10292010 Geotech Memo.pdfMEMORANDUM
Perteet Inc.
TO: Ed Sibrel, City of Edmonds Senior Engineering Technician
FROM: Jason Walker, ASLA, Environmental and Community Planning Manager
DATE: October, 29, 2010
RE: Shell Valley SEPA Review Per 23.80.070 Development Standards — Specific
Hazards
Pursuant to SEPA review of Section 23.80.070(2) of the City of Edmonds Development
Standards regarding Specific Hazards, we are providing the following supplemental information
for city review:
2. Alterations. Alterations of an erosion or landslide hazard area and/or buffer may only occur
for activities for which a hazards analysis is submitted and certifies that:
a. The development will not increase surface water discharge or sedimentation to adjacent
properties beyond predevelopment conditions;
The project will utilize low impact permeable pavement materials and technologies for the
pavement surfacing of the emergency access road. The roadway will also be constructed with
cross -drains that will allow for continued surface and groundwater flow from the adjacent hill
side to an existing small depressional wetland that occurs in a narrow, flat bottomed, valley
between two steep forested slopes. The hydrologic regime of the wetland is not expected to
change as a result of the proposed project. This project will also not increase surface water
discharge or sediment transport to adjacent properties.
b. The development will not decrease slope stability on adjacent properties; and
By constructing the road in the chosen location, the steep, forested slopes will remain intact,
thereby avoiding erosion issues. Roadway and shoulder widths have been reduced as much as
possible while still allowing for construction of a functional emergency access route.
c. Such alterations will not adversely impact other critical areas
The proposed roadway has been located on the far western edge of an existing low -value
welted in order to avoid and minimize wetland impacts as much as practicable b n site
and design considerations such as steep slopes and mature trees. Alternati W Vp® e
project have been investigated and no other location to further decrease y6v C
provide secondary emergency access for residences on Shell Valley Roa �1,� vpio"—eq.WarA ya N
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