California is one of the five most-contaminated states in the US. The EPA’s National Priorities List currently includes 97 active NPL sites in California, with 116 total entries when proposed and deleted sites are included. The most hazardous site has an HRS score of 74.86 out of a maximum of 100. 2 additional sites are proposed for the NPL and awaiting final listing. 17 sites have been cleaned up and removed from the list. The interactive map below shows all NPL sites in California – click any marker for site details, HRS score, and a link to the EPA’s site profile.
Superfund Statistics for California
| Category | Count |
|---|---|
| Active NPL Sites | 97 |
| Proposed NPL Sites | 2 |
| Deleted (cleaned up) | 17 |
| Total NPL Entries | 116 |
| Highest HRS Score | 74.86 |
| Average HRS Score (active) | 55.8 |
| EPA Region | Region 9 |
Highest-Risk Superfund Sites in California
The table below lists the active NPL sites in California 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 |
|---|---|---|---|
| McCormick & Baxter Creosoting Co. | Stockton, San Joaquin | 74.86 | CAD009106527 |
| Riverbank Army Ammunition Plant | Riverbank, Stanislaus | 63.94 | CA7210020759 |
| Argonaut Mine | Jackson, Amador | 58.31 | CAD983650011 |
| Halaco Engineering Company | Oxnard, Ventura | 58.31 | CAD009688052 |
| McClellan Air Force Base (Ground Water Contamination) | Sacramento, Sacramento | 57.93 | CA4570024337 |
| Operating Industries, Inc., Landfill | Monterey Park, Los Angeles | 57.22 | CAT080012024 |
| Iron Mountain Mine | Redding, Shasta | 56.16 | CAD980498612 |
| Aerojet General Corp. | Rancho Cordova, Sacramento | 54.63 | CAD980358832 |
| Brown & Bryant, Inc. (Arvin Plant) | Arvin, Kern | 53.36 | CAD052384021 |
| Industrial Waste Processing | Fresno, Fresno | 51.13 | CAD980736284 |
| Alark Hard Chrome | Riverside, Riverside | 50.50 | CAD098229214 |
| Blue Ledge Mine | Rogue River – Siskiyou National Forest, Siskiyou | 50.28 | CAN000906063 |
| Klau/Buena Vista Mine | Paso Robles, San Luis Obispo | 50.00 | CA1141190578 |
| Southern Avenue Industrial Area | South Gate, Los Angeles | 50.00 | CAN000905902 |
| Jet Propulsion Laboratory (NASA) | Pasadena, Los Angeles | 50.00 | CA9800013030 |
Superfund Cleanup Progress in California
California has made measurable progress on Superfund cleanup: 17 sites have been fully remediated and removed from the National Priorities List. The remaining 97 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 9
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. California falls under EPA Region 9, which coordinates Superfund investigations, cleanups, and community engagement for the region.
Frequently Asked Questions
How many Superfund sites are in California?
California has 97 active sites on the EPA National Priorities List, plus 2 proposed sites awaiting final listing. Including sites that have been cleaned up and removed, the total NPL count for California is 116.
What is the most contaminated Superfund site in California?
Based on HRS score, the highest-risk active Superfund site in California is McCormick & Baxter Creosoting Co. near Stockton, with an HRS score of 74.86. 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 California: Arizona, Nevada, Oregon. For a national overview, see the US Superfund Sites map.
