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ASHEVILLE — In the aftermath of the 40,000-gallon coal ash spill in February at a power plant on the Dan River in eastern North Carolina, Duke Energy and North Carolina environmental regulators have said the two dams that containing coal ash at the company’s Asheville power plant are sound.
Of the three dams at the 376-megawatt coal-burning Asheville power plant, two contain ponds of coal ash. Each of the coal ash ponds have a storage capacity of about 450 million gallons — making the total possible capacity reaching more than 900 million gallons of wet coal ash across 91 acres, according to a 2009 Environmental Protection Agency report.
One of the structures is more than half-a-century old. The other is more than three decades old. At 60 feet tall and 95 feet tall, respectively, the earth-and-rock dams are visible from Interstate 26, the only thing separating the structures from the nearby French Broad River.
“The dams are safe and well maintained and operate as they were designed to,” said Jason Walls, Duke’s district manager for the Asheville area. Walls said Duke conducts monthly visual inspections of the dams or anytime after a heavy rainfall event. In addition, he said, an outside firm conducts an inspection and analysis of the dams annually.
Within the past several years, state regulators appear to have completed mandated inspections of the coal-ash dams at Duke Energy’s Asheville plant. They have not issued any violations as a result of those inspections.
The total storage capacity of the 1964 pond is 449 million gallons. The total storage capacity of the 1982 pond is 456 million gallons. The TOTAL storage capacity of both ponds is 905 million gallons.
Still, environmental groups and state legislatures are worried.
Sen. Tom Apodaca, a Republican from Henderson County who chairs the Senate’s powerful Rules and Operations Committee, told The Charlotte Observer in February that the ash ponds at Duke’s Asheville power plant “frightens the hell out of me, because if it breaks it would go across Interstate 26 and into the French Broad River.” He said other legislators are similarly unnerved, the newspaper reported.
Since the February spill, environmental regulators across the state have come under fire, with legislators reviewing the event and state regulators launching a press campaign about their response. According to WRAL, state environmental regulators have known for about five years that some coal-fired power plants in North Carolina didn’t have required permits to discharge stormwater into nearby lakes and rivers, according to internal emails. A federal grand jury is said to be investigating the spill this month, and federal investigators have subpoenaed regional environmental officials across the state – including those at the Asheville regional office.
Susan Massengale, a spokesperson for the N.C. Department of Natural Resources, said the agency will be conducting a comprehensive inspection of coal ash containment at the Asheville this week to look at all aspects of coal ash ponds and aspects of dam construction. Between Feb. 20 and March 1, state dam safety inspectors also conducted a visual inspection of the spillways surrounding the ash ponds throughout North Carolina, including the Asheville plant.
But what have inspectors known about the Asheville structures, and what – if anything – could this increased scrutiny mean?
Two ‘high-hazard’ dams
Not all the dams at the Asheville plant contain coal ash. One, the northern dam, contains Lake Julian, and its waters are used in the cooling process of some of the plant’s operations. Another dam contains a retired coal ash pond. According to state dam inspection records, it was built in 1964 of earth-and-rock fill. The third contains an active coal ash pond, which was built in 1982 and is made of earth fill. Each of the three dams faces Interstate 26.
The two dams containing coal ash are considered “high hazard” dams, which refers to the potential of damage downstream should a break occur, rather than the condition of the dam or the toxicity of the material that the dam contains.
The National Inventory of Dams Hazard Potential Classification system rates dams as “high hazard” if, in the event of a failure, it is probable that one or more people would die, that more than $200,000 of economic damage would occur and that there is a probable loss of human life due to a breached roadway or bridge below the dam.
The Land Quality Section of the Division of Energy, Mineral and Land Resources, a division of the N.C. Department of Environment and Natural Resources, regulates the dams, not their contents. According to Steve McEvoy, state dam safety engineer, inspectors have not seen any deficiencies that would signal an imminent failure. They were last inspected on April 15, 2013. [See below for copies of the inspection reports.]
