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Wet Season Work ok'd under CUP City Letter 11-14-08.pdfloc. 1890 DATE: TO: FROM: M. CITY OF EDMONDS 121 5TH AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 • FAX (425) 771-0221 Website: wwwdedmonds.wa.us DEVELOPMENT SERVICES DEPARTMENT Planning - Building • Engineering . November 14, 2008 Brian and Cindy Isaacson (contact for Lot 2) FAX: 425-778-4499 Amy Ross (contact for Lorian Wood HOA common area) 1611973 d Place West Edmonds, WA 98026 Ann Bullis, Building Official Permit Applications BLD2007-0833 & BLD 2007-0834 Lot 2 Lorian Woods and Adjacent Common Area Request to work during "wet season" GARY HAAKENSON MAYOR The City has received peer review comments from Landau Associates in response to your written request received October 17, 2008 to conduct earthwork during the "wet season" (October I" through April 30th). A copy of these comments is attached for your information. Landau Associates is recommending "... that the applicant be allowed to do site work in the wet season only to the extent that such work would help further stabilize the existing ground surface and provide improved temporary and sedimentation control. Examples of limited site work that could be considered would be placement of mulch or erosion control materials in areas that currently have sparse vegetation and could be subject to further erosion and sedimentation during the wet season, and improvement to existing silt fence or other temporary erosion and sedimentation facilities (including removal of accumulated sediment as appropriate) along the western margin of the site. Other site activities that would disturb the existing ground surface should be deferred until after the wet season. " I concur with this recommendation. Based on this decision the subject permit applications (BLD2007-0833 and 2007-0834) will be issued no sooner than May 1, 2009. I have confirmed with Rob Chave, Planning Manager, that the temporary erosion control work described above can be done under the current Conditional Use Permit for tree cutting and replanting (PLN2006-0104) since the replanting has not yet been done. All work must be done under special inspection and monitoring by the Geotechnical Engineer of Record and field reports submitted to the City Building Division on a weekly basis. The Geotechnical Engineer shall make weekly site visits and also after a "storm Page 1 of 2 • Incorporated August 11, 1890 • Sister City - Hekinan, Japan ............................... . event" (1" or greater precipitation in a 24 hour period) to monitor the condition of the erosion control facilities, and reports shall be provided to the City Building Division. Contact Theresa Umbaugh, Senior Permit Coordinator to schedule a preconstruction meeting on site with the City's Building Inspector and Engineering Inspector. The Geotechnical Engineer of Record and your contractor(s) must be present. Theresa Umbaugh will be contacting you regarding the remaining outstanding items for permit applications BLD2007-0833 and BLD2007-0834 which must be adequately addressed before those permits can be issued in May 2009. cc: Rob Chave, Planning Manager File PLN2006-0104 File BLD2007-0833/BLD2007-0834 Page 2 of 2 LANDAU Assocmm TECHNICAL. MEMORANDUM TO:. Ann Bullis, Building Officialr l ` 'V �;� City of Edmonds Development Services Department, Building Division FROM; Dennis R. Stettler, P.E. (. 2Ar- NOV 14 2008 NG DATE:DATE:N. ovember 12, 200.8UILI RE: GEOTECHNICAL PEER REVIEW FOR EARTH SUBSIDENCE AND. LANDSLIDE HAZARD AREA SUBMITTAL PACKAGE — PLAN REvIEwNo. BLD2007.0833: AND 2007.0834 ISAACSON WET SEASON W©Ric REQiJES ' LOT Z AND ADJACENT COMMON ARE, A LORIAN WOODS EDMONDS, WASHINGTON This technical .memorandum provides our geotechnical peer. review of a request by the: applicant to conduct wet season earthwork. The request for wet season work was submitted to the City of Edmonds (City) for the proposed referenced development that lies within the Earth Subsidence and Landslide. Hazard Area.(ESLHA) of North Edmonds. The purpose of this.geotechnical peer review was to review. the, request for wet season.. work and assess its compliance with 'City development and permit regpirements as contained in Edmonds. Co. tnmunity Development Code (ECDC) Chapters 19.1.0 and 2.3.80. This geotechnical peer review was accornplisbed in accordance with Task Order No. 08-23: of Landau Associates' On -Call Geotechnical Engineering Services Agreement with :the .City. We have received the following information forwarded by the City for review: a Proposed Grading .Plan Construction Sequence,. Plan .Checks 2007-0833 and 3007-0834, Lorian Woods 'Grading and Drainage In"7provements, 16067 — 73rd Place West and Loriall Woods Com mon Area, Edmonds, Washington, letter prepared by Terra Associates, Inc., dated October 14; ?008.; In addition to the: materials forwarded by the City; we also, referred to documents submitted far earlier reviews as documented in our geotechnical peer review. technical memorandums elated December 28, 2006 