SILVERTON – It’s been more than a year since the Superfund site near Silverton was formally declared, and while the cleanup is expected to take years, Environmental Protection Agency officials highlighted some of the work accomplished.
“We’ve spent a lot of time here and developed quite a team,” said Rebecca Thomas, project manager for the Bonita Peak Mining District, north of Silverton.
In the most recent update Monday in Silverton before about 20 people, Thomas said EPA has been conducting a lot of high- and low-flow investigations, including sampling and monitoring a dozen stream gauges throughout the basin.
EPA will hold similar meetings 5:30 p.m. Tuesday in Fruitland, New Mexico, and 6:30 p.m. Wednesday at the Durango Public Library, 1900 East Third Ave.
One of the more notable projects was at the Gold King Mine, where, in August 2015, an EPA-contracted crew caused a mine blowout, releasing 3 million gallons of heavy-metal laden water in the Animas and San Juan rivers.
The EPA at that time breached the outer entrance of the Gold King Mine, yet concerns lingered another collapse further back in the mine also could have occurred – holding back a significant amount of water.
However, EPA completed a horizontal well within the last 14 days, and, Thomas said, that it didn’t find any impoundments of water further back in the historic mine.
“That was good news,” Thomas said.
The EPA has undertaken several measures to decrease the chance of a mine blowout, including stabilizing the mine’s portal and installing flow line structures to control discharges.
Thomas said the Gold King Mine continues to see steady discharges of about 620 gallons-a-minute of mine wastewater, which is treated by a temporary water-treatment plant.
The EPA has still not identified a long-term location for the sludge generated by the treatment plant, Thomas said.
“We still have a sludge issue and continue to seek out a repository, hopefully within the district,” she said.
Other EPA personnel gave presentations on the many studies happening around the basin.
Brian Sanchez, an EPA ecotoxicologist, said the agency continues to conduct its ecological risk assessment, which looks at the potential risk mining contamination poses to the area.
As it pertains to soils, Sanchez said lead and zinc emerged as the heavy metals that pose the most risk. Out of 35 mine sites included in an evaluation, nearly 90 percent ranked in the high risk category.
Out of 12 campsites, three also fell into the high-risk category.
Sanchez, however, said rankings are somewhat “arbitrary” and will be used, rather, to function as a framework for the agency as it drafts a more complete priority list of sites the EPA wants to address.
Thomas said the final ecological risk report should be complete by 2019. A human health risk is expected to be finished by the end of the year, and a water-quality report should be released sometime in spring 2018.
“We’re really encouraged on the amount of data we’ve collected the past two years,” Thomas said. “We have a legacy of decades of mining, and that will take years to understand.”
However, that won’t stop the EPA from taking action when and where it can, she said.
The EPA did a short-term test of closing the Red & Bonita Mine bulkhead, but did not close the valve for good. Thomas said some additional grouting and study needs to be taken before that can occur.
EPA also sampled dust kicked up by ATV use as part of its human health risk assessment, and recently harvested two deer to test for any impacts mining contamination may have on wildlife.
Crews were unable to drill a monitoring well at the American Tunnel (the main drainage for the vast Sunnyside Mine workings) with the onset of winter fast approaching, Thomas said.
jromeo@durangoherald.com