Idaho is home to 6 sites on the EPA’s National Priorities List. The EPA’s National Priorities List currently includes 6 active NPL sites in Idaho, with 12 total entries when proposed and deleted sites are included. The most hazardous site has an HRS score of 57.80 out of a maximum of 100. 3 additional sites are proposed for the NPL and awaiting final listing. 3 sites have been cleaned up and removed from the list. The interactive map below shows all NPL sites in Idaho – click any marker for site details, HRS score, and a link to the EPA’s site profile.
Superfund Statistics for Idaho
| Category | Count |
|---|---|
| Active NPL Sites | 6 |
| Proposed NPL Sites | 3 |
| Deleted (cleaned up) | 3 |
| Total NPL Entries | 12 |
| Highest HRS Score | 57.80 |
| Average HRS Score (active) | 54.8 |
| EPA Region | Region 10 |
Highest-Risk Superfund Sites in Idaho
The table below lists the active NPL sites in Idaho sorted by Hazard Ranking System (HRS) score. The HRS is a 0-100 scale used by the EPA to assess the potential threat to human health and the environment. Sites scoring 28.50 or above qualify for NPL listing.
| Site Name | City / County | HRS Score | EPA ID |
|---|---|---|---|
| Mountain Home Air Force Base | Mountain Home, Elmore | 57.80 | ID3572124557 |
| Eastern Michaud Flats Contamination | Pocatello, Bannock, Power | 57.80 | IDD984666610 |
| Monsanto Chemical Co. (Soda Springs Plant) | Soda Springs, Caribou | 54.77 | IDD081830994 |
| Bunker Hill Mining & Metallurgical Complex | Smelterville, Shoshone | 54.76 | IDD048340921 |
| Kerr-McGee Chemical Corp. (Soda Springs Plant) | Soda Springs, Caribou | 51.91 | IDD041310707 |
| Idaho National Engineering Laboratory (USDOE) | Idaho Falls, Bingham, Bonneville, Butte, Clark, Jefferson | 51.91 | ID4890008952 |
Superfund Cleanup Progress in Idaho
Idaho has made measurable progress on Superfund cleanup: 3 sites have been fully remediated and removed from the National Priorities List. The remaining 6 active sites are at various stages of investigation and cleanup. EPA cleanup timelines vary widely depending on contamination type, site complexity, and the availability of responsible parties to fund remediation.
About the Superfund Program in EPA Region 10
The Superfund program, formally known as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), gives the EPA authority to clean up contaminated sites that pose risks to public health or the environment. Sites are assessed using the Hazard Ranking System (HRS) – a score of 28.50 or above triggers NPL listing and formal cleanup proceedings. Idaho falls under EPA Region 10, which coordinates Superfund investigations, cleanups, and community engagement for the region.
Frequently Asked Questions
How many Superfund sites are in Idaho?
Idaho has 6 active sites on the EPA National Priorities List, plus 3 proposed sites awaiting final listing. Including sites that have been cleaned up and removed, the total NPL count for Idaho is 12.
What is the most contaminated Superfund site in Idaho?
Based on HRS score, the highest-risk active Superfund site in Idaho is Mountain Home Air Force Base near Mountain Home, with an HRS score of 57.80. The HRS score reflects the site’s potential to harm human health or the environment through groundwater, surface water, soil, or air pathways.
How does the EPA decide which sites go on the Superfund list?
The EPA uses the Hazard Ranking System to score sites based on the likelihood of a release, the characteristics of the waste, and the people or environments that could be affected. Sites scoring 28.50 or higher are eligible for the National Priorities List. Once listed, sites become eligible for federally funded cleanup or enforcement against responsible parties under CERCLA.
Superfund Sites in Nearby States
Explore Superfund data for states bordering Idaho: Montana, Nevada, Oregon, Utah, Washington, Wyoming. For a national overview, see the US Superfund Sites map.
