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How CERCLA works

Many people find the remedy and restoration process under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund, to be confusing, complex, and full of legal jargon. This page contains a simplified, plain-English description of the process, to help interested persons gain a general understanding of how CERCLA works. If you would like more information about the CERCLA process, the U.S. Environmental Protection Agency (EPA) has additional CERCLA information on its website at The State of Montana’s Superfund counterpart is the Comprehensive Environmental Cleanup and Responsibility Act (CECRA), and additional information on CECRA can be found on the MDEQ website at

What is CERCLA

It has been nearly forty years since the U.S. Congress enacted the Comprehensive Environmental Response, Compensation and Liability Act of 1980, 42 U.S.C. §§ 9601 et seq. (CERCLA, also known as Superfund) to enable the federal government to cleanup and abate contamination at thousands of sites across the nation.

CERCLA was enacted in response to growing public concern about environmental contamination, the belief that people who caused the problem should pay to clean it up, and a perception that federal government action was needed to protect the public from waste that was abandoned, uncontrolled and a potential hazard to people, wildlife or habitat.

CERCLA created a federal program to identify sites where hazardous substances have been released into the environment, and to prioritize them for investigation and remediation. The statute requires parties responsible for that contamination to perform and/or pay for remedies that are necessary to protect human health and the environment. CERCLA remedies are commonly used to remove, collect and treat, and contain contamination in soil, water and groundwater. At some sites, remedies are also needed to clean portions of buildings, pipelines, and other structures. The goal of a CERCLA remedy is to protect people, wildlife and the environment from exposure to unsafe levels of contaminants—not to return a site to the condition it was in at some time in the past.

CERCLA has a second program to restore or compensate for damage to wildlife, habitat, and other natural resources that occurred in the past, or that may exist in the future after the remedy is in place. It authorizes federal, state and tribal trustees who own, control or manage natural resources to: i) identify and quantify damage to natural resources that results from a liable party's release of a hazardous substance, rather than other causes; ii) consider how the remedy will impact the damaged resources; and iii) develop restoration projects to restore, replace, or compensate for lost resources that the remedy will not restore or replace.

Trustees are the only persons authorized to bring claims for natural resource damages. The restoration projects they select must be feasible, cost effective, and able to wholly or partially restore, or replace, or acquire equivalent resources to substitute for, the lost resources. 43 C.F.R. 11.82.

"Loss" is measured by looking at the condition the natural resource would be in, if the hazardous substance contamination had not occurred. In urban areas where streams have been channelized and moved to make room for streets and highways, and land has been filled, paved, and developed, the CERCLA restoration program is not intended to remove those developments. CERCLA looks at the condition the resources would be in with those structures in place.

How Does CERCLA Work

CERCLA authorizes the U.S. President or the agency designated by the President – in most cases, the EPA—to identify contaminated areas that present significant risks to public health or the environment, and to place those areas on a “National Priority List” (NPL) for further investigation and attention. CERCLA, 42 U.S.C. 9605(a).

Once a site is placed on the NPL, EPA (or the designated agency) has authority to investigate the contamination, identify and evaluate potential remedies, and ultimately select a remedy to remove, contain, and/or collect and treat that contamination.

At most sites this process begins with a Remedial Investigation (RI) to determine the nature and extent of contamination, followed by a Feasibility Study (FS) to evaluate the available cleanup options. CERCLA, 42 U.S.C. § 9605 and 40 CFR Part 300.430.

Once EPA has identified a preferred environmental remedy, it publishes a proposed plan that describes the contamination, the cleanup options, and the preferred remedy for public review and comment. There are nine criteria that EPA uses to evaluate and choose the most appropriate remedy for the site. Three of these are mandatory, meaning that EPA must select a remedy that:

  • Protects human health and the environment;
  • Is cost effective and technically feasible; and
  • Achieves relevant and appropriate cleanup standards. If a standard is not technically feasible to attain, EPA may select another standard that is feasible to achieve, and that will protect public health and the environment.

CERCLA, 42 U.S.C. § 9621. EPA also considers whether the remedy will reduce waste volume, toxicity or mobility where feasible, and it looks at how effective the remedies will be over the short and long term. Final CERCLA remedies are intended to be permanent and sustainable in the future.

