7301 HARDESON RD 2019-01-11 - Laserfiche WebLink

{ PW 1705- D.7-'9 GEOENGINEERS 17425 NE Union Hill Road,Suite 250 Redmond,Washington 98052 425.861.6000 August 31, 2018 Cadman, Inc. 7554 185th Avenue NE Redmond, Washington 98073 Attention: Bill Sayer,Vice President, Land Development Subject: Hydrogeologic Services Hardeson Pond Infiltration Verification Testing Mountain View Business Centre-Division 9 Everett,Washington File No.0643-013-02 INTRODUCTION This letter(Addendum No. 1)summarizes the results of two verification pilot infiltration tests(PITs)completed in the Hardeson Pond, a stormwater management facility designed by David Evans and Associates (DEA)for the Mountain View Business Centre Division 9 project located in Everett, Washington. The Hardeson Pond is shown relative to existing physical features in Figure 1, Hardeson Pond Site Plan. Two small-scale PITs were conducted at the site as requested by the City of Everett in their Public Works Permit No. PW1705-029. The tests were conducted following the guidelines provided in the Washington State Department of Ecology's (Ecology) 2014 Stormwater Management Manual of Western Washington (2014 SWMMWW).GeoEngineers, Inc.(GeoEngineers)previously issued a geotechnical report for the Hardeson Pond titled "Infiltration Evaluation, Glenwood and Hardeson Ponds, Cadman Glenwood Pit, Everett, Washington", dated August 10, 2017.This letter is submitted as Addendum No. 1 to our August 10,2017 report. PROJECT DESCRIPTION The Hardeson Pond site is located adjacent to Hardeson Road, and near the commercial property located south of Shuksan Way in Everett, Washington. The Hardeson Pond is planned to be about 230 feet long by 55 feet wide with the pond bottom at Elevation 427.0 feet. Pond side slopes are designed at 3H:1V (horizontal:vertical)and the maximum water level is designed at Elevation 434.0 feet.We understand that an infiltration rate of 1.6 inches per hour was used by DEA in developing the design of the pond. The Hardeson Pond Infiltration Facility Detail is shown on Figure 2. Existing silty fill located below the pond bottom will be removed down to native advance outwash sand and gravel and replaced with approximately 5 feet of engineered soil consisting of a washed sand.