related to tree clearing and July 22, 2008 and September 8, 2008 related to proposed grading and drainage:for the,:subject project. The City requires that earthwork during the winter season between October 1 and April 30 "be restricted. The purpose of :this ,restriction is to try .to. limit the: potential for damaging disruption to the ground surface., limit erosion and sedimentation during this period, .and to accomplish the work in a season that; facilitates early reestablishment of vegetation for erosion control. Any carthwork within this time period requires approval from both the Geotechnical Engineer. of Record and the City Building Official. The letter from Terra Associates, Inc.. outlines a proposed construction sequence, including hand sewing grass seed, installation of the, northern catch basins and drainage pipes, construction of shallow 130 2nd.Avenue South • Edmonds, WA 98020 a (425) 778-09417 + fax (425) 778-6409 ,, www_Eandauha.com 1 swales, removal of an existing silt fence and accumulated sediment along the western margin of the site, and construction of elements of the northern drainage system. Appropriate collection of seepage and surface water is beneficial to the overall slope stability. However, the process of constructing the proposed drainage improvements on the wet slope during wet weather conditions will also result in damage to existing ground cover and vegetation. This action could potentially increase the potential for surface water infiltration, and make temporary erosion and sedimentation control more difficult. In addition, any disturbed areas cannot be effectively revegetated until the next growing season. In our opinion, the suggestion to hand sow grass seed at this time of year would be ineffective. On the balance, it is our opinion that the proposed actions could present more problems than benefits. As such, we recommend that the proposed installation of the northern drainage system and other site improvements not be allowed until after the current wet season (after April 30, and preferably later in the summer). We suggest that the applicant be allowed to do site work in the wet season only to the extent that such work would help further stabilize the existing ground surface and provide improved temporary erosion and sedimentation control. Examples of limited site work that could be considered would be placement of mulch or erosion control materials in areas that currently have sparse vegetation and could be subject to further erosion and sedimentation during the wet season, and improvement to the existing silt fence or other temporary erosion and sedimentation facilities (including removal of accumulated sediment as appropriate) along the western margin of the site. Other site activities that would disturb the existing ground surface should be deferred until after the wet season. This technical memorandum has been prepared for the exclusive use by the City of Edmonds in .evaluating the adequacy of permit submittal documents related to proposed implementation of portions of the Issacson grading and drainage permit during seasonal wet weather restrictions on the subject property. The focus of this review was the geotechnical aspects of the application. The purpose of the review was to assess the adequacy of the application documents 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 prepare an appropriate design for the site conditions. 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. DRS/rgm 11/13108 4Edmdatalprojects10741136TBaRoom\RkGeotPeerReviewWetseaswt_DRAFlimdoc 2 LANDAU ASSOCIATES TERRA ASSOCIATES Inc. �y RECEIVED Consultants in Geotechnical Engineering, Geology and OCT17 208 Environmental Earth Sciences BUILDINC . DEPRRTME?4T CITY . OF EDMONDS . October 14, 2008 Project T.-840-10 Ms. Ann Bullis I . City of Edmonds 121 5th Avenue North Edmonds, Washington 98020 .Subject: Proposed Grading Plait Construction Sequence Plan Checks 2007-0833 and 2007-0834 Lorian Woods Grading and Drainage Improvements 16007 -.73rd Place West and Lorian Woods Common Area Edmonds, Washington References: 1. Geotechnical Report, Meadowvale Beach, Lots 54 through 57, Project No. T-840-1, prepared by Terra Associates, Inc., dated June 6; 1989 2. Geotechnical Report, Lot 2, Lorian Woods, Project No. T-840-10, prepared by Terra Associates, Inc., dated .September 14, 2005 3. Lorian.Woods.Estates Tree Removal, Forest, and Slope Restoration in Tract "A", Report on Conditions: Plans with Details; Related, Documents, prepared by City Foresters, dated March 4, 2006 4. Land Use Application, for Tree Removal, dated August 2, 2006 5:: Supplemental GeotechnicalConsultation, Tree Removal, and Maintenance, Project No. T-840-10, prepared by Terra Associates; hic., dated August 7, 2006. 6. Geotechnical Report, Lot 2, Lorian Woods,"Project No. T-840-10, prepared by.Terra Associates, hic., dated March 30, 2008 7. Drainage Plans prepared for Brian Isaacson by Western Engineers, dated May 22, 2008 8. Geotechnical Plan Review, Drainage Plan.Review, Project No, T-840.