Engineering & Planning Civil Comments 3 - PLN20180033.pdfOF EDV0 CITY OF EDMONDS
CIVIL PLAN REVIEW COMMENTS
ENGINEERING DIVISION
6'st 1 g90 (425) 771-0220
City Website: www.edmondswa.gov
DATE: September 30, 2019
TO: Greg Guillen
Grego@cgengineering.com
FROM: Jeanie McConnell, Engineering Program Manager
jeanie.mcconnell@edmondswa.gov
RE: Subdivision File 4: PLN20180033
Project: Larsen 3-lot Short Plat
Project Address: 15729 75th PI W
During review of the above noted application, it was found that the following information,
corrections, or clarifications are needed. Please redline plans or submit two (2) sets of revised
plans/documents with a written response to each of the items below to an engineering technician.
Resubmittals can be made at the Development Services Department on the 2nd floor of City Hall.
Permit Center hours are M, T, Th & F from 8am-4:30pm and on Wednesdays from 8:30am-noon.
City of Edmonds handouts, standard details and development code can be referenced on the City
website.
Comments 1 — April 2, 2019
Comments 2 — June 7, 2019
Comments 3 — September 30, 2019
GENERAL
1. September 30, 2019 — Thank you for the cost estimate. Inspection fees and performance
bond amounts will be confirmed once civil construction plans have been approved.
2. ok
3. ok
4. ok
5. ok
6. ok
7. ok
8. ok
Sheet C3.2 — ENLARGED GRADING AND DRAINAGE PLAN AND DETAILS
1. ok
2. ok
3. ok
4. ok
5. ok
6. ok
7. ok
8. ok
9. ok
10. ok
Sheet C3.3 — GRADING AND DRAINAGE DETAILS
1. ok
2. 9/30/2019 — Revise the road profile as follows:
a. Add note that fittings for connection to the existing main to be verified once the
pipe is exposed.
b. Add note that the connection to the existing main shall be the high end of the new
pipe section being laid. Likewise, note that the capped end shall be the low end.
c. Reference Detail 1 on sheet C4.3 for the 1" domestic water service connection.
d. Include stationing and offset for each end of the main, the blow -off, and the
domestic service and meter.
e. Show location of blow -off
f. It was felt that some added clarity was needed in the note re: how to lay the pipe.
Please note that the rising slope shall be to the north. In addition, the location of
the ARV shall be coordinated with the City inspector.
3. 9/30/2019 - The typical road section shows the separation between the existing storm main
and the existing sewer main to be 3-feet. With this info, there could be a conflict with the
installation of the proposed storm manhole. Please add notes to the plans stating the exact
location of utility pipes shall be verified and any conflicts shall be brought to the attention
of the engineer of record and the city inspector.
Sheet C4.2 — ENLARGED WATER AND SEWER PLAN
1. ok
2. ok
3. ok
4. ok
5. ok
6. ok
7. ok
8. ok
9. ok
10. 9/30/2019 — Revise notes pertaining to the water main as follows:
a. The note regarding the 45-degree (the note is placed on the west side of 72°a) shall
state RJ x RJ
b. For the connection to the existing main, add note that the fittings shall be verified
once the existing pipe is exposed.
c. Revise layout to show the RSGV on the north side of the 45-degree bend.
Page 2 of 3
d. Add note cross referencing the profile on Sheet C3.3.
e. Callout standard details for thrust blocking (Detail 3 on sheet C4.3)
L Standard detail WA-121 for the blow -off is referenced. Please also include detail in
plan set.
g. Add note to place blow -off in a concrete pad. This will help prevent vegetation
from covering the blow -off in the future.
h. Revise 8" cap note to state RJ cap
11. 9/30/2019 — Show the storm manhole with rotation away from the sewer pipe.
12. 9/30/2019 — Add note that the water meter shall be located in alignment with that portion
of the wall that is temporary.
13. 9/30/2019 — Provide invert elevation for side sewer connection to sewer manhole. Confirm
there are no conflicts with the storm pipe crossing.
14. 9/30/2019 - Reference and include in plan set city standard detail GU-421 (Type I MH),
which provides specific direction related to channeling and the ladder.
15. 9/30/2019 - Label sanitary sewer cleanout and reference city standard detail (Detail 5,
Sheet C4.3)
PLANNING DIVISION COMMENTS
Planning Division comments were emailed 9/19/2019 and have also been attached here for
reference. Please contact City Environmental Program Manager, Kernen Lien directly at 425-771-
0220 or by email at kernen.liengedmondswa.gov with any specific questions you may have
regarding these comments.
