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geotech peer review.pdf Geotechnical Engineering Study, Proposed Two Residences, 1020 Bell Street, Edmonds, Washington prepared by Geotech Consultants, Inc., dated November 2, 2005. The report is signed and sealed by James H. Strange, Jr., P.E. Environmentally Critical Areas Study & Buffer Mitigation Plan for Gaenz 1020 Bell Street, prepared by ACRE Environmental Consulting, LLC, dated September 10, 2015. The report is signed by Louis Emenhiser. The preceding documents comprise the majority of required application submittals identified in Section 19.10.030 of the ECDC. However, we found the following deficiencies as required by the ECDC: A tree cutting/land clearing plan, or a letter or a report stamped by an appropriate licensed design professional, with sufficient information or data to demonstrate why this item is inapplicable. An affidavit to verify and document that a notice of permit submittal application has been posted conspicuously at the subject property in accordance with ECDC 20.03.002. The affidavit should be notarized. Storm drainage calculations are not included. The sections below provide our specific geotechnical peer review comments related to the submitted documents. RR EVIEW OF EPORTS The geotechnical report provides a good discussion of site conditions and risks, and generally provides geotechnical recommendations appropriate for design. The report appears to adequately document existing site conditions based upon field reconnaissance and subsurface explorations, and acknowledges the presence of steep slopes on the property and addresses these issues in the form of geotechnical recommendations for the construction of drilled pier foundations, retaining walls, slabs on grade, excavations and slopes, temporary shoring, drainage, and earthwork. The geotechnical report includes recommended seismic design considerations based on the 2003 International Building Code (IBC). We recommend that the geotechnical report be revised or a supplementary letter submitted that provides updated seismic design criteria, including peak ground acceleration (PGA) based on the 2012 IBC. The slope consultation letter provides a good evaluation of the slope stability for both the current and proposed conditions and adequately addresses the feasibility of construction and concludes that the proposed construction will not increase the threat of geologic hazard to adjacent properties beyond current conditions in accordance with ECDC 23.80. The letter also provides updated foundation recommendations and provides geotechnical design parameters for conventional continuous or spread footings on a tiered foundation system allowing the structures to day light into the slope. The slope consultation letter references that the proposed development meets the criteria in ECDC 23.80.060 and 23.80.070 based on the provided LA ANDAU SSOCIATES 11/5/15 P:\\074\\185\\R\\PeerReview_tm.docx 2 slope stability analysis. However, the factor of safety (FOS) for slope stability of the proposed condition under seismic conditions is 1.075, which is less than the minimum FOS stated in ECDC 23.80.70 of 1.2. Additionally we recommend that the slope consultation letter be appended to include a discussion on minimum setbacks and buffers, or reductions of, as a result of the slope stability analysis. We also recommend that the slope consultation letter be appended or a supplementary letter submitted that offers a discussion of how the site meets the definition of a geologically hazardous area as defined in ECDC 23.80.020. Detailed review of the Environmentally Critical Areas Study & Buffer Mitigation Plan was not included in Landau Associates scope of work (confirmed via email from Linda Thornquist, City of Edmonds, dated October 24, 2015). However, a cursory review of the document was performed and the report appears to address the environmentally critical areas within the proposed construction area in accordance with ECDC 23.40, 23.50, and 23.90. CP IVIL LANS The civil engineering plans appear to include the necessary details for TESC as shown on the SWPPP, grading, drainage, and utility plans. Provisions for foundation drainage are included in the architectural and structural plans. An addition to the civil plans should include fill/soil stockpile limitation provisions and slope protection plans, in accordance with ECDC 19.10.030. The civil plans should be revised to reflect such provisions, including specific location(s) for stockpiling, height restrictions on stockpiles, and guidelines for protection and maintenance of stockpiled fill/soil. Additionally, existing grade contours are shown at 5-foot intervals; the existing and proposed site grades should be shown at 2-foot intervals in accordance with ECDC 19.10.030. We also recommend that the civil plans include notes that explain the ECDC limitations on site access and special inspection requirements for TESC between October 1 st and April 30 th. The contractor may not be aware of the site access restrictions and special inspection requirements unless this is explicitly stated on the civil plans. ASP RCHITECTURAL AND TRUCTURAL LANS For 1024 Bell Street, the architectural plan Sheet A2.0 All concrete footings shall bear on undisturbed soil, with a minimum soil bearing capacity of 1,500 psf. firm undisturbed soil, bearing capacity of 2,000 psfslope consultation letter recommends an allowable bearing capacity of 2,500 psf on undisturbed soils. The allowable bearing capacity for firm, LA ANDAU SSOCIATES 11/5/15 P:\\074\\185\\R\\PeerReview_tm.docx 3 undisturbed soils used in the design of foundations should be confirmed and presented accurately and consistently on both sheets for 1024 Bell Street. The slope consultation letter explains how compaction of in-situ soils or excavation and replacement of unsuitable soils may be performed if loose/unsuitable soils are encountered. These procedures, including compaction criteria, should be incorporated into the plans. Structural fill and its compaction criteria should be specified, as well for both residences. For 1020 Bell Street, the structural sheets included with the submittal are incorrect and for a different address. The structural sheets for 1013 Bell Street should be replaced with the structural sheets for 1020 Bell Street. The Architectural and Structural Plans for both residences are not signed and sealed by the design professionals. TMS/P OPOGRAPHIC AP AND URVEYLAT The topographic map and survey/plat should include the lowest footing elevations of the proposed residences. This information may be included within the sheets we reviewed for this submittal; however, in accordance with ECDC 19.10.030, a separate topographical drawing should be submitted showing proposed grade contours at two-foot intervals and the bottom elevations of proposed footings, including all stepped footing elevations. Additionally, existing grade contours are shown at 5-foot intervals, the existing site grades should be shown at 2-foot intervals in accordance with ECDC 19.10.030. The approximate distances of existing habitable structures on adjacent sites within 50 feet of property lines should be also be included on the topographic map and survey/plat as required by ECDC 19.10.030. The and was confirmed by Landau Associates by available aerial photography. Setbacks or buffers are not provided on the topographic map and site survey/plat. The topographic map and site survey are not signed and sealed by the surveyor. RSD EQUIRED TATEMENTS AND ECLARATIONS No statements and declarations from the design professionals as required by the City, as applicable, were included in the submittal package. LA ANDAU SSOCIATES 11/5/15 P:\\074\\185\\R\\PeerReview_tm.docx 4 * * * * * * This technical memorandum has been prepared for use by the City of Edmonds in evaluating the adequacy of permit submittal documents related to the proposed residential structures located at 1020 and 1024 Bell Street. 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 23.40, 23.50, 23.80, 23.90, and ECDC 19.10 and conformance with conventionally accepted geotechnical engineering practices. This geotechnical peer review by Landau Associates does not to serve as t Engineer of Record 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. CE/SZW/rgm LA ANDAU SSOCIATES 11/5/15 P:\\074\\185\\R\\PeerReview_tm.docx 5