20090223104628.pdfLANDAU
14 ASSOCIATES
TECHNICAL MEMORANDUM NRiURA1 RESOURCES
TO: Ann Bullis, Building Official
City of Edmonds Development Services Department.. Building Division �+ e
FROM: Dennis R. Stettler, P.E., Colin Turnb . .G. RECEIVED
DATE: February 23, 2009 FEB 23 2009
PMEW SERVICES CTR.
RE: DRY SEASON EARTHWORK EXTENSION GEOT]ECHNICAL PEER R0FE-LRy OF EI)MONDS
PEIamn No. BLD20080117
HILLIARD SFR -15515 75TH PLACE WEST
EDMONDS, WASHINGTON
This technical memorandum provides our geotechnical peer review comments for a requested dry
season earthwork construction extension. Construction of the residence is currently underway. The
project is located within the Earth Subsidence and Landslide Hazard Area (ESLHA) of North Edmonds.
Earthwork in the ESLHA during the winter season between October 1 to April 30 is restricted. The
Building Official may consider a request, supported by the owner's geotechnical consultant, for
earthwork to continue during this time period. The Building Official considers such factors as the type
and extent of construction, location, duration, construction approach, monitoring, and other factors in
deciding whether to grant approval of earthwork construction during the winter season.
Cornerstone Geotechnical, Inc. has provided a letter to the City of Edmonds (City) dated
February 11, 2009 requesting a dry season extension in order to complete certain final stages of site
construction. The planned activities include a retaining wall from the northwest corner of the house to the
northwest corner of the property and tie-in of underground utilities to existing utilities in 750' Place West.
Cornerstone Geotechnical, Inc. describes the extent of the planned construction and the planned
construction approach in their letter. We understand that Cornerstone Geotechnical, Inc. has been
providing weekly monitoring and reporting in accordance with the building permit regarding stormwater
best management practices.
In our opinion, the requested dry season earthworks extension is reasonable, given the extent of
the planned construction and the approach to the construction as outlined in Cornerstone Geotechnical's
letter. We concur that the planned earthwork should not occur during periods of rainfall. Any backftll
and compaction of utility trenches within public right-of-way must be completed in accordance with City
requirements. We recommend that Cornerstone Geotechnical, Inc. provide special inspection services for
the earthwork and retaining wall construction; including retaining wall drainage provisions. We also
recommend that weekly monitoring and reporting of stormwater best management practices continue.
130 2nd Avenue South e Edmonds, WA 98020 a (425) 778-0907 • fax (425) 778-6409 • www.landauinc.com
This technical memorandum has been prepared for use by the City in evaluating the adequacy and
appropriateness of the request for a dry weather earthwork extension related to the construction of the
Hilliard single family residence at 15515 75"' Place West. The focus of this review was the geotechnical
aspects of the request. The purpose of the review was to assess the appropriateness of the request 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 monitor site conditions during construction.
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.
DRSICBT/rgm
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