PEER REVIEW — SHORING WALL
1. There were not no further comments during the peer review, however, the City's utility engineer
is asking for a callout on Sheet SH3.1 that addresses the following:
a. Spacing of the 3 end ties
b. Size, material and location of the lifting inserts.
Page 3 of 3
Date:
To:
From:
Subject:
MEMORANDUM
September 9, 2019
Jeanie McConnell, Engineering Program Manager
Kernen Lien, Environmental Programs Manager
PLN20180033, Larsen 3 — Lot Short Plat
15729 75t" Place W
Civil Review Comments
I have reviewed the August 15, 2019 civil resubmittal. Please have the applicant address the
following items on the civil documents for the above reference short plat:
1. Native Vegetation Plan:
a. Monitoring Program: Addressed.
b. Cost Estimate: Addressed.
c. Consistency: Addressed.
May 22, 2019 Comment: Addressed.
2. Tree Cutting Plan: Addressed.
3. Geotechnical Review: Partially addressed. The property is located with the Earth
Subsidence Landslide Hazard Area (ESLHA) and subject to the requirements of Chapter
19.10 ECDC as well as critical area review in accordance with Chapter 23.80 ECDC
Geologically Hazardous Areas. Chapter 19.10 ECDC requires peer review of the geotechnical
reports for projects with the ESLHA. Peer review was conducted during the preliminary
subdivision review process (as well as with some work on the existing house on Lot 2). it
was noted in the staff report granting preliminary approval, that any development
associated with the subdivision that was not reviewed with building permit BLD20180517
for the foundation work on the existing residence on Lot 2 or the related to preliminary
approval of the subdivision will be subject to additional geotechnical analysis and peer
review consistent with Chapters 19.10 and 23.80 ECDC. Landau's peer review of the
geotechnical reports submitted with the subdivision preliminary review also noted:
...grading and site drainage plans should be subjected to further geotechnical
engineering review prior to construction. Furthermore, we concur with Nelson
Page 1 of 2
Geotechnical Associates' statement in their February 28, 2018 report that this review
should include specific stability analysis of proposed cuts and fills, and provide specific
recommendations for accomplishing the desired grading while maintaining long-term
slope stability. This analysis should also include an analysis of the two retaining walls
that are proposed along the western portion of 72nd Avenue West that will be extended
to provide access to the upper proposed lot, as well as all underground utilities that are
proposed in close proximity to the site's steep slope and associated buffer.
An updated geotechnical report has not been provided with the civil submittal. A
geotechnical report addressing the items identified by Landau for further review should be
prepared and sent for peer review consistent with Chapters 19.10 and 23.80 ECDC.
Note that the applicant is responsible for the cost of peer review and the City has yet to be
reimbursed for the peer review conducted with the preliminary approval which cost $625.
The applicant should be required to reimburse the City for the peer review prior to issuance
of the civil documents.
May 22, 2019 Comment: A "Geotechnical Plan Review Letter" was provided with the May
6, 2019 resubmittal. This geotechnical letter does not appear to address the criteria of
Chapters 19.10 and 23.80 ECDC. The geotechnical letter is subject to peer review at the
cost of the applicant. The applicant should be given the option to update the geotechnical
letter prior to sending it out for peer review, or to send it out for peer review and pay for
Landau to point out the deficiencies.
September 9, 2019 Comments: The amended geotechnical report and civil plans were sent
to Landau Associated for peer review, specifically in regards to the criteria of Chapters 19.10
and 23.80 ECDC. Landau found four deficiencies in the reports and civil plans related to the
development. Please have the applicant address the deficiencies noted in the attached
technical memorandum from Landau dated September 6, 2019.
Page 2 of 2
Technical Memorandum
TO: Kernen Lien, Environmental Programs Manager
City of Edmonds Planning Division
FROM: Sean Gertz, EIT and Steven Wright, PE
DATE: September 6, 2019
RE: Supplemental Geotechnical Peer Review
Submittal Package for Short Plat in a Critical Area
Larsen Residence — 15729 751" Place West
Edmonds, Washington
This technical memorandum summarizes the results of our supplemental geotechnical peer review of
the permit submittal package that was submitted to the City of Edmonds (City) for a proposed short
plat subdivision located at the above -referenced address, which is located within the North Edmonds
Earth Subsidence and Landslide Hazard Area (ESLHA) in Edmonds, Washington. The purpose of our
supplemental geotechnical peer review is to review portions of the submittal package and assess its
compliance with the City's 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 ESLHA. This review also assesses the submittal's compliance with the requirements of
Chapter 23.80 of the ECDC as required or noted in Chapter 19.10. This geotechnical peer review was
conducted in accordance with Task Order No. 19-02 of Landau Associates' On -Call Geotechnical and
Environmental Engineering Services Agreement with the City.
