Energy giants Chevron Corp., BP PLC, ExxonMobil Corp., and others agreed to a $7.76 million settlement with the state of Colorado on Monday, over alleged pollution at a mining and metallurgical research center in Golden Colorado, Law360 reports.

Colorado previously filed a complaint in federal court alleging that 11 defendants, including the federal government, were responsible for the release of harmful substances at the research site between 1912 and 1987. The state stipulated that all 11 entities would contribute to the settlement, which would reimburse the state for some of the cost of cleaning up the harmful substances from research projects.

“As a direct and proximate result of such releases or threatened releases of hazardous substances at the site, Colorado has incurred approximately $13 million in necessary, unreimbursed response costs to investigate and clean up hazardous substances,” the complaint stated.

The research site in Golden, Colorado was used by the defendants from 1912 to 1948 as a research facility to “develop ore preparation techniques,” according to the complaint. In 1948, the site became the home of the Colorado School of Mines Research Institute, where mining research was conducted “on behalf of private industry and government contractors.”

The Golden, CO site facilitated thousands of research projects, many of which were confidential and contained “military trade secrets.” The complaint alleged that research materials at the site contained toxic, hazardous substances including, “radionuclides, lead, arsenic, molybdenum, vanadium and mercury.” The toxic substances continue to contaminate the soil and groundwater at the former research site.

The government will pay the largest share of the settlement, $3.699 million. Other defendants include BP America Inc., Cotter Corp., Elf Aquitaine Inc., Freeport-McMoRan, Industrial Minera Mexico SA de CV, Mexicana de Cobre SA de CV, and Terra Industries.

Alisha Mims is a writer and researcher with Ring of Fire.