In 1994, a sampling of a drinking water well by the Colorado Department of Health (CDH), in accordance with Colorado drinking water regulations for "non-transient non-community" systems, showed the well containing CCl4 in concentrations (9 parts per billion [ppb]) above the Maximum Contaminant Level (MCL) [5 ppb]. Four other drinking water wells within a 1/2 mile radius also were tested with no detections of CCl4. On October 25, 1994, EPA initiated a Removal Action and began supplying bottled water to 33 residents. A Treatability Study was conducted by EPA’s Emergency Response Team (ERT) to determine the best method of removing the CCl4, which ranged from 6 to 99,000 ppb. Four air strippers and 29 carbon filters were installed on 33 homes. A thorough investigation was conducted by EPA Contractors (TAT and REAC) in 1995 and 1996. A source removal system was installed in March of 1997; it consisted of 4 pumping wells, 6 reinfiltration wells, a shallow tray air stripper system, and carbon polishing tanks.
The source area around Cornelius and Vosler Streets, where groundwater is pumped and treated, continues to clean up slowly. Carbon absorption systems in individual residences also continue to filter water for homes that remain above the MCL of 5 ppb. As of May 2026, there are twenty-three homes that have systems installed. Each year, EPA conducts annual sampling for these residences and replaces spent carbon as-needed.
