The Environmental Protection Agency plans this summer to drill into the collapsed entrance of a mine near Silverton that’s at risk of a blowout.

If the situation sounds familiar, it is.

The EPA in August 2015 drilled too far into the loose pile of dirt and rocks that covered the entrance of the Gold King Mine, causing a blowout that released 3 million gallons of water laced with heavy metals into the Animas River.

But not all mines are created equal, said Rob Parker, a project manager for the Bonita Peak Mining District Superfund site, which was set up about a year after the Gold King Mine spill.

The Bandora Mine, about 9 miles west of Silverton up Forest Service Road 585, along the banks of the South Fork Mineral Creek, has drawn concern for years because of the risk for a blowout.

What makes the danger of Bandora Mine’s collapsed portal particularly concerning is, should a blowout occur, it could potentially put untold numbers of people at risk in the popular South Mineral Creek camping area.

“It could be a real mess,” Bill Simon, co-founder of the now-defunct Animas River Stakeholders Group, said in May 2016. “There could be serious injury.”

The Bandora Mine produced gold and silver on and off from 1890 to 1940. Although the mine was last known to be owned by Stith Mining LLC, based in Alabama, the site has sat idle for decades.

Over the years, erosion has caused rock and dirt to collapse over the entrance of the mine, which is now backing up groundwater that was previously freely flowing out of the mine’s workings.

The problem is that no one knows how much water is behind the collapsed entranced. In 2015, an inspection showed water inside the mine is spilling out at an elevation higher than the flow of the workings.

“That’s bad,” Kirstin Brown with the Colorado Division of Reclamation, Mining and Safety, said at the time. “There is water backed up. How much? I don’t know. But every mine with water backed up could have the potential to blow out.”

The Bandora Mine has at least 5,000 feet of mine workings – for reference, the Gold King Mine has about 7,000 feet – yet it remains unknown how much water pressure is behind the entrance.

The Animas River Stakeholders Group was awarded a grant a few years ago to work on the Bandora Mine, sitting at an elevation of 10,961 feet, but because of liability issues, the group ultimately scrapped the project.

The Bandora Mine is, however, listed as one of 48 mining-related sites that are part of the EPA’s proposed Superfund listing – the Bonita Peak Mining District – which would have the protections to undertake cleanup efforts.

And that work is expected to start this summer.

As part of the project at the Bandora Mine, the EPA wants to remove the pile of dirt and rock blocking the entrance of the mine to prevent any future unexpected blowouts.

While a similar effort resulted in a major release of mine wastewater at the Gold King Mine, there have been successful examples of entering and clearing the entrance of mines, such as at the Red & Bonita Mine north of Silverton.

The EPA’s Parker said the agency will first drill a well above the portal to the mine to get an idea about the water level inside the workings. If water levels are high, the agency would pump water out before excavating any material.

“We would pump water out in order to draw that level down to open up the portal without the risk of water coming out the front end,” Parker said. “Each location has its own challenges ... but we’ll get an idea of that water level.”

The EPA does not believe there is imminent risk of a blowout at the Bandora Mine, but should that thinking change, the agency would construct holding ponds outside the entrance in case of an unexpected release, Parker said.

“We know this is a portal that’s partially obstructed and water is building up ... but we don’t think there’s an immediate chance of a failure,” he said. “But we want to address it sooner rather than later.”

Peter Butler, another co-founder of ARSG who now helps run the Superfund site’s Community Advisory Group, said the situations with Gold King and Bandora Mine are different.

At the Gold King Mine, the EPA was unable to drill above the entrance of the mine because the ground was unstable. Instead, crews tried to open the mine at the top of the entrance to stick a pipe inside.

“For some reason, they didn’t think the water level was at the top of the adit,” Butler said. “That’s a big unknown why they thought that.”

With the Bandora Mine, it should be more possible to drill above the entrance given conditions on the ground. Butler said water is coming out of the mine about 10 feet above the base of the entrance.

“It could still be tricky to drill behind the Bandora and open it up,” he said. “No one knows how much water is back there.”

The Bandora Mine is considered a high loader of heavy metals into Mineral Creek, a tributary of the Animas River.

Once the entrance is cleared, EPA’s Parker said the agency will evaluate next steps. The agency also plans additional work on the site, such as diverting surface water from coming in contact with mine waste piles.

“At that point, we will evaluate what additional steps need to be done to improve water quality in Mineral Creek,” Parker said.

As far as the safety of campers and the general public, the EPA will also evaluate what steps need to be taken, such as putting up signs or other measures.

Thousands of people camp in the South Mineral Creek area every summer, whether at established campgrounds or dispersed camping, many times in known floodplains.

“It would only be a matter of 15 to 30 minutes before it reached South Mineral Campground,” ARSG’s Simon said previously.

Parker said the EPA hopes to complete the project this summer, but it could go into 2022.

jromeo@durangoherald.com