In addition, EPA reviews all remedy comments it receives during the public comment process, and evaluates the extent of State and community acceptance for the preferred remedy. In response to concerns raised in the public comment process, EPA may make necessary changes that are consistent with CERCLA’s remedy selection criteria. CERCLA, 42 U.S.C. § 9621.

Once the public comment and review process is complete, EPA issues a Record of Decision (ROD) that identifies the remedy it has selected. The ROD explains why the remedy has been chosen, describes the cleanup requirements that EPA seeks to achieve, and specifies the technologies and methods that will be used to complete the remedy. The ROD also includes a summary of public comments on the various remedy options, and EPA’s responses to those comments. CERCLA, 42 U.S.C. 9617.

Who Performs and Pays for Remedies

One of CERCLA's goals is to make the "polluter pay" for environmental remediation at most of the approximately 1,800 sites that have been placed on the NPL, and at most of the approximately 40,000 sites that are eligible for cleanup under CERCLA throughout the nation. For additional CERCLA site statistics, see; CERCLA, 42 U.S.C. Sections 9604, 9606 & 9607.

To find persons who are responsible for contamination, EPA searches public records and other information, often going back for decades, to identify current and former site owners, tenants, and other persons who have conducted activities on the property or in the area. Under CERCLA, the persons who are potentially responsible for environmental remedies include:

  • Current owners or operators of contaminated property, or
  • Former owners or operators at the time when hazardous substances were disposed on site, or
  • Persons who generated and arranged to dispose of hazardous substances and wastes found on site, or
  • Person who transported hazardous substances and wastes for disposal on site.

CERCLA, 42 U.S.C. 9607(a)(1)-(4). Liability under CERCLA is strict, retroactive, and may be joint and several in some circumstances, with a very limited number of defenses. What does this mean?

  • Strict liability means EPA does not need to show that a responsible party acted in a careless manner or with intent to pollute. A responsible party may be liable under CERCLA even if it has consistently complied with every law and regulation in place at the time of waste disposal.
  • Retroactive liability means that CERCLA applies to activities that occurred before CERCLA was enacted. At sites like Butte Priority Soils, it applies to activities that occurred more than a century before CERCLA was enacted, even before Montana became a state.
  • Joint and several liability means that one or more responsible parties may be asked to perform and pay for a remedy for contamination that is commingled with waste released by another person, including persons who no longer exist or who are not able to pay their fair share of the remedy costs.

There has been some discussion among regulators, elected officials, industry, environmentalists and others, about whether this system fairly allocates responsibility for contamination released long ago. Most of this debate has focused on who should pay for the cost of cleaning up pollution caused by persons who are deceased, companies that are defunct or dissolved, and entities that no longer exist. See Superfund Deskbook, 2d Edition, by A. Rumsey & M. Daneker (Environmental Law Institute 2014).

A related debate arises when a party seeks to distinguish its own waste from other waste at a site, based on waste type, location, volume, or other features that makes it unique and "divisible" from other wastes. If a party can prove its waste is distinguishable or "divisible" from the other wastes, it may be able to limit its liability to remedy costs arising from its own portion of the site or waste. Burlington Northern and Santa Fe Railway Co. v. United States, 556 U.S. 599 (2009).

At sites where multiple parties have each contributed to the contamination in different ways, it is also common for two or more parties to enter into agreements that allocate certain remedy work and costs between or among themselves. The allocation may be based on the type, volume or location of waste that each party contributed, or on other facts that establish each party's fair share of the waste or the remedy to address it.

All of these concerns arise at a site like Butte Priority Soils, where many persons contributed to metal contamination on the hillsides, in the creek corridor, and in the groundwater over more than a century. EPA has identified several "potentially responsible parties" (PRPs), including:

  • Atlantic Richfield Company, as the successor to the Anaconda Company, and the owner/operator of the Butte mining business for several years before that business was sold;
  • Three railroads (BNSF, Rarus and Union Pacific) that are current and former owner/operators of property containing mining waste;
  • Federal agencies that were owners or operators of property at the time when it was contaminated with mining, milling and smelting wastes;
  • The city and county of Butte Silver Bow, as a current and former owner/operator of property at the time when it was contaminated with metals from multiple sources.