McEvoy said “the dams at the Asheville plant are assessed as good,” based on inspections conducted by state regulators. He said that the 2013 inspections found no issues that would cause regulators to be concerned or to take action.
However, a DENR press release said that state regulators plan to conduct detailed inspections of all Duke Energy’s coal ash facilities in North Carolina this week. Regulators will also request that Duke Energy provide engineering and emergency action plans and maps for the facilities and videos of the insides of all pipes at the impoundments.
Tracy Davis, director of the Division of Energy, Mineral and Land Resources, said that running cameras through every pipe and getting the plans for each site will give regulators a better understanding of the construction of the spillways and the integrity of the dams.
Inspections found ‘wetness’ on downstream slope
Robin Smith, former assistant secretary of DENR who is now an attorney, said that, in 2009, the N.C. General Assembly removed exemptions of coal ash dams from state inspections in the wake of the TVA dam breach in 2008 in Tennessee. Senate Bill 1004, signed by Gov. Bev Perdue in 2009, required that dams enclosing coal ash ponds be inspected every two years by state regulators.
“The dam safety program went through a process of looking at existing impoundments to try and get a look at what the risk may be and look at obvious problems,” Smith said. “It’s clearly important to keep an eye on the condition and understand what the risks are. The TVA spill was the worst case scenario, but it did happen.”
An April 2013 state inspection of the 1982 dam, which contains the active coal ash pond, revealed no problems that required immediate attention, according to an April 19, 2013, notice of inspection delivered to Duke Energy by DENR.
However, the letter indicated that the inspection found wetness on the downstream slope of the dam and that excessive wetness and seepage can cause failure of the dam due to internal erosion and/or embankment sliding.
A 2012 and 2011 inspection of the same dam identified an identical concern. Regulators did not issue any violations following those inspections.
That same month, a state inspection of the older dam containing coal ash waste did not identify concerns of excessive wetness or seepage.
McEvoy said that it is very difficult to handicap the percent chance of the failure of a dam.
The Asheville pond dams are also rated by the EPA. The active pond dam was given a condition rating of “satisfactory” and the inactive dam was rated as “poor.” A poor rating does not necessarily indicate that the dam is unsafe or structurally deficient.
According to Duke Energy’s website, the poor rating was due to the lack of original engineering design documents and the need for additional stability analyses. Minor maintenance deficiencies were documented, but no issues of immediate concern were identified. According to Duke Energy and EPA records, the rating is not a direct indicator of the structural integrity or soundness of the ash impoundment. Many of the maintenance items identified have been completed, according to EPA records. The remainder of the recommendations are currently being addressed by Duke Energy.
Dike failure reported in 2012; budget cuts this year
Still, environmental groups are concerned about the impact of an unexpected dam failure.
In October 2012, a large internal dike that divides one of the coal ash ponds failed after a heavy rain event at the Asheville plant. Duke energy says that no coal ash waste was released into the French Broad River from the failure of the dike.
While a dam failure may be difficult to predict, environmentalists say that seepage of contaminated water from the coal ash ponds into the French Broad River is also at the top of their list of concerns.
Jason Walls, of Duke, said that “dams are inherently designed to seep and water quality sampling continues to show we are operating within our permits.” He added that Duke is currently working on a coal ash waste management strategy. “We recognize that the way we have managed coal ash waste will not be the way we manage it in the future.”
Smith said that her concern is that the state’s water quality division is stressed for resources and may have a difficult time monitoring the level of seepage in the future. The transfer of the Division of Water Quality’s programs into the Division of Water Resources passed in the most recent state budget may impact the ability of the agency to deliver the kind of oversight needed, she added.
Smith said that the combined budget of the two programs mandates a savings of $2 million, or roughly 12.5 percent of the current budget, by June 2014.2013 Asheville coal ash dam inspection (1) (PDF)
2013 Asheville coal ash dam inspection (1) (Text) 2013 Asheville coal ash dam inspection (2) (PDF)
2013 Asheville coal ash dam inspection (2) (Text)
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