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20061222085209.pdfof�'o City of Edmonds ... :3, PLAN REVIEW COMMENTS - BUILDING DIVISION 9 Est. g90 (425) 771-0220 DATE: December 22, 2006 TO: Jim Thomas Fax(425)252-6911 FROM: Jenny Readwin, Plans Exam ne RE: Plan Check # 2006-0654 Project: Oates SFR (ESLHA) Project Address: 7400 158' ST W During re -review of the above noted application, it was found that the following information, corrections, or clarifications are needed. Please redline plans or submit two (2) sets of revised plans/documents (affected sheets only) with a written response to each of the items below to a Permit Coordinator. 1) See attached comments. Please respond to each item in writing.. Geotechnical review of ECDC 19.10 and 23.80 under separate cover. 2) Provide stamped and signed shoring details and calculations. Provide grading plan showing 1:1 slopes and/or temporary shoring as noted in letter dated April 21, 2006 by Dennis Bruce, P.E. Also, have Geotech review the revised plan for compliance with his recommendations. 3) Declaration needs to be on a separate cover sheet. Geotechnical. Declaration and Statement of Risk submitted does not have the correct wording required (see attached for sample wording). 4) ok 5) ok 6) Typical wall section still calls out 16" wide footing. Please revise. Revise foundation plans to match the foundation recommendations specified in the Geotechnical Evaluation Report (page 3) by Dennis Brace, P.E. dated May 17, 2005. 7) ok 8) Geotechnical Engineer of Record referenced City of Edmonds Standard Rockery details. This detail specifically states in the corner that it is not applicable to the ESLHA. Please provide new stamped and signed details and calculations from the Geotechnical Engineer of Record as required in the Rockery Handout. Per our Rockery Handout (attached) all rockeries located in the ESLHA are required to be design consistent to ECDC chapter 23.80 including design calculations stamped and signed by a Washington State Licensed Professional Engineer. Submit details and design calculations for all proposed rockeries and reference detail on the site plan. 9) Provide construction detail for proposed site built shower including shower pan, slope, drain, etc. 1.0) ok 11) ok 12) Still Need. Special inspections are required for the following. Complete the enclosed special inspection agreement signed by the owner, the general contractor and the special inspector and submit to the City for approval prior to issuance. • Start of Work Letter from Geotechnical Engineer of Record • General site monitoring by Geotechnical Engineer of Record • Excavation/Grading/Site Preparation • Soil bearing verification • Temporary Shoring • Structural fill placement and compaction • Rockery/retaining wall construction including drainage • Footing drains and subsurface drainage • Temporary and Final erosion control • Final geotech construction report Page 2 of 2 12/18/2066 13:45 4256498758 GEOGROUPNORTHWEST PAGE 02/06 Geotechnical Egineer, GeologistsCro1Northwest, 7nC• rag) Environmental Scientists December 20, 2006 Project No. G-2384 Ms. Jeannine L. Graf - City Building Official City of Edmonds - Development Services Dept. 121 - 5"' Avenue North Edmonds, WA 98020 Subject: Geotechnical Peer Review of Earth Subsidence Landslide Hazard Area Proposed Oates Residence 7400 - 158'h Street SW Edmonds, Washington Ref.: 1. City of Edmonds Development Services Department letter by Jeannine L. Graf, dated November 20, 2006. 2. City of Edmonds Ordianance #2661 3. City of Edmonds Community Development Code Chapter 19,10 4. "Final Report, Landslide Hazards investigation, Meadowdale Area, Edmonds, Washington, for the City of Edmonds." Roger Lowe and Associates, Inc, October 16, 1979. a. "Report of Geotechnical Consultation for Property Value Appraisals and Assessments in the Meadowdale Area, Edmonds, Washington." GeoEngineers Incorporated, February 28, 1985. (Including Landslide Hazard Map with reduced Landslide Percentage Values) 6. "Geotechnical Investigation For Proposed Single Family Residence, Lot 1 - Block 30, Meadowdale Beach ( 75th Place W. and 158" Street S.W.), Edmonds, Washington." Landau Associates, Inc., July 23, 1985. 7. "Geotechnical Evaluation - Foundation Recommendations, Proposed New Residence, 7,400 (approximate) 15811 St. SW, Edmonds, Washington, Lot No. 1 Block 30, Meadowdale Beach." Dennis M. Bruce, P. E.,- May 17, 2005, 13240 NE 20th Street, Suite 10 - Bellevue, Washiegtan 98005 Phone 425iG49-9757 • FAX 4251649-8758 12/18/2006 13:45 4256498758 GEOGROUPNORTHWEST PAGE 03/06 December 20, 2006 G-2384 Oates Residence Geotechnical Peer Review Page 2 8. "Geotechnical Review and Response, Proposed Oates Single Family Residence, 7400 158` St. W., Edmonds, Washington." Dennis M. Bruce, P.E., October 18, 2006. 9. "Geotechnical Review of Plans - Declaration of Minimal Risk, Proposed Oates Residence, 1400 158 th St. W., Edmonds, WA." Dennis M. Bruce, P.E., April 21, 2006. 10. "Site Plan sheets SP -1 and SP -2, and Architectural Plan Sheets A-1 to A- 11, Proposed New Residence for: Scott & Alice Oates 7400 - 158'h Street SW, Edmonds, WA." Architectural Design Associates, Inc., dated 8-22-06, Stamped by James A. Thomas, AIA. 11. "Structural Plan sheets S-1.0 and S-2.0, Oates Residence." Structural Design Associates, 8-22-06. 12. Drainage and Grading Plans and Vicinity Map, Oates SFR at 7400 - 158th Street SVV, Edmonds, WA. J.C. McDonnell Engineering, P.C., May 4, 2006. 