Geotech Response.pdfZipp Geo
Geoprofessional Consultants
Project Number: 2092.01
April 2, 2019
Ken Huffman
10620 235th Place SW
Edmonds, WA 98020
Subject: Geotechnical Response to City of Edmonds 1/16/19 Planning Review Comments Letter
Huffman Residence Additions
10620 235th Place SW
Edmonds, Washington 98020
Dear Mr. Huffman:
Zipper Geo Associates, LLC (ZGA) has completed a review of the City of Edmonds Planning Review
Comments letter dated January 16, 2019. This letter provides our response to geotechnical comments
contained in the City of Edmonds letter. Our response is based on revised plans for the remodel project
(Revision 1) dated March 20, 2019. The revised plans eliminate one of the two proposed additions to the
residence and associated ancillary improvements. The revised plan includes a total of 180 square feet of
new impervious surface to be discharged via splash blocks as is currently done for the existing residence.
Citv Comment No. 1
"A critical areas determination was completed for the property on November 29, 2017 which indicated that
the property is within a Geologically Hazardous Area for erosion and landslide hazards. A geologic hazard
area report dated October 22, 2018 has been provided, however; the report should specifically address ECDC
23.80.060 and 23.80.070.
Please also have the geotechnical engineer evaluate and address in the geotechnical report, the impacts to
the landslide and erosion hazard areas as result of the proposed discharge of surface water toward the slope
via splash blocks as shown on the site plan sheet A0.0. Clarify how the proposed discharge meets the non -
point discharge requirement per 23.80.070.A.7; specifically address how the proposed drainage qualifies as
dispersed discharge and how the discharge was determined to not increase saturation of the slope."
ZGA Response to Comment No. 1
ECDC 23.80.060 addresses development standards for alterations of geologically hazardous areas or
associated buffers. The planned residential addition and associated site alterations are located within the
relatively level portion of the site and are not located within identified geologically hazardous areas or their
associated buffers. As such, it is our opinion that ECDC 23.80.060 is not applicable to the planned
improvements. However, our October 22, 2018 Geologic Hazard Area Report includes the following Risk
Evaluation Summary, which is in general accordance with the requirements of ECDC 23.80.060.
19019 36th Avenue West, Suite E Lynnwood, Washington 98036 (425) 582-9928
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Huffman Residence Addition, Edmonds, Washington
ZGA Project No. 2092.01
April 2, 2019
ZipperGeo
Geoprofessional Consultants
"Our geotechnical evaluation was limited to evaluating the potential for the planned development
to adversely affect identified Geologic Hazard Areas and the potential for identified Geologic Hazard
Areas to adversely affect the planned development. The planned additions to the existing residence
will be supported on dense to very dense glacial outwash deposits and are located beyond the
identified Geologic Hazard Areas and their associated buffers recommended herein. Provided that
the conditions and recommendations contained within this report are satisfied, it is our opinion that
the planned additions will be stable during the design life of the structures and the development will
not increase the potential for soil movement and the risk of damage to existing structures, the site,
and to adjacent properties from soil instability will not be increased."
Relative to splash block discharge, the planned residential addition results in an increased impervious
surface area of about 180 square feet, is located within the relatively level portion of the site mantled by
permeable glacial outwash deposits, and is located about 8 to 10 feet from buffer areas. In our opinion, the
planned alteration does not pose a threat to the public health, safety, and welfare, identified geologically
hazardous areas, or adjacent properties.
We appreciate the opportunity to submit this letter, and we trust that it meets your current needs. Please
do not hesitate to contact us should you have any questions.
Respectfully submitted,
Zipper Geo Associates, LLC
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I JAMES P. GEORQIS I
James P. Georgis, LG, LEG Thomas A. Jones, PE
Principal Principal
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