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Home My WebLink AboutNC0004979_Correspondence_20210728 (3)ROY COOPER Governor DIONNE DELLI-GATTI Secretary S. DANIEL SMITH Director NORTH CAROLINA Environmental Quality April 6, 2021 Mr. Paul Draovitch, Senior Vice President Environmental, Health and Safety Duke Energy Progress, LLC Mail Code EC13K P.O. Box 1006 Charlotte, North Carolina 28201-1006 Subject: Draft NPDES Major Modification Permit NC0004979 Allen Steam Station Gaston County Facility Class I Dear Mr. Draovitch: The Division has received your request for a Major Modification of the subject permit. The request has been granted. Please review this Major Modification to ensure thorough understanding of the conditions and requirements it contains. The draft permit modification contains the following significant changes from your current permit: • The Bottom Ash Purge was added to the list of waste streams discharged to the Retention Basin. • The wastewater generated by the dewatering process and extracted groundwater were added to the to the Retention Basin to achieve timely closure of the Ash Pond and provide greater operational flexibility. • The flow limit for dewatering operations was increased from 1.0 MGD to 3.0 MGD to achieve timely closure of the Ash Pond. • The Upstream and Downstream monitoring locations were moved to monitor discharge from the Retention Basin. • The pH limits at the Internal Outfall 005 were removed to be consistent with the requirements in 40 CFR 423. • The Technology Based Effluent Limits for Total Arsenic, Total Mercury, Total Selenium, and Nitrate/nitrite as N were removed from the permit (Outfall 005 - �D_E NORTH CAROLINA Department of Environmental Quality North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617 919.707.9000 FGD wastewater) based on the latest update to the 40 CFR 423 and due to the early retirement of the Allen Steam Station. The Monthly Average and Daily Maximum numeric limits for these parameters were replaced with the Quarterly Average numeric limits for Total Arsenic, Total Selenium, and Total Mercury and a narrative limit that requires the facility to properly operate and maintain the existing FGD wastewater treatment equipment. • The Technology Based Effluent Limits for TSS and Oil and Grease were added to the permit (Outfall 005) based on the latest update to the 40 CFR 423. • The Annual Progress Report requirement was added to the permit (see Special Condition A. (19.) based on the latest update to the 40 CFR 423. • The RPA for Retention Basin was conducted by adding the highest reported concentration of the contaminants in the interstitial wastewater. The flow volume was also increased from 3.3 MGD to 3.5 MGD based on the latest estimates that incorporate flor from the CCR landfill. The limits for As were added as a result of this RPA (Outfall 006). • The RPA for Ash Basin dewatering phase was conducted by increasing flow from 1.0 MGD to 3.0 MGD. No new limits were added as a result of this RPA (Outfall 002). • The Special Condition that requires electronic submittal of all discharge monitoring reports was changed based on the latest update to the NPDES Electronic Reporting Rule (See Special Condition A. (26.)). • The Toxicity Test Instream Waste Concentrations for dewatering and Retention basin have been adjusted (Outfall 002 dewatering and Outfall 006) to account for the increased flow volume. Please provide any comments you have regarding the draft permit to this office by May 7, 2021. At this time, the Division is also publishing a notice in the newspapers of general circulation in Gaston County, inviting public comment on the Draft Major Modification. Following the 30-day comment period, we will review all pertinent comments received and take appropriate action on the permit modification. If you have any questions about the NPDES permit process, please contact me at the following e-mail address: sergei.chernikovva,ncdenr.gov, or telephone number: 919-707-3606. cc: Central Files NPDES Files EPA Region IV (e-copy) Mooresville Regional Office/Water Quality (e-copy) Mooresville Regional Office/PWS (e-copy) WSS/Aquatic Toxicology Unit (e-copy) G=D_E NORTH CAROIJNA Department al Environmental Quality Sincerely, Sergei Chernikov, Ph.D. Environmental Engineer III Industrial NPDES Permitting Unit North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617 919.707.9000