Species Recommended for the Hundtofte /Cambell Wetland Planting Moist/dry, full sun Moist, part shade/full sun Moist, part shade /full sun Moist, part shade /part sun Dry/Moist, part shade /part sun Dry/Moist, shade /part sun Dry/Moist, shade /part sun Moist, shade /part sun Dry/Moist, part shade /full sun Moist/dry, full sun Moist, full sun, some shade Moist/dry, part shade /full sun Dry/Moist, full sun/part shade Dry, full sun/part shade Dry/Moist, part sun/full shade Moist/Dry, full shade /part sun Wet/moist, full shade /part sun 1 gal;12' -20' bareroot; 10L12' 1 gal;12' -20' bareroot; 10L12' 1 gal; 8'42' bareroot;8' -I2' 1 gal; 8' bareroot; 6' 1 gal; 8' bareroot; 6' 1 gal;4' -6' bareroot;3' 1 gal; 2'4' bareroot; 2' 1 gal;4' -6' bareroot;3' 1 gal;4' -6' bareroot;3' 1 gal;4' -6' bareroot;3' 1 gal;4' -6' bareroot;3' 1 gal;4' -6' bareroot;3' 6 " -12" 6 " -12" 6 " -12" 4' 4' bareroot bareroot bareroot bareroot bareroot 1 gallon 1 gallon bareroot bareroot bareroot bareroot bareroot 4" pots 4" pots 4" pots 1 gallon 1 gallon 15 Bareroot Sale 15 Bareroot Sale Bareroot Sale 30 Bareroot Sale 3 Bareroot Sale for dry fringe 10 Bareroot Sale for dry fringe 10 Bareroot Sale for dry fringe 50 Bareroot Sale 3 Bareroot Sale for dry fringe 100 Bareroot Sale 40 WPC 60 Bareroot Sale 10 other 20 WPC 20 WPC 10 WPC 5 other 401 PF = species requires permanently flooded conditions, SF = species requires seasonally flooded conditions, PS = species requires permanently saturated conditions, SS = species requires seasonally saturated conditions 2 The recommended spacing intervals highlighted in bold are the preferred spacing interval for this site in its present condition. 3 WPC: The King Conservation District's Wetland Plant Cooperative Nursery, Bareroot Sale: The King Conservation District's Annual Bareroot Sale, Other: Local native plante nurseries. sub for Big Maple • Common Name (Scientific Name) Species Recommended for Wetland Area * ** *Wetland Area: This area is characterized by saturated soils with onsite, weedy wetland vegetation. Habitat potential is great considering the wetland's non - isolated charactor and direct connection to Riverton Creek. The likely historical lowland plant association of Red alder /Salmonberry /Redcedar is a good target for restoration of the site. Low streamside benches also suggest natural enclaves of Small fruited Bullrush, Slough Sedge and Skunkcabbage. This zone occupies approximately 7, 500square feet. Trees Western Red Cedar (Thuja plicata) Red Alder (4lnus rubra) Sitka Spruce (Picea sitchensis) Sub - Trees/Multi- Stemmed Trees/Tall Shrubs Pacific willow (Salix lasiandra) Sitka Willow (Salix sitchensis) Shrubs Black Twinberry (lonicera involucrata) Salmonberry (Rubus spectabilis) Red Osier Dogwood Fornus sericea) Emergents Slough Sedge (Carex obnupta) Small fruited Bullrush ¢cirpus microcarpus) Skunkcabbage (Lysichitum americanum) Ferns Sword Fern (Polystichum munitum) Lady Fern (4thyrium felix femina) Site Requirements Wet/moist, full shade /part sun Moist, part shade /full sun Wet/moist, part shade /full sun Wet, full sun Moist/Wet, part shade/full sun Wet/moist, part shade /part sun Wet/moist, part shade /part sun Wet/moist, part shade/full sun SF/PS, part shade /full sun, emergent zone SF /SS, part shade /full sun, wet meadow /forested wetland PS full shade /part sun, wet river /pond/lake margin, forested wetland. Moist, full shade /part sun Wet/moist, full shade /part sun Size of Plant Plant Spacing Recommended 2 Recommended 1 gal;12' -20' bareroot; 10L 12' 1 gal;12' -20' bareroot; 10L12' 1 gal;12' -20' bareroot; 10L 12' 1 gal; 3' -4' cuttings; 2' 1 gal; 3' -4' cuttings; 2' I gal; 4' -6', bareroot; 3L4' I gal; 4' -6', bareroot; 3L4' 1 gal; 3'4' cuttings; 2' 1 gal; 2', plugs; 6"42" I gal; 2', plugs; 6"42" 2' 4' 4' Number of Plants Needed by Species bareroot 30 Bareroot Sale bareroot 12 WPC bareroot 10 Bareroot Sale bareroot/ cuttings 50 Bareroot Sale bareroot/ cuttings 150 Bareroot Sale bareroot 100 Bareroot Sale bareroot 200 Bareroot Sale bareroot 200 Bareroot Sale I gallon 20 WPC 1 gallon 20 WPC 1 gallon 15 WPC 1 gallon 15 WPC 1 gallon 10 other 832 PF = species requires permanently flooded conditions, SF = species requires seasonally flooded conditions, PS = species requires permanently saturated conditions, SS = species requires seasonally saturated conditions 2 The recommended spacing intervals highlighted in bold are the preferred spacing interval for this site in its present condition. 3 WPC: The King Conservation District's Wetland Plant Cooperative Nursery, Bareroot Sale: The King Conservation District's Annual Bareroot Sale, Other: Local native plante nurseries. must special order must special order must special order not ready untill 2007( ?) Common Name (Scientific Name) Site Requirements I Species Recommended for Wetland Buffer Area Size of Plant Number of Plants Plant Spacing Recommended 2 Recommended Needed by Species Materials Source 3 Notes Wetland Buffer Area: This zone is characterized by fill soils and low slopes of varying steepness of which boarder the stream and associated seasonally innundated areas. The buffer is dominated by turf grasses and has already been planted with salvaged conifers, ferns, and a recent native bare root installation. Its nutrient poor, well drained soils at the top of the slope are partially shaded by mature decidious trees and the richer, more frequently saturated native soils are mostly shaded by the adjoining wetland's decidious trees. Native plant species currently present on the site suggest a Douglas Fir /Sword fern plant association for the upland slope. Groundcovers can be installed as highlights after all construction is finished. This zone occupies approximately 4,000 square feet. Trees Douglas fir (Pseudotsuga menziesit) Moist/dry, full sun 1 gal;12' -20' bareroot; 10t12' bareroot 15 Bareroot Sale Big Leaf Maple (Icer macrophyllum) Moist, part shade /full sun 1 gal;12' -20' bareroot; 10L12' bareroot 15 Bareroot Sale Cascara (Rhamnus purshiana) Moist, part shade /full sun I gal; 8'42' bareroot;8' -12' bareroot Bareroot Sale sub for Big Maple Sub - Trees/Multi- Stemmed Trees/Tall Shrubs Vine Maple (Acer circinatum) Moist, part shade /part sun 1 gal; 8' bareroot; 6' Mock Orange (Phyladelphus lewisir) Dry/Moist, part shade /part sun 1 gal; 8' bareroot; 6' Shrubs Salal (Gaultheria shallop) Low Oregon Grape (bfahonia nervosa) Indian plum (Oemleria cerasiformis) Red Flowering Current Ribes sanguineum) Nootka Rose (Rosa nutkana) Thimbleberry (Rubus parvijlora) Snowberry (Symphoricarpos albus) Dry/Moist, shade /part sun Dry/Moist, shade /part sun Moist, shade /part sun Dry/Moist, part shade /full sun Moist/dry, full sun Moist, full sun, some shade Moist/dry, part shade /full sun I gal;4' -6' bareroot;3' 1 gal; 2'4' bareroot; 2' I gal;4' -6' bareroot;3' I gal;4' -6' bareroot;3' 1 gal;4' -6' bareroot;3' I gal;4' -6' bareroot;3' 1 gal;4' -6' bareroot;3' bareroot bareroot 1 gallon 1 gallon bareroot bareroot bareroot bareroot bareroot 30 Bareroot Sale 0 Bareroot Sale 0 Bareroot Sale 0 Bareroot Sale 50 Bareroot Sale 10 Bareroot Sale 40 Bareroot Sale 40 WPC 50 Bareroot Sale 250 Groundcover Fringecup (Telima grand(ora) Dry/Moist, full sun/part shade 6 " -12" 4" pots 10 other Kinnikinnick (Arctostaphylos uva -ursi) Dry, full sun/part shade 6 " -12" 4" pots 20 WPC Woodland Strawberry (Fragaria vesca) Dry/Moist, part sun/full shade 6 " -12" 4" pots 20 WPC Ferns Sword Fern (Polystichum munitum) Moist/Dry, full shade /part sun 4' 1 gallon 10 WPC Lady Fern (4thyrium felix femina) Wet/moist, full shade /part sun 4' 1 gallon 5 other PF = species requires permanently flooded conditions, SF = species requires seasonally flooded conditions, PS = species requires permanently saturated conditions, SS = species requires seasonally saturated conditions 2 The recommended spacing intervals highlighted in bold are the preferred spacing interval for this site in its present condition. 3 WPC: The King Conservation District's Wetland Plant Cooperative Nursery, Bareroot Sale: The King Conservation District's Annual Bareroot Sale, Other: Local native plante nurseries. Optional Common Name (Scientific Name) Species Recommended for Wetland Area Site Requirements Wetland Area: This area is characterized by saturated soils and a mix of native and invasive vegetation. Habitat potential is great considering the direct connection of the wetland to Riverton Creek. The likely historical plant association of Red alder /Salmonberry /cedar is a good target for restoration of the site. Low streamside benches are suitable for planting wetland emergent vegetation. This zone occupies approximately 7,000 square feet of which approximately 5,000 square feet is unvegetatated. Trees Western Red Cedar (Thuja plicata) Red Alder (Alnus rubra) Sitka Spruce (Picea sitchensis) Sub- Trees/Multi- Stemmed Trees/Tall Shrubs Pacific willow (Salix lasiandra) Sitka Willow (5alix sitchensis) Shrubs Black Twinberry .onicera involucrata) Salmonberry (Rubus spectabilis) Red Osier Dogwood Jornus sericea) Emergents Slough Sedge (Carex obnupta) Small fruited Bullrush IZcirpus microcarpus) Skunkcabbage (Lysichitum americanum) Ferns Sword Fern (Polystichum munitum) Lady Fern (4thyrium felix femina) Wet/moist, full shade /part sun Moist, part shade /full sun Wet/moist, part shade /full sun Wet, full sun Moist/Wet, part shade /full sun Wet/moist, part shade /part sun Wet/moist, part shade /part sun Wet/moist, part shade /full sun SF/PS, part shade /full sun, emergent zone SF /SS, part shade/full sun, wet meadow /forested wetland PS full shade/part sun, wet river /pond/lake margin, forested wetland. Size of Plant Plant Spacing Recommended 2 Recommended 1 gal;12' -20' bareroot; 10L12' I gal;12' -20' bareroot; IOL 12' 1 gal;12' -20' bareroot; 10L12' 1 gal; 3' -4' cuttings; 2' 1 gal; 3' -4' cuttings; 2' 1 gal; 4' -6', bareroot; 3' -4' I gal; 4' -6', bareroot; 1 gal; 3'-4' cuttings; 2' I gal; 2 ', plugs; 6 "42" 1 gal; 2', plugs; 6 "42" 2' bareroot bareroot bareroot bareroot/ cuttings bareroot/ cuttings bareroot bareroot bareroot 1 gallon 1 gallon 1 gallon Number of Plants Needed by Species 12 Bareroot Sale 0 WPC 10 Bareroot Sale 0 Bareroot Sale 50 Bareroot Sale 60 Bareroot Sale 60 Bareroot Sale 60 Bareroot Sale 20 20 20 WPC WPC WPC Moist, full shade /part sun 4' 1 gallon optional WPC Wet/moist, full shade /part sun 4' 1 gallon optional other 312 PF = species requires permanently flooded conditions, SF = species requires seasonally flooded conditions, PS = species requires permanently saturated conditions, SS = species requires seasonally saturated conditions 2 The recommended spacing intervals highlighted in bold are the preferred spacing interval for this site in its present condition. WPC: The King Conservation District's Wetland Plant Cooperative Nursery, Bareroot Sale: The King Conservation District's Annual Bareroot Sale, Other: Local native plante nurseries. • • Trees Douglas fir (Pseudotsuga menziesii) Big Leaf Maple (Acer macrophyllum) Cascara (Rhamnus purshiana) Sub - Trees/Multi- Stemmed Trees/Tall Shrubs Vine Maple (Acer circinatum) Mock Orange (Phyladelphus lewisii) Shrubs Salal (Gaultheria shallon ) Low Oregon Grape (Mahonia nervosa) Indian plum (Oemleria cerasiformis ) Red Flowering Current (Ribes sanguineum ) Nootka Rose (Rosa nutkana) Thimbleberry (Rubus parviflora ) Snowberry (Symphoricarpos albus) Groundcover Fringecup (Telima grandiflora ) Kinnikinnick (Arctostaphylos uva -ursi) Woodland Strawberry (Fragaria vesca) Ferns Sword Fern (Polystichum munitum) Lady Fern (Athyrium felix femina ) Species Recommended for the Hundtofte /Cambell Wetland Planting Moist/dry, full sun Moist, part shade/full sun Moist, part shade /full sun Moist, part shade/part sun Dry/Moist, part shade /part sun Dry/Moist, shade/part sun Dry/Moist, shade/part sun Moist, shade /part sun Dry/Moist, part shade /full sun Moist/dry, full sun Moist, full sun, some shade Moist/dry, part shade /full sun Dry/Moist, full sun /part shade Dry, full sun/part shade Dry/Moist, part sun /full shade Moist/Dry, full shade/part sun Wet/moist, full shade/part sun Plant Spacing Size of Plant Number of Plants Common Name (Scientific Name) Site Requirements I Recommended 2 Recommended Needed by Species Species Recommended for Wetland Buffer Area Wetland Buffer Area: This zone is characterized by fill soils and low slopes of varying steepness of which boarder the stream and associated seasonally innundated areas. The buffer is dominated by turf grasses and has already been planted with salvaged conifers, ferns, and a recent native bare root installation. Its nutrient poor, well drained soils at the top of the slope are partially shaded by mature decidious trees and the richer, more frequently saturated native soils are mostly shaded by the adjoining wetland's decidious trees. Native plant species currently present on the site suggest a Red alder /Salmonberry plant association for the wet benches along the stream and wetland, and a Douglas Fir /Sword fern plant