RIMINI — The former Pocahontas mine site is located in the Minnehaha Creek basin in the mountains southwest of Helena. About 100 years ago, the mine produced lead and zinc, which were transported by wagon for processing further down the mountain. While the miners extracted the high-quality ore, they left the low-quality material in a pile on the hillside.
Now, after all this time, the contaminated soil is being cleaned up as part of the latest phase of remediation at the Upper Tenmile Creek Mining Area Superfund site.
“When agencies, the public and contractors work together, we can really accomplish a lot,” said Dick Sloan, senior environmental project manager with the Montana Department of Environmental Quality.
Jonathon Ambarian
The Upper Tenmile Creek area is a historic mining area surrounding the community of Rimini. It was placed on the federal Superfund list in 1999 due to ongoing contamination.
Authorities identified about 150 active and abandoned mine sites in the area – many of them small gold, copper, lead and zinc producers. The leftover material from mines like the Pocahontas still contains significant amounts of metal – perhaps 5 to 8 percent zinc and 4 to 5 percent lead, according to Sloan. When rainwater or meltwater seeps through, it can create acidic runoff and leach metals into nearby streams.
The U.S. Environmental Protection Agency has secured funding for the current phase of work, which focuses on the Minnehaha River Basin, and DEQ is overseeing the project.
There are about 40 former mine sites in the basin, and officials have identified five of them – including Pocahontas – that contributed most to metal loading in Minnehaha Creek and further downstream in Upper Tenmile Creek, and are concentrating their work there.
Jonathon Ambarian
Contractors are currently using excavators to dig up the contaminated material, loading it onto trucks and transporting it about 12 miles (19 kilometers) to a secure, sealed repository near the tip of the Continental Divide.
“It will certainly have a significant impact on reducing the amount of zinc in both Minnehaha Creek and the Upper Tenmile,” Sloan said.
Sloan said the amount of zinc in the water is currently within federal drinking water standards, but there are concerns about the impact on aquatic life – particularly fish and large invertebrates.
Jonathon Ambarian
Buster Bullock owns Bullock Contracting, which is doing the current construction work.
“It’s an awfully big mountain and there is an enormous logistical effort involved in terms of the various transport routes and the many kilometers needed to get the product to the final storage facility,” he said.
In addition to material from the mine sites, workers also transport waste from previous cleanup operations to the repository. Trucks transport this material along the lower end of Rimini Road before turning onto Minnehaha Creek Road. Minnehaha Creek Road is closed weekdays through the end of summer to allow all truck traffic.
“It’s really uncomfortable for us to tell someone they can’t go out there,” Bullock said. “But what can happen if they do – you see the size of the trucks, they don’t stop right there.”
Jonathon Ambarian
At the Pocahontas mine, approximately 4,000 tons of contaminated material must be removed. Workers will then deliver clean soil and eventually recontour and replant the ground.
“There will be no more garbage pile,” Sloan said.
Jonathon Ambarian
While this work will clean up the environmental damage left by the legacy of early miners, Sloan said it’s important to remember that those miners provided the materials needed – and did so within the rules of the times.
“Now we’ve learned that maybe we could have done some things differently, but everyone did what they could based on what they knew best,” he said.
Sloan said officials hope to have all work on the Minnehaha Drain completed by the end of the year. After that, they will look at other potential projects in the area, but most of the major demolition work will be completed, so there will be less heavy traffic on Rimini Road in the future.
