Duke Energy report outlines plans for Cliffside coal ash basin work

Duke Energy (NYSE: DUK) in a plan released Sept. 14 described how it intends, as part of an overall effort covering several plants, to clean up coal ash basins at the Cliffside Steam Station at the Rogers Energy Complex.

The cleanup plan covers the following ash basins: Units 1-4 Inactive Ash Basin (U1-4 Basin); Unit 5 Inactive Ash Basin (U5 Basin); and the Active Ash Basin, which includes two ash storage areas.

The purpose of this Ash Excavation Plan is to present the approach for excavating a portion of the ash from the U1-4 Basin and the U5 Basin to address Notices of Deficiency (NOD) issued by the North Carolina Department of Environment and Natural Resources (NC DENR). Subsequent updates to this Plan and/or the closure plans will address the remaining ash excavation and dam decommissioning of the U1-4 Basin, including water re-route, and closure of the U5 Basin.

Closure plans will be prepared and submitted to NC DENR in October 2016 for the U1-4 Basin, U5 Basin, and Active Ash Basin.

Duke Energy received a NOD from NC DENR on March 5, 2014, for the “high hazard potential” of the Cliffside Inactive Ash Basin 1-4 Main Dam due to the potential for significant environmental damage to the Broad River if the coal ash stored behind the dam were to be released. On Sept. 30, 2014, Duke Energy submitted the drawing package titled Inactive Ash Basin 1-4 Main Dam (CLEVE–047), High Hazard Potential, Storm Storage Excavation for Cliffside Steam Station, Cleveland and Rutherford Counties, North Carolina, September 2014, to NC DENR to provide a basis to resolve the issues identified in the NOD.

On Jan. 26, 2015, NC DENR issued a letter approving the drawing package. Based on these drawings, Duke Energy will excavate approximately 84,000 cubic yards (or approximately 101,000 tons) of ash and material from the U1-4 Basin to increase stormwater storage capacity, increase freeboard, and validate hydrology and hydraulics analysis to allow the retirement of decant riser/outfall pipe.

Based on the NOD, the basin’s location adjacent to the Broad River, and the structural integrity analysis performed under the Disposal of the Coal Combustion Residuals from Electric Utilities published by the U.S. Environmental Protection Agency on April 17, 2015, which indicates that there is an insufficient safety factor in the event of an earthquake, Duke Energy proposes to excavate the remainder of the ash and close the U1-4 Basin under North Carolina’s Coal Ash Management Act of 2014 (CAMA).

Duke Energy said it received another NOD from NC DENR on March 5, 2014, categorizing the Cliffside Inactive Ash Basin #5 Main Dam as a “high hazard” dam due to the potential for significant environmental damage to the Broad River if the coal ash stored behind the dam were to be released.

On November 14, 2014, Duke Energy submitted the drawing package titled Inactive Ash Basin #5 Main Dam (RUTHE–070), High Hazard Potential, Storm Storage Excavation for Cliffside Steam Station, Rutherford County, North Carolina, November 2014, to NC DENR to provide a basis to resolve the issues identified in the NOD.

On Feb. 2, 2015, NC DENR issued a letter approving the drawing package. Based on these drawings, Duke Energy will excavate approximately 400,000 cubic yards (or approximately 500,000 tons) of ash and material from the U5 Basin to increase stormwater storage capacity, increase freeboard, and validate hydrology and hydraulics analysis in order to retire the decant riser/outfall pipe.

It may become necessary for Duke Energy to modify the plan to address other legal requirements or factors that develop during ash excavation. Significant changes to this plan and final closure requirements and plans will be included in annual updates to the plan (by Dec. 31 of each subsequent year) and/or in the final closure plan that Duke Energy will submit to NC DENR by October 2016.

Cliffside is located at Mooresboro, North Carolina. It went into initial operation in 1939 with one coal-fired unit and was over time expanded to six coal-fired units. Units 1-4 were retired in 2011, and Unit 5 (commissioned in 1979) and Unit 6 (commissioned in 2012) continue to operate with a combined capacity of about 1,387 MW.

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.