The earthen dam at one of the coal-ash ponds at the Cape Fear power plant in Chatham County was damaged when Duke Energy workers pumped out wastewater there in an unauthorized operation over the past several months, state regulators said Friday.
Duke Energy says the crack, which it told regulators about Thursday, began as a “small depression” two weeks ago on one of the five ponds at the closed plant. Workers monitoring the crack said it hadn’t gotten bigger, according to the company, until Thursday – when it suddenly grew to a 3- to 4-inch wide gap and was about 35 feet long.
No wastewater from the ash lagoon spilled through the crack, the company said. The N.C. Department of Environment and Natural Resources said the structure, which was built in 1985, didn’t appear to be in imminent danger of failure, but it was monitoring repair plans.
Duke is allowed to discharge a certain amount of wastewater that has been tested for safety from the ponds into a tributary of the Cape Fear River, which supplies drinking water to several municipalities downstream. But DENR determined that the pumping operation exceeded reasonable maintenance methods, and sent 61 million gallons of wastewater into the river over several months. No water quality problems have been reported, but the company faces substantial fines.
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So far, DENR has not issued a violation notice for the dam fissure. On Friday, the agency approved the company’s emergency fix to the growing crack at the plant in Moncure and will require a long-term repair be developed. Duke says it is taking those measures “out of an abundance of caution” but stresses the dam remains safe and structurally sound.
“They are just trying to patch up an outmoded, worn out, unlined pit and an old defective dam, when DENR and Duke Energy should be moving the coal ash away from the Cape Fear River to safe dry storage in a lined landfill,” said Frank Holleman, an attorney with the Southern Environmental Law Center, which has been pushing regulators to do more to force the utility to clean up the plants. “This is an approach that will not protect the public or the Cape Fear River from continued risk and toxic pollution.”
State regulators found the pumping operation on March 11 during a week of intensive inspections at all 14 of Duke’s coal ash sites in the state. The day before, an environmental group called Waterkeeper Alliance photographed from an airplane two pumps at two ponds at the Moncure site, and provided the photos to reporters later in the week.
Duke said crews had been lowering the water level in the ponds to do maintenance work on vertical spillway pipes called risers. The company said it pumped the water into authorized outlets and that it monitored the quality of the water.
But regulators said Thursday that the process Duke used bypassed the risers where the water should have gone and too rapidly reduced the water level in the ponds, preventing it from being properly treated. The company has 30 days to respond, and is subject to substantial fines.
On Friday, DENR explained problems were compounded when Duke workers moved loose soil on top of a compacted embankment to provide a platform for equipment and vehicles in the pumping operation. That reduced the strength of the earthen basin in an area where the dam cracked.
The emergency fix calls for water to be removed using a horizontal pipe and a bladder to control the withdrawal. Duke will slowly excavate the area around the crack, and stabilize that area with fabric and riprap. The excavated material will be moved to another part of the basin.
The U.S. Environmental Protection Agency last year rated the dams at the five ponds at the Cape Fear plant as “poor.” Only one other pond, in Asheville, ranked that low in terms of structural integrity.
But DENR responded that inspections have not shown the dams were in bad enough shape to warrant repairs.