This section provides information about abandoned hardrock mines, sites, and features; and federal and state agency roles in addressing abandoned hardrock mines. Federal and state agencies generally describe abandoned hardrock mines in terms of mine sites, the individual features that comprise a site, or both. However, these agencies do not all have a common definition for what constitutes an abandoned hardrock mine or mine site, as we found in 2008. The agencies generally agree on what constitutes an individual feature—for example, a feature can be a mine opening (such as a tunnel, pit, or vertical shaft), a structure, or a pile of discarded materials (known as mine tailings or waste rock) that is left behind after ore is crushed and the valuable minerals are extracted. They also generally agree that an abandoned mine site can be comprised of only one feature (e.g., an isolated mine shaft) or many features (e.g., an area with multiple entries, shafts, open pits, mill buildings, and tailings piles). There is no universally agreed-upon average number of features per site. Also, not all federal and state agencies count both sites and features—some agencies only count sites, some only count features, and some count both. The individual features that make up a mine site may pose hazards to physical safety and risks to human health and the environment. Physical safety hazards. Abandoned hardrock mine features that pose physical safety hazards generally present immediate danger of injury or death. Examples of physical safety hazards include unstable mine tunnels that can collapse without warning; unmarked open mine shafts and deep pits that pose a danger to individuals who may inadvertently drive off-road vehicles into them; and deadly concentrations of gases, such as carbon monoxide and methane, present inside some mines that can asphyxiate explorers. To address physical safety hazards, federal and state agencies typically focus on identifying and mitigating the risk from individual features. They may safeguard these features by, for example, filling, capping, or gating the abandoned mine openings with engineered structures. After a dangerous feature is identified, an agency may post a warning sign or erect a fence to temporarily limit access to the feature until the agency can permanently close it. According to a 2008 Interior Inspector General report, physical hazards require the least expertise to identify and evaluate and the least funding to fix or mitigate. Environmental hazards. Mine features can also contribute to degradation of the environment and present short- and long-term risks to human health. For this report, we refer to these collectively as environmental hazards. People may be exposed to these hazards when recreating or living near an abandoned mine. Examples of environmental hazards include a mine tunnel that drains acidic water laden with heavy metals into a waste rock or tailings piles located along the banks or in the middle of streams that release hazardous substances such as arsenic, lead, and mercury into the water; and tailings that have dispersed into a surrounding community’s soil, exposing residents to harmful substances. The extent of environmental hazards at abandoned mines can vary widely, from sites that contain one draining tunnel and a few waste rock piles to sites with extensive underground tunnel networks, many waste rock piles, and miles of dispersed tailings. Some contaminated hardrock mine sites are included on the National Priorities List, which includes some of the most seriously contaminated sites that EPA identifies for long-term cleanup. The work required to address environmental hazards varies depending on the extent, type, and concentration of contaminants. For example, agencies may take one or more of the following actions at a site: remove waste rock or tailings from streams; develop passive water treatment systems that allow water to flow out of mines into treatment ponds; manage the waste on-site or transport it off-site for disposal; or establish active water treatment systems for the most contaminated sites that require continuous long-term monitoring, among other actions. According to EPA documents, sites with environmental hazards can cost hundreds of millions of dollars and take many years to address. For example, as of July 2019, the actual costs at the 25 most expensive mine and mineral processing sites ranged from $50 million to $583 million per site, and EPA had been working on some of the sites for over 20 years. Furthermore, agencies monitor remedies after completion to help ensure that they are achieving the desired results. Figure 1 depicts examples of physical safety and environmental hazards found at abandoned hardrock mine sites and activities that could take place to address them. Land ownership at abandoned mine sites is often complicated. The General Mining Act authorizes miners to patent, or purchase, the land associated with their mining claims—thereby mined land often passed from federal to private ownership. Partly because of this, many abandoned mine sites are a patchwork of federal, private, and other lands, and the ownership boundaries are not always clear. Agencies refer to these sites as mixed ownership sites. The Forest Service, BLM, the Park Service, EPA, and OSMRE, as well as states with abandoned hardrock mines, administer programs that address abandoned hardrock mines. Specifically, these federal and state agencies collect information about abandoned hardrock mine sites and features, and the associated hazards, on land under their jurisdictions. These agencies also safeguard the physical safety hazards and clean up the environmental hazards present at these mines. Agencies inventory and address these mines based on their different authorizing statutes, regulations, and missions. The Forest Service is responsible for managing about 193 million acres of national forests and grasslands throughout the United States. The Forest Service’s Safety and Environmental Restoration program oversees the agency’s work on abandoned hardrock mines. The Forest Service distributed $15.9 million in appropriations to the Safety and Environmental Restoration program in fiscal year 2019. USDA also distributed about $6.9 million in fiscal year 2019 to the Forest Service to address environmental hazards at several abandoned hardrock mines. USDA seeks recovery of cleanup costs under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended (CERCLA), from responsible parties, such as current and former owners and operators of a contaminated site, to help reimburse costs at such sites. The Forest Service develops and maintains its information about abandoned hardrock mines primarily at its regional, national forest, and district offices. In general, the Forest Service tracks physical safety hazards by feature and environmental hazards by mine site. As of November 2019, the Forest Service did not have a national inventory of abandoned hardrock mine features or sites and the physical safety hazards they may pose. However, information about environmental hazards at abandoned hardrock mine sites is contained in a database maintained by USDA that tracks progress on all hazardous waste cleanup projects funded by the department, including projects at abandoned hardrock mines. Forest Service regional and national forest staff inventory, assess, mitigate, and monitor the physical safety and environmental hazards at abandoned hardrock mine sites on Forest Service-managed land as part of their daily responsibilities. BLM manages 245 million acres of public lands in the United States, located primarily in the western states and Alaska. BLM’s Abandoned Mine Lands program is aimed at protecting public safety and reducing liabilities by eliminating or minimizing physical safety and environmental hazards posed by abandoned mines, among other objectives. BLM’s Hazardous Materials Management program also addresses environmental hazards at all types of contaminated sites, including abandoned hardrock mines. In fiscal year 2019, BLM received a total of $38.5 million in appropriations for these programs. In addition, Interior distributed $2.7 million to BLM in fiscal year 2019 from the Central Hazardous Materials Fund—an Interior account that supports response actions undertaken at contaminated sites pursuant to CERCLA—for work at abandoned hardrock mines. BLM maintains a national inventory of abandoned hardrock mines in its Abandoned Mines and Site Cleanup Module database to help track information about sites, features, and hazards. However, as of 2019, BLM officials said the agency is shifting from tracking information by site, which can be subject to interpretation, to primarily tracking and reporting abandoned mine features. In addition to its abandoned mine database, BLM submits a subset of information about its contaminated abandoned mines to Interior for inclusion on the department’s list of contaminated sites, the Environmental and Disposal Liabilities list. BLM state, district, and field office staff inventory, assess, and mitigate the physical safety and environmental hazards at abandoned hardrock mines on BLM- managed land while conducting their daily work. The Park Service manages more than 85 million acres in 419 park units across the country. The Park Service addresses abandoned hardrock mines on this land through an abandoned mine safety program and an environmental compliance and cleanup program. In fiscal