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Fritschen Wet Season Letter.pdf4c.1 9' C11"Y OF EDMONDS 121 5TH AVENUE NORTH ^ E©MONDS, WA 98020 • (425) 771-0220 • FAX (425) 771-0221 Website: www.ci.edrr onds.wa,us DEVELOPMENT SERVICES DEPARTMENT Planning o Building - Engineering October 8, 2009 David Fritschen and. Deborah Stewart 19225 13"}' Drive SE Bethell, WA 98012 RE: Request to perform groundwork during wet season 163 l9 75"' place West, Edmonds Building Permit BLD20090376 Dear Mr. Fritschen and Ms. Stewart, GARY HAAKENSON MAYOR The City received the written request frorn your Geotechnical Engineer to perform additional groundwork during the wet season between October 1" and April 30`x' (ECDC 19.10.010) as outlined in his request dated September 28, 2009, including excavation and removal of soil from the site, construction of a rockery wall, and pin pile foundation construction. The City's Geotechnical Consultant conducted a peer review of the request and found it acceptable as outlined in your Geotechnical Engineer's letter, and I concur with that determination, All aspects of the ground work must be monitored by the Geotechnical Engineer at minimum on a weekly basis (not including additional inspections for required Special Inspections) and immediately following a storm event (F or greater precipitation in a 24 hour period as reported by i OAA) and reports submitted to the City also on a weekly basis, The General Contractor shall follow all recommendations of the Geotechnical Engineer. Should you have any questions, please contact me at 425-771-0220. Sincerely, Ami Bullis, CBO Building Official cc: Erik Anderson, PE, HWA Gcosciences lnc,oaYpor°c°ated c"1ugust 11„ 1890 �: _._ i-:— ., -1-- — r-.- - -- 1ALANDAU ASSOCIATES TECHNICAL MEMORANDUM 'TO: Ann Bullis, Building Official City of Edmonds Development Services Department, Building Division FROM: Dennis R. Stettler, P.E. DATE: October 7, 2009 RE; GEOTECHNICAL PEER RFviENV FOR WE, SEASON EARTHWORK R CQUEST CCTV OF EDMONDS PIAN CiwcK No. 20090376 i(+`.RITSCHEN/STEIVART SFR -16319 75"' PLACE ''WEST EDM.ONDS, WASHINGTON This technical inemorandum provides our geotechnical peer review comments fora requested wet season earthwork request. 'rhe project is located within the Earth Subsidence and Landslide Hazard Area (ESLHA) of North Edmonds. Earthwork in the ESLHA during the winter season between October l 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 time 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. HWA Geosciences, Inc. (HWA) has provided a letter to the City of Edmonds (City) dated September 28, 2009 requesting wet soason earthwork in order to complete site construction. The planned activities include excavation and removal of soil from the site, construction of a rockery wall, and pin pile foundation construction. F1WA provides specific recommendations in their letter to limit the extent of soil exposed at any particular link and maintain the temporary erosion and sedimentation control pleasures on the site. We understand that HWA will be providing monitoring of temporary erosion and sedimentation controlfeatures and performance during construction. In our opinion, the requested wet season earthwork request is reasonable, given the extent of the planned construction and the approach to the construction as outlined in HWA's letter. This technical memorandum has been prepared for use by the City in evaluating the adequacy and appropriateness of the request for a vet weather earthwork request related to the construction of the Fritschen/Stewart single family residence at 16319 75#1' 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 130 2nd Avenue South . Edmonds, WA 98020 • (425) 778-0907 • fax (425) 778-6409 a www.landauinc.com 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. DRSlrgm 1017109 11Edmdatalprojects1oi451385File Rm1R1WeIWeatherGeolPeerReview_lm.doc LANDAU AssocIATES 2 Umbaugh, Theresa From: Dennis Stettler [DStettler a landauinc.com] Sent: Wednesday, October 07, 2009 2:45 PM To: Bullis, Ann Ce: Umbaugh, Theresa Subject: FW: Here is a PDF of the final Fritschen - Stewart Wet Season Tech Memo. A hard copy will also be mailed. today. Ann and "Theresa Attached is our tech memo for the Fritshen/Stewart Wet Season request, Please let us know if we can be of further assistance. Dennis Dennis R. Stettler, Y.E. " Principal Landau Associates, In C. 130 2°d Ave. S, Edmonds, WA 98020 425.778.0907 " fax 425.778.6409 clstettlerCr)landauinc.cona - wwNv.landauine.ccan Email is a sustainable communications tool — please consider this bcfare printing. Notice: This co€nmunication may contain privileged or other confidential information. If you have received it in error, please advise the sender by reply email and immed€atcly delete the message and any attachments without copying or disclosing the contents. Thank you. From: Rhonda Moon Sent: Wednesday, October 07, 2009 2:43 PM To: Dennis Stettler Subject: Here is a PDF of the final Fritschen - Stewart Wet Season Tech Memo. A hard copy will also be mailed today. Rhonda C. Moon " Project Coordinator Landau Associates, Inc. 130 2,,d Ave. S, Edmonds, WA 98020 425,778.0907 " tax 425.778.6409 rgmoon .i?.I }ndauinc.com " www.landauinc.com Email is a sustainable communications tool —please consider this before printing. Notice: This communication may contain privileged or other confidential information. if you have received it in error, please advise the sender by reply email and immediately delete the message and any attachments ~without copying or disclosing