association for the upland slope. Some dry fringe and groundcover plants should be installed as highlights after all construction is finished to aviod impact. This zone occupies approximately 4,000 square feel. 1 gal;12' -20' bareroot; 10' -12' 1 gal;12' -20' bareroot; 10' -12' 1 gal; 8' -12' bareroot; 8' -12' 1 gal; 8' bareroot; 6' 1 gal; 8' bareroot; 6' 1 gal;4' -6' bareroot; 3' 1 gal; 2' -4' bareroot; 2' 1 gal;4' -6' bareroot; 3' 1 gal;4' -6' bareroot; 3' 1 gal;4' -6' bareroot; 3' 1 gal;4' -6' bareroot; 3' 1 gal;4' -6' bareroot; 3' 6 " -12" 6 " -12" 6 " -12" 4' 4' bareroot bareroot bareroot bareroot bareroot 1 gallon 1 gallon bareroot bareroot bareroot bareroot bareroot 4" pots 4" pots 4" pots 1 gallon 1 gallon 15 Bareroot Sale 15 Bareroot Sale Bareroot Sale 30 Bareroot Sale 3 Bareroot Sale 10 Bareroot Sale 10 Bareroot Sale 50 Bareroot Sale 3 Bareroot Sale 100 Bareroot Sale 40 WPC 60 Bareroot Sale 10 other 20 WPC 20 WPC 10 WPC 5 other Materials Source Notes 1 PF = species requires permanently flooded conditions, SF = species requires seasonally flooded conditions, PS = species requires permanently saturated conditions, SS = species requires seasonally saturated conditions 2 The recommended spacing intervals highlighted in bold are the preferred spacing interval for this site in its present condition. WPC: The King Conservation District's Wetland Plant Cooperative Nursery, Bareroot Sale: The King Conservation District's Annual Bareroot Sale, Other: Local native plante nurseries. sub for Big Maple for dry fringe for dry fringe for dry fringe for dry fringe • 0 )1\ S Plant Spacing Common Name (Scientific Name) Site Requirements' Recommended 2 Species Recommended for Wetland Area Wetland Area: This area is characterized by saturated soils with onsite, weedy wetland vegetation. Habitat potential is great considering the wetland's non - isolated charactor and direct connection to Riverton Creek. Me likely historical lowland plant association of Red alder /Salmonberry/Redcedar is a good target for restoration of the site. Low streamside benches also suggest natural enclaves of Small fruited Bullrush, Slough Sedge and Skunkcabbage. This zone occupies approximately 7,S00square feet. Trees Western Red Cedar (Thuja plicata) Red Alder (Alnus rubra) Sitka Spruce (Picea sitchensis) Sub - Trees/Multi Stemmed Trees /Tall Shrubs Pacific willow (Salix lasiandra) Sitka Willow ( Salix sitchensis) Shrubs Black Twinberry (Lonicera involucrata) Salmonberry (Rubus spectabilis) Red Osier Dogwood (Cornus sericea) Emergents Slough Sedge (Carex obnupta) Small fruited Bullrush (Scirpus microcarpus) Skunkcabbage (Lysichitum americanum) Ferns Sword Fern (Polystichum munitum) Lady Fern (Athyrium felix femina ) Wet/moist, full shade/part sun Moist, part shade/full sun Wet/moist, part shade /full sun Wet, full sun Moist/Wet, part shade /full sun Wet/moist, part shade /part sun Wet/moist, part shade /part sun Wet/moist, part shade /full sun SF /PS, part shade /full sun, emergent zone SF /SS, part shade /full sun, wet meadow /forested wetland PS full shade /part sun, wet river /pond /lake margin, forested wetland. 1 gal;12' -20' bareroot; 10' - 12' I gal;12' -20' bareroot; 10' - l2' I gal;12' -20' bareroot; 10' - 12' I gal; 3' -4' cuttings; 2' I gal; 3' -4' cuttings; 2' I gal; 4' -6', bareroot; 3' -4' I gal; 4' -6', bareroot; 3' -4' 1 gal; 3' -4' cuttings; 2' I gal; 2', plugs; 6 " -12" I gal; 2', plugs; 6 " -12" 2' Moist, full shade /part sun 4' Wet/moist, full shade /part sun 4' Size of Plant Number of Plants Recommended Needed by Species • • bareroot bareroot bareroot bareroot/ cuttings bareroot/ cuttings bareroot bareroot bareroot/ cuttings 1 gallon 1 gallon 1 gallon 1 gallon 1 gallon 30 Bareroot Sale 12 WPC 10 Bareroot Sale 50 Bareroot Sale must special order 150 Bareroot Sale must special order 100 Bareroot Sale 200 Bareroot Sale must special order 200 Bareroot Sale 20 WPC 20 WPC not ready untill 15 WPC 2007( ?) 15 WPC 10 other I PF = species requires permanently flooded conditions, SF = species requires seasonally flooded conditions, PS = species requires permanently saturated conditions, SS = species requires seasonally saturated conditions 2 The recommended spacing intervals highlighted in bold are the preferred spacing interval for this site in its present condition. 3 WPC: The King Conservation District's Wetland Plant Cooperative Nursery, Bareroot Sale: The King Conservation District's Annual Bareroot Sale, Other: Local native plante nurseries. • Wet/and1esorces, /hc. Delineation / Mitigation / Restoration / Habitat Creation / Permit Assistance S RECEIVED iWAY 1 2006 COMMUNITY DEVELOPMENT SENSITIVE AREA STUDY AND MITIGATION PLAN FOR HUNDHOFTE PROPERTY - S. 126 STREET City of Tukwila, Washington Wetland Resources, Inc. Project #05041 Prepared By: Wetland Resources, Inc. 9505 19th Ave. SE Suite 106 Everett, WA 98208 (425) 337 -3174 For: Aaron Hundhofte Et Brie Campbell 3727 S. 126 Street Tukwila, WA 98168 March 6, 2006 9505 19th Avenue S.E. Suite 106 Everett, Washington 98208 (425) 337 -3174 Fax (425) 337 -3045 • • TABLE OF CONTENTS INTRODUCTION 2 WETLAND AND STREAM CLASSIFICATION - COWARDIN SYSTEM 3 WETLAND AND STREAM CLASSIFICATION - CITY OF TUKWILA 3 WETLAND DETERMINATION REPORT 3 BOUNDARY DETERMINATION FINDINGS 3 ANALYSIS OF EXISTING FUNCTIONS AND VALUES 4 PROPOSED DEVELOPMENT PLAN 5 PROPOSED MITIGATION PLAN 7 PLANTING NOTES 8 PROJECT SUCCESS AND COMPLIANCE 10 PROJECT MONITORING 11 MAINTENANCE 12 CONTINGENCY PLAN 12 ASSURANCE DEVISE 13 ESTIMATED PROJECT COST 14 USE OF THIS REPORT 14 FIELD DATA SHEET 15 SENSITIVE AREAS STUDY AND MITIGATION PLAN MAP SHEET 1 / 1 SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126"' STREET 1 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 INTRODUCTION Wetland Resources, Inc. was contracted by Aaron Hundhofte and Brie Campbell to identify and delineate jurisdictional wetlands for the approximate one -acre site located at 3725 S. 126 Street in the city of Tukwila, Washington. The property is further located as a portion of Section 10, Township 23N, Range 4E, W.M. Access to the site is via S. 126 Street along the northern property boundary. The on -site fieldwork was conducted on February 22, 2005. Anticipated development will include construction two single- family homes with parking and improvements to the existing access driveway. The Washington State Department of Ecology Wetlands Identification and Delineation Manual, 1997, was used to identify and define wetland conditions. The City of Tukwila Municipal Code (TMC) Chapter 18.45 was used to classify wetland and stream systems. The study area is comprised of three existing legal tots, each rectangular with a long north -south axis. Topography on the site is comprised of an east aspect slope. Surrounding land uses are comprised of a combination of commercial development and single- family residences. The majority of the site has been historically cleared. The property currently contains an existing gravel driveway and two existing houses in the southern portion of the eastern lot. The southwestern portion of the site is currently comprised of a fenced maintained lawn. Vegetation within the remaining northern portion of the site is comprised of a combination of maintained grasses, red alder, Japanese knotweed, Himalayan blackberry, reed canarygrass, salmonberry, and willows. The property contains a Type 2 wetland associated with a Type 2 stream. The stream, known as Riverton Creek, is located mainly off -site to the east. The off -site stream flows north, and eventually drains into the Duwamish River. It is classified as a Type 2 watercourse because it is smaller than a Type 1 stream and is used by salmonid fish. The on -site wetland is hydrologically connected to the off -site stream, and therefore meets the criteria for a Type 2 wetland. The on -site portion of the wetland has been historically disturbed. The outer western portion of the wetland is cleared, and dominated by maintained grasses. Vegetation within the eastern on -site portions of the wetland is dominated by invasive /non - native species with a red alder canopy. Pursuant to the City of Tukwila Municipal Code (TMC), Chapter 18.45.080, Type 2 wetlands typically receive 80 -foot buffers and Type 2 streams typically receive 100 -foot buffers. For this site, the 80 -foot wetland buffer is the more restrictive buffer and will be regulated under Chapter 18.45.080. The standard 80 -foot wetland buffer covers approximately 80 percent of the site. The existing use of the single- family homes and associated lawns in the southern portion of the site are allowed, pursuant to TMC 18.45.070. SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET • • 2 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • WETLAND AND STREAM CLASSIFICATION - COWARDIN SYSTEM According to the Cowardin System, as described in Classification of Wetlands and Deepwater Habitats of the United States, the classification for the on -site wetland and the off -site stream are as follows: Wetland: Palustrine, Forested Wetland, Broad - leaved Deciduous, Seasonally Saturated. Stream: Riverine, Perennial, Streambed, Cobble- Gravel. WETLAND AND STREAM CLASSIFICATION - CITY OF TUKWILA Under the City of Tukwila Municipal Code (TMC), Chapter 18.45, the on -site wetland and off -site stream are classified as follows: Type 2 Wetland: The subject wetland is hydrologically connected (non- isolated) to an off -site Type 2 watercourse. Type 2 wetlands typically receive 80 -foot protective buffers in the city of Tukwila. Type 2 Watercourse: The off -site stream is known as Riverton Creek. This stream is a perennial stream, smaller than a Type 1 stream that is presumed to support salmonid fish. Type 2 watercourses typically receive 100 -foot protective buffers in the city of Tukwila. SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126'" STREET WETLAND DETERMINATION REPORT Methodology On site, the routine methodology described in the Washington State Wetlands Identification and Delineation Manual (Washington State Department of Ecology Publication #96 -94, March 1997) was used for this determination, as required by the City of Tukwila. Under this method, the process for making a wetland determination is based on three sequential steps: 1. Examination of the site for hydrophytic vegetation (species present and percent cover); 2. If hydrophytic vegetation is found, then the presence of hydric soils is determined. 3. The final step is determining if wetland hydrology exists in the area examined under the first two steps. The following criteria descriptions were used in the boundary determination: 3 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • S Vegetation Criteria The Washington State Wetlands Identification and Delineation Manual, 1997 edition, defines hydrophytic vegetation as the sum total of macrophytic plant life that occurs in areas where the frequency and duration of inundation, or soil saturation, produce permanently or periodically saturated soils of sufficient duration to exert a controlling influence on the plant species present. One of the most common indicators for hydrophytic vegetation is when more than 50 percent of a plant community consists of species rated "Facultative" and wetter on lists of plant species that occur in wetlands. Soils Criteria and Mapped Description The Washington State Wetlands Identification and Delineation Manual, 1997 edition, defines hydric soils as those that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. Field indicators are used for determining whether a given soil meets the definition for hydric soils. The subject property is not mapped in the Soil Survey of King County Area Washington. Hydrology Criteria The Washington State Wetlands Identification and Delineation Manual, 1997 edition, states that "areas which are seasonally inundated and /or saturated to the surface for a consecutive number of days z12.5 percent of the growing season are wetlands, provided the soil and vegetation parameters are met. Areas inundated or saturated between 5 and 12.5 percent of the growing season in most years may or may not be wetlands. Areas saturated to the surface for less than 5 percent of the growing season are non - wetlands." Field indicators are used for determining whether wetland hydrology parameters are met. BOUNDARY DETERMINATION FINDINGS Onsite Wetland: Vegetation within the on -site wetland is dominated by immature red alder (Alnus Rubra, Fac), Himalayan blackberry (Rubus discolor, FacU), Japanese knotweed (Polygonum cuspidatum, FacU), salmonberry (Rubus spectabilis, Fac +), reed canarygrass (Phalaris arundinacea, FacW), and willows (Salix, sp., Fac -Obl). Underlying soils are black (10YR 2/1) sandy loam and gravelly sandy loam about 18 inches thick. The soils were saturated to the surface at the time of investigation. The dominance of species rated "Facultative" and wetter meets the criteria for hydrophytic vegetation in areas mapped as wetland. The presence of low chroma, saturated