year 2019, the Park Service received $5 million in appropriations to address physical safety hazards on abandoned mineral lands. Interior also distributed $890,000 from the Central Hazardous Materials Fund to the Park Service to address contaminated abandoned hardrock mine sites in fiscal year 2019. The Park Service recovers costs from responsible parties at abandoned mine sites through CERCLA. The Park Service maintains information about abandoned hardrock mine sites and features in its Abandoned Mineral Lands Database. In 2013, the Park Service completed a system-wide inventory and assessment project to identify abandoned mines on lands it manages. In addition, the Park Service submits information to Interior about contaminated abandoned mine sites for inclusion on the Environmental and Disposal Liabilities list. Park Service headquarters and regional offices may assist park units in addressing hazards and preserving cultural resources and wildlife habitat at abandoned hardrock mines on Park Service-managed land. EPA administers the Superfund program, which was established under CERCLA to address the threats that contaminated waste sites pose to human health and the environment. As part of the Superfund program, EPA oversees and conducts investigations and cleanup actions at a variety of hardrock mine and mineral processing sites on private and other nonfederal lands and mixed ownership sites. The Superfund program operates on the principle that polluters are to pay for the cleanups rather than passing on the costs to taxpayers. EPA may compel parties statutorily responsible for contamination at sites to clean them up or to reimburse EPA for its cleanup costs. Responsible parties at abandoned hardrock mines could include current or former owners or operators of a site; persons who arranged for disposal, treatment, or transportation of hazardous substances; or the transporters of hazardous substances. To address contaminated sites—including abandoned mines—that do not have viable responsible parties, EPA uses funding from appropriations to the Superfund program, which were approximately $1.1 billion in fiscal year 2019. EPA maintains information about abandoned hardrock mine and mineral processing sites on nonfederal lands, including tribal lands, and mixed ownership sites in its national database of contaminated sites, the Superfund Enterprise Management System. EPA counts these mines and processing facilities by site and not by individual mine feature. According to EPA officials, many of the mine sites included in the database may contain tens to hundreds of individual features. In addition, EPA does not count sites that pose solely a physical safety hazard since they fall outside of the Superfund program mission. In addition, EPA and authorized states address certain abandoned hardrock mines in accordance with the Clean Water Act. Specifically, EPA and state agencies regulate discharges of pollutants to waters of the United States at abandoned mine sites under the act, such as mine tunnels draining contaminated water that exceeds water quality standards. To comply with the act, an entity operating a cleanup project involving a draining mine tunnel or other concentrated discharge source must obtain a permit, under which the discharge must be treated or managed to meet and maintain applicable water quality standards. OSMRE’s Abandoned Mine Land program primarily focuses on reclaiming and restoring land and water resources degraded by past coal mining, but the program also supports reclamation at abandoned hardrock mines. In accordance with the Surface Mining Control and Reclamation Act of 1977, as amended, OSMRE can provide grants for the reclamation of certain abandoned hardrock mines under limited circumstances—in particular, after a state or Indian tribe certifies that it has cleaned up its abandoned coal mine sites and the Secretary of the Interior approves the certification. Absent such certification, OSMRE can award these grants at the request of a state or Indian tribe where necessary to protect the public health, safety, general welfare, and property from extreme danger of adverse effects from the abandoned hardrock mine, and the Secretary of the Interior grants the request. In fiscal year 2019, OSMRE distributed a total of $310.5 million in grants to states and tribes to address abandoned coal and non-coal mines. OSMRE does not maintain an inventory of abandoned hardrock mines since the Abandoned Mine Land program’s primary objective is to address abandoned coal mines. States that receive grants from OSMRE to address non-coal abandoned mines may maintain their own inventories of abandoned hardrock mines. According to OSMRE budget documents, western states in particular often use OSMRE grants to address physical safety hazards at high-priority abandoned hardrock mines for which there is no other source of federal funding. States identify and address physical safety and environmental hazards at abandoned hardrock mines on state, county, and private lands within their borders, often through state abandoned mine programs. States may also work with federal agencies to identify and address these hazards on federal land. Some state agencies manage or oversee cleanup activities under CERCLA at abandoned hardrock mines. State agencies may receive funds to support their work at abandoned hardrock mines from nonfederal and federal sources, including state-appropriated funds, responsible parties under CERCLA, and cooperative funding agreements or grants from federal agencies. States with abandoned hardrock mines generally maintain databases or inventories that identify the locations of these mines and any associated hazards. As of May 2019, the Forest Service, BLM, the Park Service, and EPA together identified in their databases at least 140,652 abandoned hardrock mine features—of which over 60 percent are known to pose or may pose physical safety or environmental hazards. Officials from 13 western states also identified from their state databases about 246,000 abandoned hardrock mine features on federal and nonfederal lands within their states, including about 126,000 features that pose physical safety or environmental hazards. Some state information overlaps with federal agency information, but the extent of overlap is unknown, according to state officials. Federal and state officials also estimated that there likely are hundreds of thousands of additional abandoned hardrock mine features that they have not yet captured in their databases. The Forest Service, BLM, the Park Service, and EPA identified in their databases at least 140,652 abandoned hardrock mine features, as of May 2019. Of this amount, BLM identified 103,029 features and the Park Service identified 20,675 features. As previously noted, the Forest Service and EPA track abandoned mines by site and not by features associated with the sites; the Forest Service identified 16,375 sites and EPA identified 573 sites. According to agency officials, many abandoned hardrock mine sites contain more than one feature. Since there is no agreed-upon average number of features per site, we counted the minimum of one feature per Forest Service and EPA site for the purpose of this analysis. As a result, the total number of features identified by federal agencies likely is underestimated. Of the 140,652 total features, about 89,000 features are known to pose or may pose a physical safety or environmental hazard, according to information in the federal agencies’ databases. Specifically, agencies confirmed 7,802 features pose a hazard, of which 6,439 pose a physical safety hazard and 1,363 pose an environmental hazard; and identified 81,541 features with an unconfirmed hazard (whereby agency staff had not assessed current conditions in person to confirm the hazard), of which 60,279 may pose a physical safety hazard and 21,262 may pose an environmental hazard. Table 1 shows information about abandoned hardrock mine features that pose or may pose physical safety and environmental hazards, by agency. However, agency officials said there could be approximately 393,000 more abandoned hardrock mine features on federal land that the agencies identified on historic maps but have not captured in their captured in a central database. In addition, BLM officials estimated there are about 380,000 abandoned hardrock mine features on the land BLM manages that are not captured in its abandoned mine database. Park Service officials did not estimate a number of additional abandoned mines that might be in Park Service units; they said they believe their database is relatively comprehensive. Given the Forest Service and BLM estimates of additional features not found in their databases, the total number of estimated and identified abandoned hardrock mine features on lands within Forest Service, BLM, Park Service, and EPA jurisdiction is at least 533,652. Figure 2 depicts federal agency information about the numbers of confirmed and unconfirmed physical safety and environmental hazards on the lands under these agencies’ jurisdictions, in relation to the total estimated abandoned hardrock mine features, as of May 2019. To develop more comprehensive information about the total number of abandoned hardrock mine features on the lands they manage, the Forest Service and BLM are taking steps to improve their databases, including capturing information about abandoned mines that are not currently in a database. Specifically, Forest