Each of these parties is also alleged to have arranged for the disposal of metals, and each party has participated in some of the work to implement a portion of EPA’s remedy for Butte Priority Soils.

Many other persons, companies, and entities have been involved in the mining, milling, smelting, and other activities that released contamination in Butte at some point in the past, from its beginning as a mining camp in the 1860's up to today. However, many of these responsible parties are not able to take responsibility for the waste they released. Many people are deceased, and many companies and partnerships have been dissolved. Some of the long-standing disputes at the Butte Priority Soils Site result from the challenge of developing a remedy for contamination created by parties that no longer exist and cannot participate in the cleanup. These are commonly referred to as "orphan parties."

Another challenge arises from large number of potential sources of contamination at this Site. The site boundary encompasses most of the city of Butte and the town of Walkerville. In addition to the former mines, mills and smelters that operated here, there are other sources of metal contamination that include: the past use of mine and mineral processing waste to construct streets, highways, railroads and other infrastructure; the past use of mine waste and other metal-containing fill material to help raise buildings, parking lots and other areas above the floodplain or water table; high levels of naturally occurring minerals that exist in the mining district; and metals released into the city and town stormwater system from contaminated properties, autos and trucks, metal roofs and pipes, and many other sources.

Remedy Enforcement

EPA has several ways to require liable parties to perform or pay for CERCLA remedies. EPA may:

  • Issue an administrative order to compel a trusted responsible party to perform the selected remedy. CERCLA, 42 U.S.C. § 9606.
  • If a responsible party does not comply with a lawful EPA order, EPA may file a lawsuit in federal court, and ask the court to order the responsible party to perform and pay for the selected remedy. In some cases, EPA may also seek a penalty equal to three times the cost of the necessary remedy work which the liable party unlawfully refused to perform. CERCLA, 42 U.S.C. §§ 9606 and 9607.
  • EPA may select and perform the remedy work itself with taxpayer dollars, and then file a lawsuit in federal court to recover the necessary costs of that remedy from responsible parties. CERCLA, 42 U.S.C. § 9607(a).
  • EPA can enter into a voluntary agreement (such as a consent decree) with responsible parties who are willing to perform and fund some or all of the selected remedy. CERCLA, 42 U.S.C. § 9622. Administrative settlements are called Administrative Orders on Consent. Judicially approved settlements are called consent decrees.

Atlantic Richfield Company, Butte-Silver Bow, and the three railroad parties all have conducted remediation work at the Butte Priority Soils operable unit under one or more administrative orders issued by EPA. A list of these orders is included on the Remediation page of this website.

The United States, State of Montana, and Atlantic Richfield Company also have been involved in over thirty years of litigation regarding the parties' alleged liability for contamination at the Butte Priority Soils site (among other sites). Some of these disputes are ongoing, and some have been resolved in consent decrees to implement remedies at other parts of the Butte Area sites and Clark Fork River Basin. Atlantic Richfield Company also has entered settlements with the United States, State of Montana, and Confederated Salish and Kootenai Tribes to resolve all of the natural resource damage claims filed against it.

On February 13, 2020, the United States, State of Montana, Atlantic Richfield Company and Butte-Silver Bow announced an additional proposed consent decree that would, if approved, resolve the parties' alleged liability for most of the remedies that EPA has selected for the Butte Priority Soils operable unit.

The proposed consent decree does not include the residential metals abatement program, commonly known as RMAP. The amended remedy (Feb. 2020) expands the RMAP to new areas of Silver Bow County that are outside the BPSOU boundary and have not been fully assessed. While further assessment work is underway, EPA plans to use its administrative order authority to make RMAP available to thousands of additional residents outside the BPSOU boundary who want to have their homes and yards tested, and who may qualify for further home and yard abatement.

A copy of the proposed BPSOU Consent Decree is available on the Consent Decree page of this website. Further information about the proposed work in the partial BPSOU Consent Decree can also be found in the Remedy section.