soils suggest that reducing conditions are present long enough during the growing season to develop anaerobic conditions in the upper part of the soil horizon. These characteristics meet the criteria for wetland soils. The areas mapped as wetland were saturated in the upper part at the time of the investigation, and appear to be seasonally inundated and /or saturated to the surface for a consecutive number of days _12.5 percent of the growing season, thereby fulfilling wetland hydrology criteria. SENSITIVE AREA STUDY AND MITIGATION PLAN 4 MARCH 6, 2006 HUNDHOFTE - S. 126 STREET WETLAND RESOURCES, INC. #05041 • • Non - wetland: The areas mapped as non - wetland on this site are mainly comprised of maintained grasses and ornamental tree species. Herbaceous species include bentgrasses (Agrostis, species, Fac- FacW), English plantain (Plantago lanceolata, Fac), and common dandelion, Taraxacum officinale, FacU). The soils within the non - wetland areas are dark yellowish brown (10YR 4/4) gravelly sandy loam about 18 inches thick. These soils were dry at the time of our investigation. Based on these characteristics, wetland soils are not present within the areas mapped as non - wetland. Based on the lack of field indicators, it appears that the non - wetland areas of the site are saturated to the surface for less than 12.5 percent of the growing season, thereby not fulfilling wetland hydrology criteria. ANALYSIS OF EXISTING FUNCTIONS AND VALUES The methodology for this biological functions assessment is based on professional opinion developed through past field analyses and interpretations. This assessment pertains specifically to the on -site wetland and buffers. Generally, vegetation on this site has been highly impacted by historic land use. The outer western portion of the wetland is cleared, and dominated by maintained grasses. Vegetation within the eastern on -site portions of the wetland is dominated by invasive /non - native species with a red alder canopy. The buffer associated with the on- site wetland is comprised of an existing gravel driveway and maintained grasses, and void of tree and shrub canopies. Hydrologic Control Hydrologic control (flood control and water supply) is a very important function provided by wetlands and buffers. Due to their depressional characteristics, wetlands effectively function as natural water storage areas during periods of high precipitation, and are able to accumulate stormwater runoff. Wetlands with limited outlets store greater amounts of water than wetlands with unrestricted flow outlets. Forested areas retain much of the stormwater and help prevent soil erosion through hydrologic flows. The vegetation in the wetland stores any excess stormwater that reaches the wetlands. Conifer forested wetlands and buffers have potential to retain more stormwater and help prevent soil erosion to a greater degree than immature deciduous forests or scrub shrub areas. Areas dominated by invasive species are less effective for the function of hydrologic control. Water Quality Improvements Water quality improvement is another evaluated function. Surface runoff during periods of precipitation increases the potential for sediments and pollutants to enter surface water. Wetlands improve water quality by acting as filters as water passes through them, trapping sediments and pollutants from surface water. Ponded areas within depressional wetlands also allow sediments to drop out of suspension, thereby increasing water quality. As development increases, the potential for polluted water to SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET 5 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • reach wetlands and streams also increases. Vegetated buffers helps to slow overland flows and allows sediment to settle before entering the watercourse. Conifer forests with a layering canopy of native trees, shrubs and forbs provide the highest potential for this function. Unnaturally high inputs of pollutants, which are often found in urbanized areas, along with the size of the wetlands and the vegetation structure within them are the main limiting factors of this function. Wildlife Habitat Wetlands have potential to provide diverse habitat for aquatic, terrestrial, and avian species for nesting, rearing, resting, cover, and foraging. Wetland buffers with multi canopy environments have potential to provide resources such as food, water, thermal cover, and hiding cover in close proximity, which wildlife species need to thrive. Wildlife species are commonly dependent upon a variety of intermingled habitat types, including wetlands, adjacent uplands, large bodies of water, and movement corridors between them. Vertical habitat diversity provides greater potential wildlife function than single canopy environments. Species diversity in a similar manner provides greater potential wildlife function than homogeneous plant communities. In addition, stream systems and their associated buffers allow for movement corridors, which become increasingly important as areas become developed. Human intrusion, including development within and adjacent to wetlands, and impacts to movement corridors are the most limiting factors for wildlife habitat functions. Analysis The subject wetland is a riparian wetland connected through surface flow to Riverton Creek. The majority of the wetland is comprised of sporadic immature native trees in the canopy with a mixed native and non - native scrub -shrub understory. This wetland has moderate potential to trap and slowly release water downstream during and after storm events. Existing vegetation within this wetland may also have potential to trap and filter out excess pollutants before the water enters the stream. This is a small wetland surrounded by urban development. While limited in size and native species diversity, this wetland has moderate potential for providing habitat for some birds, small mammals, and amphibians. The tree canopy also provides shade along the creek. Limiting factors to greater function and value of this wetland are associated with the lack of a viable buffer, historic human disturbance, and coverage of invasive species. Based on these conditions this wetland has moderate potential to provide typical wetland functions and values in the landscape. Removing invasive species and densely planting a diversity of native trees and shrubs may greatly improve the functions of this wetland over time. The on -site wetland buffer currently has low potential for providing typical buffer functions. The lack of a tree or shrub canopy represents the limiting factors for this function. This buffer provides virtually no wetland protection, wildlife habitat, hydrologic control, or water quality improvements. Planting a diversity of native trees and shrubs would greatly improve functions of this buffer over time. SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET 6 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • PROPOSED DEVELOPMENT PLAN Project Description The anticipated development plan includes construction of two new single- family homes within the western portion of the site along with parking and low impact improvements to the existing access driveway. Discussion of Potential Alternatives and Avoidance The on -site wetland and associated 80 -foot protective buffer cover approximately 80 percent of the site. The non - wetland /buffer areas on this site are within the southwest corner. Access to this portion of the site and the existing buildings is currently being provided by an existing gravel driveway located through approximately the middle portion of the standard 80 -foot wetland buffer. Pursuant to TMC 18.45.080, up to 50 percent buffer reduction is allowed if the applicant demonstrates that the existing buffer conditions are degraded and that increased wetland protection and buffer enhancement would be provided. This would result in a 40 -foot buffer width along the wetland in the northern portion of the site. While a 50 percent buffer reduction is feasible for this site, the existing gravel driveway would continue to he within the outermost portion of a reduced 40 -foot wetland buffer. Under strict application of TMC 18.45, a proposed development design would require relocation of the access driveway so that it is outside the minimum allowed wetland buffer area. Relocating the driveway to the west of the 40 -foot buffer line, however, would result in significant on -site impacts and considerable financial hardship for the applicants. The work would require extensive excavation along the slope in the western part of the site for creation of an appropriate new road grade and associated side slopes. Exposed soils could increase potential for erosion and siltation into the adjacent wetland and stream areas. Shifting the driveway to the west would also require removal of several large established trees along the western property boundary. The existing trees occur along the outer portion of the standard 80 -foot wetland buffer line. While these trees currently offer limited buffer functions, due to the heavily disturbed and unvegetated area between them and the wetland boundary, they do provide an excellent visual barrier between the subject property and the adjacent property to the west. They also provide potential habitat for avian species. The wetland buffer between the existing driveway and the wetland is heavily disturbed and devoid of tree and shrub canopies. Based on the existing conditions of this site and the potential for significant impacts associated with relocating the access driveway, it is our opinion that the existing location of the driveway should be retained. In lieu of relocating the driveway and retaining a minimum 40 -foot buffer, the applicants propose an alternative innovative development design that will improve the conditions of the site. The design is intended to improve stormwater infiltration and minimize impacts to sensitive areas surrounding the proposed development site. The plan calls for SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET 7 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • retaining and improving the existing access driveway, using low - impact methods and pervious materials. Proposed driveway improvements include widening the driveway by no more than 5 feet along the western side, and then replacing the existing gravel with permeable concrete materials. The proposed width of the driveway is 15 -foot buffers. For further details of this design concept and proposed materials to be used, please refer to the Low Impact Driveway and Parking area Permeable Paving Analysis report, prepared by Ridolfi, Inc. on December 20, 2005. This low impact driveway design will result in increased potential for natural wetland recharge, flood attenuation, and water quality improvement functions by infiltrating a greater amount of stormwater on this site. By retaining the existing driveway location, site impacts have been minimized to the greatest extent possible. Potential Sensitive Area Impacts Potential impact to functions and values offered be this site could be a result of the following: increased noise, increased automobile passage, human and domestic animal intrusion in the designated sensitive areas and buffers, and increased impervious surfaces associated with new house roofs. This development plan will not result in vegetation clearing within the sensitive areas and buffers. The development and its proposed mitigation measures are not likely to adversely affect salmonids or their habitat. Generally, vegetation within the wetland and buffer areas on this site has been highly impacted by historic land uses. The on -site buffers and a portion of the wetland are comprised of maintained grasses and are void of tree and shrub canopies. As a result, these wetland and buffer areas are severely limited in providing the typical functions and values described earlier. Dense planting of native trees and shrubs throughout the wetland and buffer areas and installation of a split rail fence on this site will greatly improve functions and values and will sufficiently offset potential impacts associated with the proposed development plan. PROPOSED MITIGATION PLAN The resulting wetland buffer widths will be a minimum of 22.5 feet and a maximum of 54.5 feet. As mitigation for proposing a buffer width below 40 feet, a wetland and buffer enhancement plan shall be implemented on this site. This plan will result in 7,500 square feet of wetland enhancement and 4,000 square feet of buffer enhancement. In addition to wetland and buffer enhancement, a split -rail fence fixed with sensitive area signs shall be installed along the proposed boundary of the wetland buffer. The fencing will provide additional protection and will clearly mark the boundary of the on -site sensitive areas. Project Goal and Objectives The goal of this mitigation plan is to sufficiently replace and improve the functions and values on this site by increasing