13. City of Edmonds, Task Order, On-call Geotechnical Engineering Services, Order No. 06-01, December 4, 2006. Dear Ms. Graf: In response to the above referenced letter dated November 20, 2006 and the task order dated December 4, 2006 from the City of Edmonds Development Services Department, we have reviewed the geotechnical aspects of the above referenced documents, plans, and City of Edmonds code. Based on our review of the above referenced plan sheets and documents we are of the opinion that the geotechnical reports prepared by Landau and Associates and Dennis Bruce (Ref. 6, 7, 8, 9) adequately address the geotechnical foundation issues at the site. The pians for the site (references 10, 11, and 12) present the architectural, structural and drainage plans for the site. However, a review of geotechnically-related sections of City of Edmonds Ordinance 2661 and ECDC 19.10 indicates that several requirements of the City of Edmonds documents have not been met by the current geotechnical documents and plan sheets. Descriptions of the requirements that have not been met are listed below. GEO Group Northwest, Inc. 12/18/2066 13:45 4256498758 GECGRCUPNORTHWE5T PAGE 84/66 December 20, 2008 G-2384 Oates Residence Geotechnical Peer Review Page 3 The Dennis Bruce documents do not include a description of the entire risk of the geologic hazards at the site with "...scientific clarity...." and did not describe the landslide hazard area applicable to the site defined by Lowe Associates and GeoEngineers as is required by Chapter 19.10.000 and 19.10.020 (D). A review of previous explorations of the site should be included in the geotechnical report as described in the above referenced sections. • A checklist of geotechnical report items is also not included in the permit documents as is required by Chapter 19.10.030(B). • Chapter 19.10.030 also requires that the opinions and recommendations in the geotechnical report should be supported by field observations and literature review, including explanation of both. Because the evaluation involves geologic evaluations and interpretations, it should be approved by a geologist with qualifications as defined by 19,10.20(E). The primary geologic hazard at the site was found by Landau to be at 20 to 50 feet below the ground surface, while the Dennis Bruce test pits extended to only 11 feet below the ground surface. The Dennis Bruce reports need to reference the Landau report to support the opinions and recommendations by Dennis Bruce. • The literature review in the Dennis Bruce report is also incomplete. The Dennis Bruce report notes the condition of soils at the base of proposed excavations to be similar to findings of the Landau report. However, the Dennis Bruce report does not discuss the potential for a sliding surface at 20 to 50 feet below the ground surface that was emphasized in the Landau report consistent with the Lowe Associates and GeoEngineers literature. A discussion of these aspects of the Landau, Lowe and GeoEngineers reports should be included in the Dennis Bruce documents. • The Dennis Bruce documents make a statement of minimal risk of damage and state that the proposed development will not increase the potential for soil movement as is required by Chapter 19.10.040. The Bruce documents state a statistical probability of earth movement within the 25 year period as less than 1 percent due to removal of significant soil weight and an addition of subsurface GEO Group Northwest, Inc. 12/18/2086 13:45 4256498758 GEOGROUPNORTHWEST PAGE 05/06 December 20, 2006 G-2384 Oates Residence Geotechnical Peer Review Page 4 and surface drainage at the site. The Landau report places the 25 year probability at 10 to 30 percent with similar removal of soil and drainage installation resulting in "...a very slight improvement in overall hillside stability." The risks described in the Landau report are acceptable for development based upon definitions provided in Chapter 19.10.020(.1) for "stable." The definition states that, "In the event that any site has an underlying risk of movement based upon deep-seated earth movement or large scale earth failure which is not susceptible of correction by on-site improvements, such hazard shall not render a site proposed for single family residences to be presumed unstable for the purpose of this provision if the risk of probability of earth movement is measured at 30 percent or less within a 25 -year period and this hazard, along with all measures taken to correct it or reduce it are fully disclosed in the covenant required to be executed in accordance with provisions of this chapter, in which case the defined risk may be approved as an acceptable condition." It is our opinion that this site is applicable to this definition in terms of uncorrectable deep-seated earth movement risk, proposed single-family residence, risk probability of 30 percent or less in 25 years, and proposed developments taking all measures to reduce the potential effects of the hazards. The calculation of statistical probability of earth movement by Dennis Bruce should be discussed in detail and it should be apparent that the probability is based on literature of previous explorations, a sufficient exploration by Dennis Bruce:, or both. It is our professional opinion that the above referenced plan sheets and documents generally conform to the geotechnically-related requirements of City of Edmonds Ordinance 2661 and ECDC 19.10 except for the above -noted items. In order to create code compliance, we recommend that the geotechnical documents include a more detailed literature review with detailed descriptions of hazards at the site. We. recommend that the geotechnical engineer of record clearly explain to the owners the acceptance of risk of possible earth movement at the site. Changes to the above documents should be sent to our office for review. Should you have any questions regarding this letter or need additional information, please feel free to call us. GEO Group Northwest, Inc. 12/18/2606 13:45 4256498758 GEOGROUPNORTHWEST PAGE 06106 G-23 December 20, 2006 Pacie 5 Oates Residence Geotechnical Peer Review Pa e 5 Sincerely, GEO GROUP NORTHWEST INC. Ge Wade Geologist William Chang, P.E. Principal Engineer GEO Group Northwest, Inc.