NC0004979_Correspondence_20210728 (6)

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
S. DANIEL SMITH
Director
NORTH CAROLINA
Environmental Quality
July 26, 2021
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: Final NPDES Major
Modification
Permit NC0004979
Allen Steam Station
Gaston County
Facility Class I
The Division of Water Resources is forwarding herewith the Final Major Modification for
Roxboro Steam Electric Generating Plant. This modification is issued pursuant to the
requirements of North Carolina General Statute 143-215.1 and the Memorandum of Agreement
between North Carolina and the U.S. Environmental Protection Agency dated October 15, 2007
(or as subsequently amended).
The Final Major Modification contains the following significant changes from your Draft
Permit:
• Early retirement exemption has been postponed and earlier FGD limits have been re-
instated until Duke submits the Notice of Planned Participation (Internal Outfall 005).
• The ELG re -opener clause was added to the permit (Internal Outfall 005).
The Final Major Modification maintains the following significant changes contained
in the Draft 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.
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 11617 Mali Service Center I Raleigh, North Carolina 27699-1617
919,707.9000

• 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 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.
If any parts, measurement frequencies, or sampling requirements contained in this permit are
unacceptable to you, you have the right to an adjudicatory hearing upon written request within thirty
(30) days following receipt of this letter. This request must be in the form of a written petition,
conforming to Chapter 150B of the North Carolina General Statutes, and filed with the office of
Administrative Hearings, 6714 Mail Service Center, Raleigh, North Carolina 27699-6714. Unless such
a demand is made, this permit shall be final and binding.
Please note that this permit is not transferable except after notice to the Division. The Division may
require modification or revocation and reissuance of the permit. This permit does not affect the legal
requirements to obtain other permits which may be required by the Division of Water Resources or
any other Federal, State, or Local governmental regulations.
If you have any questions or need additional information, please contact Sergei Chernikov, telephone
number [phone] or email: [e-mail].
cc: Central Files
NPDES Files
Mooresville Regional Office/Water Quality
WSS/Aquatic Toxicology Unit (e-copy)
EPA Region IV (e-copy)
Sincerely,
>f- S. Daniel Smith, Director
Division of Water Resources
,D_EQV)
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