the density and diversity of native vegetation within the on -site wetland and buffer areas. This will be achieved by having at least 75 percent survival of the native plants set forth in the approved mitigation plan by the end of five years. The species mix should resemble that proposed in the planting plans, but strict SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET 8 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • adherence to obtaining all of the species shall not be a criterion for success. By the end of the fifth growing season, the percent areal coverage of the native shrub /sapling stratum shall be 60 percent in the mitigation areas. Post - Construction Functions and Values This development plan will result in significantly increased native species density and diversity on this site and improved functions of previously degraded wetland and buffer areas. Over time, the newly planted species will provide a mixed forest of both deciduous and conifer trees and a dense understory of native scrub -shrub species. The enhanced wetland and buffer areas will provide additional hydrologic control, water quality benefits, and a dense vegetative barrier between the new development and the on -site wetland. Furthermore, the new low impact driveway and enhanced wetland and buffer areas will generally have an improved aesthetic quality over the existing conditions of the site. Based on these anticipated conditions, the intentions to replace and improve the functions and values offered by this site shall be achieved. Split Rail Fencing and Sensitive Area Signs A two rail fence shall be installed along the proposed buffer boundary to designate and to protect the sensitive areas. Fencing should be installed per the manufacturer's directions. The fence posts should be 5" x 5" x 85 ", and spaced approximately 8' apart. All fence post holes should be a minimum 30" deep. Once posts are placed in holes, the holes should be backfilled with approximately 12" of small limestone or gravel. Pour cement into hole (over small limestone) within 6" of existing grade. Fill the hole to grade with fine dirt. Sensitive area signs shall be fixed on the split rail fence. Signs shall be constructed of aluminum or similar durable material. The signs shall be secured to minimum 6' x 4" x 4" pressure treated posts buried a minimum two -foot deep in quick setting concrete. The signs shall be placed at approximately 100 -foot intervals around the perimeter of the proposed buffer. Exact sign language shall be approved by the City of Tukwila. An example of sensitive area sign language is as follows: ENVIRONMENTALLY SENSITIVE AREA THIS WETLAND AND UPLAND BUFFER ARE PROTECTED TO PROVIDE WILDLIFE HABITAT AND MAINTAIN WATER QUALITY PLEASE DO NOT DISTURB THIS VALUABLE RESOURCE. Wetland Enhancement Plan The applicant proposes to enhance 7,500 square feet of on -site wetland on this site. Prior to planting, the existing Himalayan blackberry and Japanese knotweed will be removed. Removal of these species may be conducted using hand -held tools. For best results, the roots of these species should also be removed. Any new growth should be spot sprayed or painted with an appropriate product, such as Round Up. Use of an SENSITIVE AREA STUDY AND MITIGATION PLAN 9 MARCH 6, 2006 HUNDHOFTE - S. 120 STREET WETLAND RESOURCES, INC. #05041 herbicide needs to be approved by the City. Invasive plant cuttings should be exported off -site. • • Following the removal of the undesirable species, the on -site wetland areas will be planted to native species. Plant spacing will be based on 40 percent of the enhancement area planted with trees on 10 -foot centers and 40 percent of the area planted with shrubs on 5 -foot centers. Plantings will be in groups of 2 -3 like species, however, the actual placement of individual plants shall mimic natural, asymmetric vegetation patterns. Red alder and black cottonwood shall be allowed to establish as native pioneer species. The following species shall be planted within the wetland creation area: Wetland Enhancement Planting Plan (7,500 square feet) Common Name Latin Name Size Spacing Numbers 1 Western red cedar Thuja plicata 1 gal 10' 15 2. Sitka spruce Picea sitchensis 1 gal 10' 15 3. Pacific willow Salix lucida 1 gal 5' 30 4. Black twinberry Lonicera involacrata 1 gal 5' 30 5. Red -osier dogwood Cornus sericea 1 gal 5' 30 6. Satmonberry Rubus spectabilis 1 gal 5' 30 Buffer Enhancement Plan The applicant proposes to enhance 4,000 square feet of on -site wetland buffer through planting of a diversity of native species. Plant spacing will be based on 50 percent of the enhancement area planted with trees on 10 -foot centers and 50 percent of the area planted with shrubs on 5 -foot centers. Plantings will be in groups of 2 -3 like species, however, the actual placement of individual plants shall mimic natural, asymmetric vegetation patterns. Red alder and black cottonwood shall be allowed to establish as native pioneer species. The following species shalt be planted within the buffer enhancement area: Buffer Enhancement Area Planting Plan (4,000 square feet) Common Name Latin Name Plant Size Spacing Quantity 1. Douglas fir Pseudotsuga menziesii 1 gal 10' 20 2. Big leaf maple Acer macrophyllum 1 gal 10' 20 3. Vine maple Acer circinatum 1 gal 5' 20 4. Nootka rose Rosa nutkana 1 gal 5' 20 5. Thimbleberry Rubus parviflorus 1 gal 5' 20 6. Snowberry Symphoricarpos albus 1 gal 5' 20 SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET PLANTING NOTES Timing Planting will occur in the early spring or late fall. Plants should be ordered from a reputable nursery. Care and handling of plant materials is extremely important to the overall success of the project. All plant materials recommended in this plan should be available from local and regional sources, depending on seasonal demand. Some limited 10 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • species substitution may be allowed, only with the agreement of the consulting wetland professional. Plant Distribution The plants shall be arranged in a pattern with the appropriate numbers, sizes, species, and distribution to achieve the desired vegetation coverage. The actual placement of individual plants shall mimic natural, asymmetric vegetation patterns found on similar undisturbed sites in the area. Spacing of the plantings may be adjusted to maintain existing vegetation with approval from the consulting wetland professional. Mulch Wood chips shall be used for mulching in the areas planted with trees and shrubs. All existing vegetation is to be removed from a two -foot diameter area at each planting site. Wood chips are to be placed in this two -foot diameter area at a depth of three to four inches, and not within 2" of the plant stem. Plant Marking Lath stakes or other approved marking method, such as brightly colored surveyors ribbon, shall be placed next to each installed tree and shrub to assist in locating these plants during maintenance and monitoring. Inspections A certified wetland professional shall inspect the plantings described in this plan. Due to the physical condition of the site, unusual or hidden site situations, minor adjustments to the original designs may be required prior to and during planting. These decisions will be made onsite by the City representative and /or the consulting wetland professional. SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET PROJECT SUCCESS AND COMPLIANCE Criteria for Success Upon completion of the proposed wetland and buffer enhancement, an inspection by a qualified biologist will be made to determine plan compliance. A compliance report will be supplied to the City of Tukwila within 30 days after the completion of planting. A professional landscape professional or biologist will complete the condition monitoring of the plantings in the fall, annually. A written report describing the monitoring results will be submitted to City of Tukwila after each site inspection of each monitored year for a total of 5 years. The contracted consultant will prepare a report as to the success of the project. Definition of Success The wetland and buffer enhancement areas shall support at least 75 percent of the native plants set forth in the approved mitigation plan by the end of five years. The species mix should resemble that proposed in the planting plans, but strict adherence to obtaining all of the species shall not be a criterion for success. By the end of the fifth growing season, the percent areal coverage of the native shrub /sapling stratum shall be 60 percent in the mitigation areas. 11 MARCH 6, 2006 WETLAND RESOURCES, INC. $/05041 • • Sensitive Area Enhancement Performance Standards Year 1 Year 2 Year 3 Year 5 Shrub and sapling tree coverage* >15% >30% >35% >60% Shrub and sapling tree survival 100% >85% >80% >75% Herbaceous cover* >60% >80% >90% >90% Herbaceous Survival 100% >85% *Includes beneficial native plants in that category that are recruited naturally. PROJECT MONITORING Requirements for monitoring project 1. Initial compliance report 2. Yearly site inspection (once per year in the fall) for 5 years 3. Annual reports including final report (one report submitted in the fall of each monitored year) Purpose for Monitoring The purpose for monitoring this mitigation plan shall be to evaluate its success. Success will be determined if monitoring shows at the end of 5 years that the definitions of success stated below are being met. The property owner shall grant access to the enhancement areas for inspection and maintenance to the contracted landscape or wetland specialist and the City of Tukwila biologist until the project is evaluated as successful. Vegetation Monitoring Sampling points or transects will be established for vegetation monitoring, and photo points established from which photos will be taken throughout the monitoring period. Permanent sampling points must be identified on the mitigation site plans in the first monitoring report (they may be drawn on approved restoration plans by hand). Each sampling point shalt detail herbaceous, shrub, and tree coverage. Monitoring of vegetation sampling points shall occur annually between May 15 and September 30 (prior to leaf drop), unless otherwise specified. Monitoring Reports Monitoring reports shall be submitted by October 31 of each year during the monitoring period. As applicable, monitoring reports must include descriptions /data for: a. Site plan and location map b. Historic description of project, including date of installation, current year of monitoring, restatement of mitigation / restoration goals, and performance standards c. Plant survival, vigor, and aerial coverage for every plant community (transect or sampling point data), and explanation of monitoring methodology in the context of assessing performance standards d. Slope condition, site stability, any structures or special features e. Buffer conditions, e.g., surrounding land use, use by humans, and /or wild and domestic creatures f. Observed wildlife, including amphibians, avians, and others g. Assessment of nuisance / exotic biota and recommendations for management SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET 12 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • h. Color photographs (4 "x6" in size) taken from permanent photo - points that shall be depicted on Monitoring Plan MAINTENANCE The mitigation areas will require periodic maintenance to replace vegetation mortality as necessary. Maintenance may include, but will not be limited to, removal of competing grasses (by hand if necessary), irrigation, fertilization (if necessary), replacement of plant mortality, and the replacement of mulch for each maintenance period. Chemical control, only if approved by City of Tukwila biologist, shall be applied by a licensed applicator following all label instructions. Survival The Permittee shall be responsible for the health of 100 percent of all newly installed plants for one growing season after installation has been accepted by the city of Tukwila (see Performance Standards). A growing season for these purposes is defined as occurring from spring to spring (March 15 to March 15, of the following year). For fall installation (often required), the growing season will begin the following spring. The Permittee shalt replace any plants that are failing, weak, defective in manner of growth, or dead during this growing season, as directed by the Landscape Designer, Wetland Biologist, and /or City of Tukwila Biologist. Irrigation / Watering Water shall be provided during the dry season (July 1 through October 15) for the first two years after installation to ensure plant survival and establishment. A temporary above ground irrigation system and /or water truck should provide water. Water should be applied at a rate of 1 inch of water twice per week for year 1 and 1 inch per week during year 2. CONTINGENCY PLAN If during any of the inspections, 20 percent of the plants are severely stressed, or it appears 