Repairs to an ash pond pipe at Duke Energy’s Marshall power plant have raised concerns that contaminants could be released into Lake Norman.
State regulators this week said Duke could release water from the Marshall pond to patch a quarter-inch hole and a 5-inch hairline crack in the corrugated metal pipe. The 140-acre ash pond is the state’s largest.
The state ordered Duke to test the released water for potentially toxic elements found in ash. Those elements can’t exceed limits set out in a state discharge permit that lets Duke routinely drain excess water from the pond into Lake Norman.
Rick Gaskins, executive director of the Catawba Riverkeeper Foundation, says the permit has holes in it. It doesn’t set specific limits for some elements found in ash, including arsenic and mercury.
Gaskins says the more-than-normal volume of water released for the pipe repair could pose added risks.
“We may see higher (contaminant) concentrations coming out, and it may be stirring up things at the bottom” of the pond, he said. “This is an atypical situation.”
Marshall’s pond holds 22 million tons of ash. The Riverkeeper Foundation estimates that the pond can hold 2.2 billion gallons of water.
Duke spokeswoman Paige Sheehan couldn’t say Friday how much water will be released from pond for the pipe repair.
“While I don’t have specifics on how much the water will be lowered, it will take place fairly slowly, not more than 1 foot a week, and will comply with permit limits,” she said by email.
Metals found in coal ash can be toxic in high doses. Marshall’s discharge permit sets limits for concentrations of copper, iron and selenium, all found in ash. But Duke is required to only to test water for metals including arsenic, mercury, nickel and zinc.
State officials say pollutant limits aren’t included in discharge permits unless previous data showed a “reasonable potential” those contaminants would hurt water quality.
The metals that don’t have limits in the Marshall permit haven’t crossed that threshold, the officials say.
The water to be released in the pipe repair project “is the same water that they discharge anyway,” said Sergei Chernikov, an engineer in the discharge permitting staff of the state Division of Water Resources.
Duke said monitoring of Lake Norman and Mountain Island Lake near Charlotte’s water intakes consistently measure arsenic, chromium, selenium and other elements at the lowest levels lab instruments can detect.
In March, the Department of Environment and Natural Resources cited Duke for improperly releasing 61 million gallons of water from two ash ponds at its retired Cape Fear power plant in Chatham County. Duke responded that the releases were allowed under its discharge permit and that it notified DENR in advance.
Other ash ponds
The Marshall repair raises questions about how Duke will drain 31 more ash ponds statewide by 2029, as legislators ordered last summer.
Ash may stay in place at some ponds, with protective caps over them, but all will have to be emptied of water that had been mixed with ash.
Coal Ash Management Commission member Rajaram Janardhanam, a civil engineering professor at UNC Charlotte, raised the issue at the commission’s first meeting in November.
How, Janardhanam asked Duke official Richard Baker, “would we drain (ponds) without hurting the environment?”
Baker responded that the company will work with DENR and others to do “all the appropriate calculations to ensure that we don’t impact the water body as we do start releasing that water.”
Sheehan said Duke expects to use filtration systems, among other measures, to stay within permit limits while draining the ponds. Discharge permit modifications reflecting those changes are expected next year for Marshall and other Duke plants.
Ash settles to the bottom of ponds, where contaminants are concentrated. Chernikov, the state engineer, said Duke might have to remove contaminants from water that’s trapped between ash pores before discharging it.