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NC DENR Gives Duke Permission to Drain Marshall Ash Ponds

NC DENR Gives Duke Permission to Drain Marshall Ash Ponds

According to a press release from the State of North Carolina, the North Carolina Department of Environment and Natural Resources has given Duke permission to lower the level of waste in the ash ponds at the Marshall coal-fired power plant in Catawba County (on Lake Norman) in order to repair a pipe in the dam structure.

NC DENR Gives Duke Permission to Drain Marshall Ash Ponds

Marshall Steam Station Discharge - July 25, 2009

The press release indicates that the coal ash waste in the ash ponds will be drained into Lake Norman in order to lower the level enough to perform necessary repairs to a corrugated metal pipe associated with the dam structure that holds back the waste.  It was a corrugated metal pipe failure that caused the coal ash spill at the Duke's Dan River plant in February 2014.  

It is unclear from the press release if the pipe that will be repaired poses an imminent threat to the safety of the dam.  However, the coal ash waste pond at the Marshall Steam Station is approximately ten times larger than the ash ponds at the Dan River facility.

The press release indicates that the State is allowing the "lowering [of] pond levels for essential maintenance to a dam as long as the utility does not exceed permitted wastewater discharge limits during maintenance." However, unlike a typical NPDES permit, the permit for the Marshall ash pond does not contain any limits for flow or the concentrations Arsenic, Mercury, Nickel or Zinc.  

Marshall Steam Station coal ash dike

Marshall coal ash pond dike which is approximately 90 feet high.

Furthermore, it is worth noting that the Marshall ash ponds are permitted to discharge more than just coal ash waste.  The Marshall ash ponds are permitted to receive and discharge into Lake Norman "metal cleaning wastes, coal pile runoff, ash transport water, domestic wastewater, low volume wastes, and FGD wet scrubber wastewater."

The text of the NCDENR press release is included below:

Regulators authorize repairs to dam structure at Duke Energy coal ash impoundment

RALEIGH –State environmental regulators have given Duke Energy permission to lower the level of a coal ash storage pond to make repairs to a dam structure at the Marshall Steam Station in Catawba County.

The N.C. Department of Environment and Natural Resources on Thursday granted the utility authorization to lower the level of the ash impoundment only after state and Environmental Protection Agency officials consulted on Duke Energy’s request. The utility requested it be allowed to lower the level of the coal ash impoundment to make necessary repairs to a corrugated metal pipe that is part of the decant system that filters wastewater in the ash pond. The Division of Energy, Mineral and Land Resources has approved repairs to the pipe.

The EPA and state regulators determined the repairs are authorized under a provision of the utility’s National Pollutant Discharge Elimination System permit that allows lowering pond levels for essential maintenance to a dam as long as the utility does not exceed permitted wastewater discharge limits during maintenance.

DENR sent a letter Thursday to Duke Energy giving permission to proceed with the project but directed the utility to collect and test wastewater discharges during the maintenance project to ensure that the permitted effluent discharges are not exceeded. Duke Energy is allowed to discharge wastewater from the coal ash impoundment at Marshall Steam Station toLake Norman, which flows to the Catawba River.

“Though notification of activities or approval is not explicitly required by regulation, DWR (Division of Water Resources) may review other submitted dam repair projects to convey to Duke Energy a better understanding of our interpretation of essential maintenance activities,” Jeff Poupart, the state water quality permitting section chief, stated in the letter sent to Duke Energy Thursday.

Copies of the letters DENR sent to Duke Energy approving the lowering of the storage pond and repairs to the pipe can be found on DENR’s coal ash website under the heading “Correspondence with Duke Energy” at:

The Marshall Steam Station is one of many Duke Energy coal ash facilities that will require state approvals to remove coal ash water to allow for repairs to dam structures or prepare for ash pond closure. Plans submitted by Duke Energy for those activities are being reviewed by the state divisions of Water Resources and Energy, Mineral and Land Resources.



Additional information about coal ash can be found at


News coverage about the repairs:



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