In 2001, an environmental assessment of soil and groundwater contamination associated with natural gas production was conducted by Pioneer Natural Resources USA Inc. The gas compression and production facilities are located in the West Panhandle Field, Moore and Potter Counties, Texas, and have been in operation since the 1930s. Shallow and/or deep soil contamination, primarily from used lube oil and natural gas condensate was discovered at most of the gas compression facilities. Limited amounts of non-aqueous phase liquids (NAPL) were observed on shallow perched water-bearing zones at two sites and dissolved phase (BTEX) plumes with benzene concentrations exceeding drinking water standards were observed at a total of six sites. The depths to the shallow perched water-bearing zones at these sites varied from approximately 20 to 40 feet below ground surface.