20 percent may not survive, additional plantings of the same species may be added to the planting area. Elements of a contingency plan may include, but will not be limited to: more aggressive weed control, pest control, mulching, replanting with larger plant material, species substitution, fertilization, soil amendments, and /or irrigation. If there is a significant problem with the enhancement achieving its performance standards, the bondholder shall work with the City of Tukwila biologist to develop a Contingency Plan. Contingency plans can include, but are not limited to, regrading, additional plant installation, erosion control modifications to hydrology, and plant substitutions of type, size, quantity, and location. ASSURANCE DEVICE A performance bond or assignment of funds will be provided to the City of Tukwila for the period of five years from the completion of the restoration project. The performance bond is intended to cover the cost of plant material, labor, monitoring, maintenance, and contingency planning. This bond shall be released at the end of five SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET 13 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 years, or upon a "successful determination" for all portions of this enhancement project. The definitions of success are described below. ESTIMATED PROJECT COST Quantity of 1- gallon Plants (at 8.25 per plant) 270 Estimated Cost of Plants Materials and Labor 2,227.50 USE OF THIS REPORT This Sensitive Area Study and Wetland Mitigation Plan is supplied to Aaron Hundhofte and Brie Campbell as a means of determining on -site sensitive area conditions. This report is based largely on readily observable conditions and, to a lesser extent, on readily ascertainable conditions. No attempt has been made to determine hidden or concealed conditions. Reports may be adversely affected due to the physical condition of the site and the difficulty of access, which may lead to observation or probing difficulties. The laws applicable to wetlands are subject to varying interpretations and may be changed at any time by the courts or legislative bodies. This report is intended to provide information deemed relevant in the applicant's attempt to comply with the laws now in effect. The work for this report h as conformed to the standard of care employed by wetland ecologists. No other representation or warranty is made concerning the work or this report and any implied representation or warranty is disclaimed. If you should need any further information regarding the sensitive areas and buffers on this property, please contact our office at (425) 337 -3174. Wetland Resources, Inc. Andrea Bachman Senior Wetland Ecologist SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE - S. 126 STREET • • 14 MARCH 6, 2006 WETLAND RESOURCES, INC. #05041 • • Field Data Hundhofte - WRI# 05041 Investigation Date: February 22, 2005 Pit Depth Texture Color Moisture Species % Status Strata S1 0 -18" Gravelly Sandy Loam 10YR 2/1 sat Ranunculus repens 20 Fac Tree Wetland Agrostis sp. 30 Fac -FacW Herb Poa sp. 15 Fac -FacW Herb Conclusion: Wetland - Parameters for hydrophytic vegetation, hydric soils, and wetland hydrology are met. 52 0 -18" Sandy Loam 10YR 2/1 sat Alnus rubra 25 Fac Tree Wetland Rubus discolor 20 FacU Shrub Rubus spectabilis 10 Fac+ Shrub Salix sp. 10 Fac -Obl Shrub Phalaris arundinacea 55 FacW Herb Polygonum cuspidatum 15 FacU Herb Conclusion: Wetland - Parameters for hydrophytic vegetation, hydric soils, and wetland hydrology are met. S3 0 -18" Gravelly Sandy Loam 10YR 4/4 dry Agrostis sp. 30 Fac -FacW Herb Non - Wetland Plantago lanceolata 10 Fac Herb Taraxacum officinale 10 FacU Herb Conclusion: Non - Wetland - Parameters for hydrophytic vegetation, hydric soils, and wetland hydrology are not met. 15 Scale 1" = 30' 30 60 PLEASE NOTE: THE STREAM LOCATION DEPICTED ON THIS MAP IS APPROXIMATE, AND DOES NOT REPRESENT AN ACTUAL STREAM SURVEY. APPROXIMATE STREAM LOCATION WAS BASED ON AERIAL PHOTOGRAPHY. LEGEND X WETLAND WETLAND ENHANCEMENT BUFFER ENHANCEMENT PROPOSED BUFFER WITH SPLIT RAIL FENCE 40' BUFFER LINE 80' BUFFER LINE • SENSITIVE AREA SIGN X • • TYPE 2 5 1 � IB ?aos W�puc�;a i,r F te:: e.200 id 10111 u plinomplir A jivi7 ---- A LIVIrr ii Ad MIMI 3_r• , At, A, Ar Air Ar d Air , ArAdvArArAf Ar Ar .A44, P► 14" 8 ' LOT 2 11" 0 11" 5' HOUSE 2 150' TO R.O.W. EXISTING BLDG LOT 3 EX. YARD 10' 10' a CL 5' 1 i HOUSE 1 012" G 10" LOT 1 2 -5r 3 -4CD a \ EX. BLD A. � ..- e r n ' SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE PROPERTY - S 126TH STREET Section 10, Township 23 North, Range 4 East, W.M. 10" >, N I. __AL-- �N COV to PROPOSED BUFFER LINE BUFFER ENHANCEMENT 4,000 SF TYPE 2 WETLAND 7,500 SF TO BE ENHANCED SENSITIVE AREA STUDY Et MITIGATION PLAN MAP HUNDHOFTE PROPERTY - S. 126TH ST. City of Tukwila, Washington Aaron Hundhofte a Brie Campbell 3727 S. 126th St. Tukwila, WA 98168 Sheet 1/1 Job # 05041 Drawn by: A Bachman Date: March 6, 2006 1 Wet /andRiesoyrces, /hc. .. '�,�Gelineation / Mitigation / Reuoration /Habitat Creation /Permit Assistance 9505 19th Avenue S.E. Suite 106 Everett,Washingtan 98208 Phone (425) 337-3174 Fax (425) 337-3045 E -mail: mailbox®wetlandresources.com DRAFT TECHNICAL MEMORANDUM RECEIVED DATE: December 12, 2005 DEC 1 3 2005 TO: Aaron Hundtofte and Brie Campbell 1 ur■vvij FROM: Joe Mathieu, P.E., RIDOLFI Inc. Z1V PUBLIC WORKS SUBJECT: Hundtofte - Campbell Low Impact Driveway and Parking Area Permeable Paving 1.0 INTRODUCTION 2.0 BACKGROUND 3.0 METHODOLOGY • • This memorandum evaluates the use of pervious paving materials compared to conventional paving for a driveway and parking area at the Hundtofte - Campbell property located at 3727 South 126th Street in Tukwila, Washington. The Western Washington Hydrologic Model (WWHM) was used to evaluate flow exceedances as well as compare predicted peak flows for the pre - developed condition and two developed conditions of using impervious paving verses pervious paving. The results indicate that pervious paving exceeds the two year flows about 65% less and the 50 -year flows about 96% less than impervious paving. Pervious paving also accounts for a 44% reduction in peak flows as compared to impervious paving. The Hundtofte - Campbell property consists of three contiguous rectangular lots oriented along a north -south axis. Riverton Creek is adjacent to the east of the property and a wetland associated with the creek extends onto the northeastern sections of the property. Riverton Creek is classified as a Type 2 stream and the wetland is classified as a Type 2 wetland. The Tukwila Municipal Code mandates a 100 -foot buffer for Type 2 streams and an 80 -foot buffer for Type 2 wetlands. The wetland and 80 -foot buffer encompass about 80% of the property; the existing gravel driveway and parking area (about 4615 square feet) are almost entirely within the 80 -foot wetland buffer (Figure 1). Hundtofte - Campbell propose to change the lot lines at their property to allow for building three houses. Low impact development (LID) techniques will be used to minimize construction impacts and reduce stormwater runoff flows following development. The use of pervious paving material is proposed to allow for infiltration and reduce stormwater flows. This report analyses the effectiveness of permeable paving as compared to impervious surfacing as a potential LID technique. 3.1 Pre - Developed Conditions The Washington State Department of Ecology (WDOE) WWHM was used to model flow duration and peak flows for the driveway and parking area at the Hundtofte- Campbell property. The pre - developed conditions were modeled as forest with underlying forest till soils. This type of environment is typical for pre- developed areas in Western Washington. W W HM_TechMemoFinal_051212.doc 1 12/12/05 IIII AFT Technical Memorandum: Hundtofte- Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 Glacial till soils were assumed because of the lack of site - specific soils information. These soils typically have relatively low infiltration rates; the lower infiltration rates result in a more conservative estimate of stormwater flows. The Type 2 wetland in the northwest corner of the property was modeled as saturated forest with underlying till soils. Because the model used for this analysis was developed for Western Washington, the WWHM default values for infiltration rates for these types of soils in the undeveloped scenario were assumed to accurately characterize these parameters. Table 1 summarizes the WWHM inputs used for the pre - developed analysis. 3.2 Developed Conditions Two developed scenarios were modeled. Both developed conditions included roof and parking areas for future build -out. These areas were estimated from the maximum allowed area based on setbacks for the proposed lot boundaries. These areas were intentionally maximized to provide a conservative estimate of stormwater flows. Figure 2 details the proposed extents of development. 3.2.1 Impervious Paving The first developed scenario was modeled based on conventional roof, driveway, and parking area construction. These areas were assumed to be 100% impermeable. The soil parameters input for the undeveloped portions of the site were identical to those input for "pre- developed site" model. Table 2 summarizes the WWHM inputs used for the conventionally developed analysis. 3.2.2 Pervious Paving The second "developed" model analysis was based on identical build out conditions as the first scenario with the exception of the materials used to construct the driveway, walkway, and parking areas. Under this scenario, these surfaces were modeled as permeable paving materials. Further, the road base under the primary driveway was modeled as a detention /infiltration pond as recommended by the WDOE Stormwater Management Manual for Western Washington and the Puget Sound Action Team LID Technical Manual. This required the input of several "pond" parameters, which include underlying soil type, short term infiltration rate, long term infiltration rate and a correction factor. The short term infiltration rate is used to calculate infiltration soon after the installation of the infiltration infrastructure. The long term infiltration rate aids in the calculation of attenuated infiltration after the surface has been in service for some time. It is assumed that some pore clogging and compaction will decrease the infiltration efficiency of the surface. The correction factor is used as a factor of safety, which further decreases the infiltration rates used in calculations of infiltration efficiency. For the purposes of this analysis, conservative values for these parameters were assumed. Table 3 summarizes the WWHM inputs parameters used for the developed condition using pervious paving surfaces. Figure 3 illustrates two proposed types of permeable "paving" surface. 4.0 MODELING RESULTS The Western Washington Hydrologic Model returns flow duration curves and peak values for the 2, 5, 10, 25, 50 and 100 year flow events as output. These output curves are based on 50- WWHM TechMemoFinal_051212.doc 2 1110 1;tAFT Technical Memorandum: Hundtofte- Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 years of regional rainfall data. Figure 1 illustrates the flow duration curves for the three modeled scenarios. The flow /exceedance curve (Figure 4) shows the estimated number of times a specified flow is exceeded over the 50 year model period. Figure 4 clearly illustrates that the incorporation of permeable materials reduces the number of flow exceedances when compared to the performance of the conventional paving. On average the number of exceedances is 65% less under low (2 -year peak) flows and up to 96% less at 50 -yr peak flows. Return periods are expressions or measures of how often a hydrologic event of given size or magnitude should, on an average, be equaled or exceeded. For example a 50 -year frequency flood should be equaled or exceeded in size, on the average, only once in 50 years. In drought or deficiency studies it usually defines how many years will, on the average, be equal to or less than a given size or magnitude. Expected peak flows for 2 -, 5 -, 10 -, 25 -, 50- and 100 -year (return period) runoff flow events for the modeled area are shown in Figure 5. The peak stormwater runoff flow is, on average, 44% lower using permeable paving materials than would be seen using conventional materials for this application. 