NC0000396_NOV-2022-LV-0195 Response_20220329

/'DUKE
ENERGY®
PROGRESS
March 29, 2022
ELECTRONIC SUBMITTAL
Mr. G. Landon Davidson, P.G., Regional Supervisor
Water Quality Regional Operations Section
Asheville Regional Office
Division of Water Resources, NCDEQ
E-mail Address: [e-mail]
Subject: Response to NOV-2022-LV-0195
NPDES Permit NC0000396
Duke Energy Progress, LLC
Asheville Combined Cycle Plant
Dear Mr. Davidson:
Keith Douthit
Plant General Manager
Asheville Combined Cycle Station
Duke Energy Progress
ASVL PLT146 Duke Energy Lane
Arden, NC 28704
o: 828-650.0620
t.. 828.650-0701
keith.douthit duke-energy-com
Duke Energy Progress, LLC (Duke Energy) appreciates the opportunity to provide this response to the
subject Notice of Violation (NOV). Duke Energy continues to progress with activities at the Asheville
Plant in efforts to safely close the station's ash basin and landfill. The coal-fired units at the site have
been retired since early 2020 and replaced by natural gas -fired combined cycle generation units. The
combined cycle internal outfalls OO1A and OO1C, were added to the NPDES permit in 2019 and
combine discharges with outfall 001 - 1964 Ash basin. The flows from the 1964 ash basin have been
significantly reduced since shutdown of the coal units.
Prior to January 25, 2022, outfall 001 had not experienced any pH exceedances. Duke Energy has
conducted a thorough evaluation as to the causes of the pH exceedance noted in the subject Notice of
Violation. A clear cause has not been identified. There were no upsets or alarms leading up to the
event. The discharge from the internal outfalls consists primarily of cooling tower blowdown. The
water chemistry in the cooling tower and HRSG (heat recovery steam generator) is continuously
monitored and operated in accordance with the manufacturer recommendations. Blowdown is based
on ORP and conductivity and is approximately 3% discharge of the circulating water system.
Blowdown is treated with sodium bisulfite for de -chlorination prior to discharge. A by-product of the
warmer discharge to the secondary settling basin has been the development of algae bloom even in
winter months, thought to be associated with phosphorus and ammonia residual in the blowdown
stream. Retention time in the settling basin can increase when the ash basin pumps are not run, as was
the case for 4 days prior to the sample in question. Water treatment science has documented that algae
consumes CO2 and results in increased pH.
Additional assessment is ongoing, and Duke Energy has undertaken several steps to identify and
prevent recurrence. A list of short- and long-term actions taken includes:

Response to NOV-2022-LV-0195
March 28, 2022
page 2 of 2
1. Continue regular operational pH monitoring of the combined cycle wastewater collection
sump.
2. Regular removal of settling pond algae growth until a long-term solution is implemented.
3. Organized a project management and engineering team, including third party engineering to:
a. Evaluate and design a pH monitoring and treatment system for the combined cycle
wastewater sump.
b. Evaluate and design the configuration of the secondary settling basin to accommodate
ash basin closure and lower flows.
Duke Energy believes these actions will minimize the likelihood of a future exceedances and identify
design improvement that will work well in our future configuration once closure activities are
completed.
If you have any questions, please contact Ms. Teresa Williams [phone], or Mr. Don Safrit
[phone].
I certify, under penalty of law, that this document and all attachments were prepared under my
direction or supervision in accordance with a system designed to assure that qualified personnel
properly gather and evaluate the information submitted. Based on my inquiry of the person or persons
who manage the system, or those persons directly responsible for gathering the information, the
information submitted is, to the best of my knowledge and belief true, accurate, and complete. I am
aware that there are significant penalties for submitting false information, including the possibility of
fines and imprisonment for knowing violations.
Sincerely,
Keith Douthit
Asheville Combined Cycle Station Manager
cc: Mr. Tim Heim, P.E., Environmental Engineer
Water Quality Regional Operations Section
Asheville Regional Office
Division of Water Resources, NCDEQ
E-mail Address: [e-mail]