Concentrations of metals in the upper Animas River and its main tributaries, Cement and Mineral creeks, pose problems for invertebrates, fish and the animals that prey on them, an Environmental Protection Agency study finds.
The study is a draft, and the conclusions are conservative, the report says. The results, released this week, are based on dozens of surface water samplings from May 2009 and May 2012.
Samples were taken before the spring runoff (February to April), during runoff (May and June) and post-runoff (July to November).
Samplings of dissolved metals varied from stream to stream, but the list included aluminum, cadmium, copper, iron, zinc, lead and manganese.
Peter Butler, a coordinator of the Animas River Stakeholders Group that is trying to mitigate toxic-metal discharge from abandoned hard-rock mines around Silverton that reach the same waterways, didnt know Friday if the group would respond to the EPA study.
I think some individual members may, said Butler, who also is chairman of the state Water Quality Control Commission.
The stakeholders group has an email list of 50, including public and private agencies and individuals, all of whom were notified, Butler said.
The goal of the Screening-Level Ecological Risk Assessment was to select contaminants of potential concern and assess the potential for risk to different types of organisms exposed to mining-contaminated surface water, sediment and food, the EPA said in its introduction.
Under study were the effects of dissolved metals on macro- and microinvertebrates, fish, birds that eat fish, and insects and mammals that feed on riparian plants.
Among its conclusions, the study found that:
Invertebrates would not survive in Cement Creek and would experience high stress in Mineral Creek and the Animas River in the vicinity of Silverton.
Fish also couldnt live in Cement Creek and would be under high stress in Mineral Creek and the Animas around Silverton.
The level of dissolved metals has the potential to cause significant risk to animals such as the kingfisher, American dipper and the muskrat.
An estimated 800 gallons a minute of toxic metals flow into Cement Creek, a tributary to the Animas at Silverton. The runoff is from background sources and from mines that operated around Silverton from the late 1800s to 1991.
The Animas River Stakeholders Group formed in 1994 to reduce or eliminate toxic mine drainage. The group has secured or removed tons of mine tailings from harms way. But projects involving water present the risk of ongoing liability that no one is willing to chance.