Rivers hardest hit by Colorado mine waste spill to stay closed until Aug. 17

[August 11, 2015]  By Steve Gorman
 
 (Reuters) - Two rivers in Colorado and New Mexico hardest hit by contamination from toxic wastewater spilled from a defunct gold mine will remain closed to drinking water and irrigation intakes for at least another week, U.S. environmental officials said.

The San Juan River and its northern tributary, the Animas River, have been fouled by the release of more than 3 million gallons (11.3 million liters) of acid mine drainage inadvertently triggered by a team of Environmental Protection Agency (EPA) workers last week.

The discharge has continued to flow at the rate of 500 gallons (1,900 liters) per minute from the site of the century-old Gold King Mine, near the town of Silverton in southwestern Colorado, into a stream below called Cement Creek.

The wastewater has then washed into the Animas River and into San Jan River in northwestern New Mexico.

The orange-tinged contamination plume, containing heavy metals such as arsenic, mercury and lead, has dissipated through dilution as it spreads downstream, with its leading edge no longer visible from aerial surveys, the EPA said.
 

However, experts say a long-term concern is the deposit of heavy metals from the spill that have settled into river sediments, where they can be churned up and unleash a new wave of pollution when storms hit or rivers run at flood stage.

An unspecified number of residents who live downstream from the mine and draw their drinking supplies from private wells have reported water discoloration, but there has been no immediate evidence of harm to humans, livestock or wildlife, according to EPA officials.

Still, residents have been advised to avoid drinking or bathing in water drawn from wells in the vicinity.

Two Colorado municipalities, including the city of Durango, and the New Mexico towns of Aztec and Farmington have shut off their river intakes, the EPA said.

EPA officials said on Monday the Animas and San Juan rivers would remain closed until at least Aug. 17 to drinking, irrigation supply, fishing and boating as experts try to gauge safety risks posed by the spill.

Wastewater continues to pour from a tunnel wall accidentally breached by EPA crews last Wednesday but the concentration of heavy metals reaching local streams has diminished.

Emergency treatment of the effluent by diverting it into settling ponds before it empties into Cement Creek has reduced acidity and metal levels in the creek, the EPA said.

The creek's water quality was already badly degraded from a long history of acid mine drainage in the area, EPA officials acknowledge.

The conservation group American Rivers says Colorado has more than 4,000 abandoned mines, about 1,100 of them around Silverton, which it calls "ticking time bombs."

The Navajo Nation has also been affected. Its sprawling reservation is traversed by the San Juan River, which flows through southeastern Utah into Lake Powell. It was uncertain how far significant contamination from the spill would travel.

(Reporting by Steve Gorman in Los Angeles; Editing by Paul Tait)

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