Summary: GAO discussed: (1) environmental problems at federal facilities; and (2) facilities' compliance with environmental laws. GAO found that many federal facilities: (1) contaminated groundwater and soil with hazardous and radioactive substances; (2) contaminated drinking water aquifers, posing a possible public health threat; and (3) continued to discharge hazardous materials into the environment. GAO also found that federal agencies: (1) were slow in identifying their potential hazardous waste sites, the solutions to correct them, and the costs of complying with environmental laws; (2) could not provide information on how much they spent on site identification and cleanup because their budgets did not separately identify those costs; and (3) could not predict how long it would take or how much it would cost to clean up the sites, since that would depend on the complexity of the remedies. GAO believes that agencies need to more efficiently inform Congress of their expenditures for compliance activities.