EPA does not actively seek out sites for the Superfund program but relies on states or interested parties to report them. Once reported, sites are added to EPA’s inventory for evaluation. As of March 1994, EPA’s inventory had 36,785 nonfederal sites, of which 1,192 had been placed on the National Priorities List. Evaluation of potentially hazardous sites occurs in several stages. At the completion of each stage, EPA may determine that no federal action is needed or it may proceed to the next stage. First, EPA requires that a site receive a preliminary assessment within a year of its entry into the inventory. The preliminary assessment involves a review of available documents and possible site reconnaissance. If the preliminary assessment indicates a potential problem, the site moves to the next stage of evaluation—the site inspection—which involves collecting and analyzing soil and water samples as appropriate. If warranted by the results of the site inspection, sites enter the final decision process. This process involves other evaluations, including an extended site inspection if needed, scoring under EPA’s hazard ranking system; and a judgment by EPA officials on the appropriateness of listing the site on the priorities list. An extended site inspection requires more samples and could involve installing wells to monitor groundwater or other nonroutine data collection activities. The hazard ranking system is a method of quantifying the severity of site contamination to determine if a site should be placed on the list. The system assigns a numerical score based on the likelihood that a site has released or has the potential to release contaminants into the environment, the characteristics of the contaminants, and the people or environments affected by the release. A site must score at least 28.5 on the hazard ranking scale in order to be placed on the list. Sites can be dropped from further consideration following the extended site inspection or the scoring process. Sites also can be dropped from further consideration if, in the judgment of EPA regional officials, the sites do not pose risks great enough to warrant a Superfund cleanup. In addition to the sites following the process described above, the EPA inventory includes a large group of sites that have already been inspected but are awaiting reevaluation because of a change in the evaluation process. The Superfund Amendments and Reauthorization Act of 1986 required EPA to revise its evaluation system to make it more comprehensive and accurate in its assessment of threats to human health and the environment. According to EPA site assessment officials, the revision will change the mix of sites, but not necessarily the number of sites, that will end up on the priorities list. The revision was effective in March 1991. During the transition to the revised system, sites were evaluated through the site inspection stage using the original evaluation system. However, EPA decided to use the new system to make final decisions about placing these sites on the priorities list. In October 1991, EPA began to reevaluate these 6,467 sites, which it referred to as its evaluation backlog. Reevaluation could include collecting additional site information as well as limited sampling. As of the close of fiscal year 1993, EPA had completed this process for about 1,600 of the 6,467 sites. Fewer sites are being reported to EPA for evaluation, but site inspection results indicate that new sites reaching the site inspection stage are as likely to have contamination requiring a Superfund cleanup as those inspected in the past. The number of sites reported annually has been declining since fiscal year 1985. (See fig. 1.) In fiscal year 1993, 1,159 sites were added to the inventory—29 percent less than the prior year and 68 percent less than in fiscal year 1985. EPA attributed the decline since 1985 to the fact that many states now have their own Superfund programs. According to EPA site assessment officials, states are reluctant to report new sites, preferring instead to manage the cleanup themselves. EPA Region I site assessment officials suggested that states generally report sites that present challenging enforcement or cleanup problems. The percentage of sites that EPA believes warrant further consideration after completing the site inspection has been fairly steady for the last 10 years. (See fig. 2.) From program inception through fiscal year 1993, 43 percent of the 17,556 sites inspected were considered hazardous enough to need further consideration for the priorities list. In fiscal year 1993, 43 percent of the 725 sites inspected were also considered for further action. (App. II provides statistics on the number and percent of nonfederal sites accepted and rejected for further consideration after site inspection.) EPA officials do not expect to find in the future very large, heavily contaminated sites equivalent to Love Canal, which entered the Superfund program early in its history. However, the officials believe that contamination at newly discovered sites is generally not less severe than at