NC0005088_Update Application on File_20200521

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DUKE Rogers Energy Complex
573 Duke Power Road
ENERGY® Mooresboro. NC 28114
828 657 2000
May 21, 2020
Sergei Chernikov, PhD.
North Carolina Division of Water Resources C 'VED
1617 Mail Service Center
Raleigh, NC 27699-1617 MAY 2 9 1010
Subject: Duke Energy Carolinas, LLC �ppEQ�pWRINpDES
Rogers Energy Complex - Cliffside Steam Station
Update to NPDES Application on File
NPDES Permit #NC0005088
Ash Basin and Storage Area Excavation Activities
Dear Dr. Chernikov:
This letter is being sent to you in order to keep you informed of the activities associated
with the ash excavation projects as they relate to the NPDES permit and to update
Duke Energy's (Duke) NPDES permit application record in your files.
As discussed on May 14, 2020 with Mr. Shannon Langley, the relatively new on-site
waste water treatment system (WWTS) (NPDES Outfall 005) has performed very well, it
is Duke's conclusion that the optimal approach is to send all the waste water that is
generated during ash location closure and excavation activities to this WWTS for
enhanced treatment. The site WWTS is a permanent physical/chemical treatment
system that consists of two 1 million-gallon flow equalization tanks, reaction tanks for
pH neutralization and coagulation. Flocculation is then provided by high-rate clarifiers.
If further treatment is needed, the option is available to send the treated water through
polishing filters. This system went into operation in April 2019. This WWTS has the
capacity to process on the average 13 MGD. Its current daily average flow over the
past year has been 5.5 MGD.
The following provides more details of the ash removal and remediation activities. The
attachment outlines where these activities are to occur.
1. Ash Basin — Duke has started to dewater the Ash Basin. On April 30, 2020, the
discharge from Outfall 002 was valved shut, and on May 5, 2020 Duke began pumping
this water to the new WWTS. Notification was made to DEQ on April 21, 2020 in
advance of this change in accordance with the NPDES permit. Outfall 002 is going to
be evaluated with respect to the need to discharge in the future. The flow from this
activity to the site WWTS is estimated to be a long-term average of 1 MGD.
2. Ash Storage Area - The excavation of the Ash Storage Area is scheduled to begin
in October 2020. The storm water that comes into contact with ash in this area will be

Sergei Chernikov, PhD.
NC Division of Water Resources
May 21, 2020
collected and pumped to the Ash Basin, where it will be pumped to the site WWTS. The flow
from this operation to the site WWTS will be part of the 1 MGD flow noted for the Ash Basin
above. This project is planned to be completed by the end of 2021.
3. Unit 5 Inactive Ash Basin -The Unit 5 Inactive Ash Basin is scheduled to begin ash
excavation in April 2021. A lined basin will be constructed to collect rain water that comes into
contact with ash. The removal process of this ash will be a phased approach such that the
entire IAB does not all drain into the lined basin. The water collected in the lined basin will be
pumped to the site WWTS in a metered approach as allowed by the WWTS treatment capacity.
It is estimated that the long-term average flow from this operation will be approximately 0.25
MGD.
4. Corrective Action Program Remediation Wells - Site remediation groundwater wells are
being installed. These wells will initially start as a pilot in April 2021 and then go into full
operation in June 2021. The long-term average flow to the WWTS from the well operation is
anticipated to be approximately 0.24 MGD.
With the start of the above activities, it is estimated that the long-term daily average flows from
Outfall 005 will range over the next several years from approximately 7 to 8 MGD. Concurrent
with this, the discharge from outfall 002 (ash basin) will effectively cease, unless there is
another need identified for it to be utilized. There should not be any significant changes in the
final discharge concentrations from Outfall 005. The receiving waters should also not see
significant changes in overall flows. The net effect of the additions to Outfall 005 and the likely
ceasing of flows from Outfall 002 should result in a minor overall difference.
Please advise if any additional information is needed. If you have questions, please contact
Robert Wylie at [phone] or [e-mail].
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 fine and imprisonment for knowing violations.
Sincerely,
1)airc:7
David P. Barnhardt
General Manager II, Rogers Energy Complex
Fossil/Hydro Operations - Carolinas Coal Generation
Attachment: Figure of Ash Excavation Locations
USPS 7020 0090 0001 7517 0054

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