On August 5, 2015, an accidental spill from the Gold King Mine, a long-abandoned gold mine site in Colorado, released an estimated three million gallons of acid mine drainage (AMD) wastewater into a tributary of the Animas River. From there, the contaminated wastewater migrated downstream to the San Juan River into New Mexico, Utah, and tribal lands. Water samples taken in days immediately after the mine blowout indicated elevated levels of some metals (copper, lead, and manganese), although concentrations diminished to "pre-incident" levels as the plume moved downstream. Nevertheless, the spill led to widespread concern about impacts on water quality, public health, agriculture, fish, and wildlife. It also raised concern about other inactive or abandoned hardrock mine (IAM) sites on public and private lands in the United States. Mining has been conducted throughout the country for nearly 150 years, but most occurred before the advent of environmental regulation. Many historic mining operations were abandoned without being adequately reclaimed or safeguarded against future environmental damage. There may be more than 550,000 of these sites on public and private lands in the United States; there is no single inventory of sites, and thus the precise number is unknown. The Government Accountability Office ( GAO ) estimated that there may be more than 160,000 abandoned hardrock mines in the western states and Alaska and that 20% of these sites (about 33,000) had degraded the environment outside the mine. Although most sites do no t pose environmental problems, drainage or runoff from some continue to pose a threat to both surface water and groundwater. The Environmental Protection Agency (EPA) estimated in 2000 that approximately 40% of headwaters in rivers and streams in the West, which are the source of drinking water for thousands of persons, have been impacted by discharges from abandoned hardrock mines, thus threatening community and agricultural water supplies, increasing drinking water treatment costs, and limiting fishing and recreation. The number of mines that are causing or have potential to harm the environment is unknown, but is generally believed to be a small percentage of the total: perhaps 5%-10% of all IAM sites. But even so, 5%-10% of 500,000 possible sites still represents a large number of potential sites (25,000 to 50,000) that concerns many persons. The Colorado spill has raised interest in facilitating cleanup of legacy pollution at IAM sites in order to prevent similar accidents. One approach that has drawn attention is encouraging remediation by so-called "Good Samaritan" entities, third parties who have no history of polluting at a particular site or legal responsibility for its pollution, but who step forward to clean up AMD or other historic mine residue of pollution. Legislation to authorize Good Samaritan remediation has been introduced regularly since 1999, including H.R. 963 , H.R. 3843 , and a Discussion Draft bill in the 114 th Congress. These bills propose incentives in the form of reduced liability from environmental laws (such as strict liability for cleanup costs and restoring damaged natural resources) and less stringent environmental standards applicable to cleanup activities. Proponents, who include mining companies, industry associations, and some conservation groups, maintain that any degree of cleanup is better than inaction or the status quo, and they argue that, if not addressed in this legislation, the issues of liability exposure under environmental law and strict regulatory standards will continue to stymie voluntary cleanups. Opponents, especially many environmental and conservation advocates, acknowledge that cleanup would benefit the environment, but they express concern that exemptions and relief might be the first step in dismantling key environmental legislation, due to vague standards that would apply to a Good Samaritan cleanup. Other stakeholders in the debate include states (many, especially in the West, support the idea of facilitating cleanup of abandoned mines) and the federal government. H.R. 963 , H.R. 3843 , and the Discussion Draft propose to establish a process for issuing permits to those who would be Good Samaritans. Permitting authority would vest in EPA, but could be delegated to qualified states and Indian tribes. The bills would allow a potential remediating party to obtain a permit authorizing it to take steps to improve water quality without being required to comply fully with water quality standards that would otherwise apply. The bills would establish a process for identifying what entities and lands are eligible, specifying goals of cleanup and conditions for permits, and issuing permits. The bills reflect several differences, as well. H.R. 963 is drafted as a measure that would amend the Clean Water Act (CWA, 33 U.S.C. §1251 et seq.). Under this bill, the permit provision would be part of the CWA's overall regulatory, permitting and enforcement mechanism. The CWA prohibits the discharge of pollutants into the nation's waters without authority under a CWA permit, and H.R. 963 would amend the act's principal permit provision, called the