The Palermo Wellfield Superfund Site (Site) is located near Interstate Highway 5 and Trosper Road in Tumwater, Washington. The Site includes a City-operated water-supply wellfield and an adjacent residential neighborhood in the Deschutes River Valley (sometimes referenced in site documents as the Palermo Valley), as well as upland source areas including the current Washington State Department of Transportation (WSDOT) Materials Testing Laboratory (MTL), a former WSDOT MTL, and the Southgate Dry Cleaners business. Trichloroethene (TCE) was detected at the wellfield in 1993. Subsequent investigations identified a TCE groundwater plume over 3,000 feet (ft) long and 600 ft wide, and a smaller tetrachloroethene (PCE) plume near the Southgate Dry Cleaners site.

The Site remedy for groundwater includes capture of contaminated groundwater at the Palermo Wellfield with air stripping to reduce the levels of TCE and PCE below maximum contaminant levels (MCL). The air strippers have been in operation since 1999.

• Optimization Review, Palermo Wellfield Superfund Site, City of Tumwater, Thurston County, Washington (PDF)(152 pp, 24 MB, 2012, 542-R-11-010)