Larsen Residence PeerReview_tm.pdf
Technical Memorandum
TO: Linda Thornquist, Senior Permit Coordinator
City of Edmonds Development Services Department, Building Division
FROM: Sean Gertz, EIT and Steven Wright, PE
DATE: April 30, 2018
RE: Geotechnical Peer Review
Submittal Package for Structural Improvements in a Critical Area
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Larsen Residence 15729 75 Place West
Edmonds, Washington
This technical memorandum summarizes the results of our geotechnical peer review of the permit
submittal package that was submitted to the City of Edmonds (City) for proposed structural
improvements to the above referenced residence, which is located within a critical area in Edmonds,
Washington. The purpose of our geotechnical peer review is to review portions of the submittal
package and assess its compliance with the City development and building permit requirements as
contained in Edmonds Community Development Code (ECDC) Chapter 19.10 for sites designated
within or near the North Edmonds Earth Subsidence and Landslide Hazard Area (ESLHA). This review
also assesses the submittals compliance with the requirements of Chapter 23.80 of the ECDC as
required or noted in Chapter 19.10. This geotechnical peer review was accomplished in accordance
with Task Order No. 18-02 -Call Geotechnical and Environmental Engineering
Services Agreement with the City.
We reviewed the following information forwarded by the City:
Completeness Review Pre-Application Form for Earth Subsidence Landslide Hazard Area
projects, stamped Received March 1, 2018
February 26, 2018
Applicant/Owner Covenant to Notify and Hold Harmless, dated February 26, 2018
Structural Engineer Declaration, prepared by CG Engineering on February 26, 2018
Lead Design Professional Designation and Statement and Geotechnical Hazard
Identification/Declaration, prepared by CG Engineering on February 26, 2018
Geotechnical Hazard Identification/Declaration and Mitigation Statement of Risk from
Geotechnical Engineer, prepared by Nelson Geotechnical Associates, Inc. on March 20, 2018
Applicant/Owner Liability and Landslide Acknowledgment, dated February 26, 2018
Structural Design Calculations (stamped by Structural Engineer), prepared by CG Engineering
on March 1, 2018
Critical Area Determination (CRA20180012), stamped Received March 1, 2018
130 2nd Avenue South Edmonds, Washington 98020 (425) 778-0907
Landau Associates
North Edmonds Earth Subsidence and Landslide Hazard Areas Map with signed signatory
block, dated February 26, 2018
Vicinity Map, prepared by CG Engineering on February 26, 2018
Topographical Map and Survey, prepared by A.S.P.I. Land Surveying and Planning on February
14, 2018
Preliminary Geotechnical Engineering Evaluation (stamped by Geotechnical Engineer),
prepared by Nelson Geotechnical Associates, Inc. on February 28, 2018
Building Construction Plans (stamped by Engineer), prepared by CG Engineering on February
21, 2018.
Based on our review of the information that was submitted, it is our opinion that the geotechnical
report that was prepared and submitted for this project provides a good discussion of site conditions
and risks, and provides geotechnical recommendations that appear to be appropriate for design. In
addition, the report appears to adequately document existing site conditions based upon field
reconnaissance and subsurface explorations, and acknowledges the presence of, and adequately
evaluates, seismic, erosion and landslide hazards on the property.
The submittal package that we reviewed includes the majority of the information in Sections 19.10
and 23.80 of the ECDC that is identified as being required. However, ǞĻ ŅƚǒƓķ ƷŷĻ ŅƚƌƌƚǞźƓŭ
ķĻŅźĭźĻƓĭźĻƭ in the information that was submitted:
The vicinity map does not identify existing conditions such as known landslide masses, debris
flows, or mud flows on or near the site.
The topographic survey does not show distances to existing habitable structures on or near
the site, as required in ECDC 19.10.030(D).
The applicant did not submit a separate topographical drawing showing proposed grade
contours at 2-foot intervals, as required in ECDC 19.10.030(E.7).
The geotechnical report, dated February 28, 2018 by Nelson Geotechnical Associates does not
provide analysis of the rate of retreat of the bluff nor an estimate of the percent risk of
landslide area expansion that recognizes and reflects potential catastrophic events such as
seismic activity or a 100-year storm event, as required in ECDC 19.10.030(H.6) and ECDC
23.80.050(F.2.e).
The geotechnical report, dated February 28, 2018 by Nelson Geotechnical Associates does not
describe public and private sewage disposal systems, as required in ECDC 23.80.050(F.2.c).
The geotechnical report, dated February 28, 2018 by Nelson Geotechnical Associates does not
consider the run-out hazard of landslide debris and/or the impacts of landslide run-out on
downslope properties, as required in ECDC 23.80.050(F.2.f).
The geotechnical report, dated February 28, 2018 by Nelson Geotechnical Associates does not
adequately assess the stability of the slope, as required in ECDC 23.80.050(F.2.g). The
geotechnical engineer should confirm the stability of the slope through modeling or numerical
analysis and present the results in the geotechnical report.
Geotechnical Peer Review
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Larsen Residence 15729 75 Pl W 2 April 30, 2018
Landau Associates
The applicant did not submit documentation of required bonds, frozen funds, or adequate
insurance, as required by ECDC 19.10.030(J).
This technical memorandum has been prepared for use by the City in evaluating the adequacy of
permit submittal documents related to the proposed structural improvements to the residence at
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15729 75 Place West in Edmonds, Washington. 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 19.10, ECDC 23.80, and
conformance with conventionally accepted geotechnical engineering practices. This geotechnical peer
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.
LANDAU ASSOCIATES, INC.
Sean Gertz, EIT
Senior Staff Geotechnical EIT
Steven R. Wright, PE
Principal
SMG/SZW/rgm
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Geotechnical Peer Review
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Larsen Residence 15729 75 Pl W 3 April 30, 2018