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City of Edmonds Gov o
Development Services Department
1215 th Avenue North
Edmonds, Washington 98020
Attention: Ms. Theresa Umbaugh
Subject: Geotechnical Review
Proposed Bui Residence
16105 75th Place West
Edmonds, Washington
Plan Review Number: 05-564
J-2322
May 23, 2006
As requested by the City of Edmonds, Zipper Zeman Associates, Inc. (ZZA) has
completed third -party geotechnical review for the above referenced project located within the
Meadowdale landslide hazard area in Edmonds, Washington. Preliminary geotechnical review
comments were provided by ZZA in a letter dated January 4, 2006- A response letter dated
February 23, 2006 by LSI Adapt was provided to us.
Based on our review of the provided response, we requested additional information
regarding the soil strength parameters used in the slope stability analysis. LSI Adapt responded
via email, which is attached to this letter. Overall, the LSI Adapt response letter adequately
addresses the review comments, in our opinion. The items discussed below are listed in order of
the provided response.
Response Number 1: As requested, LST Adapt reviewed their report and the previous
RLA and Geoengineers reports. LSI Adapt concluded that it was unwarranted to modify
their analysis as they have performed site specific subsurface explorations and analyses.
While the results of their analyses may differ from other investigators, their conclusions
are based on site-specific information obtained by the project geotechnical engineers. In
our opinion, the analyses provided by the . engineer are in accordance with requirements
of the ECDC.
Response Number 2: LSI Adapt provided firther detail on the stability analyses
performed and provided further detail on the strength parameters used in the analyses.
We requested additional information regarding the soil strength parameters used which
can be found in the attached email correspondence. As discussed above, while their
interpretations may differ from other investigators, their interpretations are based on site-
specific information obtained by the project geotechnical engineers, and, in our opinion,
are in accordance with the requirements of the ECDC.
18905 33r1 Avenue West #117, Lynnwood, WA 98036 425-771-3304 Fax: 425-771-3549
LZA Proposed Bui Residence — Edmonds, Washington
Job No. 1-2322
May 23, 2006
mr.160m,
Page 2
• Response Number 3: As requested, LSI Adapt provided a slope stability analysis for the.
temporary slope excavations. While there is a reduction in the factor of safety, the
minimum factor of safety calculated is above generally accepted geotechnical
engineering standards. In addition, the critical failure surface calculated appears to
remain within the subject property bounds. Based on this information, and the fact that
LSI Adapt performed a site-specific analysis, the provided response complies with ECDC
requirements, in our opinion. However, due to the nature of this project, we recommend
that the project geotechnical engineer monitor the slope excavations during construction..
In addition, we recommend that excavation and grading activities should be limited to the
generally accepted dry season (approximately November 1 to March 31).
•
Response Number 4: The response is acceptable.
Based on our review and the provided responses by the project geotechnical engineer, it
is our opinion that the geotechnical aspects of the project generally conform to the Edmonds
Development Code with respect to the Meadowdale Earth Subsidence and Landslide Hazard
code requirements.
We trust that this letter meets your needs at this time. Should you have any questions
regarding this project, please contact us at your convenience.
Respectfully Submitted
Zipper Zeman Associates, Inc.
Kristopher T. Hauch, P.E.
Project Engineer
6;70-4� 4 ?
John E. Zipper, P
Principal
Enclosed: Email Correspondence (May 4, 2006)
CC: LSI Adapt, Inc. — Mr. Rolf B. Hyllseth, P.E. .
J-2322 Fina[ ReviewOS2306.doe
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