37 years ago, Atlantic Richfield abandoned an open pit copper mine in Butte and allowed it to flood with toxic mine water. Now, the company estimates they’re one month away from proving they’re in control of the Berkeley Pit. MTPR's Nora Saks got a sneak peek of their new water treatment facility and has more.
I’m inside a huge tan shed located right next to the Berkeley Pit in Butte, resisting the urge to reach out and touch the maze of tanks, spigots, gauges and pipes going every which way.
"We are treating water right now, so it’s very important that we don’t - everyone wants to turn a valve or push a button, but let’s try not to do that today."
That’s Atlantic Richfield’s operations manager Ron Halsey. He’s in charge of this new polishing plant, which has an unassuming appearance, but is almost ready to serve a critical function.
It’s the final component of a pilot project to start pumping and treating the highly acidic and metal-laden groundwater flooding the Berkeley Pit, well before it reaches the point when it will contaminate Butte’s aquifer and creeks. Unmanaged, that’s projected to happen in 2023.
"The pilot project is really about holding, trying to hold the Pit steady, we want to make sure we can control the Pit, and that’s what this pilot project is set to do," Halsey says.
Under a legally binding Superfund decision, both Atlantic Richfield and Montana Resources are in charge of the Berkeley Pit and required to keep the water below the so-called "critical level."
To do that, their pilot project will take toxic water from the 50 billion gallon pit lake on a long, strange trip. First, it gets pumped out and sent on a spaghetti-like route through MR’s active mining operation next door. Along the way, it’s used on site, treated with lime, and herded up to the tailings impoundment. By the time water from the backside of the tailings dam is piped down to AR’s new polishing plant, the pH is basic, and 99% of the heavy metals have dropped out.
Halsey walks over to a grey pipe labeled “raw water influent."
"It comes in our facility right here."
At this last stop, the water is further cleaned to meet state and federal water quality standards, so it can be discharged into Silver Bow Creek, its final destination.
Using gravity, incoming water is cycled through a series of “multi-media filters” - a more complex version of what might be in your swimming pool.
"These filters have basically three layers. On the top is an anthracite, which is a coal, then it has sand, and then at the bottom it has gravel."
Then, non-toxic chemicals are added to make sure any remaining metals settle out and bind onto the filters, and carbon dioxide is injected to lower the pH back to the required neutral 7.
Halsey says the $19 million facility is state-of-the-art because of the filtration system, and the fact that it’s run by sophisticated computers. He points to a grey box with lots of little panels.
"That’s the brains of the whole outfit. That’s where everything is controlled. So we’ll stop here real quick."
This new polishing plant is also designed to adapt to changes in the Pit’s water chemistry over time, and handle very large volumes of water, between three and ten million gallons per day.
"So we’ve tested these technologies at a pilot scale. At 10, 15 gallons a minute for 2 or 3 days. Now we’re going to test them at up to 7,000 gallons a minute, 24-7. So it’s really important that we prove we can do this safely," Halsey says.
Right now, every gallon of treated water is being recycled back into Montana Resources’ mining circuit. It’s gushing through a giant faucet under a grate in the floor.
But if, or when the filtered water passes EPA’s tests, it will be released for the first time ever into Silver Bow Creek, and begin a whole new journey in the Clark Fork River watershed. Atlantic Richfield’s Ron Halsey expects to have approval from the agency by mid-September.
"We’re not focused so much on the actual date, as making sure that everything is operating properly and we’ll have a safe discharge to the creek. So the date really is pretty flexible. We’re four years ahead of when we think we would have to remove water from the Pit, so we feel like we have plenty of time."
Atlantic Richfield is currently in discussions with EPA and Montana Resources about building an additional water treatment plant to draw the level of toxic water in the Berkeley Pit down further.
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