Some of the abandoned mines scattered around the state are nothing more than a pile of rocks on a mountainside—something most hikers wouldn't even notice, according to Jonathan Oppenheimer, senior conservation associate with the Idaho Conservation League.
"Then there are cases where people are out snowmobiling or ATV riding and boom, they fall into an abandoned mine shaft and die," Oppenheimer said. "It's a serious thing."
They run the gamut of harmless little holes in the ground to old adits full of contaminated groundwater. There are an estimated 5,000 of them—from the Boise National Forest, through the Salmon-Challis area, along the border of Montana and in northern Idaho, as well as the Owyhee Canyonlands.
"The mines are from the mid-1800s through the 1950s," Oppenheimer said. "There is more work to do out there in buttoning these up than there is capacity to do it. It's a big, gaping hole—no pun intended—in the federal budget, but the Bureau of Land Management and the U.S. Forest Service do take it seriously."
So seriously that the BLM's Idaho office hired Cheryl Seath in 2013 as the full-time Abandoned Mine Lands Hazardous Materials coordinator. She competes for funding against 13 other Western states teeming with abandoned mines and manages a small team. Together, they close off around 140 mines per year.
"It's hard to say if we only have 5,000 abandoned mines," Seath said. "It gets added to every year. Sometimes fires will burn up vegetation that was covering up a shaft. We prioritize sites by their physical safety issues and how close they are to urban or recreational areas."
Seath added to the list of Oppenheimer's concerns. Someone could walk too far into an adit and run out of oxygen, then die of carbon dioxide poisoning. Sometimes dynamite is left behind that can be dangerous to whoever discovers it.
Closing each abandoned mine takes anywhere from $20,000 to $30,000, according to a BLM report.
Seath's crew either fills in the shaft with nearby rock and soil or installs a bat gate, which is large enough to let bats through but keeps humans out. They also use an expandable foam to close some shafts, "like the foam you put into your tire if you have a flat," she said.
Even after the mine is closed, it still remains on Seath's radar. Each of the mines have to be maintained and protected from vandalism, whether people are burning out the foam to get into the mine or cutting the bars on the bat gates.
"Then there's the active sites that will have to be closed as well," she said.
Mining companies usually put in their own closures, but if they declare bankruptcy and walk away from the site, it falls on taxpayers to clean up after them.
According to a report published Dec. 2, 2015 by the Center for Western Priorities, "The Mining Burden: Why State Land Seizures Could Cost Billions," if Idaho took over public lands it could be on the hook for up to $1 billion to clean up and close the remaining mines in the state.
"This billion dollars hasn't even been factored into the analyses that have been done," Oppenheimer said. "Just in the management of public lands—mostly managing wildfires—would cost the state about $1.5 billion over the course of 10 years. This is just one more argument in the cost column when we're looking at the costs and benefits at taking over public lands."
John Robison, Public Lands director at the Idaho Conservation League, has heard his share of horror stories about Idahoans running into abandoned mines—whether they nearly pitched a tent on top of a vertical mine shaft in the wintertime, or took home highly toxic sand for their children's sandbox.
Robison said the shadow cast by abandoned mine points to the need to reform the 1872 Mining Law. Mining companies are supposed to place a bond with the BLM or Forest Service that would cover the cost of cleanup, should the company go out of business.
The problem, Robison said, is the bonds aren't sufficient to clean up the site.
"Take the Thompson Creek Mine, outside of Challis," he said. "They have a reclamation bond in place for $42 million. The problem is, they unintentionally created an acid mine drainage problem, so rainwater and snowmelt percolates into the tailings, mixes with the sulfides and sulfuric acid comes out the bottom into the headwaters of the Salmon River."
Right now, the company is capturing the water and treating it, but Robison said that sort of treatment will have to go on forever, and $42 million won't cover it.
"Thompson Creek is teetering on the edge of bankruptcy," he said. "You and I and all the other taxpayers will be left with the bill to clean that up. Meanwhile, what happens to the sulfuric acid going into the Salmon River?"
After the Gold King Mine wastewater spill into Colorado's Animas River in August 2015, Robison started focusing on abandoned mines possibly threatening the Boise River.
Robison asked officials from the U.S. Environmental Protection Agency, the Idaho Department of Environmental Quality, BLM and the Boise National Forest exactly how many abandoned mines are upstream of Boise.
"The answer," Robison said, "was, 'We don't know.'"