NC0003468_Other Agency Documents_20180618

fort, DUKE Dan River Combined Cycle
N., ENERGY® Duke Energy Carolinas
864 South Edgewood Road
Eden, NC 27288
June 18,2018
Mr.Jeffrey 0.Poupart
North Carolina Department of Environmental Quality RECEIVED/DENR/DWR
1617 Mail Service Center
Raleigh,NC 27699-1617 JUN 2 2 2018
Subject: Duke Energy Carolinas,LLC Water Resources
Dan River Combined Cycle Station Permitting Section
NPDES Permit NC0003468
Rockingham County
Dear Mr.Poupart:
Duke Energy Carolinas, LLC (Duke Energy) will soon commence removal of interstitial water from the ash basins
at the Dan River Combined Cycle Station(Dan River). In order to meet the NPDES permit requirements associated
with discharge of interstitial water from these basins, the existing wastewater treatment process will be
supplemented to include temporary, mobile treatment units. These units will serve to provide additional treatment
of the interstitial water remaining in the basins. The purpose of this letter is to provide courtesy notification of the
planned temporary changes and a simplified schematic of this additional treatment process for your information and
files. Duke Energy plans to begin release of this water on 7/2/2018. This letter serves as both our submittal of plans
describing the treatment technologies but also our required notification at least one week prior to commencement of
the discharge.
As you are aware, and described in Dan River's current NPDES Permit NC0003468, the existing wastewater
treatment system for waste flows from Dan River's former coal generating facility consist of sedimentation and
neutralization process provided by the two site ash ponds. That wastewater treatment system will be temporarily
supplemented to include the following treatment:
• Reaction/feed frac tank for chemical addition and equalization(oxidation&pH adjustment)
• Ultrafiltration membrane container
• Effluent storage tank
The treated effluent from the expanded wastewater treatment system will be routed to Dan River through outfall
002. The small flow that has been reported on DMR's since 11/12/2016 (approximately 0.00025 MGD) will be
commingled with this flow and released through outfall 002. Any low volume wastes (such as reject streams or
backwash processes) resulting from this additional treatment will be recycled to the ash pond. Potential industrial
stormwater from the area containing this equipment will be routed to the City of Eden consistent with Industrial
User Permit#1013. Sludge will be collected and properly disposed of in onsite landfill. The vendor selected to
provide the temporary units will be providing additional operational support staff for the treatment equipment.
In accordance with NCGS 143-215(a6), and because all activity is authorized under the facility's existing NPDES
permit, no authorization to construct is required to be issued before the temporary systems can be utilized, and no
NPDES permit modification will be necessary.
Duke Energy remains committed to safely closing ash basins at all of our North Carolina sites. We look forward to
continuing to work with your agency in a collaborative manner to facilitate this work. If there are any questions,
please feel free to contact Joyce Dishmon, EHS CCP Permitting and Compliance, at Joyce.Dishmon@duke-
energy.com or 336-623-0238.

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
7 Sinerely, •
Michael Lanning
GM II—Regulated Stations
Dan River Combined Cycle
Power Generating Carolinas East
Attachment
Cc: Julie Gryzb—NC DWR 1617 Mail Service Center Raleigh,NC 27699-1617
Sherri Knight—WSRO,450 West Hanes Mill Road,Winston-Salem,NC 27105
Richard Baker w/attachment-via email
Shannon Langley w/attachment—via email
Dana Newcomb,ORC
Joyce Dishmon/Filenet w/attachment

Duke Energy Carolinas, LLC NPDES Permit NC0003468
Dan River Combined Cycle Station Interstitial Water Treatment Flow Chart
Mobile
Primary Interstitial Water
Primary Reaction/Feed
BasinFrac Tank
Low vo'ume wastes
dt�a�W ater
SeCondar `nter5 Ultrafiltration
v
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ag
rD
Basin Mobile
Effluent °
Bag Filter <
Storage
e,
rD
(1)
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Outfall 002 to Dan River