CERCLA requires EPA to compile a list of contaminated and potentially contaminated federal facilities. This list, known as the Federal Agency Hazardous Waste Compliance Docket (docket), is based on information that agencies are required to report to EPA. EPA compiled the first docket in 1988 and, under CERCLA, EPA is to publish a list of any new sites added to the docket in the Federal Register every 6 months. Under section 120(c) of CERCLA, EPA is to update the docket after receiving and reviewing notices from federal agencies concerning the generation, transportation, treatment, storage, or disposal of hazardous wastes or release of hazardous substances. After a site is listed on the docket, CERCLA requires EPA to take steps to ensure that a preliminary assessment is conducted. EPA has established 18 months as a reasonable time frame for agencies to complete the preliminary assessment. After the agency conducts the preliminary assessment, EPA reviews it to determine whether the information is sufficient to assess the likelihood of a hazardous substance release, a contamination pathway, and potential receptors. EPA may determine that the site does not pose a significant threat and requires no further action. If it determines that further investigation is needed, EPA may request that the agency conduct a site inspection to gather more detailed information. If, on the basis of the site inspection, EPA determines that hazardous substances, pollutants, or contaminants have been released at the site, EPA will use the information from the preliminary assessment and site inspection to calculate and document a site’s preliminary Hazard Ranking System (HRS) score, which indicates a site’s relative threat to human health and the environment based on potential pathways of contamination. Sites with an HRS score of 28.50 or greater become eligible for listing on the National Priorities List (NPL), a list that includes some of the nation’s most seriously contaminated sites. Based on the risk a site poses, EPA may place the site on the NPL. According to an EPA official, 158 federal sites are on the NPL, as of September 2015. Once a site is on the NPL, EPA is to oversee the cleanup. As part of its oversight responsibility, EPA works with the responsible federal agency to evaluate the nature and extent of contamination at a site. The agency must then enter into an interagency agreement with EPA that includes: (1) a review of remedial alternatives and the selection of the remedy; (2) schedules for completion of each remedy; and (3) arrangements for the long-term operation and maintenance of the site. According to EPA, the agreements also provide a process for EPA and the federal agency to resolve any disagreements related to implementing the cleanup remedy, with EPA being the final arbiter of such disputes. Once the agency and EPA agree on a cleanup remedy, the agency implements the remedy at the site. Afterwards, the agency must conduct long-term monitoring to ensure the remedy remains protective of human health and the environment. For federal sites not included on the NPL, CERCLA provides that state cleanup and enforcement laws apply, and most states have their own cleanup programs to address hazardous waste sites. USDA, Interior, DOD, and DOE have identified thousands of contaminated and potentially contaminated sites on land they manage, but there is not a complete inventory of sites, in particular, for abandoned mines. We found in our January 2015 report that there were at least 1,491 contaminated sites on land managed by USDA. These sites include 1,422 Forest Service sites, which are primarily abandoned mines; 2 Animal and Plant Health Inspection Service (APHIS) sites; 3 Agricultural Research Service (ARS) sites; 61 former grain storage sites once managed by the Commodity Credit Corporation (CCC); and 3 foreclosure properties belonging to the Farm Service Agency (FSA). In addition to sites with confirmed contamination, we found that USDA agencies have also identified some potentially contaminated sites. ARS had identified 3 sites that are potentially contaminated. Forest Service regions maintain inventories of potentially contaminated sites that include landfills, shooting ranges, and cattle dip vats, but there was no centralized database of these sites and no plans or procedures for developing one. These various inventories did not provide a complete picture of the extent of USDA’s potentially contaminated sites. For example, there were an unknown number of potentially contaminated former grain storage sites in the 29 states where the CCC previously used carbon tetrachloride. This number was unknown because the CCC relies on the states to notify them of potential contamination, and 25 of the 29 states had not yet reported whether there was suspected contamination at their former CCC grain storage sites. The Forest Service also deals with various other types of hazardous waste sites, such as methamphetamine laboratories, roadside spills, and waste dumps. Forest Service officials said that, since these types of sites may involve illegal activities and are, therefore, not routinely reported, it is not possible to develop a comprehensive inventory of these types of sites. In addition, in January 2015, we reported that the Forest Service had not developed a complete, consistent, or usable inventory of abandoned mines and had no