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Hilliard Wet Season Approval.pdf-fp, i $90 CITY OF EDMONDS GARY HAAKENSON MAYOR 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771-0221 Website: www.dedmonds.wa.us DEVELOPMENT SERVICES DEPARTMENT Planning • Building • Engineering February 24, 2009 Ron and Susan Hilliard 2083123 rd Avenue W Lynnwood, WA 98036 RE: Request to perform groundwork during wet season 15515 75d' Place West, Edmonds Building Permit 2008-0117 Dear Mr. and Mrs. Hilliard, The City received the written request from your Geotechnical Engineer to perforin additional groundwork during the wet season (ECDC 19.10.010), specifically to install underground utilities and install the Redi-Rock retaining wall at the north portion of the property. The City's Geotechnical Consultant conducted a peer review of the request and found it acceptable with conditions, and I concur with that determination. These conditions are set forth in the 3`d paragraph of the attached Technical Memorandum by Landau Associates dated February 23, 2009. Conditions of approval: • The Geotechnical Engineer must approve the time period when the proposed groundwork will be done. • The planned groundwork must not occur during periods of rainfall. + The Geotechnical Engineer must provide special inspection of the retaining wall construction, including drainage and backfill, and provide reports to the City. • Provide compaction reports for backfill of all utility work in the right of way and driveway areas. • Weekly monitoring and reporting from the Geotechnical Engineer of storm water best management practices must continue and reports provided to the City on a weekly basis. • Contractor shall follow all recommendations of the Geotechnical Engineer. Should you have any questions, please contact me at 425-771-0220. Ann Bullis, CBO Building Official cc: Steve Barnes, Cornerstone Architecture • Incorporated August 11, 1890 • Sister City - Hekinan, Japan LANDAU 14 ASSOCIATES TECHNICALMEMORANDUM EWRONMEIM I GEOT=:H A INAIR7ALM01ME5 TO: Ann Bullis, Building Official City of Edmonds Development Services De artment, Building Division FROM: Dennis R. Stettler, P.E., Colin Turnb4llG. DATE: February 23, 2009 RE: DRY SEASON EARTHWORK EXTENSION GEOTECHNICAL PEER REVIEW PERMIT No. BLD20080117 HiLLIARD SM —15515 75 TR PLACE WEST EDImIoNDs, WASHINGTON This technical memorandum provides our geotechnical peer review comments for a requested dry season earthwork construction extension. Construction of the residence is currently underway. The project is located within the Earth Subsidence and Landslide Hazard Area (ESLHA) of North Edmonds. Earthwork in the ESL14A during the winter season between October 1 to April 30 is restricted. The Building Official may consider a request, supported by the owner's geotechnical consultant, for earthwork to continue during this tirne period. The Building Official considers such factors as the type and extent of construction, location, duration, construction approach, monitoring, and other factors in deciding whether to grant approval of earthwork construction during the winter season. Cornerstone Geotechnical, Inc. has provided a letter to the City of Edmonds (City) dated February 11, 2009 requesting a dry season extension in order to complete certain final stages of site construction. The planned activities include a retaining wall from the northwest corner of the house to the northwest corner of the property and tie-in of underground utilities to existing utilities in 75`t' Place West. Cornerstone Geotechnical, Inc. describes the extent of the planned construction and the planned construction approach in their letter. We understand that Cornerstone Geotechnical, Inc. has been providing weekly monitoring and reporting in accordance with the building permit regarding stormwater best management practices. In our opinion, the requested dry season earthwork extension is reasonable, given the extent of the planned construction and the approach to the construction as outlined in Cornerstone Geotechnical's letter. We concur that the planned earthwork should not occur during periods of rainfall. Any backfill and compaction of utility trenches within public right-of-way must be completed in accordance with City requirements. We recommend that Cornerstone Geotechnical, Inc. provide special inspection services for the earthwork and retaining wall construction, including retaining wall drainage provisions. We also recommend that weekly monitoring and reporting of stormwater best