The U.S. Environmental Protection Agency ordered Raytheon and the U.S. Air Force to clean up a migrating plume of contaminated groundwater found near a water treatment plant that serves 50,000 residents of Tucson, Arizona. Groundwater contaminated with excessive amounts of trichloroethylene (TCE) and dioxane (DX), chemical solvents believed to be human carcinogens, was found near the Tucson International Airport Area Superfund Site, where Raytheon and the Air Force share a facility called Air Force Plant 44. The contaminants migrated north of the facility and into the water treatment plant. For more than 50 years, aircraft and electronics facilities (including Raytheon and its predecessor, Hughes Aircraft) and unlined landfills have deposited various chemical contaminants into the site. The EPA’s order requires Raytheon and the Air Force to install and operate an advanced oxidation process system to treat the solvents in the plume. If they disobey the order, the EPA will fine the parties up to $32,500 per day, per violation.