Duke cleared to repair coal ash dam at Cape Fear plant

North Carolina regulators have approved Duke Energy’s (NYSE: DUK) emergency plans to start repairing an earthen dam at a coal ash impoundment at the utility’s Cape Fear Steam Electric Station.

The utility on March 20 reported to the state Department of Environment and Natural Resources (DENR) that a crack had formed in an earthen dam at an ash impoundment at the Cape Fear facility. The impoundment, which was constructed in 1985, holds water mixed with coal ash.

DENR approved the utility’s emergency response plan on March 21. The plan calls for removing water from a horizontal pipe in the ash impoundment and using a bladder to stop water from exiting the pond through the pipe. Duke Energy also intends to slowly excavate part of the earthen dam where the crack has formed to address concerns that the soil in the dam could strike the nearby vertical pipe and lead to a rupture in the dam. Duke’s plans are to move the excavated material to another part of the ash impoundment and then stabilize the excavated portion of the dam with a layer of special fabric and riprap.

The plan directs Duke Energy to contact DENR and start alternative repairs if soil from the dam starts to move into the impoundment toward the vertical spillway pipe before or during the excavation work. The state will require that Duke Energy start working on a long-term repair for the area after the emergency response activities are completed.

Earlier on March 20, before DENR was notified about the crack in the earthen dam, the state agency cited Duke Energy for violating the conditions of a wastewater permit by pumping 61 million gallons of wastewater from the 1985 impoundment and another impoundment on-site that was constructed in 1978. The water was pumped over several months into an on-site canal that leads to a tributary and eventually the Cape Fear River.

The Cape Fear plant is located near Moncure, N.C., and began commercial operation in 1923. Two of the six coal-fired units were retired in 1977 and two more in 2011. The remaining two coal-fired units, along with one of four oil-fueled combustion turbine units on site, were retired in October 2012.

Duke Energy emphasized in a March 20 statement that despite the crack, the basin dam remains safe and structurally sound. A small depression was observed two weeks ago on the embankment of the basin, which was constructed in 1985. Site personnel have been monitoring it, and it had not changed in size or condition since it was discovered. However, company officials observed on March 20 that the depression had developed into a narrow gap about 35 feet long and three to four inches wide.

“Company engineers and engineering consultants responded to the site today and are making repairs,” Duke said. “No ash basin discharge has occurred, and out of an abundance of caution, the company is taking steps to prevent any potential for discharge.”

In a related matter, Duke Energy has identified another large coal ash deposit at its Dan River plant, the site of the initial ash spill on Feb. 2 that drew attention to the ash issue statewide, and has hired a contractor to remove the ash from the river. Earlier, the company identified a coal ash deposit behind the dam at the Danville water treatment intake. The second ash deposit is about one mile downstream from the Eden facility in the Dan River near the confluence of Towns Creek. Plans are to remove both deposits and continue identifying other deposits for removal. The Dan River plant was retired earlier this decade.

Duke also informed DENR recently that a contractor working on boat ramp repairs in the Dan River struck an abandoned dredge line, forcing water in the line to discharge to the river. Duke officials said none of the water contained coal ash residuals and that there several booms, a silt fence and curtains in the river at the boat ramp site. Duke staff calculated that if the entire length of pipe were full of water, the discharge could have been as much as 1,006 gallons. The unauthorized discharge could prompt enforcement action from the state.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.