5.0 CONCLUSIONS AND RECOMMENDATIONS This analysis evaluated the effectiveness of pervious paving as a LID technique using assumptions generated at the conceptual design level. A soil analysis was not completed. In order to determine the actual size and scope of the required flow control facilities for the entire site, specific geotechnical and more complete development information will be necessary. The WWHM results indicate that the use of permeable paving materials reduces peak stormwater flows and channel forming flow frequencies when compared to conventional impervious paving. Pervious paving when combined with other low impact techniques such as green roofs, biodetention swales and pin foundations could further reduce peak flows and flow durations to flows that existed under pre - developed conditions. W WHM_TechMemoFinal_051212.doc 3 WWHM TechMemoFinal Q51212.doc • APPENDIX A Tables 4 RAFT Technical Memorandum: Hundtofte- Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 Impermeable Surfaces Element Area (ft Area (acre) Roof A 1,154 0.026 Roof B 446 0.010 Roof C 1,657 0.038 Roof D 1,368 0.031 Roof E 1,080 0.025 Covenant Parking 2,047 0.047 Primary Driveway 4,487 0.103 Shared Driveway 741 0.017 Total Impermeable 12,980 0.298 Permeable Surfaces Element Area (ft Area (acre) Wetland 7,735 0.178 Open Space 12,203 0.280 Total Permeable 19,938 0.458 Permeable Surfaces Element Area (ft Area (acre) Wetland 7,735 0.178 Forested 25,183 0.578 Total Permeable 32,918 0.756 Soil Input Parameters Underlying soil type (Forest) Till Forest Underlying soil type (Wetland) Saturated Till Forest B i 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 WWHM TechMemoFinal 051212.doc Table 1. Pre - Developed Condition Model Inputs Table 2. Developed Condition #1 (Impervious Paving) Model Inputs 5 *FT Technical Memorandum: Hundtofte- Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 Impermeable Surfaces Element Area (ft Area (acre) Roof A 1,154 0.026 Roof B 446 0.010 Roof C 1,657 0.038 Roof D 1,368 0.031 Roof E 1,080 0.025 Total Impermeable 12,980 0.131 Permeable Surfaces Element Area (ft Area (acre) Covenant Parking 2,047 0.047 Primary Driveway 4,487 0.103 Shared Driveway 741 0.017 Wetland 7,735 0.178 Open Space 12,203 0.280 Total Permeable 27,213 0.625 Permeable Paving Surface Parameters Underlying soil type Till Forest Short -term Infiltration Rate (in /hr)a 0.500 Correction Factors 4 Long -Term Infiltration Rate (in /hr)a 0.13 a Reference: Stormwater Management Model for Western Washington I 11 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 W WHM_TechMemoFinal_051212.doc 6 /DAFT Technical Memorandum: Hundtofte- Campbell Low Impact Driveway and Parking Arca Permeable Paving December 12, 2005 Table 3. Developed Condition #2 (Pervious Paving) Model Inputs WWHM TechMemoFinal_Q51212.doc • APPENDIX B Figures 7 RAFT Technical Memorandum: Hundtofte- Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 1 Hundtofte - Campbell Low Impact Driveway Project O- O -p -p- p_ 0_0_0 _ 0_0 _0_0_0 - 0- 0 - 0- 0 -0_0_ Existing Property Conditions 3727 So. 126th St., Tukwila, WA • LO N • U) A. 0 0 4 0 . 0 + r RIDOLFI Inc. 1r 1 9 . 101. roposed Hous = 1080 sf 1 10 oof D Area =1 d House Existing House Roof A Areo=1154 sf xisting Hou Roof B Areo =446 sf 108.08 115.05 663 8 sf Aaron Hundtofte and Brie Campbell Hundtofte — Campbell Low Impact Driveway Project December 12, 2005 Proposed House Roof C Area= 1657 sf Scale 1u -20' Low Impact Driveway Plan View Figure 2 FILTER FABRIC 6' LAYER— ASTM NO, 57 CRUSHED AGGREGATE BASE COMPACTED (85Z PROCTOR) CONCRETE EDGE CONSTRAINT TYPICAL PAVER INSTALLATI ❑N SECTI ❑N NOT TO SCALE 2 "LAYER— ASTM NO. 8 AGGREGATE COMPACTED NATIVE S ❑IL SUBGRADE (95Z PROCTOR) 19.7' 6.6' 9.8' 3.3' 0.9' 2.4' 0,0„* d SPECIFICATIONS UNIT SIZE - 20' X 20' X 1' AVAILABLE IN 9 STANDARD ROLL SIZES UNIT WEIGHT - 510 GRAMS (18 OZ.) OR 2.0 KG (4.5 POUNDS) STRENGTH - 5720 PSI COLOR - BLACK (STANDARD) RESIN - HDPE (WITH SOME POST- CONSUMER RECYCLED CONTENT) GRASSPAVE2 SQUARES ADJACENT GRASSPAVE2 SQUARES SEE ENLARGEMENT BELOW HYDROGROW MIX BELOW RING SUPPLIED FREE BY MANUFACTURER RINGS FILLED WITH CONCRETE SAND (CLEAN, SHARP SAND) 6' COMPACTED SANDY GRAVEL ROAD BASE 95X MODIFIED PROCTOR DENSITY COMPACTED SUBGRADE TOT OF GRASS ROOT MASS i' ABOVE TOP OF RING GRASSPAVE2 ATTACH WITH SNAP -FIT FASTENERS ROOT MASS TO FILL GRASSPAVE2 COMPACTED SANDY GRAVEL BASE COURSE TYPICAL GRASSPAVE2 PLAN AND PR ❑FILE DETAIL NOT TO SCALE lt1DAVFI Mc. 11 Aaron Hundtofte and Brie Campbell Hundtofte — Campbell Low Impact Driveway Project November 21, 2005 Figure 3 Permeable Driveway Surface Material Details DRAFT Technical Memorandum: Hundtofte - Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 18000 16000 0 1 14000 12000 m g 10000 8000 6000 4000 2000 0 Figure 4. WW HM Flow Duration Curves for Construction Material Alternatives • ■ • Predeveloped • Conventional Paving X Permeable Materials ■ _ _' _X. L` ... m. .'- ri�•'iK. j ?�'� ?�i k ^��`•' .. `' 0 0.02 0.04 Flow (CFS) 0.06 0.08 WWHM TechMemoFinal_051212.doc 12/12/05 0.18 0.16 0.14 0.12 0.1 0.08 o 0.06 0.04 0.02 0 Figure 5. INING1M Peak ROWS for Construction Materiall Predeveloped Conventional Paving El Permeable Materials ternatives 2 5 ReVarn PeriooZ 50 .r ( 100 WWHM_TechMemoFinal_051212.doc DRAFT Technical Memorandum: Hundtofte-Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 12/12/05 APPENDIX C Western Washington Hydrologic Model Output *AFT Technical Memorandum: Hundtofte - Campbell Low Impact Driveway and Parking Area Permeable Paving December 12, 2005 W W HM_TechMemoFinal_051212.doc 12/12/05 I 1 1 1 1 1 1 1 1 Project Name: Site Address: City Report Date : Gage Data Start Data End Precip Scale: I PREDEVELOPED LAND USE ' Basin : Basin 1 Flows To Point of Compliance GroundWater: No Land Use Acres TILL FOREST: 0.578 SATURATED FOREST: 0.178 ' DEVELOPED LAND USE Basin Basin 1 Flows To Point of Compliance GroundWater: No Land Use TILL FOREST: TILL GRASS: SATURATED FOREST: IMPERVIOUS: Till I Saturated : WESTERN WASHINGTON OLOGY MODEL V2 PROJECT R RT default 3727 S. 126th St. Tukwila 11/8/2005 Seatac 1948 1998 1.00 Acres 0.28 0.02332155 0.178 0.27467845 1 Flow Credits: Soil Type Infiltrate Disperse Porous Pavement Outwash 0 RCHRES (POND) INFORMATION 0 0 0 95 0 0 ANALYSIS RESULTS Flow Frequency Return Periods for Predeveloped ' Return Period Flow(cfs) 2 year 5 year ' 10 year 25 year 50 year 100 year 0.020581 0.035641 0.04631 0.060111 0.070448 0.080734 1 Flow Frequency Return Periods for Developed Unmitigated Return Period Flow(cfs) 2 year 0.084866 1 5 year 0.105242 10 year 0.118055 25 year 50 year 100 year 0.133. 0.145 0.15612 Flow Frequency Return Periods for Developed Mitigated Return Period Flow(cfs) 2 year 0.078456 5 year 0.098105 10 year 0.110537 25 year 0.125773 50 year 0.136858 100 year 0.147764 Yearly Peaks for Predeveloped and Developed- Mitigated Year Predeveloped Developed 1949 0.022 0.083 1950 0.060 0.145 1951 0.060 0.106 1952 0.018 0.061 1953 0.010 0.060 1954 0.023 0.077 1955 0.042 0.096 1956 0.037 0.088 1957 0.017 0.085 1958 0.026 0.072 1959 0.022 0.058 1960 0.037 0.084 1961 0.022 0.075 1962 0.008 0.060 1963 0.013 0.064 1964 0.023 0.085 1965 0.021 0.074 1966 0.013 0.068 1967 0.044 0.100 1968 0.016 0.102 1969 0.027 0.073 1970 0.015 0.067 1971 0.018 0.063 1972 0.051 0.120 1973 0.023 0.070 1974 0.020 0.063 1975 0.027 0.089 1976 0.022 0.069 1977 0.003 0.069 1978 0.011 0.090 1979 0.009 0.089 1980 0.018 0.079 1981 0.012 0.083 1982 0.024 0.117 1983 0.020 0.083 1984 0.018 0.075 1985 0.007 0.059 1986 0.029 0.086 1987 0.032 0.103 1988 0.009 0.049 1989 0.007 0.062 1990 0.045 0.133 1991 0.058 0.122 1992 0.011 0.066 1993 0.013 0.043 1994 0.003 0,051 1995 0.027 0.065 1996 0.061 0.119 1997 0.048 0.100 1998 0.013 0.078 Ranked Yearly Peaks for Predeveloped and Developed- Mitigated Rank Predeveloped Developed 1 0.0604 0.1331 • 2 0.0598 17 3 0.0582 10,97 4 0.0508 0.1187 5 0.0484 0.1170 1 6 0.0453 0.1058 7 0.0444 0.1029 8 0.0422 0.1018 9 0.0372 0.0999 10 0.0370 0.0995 11 0.0321 0.0955 12 0.0289 0.0899 13 0.0270 0.0892 1 14 0.0269 0.0888 15 0.0267 0.0882 16 0.0261 0.0862 17 0.0243 0.0850 18 0.0229 0.0850 19 0.0228 0.0837 20 0.0228 0.0833 1 21 0.0224 0.0831 22 0.0223 0.0826 23 0.0218 0.0794 24 0.0216 0.0784 25 0.0210 0.0774 26 0.0202 0.0752 27 0.0202 0.0749 28 0.0181 0.0740 1 29 0.0179 0.0728 30 0.0177 0.0725 31 0.0176 0.0701 32 0.0169 0.0695 1 33 0.0165 0.0690 34 0.0146 0.0681 35 0.0132 0.0673 36 0.0131 0.0656 37 0.0126 0.0646 38 0.0126 0.0643 39 0.0123 0.0632 1 40 0.0112 0.0630 41 0.0105 0.0618 42 0.0097 0.0608 43 0.0087 0.0602 1 44 0.0087 0.0597 45 0.0078 0.0595 46 0.0072 0.0576 47 0.0072 0.0508 48 0.0032 0.0492 49 0.0029 0.0427 I 1 /2 2 year to 50 year Flow(CFS) Predev Final Percentage Pass /Fail 0.0103 2674 14976 560.0 Fail 0.0109 2368 13977 590.0 Fail 0.0115 2108 13079 620.0 Fail 0.0121 1895 12246 646.0 Fail 0.0127 1691 11518 681.0 Fail 0.0133 1527 10843 710.0 Fail I 0.0139 1388 10142 730.0 Fail 0.0145 1261 9511 754.0 Fail C.0152 1129 8902 788.0 Fail 1 6.0158 1043 8402 805.0 Fail 0.0164 963 7872 817.0 Fail 0.0170 885 7425 838.0 Fail 0.0176 823 7017 852.0 Fail I C.0182 764 6623 866.0 Fail C.0188 722 6254 866.0 Fail 0.0194 669 5873 877.0 Fail 0.0200 625 5531 884.0 Fail 1 0.0206 590 5224 885.0 Fail 0.0212 550 4961 902.0 Fail n n n 1 n r n 1 n r n n n- r n n_: 1 • • ri r-i ri .l ri ri ri r1 , 1 1 - rl r-I ri . l rl ri ri r4 .H H i -r r 4 r--4 rl -, ri ri ,-4 ri ri ri ,l -ri -.i .,..1 -r4 -r1 -r1 -r1 -ri •.1 -ri •.i •ri -,i .,i -ri -.-1 -H -ri .,i -.-1 -.-1 -ri •H -H .H -H -.i -.i -.-1 -rl -ri .,i .,.1 -.-1 -.i -.-I -.i •.i -H -ri -H -H -ri ,--I ri ri ri rl ri r-i r-1 r RS f0 f0 f0 (1 rt rcs RS ft ft ft RI (0 f0 rt r0 f0 RS f0 rt RS (a ft fa f0 rt m RS f0 RS (0 (0 (0 RS f6 (0 RS f0 fa f0 RI (O RS f0 RS f0 f0 rtS f0 RS f0 b ff3 f0 f0 f0 f0 RS rt rtS RS R •H -rl •H •r+ .H - - r+ - .i - rs. 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O O O O O O O O O O O O O O O O O O O O O O d O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 d 0 0 O - • CO r- OP 00 O Ur O on N N VD N ri l0 OD r- O N ('1 141 111 r'1 ri lD el O O O ri VD O N L- Vr In a1 ul rn O M h ri Vr ri O Ch ('1 Vr r- O Ln O O d In O VD l0 O O O O ri M V O OD O u1 ri N LO ri Ln r 9 CO r - O M ON O Ur V' 1/40 N O N N r - Vr OD ul 01 O Vr r - Ch O l0 O M 01 Ur O L ` O O r'1 ul VD M Ur OD O N Ln V' O N O ul N O Ln ((5(0(0(04(5(0(0 r 1.0 CO O O O O ri r-1 N N N ('1 rl V+ Ur Ur Ln Lo Ur 1.0 VD V0 VD vp O L- (0 C` N- N N N 61 O 61 OD 61 N DD O O ri ri l0 Ln l0 N Ul VD OD 01 N N O TV V• d ul N O O 01 V \ \ \ \ \ \ \ Ol 01 ri ri ri ri r( ri ri ri rl ri r1 r1 ri ri r1 ri ri ri ri ri .1 ri ri ri ri ri ri ri ri ri ri N ri ri ri ri ri N N N N N N N rl 01 rl r'1 Ur Ln Ln Ln VD r- co W 00 r1 rl al r-1 �." t., Z Z Z [: V' rl N 01 ON C0 N VD 003 d ri r7 el ul Ln r1 V' r- ( N N OD '.0 O r-f O O 10 01 TV O rl TV O ON O 01 r-1 Vr O■ rl O Vr 01 ul Ln 10 rn V' N 01 ri dr N ri M N N VD O Vr O i 1 1 O on O O O ri 10 CO N O N O ON OO l N N C O Ln rl l0 N N N N r1 00 N 00 N O VD Vr V7 (1 ri ri ('1 V' V TV N 01 oa ul cr N O O CO 1/40 Vr rn N ri O O\ O N r- lD ul ul V' on m N N ri ri O O LO 0l Vr ri OD V. ri m L` V. ri OD l0 Ur ri rn N VD dr N ri O OD N on Vr N ri O 0l Ol r- VD on Ur cr el N ri C Vr Vr ('1 M r'1 r'1 m M N N N N N N N N ri r-1 ri ri ri rl ri ri r-1 ,-1 ri ri r-1 ri rl ri 01 OD OD N N S L' l0 l0 VD VD Ln Ln Ln ul Cr Ur Vr Vr Vr Vr Vr r'1 r'1 f'1 r'1 r1 M M N N N N N N N N N N C Ol Lfl N r- N Vr r•1 01 N OD 0l O Ur N VD O 0l N O r- O Ln N 01 l0 M ri Cn LO VP N O Ol r - ul Vr el N N N O O lD ri O 1D Vr 01 co l0 N d VD O sr N en ri O OD Ur N d 01 N N ri V) U rn N Vr Vr r'1 rl rn rn N N N N N ri ri r1 ri ri r1 rl ri ri rl O1 01 d N N VO LO VD l0 l0 ul on V Vr Vr cr V r'1 VI f'1 en N N N N r♦ ri ri ri ON O 00 OD lD Ln Vr dr sr ('1 ('1 m N O O O O O O O O C Vr ri N ('l 01 ul ri 4 rl 01 ul r 4 (- r'1 O lD N OD Ur O VD N c0 Vr O l0 N 01 10 ri (- on O> 111 ri 4- ('1 01 Ln ri r- Vr O l0 N 00 cr O VD N OD Vr O lD ('1 61 Lf1 ri r M 01 11) ri N r'1 Ch Ln N CO V O V N on rl Vr Vr Ln lD lD r` L— co 61 Ol O ri r1 N N on Vr V. Ln Ln LO r [` CO O 01 O O ri rl N r'1 ('1 Ur Tr Ln VD 1/40 r" CO CO Ol 01 CD ri rl N N m Cr VP Ln Ln VD CO CO 61 O O ri ri N f') rn Tr In V N N N N N N N N N N N N N M r'1 ('1 r'1 ('1 0 ' 1 rn M f'1 M r'1 0) to (•1 01 ('l TV V' Vr V' Vr Ur V. Ur Vr V' Vr Vr Vr Vr Cr Vr Vr Ln ul N Ln Ln Ln In Ln In L(1 ul ul ul Lo In ul l0 VD VD 1.0 l0 l0 ■7 lO VD V O O O O O O O O O O O O O O O d CD 0 0 0 0 0 0 0 0 0 0 0 0 0 CD 0 0 0 0 0 0 0 0 0 0 0 .O O O O O O O O O O O O O O O O O O O O O O O O O O O O O C O O O O O O O O O O O O O O O O O O O O O O O O O O 0 O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O d O 0 0 0 0 0 0 0 0 0 0 C 1 0.0662 0 201 n/a • Fail 0.0668 0 196 n/a Fail 0.0674 0 194 n/a Fail 0.0680 0 186 n/a Fail 0.0686 0 177 n/a Fail 0.0692 0 170 n/a Fail 0.0698 0 161 n/a Fail 0.0704 0 156 n/a Fail I The development has an increase in flow durations from 1/2 predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The Development Has an increase in flow durations for more than 50% of the flows from the 2 year to the 50 year flow. • I Water Quality BMP Flow and Volume. On -line facility volume: 0 acre -feet On -line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. I Off -line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. program and accompanying documentation as provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. AQUA TERRA Consultants and the Washington State I Department of Ecology disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall AQUA TERRA Consultants and /or the Washington State Department of Ecology be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the user of, or inability to use this program even if AQUA TERRA Consultants or the Washington State Department of Ecology has been I advised of the possibility of such damages. .EAR ( FLOW Is) 100 080 50 a .07014 t 25 . 