GEO Addendum LetterCOBALT
G E 0 S C I E N C E S
July 16, 2020
Wayne Sharp Construction
WMesharp.office ftmail.com
RE: Geotechnical Addendum
Proposed Single -Family Residence
8045 —184th Street SW
Parcel No. 27041800103800
Edmonds, Washington
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, Washington 98028
In accordance with your authorization, Cobalt Geosciences, LLC has prepared this letter to
discuss additional details regarding our previous infiltration evaluation. We have reviewed a City
comment dated February 18, 2020.
Our site investigation included a small-scale pilot infiltration test performed in accordance with
Appendix B — Methods for Determining Design Infiltration Rates (June 2017 (City of Edmonds)).
The testing included an approximately 6-hour pre-soak period followed by testing and verification
of soil and groundwater conditions after testing. No groundwater mounding was observed
following the testing in an excavation extending approximately 6 feet below grade.
We recommend that the bottom of the trenches be situated within native soils consistent with
those described in the previous report. We recommend a maximum trench/system depth of 4 feet
below grade. Local loosening of the native soils may be required up to 2 feet below the bottom of
system elevations. We recommend locating systems at least 40 feet apart and at least 10 feet from
property lines. We should be on site to confirm soil conditions and provide additional
recommendations if necessary.
Sincerely,
Cobalt Geosciences, LLC
P "ONY,y�
-WA�H�c���
If .1�5 - r
54896 ,1vL
,0
7/16/2020
Phil Haberman, PE, LG, LEG
Principal
www.cobaltgeo.com (2o6) 331-1097