This decision document presents the Selected Remedy for the Lockwood Solvent Groundwater Plume Site, in Billings, Montana. The State of Montana Department of Environmental Quality (DEQ) and the United States Environmental Protection Agency (EPA) chose the Selected Remedy in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendments and Reauthorization Act of 1986, and in accordance with Montana's Comprehensive Environmental Cleanup and Responsibility Act (CECRA). To the extent practicable, the Selected Remedy is also in accordance with the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). DEQ and EPA based this decision on the Administrative Record file for the LSGPS. EPA has consulted with DEQ throughout conduct of the RI/FS, the development of the Proposed Remedial Action Plan (Proposed Plan) (DEQ 2004), and in selection of the remedy. EPA concurs with this remedy and adopts this Record of Decision. The response action selected in this Record of Decision is necessary to protect the public health or welfare or the environment from actual or threatened releases of hazardous substances, pollutants, or contaminants into the environment.