Why the Gold King Mine Spill Could Still Cause Ecological Damage

November 2, 2015 | Sarah Tse

Animas river following the Gold King mine leak
Photo credit: Riverhugger/Wikipedia (CC BY-SA 4.0)

Despite clean-up efforts and a steady dilution since the original spill, the contamination from the Gold King Mine in Silverton, CO still poses an ecological threat.

For a brief period in early August, the Animas River in Southwest Colorado turned an alarming shade of orange. Obviously, this was not its natural state. On the morning of August 5, 2015, it still looked quite normal — clear water and all. But that clear water was hiding a host of problems, invisible to the naked eye.

The Rocky Mountain area has long suffered from pollution by old mines. A century ago, miners dug and drilled with abandon throughout Silverton, Colorado. Once they depleted the mines of precious metals, they moved on without a second thought. But all those abandoned mines have created a toxic legacy that is only now coming to national attention.

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For one thing, early miners usually dumped tailings, or waste materials full of toxic heavy metals, into streams and rivers. These heavy metals have accumulated in the riverbeds of the Animas River, with insidious effects on local fish populations. Then there’s also acid mine drainage, which forms when groundwater, exposed by mining shafts, turns into sulfuric acid and leaches even more heavy metals out of mines and into nearby waterways.

EPA workers have been cleaning up the Red and Bonita mines this summer, but when they got to the Gold King mine, disaster struck. While investigating the mine’s existing leak on August 5, they accidentally knocked through debris that had been acting as a dam. The dam burst, releasing a torrent of bright mustard-hued water full of arsenic, lead, cadmium, and other dangerous materials.

Samples taken immediately after the incident showed alarming levels of toxic materials, some at hundreds of times the safe level for consumption. The EPA took action by setting up sediment retention ponds that would contain the water long enough for some of the toxins to deposit to bottom. Since the initial spill, the metals have largely diluted and settled to the riverbed, and the Animas river has been declared safe for drinking and recreation once again. A fish survey completed three weeks after the spill did not show any critical effects from the contamination.

But just because the concentrations of these toxins are no longer high enough to immediately sicken us, doesn’t mean the threat has passed. Locals who enjoy swimming in the river put themselves at risk of prolonged exposure to the contaminants, the effects of which have yet to be evaluated. Every time something stirs up the sediments on the riverbed, the toxins lying dormant there will also surge up into the water column.

Caption: Thanks to biological magnification, toxins become more concentrated as they travel up the food chain.

These metals may also accumulate up the food chain in a process called biological magnification. At the bottom of the food chain, insect larvae consume trace amounts of the toxins that aren’t nearly enough to harm them. On the next level, minnows eat large amounts of the larvae and accumulate more of the toxins in their tissues. Finally, larger predators absorb the poisons contained in all the fish they consume. By the time a fat, juicy trout reaches a person’s dinner plate, its tissues contain heavy metals at dangerously high concentrations. This process happens to all kinds of pollutants, and since humans are at the top of most food chains we are especially at risk of ingesting lethal amounts.

Although the river appears to have largely recovered to its pre-spill conditions, this incident has forced local and national environmental agencies out of their complacent attitude regarding the hazards posed by abandoned mines. The insidious effects of ongoing acid mine discharge have plagued this region for decades, and the river doesn’t have to turn orange to endanger human lives and the ecosystem.

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