NC0003468_Correspondence_20220720

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
RICHARD E. ROGERS, JR.
Director
NORTH CAROLINA
Environmental Quality
July 26, 2022
Ms. Jessica Bednarcik, Senior Vice President
Environmental, Health and Safety
Duke Energy Carolinas, LLC
Mail Code EC13K
P.O. Box 1006
Charlotte, North Carolina 28201-1006
Dear Ms. Bednarcik:
Subject: Draft NPDES Permit
Permit NC0003468
Dan River Combined Cycle
Station
Rockingham County
Facility Class I
Enclosed with this letter is a copy of the Draft Permit for your facility. Please review the draft very
carefully to ensure thorough understanding of the conditions and requirements it contains.
The Draft Permit contains the following significant changes from your current permit:
• Once through cooling water and treated domestic wastewater have been removed from the
list of authorized discharges.
• The monitoring requirements for Mercury have been removed from the permit based on the
results of the Reasonable Potential Analysis.
• The monitoring requirements for Iron have been removed from the permit based on the
elimination of the state standards for Iron.
• The footnote associated with temperature requirement of once -through cooling system has
been removed from the permit due to the conversion to the closed -cycle cooling system.
• The monitoring and limits for pH have been removed from internal Outfall 001A to be
consistent with the requirements of 40 CFR 423.
• The 316(a) variance has been removed from the permit and substituted with the Thermal
Mixing Zone based on the new modeling information and due to the conversion to the closed -
cycle cooling system.
• The downstream sampling site was relocated closer to the discharge from 2 miles to 85 ft.
based on the results of the thermal model.
• The effluent temperature limit has been increased to 37.2°C from 35°C and was changed from
Monthly Average to Daily Maximum based on the results of the thermal model. This change
will make the limit more stringent because it will not allow any excursions above 37.2°C.
1:tE
NORTH CAROLINA
Department of Environmental Duali�
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 11611 Mail Service Center I Raleigh, North Carolina 27699-1611
919.707.9000

• The following permit conditions have been removed due to the elimination of the discharges
associated with operations of the former coal ash ponds:
1. Effluent pages for Outfall 002.
2. Effluent pages for 3 seeps.
3. Chronic toxicity conditions for Outfall 002.
4. Special Condition for Structural Integrity of the Ash Pond Dam.
5. Special Condition for Instream Monitoring.
6. Special Condition for Applicable State Law — Senate Bill 729.
7. Special Condition for Discharge from Seepage.
8. Special Condition for Fish Tissue Monitoring Near Ash Pond Discharge (Outfall 002).
Please provide any comments you have regarding the draft permit to this office by August
29, 2022. At this time, the Division is also publishing a notice in the newspapers of general
circulation in Rockingham 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.
The NPDES Standard Conditions (Parts II, III, and IV) are not included with this draft. They can
be found at the following link if you would like to review them in conjunction with this draft permit.
https: / /bit.ly/2BZ4xxx
If you have any questions about the NPDES permit process, please contact me at the following e-
mail address: [e-mail], or telephone number: 919-707-3606.
Sincerely,
Sergei Chernikov, Ph.D.
Environmental Engineer III
Complex NPDES Permitting Unit
cc: NPDES Files
EPA Region IV (e-copy)
Winston-Salem Regional Office / Surface Water Protection (e-copy)
Aquatic Toxicology Unit (e-copy)
TACU (e-copy)
cD_EQ
-4
NORTH CAROLINA
Department of Environmental Deellry
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 11611 Mail Service Center I Raleigh, North Carolina 27699-1611
919.707.9000