previously reported sites—just less obvious. Earlier site discoveries more often included sites where the hazards were visible, such as barrels of hazardous waste above ground. Sites that are being discovered and reported now, according to EPA officials, are those with less obvious—but equally serious—problems, such as groundwater or drinking water contamination. Recent estimates of the future size of the Superfund workload have differed. In congressional testimony in February 1994, EPA forecast the smallest increase—1,700 new sites. In a report dated January 1994, CBO predicted 3,300 new sites through 2027, although it said that a wide range of additions was possible. EPA’s Inspector General in a January 1994 report estimated that 3,000 of the 6,467 sites in the agency’s evaluation backlog could be added to the Superfund. In February 1994 congressional testimony, EPA’s Administrator testified that the Superfund National Priorities List could grow to about 3,000 federal and nonfederal sites, or roughly 1,700 more sites than are currently on the list. According to EPA officials, this estimate was based on an internal agency analysis prepared by the Office of Emergency and Remedial Response. The Office prepared low, medium, and high estimates, and EPA based its testimony on the medium estimate. (See app. III for a detailed breakdown of EPA’s estimates.) EPA’s estimates treated current and future inventory sites differently. In EPA’s medium estimate, 6.5 percent of the currently reported sites were estimated to become Superfund sites compared with 3.5 percent of the sites that will be reported in the future. The inventory of reported sites was estimated to grow by 20,500 sites by the year 2020, or 54 percent more than at present. The estimate projected that the number of sites added to the inventory each year would decline from 1,500 sites in fiscal years 1994 through 1999 to 500 sites in fiscal years 2010 through 2019. EPA officials said that they based the decline on less state reporting, not on the existence of fewer sites that could be reported. CBO’s estimate of potential future Superfund additions was developed in two parts. (See app. V.) First, CBO estimated the number of sites that would be reported to EPA’s inventory of potential hazardous waste sites by developing trend lines based on the number of sites reported from 1981 to 1992. Because of the data’s variability, CBO developed a base case, or most probable scenario, and low- and high-case scenarios. In the base case, CBO estimated that 25,394 sites would be added to the inventory by the year 2027. This estimate was about 5,000 sites higher than EPA’s medium estimate. In the low and high cases, CBO estimated that 15,151 and 50,000 sites, respectively, would be added. Second, to determine the percentage of reported sites that would ultimately be placed on the priorities list, CBO relied on EPA staff’s opinion since, according to CBO’s report, usable site evaluation data were not available. When asked by CBO, EPA staff estimated that between 5 and 10 percent of all future inventory sites would be placed on the priorities list. CBO chose 8 percent for its base-case estimate and applied this rate to current and future inventory sites. For its own medium forecast, EPA estimated that 6.5 percent of the current inventory and 3.5 percent of the sites added to the inventory in the future will be placed on the priorities list. CBO’s base-case estimate, after adjustment to eliminate federal sites, resulted in adding 3,300 more sites to the priorities list. The range of additional sites for the low- and high-case scenarios was between 1,100 and 6,600 sites. EPA’s Inspector General estimated that 3,136 sites in the evaluation backlog could move to the priorities list. This estimate was made as part of a study of EPA’s processing of these backlogged sites. At the time of the Inspector General’s review, EPA had evaluated only 942 of the 6,467 sites. To estimate the number of potential sites for the priorities list, the Inspector General determined the proportion of sites evaluated in each region that were found to warrant consideration for the priorities list. The Inspector General then applied these proportions to the total number of backlogged sites in each region and added the regional numbers. The Inspector General reduced the total to account for an estimated proportion of sites that drop out in the final decision process. More recent data suggest that the Inspector General’s estimate may be somewhat high. According to EPA’s site evaluation staff, the Inspector General’s estimate of 3,136 additional sites is high since it assumed that in the future, 52 percent of the sites in the backlog could move beyond the site inspection stage, the rate prevailing when the Office of Inspector General did its study. However, data for fiscal year 1993, available after the Inspector General completed the study, showed that the percentage of the backlogged sites warranting priorities list consideration had dropped to 28 percent. The number of future Superfund sites cannot be predicted with certainty.