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High mountain streams not always as pristine as they appear
Rocks around the abandoned Pennsylvania Mine show the characteristic red discoloration associated with acid mine drainage.
Peru Creek above the abandoned Pennsylvania Mine.
By Summit Voice
SUMMIT COUNTY — The Snake River, flowing from headwaters in the mountains high above Keystone, is one of several streams in Colorado that’s been identified as being affected by naturally occurring acid rock drainage.
The new report from the Colorado Geological Survey looks at streams in eleven different headwater areas of Colorado where surface water is acidic and has high concentrations of metals upstream of any significant human impacts.
Frequently, acid rock drainage from natural sources and mine sites combine to cause severe downstream water quality problems. In these situations it is important to distinguish the natural, or background, water quality so that realistic clean- up goals for water quality can be set.
Peru Creek and the Snake River are a perfect example of this combination. The abandoned Pennsylvania Mine is thought to contribute a significant amount of acid mine drainage to water that is already tainted. As a result, the water downstream is toxic to trout and other aquatic organisms. Various agencies and groups have been wrestling with cleanup scenarios for decades.
The research explains that rocks in parts of Colorado’s mineral belt were altered by intensely hot water circulating in the earth’s crust, often associated with volcanic activity during Colorado’s geologic past.
These hydrothermal alteration changed the composition of the rocks by dissolving some minerals and depositing others. In the affected areas, the process deposited metal-sulfide minerals, commonly pyrite (fool’s gold), in the rocks.
When these rocks are exposed at the surface, they interact with oxygen and the iron sulfide “rusts” to form iron oxide minerals, creating striking yellow, orange, and red colors — similar to the oxidation of metal in an old rusty car.
Acid rock drainage occurs when the sulfur that is displaced by the oxygen combines with water to form weak sulfuric acid. The acidic water then dissolves minerals from the bedrock, often adding significant amounts of dissolved metals to these headwater streams. Natural acid rock drainage has been active in Colorado for thousands, possibly millions of years.
State geologists collected 101 water samples from headwater areas and identified specific streams in the following areas as being affected by natural acid rock drainage: Silverton area, Lake City area, Platoro-Summitville area, Kite Lake area and East Trout Creek in the San Juan Mountains, the La Plata Mountains, Rico Mountains, headwaters of Lake Creek south of Independence Pass, the Ruby Range near Crested Butte, Red Amphitheatre near Alma, headwaters of the Snake River in eastern Summit County, and the Rabbit Ears Range.
Through detailed geologic mapping, the study characterized the type and intensity of hydrothermal alteration and correlated the geology with surface-water chemistry. Many of the areas exhibiting intense hydrothermal alteration also contain historic mine sites.
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Filed under: Colorado, Environment, rivers, Summit County Colorado, Summit County news, water Tagged: | acid mine drainage, acid rock drainage, Colorado Geological Survey, Environment, Peru Creek, Snake River, Summit County Colorado, Summit County News, water quality
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This article brings up the issue of pollution resulting from past mining operations, and with the seemingly urgent desire with certain people to get into the Fracking business today, it’s important to make sure the same result doesn’t occur from said process. Caution should be the exception as well as the rule in this endeavor. As we see today the aftermath, we don’t need to see or experience the same thing later in the future.
Where did the acid come from? California. Not the mines, the acid rain from California collected in the mines leeching out heavy metals I know this because the EPA shut down the mine where both my father and I worked.
The EPA was too chicken to correct the real problem. Californians should not be allowed to emigrate to any other state but should be required to live in the filthy wallow of liberalism and destruction they didn’t oppose in California but they left California to escape! And what’s worse is they spread the same liberal crap wherever they go!
How much horse manure does it take to ruin a birthday cake?
Mr Ralph Reagan,
The acid came from a chemical reaction the occurs when ground water interacts with iron pyrite, naturally occurring in the ground of the Colorado mineral belt. The reaction elevates the Ph of the ground water that in turn allows for the leeching to occur. This entire issue was increased from the naturally occurring levels due to hard rock mining in the area. I worked at a water treatment plant for 4 years treating the A.M.D. that came from the 12 miles of flooded tunnels in the hill. We lowered the Ph and extracted the hazardous metals to improve the downstream fishery. Mr Reagan if you would just shut off Fox News and read about geology and chemistry you would maybe learn something and would fight for a solution and not sanctioning of our fellow Americans regardless of state origin.