The state is wrapping up a toxic mine cleanup in Granite County that left behind the highest mercury concentrations in fish in the state.
Before the cleanup, Fish, Wildlife and Parks conducted a fish study in 2014 on a privately held reservoir at the bottom of the South Fork Lower Willow Creek, about 12 miles northwest of Philipsburg. Trevor Selch, water pollution biologist, said he found 16-inch westslope cutthroat trout that averaged 2.2 parts per million of mercury in their tissue.
That’s 22 times higher than would be expected.
“It’s the hottest little water body in the state,” Selch said.
FWP placed a fish advisory in 2015 at the reservoir warning the public that adults and children over 7 years old can safely eat one 14-to-16 inch cutthroat from that reservoir a month. Women of child-bearing age and kids under 6 should avoid the larger-sized cutthroat in that reservoir altogether. (See information box.)
The Department of Environmental Quality has been working to clean up the Black Pine Mine area, which includes the privately held Lower Willow Creek reservoir and the South Fork of Lower Willow Creek, since 2015. Around 400,000 cubic yards of metals-contaminated waste were excavated across 50 disturbed acres. Mill Creek and Flint Creek were also part of the work.
The overall project began in 2010, DEQ Project Manager Devin Clary said. The initial work involved an investigation into the problem in the area. DEQ found elevated levels of mercury, lead, arsenic, cadmium, antimony and manganese at the historic mine site.
The cleanup was part of the $138.3 million bankruptcy settlement with Asarco for Montana sites in 2009. That settlement included the East Helena Superfund site, which was a smelter site.
The Black Pine Mine cleanup got $17.5 million out of that larger settlement.
The hazardous waste was buried in a repository located on the site. Clary said the repository is upstream of the creeks at the top of the ridge. DEQ drilled several wells to ensure the repository would stay dry and conducted other tests, as well, to ensure the repository’s stability.
The repository was dug into compacted clay and DEQ placed a liner, a drainage net to shed water and above that 36 inches of clean soil.
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DEQ and the U.S. Forest Service, which participated in the cleanup because a portion of the historic mining site was located on public land, held a meeting at the Granite County Museum in Philipsburg Tuesday evening to update the public on the cleanup.
Clary said DEQ is trying to finish up the cleanup work this fall. The agencies have to do some patchwork revegetation and some work on a road that leads to the creek.
If weather doesn’t cooperate this year, DEQ will finish up those tasks next spring.
Selch told The Montana Standard that the advisory will remain in effect on Lower Willow Creek reservoir. If the owner grants permission, FWP will return to the reservoir in a few years to take another sample of the fish. If FWP finds that the mercury levels have dropped in the fish, then officials would consider removing the advisory.
The fish in the South Fork Lower Willow Creek and other creeks within the cleanup site did not show evidence of high mercury. Selch said creeks, “flowing environments,” don’t have the conditions that allow mercury to accumulate in fish tissue as easily.
Mercury breaks down in the water and various water bugs eat it. The fish then eat the bugs. Mercury is a neurotoxin and too much of it in a person’s system can adversely affect the central nervous system.
Mercury is a “global pollutant” and therefore ubiquitous, Selch said. It is rare not to find mercury in all fish, even those way up in high mountain lakes. But in high mountain lakes, the metal is usually found in low concentrations.
But the mercury found in the westslope cutthroat in the reservoir came from a former mill that miners used as part of a silver mine operation in that area.
DEQ will continue to monitor the water quality on a regular basis for the next three years to ensure that the metals are not still showing up in the creeks.
Philipsburg resident Mike Miller, who attended the meeting, called the cleanup “a significant effort in our community to cleanup a significant source of pollution.”