BUTTE — Believe it or not, much of the water in Silver Bow Creek west of Butte used to be in the Berkeley Pit. Montana Resources has been pumping treated pit water into the creek from more than two years now.
Since October of 2019, about 6 billion gallons of treated water from the pit and mine yard has been pumped into Silver Bow Creek. This was a part of an effort to control the rising water in the Berkeley Pit to prevent it from seeping into the city’s groundwater.
“So, the water level has not risen a tenth of a foot in over two and half years, where it used to rise six feet a year,” said VP of Environmental Affairs for Montana Resources Mark Thompson.
Water gets pumped from the pit and first gets treated at a plant at the mine. Water going to the creek gets a round of treatment at the polishing plant run by Atlantic Richfield before it goes to the creek.
A compliance sample of the treated water is taken every day to make sure it meets state standards before going into the creek.
“That’s almost 9,000 compliance checks for the quality of water discharged into Silver Bow Creek, and in that time we have not exceeded a single standard, not even once,” said Thompson.
The water level in the pit in 1982 was over 4,200 feet and it has steadily risen over the year to just over 5,300 feet since pumping began, keeping it below the protective level of 5,410 feet.
“We’ve proven this is a very manageable system, so I can’t think of anything that could have gone better than it has,” he said.
And they will have to keep controlling the water level as long as the pit remains.