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U.S. EPA orders manufacturing company to investigate contamination at San Benito Superfund Site

Results will support options for cleanup at one of the country’s largest mercury mines

Contact Information: 
Nahal Mogharabi (

SAN FRANCISCO – Today, the U.S. Environmental Protection Agency (EPA) announced a settlement with Buckhorn Inc. to study contamination at the New Idria Mercury Mine Superfund Site in San Benito County. The work is expected to take over two years to complete at a cost of approximately $2 million.

“The legacy of abandoned mines threatens public health and natural resources in California,” said EPA Pacific Southwest Regional Administrator Mike Stoker. “After the feasibility study is complete, EPA will select a final remedy and work toward the ultimate cleanup, protecting important waterways from mercury and other pollutants.”

Under the Trump Administration the Superfund program has reemerged as a priority to fulfill the Agency’s core mission of protecting human health and the environment.

Buckhorn Inc., a reusable plastic packaging manufacturer, is the successor to the New Idria Mining and Chemical Company, a former owner and operator of the New Idria Mercury Mine. The mine, located 64 miles southeast of Hollister, Calif., operated from about 1854 to 1972 and produced over 38 million pounds of mercury. At one point, it was the largest operating mercury mine in the country. The New Idria Mercury Mine was added to the National Priorities List in September 2011.

Under the agreement, Buckhorn will investigate the extent of contamination at the abandoned mine to identify potential human health and environmental risks. The results will inform a feasibility study with options for cleaning up the site under EPA oversight. As a responsible party under the Superfund law, Buckhorn will be responsible for investigation and cleanup costs.

Operations at the New Idria Mercury Mine deposited between 0.5 and 2 million tons of waste rock, calcines, and tailings covering more than 40 acres at the site. While EPA and Buckhorn have taken recent steps to minimize release of contaminants from the site, years of mercury pollution and mine drainage have contaminated San Carlos Creek and its sediments with levels of mercury toxic to aquatic organisms. During periods of heavy precipitation, floodwaters wash these contaminated sediments downstream where they may reach the Mendota Pool and San Joaquin River, which flows into San Francisco Bay.

Mercury, especially in the form of methylmercury, is highly toxic and bioaccumulates in living organisms. Methylmercury is an organic mercury compound created by microbes in aquatic systems such as creeks and wetlands and is known to build up in the sediments, posing a threat to fish and other wildlife. People who eat contaminated fish or other contaminated wildlife are at risk of mercury poisoning, which can damage people’s nervous systems and harm the brain, heart, kidneys, lungs and immune system.

For more information on the New Idria Mercury Mine Superfund Site, please visit:

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