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EPA to tackle one of most vexing polluters in Animas River basin

American Tunnel poses complex situation for Superfund cleanup
The American Tunnel, pictured here, poses one of the most complicated challenges in the Environmental Protection Agency’s Superfund cleanup of mine sites around Silverton, degrading water quality in the Animas River.

The Environmental Protection Agency announced Friday it intends to undergo a major effort this summer to understand one of the most vexing polluters in the upper Animas River watershed.

In July, the EPA will directionally drill into the American Tunnel on an existing well pad on private land near County Road 51 in San Juan County in what the agency calls a “critical site investigation” to understand groundwater conditions in the area.

The American Tunnel, which travels about 11,000 feet, served as a transportation route for ore, as well as a drainage channel for mine runoff, from the vast Sunnyside Mine workings to facilities at Gladstone, north of Silverton.

When Sunnyside Mine closed for good in 1991, attention turned to what to do with acidic discharges out of the American Tunnel. Sunnyside Gold initially pulled the water into a treatment plant but ultimately decided with the state of Colorado to install three bulkheads (essentially plugs) to stem the flow of acid drainage.

But in recent years, researchers believe the Sunnyside mine pool behind the American Tunnel has reached capacity and the water is spilling into other mine networks, such as the Gold King Mine, which sustained a massive blowout while the EPA was working on the mine in August 2015.

As a result, the drainage into Cement Creek, a tributary of the Animas River, is considered one of the worst contaminators in the basin and is part of the EPA’s larger Bonita Peak Mining District Superfund site that aims to improve water quality.

Sunnyside Gold, for its part, has adamantly denied over the years that its mine pool is the cause for other mines starting to discharge acidic drainages. The company, owned by international mining conglomerate Kinross Gold Corp., is considered a “potentially responsible party,” a term EPA uses for entities that could be on the hook for cleanup costs.

In an email Friday to The Durango Herald, EPA spokesman Richard Mylott said information gathered will be used to better understand the water levels within the tunnel and the connection with the larger Sunnyside mine pool, as well as other mine workings.

“This will help inform future decisions about how to manage the mine pool to control and/or treat discharges from affected mines,” Mylott wrote. “EPA will conduct this action in accordance with rigorous safety and contingency measures developed in a plan for the completion of the well. By drilling directionally from a well pad constructed in 2017, EPA will limit ground and local traffic disturbances as well as potential impacts to cultural resources.”

As part of the order Sunnyside must also:

Install up to three groundwater wells in the Lake Emma Basin to understand water levels, flow paths and groundwater chemistry within the Sunnyside mine workings.Install one well into the Terry Tunnel and one well into the Gold Prince Tunnel wells to assess and monitor bulkheads and water levels within those workings.Establish two meteorological stations near Eureka Gulch and Ross Basin. The EPA’s order requires Sunnyside Gold to evaluate groundwater conditions in the American Tunnel, but the agency is delaying the order to drill at the site until after EPA has installed its own well and evaluated the data it provides.

“These activities address the EPA’s goal of minimizing human health and ecological risks in the mining district by improving water quality in the Animas River and minimizing unplanned releases from draining mines within the site,” Mylott said. “Using the information gathered this year, additional investigations will be undertaken in the future to fully characterize the Bonita Peak Groundwater System.”

EPA will provide project time lines in coming weeks, Mylott said.


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