The Libby Groundwater Contamination site is located in Libby in Lincoln County, Montana. A lumber and plywood mill operated at the site between 1946 and 1969. Mill operations included treating wood with creosote, pentachlorophenol (commonly referred to as PCP) and other chemicals. Spills and disposal practices at the site contaminated soil, groundwater, surface water and sediment with hazardous chemicals. In 1979, EPA discovered PCP contamination in well water at a nearby residence. Following cleanup, operation and maintenance activities and groundwater monitoring are ongoing.