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AssoctATES
TECHNICAL MEMORANDUM 0MONMENLAL I GCOTFOWCA I WMALRESCARCES
TO: Leonard Yarberry, Building Official
City of Edmonds Development Services Department, Building Division
FROM: Dennis R. Stettler, P.E.
DATE: January 29, 2013
RE: GEOTECHNICAL PEER REVIEW
EARTH SUBSIDENCE AND LANDSLIDE HAZARD AREA — BLD2012-1134
McDONOUGH SFR DETACHED GARAGE -1611.5 75T" PLACE WEST
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 referenced development
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
November 30, 2012). 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 (ECI)C) Chapters 19.10 and 23,80. This
geotechnical peer review was accomplished in accordance with Task Order No. 12-05 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 Phin Set (6 Sheets, including Vicinity Allal) and Project It?fbrin(ition, Plot Plan,
Elevations, Garage Pl(ni, Demils, and Roof Plans prepared lay Robin W. Michel dated
October 15, 2012. Includes Lead Design Professional Designation and Statement by Robin
W. Michel, dated November 11, 2012,
Structiowl Plans (Sheets S7 through S3) prepared by Sound Structural Solutions, dated
November 9, 2012,
Structural Calculation Packets by Sound Structural Solutions (packet date: November 9,
2012), Signed and sealed by Ronald V. Skinner,
Structural Engineer's Disclosure Letter, prepared by Sound Structural Solutions and signed
by Ronald V. Skinner, dated November 9, 2011
• Civil Plan Set — Grading, TESC, & Prolmsed Drng (7 Sheet) prepared by Donna L. Breske,
P.E., dated October 25, 2012.
• Civil Engineer's Disclosure Letter, prepared and signed by Donna L. Breske, P.E., dated
October 30, 2012.
• Geotechnical Evaluation, Proposed Garage, 16115 75"' Place West, Edmonds, Washington.
Report from. Gcospectrurn Consultants, Inc., dated August 28, 2012,
130 2nd Avenue South ® Edmonds, WA 98020 - (425) 778-0907 o fax (425) 778-6409 a www.landaumc,corn
• Hazard Identification and Mitigation Statements, Proposed Garage, 16115 75`" Place West,
Edmonds, Washington. Letter from Geospectrum Consultants, Inc., dated November 12,
2012.
• City of Edmonds Critical Areas Reconnaissance Report, prepared by Gina Coccia, Planner,
City of Edmonds, dated August 14, 2006.
• Plot Plan, dated October 15, 2012.
• Topography Survey for Thomas and Monica McDonough, prepared by C & C Surveying,
dated August 7, 2012.
• Land Clearing and Tree Cutting Plan (statement of no trees to be removed). By Robin W.
Michel dated November 12, 2012.
• Covenant of Notification and Indemnification/Hold Harmless. Assessor's Tax Parcel ID
005131105800900 signed by Thomas and Monica McDonough, dated November 20, 2012.
• North Edmonds Earth Subsidence and Landslide Hazard Areas Map (with property location
noted and signed certification as to property location), by Robin W. Michel, Lead Design
Professional, dated November 12, 2012.
• Applicant/Owner liability and landslide acknowledgement signed by Thomas and Monica
McDonough, dated November 19, 2012.
• Affidavit of Earth Subsidence Landslide Hazard Area Permit Posting. Dated and notarized
November 21, 2012.
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
City ESLHA TESC Requirements). We recommend that the notes be revised accordingly.
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General Note 15 states: "See architectural drawings for perimeter foundation drains." The
architectural drawings do not show the perimeter foundation drains and the details of the foundation
drains as recommended by the geotechnical engineer are not incorporated into the plans. We recommend
that the perimeter foundation drain details be provided on the plans (either architectural or civil).
General Note 15 also states: "Foundation drains shall be independent of other site drain lines and
shall be tightlined to the storm drain system where indicated on the plans." We agree with this
requirement and this requirement is consistent with the recommendations of the geotechnical report. In
the event that the roof drain should become clogged or blocked, it is important that water not be allowed
to back up into the footing drains and inadvertently allow the footing drain to act as an infiltration trench.
However, the civil plans suggest that the roof drain and footing drain come together at the SE corner of
the proposed garage and cross the road in a single PVC pipe. It is not clear that this design provides the
required separation of drainage. Please review the drainage system and call out a separate tightline pipe
or provide other means to maintain separation of drainage flow.
STRUCTURAL AND ARCHITECTURAL PLANS
Some of the recommendations of the geotechnical report have not been explicitly incorporated
into the structural plans .(or alternatively the architectural plans).
• The geotechnical report and the hazard identification and mitigation statements letter
prepared by Geospectrum Consultants recommends that the footings be supported on a zone
of compacted structural fill (e.g., see the first paragraph of page 3 of the November 12, 2012
letter from Geospectrum Consultants). This requirement is not mentioned on the plans.
• The geotechnical report and the November 12, 2012 letter from Geospectrum Consultants
(e.g., see the last paragraph of page 3 of the November 12, 2012 letter) recommends that the
foundations on the west side "be deepened as required to provide a horizontal setback of at
least 8 ft or two footing widths (whichever is greater) from the existing slope surface." It is
not clear that this recommendation has been incorporated into the foundation design.
It has been our experience that the contractor tends to build what is specifically shown on the
plans and simply making a general reference to the geotechnical report is often not sufficient to achieve
the intended result. We recommend that the plans specifically include the requirement for 2 ft of
compacted structural fill beneath the foundations and that a specific bottom of footing elevation be
shown on the drawings for the footings on the west side of the building as recommended by the
geotechnical engineer.
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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 McDonough Garage at 16115 75`" 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 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 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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