The U.S. Environmental Protection Agency has released information showing there are 584 coal ash dump sites across the country — almost twice as many as previously identified. The facilities are located in 35 states and concentrated in Appalachia, the Southeast, Midwest and Intermountain West.

The release [PDF] came late last Friday in response to a Freedom of Information Act request. The information released reveals ownership, location, hazard potential, year commissioned, type and quantity of coal combustion waste disposed, dates of the last regulatory or company assessment and in some instances whether an unregulated discharge of ash has occurred.

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However, some critical data is missing because companies are claiming it’s confidential business information. Duke Energy, Progress Energy and the Southern Co.’s Alabama Power and Georgia Power are among the corporations withholding information on 74 coal ash dump sites, including some of the country’s largest ash dumps.

“Some utilities — notably Duke and Southern Companies — are hiding the ball, withholding data on their ash ponds that their competitors have already provided to EPA,” said Eric Schaeffer, executive director of the Environmental Integrity Project, which submitted the FOIA request along with the environmental law firm Earthjustice and the Sierra Club. “Let’s hope that EPA’s enforcement program puts a stop to these bogus claims of ‘confidentiality,’ and compels the disclosure of data that companies are required to report.”

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States with coal ash sites included in the list are as follows: Alabama, Arkansas, Arizona, Colorado, Delaware, Florida, Georgia, Iowa, Illinois, Indiana, Kansas, Kentucky, Louisiana, Massachusetts, Maryland, Michigan, Minnesota, Missouri, Mississippi, Montana, North Carolina, North Dakota, New Mexico, New York, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Utah, Virginia, Wisconsin, West Virginia and Wyoming.

In March, the EPA sent letters [PDF] to hundreds of power generating facilities requesting information about coal ash surface impoundments. The agency was responding to the disaster that occurred last December at the Tennessee Valley Authority’s Kingston power plant in eastern Tennessee, where a dam failure released over 1 billion gallons of toxic coal ash sludge into a nearby community and river.

Coal ash sites contain harmful levels of arsenic, lead, mercury and other toxins, which can leach out and contaminate drinking water sources.

The EPA data shows that most of of the dump sites are over three decades old, raising questions about the structural integrity of the dams and the adequacy of the liners to prevent harmful chemicals from migrating into water sources. It also shows regulatory inspections of the dams by state and federal agencies are infrequent or nonexistent.
 
In addition, EPA’s data reveal that many of the wet dumps are very large, with over 100 exceeding 50 acres and numerous sites covering several hundred acres. Furthermore the largest dumps tend to be the older sites with the least amount of protection.

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In response to another information request by the same three environmental groups, EPA recently identified 49 “high hazard” coal ash dump sites, where a failure would be likely to cause loss of life. The Department of Homeland Security had initially determined that the sites presented such a threat to nearby communities that revealing their location would present a national security risk.

EPA Administrator Lisa Jackson says her agency expects to release a proposed federal rule governing disposal and storage of coal ash by year’s end. Regulation is currently left up to an uneven patchwork of state laws.

(A version of this story originally appeared at Facing South.)