BUTTE — Montana officials plan to clean up mine and mineral processing waste dumped near the Butte Civic Center and county shops by moving some of the waste rock into a Superfund site filled with billions of gallons of acidic water.
The state reached an agreement with Montana Resources to dump about 270,000 cubic yards of the waste into Berkeley Pit, a former open-pit copper mine, Jim Ford, project manager for the Natural Resource Damage Program, told The Montana Standard this week.
The waste rock would not significantly change the chemistry or volume of the pit’s contents, according to the plan.
The U.S. Environmental Protection Agency believes the mine waste can be left in place with ongoing water treatment, but some residents are concerned that heavy metals, including lead and arsenic, will make their way into the groundwater and nearby Silver Bow Creek. It took 16 years and cost $147 million to clean mine waste from the lower part of the creek.
The state’s plan would leave some of the waste where it is, capping it in areas where groundwater contamination is not a concern. The work would include relocating the county shops because they sit atop some of the waste.
The Butte Natural Resource Damage Restoration Council heard the broad outline of the plan Tuesday. The full proposal was expected to be released to the public Thursday.