Silverton: Acid mine drainage workshop

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Here’s a recap of yesterday’s acid mine drainage workshop held up in Silverton, from Dale Rodebaugh writing for the Cortez Journal. From the article:

An all-day workshop Saturday, one of the Moving Mountain Education Seminar series sponsored by the Mountain Studies Institute here, brought together 20 people interested in talking about and seeing the consequences of acid-rock drainage – the leaching of minerals into waterways. The workshop was led by David Borrok, a professor in the geological sciences department at the University of Texas at El Paso, and Rob Runkel, Richard Wanty and Andy Manning, all with the U.S. Geological Survey in Denver…

Workshop participants, who spent the day in Prospect Gulch a few miles north of town, got an eyeful and an earful of information. Runoff from numerous Prospect Gulch tributary watersheds feed Cement Creek, whose yellowish-colored channel is evidence of the presence of iron. In fact, the caravan stopped twice to view ferricretes – iron oxide formations with their telltale reddish hue that are created when iron reacts with water and air. An ancient ferricrete was visible in a creekside cliff. The other – a terraced formation adjacent to the stream – is still forming. Iron also is responsible for the color of terrain on nearby Red Mountain Pass – the reaction of pyrites (fool’s gold) with air…

The presence of ferricretes is evidence that some streams in the region were metal-rich and acidic before mining came into its own in the region in the late 1870s, Runkel said. “Minerals are stable in the ground but react with oxygen and water when brought to the surface,” Runkel said. “No one knows the quantity of metals in the water before mining started.” He cautioned that accurate hydrological studies are required to establish standards for cleaning up contaminated mines and waterways.

Later in the day Runkel demonstrated how the dilution of a tracer solution shows the level of metal loading from different sources. Runkel poured half a bucketful of rhodamine, an organic dye, into a rivulet on the upper reaches of Prospect Gulch. A sonde with a sensor that emits light at the same wavelength as the fluorescent dye traces the flow of the additive as it moves downstream. Similar studies have been conducted on Cement Creek and other streams above Silverton as part of the Abandoned Mine Lands Initiative, he said. At the Galena Queen mine, workshop participants tested the acidity and electrical conductivity of water in the shaft. They also compared the qualities of the mine water to surface water. At a well on a bench immediately above Cement Creek, Manning explained how to age-date water. Tritium, a radioactive isotope of hydrogen (one of the components of water) has a half-life of 13 years, meaning that in 13 years half of any tritium decays to become helium-3. Consequently, the ratio of tritium to helium in water indicates its age. Rain will have a high ratio of tritium to helium-3 while the reverse is true for slow-moving subterranean water. “Age-dating will tell how an aquifer works and how much water it can supply,” Manning said.

More water pollution coverage here.

One Response to Silverton: Acid mine drainage workshop

  1. jeff d says:

    Just saw this link now, and would have liked to attend. Looks like they covered some interesting topics. Anyone know where I can get advance notice of upcoming events of this kind?

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