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TECHNICAL MEMORANDUM MWAMFWAL I GEOT[CWCAL I NAPJM REsWx ES
TO: Leif Bjorback, Building Official
City of Edmonds Development Services Department, Ppilding Division
FROM: nnis R. Stettler, P.E.
De
DATE: June 4, 2013 0
o i
R GEOTECHNICAL 'REVIEW
SUBMirrAL PACKAGE FOR 1'ARTH SUBSIDENCE AND LANDSLIDE HAZARD AREA
DENT SFR ADDITION — 16330 75"" PLACE Wr.s,r
EDMONDS, WASHINGTON
This technical memorandum provides our geotechnical peer review for the permit submittal
package that was submitted to the City of Edmonds (City) for the proposed addition to the Dent single
family residence (SFR) located within the Earth Subsidence and Landslide Hazard Area (ESLHA) of
North Edmonds. We previously performed a geotechnical completeness review (summarized in a
technical memorandum to the City dated February 25, 2013). The purpose of the current geotechnical
peer review is to review portions of the submittal package and assess its compliance with City
development and building permit requirements as contained in Edmonds Community Development Code
(ECDC) Chapters 19.10 and 23.80. '['his geotechnical peer review was accomplished in accordance with
Task Order No. 12-07 of Landau Associates' On -Call Geotechnical Engineering Services Agreement with
the City.
We have received the following information forwarded by the City for review:
• Architectural P16m Set (Sheets I through 8), prepared by Design Lines, revision dated
February 6. 2013.
• S11-11clurctl Plons (Sheets S'1.1, SL2, S1.3, S2 through S4) prepared by Sound Structural
Solutions, dated February 5, 2013.
• StRICtUral Calculation 11ackets by SOL111CI Structural Solutions (packet date: February 5,
2013). Signed and sealed by Damon S. Fleming,
• LectdDesign and Statement I.efler, prepared by Sound Structural
Solutions and signed by Damon S. Fleming, dated January 9, 2013.
• Structural P'nghieer's Decloration Letter, prepared by Sound Structural SOILItiOnS and
signed by Damon S. Fleming, dated January 9, 2013.
• Civil Plans including Storm Droinuge Plan (I Sheet) and -'S11VPPP/b",rosion onelSe(fimew
Control Plug, Details, cou-1 Notes (I Sheet) prepared by D, R, Strong Consulting
Engineers, dated January 3, 2013.
• DeW Residence � 16330 - 75"'..4ve W (Civil Engineer's Disclosure Leflei), letter prepared
and signed by 1). R. Strong Consulting Engineers, dated January 16, 2013.
Strong 9
130 2nd Avenue South - Edmonds, WA 98020 - (425) 778-0907 - fax (425) 778-6409 - www.landauinc.com
® Geotechnical Engineering Report, Proposed Single Family Residential Addition, 16330
75`r' Place West, Edmonds, Washington. Report prepared by Robinson Noble for Mr. Paul
Dent, dated March 12, 2012.
® Plan Review Letter, Proposed Single Family Residential Addition, 16330 — 75"' Place
West, Edmonds, Washington. Letter to Mr. Paul Dent from Robinson Noble, dated January
8, 2013.
® Revised Plan Review and Mitigation Statement of Risk Letter, Proposed Single Family
Residential Addition, 16330 — 75"' Place West, Edmonds, Washington. Letter to Mr. Paul
Dent from Robinson Noble, dated February 14, 2013.
® Vicinity Map, from Robinson Noble report, dated March 2012.
® Plot Plan, preparer not identified and not dated.
® Topography Survey for Paul Dent, prepared by Western Surveyor, Inc. dated January 7,
2013.
® Tree Cutting Plan (statement of 5 plum trees to be removed). Preparer not identified and
undated.
® Covenant of Notification and Indemnification/Hold Harmless. Assessor's Tax Parcel ID
005131-060-009-00 signed by Paul and Jenelle Dent, dated January 10, 2013.
® North Edmonds Earth Subsidence and Landslide Hazard Areas Map (with property
location noted and signed certification as to property location), by Paul Dent, dated
January, 3, 2013.
® Applicant/Owner liability and landslide acknowledgement signed by Paul and Jenelle
Dent, dated January 10, 2013.
The documents submitted appear to meet the minimum required application submittals identified
in Section 19.10.030 of the Development Code. The following sections provide our specific geotechnical
peer review comments.
GEOTECHNICAL REPORT
The geotechnical report provides a good discussion of site conditions and risks, and 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 occurrence of landsliding within the ELSHA and the risk potential for future landsliding at and in the
vicinity of the subject parcel.
CIVIL PLANS AND STORM DRAINAGE STUDY
Inspection, maintenance, and regular reporting of TESC measures by the Geotechnical Engineer
of Record are required [see the City ESLHA Temporary Erosion and Sediment Control (TESC)
Requirements]. The pre -construction meeting needs to include the Geotechnical Engineer of Record (see
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City ESLHA TESC Requirements). Earthwork activities within the ESLHA are also seasonally
restricted. We recommend that the notes be revised accordingly.
STRUCTURAL AND ARCHITECTURAL PLANS
It has been our experience that the contractor tends to build what is specifically shown on the
plans and simply making reference to the geotechnical report is often not sufficient to achieve the
intended result. We recommend that the plans specifically include the requirement for a 2 ft thickness
of compacted structural fill beneath the foundations and that the zone of compacted fill be shown to
extend a minimum of 2 ft beyond the footings in order to create a III. IV envelope froin the base of the
footings as recommended in the geotechnical report. We also recommend that the footing drains and
associated drainage material as recommended by the geotechnical engineer be specifically shown on
the plans, and that free -draining wall backfill with a footing drain be provided behind all foundation
walls acting as a retaining wall.
REQUIRED STATEMENTS AND DECLARATIONS
We reviewed the submittal package and confirmed that the statements and declarations from the
design professionals as required by the City for development within the ESLHA are included in the
submittal package.
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 addition to the Dent SFR at 16330 75th
Place West. 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 conforinance with conventionally accepted geotechnical
engineering practices. This geotechnical peer review by Landau Associates does not lessen the
requirements for the applicant's geotechnical consultant to serve as the project's Geotechnical 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.
DRS/CTM/rgm
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