management practices continue, 130 2nd Avenue South + Edmonds, WA 98020 + (425) 778-0907 = fax (425) 778-6409 e www,landauinc.com This technical memorandum has been prepared for use by the City in evaluating the adequacy and appropriateness of the request for a dry weather earthwork extension related to the construction of the Hilliard single family residence at 15515 75`x' Place West. The focus of this review was the geotechnical aspects of the request. The purpose of the review was to assess the appropriateness of the request for compliance with City requirements contained in ECDC 23.80 and ECDC 19.10 and conformance with conventionally accepted geotechnical engineering practices. This geotechnical peer review by landau Associates does not lessen the requirements for the applicant's geotechnical consultant, and other design professionals, to monitor site conditions during construction. We appreciate this opportunity to be of service to the City. Please contact us if you have any questions or if we may be of further service. DRSICBT/rgm 2M/09 k Edmdatakpmjects107411441FileRmlRkOryWeatherGeotPeerReview2_tmtm.doc LP.N©Au AssoclATEs 2 Cornerstone to Geotechnical, Inc. Consulting Geotechnical Engineers & Geologists February 11, 2009 Mr. Ron Hilliard 6608 - 216t' Street SW, Suite 304 Mountlake Terrace, WA 98043 Dry Season Extension Request - Retaining Wall and Utilities Ron Hilliard Residence 15515 - 75t' Place West Edmonds, Washington CG File No. 2212 Building Permit # 2008-0117 Dear Mr. Hilliard: FEB 13 2009 DAG p OF SERV $ cTR. We have prepared this letter in support of a dry season extension for the planned construction of a retaining wall and installation of utilities at your project located at 15515 - 750' Place West in Edmonds, Washington. The site has been designated an environmentally critical area due to its location within the Meadowdale landslide complex. Final stages of the project consist of construction of a new retaining wall from the northwest corner of the house to the northwest corner of the property and tie-in of underground utilities to existing utilities within 75`3' Place West. The wall will consist of a Redi-Rock concrete gravity wall. Granular material is planned to be used for backfill behind the retaining wall. This material will help minimize tracking off-site and erosion. The utility trench is located within yard areas and will not support concrete slabs or other structures. We discussed the trenchwork, and the contractor informed us he plans to cover excavated material with plastic until use as backfill. We recommended compacting the trench material as best as possible to minimize future trench settlements. The work should not be completed during periods of rainfall. Any water within the trench should be removed prior to placing backfill. Gravels or cobbles should not be placed 17625 -130th Avenue NE, C102, Woodinville, WA 98072 ■ Phone: 425-844-1977 • Pax: 425-844-1987 Dry Season Extension Request for Retaining Wall and Utilities Hilliard Residence Edmonds, Washington Building Permit # 2008-0117 February 11, 2009 CG File No. 2212 Page 2 against the utility pipes. If the areas are covered with plastic during rainy weather and during times of no construction activity, we do not consider these items as significant earthwork efforts. The site has currently been stabilized by installation of Best Management Practices (BMP's) throughout the site where needed. We have evaluated these BMP's and reported the results in field reports on a weekly basis during the wet season grading period. We plan to continue to evaluate effectiveness of the BMP's during weekly onsite visits for earthwork that will take place during the wet season. It is our opinion that using the current BMP's and following those recommended in this letter, a grading extension would not create significant additional erosion and that the potential of erosion can be controlled by maintaining the BMP's. Cornerstone Geotechnical, Inc. Dry Season Extension Request for Retaining Wall and Utilities Hilliard Residence Edmonds, Washington Building Permit # 2008-0117 February 11, 2009 CG File No. 2212 Page 3 We trust that this letter meets your needs at this time. If you have any questions or need farther clarification, please call. Sincerely, Cornerstone Geotechnical, Inc. f: Jeff ale Proj ect Manager aIn(oq Charles P. Couvrette, PE Principal Three Copies Submitted JRW:CPC:am cc: City of Edmonds — one copy Mr. Steve Barnes, Cornerstone Architectural Group — one copy Cornerstone Geotechnical, Inc.