Summary: Liquified hazardous wastes as well as oil and gas wastes are often injected into underground wells and deposited below drinking water supplies into porous rock formations that are separated from the drinking water by layers of nonpermeable rock. The nonpermeable rock reduces the likelihood of waste contaminating the drinking water. To protect drinking water supplies, the Safe Drinking Water Act requires the Environmental Protection Agency (EPA) to set minimum requirements for state underground injection control programs to regulate injection wells used for waste disposal. In addition, the 1984 amendment to the Resources Conservation and Recovery Act require EPA, beginning in 1988, to ban the disposal of untreated hazardous wastes into wells unless owners/operators could prove to EPA that the wastes would not migrate from the injection zone. This report discusses the (1) results of EPA's efforts to implement the ban on underground injection of hazardous wastes, (2) accuracy of EPA's inspection and enforcement data to ensure reliable program oversight, and (3) status of recommendations to improve the Underground Injection Control Program made in earlier GAO reports. Because two-thirds of the nation's hazardous waste and oil and gas waste injection wells are found in EPA Regions 5 and 6, which include Louisiana, Michigan, and Texas, GAO included these regions and states in this review.
