Landau Comments #2.pdfLANDAU
ASSOCIATES
TECHNICAL MEMORANDUM en"MEN%LIGMTECH r-41KARVARE$Mas
TO: Leif Bjorback, Building Official
City of Edmonds Development Services Department, Building Division
FROM: Dennis R. Stettler, P.E. til / �'�---
DATE: June 7, 2013 ��
RE: SUPPLEMENTAL GEOTECHNICAL PEER REVIEW
EARTH SUBSIDENCE AND LANDSLIDE HAZARD AREA - BLD20120858
OLSON SFR —15500 75TH PLACE WEST
EDMONDS, WASHINGTON
This technical memorandum provides our supplemental 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,
Landau Associates previously completed a peer review for this project and summarized our observations
and recommendations in a Technical Memorandum dated November 19, 2012. Several submittal packets
pertain to this project. The submittal reviewed for our previous peer review in 2012 consisted of two
document packets—one stamped "Received August 23, 2012" and one stamped "Received October 1,
2012." The former packet was submitted for completeness review by the City; the latter packet contained
a replacement set of architectural -structural drawings, an updated structural calculations packet, and an
executed agreement with BNSF for stormwater tightline construction and discharge onto the railroad's
right-of-way. The City completed their review of the submittal package and provided review comments
to the applicant in November, 2012.
The applicant revised the design and resubmitted the documents for review with a letter dated
April 4, 2013; the submittal was suspended shortly after that date so that additional revisions could be
made. Revisions to the amended design, primarily relocating the structure to provide for adjusted
building setbacks from the property lines were made, along with changes to grading to reduce or
eliminate the need for walls, and to support the lower floor as a structural floor on grade beams instead of
slab -on -grade. Other changes were made to the storm drainage configuration. These changes were
documented in transmittal letters dated April 4 and May 2, 2013. The current review focuses on the most
recent of the revised documents from either April 4 or May 2, 2013.
The purpose of the current supplemental geotechnical peer review is to review revised 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, and our
previous review comments from our Technical Memorandum dated November 19, 2012. This
130 2nd Avenue South - Edmonds, WA 98020 - (425) 778-0907 - fax (425) 778-6409 - www.landauinc.com
geotechnical peer review was accomplished in accordance with Task Order No. 13-08 of Landau
Associates' On -Call Geotechnical Engineering Services Agreement with the City.
We have received and reviewed the following new or resubmitted information forwarded by the
City for review:
• Resubmittal of selected plans for The Proposed Olson Residence, 15500 75"' Pl. SW,
BLD20120858, letter from Architectural Design Associates, PS. to City of Edmonds, dated
May 2, 2013.
• Olson Residence, 15500 75"' Pl. SW, Plan Check No. 2012-0858, letter from Architectural
Design Associates, PS. to City of Edmonds, dated April 4, 2013.
• Site Plan (Sheet SPLO) listed in sheet index of Architectural Plan Set (above) but not bound;
encountered loose in submittal packet. Updated for revised setback, but still dated July 11,
2011.
• Architectural Plan Sheets A1.0 and AL 1, prepared by Architectural Design Associates, dated
August 20, 2012, but stamped by City of Edmonds as Resubmittal on May 3, 2013.
• Architectural/Structural Plan Set (14 Sheets, including architectural and structural plans,
elevations, and details) prepared by Architectural Design Associates, resubmittal dated April
4, 2013.
• Landscape Plan Set and Tree Hazard Evaluation packet, including Re -vegetation and Tree
Mitigation Plan (drawing LI. 0), Significant Tree Inventory and Tree Preservation Plan
(drawing L2.0). Harmsen & Associates. Plans dated August 13, 2012; revision 1 dated
March 29, 2013.
• Resubmittal for Olson Residence, 15500 75"' Place West, Landscape Architecture response to
November 2012 comments, letter prepared by Harmsen & Associates, dated March 29, 2013.
• Civil Plan Set (5 Sheets, CI through C5, including Winter TESL & Grading Plan, Grading
and TESC Details, Detailed Drainage Plan, Notes & Details, and Utility Plan W. Pump.
• Geotechnical Plan Review and Comment Letter, Olson Residence, Edmonds, Washington.
Letter prepared for Mr. George Olson by Nelson Geotechnical Associates, inc., dated April 3,
2013.
The following sections provide our specific geotechnical peer review comments.
GEOTECHNICAL REPORT
The geotechnical plan review and comment letter addresses Landau Associates' previous review
comments.
We understand that our previous review comments on the structural plans regarding the location
and details of a proposed soldier pile and lagging wall no longer apply, as the proposed wall has been
excluded from the project. However, the Revised Geotechnical Report prepared by Nelson Geotechnical
Associates (7/15/2011) describes a "failed" or "failing" approximate 6 ft high block retaining wall that the
proposed soldier pile and lagging wall was intended to replace. The report also states "it is our opinion
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that this wall is unstable and could cause problems on the property in the future. " By contrast, the
Geotechnical Plan Review and Comment Letter prepared by Nelson Geotechnical Associates (4/3/2013)
states that the wall is a deteriorating block wall located within City of Edmonds right-of-way and
recommends that the wall be monitored and repaired/replaced at a later date as needed. We are concerned
that the wall has been described as unstable, failing, or failed and it appears that this wall could
potentially present either a hazard to the property or to the public on the public right-of-way (or both) if
the wall was to suddenly fail. Monitoring may not be effective in alleviating this hazard. We recommend
that the integrity of this wall and consequences of failure be further evaluated by either the applicant,
the City, or the two parties in a collaborative approach to assess the degree of hazard to the property or
to the public and to evaluate whether monitoring is sufficient, or whether mitigation, repair, or
replacement alternatives should be implemented
CIVIL PLANS AND STORM DRAINAGE STUDY
The revised civil and storm drainage plans appear to have addressed the previous review
comments, including appropriate reference to the current geotechnical engineer, clarification of a drawing
symbol, and prohibiting temporary soil stockpiles on site. We notice that the reference to no stockpiling
on the site and removing excess excavated material from the site on Sheet Cl also contains the note:
"Any soil removed fi•om the site must be hauled to a City approved site. " We would expect that the City
does not really care where the excess soil is taken, as long as it is taken to a site that is legally allowed to
accept the soil in accordance with any applicable requirements and regulations regarding disposal, or
filling and grading. We recommend that the City not approve any specific disposal site.
LANDSCAPE DESIGN
Harmsen & Associates has updated the plans and indicated a total of 23 replacement trees in
order to conform to the required 2:1 replacement ratio, rather than the 21 replacement trees indicated on
previous plans.
It appears that one of our earlier review comments may have been misinterpreted. In our review
letter we commented that "Automatic sprinklers or other irrigation systems are not specified on the
landscaping plans." What was meant by that comment was that the absence of automatic or irrigation
systems is highly desirable, since such systems are not allowed by the City in the North Edmonds Earth
Subsidence and Landslide Hazard Area as stated in ECDC 19.10.070. The design team may have
misinterpreted our comment and attempted to add the provision that automatic sprinklers or irrigation
systems could be added. Note 12 on Drawing L1.0 states in part that "The Owner may install automatic
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sprinklers or irrigation systems." The note regarding automatic sprinkler or irrigation systems should
be removed
This technical memorandum has been prepared for use by the City of Edmonds in evaluating the
adequacy of resubmitted permit submittal documents related to the proposed Olson single family
residence at 15500 75`h 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 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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