0601 10 F .046 Yearly Peaks for Predeveloped YEAR :1 FLOW (cfs) 100 . 1561 50 . 1450 25 . 1337 10 .1181 .1052 Yearly Peaks for developed W/O Pond YEAR ;FLOW (cfs) 104 .137 50 .1258 . 10 ,0980 5 ; .4854 Yearly Peaks for Developed W /Pond I 30 40 60 60 70 oCumulative Probability Flow Frequency Chart 0.07 10E -5 10E -4 10E -3 PercentLxceeding 4edevelopod Developed with Facility Duration Graph 1 1 1 1 1 1 1 1 Project Name: Site Address: City Report Date : Gage Data Start . Data End Precip Scale: WESTERN WASHINGTON H�OLOGY MODEL V2 11 �� 8"6 h "�'rR.. - kV Ti '1/431'4 °°a '��w PROJECT I PREDEVELOPED LAND USE Basin : Basin 1 Flows To : Point of Compliance GroundWater: No I Land Use Acres TILL FOREST: 0.578 SATURATED FOREST: 0.178 I DEVELOPED LAND USE Basin Basin 2 Flows To Pond 6 I GroundWater: No default 3727 S. 126th St. Tukwila 11/8/2005 Seatac 1948 1998 1.00 Land Use Acres IMPERVIOUS: 0.167 Basin Basin 3 Flows To : Point of Compliance GroundWater: No Land Use Acres I TILL FOREST: 0.28 SATURATED FOREST: 0.178 IMPERVIOUS: 0.131 I RCHRES (POND) INFORMATION Pond Name: Pond 6 Pond Type: Trapezoidal Pond Pond Flows to : Basin 3 Pond Rain / Evap is not activated. • Dimensions Depth: 0.083ft. D Bottom Length: 182ft. Bottom Width : 20ft. Side slope 1: 0 To 1 Side slope 2: 0 To 1 Side slope 3: 0 To 1 Side slope 4: 0 To 1 Volume at Riser Head: D Discharge Structure Riser Height: 0.04 ft. 0.003 acre -ft. Riser Diameter: 100 in. • • Pond Hydraulic Table Stage(ft) Area(acr). Volume(acr - ft) Dechrg(cfs) Infilt(cfs) 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016 0.017 0.018 0.018 0,019 0.020 0.021 0.022 0.023 0.024 0.025 0.026 0.027 0.028 0.029 0.030 0.030 0.031 0.032 0.033 0.034 0.035 0.036 0.037 0.038 0.039 0.040 0.041 0.042 0.042 0.043 0.044 0.045 0.046 0.047 0.048 0.049 0.050 0.051 0.052 0.053 0.053 0.054 0.055 0.056 0.057 0.058 0.059 0.060 0.061 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.084 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.005 0.010 0.016 0.023 0.030 0.039 0.048 0.058 0.068 0.079 0.090 0.102 0.114 0.127 0.140 0.154 0.168 0.183 0.198 0.213 0,229 0.245 0.000 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 0.169 1 I 1 3.062 0.084 0.005 •0.261 0.169 3.063 0.084 0.005 0.278 0.169 3.064 0.084 0.005 0.295 0.169 3.065 0.084 0.005 0.312 0.169 3.065 0.084 0.005 0.330 0.169 0.066 0.084 0.006 0.348 0.169 0.067 0.084 0.006 0.367 0.169 0.068 0.084 0.006 0.385 0.169 1 0.069 0.084 0.006 0.404 0.169 0.070 0.084 0.006 0.424 0.169 0.071 0.084 0.006 0.443 0.169 0.072 0.084 0.006 0.463 0.169 I 0.073 0.084 0.006 0.483 0.169 0.074 0.084 0.006 0.504 0.169 0.075 0.084 0.006 0.525 0.169 1 0.076 0.084 0.006 0.546 0.169 0.077 0.084 0.006 0.567 0.169 0.077 0.084 0.006 0.589 0.169 0.078 0.084 0.007 0.610 0.169 1 0.079 0.084 0.007 0.633 0.169 0.080 0.084 0.007 0.655 0.169 0.081 0.084 0.007 0.678 0.169 0.082 0.084 0.007 0.701 0.169 1 0.083 0.084 0.007 0.724 0.169 ANALYSIS RESULTS Flow Frequency Return Periods for Predeveloped 1 Return Period Flow(cfs) 2 year 0.020581 5 year 0.035641 1 10 year 0.04631 25 year 0.060111 50 year 0.070448 100 year 0.080734 1 Flow Frequency Return Periods for Developed Unmitigated Return Period Flow(cfs) 2 year 0.084866 1 5 year 0.105242 10 year 0.118055 25 year 0.133684 1 50 year 0.14501 100 year 0.15612 Flow Frequency Return Periods for Developed Mitigated Return Period Flow(cfs) 2 year 5 year 10 year 25 year 50 year 100 year 0.04269 0.056228 0.065334 0.077034 0.085906 0.094921 Yearly Peaks for Predeveloped and Developed- Mitigated Year Predeveloped Developed 1949 0.022 0.046 1950 0.060 0.090 1951 0.060 0.070 1952 0.018 0.034 1953 0.010 0.031 1954 0.023 0.043 1955 0.042 0.062 1956 0.037 0.056 1 1957 0.017 0.045 1958 0.026 0.040 • 1959 0.022 A133 1960 0.037 53 1961 0.022 0.045 1962 0.008 0.028 1963 0.013 0.034 1964 0.023 0.050 1965 0.021 0.042 1966 0.013 0.037 1967 0.044 0.064 1968 0.016 0.048 1969 0.027 0.044 1970 0.015 0,037 1971 0.018 0.037 1972 0.051 0.076 1973 0.023 0.041 1974 0.020 0.033 1975 0.027 0.047 1976 0.022 0.040 1977 0.003 0.033 1978 0.011 0.043 1979 0.009 0.043 1980 0.018 0.040 1981 0.012 0.040 1982 0.024 0.062 1983 0.020 0.039 1984 0.018 0.043 1985 0.007 0.029 1986 0.029 0.048 1987 0.032 0.049 1988 0.009 0.024 1989 0.007 0.030 1990 0.045 0.072 1991 0.058 0.074 1992 0.011 0.034 1993 0.013 0.022 1994 0.003 0.024 1995 0.027 0.037 1996 0.061 0.079 1997 0.048 0.061 1998 0.013 0.037 Ranked Yearly Peaks for Predeveloped and Developed- Mitigated Rank Predeveloped Developed 1 0.0604 0.0789 2 0.0598 0.0760 3 0.0582 0.0739 4 0.0508 0.0723 5 0.0484 0.0696 6 0.0453 0.0644 7 0.0444 0.0624 8 0.0422 0.0622 9 0.0372 0.0613 10 0.0370 0.0559 11 0.0321 0.0526 12 0.0289 0.0495 13 0.0270 0.0493 14 0.0269 0.0485 15 0.0267 0.0477 16 0.0261 0.0471 17 0.0243 0.0462 18 0.0229 0.0446 19 0.0228 0.0445 20 0.0228 0.0441 21 0.0224 0.0431 22 0.0223 0.0431 23 0.0218 0.0430 24 0.0216 0.0426 25 0.0210 0.0423 26 0.0202 0.0414 27 0.0202 0.0404 • 129 0.0179 01100 30 0.0177 0. 98 31 0.0176 0.0395 32 0.0169 0.0373 1 33 0.0165 0.0372 34 0.0146 0.0370 35 0.0132 0.0368 36 0.0131 0.0366 1 37 0.0126 0.0343 38 0.0126 0.0336 39 0.0123 0.0335 40 0.0112 0.0333 1 41 0.0105 0.0331 42 0.0097 0.0325 43 0.0087 0.0315 0.0087 0.0298 144 45 0.0078 0.0286 46 0.0072 0.0285 47 0.0072 0.0244 1 F8 0.0032 0.0237 49 0.0029 0.0224 1 1/2 2 year to 50 year Flow(CFS) Predev Final Percentage Pass /Fail 0.0103 2674 6105 228.0 Fail 0.0109 2368 5505 232.0 Fail 1 0.0115 2108 4935 234.0 Fail 0.0121 1895 4484 236.0 Fail 0.0127 1691 4047 239.0 Fail 0.0133 1527 3671 240.0 Fail 1 0.0139 1388 3339 240.0 Fail 0.0145 1261 3010 238.0 Fail 0.0152 1129 2726 241.0 Fail 0.0158 1043 2511 240.0 Fail I 0.0164 963 2319 240.0 Fail 0.0170 885 2125 240.0 Fail 0.0176 823 1934 234.0 Fail 1 0.0182 764 1797 235.0 Fail 0.0188 722 1665 230.0 Fail 0.0194 669 1527 228.0 Fail 0.0200 625 1416 226.0 Fail 1 U.0206 590 1307 221.0 Fail 0.0212 550 1201 218.0 Fail 0.0218 501 1123 224.0 Fail 0.0224 459 1053 229.0 Fail 1 0.0231 425 958 225.0 Fail 0.0237 392 900 229.0 Fail 0.0243 367 831 226.0 Fail 0.0249 337 776 230.0 Fail 1 0.0255 314 729 232.0 Fail 0.0261 293 681 232.0 Fail 6.0267 269 642 238.0 Fail C.0273 242 599 247.0 Fail I 0.0279 228 568 249.0 Fail 0.0285 209 539 257.0 Fail G.0291 190 511 268.0 Fail C.0297 174 483 277.0 Fail I 0.0303 157 456 290.0 Fail 0.0310 146 432 295.0 Fail 0.0316 138 400 289.0 Fail 1 C.0322 129 373 289.0 Fail C.0328 122 357 292.0 Fail C.0334 120 336 280.0 Fail G.0340 107 313 292.0 Fail 1 C.0346 100 299 299.0 Fail 0.0352 96 287 298.0' Fail C.0358 91 275 302.0 Fail C.0364 88 254 288.0 Fail C.0370 76 236 310.0 Fail C.0376 74 221 298.0 Fail • 0.0389 68 204 300. Fail 0.0395 66 197 298. Fail 0.0401 62 190 306.0 Fail 0.0407 60 179 298.0 Fail 0.0413 56 171 305.0 Fail 0.0419 50 160 320.0 Fail 0.0425 44 155 352.0 Fail 0.0431 43 140 325.0 Fail 0.0437 43 132 306.0 Fail 0.0443 41 124 302.0 Fail 0.0449 40 112 280.0 Fail 0.0455 38 109 286.0 Fail 0.0461 34 105 308.0 Fail 0.0467 32 97 303.0 Fail 0.0474 30 91 303.0 Fail 0.0480 29 84 289.0 Fail 0.0486 22 82 372.0 Fail 0.0492 22 79 359.0 Fail 0.0498 21 75 357.0 Fail 0.0504 16 69 431.0 Fail 0.0510 14 68 485.0 Fail 0.0516 13 63 484.0 Fail 0.0522 12 58 483.0 Fail 0.0528 9 53 588.0 Fail 0.0534 8 52 650.0 Fail 0.0540 8 51 637.0 Fail 0.0546 8 49 612.0 Fail 0.0553 6 46 766.0 Fail 0.0559 5 42 839.0 Fail 0.0565 4 40 1000.0 Fail 0.0571 4 39 975.0 Fail 0.0577 4 36 900.0 Fail 0.0583 3 34 1133.0 Fail 0.0589 3 32 1066.0 Fail 0.0595 3 29 966.0 Fail 0.0601 2 29 1450.0 Fail 0.0607 0 28 n/a Fail 0.0613 0 25 n/a Fail 0.0619 0 24 n/a Fail 0.0625 0 20 n/a Fail 0.0632 0 20 n/a Fail 0.0638 0 18 n/a Fail 0.0644 0 17 n/a Fail 0.0650 0 16 n/a Fail 0.0656 0 14 n/a Fail 0.0662 0 13 n/a Fail 0.0668 0 13 n/a Fail 0.0674 0 12 n/a Fail 0.0680 0 12 n/a Fail 0.0686 0 9 n/a Fail 0.0692 0 8 n/a Fail 0.0698 0 7 n/a Fail 0.0704 0 7 n/a Fail The development has an increase in flow durations from 1/2 predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The Development Has an increase in flow durations for more than 50% of the flows from the 2 year to the 50 year flow. Water Quality BMP Flow and Volume. On -line facility volume: 0 acre -feet On -line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. Off -line facility target flow: 0 cfs. Adjusted for 15 min: 0 cfs. program and accompanying documentation as provided 'as -is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. AQUA TERRA Consultants and the Washington State Department of Ecology disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall AQUA TERRA Consultants and /or the Washington State Department of Ecology be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the user of, or inability to use this program even if AQUA TERRA Consultants or the Washington State Department of Ecology has been advised of the possibility of such daes. • Yearly Peaks for Predeveloped YEAR I FL04 106 . 1561 50' .1450 25i 1337 Yearly Peaks for developed W/O Pond YEAR j FLOW (cfs) •00 .137$ . 5(L .1258 25!'- .1139 Yearly Peaks for Developed W /Pond w. e in x o Predeveloped 10E -� x D © Xxxx>axx> bt> ie o ...N TM 1 9O' 20 30 40 50 80 TO 80 90 99 Cumulative Probabili Flow Frequency Chart 0.04 0.07 0.06 10E -5 10E -4 10E -3 10E -2 Percent Exceeding edeveloped Developed with Facility Graph FOR STAFF USE ONLY Sierra Type: P -SP Planner: File Number: L- c' (, _DR ,6 Application Complete (Date: ) Project File Number: ? ( O 6 - OC l Application Incomplete (Date: ) Other File Numbers: LO 6 _v 3 ,S ---- III RECED CITY OF TUKWILA SAY 1 2006 Department of Community Development COMMUNITY nn �� �� 6300 Southcenter Boulevard, Tukwila, WA 98188 DEVELOPMEN 4 ER ISSION Telephone: (206) 431 -3670 FAX (206) 431 -3665 E - mail: tukplan@ci.tukwila.wa.us APPLICATION NAME OF PROJECT/DEVELOPMENT: 5cit i i z t0 g rte T LOCATION OF PROJECT/DEVELOPMENT: Give street address or, if vacant, indicate lot(s), block and subdivision, access street, and nearest intersection. LIST ALL TAX LOT NUMBERS. i2O a7 M( ILA / w i ? bl (4 - ovic : " o ©r 9 , 3 Quarter: 3k) Section: It Township: 23 Range: (This information may be found on your tax statement.) DIRECTOR DEVELOPMENT COORDINATOR : The individual who: • has decision making authority on behalf of the applicant in meetings with City staff, • has full responsibility for identifying and satisfying all relevant and sometimes overlapping development standards, and • is the primary contact with the City, to whom all notices and reports will be sent. Name: 4t}Z©l) Address: �� 3 .12 rn 3 1 / I (n)if 98 /G, 8 Phone: (' 00 B FAX: 2( 2 -44 c 1 ! 8 E -mail: rail- - ./t,C, C,&1 1M,C.Gt•, , Signature: �.s�C Date: HMI I 200 c G\APPHAMLANDUSE.APP\SPD.doc, 09/11/03 Check items . submitted with application Information Required. May be waived in unusual cases, upon ap proval of bath Pilo 'c and pl ann ing APPLICATION MATERIALS: 1. Application Checklist one (1) copy, indicating items submitted with application. 2. Permit Fee (LDR = $200, Other zones = $300). V 3. Written description of the project, the deviation being requested and response to the applicable decision criteria. ZONING CODE PARKING DEVIATION 4. A complete description of the proposed construction relative to parking areas, and all supporting agreements. 5. Dimensional site plan(s) to demonstrate parking area consistent with Zoning Code requirements. 6. Parking studies as needed to demonstrate adequate parking is provided. LANDSCAPE DEVIATION 7. Landscape plan — two (2) copies showing size and species of existing and proposed plant materials, required perimeter landscape types, parking areas, buildings, walkways, transit facilities, property lines, dimensions and area of planting beds and any calculations necessary to demonstrate compliance with review criteria. TREE REGULATION DEVIATION 8. Tree survey showing size and species of existing trees, with trees to be removed and trees to be retained noted (unless request is for use of canopy cover method) 9. Tree replacement calculations per TMC 18.54.130.3 B or canopy cover calculations per TMC 18.54.140 B. 10. Description of the nature of the undue hardship caused by strict compliance with the Tree Regulations, proposed mitigation measures and justification for the deviation from Tree COMPL E APPLICATION ECKLIST The materials listed below must be submitted with your application unless specifically waived in writing by the Public Works Department and the Department of Community Development. Please contact the Department if you feel that certain items are not applicable to your project and should be waived, or should be submitted in a later timely manner for use at the Public Hearing (e.g., revised colored renderings). Application review will not begin until it is determined to be complete. ADDITIONAL MATERIALS MAY BE REQUIRED. The initial application materials allow starting project review and vesting the applicant's rights. However, they in no way limit the City's ability to require additional information as needed to establish consistency with development standards. Department staff are available to answer questions about application materials at 206 - 431 -367c EDEIVED P:\Red Book \SPD_APP.DOC, 04 /15/03 COMPLETE APPLICATION CHECKLIST TABLE 1 MAY 15 2006 CO MMU Check items submitted with applica re formation R id Planning' gay be waive in un usual cases.. ups pproval of both. Public, Works Regulations. SENSITIVE AREA ORDINANCE DEVIATIONS 11. Site Plan — two (2) copies showing all buildings, parking areas, walkways, property lines, planting areas, sensitive areas, their buffers and setbacks. 