6375-2letter-0305202015365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
March 5, 2020
ES-6375.02
Bush, Roed, & Hitchings, Inc.
2009 Minor Avenue East
Seattle, Washington 98102
Attention: Mr. Ted Dimof
Subject: Response to Comments
Southwest 320th Street Plat
21st Avenue South and Southwest 320 th Street
Federal Way, Washington
Reference: Earth Solutions NW, LLC
Geotechnical Engineering Study
ES-6375.00, dated December 7, 2018
Earth Solutions NW, LLC
Infiltration Evaluation
ES-6375.01, dated February 11, 2020
Bush, Roed & Hitchings, Inc.
Preliminary Clearing & Grading Plan, dated March 18, 2019
City of Federal Way
Federal Way Critical Areas Map, dated May 2016
City of Federal Way
Technical Review Comments
Upland Federal Way Preliminary Plat, dated June 6, 2019
Dear Mr. Dimof:
In accordance with your request, Earth Solutions NW, LLC (ESNW) has prepared this response
to City of Federal Way comments. The comments pertinent to the Geotechnical Report aspects
of the project are provided below followed by our response.
City of Federal Way Comment 1 – The geotechnical report references an outdated critical areas
map (September 2012).
Bush, Roed, & Hitchings, Inc. ES-6375.02
March 5, 2020 Page 2
Earth Solutions NW, LLC
ESNW Response – Based on the review of the May 2016 Federal Way Critical Areas Map, there
are no geologically hazardous areas (landslide, erosion, or seismic) within, or immediately
adjacent to the subject site.
Federal Way Comment 2 – The geologically hazardous areas section of the report needs to cite
Federal Way Revised Code and address the buffer impacts to site.
ESNW Response – Based on our review of the Federal Way Revised Code (FWRC) Section
19.145 – Environmentally Critical Areas and the referenced critical areas map, no geologically
hazardous areas (landslide, erosion, or seismic) have been identified within, or immediately
adjacent to the subject site.
The December 7, 2018 Geotechnical report incorrectly identified the slope along northern
embankment of the subject site as a landslide hazard. Upon further review of topographic
surveys of the area, the northern embankment of the subject property is associated with a man-
made historical road cut along Southwest 320th Street. Therefore, the steep slope along the
northern embankment does not meet the criteria of a Landslide Hazard Area as defined in FWRC
19.05.070.
Based on review of the referenced Preliminary Clearing and Grading Plan, the majority of native
soil along the northern slope will be cut down to closely match the current road grade along
Southwest 320th Street. In our opinion, the proposed modification of the northern slope will
increase the overall stability of the hillside. Retaining walls are proposed along the northern edge
of the development to account for grade changes. As such, and based on our review, the
proposed modifications are acceptable from a geotechnical standpoint.
Federal Way Comment 3 – The report states that grading and stormwater plans were not
available for review at the time of report preparation. The preliminary grading and stormwater
plans are now available and need to be reviewed and addressed in the geotechnical report per
FWRC 19.145.250.2.e.
ESNW Response – Based on review of the referenced preliminary grading and stormwater
plans, our recommendations within the referenced December 7, 2018 Geotechnical Report and
the February 11, 2020 Infiltration Evaluation have been appropriately incorporated into the plans.
Bush, Roed, & Hitchings, Inc. ES-6375.02
March 5, 2020 Page 3
Earth Solutions NW, LLC
We appreciate the opportunity to be of service to you and trust this letter meets your current
needs. Should you have questions, or if additional information is required, please call.
Sincerely,
EARTH SOLUTIONS NW, LLC
Kyler T. Kelly Raymond A. Coglas, P.E.
Senior Staff Geologist Principal Engineer
03/06/2020