the contents. Thank you. 10/7/2009 I IWAGEOSCII NCES INC. U01 September 28, 2009 IOWA Project No. 2003-174-21-1300 TO,: CC: Ann Bullis and Pat Lawler David Fritschen Edmonds Development Services and Deborah Stewart 121 5"' Avenue North 19225 131' Drive SE Edmonds, WA 98020 Bothell, WA 98012 Subject: WINTER SEASON EARTHWORK REQUEST Fritschen/Stewart Property Development 16319 75t" Place West, Edmonds, WA City of Edmonds Plan Check No. 20090376 Dear Anii and Pat: RECEIVED' SEP 2 8 2,9��) DEVRoPmEN"F,9ERV1c1-­,,, 1. �; ]HA is providing geotechnical special inspection services for the above -subject project. We advocate that the site earthwork be permitted to: proceed into the upcoming wet season, in a manner such that the sulaj ect and adjacent properties do not become unstable, and that no sediment leaves the site. To this end, we recommend the following wet season earthwork MM10111043 I All vertical or near vertical excavations should be minimized in extent and duration of exposure. We recommend that the rock -faced gravity retaining walls along the South and cast sides of the grading area be constructed in sections, i.e., excavation, foundation preparation, and rock placement should be completed in sections. Concurrent with site excavations down to final grade these south/east site walls should be constructed. Temporary vertical to near -vertical excavations should not be left exposed to precipitation for more: than 8 hours. If it is not possible to complete a section of rock - faced retaining wall in one day's work shift, the exposed excavation face should be covered with plastic sheeting secured with sandbags on ropes to protect the excavation from exposure to wet weather. 2. All excavations for underground utilities, such as the storm water detention pipe/vaiult,, should be quickly completed and backfilled. Underground utility excavations more than 3 feet deep should not be left open overnight. Efforts should be made to minimize the amount of open excavations in order to minimize erosion hazard. 3. The approximately 1,400 cubic yards of on-site soil that will be excavated is generally very silty/clayey. As such, this material is extremely moisture 1.9730 .- 64th AAcnuc K sensitive and will become difficult or impossible to work- with when Suite 200 Lynnwood, WA 98034 5957 'f'( I: 425,774.0106 Fax 425.n,1,2714 wwwAlwageo.coln September 28, 2009 HWA Project No. 2003-174-21-1300 wet. Tire -mounted equipment should not operate on this exposed silty/clayey soil without a quarry spall construction access path. Excavated material should not be stockpiled on site, but rather loaded directly into dump trucks for offsite disposal. 4. Excavated onsite material should not be re -used as trench or structure backfill. All retaining wall and trench backfill should be comprised of imported, clean and freely - draining sand or gravel, as applicable to the structure being backfilled and/or as specified in the City -approved plans. 5. All TESC provisions must be maintained and, if necessary, replaced or improved upon as construction progresses. In our opinion, the approved TESC plan for the project will be adequate for wet season (winter) site earthwork construction. The underlying objective of the TESC measures is to ensure that no sediment leaves the site, except that which is hauled off via dump truck to an approved soil disposal site. These measures must function effectively in October and November, just the same as they must function in August and September. If at any time any silt fence, catch basin insert, or other measure is observed to be either inadequate or failing, then immediate corrective action should be taken to correct the problem. 6. At the conclusion of each day's work, the site should be protected and stabilized with plastic sheeting, quarry. spalls, and erosion control curtains as required. During each day's site inspection, the HWA geotechnical special inspector will systematically inspect the site for erosion control and soil stability. Any areas identified by the geotechnical inspector as deficient or requiring attention will be brought to the attention of the general contractor (David Fritschen) for corrective action. 7. The pin piles should be installed after the site retaining walls are completed and after the underground utilities are installed. A gravel working surface should be placed so that the pin pile subcontractor is not exposed to the silty/clayey subgrade. 8. Once all of the pin piles are installed, pile caps and grade beams should be promptly formed and poured. After this work is completed, the exposed ground surface should be hydroseeded and/or covered with straw mulch. Provided the above measures are implemented, it is our opinion allowing continued site earthwork during the upcoming winter wet season will not reduce the stability of the subject or adjacent sites, nor increase the risk of sediment leaving the site. 2003-174-21-300 Wet Weather Work Exteision 2 HWA GEOSCIENCES INC. September 28, 2009 HWA Project No. 2003-174-21-1300 We are committed to working with the City of Edmonds to ensure that the work is completed safely, and without any problems. We hope the foregoing is adequate for the City of Edmonds to provide permission to continue with site earthwork and grading. If you require additional information or we may be of further service, please contact the undersigned at (425) 774-0106. Sincerely, HWA GEoSCIENCBS INC. "N Erik O. Andersen, P.E. Senior Geotechnical Engineer, Vice President 2003-174-21-300 Wet Weather Work Extension 3 HWA GEoSciENCES INC.