NC0004979_Other Correspondence_20190424

(� DUKE
ENERGY
James Wells
Vice President
Environmental, Health and Safety
Programs & Environmental Sciences
526 South Church Street
Mail Code EC13K
Charlotte, NC 28202
[phone]
April 24, 2019 NP R
Via Overnight Mail WQIHO4;
-GIONAL OFFICE
N100RUSVILIL.' RE
Corey Basinger
Mooresville Regional Office Regional Supervisor
North Carolina Department of Environmental Quality
Division of Water Resources
Water Resources - Water Quality Regional Operations
610 East Center Avenue, Suite 301
Mooresville, NC 28115
bon meage
North Carolina Department of Environmental Quality
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Division of Water Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Report Under Special Order by Consent — EMC SOC WQ S 17-009
Duke Energy Carolina, LLC — Allen Steam Station
NPDES Permit NC0004979
Quarterly Progress Report
Dear Messrs. Basinger and Sledge:
On behalf of Duke Energy Carolinas, LLC (DEC), I am submitting to you the Allen Steam Station
Progress Report summarizing the work and activities undertaken with respect to closure of coal
ash surface impoundments as required by the Allen Steam Station NPDES Permit NC0004979
Special Order by Consent (SOC), SOC No. S17-009 Section 2.c.2).
As required by the SOC, 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.

Messrs. Basinger and Sledge
April 24, 2019
Page 2
Please direct any questions concerning the Allen Steam Station NPDES Permit NC0004979 SOC
No. S 17-009 to Elizabeth Glenn at [phone].
Vice PUesident, Environment, Health & Safety -
Programs -and -Environmental- Sciences
Duke Energy
Attachment:
Allen Steam Station Quarterly Progress Report
CC: Richard Baker, Duke Energy
Elizabeth Glenn, Duke Energy
Randy Gantt, Duke Energy
George Hamrick, Duke Energy
Paul Draovitch, Duke Energy
Matt Hanchey, Duke Energy
Randy Hart, Duke Energy

Background and Summary
On April 18, 2018, Duke Energy Carolinas, LLC (DEC) and the North Carolina Environmental Management
Commission entered into a Special Order by Consent — EMC SOC S17-009 (SOC) applicable to the Allen
Steam Station (Allen). This report is submitted in accordance with Section 2c. of the SOC. In compliance
with Section 2.c., this report summarizes the work and activities undertaken with respect to decanting
work and closure of coal ash surface impoundments at Allen. The quarterly reports are due no later than
the last day of January, April, July, and October for the duration of the SOC, once the decanting process
has begun.
Allen Steam Station is located in Belmont, NC, along the west shore of Lake Wylie. Lake Wylie is a man-
made reservoir created by the impoundment of the Catawba River. Allen is a five -unit, 1140 megawatts,
coal-fired generating facility. The Allen Station began commercial operation in 1957 with Units 1 and 2.
Unit 3 began operation in 1959, Unit 4 in 1960, and Unit 5 in 1961. The ash basins at Allen cover
approximately 293 acres with a current ash inventory of approximately 19.3 million tons of ash as of
February 2019, which is inclusive of the Active Ash Basin, Retired Ash Basin, Retired Ash Basin Landfill,
and the Distribution of Residual Solids facilities.
Allen historicallywet sluiced coal combustion residual (CCR) products into two surface impo11 undments
located on the property. These surface impoundments are known as the Retired Ash Basin (also referred
to as the Inactive Ash Basin) and the Active Ash Basin, which are impounded by the followine dams:
Retired Ash Basin (GASTO-016)
Active Ash Basin (GASTO-061)
The Retired Ash Basin received CCR products from initial operation in 1957 until 1973, when it reached
capacity and was retired. Allen then commissioned the Active Ash Basin and began wet sluicing CCR
products into this new basin. In 2009, Allen replaced its fly ash wet sluicing operation with a dry ash
handling system and began placing dry fly ash into a landfill constructed over a portion of the Retired Ash
Basin (Permit No. 36-12). Allen ceased wet sluicing of bottom ash in February 2019 when the dry bottom
ash system became operational. The Active Ash Basin was removed from service in February 2019 upon
the completion of dry bottom ash handling and diversion of all other wastewater flow to a newly lined
retention basin.
Closure Plans
A number of potential closure options are being considered for Allen. Following a comprehensive
assessment, Duke Energy will submit its Closure Plan to NCDEQ for review and approval in accordance
with CAMA requirements.
Decanting Status
In compliance with this SOC, Duke Energy initiated design and procurement efforts in Q3 2018 for a
decanting water treatment system at Allen. Purchase Orders were awarded in January 2019 for the WWTS
pad and electrical infrastructure installations, as well as a Purchase Order for the OEM water treatment
supplier. Wastewater flows were removed from the basin on February 9, 2019. Duke Energy provided
advance notice for the projected start date of decanting to NCDEQ on January 24, 2019, as required by
the NPDES Permit, and written notification for the Initiation of Decanting per the SOC on February 14,
2019.
Allen: 1