APPROVED LANDAU-Keck-Hathaway Residence Supplemental Geotechnical Peer Review Letter 1.19.2022LALANDAU
A S S O C I A T E S
January 19, 2022
City of Edmonds
121 5th Avenue North
Edmonds, WA 98020
Attn: Ms. Christina Wayland, Senior Permit Coordinator, City of Edmonds, Building Division
Transmitted via email to: Christina. Wayland@edmondswa.gov
Re: Supplemental Geotechnical Peer Review
Revised Permit Submittal Package for Keck -Hathaway Residence
Building Permit No. BLD2021-0985
Edmonds, Washington
Landau Associates Project No. 0074210.030.031
Dear Ms. Wayland:
An applicant proposes to construct a single-family residence at 15722 72nd Avenue West in Edmonds,
Washington (site). The proposed building site is located in the North Edmonds earth subsidence and
landslide hazard area.
Landau Associates, Inc. (Landau) previously reviewed the applicant's permit submittal package and
summarized its findings in a letter, dated September 10, 2021. The applicant's design consultants have
prepared a revised permit submittal, based on Landau's initial review comments.
At the City of Edmonds' (City) request, Landau has reviewed the revised permit submittal. The review
was completed in accordance with the scope outlined in Task Order No. 21-03 of the 2021 On -Call
Geotechnical Engineering Services Agreement between the City and Landau.
Landau reviewed geotechnical portions of the following documents for compliance with Chapters
19.10 and 23.80 of the Edmonds Community Development Code (ECDC):
• CG Engineering. 2021. Civil Plan. Revised December 3.
• Geotech Consultants, Inc. 2021. Project Update: Proposed Single -Family Residence, 15722 —
72nd Avenue West, Edmonds, Washington. December 15.
• LDC, Inc. 2021. Boundary and Topographic Survey. Revised November 10.
Landau's initial review comments are reproduced below in italics. The comments are followed by a
brief assessment of the applicant's response:
• Review Comment: As noted in Landau's July 26, 2021 completeness review letter, LDC, Inc.'s
topographic survey does not identify the approximate distance between the site boundary and
an existing residence to the north, as required by ECDC 19.10.030. Landau recommends that
the topographic survey is updated to include this information.
RECEIVED
Jan 19 2022
DEPARTMENT
155 NE 100th St, Ste 302 • Seattle, WA 98125 • 206.631.8680 • www.landauinc.com
Keck -Hathaway Residence — Geotechnical Review Services
Landau Associates
Response: LDC, Inc.'s updated topographic survey identifies the approximate distance (15
feet) between the site boundary and the existing residence to the north. In Landau's opinion,
this review comment has been adequately addressed.
Review Comment: The civil plan prepared by CG Engineering shows the proposed location of
stockpiled materials, however, the plan does not include provisions for the height, protection,
and maintenance of the stockpile, as required by ECDC 19.10.030. Landau recommends that
the civil plan is updated to include this information.
Response: CG Engineering has updated its civil plan to include the maximum height of
stockpiled materials (5 feet) and provisions for stockpile protection and maintenance,
including "nets and blankets (BMP C122) and/or plastic coverings (BMP C123) to protect all
exposed soil slope during construction activities." In Landau's opinion, this review comment
has been adequately addressed.
Review Comment: It is unclear which edition of the International Building Code (IBC) was used
to develop the seismic design recommendations in Geotech Consultants, Inc.'s (GCI) 2013 and
2017 geotechnical engineering studies.
With the adoption of the 20181BC, seismic design parameters for the design -level earthquake
changed significantly. Landau recommends that GCI update the seismic design
recommendations in its geotechnical engineering studies to align with the parameters in the
20181BC. Structural designs, slope stability analyses, building setbacks, and other
recommendations should be updated accordingly.
Response: GCI completed a slope stability analysis in accordance with parameters in the 2018
IBC. The results of the analysis are summarized in the "Seismic Considerations and Stability
Analysis" section of its December 15, 2021 project update. GCI now recommends that the
western edge of the proposed residence is supported by a closely spaced wall. In Landau's
opinion, this review comment has been adequately addressed.
• Review Comment: In its civil plan, CG Engineering does not specify seasonal limitations on site
clearing or grading. Landau recommends adding a note to the civil plan, stating that clearing
activities shall be allowed annually between May 1 and October 1, per ECDC 23.80.070.
Response: CG Engineering updated its civil plan with "Temporary Erosion Control Note 8:
Clearing activities shall be allowed annually between May 1 and October 1, per ECDC
23.80.070." In Landau's opinion, this review comment has been adequately addressed.
This letter has been prepared to facilitate the City of Edmonds' evaluation of permit submittal
documents for the proposed single-family residence at 15722 72nd Avenue West in Edmonds,
Washington. Landau reviewed geotechnical portions of the documents for compliance with Chapters
19.10 and 23.80 of the Edmonds Community Development Code and for conformance with
conventionally accepted geotechnical engineering practices. Landau's peer review does not diminish
the responsibility of the applicant's geotechnical consultant to serve as the project's Geotechnical
Engineer of Record. Furthermore, the applicant's consultants are responsible for preparing a design
suitable for the site conditions.
January 19, 2022
Keck -Hathaway Residence — Geotechnical Review Services
Landau Associates
Closing
If you have questions or comments, please contact Sean Gertz at 206.631.8680 or at
sgertz@landauinc.com.
LANDAU ASSOCIATES, INC.
Tyler Cartwright
Staff EIT
Sean Gertz, PE
Senior Engineer
TGC/SMG/SRW/mcs
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References
Landau. 2021. Geotechnical Peer Review: Permit Submittal Package for Keck -Hathaway Residence,
Building Permit No. BLD2021-0985, Edmonds, Washington. Landau Associates, Inc. September 10.
January 19, 2022