North Carolina leads the nation in the number of toxic ash waste pits at coal-burning power plants, according to a new report by a coalition of environmental groups.

The state is home to at least six coal ash pits that store dangerous levels of arsenic, lead, mercury and other toxins, according to the report issued today by Earthjustice and Environmental Integrity Project. Only Pennsylvania has as many sites with dangerous accumulations of waste from coal-burning power plants, the report said.

The groups are urging the U.S. Environmental Protection Agency to step up enforcement at the sites, which have operated for decades out of public eye until a massive spill in December 2008 released tons of toxic sludge in Tennessee.

"The EPA has never gone out and actively investigate these sites," said Jeff Stant, director of the Coal Combustion Waste Initiative at the Environmental Integrity Project. "The delay is unconscionable when there's this much data showing this much damage."

State officials are moving ahead with plans to monitor groundwater contamination around coal ash pits used by Progress Energy and Duke Energy to store waste from coal-burning power plants.

The N.C. Division of Water Quality has asked the state's electric utilities to propose locations for installing wells to monitor groundwater near the pits. The ash pits contain metals such as lead, mercury and arsenic that are left over after coal is burned in power plants.

Risks posed by ash pits were largely ignored until a massive spill took place two years ago at a pit in Tennessee, where a dam gave way, releasing tons of the toxic sludge.

Since then federal regulators have increased oversight and North Carolina officials have taken steps to begin monitoring ash pit safety. The state Division of Water Quality plans to monitor groundwater for potential contamination.

The U.S. Environmental Protection Agency last year reviewed 43 ash pits around the country. Five Progress pits in Chatham County received "poor" ratings as did one near Asheville. The EPA urged the company to analyze the sites for structural stability and to make other fixes.

The U.S. Environmental Protection Agency generally likes what the state Division of Water Quality proposes to do to deal with the controversial practice of allowing those who restore a stream or wetlands to sell credits against development that destroys more than one site.

This double dipping, as critics call it, became a hot issue this week when The News & Observer reported that the state is paying a Maryland company $911,000 for restored sites that the state several years ago had previously paid $1.8 million.

Officials are calling for reviews of the state Ecosystem Enhancement Program, which spent the $911,000. The state Division of Water Quality, meanwhile, is proposing new rules that would prevent such double payments. Both agencies are under the state Department of Environment and Natural Resources.

At a water quality division meeting today, an EPA representative said the federal agency finds the proposed rules "largely consistent" with federal policy because they do not allow a restored site to be double counted against multiple, similar-sized parcels of damaged streams or wetlands.

But the representative, Kathy Matthews, said the EPA does not have standing to challenge state restoration programs, which have contributed to the double dipping issue because they resemble the federal restoration requirements.

Water quality officials took comments at the meeting from environmentalists, developers and companies in the environmental restoration business. The division expects to introduce the proposed rules to the Environmental Management Commission next month for approval.

The state Division of Water Quality is standing by its February ruling that allows Durham County to proceed with resetting part of the Jordan Lake watershed boundary on the basis of a developer-commissioned survey.

The state Environmental Management Commission had asked DWQ's response to questions raised by Durham resident Melissa Rooney, Durham Planning Commission Chairman George Brine and Haw River Assembly Director Elaine Chioso.