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Berkeley Pit pilot project still on schedule, say mine officials

Berkeley Pit pilot project still on schedule, say mine officials


Montana Resources remains on target to begin pumping and treating Berkeley Pit water five years ahead of schedule, mine officials say, and the company has begun laying the groundwork at the mine site for the impending pilot project to begin.

Montana Resources has been busy fusing and laying down pipe around the mine. The pipe will carry the initial 3 million gallons, later to become 7 million gallons of water each day through a complex system of treatment and usage before any water makes its way down to Silver Bow Creek. 

MR is waiting on six custom-built pumps that are due to arrive this fall. Two pumps will go into the pump house near the pit’s edge. The other four will be close to the Horseshoe Bend Water Treatment Plant.

Mark Thompson, MR's vice president of environmental affairs, declined to say how much the construction and new equipment will cost, but he said it’s in the millions. Thompson said two years ago that the companies spent $1 million upgrading Horseshoe Bend Water Treatment Plant, which plays a crucial role in the process. 

A polishing plant has yet to be built. That will be the final step the water will go through before it hits the creek.

Atlantic Richfield spokesperson Michael Abendhoff said via email that the company expects to begin construction this year, with operations to start next year. He didn’t respond to questions about where on the Montana Resources' site the polishing plant is expected to go.

MR has also set up what they refer to as a mini-version of Horseshoe Bend Water Treatment Plant, so they can test the water and apply different scenarios.

MR is using the mini plant to look at different filtration systems, as well as a reverse osmosis system, to see what is the best way to polish the water before it gets sent out to Silver Bow Creek.

There will be an added benefit to pumping and treatment. 

Once the Berkeley Pit water begins pumping and treatment, that should prevent significant sloughing, Thompson said.

The rising water is what destabilizes the walls, said Thompson.

“It wouldn’t get worse,” Thompson said of the sloughing.

Thompson said there is “always small-scale bench failure” at the Berkeley Pit.

“That’s just open pit mining,” he said. “But there’s been nothing of any size or concern lately.”

The last major sloughing event took place in February 2013. Roughly 850,000 tons of sediment fell into the pit. As a result, the water rose .6 feet, according to

Once the treatment begins, the pit water will twist around the mine in a complex system. A pump house will pump the water out of the pit and send it to the precipitation plant, which will recover the copper out of the water. The water will then travel to Horseshoe Bend Water Treatment Plant, where it will go through treatment, before it is routed through the mine workings.

From the mill, the water will then head to Yankee Doodle Tailings Pond, where it will land on what mine officials call "the beach." The beach is the muck that comes from the mixture of water that also contains ground up ore that has the important stuff — copper and molybdenum (or moly) — removed. The water settles out to the north side of the pond.

Another pipe will route water at the back of the pond, which is relatively clean water, back down the hill to the polishing plant. 

Once it’s up and running, the new system will start out pumping 3 million gallons of Berkeley Pit water per day. Sometime next year, the companies will scale up to pumping and treating 7 million gallons of pit water a day, Thompson said.

The Berkeley Pit is a former large open pit copper mine that was in operation from 1955 to 1982, when Atlantic Richfield ceased operations and shut off the industrial-sized groundwater pumps. The pit generates acid and the water in it is loaded with a cornucopia of heavy metals.

The treated discharge water is expected to add 10 cubic feet per second of flow to the creek. Montana Fish, Wildlife and Parks Fish Biologist Jason Lindstrom said recently that the added water to the stream can impact the creek in a variety of ways.

“I’m mostly worried about temperature,” Lindstrom said.

Thompson said that because the discharge water will be coming from the Yankee Doodle Tailings pond, the water “should be cooler in summer and warmer in winter.”

“It’s a deep reservoir, 100 feet deep. It’s kind of like the water coming out of other reservoirs, which are typically cooler than a small stream,” he said.


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Environmental and natural resources reporter for the Montana Standard.

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