REV2 BLD2022-1279+DESCRIPTION+6.10.2024_1.34.05_PM+4311887June 6, 2024
ES-9697
Select Homes, Inc.
8304 — 212t" Street Southwest
Edmonds, Washington 98026
Attention: Gary Klick
Subject: Permeable Pavement Driveway Infeasibility
Aloha Street Single -Family Residence
741 Aloha Street
Edmonds, Washington
Dear Gary:
Earth
Solutions
NW«C
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
In accordance with your request, Earth Solutions NW, LLC (ESNW) has prepared this letter
regarding the use of permeable pavement for the proposed new driveway. ESNW reviewed the
referenced documents for the subject project and recently visited the site to observe current
driveway subgrade conditions. Based on review of the referenced geotechnical evaluation, dense
to very dense transitional bed soil deposits were encountered beginning at about one and one-
half feet below pre-existing grades, which should be considered relatively impermeable from a
stormwater design standpoint. The impermeability is exhibited by the mottling noted from about
6 to 18 inches in depth, which is indicative of seasonal, perched groundwater seepage. The
proposed driveway slopes toward the new house. Based on the soil conditions noted in the
geotechnical evaluation and those recently observed during construction, as well as the gradient
of the driveway, it is our opinion that the driveway should be constructed with conventional
concrete. The use of permeable pavement over the shallow impermeable/low permeable soil
layer would create saturated conditions within one foot of the bottom of the lowest gravel base
course, which is considered an infeasibility criterion in accordance with Edmonds engineering
standards.
15365 NE 90" Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704
3130 Varney Lane, Suite 105 Pasco, WA 99301 • (509) 905-0275
esnw.com
Select Homes, Inc.
June 6, 2024
ES-9697
Page 2
We trust this letter meets your current needs. If you have any questions or if additional information
is needed, please call.
Sincerely,
EARTH SOLUTIONS NW, LLC
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06/06/2024
Henry T. Wright, P.E.
Associate Principal Engineer
References:
• Geotechnical Evaluation, prepared by Cobalt Geosciences, dated February 14, 2022
• Civil Site, Stormwater Management, & ROW Plan / Profiles, prepared by CSP Engineering,
revised May 16, 2024
Earth Solutions NW. LLC