July 2, 2018

Jason Hegdahl, Cascade Corporation

2201 NE 201st Avenue

Fairview, Oregon 97024

Nick Garson, The Boeing Company

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

Seattle, WA 98124

RE:  Work Plan for Soil Vapor Extraction System Expansion, East Multnomah County Troutdale Sandstone Aquifer Remedy, Fairview, Oregon (ECSI #1479)

Dear Messrs. Hegdahl and Garson,

The Oregon Department of Environmental Quality (DEQ) has reviewed the Work Plan for Soil Vapor Extraction System Expansion East Multnomah County Troutdale Sandstone Aquifer Remedy, dated February 19, 2018. This workplan was prepared on your behalf by Cindy Bartlett, RG and Brent Miller, PE of Geosyntec Consultants in Portland. This workplan was appended to the 2017 Annual Performance Report for the East Multnomah County, Troutdale Sandstone Aquifer Remedy, dated April 3, 2018.

DEQ approves the scope of work proposed for the installation of three vapor extraction and groundwater monitoring wells to be angle-drilled beneath NE 201^st Ave. The three wells will be piped to the existing Central Treatment System vacuum pump. Please provide DEQ with the schedule for this drilling work.

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