Bonita Peak Mining District superfund site update

The “Bonita Peak Mining District” superfund site. Map via the Environmental Protection Agency

From The Durango Herald (Jonathan Romeo):

Driven by desire to know what lies beneath, crews bore deeper every day

EPA crews last week started to bore into the ground in what is expected to be a more than 500-foot journey to reach the American Tunnel in hopes of better understanding a complex network of mines in the upper Cement Creek basin, a tributary of the Animas.

It’s these mines that are considered the worst polluters of heavy metals seeping into the Animas River…

In 1959, however, when Standard Metals announced it was going to reopen the Sunnyside Mine, the now-defunct company also said it was going to extend the American Tunnel from the vast mine network to Gladstone, an old mining community about 10 miles north of Silverton.

Extending the tunnel solved two costly problems for previous mining companies: It allowed for ore to be easily taken out for further processing, and it created a better system for groundwater to exit the mine.

The move led to a three-decade period of prosperity, said Bev Rich, Silverton native and director of the San Juan County Historical Society.

“They discovered some really good gold, and a good reserve of it,” she said.

In 1991, however, the Sunnyside Mine, which had been taken over by Sunnyside Gold Corp., closed as a result of depressed gold prices. What was left behind, in terms of the American Tunnel, was a never-ending pathway for acidic discharges.

Sunnyside Gold initially pulled water coming out of the American Tunnel into a treatment plant, a costly yet effective method that took metals out of Cement Creek and greatly improved the quality of the Animas River.

But, in a move hoping to end its financial involvement in the Animas River basin, Sunnyside Gold entered an agreement in 1996 with the state of Colorado to shut down the treatment plant and instead install three bulkheads that essentially function as plugs to stem the acidic flow.

By 2001, though, it was thought the water had backed up and reached capacity within the Sunnyside Mine network, which has led some researchers and experts familiar with the basin to believe that water is spilling out into adjacent mines, like the Gold King.

Sunnyside Gold, which was purchased by international mining conglomerate Kinross Gold Corp. in 2003, has adamantly denied that its mine pool is the cause of discharge from other mines, saying there is no factual evidence for the assertion…

One thing is clear: After the Bonita Peak Mining District Superfund site was officially listed in fall 2016, EPA made it a priority to figure out what was happening with water movement underground. This past winter, a helicopter carrying an electromagnetic mapping device made the rounds around Silverton to try to understand the geological makeup of the San Juan Mountains, and hopefully, its groundwater workings.

This desire to know what lies beneath is what ultimately led to EPA drilling into the American Tunnel…

Guy, with the EPA, said it could take almost a month to reach the American Tunnel, boring through 20 to 30 feet of hard rock per day. The intent is to reach a portion of the tunnel between bulkheads 2 and 3, but it’s going to take more wells and more research to form a better grasp on how water moves underground in this geological puzzle…

Butler said the project plays into the larger question surrounding the Bonita Peak Superfund site: What is the ultimate strategy to fix issues in the upper Cement Creek area? EPA, for its part, has said that question warrants further investigation and time before being answered.

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