HomeMy WebLinkAboutExhibit_7_Geotechnical_Report
Cobalt
Geosciences
P.O. Box 82243
Kenmore, Washington 98028
(206) 331-1097
August 22, 2016
Updated April 24, 2017
pmvrsingh@gmail.com
Mr. Satwant Singh
RE: Limited Stormwater & Geologic Hazard Evaluation
Proposed Six Lot Short Plat
13609 156th Avenue SE
Renton, Washington
Dear Mr. Singh,
In accordance with your authorization, Cobalt Geosciences, LLC has prepared this letter to
discuss the results of our limited stormwater and geologic hazard evaluation at the referenced
site.
The proposed development includes six single-family residences, access driveways, and
landscaped areas.
Site and Project Description
The site is located at 13609 – 156th Avenue SE in Renton, Washington (Figure 1). The site consists
of one rectangular parcel (No. 146340-0045) with a total area of approximately 1.3 acres.
The site is developed with a single-family residence and access driveway extending onto the
property from the north and near the east end of the property. There are several outbuildings
within the remainder of the property.
The site slopes gently downward toward the southwest with total topographic relief of about 25
feet. The site is vegetated with grasses, blackberry vines, and local deciduous and evergreen trees.
The site is bordered to the south and west by single-family residences, to the north by SE 2nd Place
and to the east by 156th Avenue SE.
The project consists of subdividing the existing parcel into six building lots. The existing
residence and outbuildings would be removed as part of site development.
Stormwater management will include a stormwater detention vault located in the west portion of
the site.
Area Geology
The Geologic Map of King County, indicates that the site is underlain by Vashon Glacial Till.
Vashon Glacial Till is typically characterized by an unsor ted, non-stratified mixture of clay, silt,
sand, gravel, cobbles and boulders in variable quantities. These materials are typically dense and
relatively impermeable. The poor sorting reflects the mixing of the materials as these sediments
were overridden and incorporated by the glacial ice.