Service officials told us that they are establishing a centralized geospatial database that will consolidate information about abandoned hardrock mine features with physical safety hazards that is currently maintained in regional and national forest offices. They said they expect the new database will be populated in fiscal year 2020 and that it will provide regional and headquarters managers with better information about the extent of features with physical safety hazards. In addition, BLM officials said that field staff have been identifying and adding new features each year to its database, prioritizing features located close to communities and recreational areas. BLM officials said that they plan to update the database and communicate this information to field staff in fiscal year 2020 to help ensure staff enter information about new features into the database consistently. Officials with the 13 western states that we reviewed identified about 246,000 abandoned hardrock mine features on the federal, state, and private lands within their state borders, as of May 2019. As with the federal agencies, officials with five of the 13 states provided information about total mine sites and not features; as a result, we counted the minimum of one feature for each reported mine site for the purpose of our analysis. Of the 246,000 total features in these states, state officials estimated that about 115,000 features pose a physical safety hazard and about 11,000 features pose environmental hazards. State officials said that many of the features identified in their databases were also likely to be found in the federal agencies’ databases, but the extent of overlap is unknown. Specifically, the state officials’ estimates include abandoned mine features on federal, state, and private land because states may work on abandoned hardrock mines on both federal and nonfederal lands. However, state officials are not always able to quantify the number of mine features on federal land versus private or state land. For example, some states’ inventories are based on information from maps and databases that did not always include details about land ownership boundaries, which are necessary to differentiate on what lands the features are located. In addition, in instances in which the states could identify the features that are on federal land, such as in Utah and Nevada, state officials did not know how many of those features were also captured in federal agency databases. Similar to the federal agencies, officials with the 13 states estimated that the actual number of abandoned hardrock mine features in their states is higher than the information contained in their databases. State officials noted that their inventories are incomplete, in part because they have not conducted comprehensive, on-the-ground work to identify all the abandoned mine features in their states. They primarily focus on addressing the hazards they have already identified. Nevertheless, state officials estimated that the number of abandoned hardrock mine features in the 13 states could total more than 620,000. For example, California officials we interviewed said field staff had identified more than 70,000 individual abandoned mine features in the state as of May 2019. However, based on information from topographic maps, they estimated that 274,000 total mine features exist statewide, with an undetermined number of physical safety and environmental hazards. The states’ estimates of abandoned hardrock mine features reflect the different ways states collect information about abandoned hardrock mines. For example, California and Nevada officials explained that they count each individual abandoned mine feature in their states, whereas Colorado and Utah officials said that they only collect information about potentially hazardous features. Colorado officials estimated that there are 23,000 potentially hazardous abandoned hardrock mine features in the state. However, if the state were to count all of the features in Colorado, including shallow prospecting pits that are unlikely to pose a physical safety hazard, the officials said the total estimate would be hundreds of thousands of mine features. In addition, some states, including Idaho and California, reported numbers of abandoned mine features that included non-hardrock mines, such as sand and gravel pits, because their abandoned mine programs address different types of abandoned mines. Federal agencies spent, on average, about $287 million annually identifying, cleaning up, and monitoring abandoned hardrock mines, for a total of about $2.9 billion, from fiscal years 2008 through 2017. The Forest Service, BLM, the Park Service, EPA, and OSMRE primarily worked in partnership with other federal and state agencies and some nongovernmental stakeholders when addressing these mines, according to federal officials. Officials from the 13 western states we reviewed estimated spending an additional total of about $117 million in nonfederal funds over the 10-year period, or an average of nearly $12 million annually, to address abandoned hardrock mines within their states. Federal agency officials said they estimated it would cost billions more to address abandoned hardrock mines in the future. Federal agencies spent, on average, about $287 million annually, or a total of about $2.9 billion, to identify, clean up, and monitor hazards at abandoned hardrock mines from fiscal years 2008 through 2017. (See fig. 3.) EPA spent 80 percent of the total federal expenditures—about $2.3 billion—to address environmental hazards. Of the $2.9 billion in total federal expenditures, approximately $1 billion was reimbursed by responsible parties. Appendix II contains additional information about Forest Service, BLM, Park Service, EPA, and OSMRE expenditures by state. The agencies used some expenditures to address physical safety hazards but used most to address environmental hazards at abandoned hardrock mines. Physical safety hazards. The Forest Service, BLM, and the Park Service spent a total of over $105 million from fiscal years 2008 through 2017 to address mine features that posed physical safety hazards. According to officials with these agencies, this included filling in holes and installing gates at tunnels and other mine openings to allow bats, tortoises, and other wildlife to continue accessing important habitat. (See fig. 4.) Officials also said that their expenditures include funds provided to state agencies and others through cooperative funding agreements for projects where the state or other entity managed the work at the sites. Environmental hazards. From fiscal years 2008 through 2017, the Forest Service, BLM, the Park Service, and EPA spent a total of about $2.5 billion to address environmental hazards at abandoned hardrock mines. According to agency officials, work at these sites included conducting initial site investigations, designing and implementing remedies to address contamination, operating water treatment facilities, and monitoring completed cleanup actions. The agencies either managed this work themselves or provided funding through cooperative agreements to state agencies or others to manage the work. EPA spent about $2.3 billion at 394 sites, with about 40 percent spent at five sites. Of EPA’s total expenditures, $983 million (43 percent) was reimbursed by responsible parties. In addition, the Forest Service, BLM, and the Park Service spent a total of about $232 million to address various environmental hazards on lands they manage, of which about $40 million was reimbursed by responsible parties. Further, OSMRE reported that 12 states and two Indian tribes spent approximately $190 million in OSMRE grants to address abandoned hardrock mines and other non-coal sites from fiscal years 2008 through 2017. OSMRE officials did not specify how much of the $190 million was spent to address physical safety hazards versus environmental hazards since the agency does not require states and tribes to report such information. Table 2 shows federal agency expenditures by agency and type of hazard. Forest Service, BLM, and Park Service officials we interviewed said they conducted most of their work to address physical safety and environmental hazards at abandoned hardrock mines in collaboration with state agencies, nonfederal stakeholders, and other federal agencies, including EPA. These officials noted that it is important to partner with state agencies and EPA because many of the abandoned mine sites are of mixed ownership and the federal land management agencies generally do not have authority to address mine features on nonfederal lands. Federal agency officials said it is also helpful to pursue partnerships at mixed ownership sites to leverage limited funding. For example, Forest Service and BLM officials told us that they have partnered with Trout Unlimited, a nongovernmental organization focused on conserving freshwater fisheries and their watersheds, on projects to address environmental hazards at mixed ownership abandoned hardrock mine sites in several western states. Examples of projects that federal agencies undertook with partners include: Flat Creek-Iron Mountain Mine and Mill, Montana. Since 2014, the Forest Service has coordinated with EPA and the state of Montana to address contamination from this abandoned mine and mill site on private and Forest Service-managed lands upstream from the town of Superior. Silver, lead, and other hardrock mining operations