plans and procedures for developing such an inventory because, according to Forest Service officials, they did not have the resources to complete a comprehensive inventory of all potentially contaminated abandoned mines on the agency’s lands. The Forest Service estimated that there were from 27,000 to 39,000 abandoned mines on their lands—approximately 20 percent of which may pose some level of risk to human health or the environment, based on the professional knowledge and experience of agency staff. Such risks may include chemicals and explosives, acid mine drainage, and heavy metal contamination in mine waste rock. However, we concluded that because the Forest Service did not have a complete inventory of abandoned mine sites, the actual number of abandoned mines on National Forest System (NFS) lands was unknown. According to a USDA official, USDA first attempted to create a national inventory of mines on NFS lands in 2003. Then, in 2008, the Forest Service established the Abandoned Mine Lands (AML) database to aggregate all available data on abandoned mines on NFS lands. The AML database drew data on pending abandoned mine sites from the 2003 database and Forest Service regional inventories, as well as from the U.S. Geological Survey and various other federal, state, and local databases. USDA officials said that, once the AML database was established, the purpose of the earlier database shifted away from maintaining an AML inventory to tracking sites that entered into the CERCLA process. However, as we reported in January 2015, the AML database has a number of shortcomings. For example, the data migration from multiple inventories led to data redundancy issues, such as some mine sites being listed multiple times under the same or different names. In addition, USDA officials told us that there was a lot of variation in the accuracy and completeness of the data on these mine sites, but a quality assurance review had not yet been performed. One Forest Service official said that, because of these problems, the data in the AML database were unusable for purposes of compiling a complete and accurate inventory of abandoned mines. In 2012, the Forest Service tried to obtain the agency resources necessary to clean up the database. Even though the Forest Service rated this project as “critical,” the project did not receive any resources because other projects were deemed more important, according to a Forest Service official. Similarly, in our January 2015 report, we found several problems with the Forest Service’s regional abandoned mine inventories. First, some regional inventories were incomplete. For example, officials in Forest Service Region 10, which is composed solely of the State of Alaska, said they believed there may be some abandoned mines scattered throughout Tongass and Chugach National Forests that had not yet been inventoried. They said that Forest Service Region 10 did not have enough staff to assess all abandoned mines across such a large area. Second, several Forest Service regional inventories contained inaccurate data. Third, the Forest Service’s regional offices maintained their inventories differently. Some regional offices maintained their own inventories of potentially contaminated sites, whereas other regional offices utilized state or local agencies’ inventories. Finally, the type of data on abandoned mines varied from region to region, making it difficult to consolidate into a coherent national database. Some regional offices tracked mines at the site level, some by their features—such as mine shafts, pits, ore piles, or machinery—and some used both approaches. For example, officials in Forest Service Region 3 told us that they had identified over 3,000 abandoned mine sites, and officials in Forest Service Region 4 told us that they had identified approximately 2,000 mine features but had not yet consolidated these features into mine sites. We reported in January 2015 that, without a comprehensive inventory of such sites or plans and procedures for developing one, USDA and the Forest Service will not have reasonable assurance that they are prioritizing and addressing the sites that pose the greatest risk to human health or the environment. Consequently, in January 2015, we recommended that the Secretary of Agriculture direct the heads of the department’s land management agencies to develop plans and procedures for completing their inventories of potentially contaminated sites. USDA disagreed with our recommendation and stated that it had a centralized inventory and that this inventory was in a transition phase as a result of reduced funding levels. USDA also stated that it had taken a number of actions to manage its inventory in a more cost-effective manner, reduce operating costs, and eliminate data collection redundancies across the USDA agencies. Subsequently, in a June 2015 letter to GAO, USDA described three corrective actions that the department planned to take in response to our recommendation. We believe that these actions are needed. We found in our January 2015 report that Interior had identified 4,722 sites with confirmed or likely contamination. These include 4,098 Bureau of Land Management (BLM) sites that the agency reported had confirmed contamination or required further investigation to determine whether remediation was warranted. The majority of these sites were abandoned mines.