ALBUQUERQUE, N.M. — Contamination from abandoned mines leaching into the San Juan watershed didn’t begin or end with the 2015 Gold King Mine spill. For decades, thousands of abandoned mines in southwest Colorado have deposited heavy metals into streams and rivers that flow through New Mexico and Utah.
But the Gold King release, and $20 million in federal funding from the Water Infrastructure Improvements for the Nation Act, has spurred a multiagency group of scientists to identify pollution problem areas and improve water quality.
A water treatment plant installed after the spill treats acid mine drainage from Gold King.
The region was designated as the EPA Bonita Peak Mining District Superfund site in 2016.
Cleanup goals for the site include improving water quality, stabilizing mining source areas and minimizing unplanned releases, said EPA site project manager Christina Progess. The crews monitor groundwater as well as surface water.
“Monitoring … has given us a good head start to identify the major sources contributing to degraded water quality, so we can then identify and select remedies,” Progess said.
The EPA has proposed a permanent repository site near Silverton that would store sludge material removed from Gold King and the region’s other abandoned mines.
The WIIN Act funded a long-term water quality program for the San Juan watershed. Federal, state and tribal agencies collect water quality data at 39 sites along the river downstream from Gold King.
Shera Reems, an EPA project lead for the program, said the sites give agencies useful data about heavy metals and nutrients in the watershed.
Teasing out natural heavy metal sources from mine contamination, and then cleaning it up, is challenging in a mountainous region where mines were operated for decades before environmental laws were enacted.
“Water moves through fractures and cracks and faults in the ground,” said Rory Cowie, a hydrologist in Silverton. “Then you overlay that with a legacy of mining. Miners made Swiss cheese out of the mountains. All of these mine workings provide artificial pathways for water to move through a mountain.”
Most heavy metals from the Gold King plume ended up at the bottom of Lake Powell in Utah. But metals embedded in the San Juan riverbed may be stirred up during storms and spring runoff, said Steve Austin, a senior hydrologist for the Navajo Nation EPA water quality program.
“One of the things we’re trying to find out is the exact source of those (metals),” Austin said. “We want to know if that’s still left over from Gold King, or is it legacy contamination, or is it a continuing source from the mining district.”
Tests are continuing to measure the effects of heavy metals on the San Juan River’s fish and other aquatic wildlife.