22-102038-SF Addendum to Report by Geotech Engineer 7-20-22RESUBMITTED
7/20/2022
CITY OF FEDERAL WAY Cobalt Geosciences, LLC
COBALTCOMMUNITY DEVELOPMENT
w; CaEi7SGtENCES
P.O. Box 82243
Kenmore, Washington 98028
July 1, 2022
Viral Shah
ViralpanditO gmail.com
RE: Geotechnical Addendum
Proposed Residence
3oo16 20th Place SW
Federal Way, Washington
In accordance with your authorization, Cobalt Geosciences, LLC (Cobalt) has prepared this letter
to discuss landscaping -related construction following completion of the construction of the
residence at the referenced site. Specifically, four -feet tall concrete walls have been constructed
west and near the residence to support yard backfill zones, enclose septic systems, and as part of
patio and landscaping finalization.
We visited the site in June 2022 to observe the areas. We used a 1/2 inch diameter probe to
evaluate the subsurface soils near the newly constructed concrete walls. Suitable bearing was
observed (2,000 psf) in medium dense native soils.
Our previous buffer and setback recommendations were primarily intended for the habitable
structure. The current concrete wall and ancillary construction locations are suitable.
At this site, the buffer and steep slope areas have been previously modified through grading, wall
construction (modular blocks), and a driveway further west. We recommend that the area
between the new concrete wall and localized steep slope be landscaped fully.
Sincerely,
Cobalt Geosciences, LLC
7/1/2022
Phil Haberman, PE, LG, LEG
Principal
www.cobaltgeo.com (2o6) 331-1097