NC0038377_Report_20200724

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(� DUKE James Wells
'e ENERGY Vice President
Environmental,Health and Safety
Programs&Environmental Sciences
526 South Church Street
Charlotte,NC 28202
[phone]
July 24, 2020
Via Overnight Mail
S. Daniel Smith
Director of Water ResourcesRECEIVED
North Carolina Department of Environmental Quality JUL 2 7 7020
1617 Mail Service Center NCDEQ/DWR/NPDES
Raleigh,NC 27699-1617
Bob Sledge
Division of Water Resources
North Carolina Department of Environmental Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Report Under Special Order byConsent—EMC SOC WQ S 18-005
p p
Duke Energy Progress, LLC—Mayo Steam Electric Plant
NPDES Permit NC0038377
Quarterly Progress Report for 2nd Quarter 2020
Dear Messrs. Smith and Sledge:
On behalf of Duke Energy Progress, LLC (DEP), I am submitting to you the Mayo Steam Electric
Plant Progress Report summarizing the work and activities undertaken with respect to closure of
coal ash surface impoundment as required by the Mayo Steam Electric Plant NPDES Permit
NC0038377 Special Order by Consent(SOC), SOC No. S18-005 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. Smith and Sledge
July 24, 2020
Page 2
Please direct any questions concerning the Mayo Steam Electric Plant NPDES Permit
NC0038377 SOC No. S18-005 to Lori Tollie at [phone].
Sincerely,
C- d,/yvViii
James Wells
Vice President, Environment, Health & Safety
Programs and Environmental Sciences
Duke Energy
Attachment
Mayo Steam Electric Plant Quarterly Progress Report
CC: Richard Baker, Duke Energy
Lori Tollie, Duke Energy
Leanne Wilson, Duke Energy
Paul Draovitch, Duke Energy
Matt Hanchey, Duke Energy
Shannon Langley, Duke Energy
Randy Hart, Duke Energy

NPDES PERMIT NC0038377
SPECIAL ORDER BY CONSENT EMC SOC S18-005
QUARTERLY PROGRESS REPORT
MAYO STEAM STATION
J U LY 24, 2020

Background and Summary
On August 15, 2018, Duke Energy Progress, LLC (DEP) and the North Carolina Environmental Management
Commission entered into a Special Order by Consent - EMC SOC S18-005 (SOC) applicable to the Mayo
Steam Station (Mayo).This report is submitted in accordance with Section 2.c.2) of the SOC. In compliance
with Section 2.c.2), this report summarizes the work and activities undertaken with respect to decanting
work and closure of coal ash surface impoundments at Mayo. 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.
The Mayo Steam Station is located in Roxboro,NC(Person County),on Mayo Lake. Mayo Lake is a man-made
reservoir constructed by the impoundment of the Mayo Creek. The Mayo Steam Station is a single unit,
727-megawatt, coal-fired generating facility,which began commercial operation in 1983. Mayo's ash basin
has a single impoundment,which is regulated by the North Carolina Department of Environmental Quality.
The ash basin covers approximately 153 acres with a current ash inventory of approximately 6.6 million
tons of ash as of February 2020. Procurement activities for the ash basin closure work began in June 2020.
Mayo historically wet sluiced coal combustion residual (CCR) products into a surface impoundment
located on the property. This surface impoundment is known as the Ash Basin,which is impounded by
the following dam:
• Ash Basin(PERSO-035)
The Ash Basin received CCR products from its initial operation in 1983 until 2013. Mayo ceased wet
sluicing of bottom ash in May 2013 when the dry bottom ash system became operational. The Ash Basin
stopped receiving process flows in June 2019 upon the diversion of all wastewater flow to a newly
constructed lined retention basin.
Decanting Status
In compliance with this SOC, Duke Energy initiated design and procurement efforts in Q3 2018 for a
decanting water treatment system at Mayo. Purchase Orders were awarded in January 2019 for the WWTS
pad and electrical infrastructure installations, as well as a Purchase Order for the wastewater treatment
supplier. Duke Energy commenced construction of the infrastructure and system in March 2019 and
completed it in May 2019. Duke Energy provided advanced notice for the projected start date of decanting
to NCDEQ on June 27, 2019, as required by the NPDES Permit, and written notification for the initiation of
decanting per the SOC on June 27, 2019.
Mayo: 2

Decanting was stopped at Mayo following a sloughing event on September 14,2019. This sloughing
event, along with limits on the decanting rate, could potentially affect the Station's ability to meet
its required completion date. A plan was implemented in April 2020 to increase the pumping capacity
of the decanting system in an effort to recover from the downtime following the slough. Decanting was
restarted on May 11, 2020 and is expected to be complete,during the 4th Quarter of 2020, based on the
revised decanting plan.
Mayo: 3