The Lockwood Solvent Groundwater Plume Site (LSGPS) is a 580-acre Superfund (CERCLA) site in Lockwood, Montana, which was added to the National Priorities List (NPL) in December 2000. Historic releases from a chemical handling and distribution facility have resulted in tetrachloroethene (PCE), trichloroethene (TCE), dichloroethene (DCE) and vinyl chloride (VC) impacts to soil and groundwater as with dense non-aqueous phase liquids (DNAPL) also being identified in the subsurface at the site. The chlorinated solvent groundwater plume extends downgradient beneath a neighborhood and ultimately discharges into the Yellowstone River.