12. Sensitive area studies and enhancement plans to justify a requested buffer or setback reduction and demonstrate that the reduction will not result in a direct or indirect short-term or long -term adverse impact to the sensitive area. SIGN CODE APPROVAL/DEVIATION 13. Complete "Permanent Sign Permit Application" with all supporting materials and fees ($50). 14. The following information should be given on the plans: North arrow, title, scale and date; Vicinity map showing location and names of adjacent roads; Property lines; Locations of all buildings on site; Dimensioned elevations of building drawn to scale (for wall signs); Elevations, dimensions and materials of proposed sign(s) including advertising copy; Color elevation of proposed sign. CARGO CONTAINER APPROVAL 15. Site plan showing the location of the container(s) in relationship to parking areas, property lines, buildings, streets, trails, landscape areas and setbacks. 16. Description of the proposed screening. 17. Dimensions of proposed cargo container. P.\Red_Book \SPD_APP.DOC, 04/15/03 ❑ Buffers • c. On -site planting of all required replacement trees is not feasible, and the project includes an equivalent contribution in funds and/or labor and materials for off -site tree planting as jointly agreed by the applicant and Director. d. Smaller -sized replacement plants are more suited to the species, site conditions, and to the purposes of this chapter, and are planted in sufficient quantities to meet the intent of this chapter. ❑ Retention and Replacement of Canopy Cover - on undeveloped sites or sites with dense stands of trees, where the cost of identification of individual tree species and sizes is inordinate relative to the project, the Director may allow the applicant to use the tree canopy cover approach outlined below to calculate retention and replacement of trees: 1. The site shall have a minimum canopy cover equal to 20% of the site area, or equal to the existing canopy cover whichever is less. 2. To meet the requirements for site canopy cover, canopy cover may consist of any combination of existing trees and replacement trees. Canopy cover of each new tree shall be calculated at 314 square feet. SENSITIVE AREA ORDINANCE DEVIATIONS ❑ Setbacks. All commercial and industrial developments shall be set back 15 feet and all residential development shall be set back ten feet, measured from the foundation to the buffer's edge. The Director may waive setback requirements when a site plan demonstrates there will be no impacts to the buffer zone. The Director may reduce the standard wetland/watercourse buffers on a case -by -case basis, provided the buffer does not contain slopes 20% or greater. The approved buffer width shall not result in greater than a 50% reduction in width, and the reduced buffer shall not be less than 15 feet for wetlands and ten feet for watercourses. Any buffer reduction proposal must demonstrate to the satisfaction of the Director that it will not result in direct or indirect, short-term or long -term adverse impacts to wetlands or watercourses, and that: 1. The buffer is vegetated and includes an enhancement plan as may be required to improve the buffer function and value; or 2. If there is no significant vegetation in the buffer, a buffer may be reduced only if an enhancement plan is provided. The plan must include using a variety of native vegetation that improves the functional attributes of the buffer and provides additional protection for the wetland or watercourse functions and values. SIGN DEVIATIONS P:\Red_Book\SPD_APP.DOC, 04 /15/03 • ❑ In the single family zone (LDR): signs for all conditional uses and public facilities (TMC 19.32.080); ❑ In multi - family zones where signs face multi- family, commercial and industrial zones: signs of conditionally permitted uses, all public facilities and freestanding signs (TMC 19.32.100). In Commercial and Industrial (TMC 19.32.170) Zones: ❑ Signs of conditionally permitted uses, all public facilities and all free - standing signs, that abut or face single family zones (TMC 19.32.120) and multi - family zones (TMC 19.32.130); ❑ Any multi -tenant office building sign which has over 50% of the total allowed wall sign area (TMC 19.32.140(B)(4)); ❑ A 50% increase in wall sign area for each doubling of the Zoning Code maximum building setback up to 6% of the wall area upon which the sign will be mounted up to a maximum of 500 sq. ft. (TMC 19.32.140(A)(2) and (C)). Shopping Mall business wall signs (TMC 19.32.150(A)): ❑ To allow one wall sign to have more than 50% of the business's total allowable sign area in one sign. ❑ To allow one freestanding sign to have more than 50% of the site's total allowable sign area in one sign. CARGO CONTAINERS Approval criteria for cargo containers to be installed in the LDR, MDR, and HDR zones for institutional uses and in the RC, RCM, TUC or C/LI zones for permitted or conditional uses: ❑ Only two cargo containers will be allowed per lot, maximum length 30 feet. ❑ The container is located to minimize the visual impact to adjacent properties, parks, trails and rights -of -way as determined by the Director. ❑ The cargo container is sufficiently screened from adjacent properties, parks, trails and rights - of -way, as determined by the Director. Screening may be a combination of solid fencing, landscaping, or the placement of the cargo containers behind, between or within buildings. ❑ If located adjacent to a building, the cargo container must be painted to match the building's color. ❑ Cargo containers may not occupy any required off - street parking spaces. ❑ Cargo containers shall meet all setback requirements for the zone. ❑ Outdoor cargo containers may not be refrigerated. ❑ Outdoor cargo containers may not be stacked. P:Uted Book\SPD APP.DOC, 04115/03 Imagery Copyn ht 2008 • '26717 !P HUNDTOFTE /C PROPERTY L06 -036 SAO BUFFER REDUCTION • PBELL Scale: 1" = 100 ry CityGIS5 Copyright ® 2004. All Fits Resery The information contained herein is the prc property d the contributors supplied under Ii may not be reproduced except as licens a gtal Map Products our IfA eie) .ot 8 RECORD OF SURVEY KING COUNTY, WASHINGTON SE 1/4 of the SW 1/4 of Sec. 10, T. 23 N., R. 4 0 i 0 1 0 1 0 1 1 0 0 0 I 0 0 N 8718'57" W 0 0 0 0 0 0 2.0' 0 49.93' MEAS. 50.00' PLAT 0 2.6' 49.93' MEAS. o — 50.00' PLAT 2.3 I Lot 16 MAR 25 2005 DEV E L mUNtry Opm —0 -0— Lot 7 S. 126th St. 0 - - 0 -0 -0-0 N 8718'57 W a--o 49.93' MEAS. 50.00' PLAT Lot 6 1 0 a-0 0 0 0 0 1.2' 49.93' MEAS 50.00' PLAT 0 o- 0- 0-o -o - j Surveyed for BR /E CAMPBELL 3727 S 126th ST. 71/KJNLA, WA. 98168 Scale: 1 " = 20' Date. 3/8/2005 Drown: 7: WK. Revised: Surveyed by SADLER/&ARNARD & ASSOC. INC. 12714 Volley Ave. E., Suite "B" Sumner, Washington 98390 Lot 17 1.7' ---. 1.9' - 2.3' L 49.93' MEAS. 50.00' PLAT Wetland "A" 7,735 sq.ft. Lot 5 / / / / /// / / / // 22.24' A -2 A -1 0 0 0 0-13.- a 8 / I /////////// 1 26.67' 49.93' MEAS. 50.00' PLAT — 0 0 I 0 0 0 t 2.2' Lot 1 0.8' oNier Lot 3 2 9' Lot 2 Lot 4 4.93' v Lot 18 I Lot 19 RECORDER'S CER77F1CA 1E O REPI TRAM REC! IN K RECD RECD OF I RECORDING No. Filed for record this day of ?0 at M. In book of at page at the request of N 0 30 60 54(eitivN rewatihs h R gape, fee 1%0 - ernevSts 44 Sow Stnr haht..d yVoVd PLEASE NOTE: THE STREAM LOCATION DEPICTED ON THIS MAP IS APPROXIMATE, AND DOES NOT REPRESENT AN ACTUAL STREAM SURVEY. APPROXIMATE STREAM LOCATION WAS BASED ON AERIAL PHOTOGRAPHY. LEGEND r /,i WETLAND WETLAND ENHANCEMENT BUFFER ENHANCEMENT PROPOSED BUFFER WITH SPLIT RAIL FENCE 40' BUFFER LINE 80' BUFFER LINE • SENSITIVE AREA SIGN C3® 0 A /p4,1` — ,i, FOB SENSITIVE AREA STUDY AND MITIGATION PLAN HUNDHOFTE PROPERTY - S 126TH STREET Section 10, Township 23 North, Range 4 East, W.M. y , \ ale_ y\ —L 10" ri■m ■ ■■■■■■■■ ■ �� ■ ■ ■�� ■�;� 11 5, 11 1111111111 plimpolmmur "241 �i■i■■■ ■■� Aor A wiiii■�i�� Ar Ai, Air Aejr!i Air Air Air Adr 3.- Air Aiir Atif• Adr Air Air Adr Aior Asir Air A A. Jr Air Air Aisr Adf LOT 2 11" Ex. BLDy EXISTING BLDG HOUSE 2 150' TO R.O.W. EX. YARD -- �_ _air__ i, _alp _ale_ _A1` ai �" —y -• - k C'F� OA3C � Vi PROPOSED BUFFER LINE BUFFER ENHANCEMENT 4,000 SF TYPE 2 WETLAND 7,500 SF TO BE ENHANCED SENSITIVE AREA STUDY ft MITIGATION PLAN MAP HUNDHOFTE PROPERTY - S. 126TH ST. City of Tukwila, Washington Aaron Hundhofte B Brie Campbell 3727 S. 126th St. Tukwila, WA 98168 Sheet 111 Job # 05041 Drawn by: A Bachman Date: March 6, 2006 1 Wei` /A//G/WoHrce , /ha �, �tineation / Mitigation / Restoration / Habitat Creation 1 Permit Assluance 9505 19th Avenue S.E. Suite 106 Everett, Washington 98208 Phone (425) 337 -3174 Fax (425) 337 -3045 E -mail: mailbox @wetlandresources.com Scale 1" = 30 60 PLEASE NOTE: THE STREAM LOCATION DEPICTED ON THIS MAP IS APPROXIMATE, AND DOES NOT REPRESENT AN ACTUAL STREAM SURVEY. APPROXIMATE STREAM LOCATION WAS BASED ON AERIAL PHOTOGRAPHY. LEGEND I�l EEO WETLAND WETLAND ENHANCEMENT BUFFER ENHANCEMENT PROPOSED BUFFER WITH SPLIT RAIL FENCE 40' BUFFER LINE 80' BUFFER LINE • SENSITIVE AREA SIGN )l "PE N C HaN N E `L '1 2 5 iREAm cO s '1 IX. BLDf, A ®® ® ®® btN51 1 !VC. AIWA 1 UUY ANU MI I IUA I 1011 PLAN HUNDHOFTE PROPERTY - S 126TH STREET Section 10, Township 23 North, Range 4 East, W.M. IX. YARD LOT 2 11" HOUSE 2 150' TO R.O.W. EXISTING BLDG aO — HOUSE 1 ®12" 10" s)R'.1__ —11r— yc_ —Ile— —.Ur— — .i. _Ur— ale._ —Ale__ s `s\ ,1. .r, _ —ale—. , �lr_ ale_ _ale_ --Jr— —11` plc_ -- PROPOSED BUFFER LINE BUFFER ENHANCEMENT 4,000 SF TYPE 2 WETLAND 7,500 SF TO BE ENHANCED SENSITIVE AREA STUDY B: MITIGATION PLAN MAP HUNDHOFTE PROPERTY - S. 126TH ST. City of Tukwila, Washington Aaron Hundhofte & Brie Campbell 3727 5. 126th St. Tukwila, WA 98168 Sheet 1/1 Job A 05041 Drawn by: A Bachman Date: March 6, 2006 I Wet/AhdResouroes, /hc (Alen eatbn / Mitigation / 6.4oratlon / Habitat Creation /Permit assistance 9505 19th Avenue S.E. Sulk 106 Everett, Watthgtto 93200 Phone (425) 337-3174 Fax (425) 337 -3045 E -mail: mailbox@wetlandresources.com Scale 1" = 30 60 PLEASE NOTE: THE STREAM LOCATION DEPICTED ON THIS MAP IS APPROXIMATE, AND DOES NOT REPRESENT AN ACTUAL STREAM SURVEY. APPROXIMATE STREAM LOCATION WAS BASED ON AERIAL PHOTOGRAPHY. LEGEND WETLAND WETLAND ENHANCEMENT BUFFER ENHANCEMENT PROPOSED BUFFER WITH SPLIT RAIL FENCE 40' BUFFER LINE 80' BUFFER LINE • SENSITIVE AREA SIGN x TYPE s N EAM-0 , 4 ■ ■■■■1111 ■■■111111■■■■■■ ■■■ ■1111■■■ 1111 ■111111111111111111■ ■■■11■ ■ ■■■■■■■■■■■ ■ ■ ■ ■ ■ ■ ■■ ■1111■■■■■ ■ ■■ ■■■■■■■■■■ /M a■ ■1111■■■■■■■■■■■■■1111■■■1111■ MULM11 1■ ■■■■■■■1111•■■■■■■ ■11■■■■■■■■■■■■■ 7■ ■11 ■1111 ■11 ■ ■11■ ■■11P - ��•.11■■_■■■■ 1■■ ■■■11■■■■■r/ ���i ��i� �/ 711■■■■1111■r' A r A dr A lf Air AS A■■ ••• •� AO Air Alf Arle Ar A, Air Air Air Air A ®® ® ®® CI•I 1 'VC AKCA 1 UUT AIVU MI 1 IUA I RAI PLAIN HUNDHOFTE PROPERTY - S 126TH STREET Section 10, Township 23 North, Range 4 East, W.M. ,o /A� sic_ 10" a l, ,1. 16 IA V. Ur Ay- R � ON (R ` Ov • iONE 44 P�Ett —N.r_ PROPOSED BUFFER LINE BUFFER ENHANCEMENT 4,000 SF TYPE 2 WETLAND 7,500 SF TO BE ENHANCED SENSITIVE AREA STUDY Et MITIGATION PLAN MAP HUNDHOFTE PROPERTY - S 126TH ST. City of Tukwila, Washington Aaron Hundhofte & Brie Campbell 3727 S. 126th St. Tukwila, WA 98168 Sheet 1/1 Job x 05041 Drawn by A Bachman Date: March 6, 2006 1 metes,/ c ,/Oflmeatbn / /Ah4atnn / Restoration / 1Y611at Ovation / Permit Assistance 77 9505 19th Avenue SI. Suite 106 Everett.wadil"{tm 90208 Phone (425) 337-3174 Fax (425) 337 -3045 E -mail: mailbox®wetlandresources.com Project Address: Date transmitted: Stan coordinator: Plan check date: l 2-(' • �vV ❑ DRC review requested 0(64 OCkvi\ :City of Tukwila Department of Community Development LAND USE PERMIT ROUTING FORM TO: ❑ Building ❑ Planning ❑ Public Works E ❑ Lire Dept_ ❑ Police Dept. E P t4 ad fo e- Po ss, b(.e; A ( i Response requested bv: COMMENTS Date response received: „ k l n — ireL4,3 L ), Co� ut ptic AZOV Aasi. w-ekeGI/i►. -ok- n0,41"-o- c.- v, 1,.:21; e, e I tt uJ erg tA16,r.Ar' `1) ittu N.eia,;) ciNwi-uan ” is , t,v4 d [S u(1-(t.r t-..k (,6 1'6 stair oetu Gt., Av-ik, m,1 0 Gb . y, ( c. Net t ► " AP" "I-4 , 4 IJ O: nevt ew h2e feLouslA c eA. Vau- . — Ito di t,P tA9 (A) L 'I v— C -- L) u r.:a o ❑ Plan submittal requested ❑ Plan aooroved Comments prepared bv: File Numbe 3 /r