National Pollutant Discharge Elimination System permit (NPDES, Section 402, 33 U.S.C. §1342), by adding a new subsection with requirements specific to Good Samaritan permits. This bill includes a dedicated cleanup fund for abandoned hardrock mines from a royalty fee on minerals taken from public lands. In contrast, H.R. 3843 and the Discussion Draft are stand-alone bills. These bills propose Good Samaritan relief from requirements of the CWA and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, or Superfund, 42 U.S.C. §9601 et seq.). Neither includes dedicated funds for IAM cleanups. Proponents of Good Samaritan legislation have discussed issues related to proposals since bills were first introduced in the 106 th Congress. In the 109 th Congress, a number of bills were introduced (including one supported by the Administration), and a Senate committee reported legislation, but no further activity occurred. Bills were introduced in each subsequent Congress, as well. With apparent renewed interest in the 114 th Congress, the current legislation reflects concepts from a number of earlier proposals, with some refinements and modifications. Senate and House committees have held oversight hearings on the Gold King Mine spill and hearings to review legislative responses to it, including bills that seek to overcome obstacles to potential Good Samaritans. This report discusses several issues that have drawn attention: eligibility for a Good Samaritan permit, minerals covered by a permit, standards applicable to a Good Samaritan cleanup, scope of liability protection, funding, treatment of revenues from cleanup, enforcement, the appropriate implementation role for states and Indian tribes, terminating a permit, and sunsetting the permit program. This discussion does not address every issue in the current bills (for example, it does not analyze procedures for issuing Good Samaritan permits), nor does it discuss general background on the problem of inactive and abandoned mine sites. The issue of permit eligibility concerns the universe of parties who may undertake IAM cleanup under a Good Samaritan permit. It has several aspects, including whether Good Samaritans should be limited to government entities or may also include the mining industry and others in the private sector, and how the legislation specifies that anyone with existing or prior responsibility for environmental pollution at the site is restricted from eligibility for the liability and regulatory relief exemptions provided by a Good Samaritan permit. Some, especially conservation groups, argue that a Good Samaritan should only be working on behalf of the public welfare, meaning that remediation actions must be entirely governmental. Government, it is argued, unlike commercial or philanthropic enterprises, seeks to balance the needs and desires of society's many competing interests, and government agencies are accountable to elected politicians and ultimately to the public. According to this view, there is concern that if private entities are allowed to get involved in remediation, and profits from the activity are generated, the Good Samaritan's motives could be less focused on cleanup. Such opponents contend that, if the point of the legislation is cleanup, eligibility should be limited, so that questions of monetary awards and profit do not arise. Further, in practical terms, some argue that the more expansive the range of possible eligible parties allowed under the legislation (especially if the private sector is included), the more complicated and controversial the legislation becomes. Industry groups, on the other hand, argue that mining companies have the resources, knowledge, and technology to assess and remediate IAM sites. Industry believes that an existing company that is not responsible for creating an abandoned site should not be precluded from being a Good Samaritan. If such entities are not allowed to participate under a Good Samaritan permit, they say, fewer sites will be cleaned up, because companies will not risk the potential liability of a voluntary cleanup (see discussion below ). The more the legislation is broadened in terms of eligibility, the more Good Samaritans will step forward, they say. H.R. 963 and the Discussion Draft include an expansive listing of parties eligible for a Good Samaritan permit, presumably on the theory that a broad list would include more entities with resources and expertise to undertake cleanup. Under H.R. 963 and the Discussion Draft, a person eligible to apply for a Good Samaritan permit could include an individual; private entities (a firm, corporation, partnership, consortium, commercial entity, or joint venture); a nonprofit organization; commission; federal, state, interstate, or local government; or Indian tribe. H.R. 3843 does not include a similar list of eligible entities, but instead bases permit eligibility on the bill's definition of a Good Samaritan. Under H.R. 3843 , a Good Samaritan could be a person that has an ownership interest in the IAM site, so long as the person did not create or cause pollution related to the historic mine residue or is not liable or potentially liable for remediation costs.