The Environmental Protection Agency has released a list of 44 "high hazard potential" coal ash waste dumps across the country. The "high hazard" rating applied to sites where a dam failure would most likely result in a loss of human life, the environmental agency advisory said, but did not assess the structural integrity of the dam or its likelihood of failure.
The list, released late on Monday, was compiled as part of the agency's inventory of coal ash sites after more than a billion gallons of ash broke through a dam at the Tennessee Valley Authority's Kingston Fossil Plant west of Knoxville last December. An engineering analysis of the failure, released last week, cited design problems like the height of the ash, among other factors.
Coal ash contains toxic materials like lead, arsenic, selenium and thallium, and such sites have been known to contaminate drinking and surface water.
The list identifies disposal sites in 10 states, including 12 in North Carolina, 9 in Arizona and 7 in Kentucky. There were no Tennessee Valley Authority sites on the list.
Senator Barbara Boxer, Democrat of California and chairwoman of the Senate Committee on the Environment and Public Works, received the list earlier this month and wanted to release it, but the Department of Homeland Security and the Army Corps of Engineers objected, citing security concerns.
The agency released the list after reviewing those concerns, a spokeswoman said.
The E.P.A. list was based on responses to a questionnaire that the agency sent to utilities and power plants. Environmentalists said they did not believe the list was complete because it was based on self-assessment.
"T.V.A. ranked its own dams, and it didn't rank any of its dams 'high hazard,'" said Lisa Evans, a lawyer for Earthjustice. A spokeswoman for the authority, Barbara Martocci, said she did not know who had classified the sites on the list. The classification system was developed by the National Dam Safety Program.
Ms. Evans said dam integrity was not the only or even the central problem with coal ash dump sites. In 2007, an E.P.A. report identified 63 sites in 26 states where the water was contaminated by heavy metals from such dumps, including three other Tennessee Valley Authority dumps. Experts say coal ash should be stored in lined landfills to prevent contamination, but the agency questionnaire did not ask whether the sites were lined.
David Merryman of the Catawba Riverkeeper Foundation in Charlotte, N.C., said two of the sites on the "high hazard potential" list discharge into Mountain Island Lake, the primary source of drinking water for 750,000 people in the Charlotte area. Those sites, which belong to Duke Energy, are unlined ponds.
Jason Walls, a Duke Energy spokesman, said the company's two newest coal ash ponds were lined.
Ten of the sites on the high hazard list belong to Duke Energy. But Mr. Walls said those sites were sound. For years, the E.P.A. has failed to regulate the disposal of coal ash despite promises to do so. Under the Obama administration, agency officials have pledged to issue regulations by the end of 2009.
But Stephen Smith, the director of the Southern Alliance for Clean Energy, said withholding the list, even temporarily, raised questions about the agency's intentions. "It's still unclear to me what the E.P.A.'s ultimate goal here is to do," Mr. Smith said. "Are they really going to aggressively regulate this material like they need to, or are they taking more of a hands-off approach?"