EPA National Priorities List: Superfund Site Rankings

The National Priorities List (NPL) is the federal government's official roster of hazardous waste sites across the United States that qualify for long-term remedial action under the Superfund program. Administered by the Environmental Protection Agency under the authority of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, the NPL determines which contaminated sites receive federally funded cleanup resources. Understanding how sites earn NPL status — and what that designation triggers — is essential for property owners, state regulators, responsible parties, and affected communities navigating the Superfund program.

Definition and scope

The NPL is a published list, codified at 40 CFR Part 300, Appendix B, that identifies sites posing significant risk to human health or the environment from releases or threatened releases of hazardous substances, pollutants, or contaminants. Inclusion on the NPL does not constitute a final determination that the federal government will fund remediation, nor does it automatically assign legal liability — but it does authorize EPA to conduct Remedial Investigation/Feasibility Study (RI/FS) work and apply the full suite of CERCLA enforcement tools.

The NPL encompasses two categories of sites:

  1. General Superfund sites — contaminated properties proposed or listed based on scoring through the Hazard Ranking System (HRS).
  2. Federal Facility sites — properties owned or operated by federal agencies, listed in a separate section of 40 CFR Part 300, Appendix C.

As of the EPA's NPL site count data, more than 1,300 sites appear on the final NPL, with additional sites in "proposed" status at any given time. The list covers all 50 states, the District of Columbia, and U.S. territories.

How it works

The primary mechanism for NPL listing is the Hazard Ranking System (HRS), defined in 40 CFR Part 300, Appendix A. The HRS is a numerical scoring model that evaluates four migration pathways:

  1. Groundwater migration
  2. Surface water migration (including overland/flood and watershed)
  3. Soil exposure and subsurface intrusion
  4. Air migration

Each pathway receives a score based on factors including the likelihood of release, waste characteristics (toxicity and quantity), and the number of people or sensitive environments potentially exposed. Pathway scores are combined using a root-mean-square formula to produce a composite HRS score. A site must achieve a score of 28.50 or higher to qualify for NPL listing (EPA HRS documentation).

Two alternative listing mechanisms exist outside the HRS threshold:

Once proposed, a site undergoes a public comment period of no fewer than 60 days before EPA publishes a final listing determination in the Federal Register. Listing is a rulemaking action subject to notice-and-comment requirements under the Administrative Procedure Act.

The EPA authority under CERCLA that governs the entire NPL process grants EPA broad powers to compel responsible parties to perform or pay for remediation once a site is listed.

Common scenarios

Several fact patterns recur across NPL listing decisions:

Industrial facility contamination: Manufacturing plants, metal smelters, and chemical processors that operated under older regulatory frameworks frequently left behind soil and groundwater contamination with heavy metals, volatile organic compounds (VOCs), or polychlorinated biphenyls (PCBs). The Tar Creek Superfund site in Ottawa County, Oklahoma — one of the most contaminated areas in the United States — originated from decades of lead and zinc mining, and illustrates how legacy industrial activity drives HRS scores well above the 28.50 threshold.

Municipal landfill migration: Pre-RCRA municipal landfills that accepted industrial waste alongside household refuse have generated groundwater plumes extending hundreds to thousands of feet from original disposal areas. Such sites score heavily on the groundwater migration pathway because public drinking water wells often fall within documented exposure distances.

Federal facility releases: Military installations and Department of Energy sites contaminated with radioactive materials, solvents, and explosive compounds appear on the federal facility portion of the NPL. These sites involve interagency agreements between EPA and the responsible federal agency, governed by 40 CFR Part 300, Subpart H.

Orphan sites with no solvent responsible party: When the original polluter is bankrupt or untraceable, EPA may use the Hazardous Substance Superfund Trust Fund — financed historically through excise taxes on crude oil and chemical feedstocks, and reauthorized under the Infrastructure Investment and Jobs Act of 2021 — to fund direct federal cleanup.

Decision boundaries

Not every contaminated property qualifies for or warrants NPL listing. EPA applies defined boundaries when making placement decisions:

NPL vs. Removal Action: Sites requiring emergency or time-critical short-term response fall under the Removal Action program, not the NPL. Removal actions address immediate threats and can proceed without NPL listing. The NPL is reserved for sites warranting long-term remedial response that may span years or decades.

NPL vs. RCRA Corrective Action: Active facilities permitted under the Resource Conservation and Recovery Act undergo cleanup through RCRA Corrective Action rather than Superfund. EPA generally does not list RCRA-regulated facilities on the NPL unless RCRA corrective action is determined inadequate — a distinction detailed in the EPA authority under RCRA framework. This represents one of the sharpest jurisdictional boundaries in federal hazardous waste law.

NPL vs. Brownfields: Properties eligible for the Brownfields program — typically lower-risk sites where contamination is less severe — are addressed through grants and voluntary cleanup mechanisms rather than enforceable CERCLA orders. Brownfields sites with HRS scores at or above 28.50 may still be referred for NPL consideration.

Deletion from the NPL: Sites that have achieved all cleanup goals specified in a Record of Decision (ROD) are eligible for deletion under 40 CFR § 300.425(e). Partial deletion — removing only specific portions of a site — is also permitted when remediation in discrete areas is complete while work continues elsewhere.

The full scope of EPA's environmental programs, including the NPL process and its relationship to other regulatory authorities, is indexed on the EPA Authority homepage.