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Berkeley Pit Water Treatment

Who is responsible for treating the water in the Berkeley Pit?

The Atlantic Richfield Co., a subsidiary of British Petroleum (ARCO or BP-ARCO) which bought out the Anaconda Company in 1977, and Montana Resources (MR), the company now mining in the Continental Pit adjacent to the east of the Berkeley, are responsible, along with four other entities affiliated with MR: Asarco, Inc.; AR Montana Corp.; MR Inc., and Dennis Washington. If they fail to pump and treat the water to keep levels below 5,410 feet, the U.S. government (EPA) can take over the project and charge these companies up to three times the project cost.

Who would be responsible for water treatment if Montana Resources closes permanently?

Under EPA order, both Montana Resources and BP-ARCO are responsible for treating Berkeley Pit water. Under the Superfund law, if one company is unable to pay its share, the other company must pay all the costs of cleanup.

Is the water currently being treated?

Water at the Berkeley Pit is set to begin treatment in the summer of 2019.

Why treat the water?

Water in the Berkeley Pit is required by a court mandate to be treated before it reaches the protective water level (5,410ft).

Where does the water go after being treated?

Water treated in the Berkeley Pit will go to the following locations:

  • Reused in current mining operations at Montana Resources.
  • Discharged into Silver Bow Creek at Montana Street.

How is the water treated?

The Horseshoe Bend Water Treatment Plant is designed to treat up to 7 million gallons of water per day using lime (calcium oxide) to raise the pH (reduce the acidity of the water) and remove metals. As pH rises, metals come out of the water and form sludge. The sludge is separated from the water and returned to the Pit.