NC0038377_EMC SOC WQS18-005_20191024

t7DUKE James Wells
ENERGY. Vice President
Environmental,Health and Safety
Programs&Environmental Sciences
526 South Church Street
Charlotte, NC 28202
[phone]
October 24, 2019
Via Overnight Mail
RECEIVED
Linda Culpepper
Director of Water Resources NOV 04 2019
North Carolina Department of Environmental Quality
1617 Mail Service Center NCDEQIDWRINPDES
Raleigh, NC 27699-1617
Bob Sledge
Division of Water Resources
North Carolina Department of Environmental Quality
1617 Mail Service Center
Raleigh, NC 27699-16 17
Subject: Report Under Special Order by Consent — EMC SOC WQ S 18-005
Duke Energy Progress, LLC — Mayo Steam Electric Plant
NPDES Permit NC0038377
Quarterly Progress Report for 3rd Quarter 2019
Dear Ms. Culpepper and Mr. 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. S 18-005 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.

Ms. Culpepper and Mr. Sledge
October 24, 2019
Page 2
Please direct any questions concerning the Mayo Steam Electric Plant NPDES Permit
NC0038377 SOC No. S 18-005 to Lori Tollie at [phone].
Sincerely,
James ells
Vice President, Environment, Health & Safety
Programs and Environmental Sciences
Duke Energy
CC: Richard Baker, Duke Energy,
Lori Tollie, Duke Energy
Leanne Wilson, Duke Energy
George Hamrick, Duke Energy
Paul Draovitch, Duke Energy
Matt Hanchey, Duke Energy
Randy Hart, Duke Energy

NPDES PERMIT NC0038377
SPECIAL ORDER BY CONSENT EMC SOC 518-005
QUARTERLY PROGRESS REPORT
MAYO STEAM STATION
OCTOBER 24, 2019

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Background and Summary
On August 15, 2018, Duke Energy Carolinas, LLC(DEC)and the North Carolina Environmental Management
Commission entered into a Special Order by Consent — EMC SOC 518-005 (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 140 acres with a current ash inventory of
approximately 6.6 million tons of ash as of July 2019.
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 2019. Mayo ceased wet
sluicing of bottom ash in May 2013 when the dry bottom ash system became operational. The Ash Basin
was removed from service in June 2019 upon the completion of the diversion of all other wastewater flow
to a newly 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 OEM water
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 20, 2019, as required by the NPDES Permit, and written notification for
the initiation of decanting per the SOC on June 27, 2019. Through September 30, 2019, approximately 7
feet have been decanted from an initial depth of 46 feet.
Due to the sloughing event that occurred at Mayo on September 13, 2019, decanting ceased and likely
will not resume until 2020. This will result in a loss of the ability to decant the basin by numerous feet
during this timeframe. This event, along with limits on the decanting rate, could potentially affect the
Station's ability to meet its required completion date.
Mayo: 1