This summer will be the first full work season since the Bonita Peak Mining District Superfund site was declared last September, and the Environmental Protection Agency is wasting no time trying to figure out one of the biggest mysteries in the watershed: The American Tunnel.
EPA hydrologist Ian Bowen said this week the agency plans to drill 500 feet into the San Juan Mountains to install a monitoring well between the second and third bulkheads on the tunnel.
“It’s not easy, but it’s certainly not impossible,” Bowen said at a community meeting Tuesday in Silverton
The American Tunnel, which travels about 11,000 feet, served as a transportation route for ore, as well as a deep drainage, 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 initially pulled the water into a treatment plant, but ultimately decided with the state of Colorado to install three bulkheads 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 and Red & Bonita.
In the case of Gold King, a historically “dry mine,” discharges became such a serious concern that the EPA in 2014 stepped in to investigate. The agency placed a bulkhead on Red & Bonita that has not been closed and is evaluating the impacts should the valve be closed.
A year later, however, an EPA-contracted crew dug too deeply into the collapsed portal of loose rock and gravel around the Gold King entrance, releasing 3 million gallons of mine waste down the Animas and San Juan rivers.
The spill, which drew national attention, kicked off events that ultimately led last fall to Superfund listing, comprised of 48 mining-related sites believed to be major contributors to degrading water quality in the Animas River.
The Animas River headwaters are broken into three drainages: Mineral Creek, Cement Creek and the Upper Animas.
Rebecca Thomas, project manager for the Bonita Peak Mining District Superfund site, has previously said each drainage accounts for about a third of heavy metal loading in the Animas, causing a dead zone of aquatic life on the river from just below Silverton to Bakers Bridge.
But many people familiar with the basin say the EPA, which could see massive budget cuts under the Trump administration, should focus on the high metal content waters of Cement Creek, where 13 of the 48 sites are located.
“If measurable improvements to water quality and aquatic habitat are important goals, then the EPA needs to put their money toward making major reductions in metal loading that can only be achieved by addressing the major drainage mine sources located near Gladstone (i.e., Gold King, Red & Bonita, American Tunnel and the Mogul mines),” Bill Simon, co-founder of the Animas River Stakeholders Group, wrote in an op-ed to The Durango Herald.
Treatment options for the American Tunnel are a great unknown, Bowen said.
Some have called for a complete draining of the tunnel, which could take decades and cost a lot of money to treat discharges. Others have suggested placing bulkheads on all the mines in the area.
Bowen said the EPA first needs to understand the hydrology of the area. The new monitoring well that is expected to be installed by August will be a key tool in that effort because it will provide insight about how much water is behind the bulkheads, he said.
“There’s strong indications that these systems are related, but there’s not enough evidence to say it’s immediately connected,” Bowen said.
Sunnyside Gold Corp. has long contended there is no connection between the American Tunnel and any other mine networks in the area.
The American Tunnel drains about 100 gallons of acid mine waste water a minute, which flows right by the EPA’s temporary treatment plant into Cement Creek.
The temporary treatment plant takes discharges only from the Gold King Mine, which is now discharging at about 620 gallons a minute. The EPA said it may consider treating other mine discharges upon further evaluation.