LAI previously completed a geotechnical peer review for this project and our initial review comments
are contained in a technical memorandum dated October 15, 2018. While the submittal that was
reviewed in 2018 was generally considered to be adequate, we recommended that we review
additional information of a geotechnical nature as it becomes available. The applicant's design team
has prepared and submitted additional geotechnical information related to proposed site grading and
retaining walls for peer review. This supplemental geotechnical peer review focuses on the additional
information provided.
For this round of peer review, we reviewed the following information that was forwarded to us by the
City:
• Civil Plans (stamped by Engineer), prepared by CG Engineering, dated May 3, 2018 and last
update July 31, 2019.
• Preliminary Geotechnical Engineering Evaluation, Larsen Property Short Plat and Residence
Underpinning (stamped by Geotechnical Engineer), prepared by Nelson Geotechnical
Associates, Inc. dated February 28, 2018.
• Geotechnical Plan Review and Comment Response Letter, Larsen Property Short Plat (stamped
by Geotechnical Engineer), prepared by Nelson Geotechnical Associates, Inc. dated August 13,
2019.
14 LANDAU
ASSOCIATES 130 2nd Avenue South • Edmonds, Washington 98020 • (425) 778-0907
Landau Associates
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 information that we reviewed includes most of the information in Sections 19.10 and
23.80 of the ECDC that is identified as being required. However, we found the following deficiencies
in the information that was submitted:
• The geotechnical letter, dated August 13, 2019 by Nelson Geotechnical Associates provides
results of slope stability analysis conducted based on the proposed development; however,
the resulting Factor of Safety (FS) under seismic conditions is 1.1. The FS under seismic
conditions should be 1.2 or greater, as required in ECDC 23.80.070(A.4.a).
The slope stability analysis under seismic conditions provided in the August 13, 2019
geotechnical letter shows a critical slip surface that extends approximately 75 ft from the top
of the slope; however, the Preliminary Geotechnical report, dated February 28, 2019 by
Nelson Geotechnical Associates recommends a setback of only 60 ft from the top of the slope.
Based on the analysis provided, a 60-ft setback could result in a structure being constructed
too close to the crest of the slope, especially when compared to the yet to be determined
distance that would be required to achieve a FS of 1.2 under seismic conditions. The design
team should clarify this inconsistency.
• The slope stability analysis provided in the August 13, 2019 geotechnical letter includes a
1,000 pcf surcharge for the proposed residence. We presume that Nelson Geotechnical
Associates intended to say 1,000 psf. Nevertheless, the Preliminary Geotechnical Report
recommends an allowable bearing pressure of 2,000 psf for the proposed residence. While we
recognize that the entire building footprint will not be subjected to a surcharge pressure of
2,000 psf, it is our opinion that the geotechnical engineer should analyze the stability of the
slope using a higher surcharge pressure (i.e., 2,000 psf) where shallow foundations will be
located and possibly a lower surcharge pressure in areas of the building footprint that will
subjected to lighter loads (e.g., beneath concrete slabs -on -grade).
Neither the Civil Plans dated July 31, 2019 by CG Engineering, nor the Preliminary
Geotechnical Report, dated February 28, 2019 by Nelson Geotechnical Associates
acknowledge the seasonal restrictions for clearing described in ECDC 23.080.070(A.6). A note
should be added to the Civil Plans with the purpose of identifying the seasonal restrictions.
This technical memorandum has been prepared for use by the City in evaluating the adequacy of short
plat submittal documents related to the proposed subdivision at 15729 751" Place West in Edmonds,
Washington. The focus of this review was the geotechnical aspects of the application. 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.
Geotechnical Peer Review
Larsen Residence Short Plat — 15729 75t" Place West 2 September 6, 2019
Landau Associates
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
Project EIT
SZ- Lt4vd
Steven R. Wright, PE
Principal
SMG/SZW/rgm
[\\EDMDATA01\PROJECTS\074\196\060\R\LARSEN RESIDENCE SHORT PLAT SUPPLEMENTAL PEER REVIEW_TM.DOCX]
Geotechnical Peer Review
Larsen Residence Short Plat — 15729 75t" Place West 3 September 6, 2019