North Carolina is home to ore than a quarter of the nation’s coal combustion residue (CCR) impoundments that carry a “high hazard potential rating,” meaning that if the impoundment failed, it would probably cause loss of human life. This is according to an Environmental Protection Agency report released today, which designated 12 North Carolina coal residue impoundments with the rating. Ten are operated by Duke Energy; two are operated by Progress Energy. The EPA identified 44 such impoundments nationwide.

According to the EPA, the rating is not an indication of the structural integrity of the unit or the possibility that a failure will occur in the future; it allows dam safety and other officials to determine where significant damage or loss of life may occur if there is a structural failure.

There are three CCR impoundments in Spencer, which is near Salisbury. The following towns have two: Arden, south of Asheville; Eden, north of Greensboro near the Virginia-N.C. line; and Mt. Holly, just northwest of Charlotte. Belmont, which is south of Mt. Holly, Walnut Cove, north of Kernersville, and Terrell, which is near Lake Norman north of Charlotte, have one each.

Here’s more from the EPA announcement:

The EPA made its determination using the criteria developed by the National Dam Safety Program for the National Inventory of Dams. Hazard potential ratings are generally assigned by the State Dam Safety officials.

These impoundments contain fly ash, bottom ash, coal slag and flue gas desulfurization residue. CCRs contain a broad range of metals, for example, arsenic, selenium, cadmium, lead, and mercury, but the concentrations of these are generally low. However, if not properly managed, (for example, in lined units), CCRs may cause a risk to human health and the environment and, in fact, EPA has documented cases of environmental damage.

EPA’s assessment of the 26 facilities that have units with high hazard potential ratings continues to be an Agency priority. EPA has conducted on-site assessments, which are undergoing Agency review, at 11 of these facilities. The remaining 15 of these facilities have had state inspections within the past 12 months and EPA will be reviewing the reports from those inspections. EPA plans to make public the results of our assessments as soon as they are completed.