Pursuant to a congressional request, GAO reviewed the Environmental Protection Agency's (EPA) completed Superfund hazardous waste cleanup actions, focusing on the: (1) type and extent of actions taken at those sites; and (2) challenges EPA will face in managing and monitoring these sites.

GAO found that: (1) significant amounts of hazardous wastes have been removed or controlled at 149 EPA Superfund hazardous waste sites; (2) EPA removal and remedial actions including landfill waste disposal, waste capping, and the use of contamination treatment technology have addressed long-term health risks and significant surface, soil, and groundwater contamination problems; (3) although most cleanup actions involved surface waste treatment, some sites did not require remedial action because EPA already addressed site risks; (4) other groundwater contamination problems required long-term treatment and monitoring; (5) EPA completed 125 separate removal actions at over half of the 149 sites and averted additional site and environmental contamination by removing waste from sites or constructing barriers to prevent access to waste; (6) despite these accomplishments, EPA needs to improve its reporting of cleanup work performed at sites on the National Priorities List; (7) EPA, states, and responsible parties can expect increased demands on cleanup resources because current and future Superfund sites will require complex cleanup efforts and long-term monitoring and maintenance; and (8) although states have increasingly challenged EPA interpretation of legislation requiring them to fund all costs for operating and maintaining completed or deleted sites, recent court rulings have upheld the EPA interpretation.