left mill tailings piles that contaminated soil, groundwater, and surface water in Flat Creek, which flows for 3.5 miles from the mine site through Forest Service and private lands into the town. The local government and individuals also used tailings as fill material in yards, roadways, and other locations, including the high school track. The Forest Service took the lead on the portion of the site on the land it manages, and EPA and the state took the lead on various nonfederal portions of the site. At the state’s request, in 2000, EPA started assessing and cleaning up 79 residential and community properties in Superior; it completed this effort in 2013. In 2017, the state removed mine tailings from the private lands along Flat Creek with EPA oversight. As of November 2019, the Forest Service has been working with Trout Unlimited and the state to remove the mine tailings from the banks of Flat Creek on Forest Service land. Trout Unlimited representatives and Forest Service officials said they are also planning to reconstruct the stream channel and floodplains and restore fisheries habitat in the summer of 2020 after the tailings are removed. Gold Butte National Monument, Nevada. In 2018, BLM and the Nevada Division of Minerals worked with other federal, state, and local agencies to address 40 features that posed physical safety hazards within the historic Gold Butte Mining District in southern Nevada. The abandoned mine features were within the BLM- managed Gold Butte National Monument, which was established in 2016. According to project documents, the anticipated increase in recreation as a result of the monument designation prompted BLM and the state to evaluate the area for potential physical safety hazards. The 40 abandoned mine features included horizontal mine tunnel openings and deep vertical openings. BLM and the Nevada Division of Wildlife conducted cultural and wildlife surveys, respectively, to help determine appropriate closure methods. The state then filled the hazardous openings with foam and rock or installed gates that provide access to bats and desert tortoises. The local county government also contributed to the installation of the bat gates. Officials from the 13 states in our review estimated spending about $117 million in total, or an average of nearly $12 million annually, of nonfederal funds from fiscal years 2008 through 2017 to address physical safety and environmental hazards at abandoned hardrock mines within their states. Spending in three of the 13 states—California, Colorado, and Idaho—represented over 86 percent of the total nonfederal expenditures. Of the approximately $117 million, states spent about $26 million addressing physical safety hazards and about $91 million addressing environmental hazards. (See table 3.) State officials said that the sources of nonfederal funds that the states spent to address abandoned hardrock mines included (1) state-generated funds and (2) funding from settlements with responsible parties. State-generated funds. Officials from eight of the 13 states reported that they expended revenue raised by the state government to work on abandoned hardrock mines. Revenue sources include mine license taxes and royalties on oil and gas, hardrock mines, and other mineral extraction, and other sources such as the state general fund. For example, officials from the California Department of Conservation said the agency spent funds generated by state fees on active gold and silver operations to address physical safety hazards at abandoned mines on public lands. In addition, Colorado officials said they spent funds from a state severance tax collected on oil and gas, coal, metallic minerals, and other mineral production to address physical safety and environmental hazards. Settlements with responsible parties. Officials from five of the 13 states reported that they spent funds received from settlements with responsible parties to either conduct cleanup actions or oversee the responsible parties’ work to address environmental hazards. For example, from fiscal years 2008 through 2017, the state of New Mexico spent over $3.8 million that it had collected from responsible parties at two abandoned hardrock mine sites, according to state documents. Nevada and Washington officials said that their agencies’ expenditures to address environmental hazards during the 10-year period were entirely funded by collections from responsible parties. State officials we interviewed said they spent these nonfederal funds to address abandoned hardrock mines located primarily on private, county, state, or other nonfederal lands, including at mixed ownership sites. Officials from two of the 13 states (Colorado and Nevada) said they also spent state-generated funding to address hazards on federal land. Officials from the Nevada Division of Minerals’ abandoned mine program said that they generally spend about 80 to 90 percent of the program’s nonfederal funding addressing physical safety hazards on federal land. These officials explained that fees from unpatented mining claims on federal land are the division’s main funding source and, therefore, the state spends most of this funding to address hazards on federal land. Officials with the 13 states also told us that, in addition to spending about $117 million in nonfederal funds over the 10 years, states also spent more than $440 million they received from federal agencies, primarily through grants and cooperative agreements, during this period. Officials with seven states reported that they receive significantly more federal funds than nonfederal funds to work on abandoned hardrock mines and that federal funding is critical to addressing hazards at these mines. The Forest Service, BLM, the Park Service, and EPA estimated that their future costs to inventory and address physical safety and environmental hazards at abandoned hardrock mines would be in the billions of dollars. Each agency has generated some information about estimated future costs using a variety of methods and covering a range of activities. Given the level of uncertainty associated with the estimates, they likely understate the amounts that will be needed to comprehensively inventory and address these hazards. The Forest Service and BLM estimated that it could cost over $650 million to finish inventorying abandoned hardrock mines on lands they manage. Specifically, Forest Service information indicated it could cost about $147 million to complete the agency’s inventory, which includes identifying potential environmental hazards at 15,247 sites as well as the locations and conditions at approximately 13,000 sites not currently captured in a database. In addition, BLM officials estimated that it would cost about $510 million to complete the agency’s inventory of abandoned hardrock mines. This estimate includes about $130 million to evaluate approximately 66,000 features identified as posing an unconfirmed physical safety or environmental hazard. It also includes another $380 million to confirm the locations and presence of hazards at the approximately 380,000 additional features that may be on BLM-managed land but are not in its database. The Park Service and EPA did not provide estimates for future inventory work. Park Service officials said they have not estimated costs for additional inventory work because they believe that their inventory is largely comprehensive. EPA officials explained that the agency does not manage lands so they do not work to identify the existence of contaminated abandoned mines. Rather, EPA relies on external sources, such as state agencies and local governments, to alert it of potentially contaminated sites on nonfederal lands that may need attention. BLM and the Park Service estimated it could cost nearly $5 billion to address the physical safety hazards at abandoned hardrock mines on the lands they manage, and the Forest Service has not estimated this amount. Specifically, BLM estimated it could cost about $4.7 billion to fill in, gate, or otherwise address the nearly 65,000 features it has identified with confirmed and unconfirmed physical safety hazards and the estimated 380,000 additional features that are not yet included in the agency’s database. Park Service officials said they estimated that it would cost about $86 million to address the physical safety hazards at the abandoned hardrock mines identified in the agency’s database. These officials said that they plan to revise this estimate once they have better information about the actual costs to close the features where they are currently working. The Forest Service and EPA did not have estimates for addressing physical safety hazards. The Forest Service has not comprehensively estimated these costs, although the individual forests identify priority projects for spending each year, according to agency officials. EPA has not separately estimated costs to address physical safety hazards since those costs are included in its estimates to address environmental hazards. The Forest Service, BLM, the Park Service, and EPA have partly estimated costs to address environmental hazards at abandoned hardrock mines. Agency officials said that they do not have comprehensive estimates, in part because they have not yet selected the cleanup remedy at numerous sites—information they need to develop detailed estimates—nor have they identified all of the contaminated sites that will need to be addressed. The officials explained that a remedy to