MOUNTAIN ISLAND LAKE - From its crook in the Catawba River, the Riverbend Steam Station has gobbled coal by the rail car since 1929, making electricity -- and mountains of ash.

Riverbend and Duke Energy's seven other coal-fired plants in the Carolinas disgorge 2.2 million tons of ash a year. Two-thirds is dumped in landfills and ponds at the plants, an old practice that has begun to worry regulators.

Coal ash is loaded with metals that can contaminate groundwater and lakes such as Mountain Island, the chief water supply for more than 850,000 people. Millions of gallons of water a day flow from Duke's ash ponds into the Catawba.

State records show that arsenic, boron and selenium -- all toxic in high concentrations -- have been found at potentially unsafe levels in groundwater under Duke's ash basins.

Duke says there is no evidence that water supplies have been harmed. Tests support that at Mountain Island. But until recently, groundwater has gotten little scrutiny.

The Environmental Protection Agency first raised the question in 2000, acknowledging "gaps" in the oversight of ash basins at the nation's 440 power plants. EPA is soliciting public comment to find "practical and safe solutions" for monitoring ash, an agency spokesman said.

As part of an industry response, Duke is voluntarily installing wells to detect tainted groundwater at its Carolinas plants. Fifty monitoring wells have been installed since 2005, and 33 will be added by 2010.

"It's better to know," said Duke scientist Allen Stowe, "than to not know."

The known hazards

Critics say the industry efforts, and recent North Carolina legislation, don't safeguard public health after decades of ash dumping.

Coal ash contaminants, which can accumulate over time, are known to have killed fish, deformed bullfrogs and tainted groundwater near four Carolinas power plants, including one owned by Duke, the EPA says.

Many of the minerals found in ash occur naturally in Piedmont soils. Some, such as iron and manganese, aren't considered dangerous. Duke sells 700,000 tons of ash a year for use in making concrete products.

Other minerals, if ingested in high concentrations in water, pose risks. Selenium can cause neurological problems; arsenic can cause cancer. Boron can damage the liver, intestines and brain.

Groundwater contamination at Duke's biggest coal plant, Belews Creek, 85 miles northeast of Charlotte, has been persistent enough to force Duke to close an ash landfill this year.

In the 1970s and 1980s, selenium-laced discharge from a Belews ash basin killed 16 of the 20 fish species in Belews Lake, an EPA report says. A state advisory warning against eating fish from the lake was in place from 1993 to 2000.

Unlined ash basins -- Duke's plants have 14 -- are the type most likely to pollute groundwater, according to another EPA study. Cancer risks from drinking groundwater tainted by arsenic from unlined basins are 900 times higher than the government says is acceptable.

Loophole in new law

North Carolina legislation, enacted last year, allows new ash landfills to be built on top of old basins. The new landfills must be lined to prevent leaks and keep out rain, which can leach metals into the ground from old ash.

But the industry-supported measure doesn't make utilities determine the extent of contamination from the old basins. Tainted groundwater may move over time, potentially reaching offsite wells.

"They're forgetting a huge step there," said attorney Lisa Evans of Earthjustice, a nonprofit law firm in Oakland, Calif. "That seems like a way for the utilities to sweep under the rug any problems they might have with old surface impoundments."

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