Editor's note: This story was updated at 1:45 p.m. Monday to better clarify the cost of the project. The following sentence was added: The cost of the pumping is about $120,000, said Harley Harris, NRD attorney. The $3.45 million cost represents the cost for the construction of phase one of the Parrot tailings removal project.
As much as 30 million gallons of highly contaminated groundwater will be pumped out of the former Parrot Smelter site in middle of Butte beginning this summer, state officials say.
But the excavation project removing the source of the groundwater's contamination has been put on hold while Butte-Silver Bow teases out the final details of the relocation of the county shops, which sit atop the site where the second half of the smelter byproducts that cause the groundwater contamination are buried. (See related story.)
The state and the Environmental Protection Agency battled for years about whether to remove that contamination, which is the result of the smelting process that occurred at the site behind the Butte-Silver Bow Civic Center over a 20-year period in the late 19th century.
While Montana and the EPA still disagree about the remedy for the toxic water at the site, the state opted to move ahead anyway in late 2015 and remove the contamination's source: mine and smelting waste and contaminated black clay.
The state's Natural Resource Damage Program began overseeing the excavation of the Parrot tailings in 2018, to much fanfare, with Gov. Steve Bullock and other officials showing up for the groundbreaking ceremony.
The first half of that work was completed last year.
While the state waits to begin excavating the second half of the Parrot tailings, Jim Ford, NRDP project manager for the Parrot removal, said last week that the NRDP will use the interruption in tailings-removal work as an opportunity to start pumping out the plume of bluish water in the ground at the construction site.
That water has been found to have 15 times more copper, five times more lead, and twice as much cadmium as water in the Berkeley Pit.
The Parrot groundwater plume also contains the same amount of arsenic and zinc as the Berkeley Pit and has been described by hydrologists as the most contaminated mine water in the state.
Ford said that when the NRD started the project, workers found the contaminated water to be much more extensive than anticipated.
Once it leaves the ground, the toxic water will travel through a double-walled pipe through a culvert under Shields Avenue and end up in a Montana Resources pond located below the active mine's concentrator.
Mark Thompson, MR vice president for environmental affairs, said the mine normally circulates 3 to 4 million gallons of water a day through that pond and that the extra flow from the Parrot would be “almost nonexistent.”
He said the water will be treated at the pond.
The metals that fall out in the pond will be dredged along with other tailings and go to Yankee Doodle Tailings Impoundment, where all of MR's mine waste currently goes.
Thompson said the volume of copper in the water from the Parrot site is not large enough to be worth routing to the precipitation plant where MR is currently recovering copper from the Berkeley Pit. That plant sits on the other side of the mine site.
“We’re just happy to be of service,” Thompson said.
The cost of the pumping is about $120,000, said Harley Harris, NRD attorney.
With the overall price tag of $3.45 million for construction of phase one on the Parrot removal project, the construction of phase one has stayed under its overall budget, Ford said. But the overall estimated cost of the project has increased since NRDP originally presented its expected expenditures in 2017. (See related story.)
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Harris said the final cost for phase one of the groundwater-pumping project will ultimately be higher than $3.45 million, as there are additional costs that haven't been fully factored in yet.
He will present those numbers after the end of the current fiscal year on June 30.
But Ford said the pumping project will cost the state less than a penny a gallon.
“I can’t underestimate the cost effectiveness for this,” Ford said.
Ford said the state wants to do it because it will help clean up the aquifer beneath the center of Butte. The state's ultimate goal is to protect its $157-million cleanup on lower Silver Bow Creek by removing the source of the pollution to the aquifer.
The pumping will likely start in July and will continue for about seven months, Ford said. He said the aim is to keep pumping until the weather gets cold enough to potentially freeze pipes — but that plan might change.
“If it’s wildly successful, we’ll look at the cost of burying the pipes and running it through the colder months,” Ford said.
The pumping process will turn the hole that is fenced off behind the Civic Center into what's known as a "cone of depression." The term refers to places like the Berkeley Pit, where groundwater collects beneath the surface of the ground.
Ford said the NRDP installed monitoring wells all around the site and through the corridor toward the creeks that run along the southern part of town, near the site.
Those wells will enable the state to track how the cone of depression is affecting the area’s groundwater. He said a two-year window is about how long the state can keep up the pumping without altering the groundwater flows that travel to the Berkeley Pit.
The flow rate could be variable. Current estimates predict 10 million to 15 million gallons will flow off site to MR each summer season, and the project is expected to last for two warm seasons — this summer and next summer. The agreement with MR is for 100 gallons to be pumped to the mine's pond per minute.
Ford presented the plan to the Butte Natural Resource Damage Council Thursday evening at the Butte-Silver Bow Public Archives.
Emmett Riordan, BNRC member, asked Ford, "Why not run it (the pump) longer?"
In response, Ford called the current plan a "first step."
"The benefit is high, and the cost is low," Ford said. "I could see expanding or maintaining something like this."
So far the NRD has removed 400,000 cubic yards of material behind the Civic Center. Of that, 113,000 cubic yards was overburden. About 100,000 cubic yards was made up of slag, which is smelting waste. And about 170,000 cubic yards was tailings, which is mine waste plus highly contaminated black clay.
Ford said the pumping could affect the subdrain — the slotted pipe that runs horizontally 5 feet below ground and passes beneath upper Silver Bow Creek from the Civic Center to George Street near the creek's confluence with Blacktail Creek.
"I think it would have a positive effect (on the subdrain) by keeping contaminated water out of there," Ford said.
The subdrain currently collects contaminated groundwater from throughout the upper Silver Bow Creek corridor as part of the EPA remedy for the Butte Hill.