address an abandoned mine site with one waste rock pile (e.g., removing the pile from a creek and constructing a repository for it) is different from a remedy needed to address a site with perpetually draining mine tunnels, which could include operating and maintaining water treatment systems over the long term. As a result, the costs of cleanup remedies can vary from hundreds of thousands to hundreds of millions of dollars per site. Estimates of future costs to address environmental hazards at abandoned hardrock mines and what the estimates included varied by agency: Forest Service. Forest Service and USDA officials said that they estimated in 2014 that it could cost about $6 billion to address environmental hazards at 6,600 abandoned hardrock mine sites on Forest Service-managed land. This estimate includes costs to assess the extent of contamination, search for responsible parties, design and implement an action to remove a small waste rock or tailings pile, and monitor and maintain each site for 30 years after the cleanup is complete. According to the estimate, costs to maintain the completed sites make up half of the $6 billion in estimated future costs. These officials also said they assumed that all 6,600 sites are relatively simple and not complex with more extensive contamination. In developing this estimate, the Forest Service did not assume that responsible parties would cover any of these costs. BLM. BLM estimated a portion of the costs associated with addressing environmental hazards at abandoned hardrock mines on BLM-managed land, since BLM officials said there are too many unknowns and unique circumstances at each feature to comprehensively estimate total costs. These officials said the agency has estimated costs for some sites with confirmed environmental hazards in accordance with Interior’s environmental liabilities reporting guidance. Specifically, as of June 2019, BLM estimated that future costs to address environmental hazards at 105 abandoned hardrock mine sites on BLM-managed land range from $61 million to about $265 million. Interior and BLM officials explained that these costs do not represent all future costs needed to clean up these sites. Instead, the range includes the future costs that the agency determines are reasonably estimable at the time for these sites. In some cases, these costs are limited to the cost of conducting a study if the agency has not selected a cleanup remedy. As a result, officials said they expect that BLM’s estimate of total future costs will increase once the agency selects the cleanup remedies and estimates their costs. Officials also said they have not estimated future costs for sites where the agency has not determined the type or extent of the contamination or where BLM is not likely to fund the cleanup, for example, because a responsible party may pay for it. Park Service. Similar to BLM, Park Service officials estimated the future costs associated with addressing environmental hazards at 50 contaminated abandoned hardrock mines, based on Interior’s guidance. As of June 2019, the Park Service estimated that these future costs range from $21 million to $35 million, exclusive of any reimbursements from responsible parties. The Park Service did not estimate the future costs to address 19 additional sites that the agency identified as posing environmental hazards because either work at these sites is in the early stages, the agency was unable to estimate costs, or the Park Service is not likely to fund the cleanup, according to Park Service and Interior officials. EPA. EPA officials told us that they do not have a comprehensive estimate of costs to clean up hardrock mines. Specifically, officials said EPA tracks planned obligations to be incurred for sites where the agency anticipates taking action within the next 3 years to help support its budget development process. As of fiscal year 2018, EPA identified about $519 million in planned obligations for 115 hardrock mine or mineral processing sites. EPA officials said the planned obligations do not necessarily reflect the total estimated costs remaining at a site because the agency typically requires its regions to report known planned obligations for 3 years, or longer, if available. According to EPA data, future costs to address hardrock mines likely will exceed these obligations. For example, EPA did not report planned obligations for 423 mine and mineral processing sites where the agency has not completed site assessment work or selected a cleanup remedy. According to EPA officials, they generally do not plan obligations for future cleanup work while conducting an assessment. However, they said that if an assessment reveals a need for a time-sensitive response at a site, the agency may fund it. EPA officials also told us that they expect responsible parties to pay a portion of the future costs associated with these sites, but that amount is unknown. Federal agency officials, state officials from three selected states (Colorado, Montana, and Nevada), and stakeholders cited availability of resources and legal liability concerns as factors that limit efforts to identify, clean up, and monitor hazards at abandoned hardrock mines. Federal and state officials said their backlog of work on abandoned mines is greater than current staff and budget levels. In addition, state agency officials and other stakeholders we interviewed, such as nongovernmental organizations and mining companies, have limited their participation in projects to address environmental hazards at abandoned mines because of concerns about their potential legal liability under CERCLA and the Clean Water Act. All of the officials we interviewed from the Forest Service, BLM, the Park Service, and EPA, as well as from Colorado, Montana, and Nevada, cited availability of resources as a factor that limits their efforts to identify and address the physical safety and environmental hazards at abandoned hardrock mines. Representatives from state associations and nongovernmental organizations we interviewed also cited this factor as limiting federal and state efforts. Federal and state officials said that their backlog of work on these mines far exceeds their current staff and budget levels. For example, BLM officials estimated that with the agency’s current abandoned mine budget and staff resources, it could take up to 500 years to confirm the presence of physical safety or environmental hazards at the approximately 66,000 features in its database and the estimated 380,000 features not yet captured in its database. Officials from Colorado and Montana and representatives from a state association noted that these two states regularly receive reclamation funding from OSMRE to address abandoned coal mines in their states. As a result of having access to such funds, five states, including Montana and Wyoming, as well as three tribes have certified that they have addressed all of their known priority abandoned coal mines. These officials also noted that there is not a similar or consistent source of funding for states to address hazards at abandoned hardrock mines. In Nevada, although state-collected mining fees contribute to addressing safety hazards at abandoned hardrock mines, state officials said they do not have a consistent source of funding to address environmental hazards. As a result, Nevada officials explained that they tend to work primarily on mines where there is a viable responsible party to fund the cleanup. However, one official said that most of the approximately 190 abandoned hardrock mine sites in the state that pose or may pose environmental hazards do not have a viable responsible party. Federal and state agency officials described several steps they have taken to work more efficiently within existing limited resources. For example, federal agency officials said they prioritize proposed projects to address abandoned mines that pose the highest safety and environmental risks. In addition, federal officials explained that they have established several formal mechanisms for national and local collaboration to facilitate leveraging resources. For instance, federal and state officials working in Colorado said they formed a working group in 2010 to jointly identify and prioritize watersheds that have been contaminated by abandoned hardrock mines. The agencies work collaboratively to evaluate the extent of contamination in each watershed, leading to a more holistic approach to addressing contamination, according to EPA and Colorado state officials. Regional Forest Service officials we interviewed who also work outside of Colorado said the group is a national model for collaboration and efficient use of resources. Forest Service, BLM, Park Service, EPA, and state officials also said that they work to leverage federal and state resources by searching for responsible parties to contribute funding to their efforts at abandoned hardrock mines. However, officials told us that identifying such parties is difficult and can be resource intensive given the length of time that has elapsed since the mines were abandoned and the lack of a clear chain of custody and land ownership boundaries at mine sites. All of the state officials and nearly all of the stakeholders from nongovernmental organizations, state associations, and industry we interviewed cited concerns over legal liability—that is, being held legally responsible for addressing environmental contamination—as a factor that limits efforts