For 25 years, TCE-polluted groundwater has been pumped for treatment from an old Air Force Plant near Tucson where chemicals were dumped by weapons-systems manufacturers from the 1940s until the 1970s. Discovered in 1981, the groundwater contamination remains at very high levels in areas of the 1,300-acre site. Some monitoring wells still show pollution at more than 10,000 parts per billion. TCE, also known as trichloroethylene, is a cancer-causing industrial solvent.
From 1987 to 2009, the Air Force was pumping out polluted groundwater in this area and running it through an air-stripping system to remove contaminants. In 2009, it switched to what’s known as advanced oxidation form of treatment, in which hydrogen peroxide and ozone are injected into pumped-out groundwater to destroy TCE, 1-4 dioxane and other toxic chemicals. Ozone peroxide is more effective and uses less energy than air stripping.