Summitville Mine - Natural Versus Manmade Pollution

Natural Versus Manmade Pollution

Rocks in the Summitville area were millions of years ago subjected to acid-sulfate alteration, which causes the streams that drain the area to be naturally acidic and naturally high in metals. The very names of nearby creeks are evidence of poor natural water quality: Iron Creek, Alum Creek, and Bitter Creek. Mining at Summitville, by exposing more rock surface to weathering, increased acidity and concentrations of dissolved metals in runoff from the mine area. The degradation in Summitville runoff water quality has its origin in both decades-old mining structures, such as the Reynold’s adit, and the open-pit mining of 1985-1992.

Water runoff from the Summitville mine flows down Wrightman Fork, mixes with naturally acidic runoff from unmined areas, flows into the Alamosa River and flows out of the mountains into the San Luis Valley, where it is used for crop irrigation. A United States Geological Survey investigation arrived at three major conclusions:

”Extreme acid-rock drainage is the dominant long-term environmental concern at the Summitville mine and could have been predicted given the geological characteristics of the deposit. Extensive remedial efforts are required to isolate both unweathered sulfides and soluble metal salts in the open-pit area and mine-waste piles from weathering and dissolution.”

”It is likely that natural contamination adversely affected water quality and fish habitat in the Alamosa River long before and will continue to have adverse effects even when acid drainage from Summitville is remediated. Thus, reasonable natural conditions for the Alamosa River must be established in order to set realistic remediation conditions for the Summitville site.”

”Results of studies as of late 1993 indicate that mining at Summitville has had no discernable short-term adverse effects on barley or alfalfa crops irrigated with Alamosa River water. Remediation of the site will help to ensure that no adverse effects occur over the longer term.”