to address certain abandoned hardrock mine hazards on nonfederal land. Specifically, liability concerns can prevent third parties— entities who offer assistance in addressing environmental hazards that they did not create and are not legally required to clean up—from taking actions to help address such hazards that are on private land and on nonfederal portions of mixed ownership sites. These parties are often referred to as Good Samaritans and may include state agencies, nongovernmental organizations, local governments, private landowners, and mining companies, among others. Federal and state officials and stakeholders we interviewed said that Good Samaritans have avoided taking certain cleanup actions—in particular, addressing mine tunnels that perpetually drain highly contaminated water—at abandoned hardrock mines because they are concerned about potentially being held legally responsible under CERCLA and the Clean Water Act. Specifically, a Good Samaritan undertaking cleanup actions at an abandoned hardrock mine might become a responsible party under CERCLA and thereby would be responsible for the entire cost of cleaning up the site. As a result, representatives from an industry association and a nongovernmental organization told us that while they are interested in addressing contamination on private land in the West, they generally have not done so, in part because of concerns about becoming responsible under CERCLA for cleaning up all of the contamination present at the site. In addition, a Good Samaritan undertaking cleanup actions to address draining mine tunnels may be required to do so in accordance with a discharge permit under the Clean Water Act. Complying with such a permit requires that the cleanup meet and maintain water quality standards, which can be expensive and may require perpetual water treatment. State officials and stakeholders explained that meeting and maintaining such standards at certain mines is difficult because of naturally occurring heavy metals and continual drainage from the mines. They said they are interested in undertaking smaller-scale projects to address mine tunnel drainage that may significantly improve water quality and aquatic habitat but would not fully meet water quality standards. However, Colorado and Montana state officials and various stakeholders said they generally decide not to undertake such projects, even if they could make incremental improvements, because of the risk of being held responsible for meeting and maintaining water quality standards in perpetuity. To encourage nongovernmental organizations, other stakeholders, and states to participate in abandoned hardrock mine projects at mixed ownership sites and on other private land, EPA developed administrative tools aimed at limiting Good Samaritans’ CERCLA and Clean Water Act liability. In 2007, EPA developed guidance for issuing “comfort/status letters” to Good Samaritans willing to perform cleanup work under EPA oversight and for entering into settlement agreements—legally enforceable documents signed by EPA and a Good Samaritan that include a federal covenant not to sue under CERCLA in exchange for cleanup work. In 2012, EPA also issued guidance stating that, as a general matter, the agency would not require a Good Samaritan to obtain a Clean Water Act discharge permit if they successfully complete a cleanup action under a comfort/status letter or settlement agreement with EPA. Good Samaritans have participated in some projects at abandoned hardrock mines using EPA’s administrative tools. As of January 2020, EPA had issued four comfort letters and entered into three settlement agreements, generally to address hazards at sites that did not require a Clean Water Act permit. Some state officials and stakeholders we interviewed said they have not pursued using EPA’s administrative tools because, in part, these tools do not sufficiently alleviate liability under the Clean Water Act. For example, they explained that the tools and guidance provide reassurance that EPA may not sue the Good Samaritan but do not ensure that certain outside parties will not sue to require they meet water quality standards. State officials and stakeholders we spoke with said that they believe that resolving the concerns over CERCLA and Clean Water Act liability may require federal legislation. However, other stakeholders expressed concerns that legislative changes, such as amending CERCLA or the Clean Water Act, could inadvertently result in weakening the existing environmental protections in these and other laws or could limit the ability of outside parties to enforce their provisions. Since 1999, several bills have been introduced that would have responded to liability concerns but as of December 2019, none had been enacted. State officials and stakeholders have been involved in efforts to draft legislation that would address liability concerns, but the interested parties have disagreed about the specific provisions to include. While federal agency officials did not cite liability concerns as a factor that limits their agencies’ efforts to address abandoned hardrock mines on lands under their jurisdictions, Forest Service, BLM, and EPA officials concurred that legal liability concerns deter Good Samaritans from participating in projects with federal agencies at mixed ownership sites. Federal officials explained that, unlike Good Samaritans, the abandoned hardrock mines the federal agencies address are under their jurisdiction and the agencies are already responsible for meeting the requirements of CERCLA and other applicable laws. However, federal agency officials have observed the effects of Good Samaritan legal liability concerns on projects. For example, Forest Service officials in Colorado said that potential partners have expressed interest in addressing contamination on the private land portions of mixed ownership sites but declined once they learned they would be subject to liability under CERCLA. In the absence of legislative changes, EPA officials said they are looking for new ways to encourage Good Samaritan participation in abandoned hardrock mine projects. For example, they are working to update and refine the agency’s administrative tools and identify new solutions to better address Good Samaritans’ concerns. They are also looking to encourage Good Samaritan participation in more projects that would not require a Clean Water Act permit, such as moving mine tailings piles away from streams. We provided a draft of this report to the Department of Agriculture, the Department of the Interior, and EPA for their review and comment. The Forest Service Audit Liaison provided comments by email, stating that the Forest Service generally agreed with the report. USDA and EPA provided technical comments, which we incorporated as appropriate. Interior told us they had no comments. As agreed with your office, unless you publicly announce the contents of this report earlier, we plan no further distribution until 30 days from the report date. At that time, we will send copies of this report to the appropriate congressional committees, the Secretaries of Agriculture and the Interior, the Administrator of EPA, and other interested parties. In addition, the report will be available at no charge on the GAO website at http://www.gao.gov. If you or your staff have any questions about this report, please contact me at (202) 512-3841 or fennella@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. GAO staff who made key contributions to this report are listed in appendix III. This report describes (1) what is known about the number of abandoned hardrock mines in the United States; (2) federal and state agency expenditures to address abandoned hardrock mines from fiscal years 2008 through 2017, and what is known about future costs to address these mines; and (3) factors that limit federal and state agencies’ and stakeholders’ efforts to address abandoned hardrock mines. To address these objectives, we reviewed our previous work on abandoned hardrock mines, including a March 2008 report in which we summarized information about the number of abandoned hardrock mines in the United States and the amount of federal spending on these mines from fiscal years 1998 through 2007. We also reviewed federal agency reports to identify the federal agencies that track numbers of abandoned hardrock mines, conduct work to address hazards at these mines, or fund projects to address these hazards. We identified the U.S. Department of Agriculture’s (USDA) Forest Service; the Department of the Interior’s Bureau of Land Management (BLM), National Park Service (Park Service), and Office of Surface Mining Reclamation and Enforcement (OSMRE); and the Environmental Protection Agency (EPA) to include in our review. We reviewed agency documents detailing these agencies’ cleanup efforts and abandoned hardrock mine programs. We also selected 13 western states to include in our review: Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington, and Wyoming. We selected these states because our March 2008 report and other federal and state agency reports indicated that most of the abandoned hardrock mines are in these states. We conducted two site visits to abandoned hardrock mines in Colorado in February 2019. We selected sites in Colorado because they provided opportunities to observe examples of physical safety and environmental hazards on federal and nonfederal lands. We visited sites with physical