Thousands of mines with toxic water lie under the West

DENVER -- Beneath the western United States lie thousands of old mining tunnels filled with the same toxic stew that spilled into a Colorado river last week, turning it into a yellow concoction and stoking alarm about contamination of drinking water.

Though the spill into the Animas River in southern Colorado is unusual for its size, it's only the latest instance of the region grappling with the legacy of a centuries-old mining boom that helped populate the region and left buried toxins.

Until the late 1970s, there were no regulations on mining in most of the region, meaning people could dig a hole wherever they liked and search for gold, silver, copper or zinc.

Abandoned mines fill up with groundwater and snowmelt that becomes tainted with acids and heavy metals from mining veins that can trickle into the region's waterways.

Experts estimate there are 55,000 such abandoned mines from Colorado to Idaho to California, and federal and state authorities have struggled to clean them for decades.

The federal government says 40 percent of the headwaters of Western waterways have been contaminated by mine runoff.

Last week, the Environmental Protection Agency was trying to staunch leakage from a gold mine -- not worked since 1923 -- high in the San Juan mountains of southern Colorado.

But workers moving debris from the mine tunnel accidentally opened the passage, leading to a million gallons of sludge spilling into a creek that carried it into the Animas River.

From there the discharge headed toward the Colorado River, which provides water to tens of millions.

"The whole acid draining issue is something we struggle with in the western United States," said Bruce Stover, the Colorado Department of Mining official in charge of dealing with abandoned mines in that state.

One of the complicating factors is money and legal liability.

Cleaning the mines is costly, and the Clean Water Act says anyone who contributes to pollution of a waterway can be prosecuted for a federal crime, even if the person was trying to clean pollution.

That's kept environmental groups from helping the EPA treat water and tidy up mines.

Groups for several years have been pushing for a federal law that would let so-called "Good Samaritan" groups help with cleanup without being exposed to liability.

"There's still a whole generation of abandoned mines that needs to be dealt with," said Steve Kandell of Trout Unlimited, one of the organizations backing the bill.