-10, dated May 22' 2008 Dear. Ms. Bullis: This Ietter describes the current planned activities that will occur under the, current permit application for the " proposed Isaacson house. With the end of the growing season and the onset of the wet weather-moratorium'for site work, we .have recommended deferring the following elements of the plan: 1. Placement of the southern elements of the drainage improvements. The. southern drainage ' systern will need to be modified to fit the revised catchment wall recommended by the City of Edmonds. 2. Minor grading/debris removal proposed above the house footprint to remove the accumulated erosion sediments. 3. Replanting of the hillside. 12525 Willows Road, Suite 1.01, Kirkland; Washington9BO34 Phone (425) 821-7777 • Fax (425) 821-4334 - Ms. Agin Bullis October 14, 2008 The work will be deferr=ed until next spring when the next growing season begins and prior to the construction of. the proposed catchment wall.. " We recommend that .the northern storm drainage system shown on the current plans be established. .We are proposing a phased approach. The purpose of this work .is to create an on-site discharge paint for the seepage that is occurring. on the site. This work will consist of placement of catch basins labeled DB -1 and DB -2 along the northern margin of their building .envelope. ` Placement of these catch basins will not interfere with the construction of the proposed house or catchment: wall.. Placement of the catch basins on-site will reduce the amount of seepage that is currently flowing down the eastern edge of the road. The existing swales that were conshucted last fall will .be modified by hand excavations or r using a mini excavator to direct surface runoff and flows to the new catch basins. Any swales.needed east of the proposed,catchinent wall will be hand excavated.. New swales will be no deeper than 18 inches below existing site grades. If weather conditions permit, following or during the installation of the stonn drainage system described above, the northern seepage collection pans and tightlines on the slope will be installed as shown on the plans and described in our report dated May 22, 2008. The bulk of the seepage has been noted as being on the slope above the northeast corner of the building footprint. Due to the end of the growing season, it will likely not be possible to reestablish vegetation in areas disturbed by the placement of the upper seepage, collection zone. The contractor will place .jute mattingor equivalent erosion control mats in areas where the foot traffic damages vegetation. The current erosion control plan.shown on the project plans prepared by Western Engineers will be implemented. Temporary erosion control measures that were established last fall following removal of the trees under. a separate permit will be modified to comply with the plans by Western Engineers. In summary, it is planned to: 1. Arrange a pre -construction meeting with the City of.Edmonds. 2.. Hand sow the grass seed specified on the current plans prepared by Western: Engineers. 3. Establish .the northern catch, basins labeled DB -1 and "DB -2:. Soils excavated 60m these trenches that is not used as backfill will be removed -from the site. .Structural fill within the road right-of-way will be placed in accordance with the referenced geotechnical report. 4. Excavate shallow swales to direct the seepage "and surface runoff from the northernportion of the site to the drainage basins. 5. Remove the existing silt fence. and accumulated sediment along the western margin of the site. The accumulated sediment within about five feet of the curb will be removed with a small excavator working. from the paved area. The accumulated sediment will be removed from the site. No fill will be placed along the margin of the road. Any cut slopes created by .the removal of the accumulate_ d sediment will be trade at a 3:1 or flatter. Disturbed areas will be mulched. Project No T-840-10 Page No. 2 Ms. Anis Bullis October 14, 2008 6. If .weather pennies, install the northern elements of the seepage collection system. A suitable weather window will consist of `a 10 period with no significant stories in the weather forecast. All work east, . uphill;of the proposed catchment wall `will be done with handheld equipment. 7.. Tena.. Associates will make weekly and storm specific site visits to observe the condition of the erosion control facilities. Any deficiencies will be promptly brought to the attention of the Isaacson's, their contractor, and the City of Edmonds.: _Field memos will be submitted to the city on a weekly basis. . 8. Tena Associates will make daily field ,visits during all work involving excavations on-site associated with this letter. We trust this letter is adequate for your current needs. If you have any questions, please call: Sincerely yours, TERRA ASSOCIATES, INC. Charles R. ie, L.E.G. Project Manager` Se Fag�of9 age cc : Brian and Cindy Isaacson Mr. Barry R. Constant, P.E., Western Engineers ,CsgO Mr: Michael O'Brien, AIA Mr. Bill Johnson, JLEC: ►ELE IR;