safety hazards that BLM and the state had addressed on BLM and county lands. We also visited a National Priorities List site where EPA and the state were addressing environmental hazards on private land. To describe what is known about the number of abandoned hardrock mines in the United States, we obtained and summarized information about abandoned hardrock mine features and sites—including the number of features and sites that pose confirmed and unconfirmed physical safety and environmental hazards—that the Forest Service, BLM, the Park Service, and EPA maintained in databases as of May 2019, the most current at the time of our review. Specifically: the Forest Service provided information about abandoned hardrock mine sites from USDA’s National Environmental Accomplishment Tracking system; BLM provided information about abandoned hardrock mine features from the Abandoned Mines and Site Cleanup Module; the Park Service provided information about abandoned hardrock mine sites and features from the Abandoned Mineral Lands Data Entry and Edit database and from Interior’s Environmental and Disposal Liabilities list; and EPA provided information about hardrock mining and mineral processing sites from its Superfund Enterprise Management System. In addition, we obtained information on the agencies’ estimates of the number of additional abandoned hardrock mine sites or features that are not captured in their databases, where applicable. We assessed the reliability of the agencies’ databases by testing the data for accuracy by cross-referencing with relevant data sets and checking for missing data and errors. We also reviewed agency documents about the databases and our previous related work regarding the use of these data. We also interviewed headquarters officials from each agency and discussed the data and any limitations. We determined that the information in the agencies’ databases about the number of abandoned hardrock mines was sufficiently reliable to summarize in our report. We calculated the agencies’ total number of abandoned hardrock mines in terms of the number of features. According to agency officials, many abandoned hardrock mine sites contain more than one feature, but there is no agreed-upon average number of features per site. Since the Forest Service and EPA reported information only by mine site, we counted the minimum of one feature per site in our calculations. As a result, the total number of features likely is underestimated. Further, we collected information about the number of abandoned hardrock mines in the 13 western states through semi-structured interviews with state officials. For each state, we interviewed officials with the relevant state agencies that address abandoned hardrock mines through, for example, a dedicated abandoned mine program or a broader program focused on addressing environmental hazards. In each interview, we asked the officials to provide information about the numbers of abandoned hardrock mine sites they identified in their state, features that posed a hazard to public health and safety, and features that caused environmental degradation as of the time of our review. We provided the states with a common definition of abandoned mine site and feature. However, officials with five states provided information only for abandoned mine sites and not features. For those states, we counted the minimum of one feature per site to calculate the states’ total number of abandoned hardrock mine features. As a result, the states’ total number of features likely is underestimated. We assessed the reliability of the states’ information by reviewing documents about the data systems, checking for missing data and errors, and discussing the data and their sources with state officials, including any limitations. We determined that the data were sufficiently reliable to describe what the state agencies know about abandoned hardrock mines within their jurisdictions. To describe federal agency expenditures to address abandoned hardrock mines from fiscal years 2008 through 2017, we summarized expenditure information from the Forest Service, BLM, the Park Service, EPA, and OSMRE for this time period, the most recent 10 years of information available at the time of our review. Specifically, we collected information about total expenditures to address abandoned hardrock mines, expenditures to address physical safety hazards, expenditures to address environmental hazards, and expenditures of collections from responsible parties under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as applicable. We assessed the reliability of the agencies’ information by testing the data for accuracy and completeness by checking for missing data and errors. We also reviewed our previous related work regarding the use of the information and interviewed agency officials involved with collecting or analyzing the information. We determined that the information obtained from the agencies was sufficiently reliable for our descriptive purposes. Additional details on agency-specific information we used follows: Forest Service. The Forest Service provided expenditure information for fiscal years 2008 through 2017 for its Abandoned Mine Land and Environmental Compliance and Protection programs from its Foundation Financial Information System. The Forest Service also provided information from this system about expenditures of reimbursements from responsible parties. USDA provided information about the Forest Service’s expenditures from the department’s Hazardous Materials Management Account for fiscal years 2008 through 2017 from the Financial Management Modernization Initiative system. BLM. BLM provided expenditure information from Interior’s Financial Business Management System for fiscal years 2009 through 2017. BLM’s budget office provided expenditure information for fiscal year 2008 since information prior to fiscal year 2009 is not included in Interior’s current financial system. BLM provided information about abandoned hardrock mine expenditures from relevant subactivity codes, including Abandoned Mine Lands, Hazardous Materials Management, American Recovery and Reinvestment Act-Abandoned Mine Land projects, and Central Hazardous Materials Fund, among others. Park Service. The Park Service provided expenditure information from Interior’s Financial Business Management System and the Park Service’s Project Management Information System and Administrative Financial Systems 3 and 4 for fiscal years 2008 through 2017 for its Abandoned Mine Lands program and the Contaminants Cleanup Branch. The Park Service also provided information from Interior’s system about expenditures of reimbursements from responsible parties. OSMRE. OSMRE provided expenditure information from Interior’s Financial Business Management System for fiscal years 2008 through 2017 from its non-coal account, which includes spending for projects to address abandoned hardrock mines, non-hardrock abandoned mines, and other eligible projects. To further narrow the non-coal account expenditures to spending on abandoned hardrock mines, we reviewed information for projects that states completed during the 10-year period and eliminated expenditures that were clearly identified for non-hardrock-related projects. We also compared the expenditure information from OSMRE with expenditure information we obtained during our semi-structured interviews with officials from six state agencies that reported spending OSMRE grants specifically on hardrock abandoned mines—Alaska, Colorado, New Mexico, Montana, Utah, and Wyoming. We determined that Alaska’s and Colorado’s reported expenditures were more specific to abandoned hardrock mines than the information OSMRE provided for those states. As a result, we used Alaska’s and Colorado’s information to report expenditures for those states and used OSMRE’s information to report expenditures for all other states. OSMRE officials agreed with this approach. EPA. EPA provided information about the Superfund program’s expenditures at mine and mineral processing sites from the Integrated Financial Management System for fiscal years 2008 through 2011 and the Compass Financial System for fiscal years 2012 through 2017. EPA provided expenditures from its (1) Superfund appropriation accounts, (2) special accounts through which EPA receives resources from settlements with responsible parties for EPA to conduct site- specific work, and (3) state cost-share accounts, through which states contribute 10 percent of costs for EPA’s Superfund-financed remedial actions. EPA also reported expenditures of funds provided by other federal agencies; we excluded these expenditures from our reporting of EPA’s spending to avoid potential double counting. Further, we obtained information through our semi-structured interviews with officials from the 13 selected states about their expenditures of nonfederal and federal funds at abandoned hardrock mines for state fiscal years 2008 through 2017. We obtained and summarized information on total expenditures to address abandoned hardrock mines, expenditures to address physical safety hazards, and expenditures to address environmental degradation. We also obtained information about the sources of the agencies’ funding, such as collections from responsible parties. The states provided expenditure information by state fiscal year and not federal fiscal year because their financial systems are organized by state fiscal year. We assessed the reliability