size and scope of these programs. The Committee sought to determine (1) the number of sites that have not yet reached closure, (2) principal chemicals of concern, (3) remediation costs expended to date, (4) cost estimates for reaching closure, and (5) the number of sites affecting local water supplies. Information was gathered for sites in the EPA’s Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), Resource Conservation and Recovery Act (RCRA), and Underground Storage Tank (UST) programs; sites managed by the DoD, the Department of Energy (DOE) and other federal agencies; and sites under state purview (e.g., state Superfund, voluntary cleanup programs, and Brownfields programs). The metrics and milestones across all these programs differ, making comparisons and the elimination of overlap difficult. Nonetheless, the Committee used these data to estimate the number of complex sites, the likelihood that sites affect a drinking water supply, and the remaining costs associated with remediation.

At least 126,000 sites across the country have been documented that have residual contamination at levels preventing them from reaching closure. This number is likely to be an underestimate of the extent of contamination in the United States for many reasons. For example, the CERCLA and RCRA programs report the number of facilities, which are likely to have multiple sites. The total does not include DoD sites that have reached remedy in place or response complete, although some such sites may indeed contain residual contamination. Although there is overlap between some of the categories, in the Committee’s opinion it is not significant enough to dismiss the conclusion that the total number of 126,000 is an underestimate.

No information is available on the total number of sites with contamination in place above levels allowing for unlimited use and unrestricted exposure, although the total is certainly greater than 126,000. For the CERCLA program, many facilities have been delisted with contamination remaining in place at levels above unlimited use and unrestricted exposure. Depending on state closure requirements, USTs are often closed with contamination remaining due to the biodegradability of petroleum hydrocarbons. Most of the DOE sites, including those labeled as “completed,” contain recalcitrant contamination that in some cases could take hundreds of years to reach levels below those allowing for unlimited use and unrestricted exposure.

A small percentage (about 12,000 or less than 10 percent) of the 126,000 sites are estimated by the Committee to be complex from a hydrogeological and contaminant perspective. This total represents the sum of the remaining DoD, CERCLA, RCRA, and DOE sites and facilities, based

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