February 7, 2019

Jason Hegdahl, Cascade Corporation

2201 NE 201st Avenue

Fairview, Oregon 97024

Nick Garson, PG, The Boeing Company

P.O. Box 2207, M/S 7A-XA

Seattle, WA 98124

RE:  SVE Expansion and Rebound Testing, East Multnomah County Groundwater TSA Remedy, Fairview, Oregon (ECSI #1479)

Dear Messrs. Hegdahl and Garson,

The Oregon Department of Environmental Quality (DEQ) approves the Soil Vapor Extraction System Expansion and Rebound Testing Workplan for the East Multnomah County Groundwater Troutdale Sandstone Aquifer Remedy, dated January 29, 2019. This workplan was prepared on your behalf by Cindy Bartlett, RG and Brent Miller, PE of Geosyntec Consultants in Portland.

DEQ approves the scope of work proposed for the installation of six new vapor extraction wells, plumbing system, and the shut down and vapor rebound testing of VMW-A, VMW-B and VMW-D. All existing and proposed SVE wells are piped to the existing Central Treatment System vacuum pump. Please provide DEQ with the schedule for performance of this scope of work as well as the drilling schedule for angle borings VMW-E, VMW-F and VMW-G.

Please feel free to call me with questions.

Sincerely,

Kenneth Thiessen, CEG

Northwest Region Cleanup Section

cc:  Cindy Bartlett, R.G. Geosyntec Consultants

Brent Miller, P.E. Geosyntec Consultants

Chris Kimmel, P.G. Landau Associates

ECSI #1479