of the states’ expenditure information by testing for missing data and errors, reviewing documents, and discussing the information and any limitations with state agency officials. Three states were unable to provide expenditure information specific to abandoned hardrock mines for the entire 10-year period. Therefore, we discussed and agreed with each of these states how they could provide information that most closely responded to our request—for example, by providing information for the years that were available—and we are reporting the state agencies’ total expenditures as estimates. We determined that the data were sufficiently reliable to describe an estimate of how much in nonfederal and federal funds the state agencies spent to address abandoned hardrock mines. We are reporting both federal and state agency expenditures in nominal dollars. We are doing so for several reasons, including that there was a relatively low rate of inflation from fiscal year 2008 through 2017 (about 1.5 percent per year, on average); not all states reported annual expenditures that could be adjusted for inflation; and federal and state agencies reported annual expenditures differently, with federal agencies reporting by federal fiscal year and state agencies reporting by state fiscal year. To describe what is known about future costs to address abandoned hardrock mines, we reviewed and summarized documentation of the federal agencies’ most recently available estimates of costs to inventory additional abandoned hardrock mine features and to address physical safety and environmental hazards that have not been addressed. We discussed these estimates, and the assumptions used to create the estimates, with relevant agency officials. We describe the estimates and their underlying assumptions in the report. To identify factors that limit federal and state agencies’ and stakeholders’ efforts to address abandoned hardrock mines, we reviewed relevant agency documents and independent reports that describe limiting factors. We interviewed federal agency officials, state agency officials, and stakeholders. More specifically, we interviewed Forest Service, BLM, Park Service, EPA, OSMRE, and Interior headquarters officials and officials from these agencies’ regional or state-based offices who work in Colorado, Montana, and Nevada. We also interviewed officials with the relevant state agencies that address abandoned hardrock mines in these three states. We selected these states for geographic diversity, higher numbers of abandoned hardrock mines, and variation in the types of hazards posed by abandoned hardrock mines in these states. The sample of states is not generalizable, and the results of our work do not apply to all states where abandoned hardrock mines are located, but provide illustrative examples. In addition, we obtained perspectives from stakeholders that have participated in or expressed interest in participating in projects to address abandoned hardrock mines. We interviewed a sample of stakeholders, selected to provide perspectives from industry associations, nongovernmental organizations, state agency associations, and individuals with long-standing involvement in issues related to addressing abandoned hardrock mines. We identified and selected these stakeholders based on our previous work, including the stakeholders we interviewed for our March 2008 report; a review of relevant literature, including written testimony statements and a summary of proceedings from a 2018 conference on abandoned hardrock mines; interviews with federal and state agency officials; and recommendations from stakeholders. Our sample of stakeholders is not generalizable to all stakeholders involved with abandoned hardrock mines, but provides perspectives on factors that limit efforts to address abandoned hardrock mines. In total, we obtained responses from officials with 13 federal agency offices, including six headquarters offices and seven regional or state- based offices; officials with three states; and representatives of 11 stakeholder organizations, including three state associations that represent states with abandoned mine programs, two nonprofit conservation organizations, two mining industry associations, one mining company, and three individuals with long-standing involvement in abandoned hardrock mine policy. In our discussions, officials and representatives with each entity identified the factors that limit their or others’ efforts to address abandoned hardrock mines. We reviewed the responses and identified the factors that officials and stakeholders in each group (i.e., federal agencies, state agencies, and stakeholders) frequently mentioned. Two factors arose frequently both within and across the groups—we describe these factors in our report. We conducted this performance audit from June 2018 to March 2020 in accordance with generally accepted government auditing standards. Those standards require that we plan and perform the audit to obtain sufficient, appropriate evidence to provide a reasonable basis for our findings and conclusions based on our audit objectives. We believe that the evidence obtained provides a reasonable basis for our findings based on our audit objectives. Table 4 includes expenditures to address abandoned hardrock mines for the Bureau of Land Management, Environmental Protection Agency, Forest Service, Office of Surface Mining Reclamation and Enforcement, and National Park Service. In addition to the contact named above, Elizabeth Erdmann (Assistant Director), Leslie Kaas Pollock (Analyst-in-Charge), Matthew Elmer, William Gerard, Anne Rhodes-Kline, Sheryl Stein, Sara Sullivan, and Rajneesh Verma made key contributions to this report.

Summary: The General Mining Act of 1872 allowed individuals to obtain exclusive rights to valuable hardrock mineral deposits on land belonging to the United States. Miners explored, mined, and processed valuable minerals, but many did not reclaim the land after their operations ended. Unsecured mine tunnels, toxic waste piles, and other hazards—known as mine features—are found at abandoned hardrock mines across federal and nonfederal lands. The Forest Service, BLM, National Park Service, EPA, and OSMRE—as well as state agencies—administer programs that identify and address hazardous features at abandoned hardrock mines. Addressing features could include, for example, sealing mine tunnels or treating contaminated water. GAO was asked to provide information about abandoned hardrock mines. This report describes (1) what is known about the number of abandoned hardrock mines in the United States; (2) agency spending to address abandoned hardrock mines from fiscal years 2008 through 2017 and estimated future costs; and (3) factors that limit federal and state agencies' and stakeholders' efforts to address abandoned mines. GAO obtained and summarized information from agency databases about the number of abandoned mines, features, and hazards as of 2019; summarized agency spending data from fiscal years 2008 through 2017, the most currently available; and interviewed federal and state agency officials and stakeholders, selected to provide diverse perspectives. The U.S. Department of Agriculture's Forest Service, the Department of the Interior's Bureau of Land Management (BLM) and National Park Service, and the Environmental Protection Agency (EPA) identified at least 140,000 abandoned hardrock mine features, such as a tunnel, on lands under their jurisdictions. Of these, about 67,000 pose or may pose physical safety hazards—danger of injury or death—and about 22,500 pose or may pose environmental hazards—risks to human health or wildlife from long-term exposure to harmful substances. Agency officials also estimated there could be more than 390,000 abandoned hardrock mine features on federal land they have not captured in their databases, and agencies are developing more comprehensive information about these mines. Forest Service, BLM, National Park Service, EPA, and Interior's Office of Surface Mining Reclamation and Enforcement (OSMRE) spent, on average, about $287 million annually to address physical safety and environmental hazards at abandoned hardrock mines from fiscal years 2008 through 2017, for a total of about $2.9 billion (see figure). Of this total, the agencies spent about 88 percent ($2.5 billion) addressing environmental hazards, and about $1 billion was reimbursed by private parties, such as former mine owners. Federal officials also estimated that it would cost billions more to address these mines in the future. Nearly all of the federal and state agency officials and stakeholders GAO interviewed cited availability of resources and legal liability concerns as factors that limit efforts to address hazards at abandoned hardrock mines. Federal and state officials said their backlog of work is greater than what can be done with available staff and budgets, but they have taken steps to collaborate to help leverage resources. State officials and stakeholders, such as conservation groups, said they want to help address environmental hazards that they did not cause at abandoned hardrock mines. However, they generally do not do so because they are concerned about becoming legally responsible for the entire cost of addressing contamination at an abandoned mine if they attempt partial cleanup. EPA officials said they are considering new ways to encourage volunteer participation, in addition to existing administrative tools.