NC0004987_SOC WQ S17-009_20200423

4, DUKE James Wells
Vice President
ENERGY® Environmental,Health and Safety
Programs&Environmental Sciences
526 South Church Street
Charlotte,NC 28202
[phone]
April 23, 2020 RECEIVED
Via Overnight Mail MAY 0 1 2020
Corey Basinger NCDEQIDWRINPDES
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
Bob Sledge
North Carolina Department of Environmental Quality
Water Quality Permitting Program
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 Carolinas, LLC—Marshall Steam Station
NPDES Permit NC0004987
Quarterly Progress Report for 1st Quarter 2020
Dear Messrs. Basinger and Sledge:
On behalf of Duke Energy Carolinas, LLC (DEC), I am submitting to you the Marshall Steam
Station quarterly progress report that summarizes the work and activities undertaken with respect
to closure of coal ash surface impoundment as required by the Marshall Steam Station NPDES
Permit NC0004987 Special Order by Consent (SOC), SOC No. S 17-009 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 23, 2020
Page 2
Please direct any questions concerning the Marshall Steam Station NPDES Permit NC0004987
SOC No. S17-009 to Robert Wylie at [phone].
Sinc y,
James ells
Vice P sident, Environment, Health & Safety-
Programs and Environmental Sciences
Duke Energy
Attachment:
Marshall Steam Station Quarterly Progress Report
cc: Richard Baker, Duke Energy
Scott La Sala, Duke Energy
George Hamrick, Duke Energy
Paul Draovitch, Duke Energy
Matt Hanchey, Duke Energy
Randy Hart, Duke Energy

NPDES PERMIT NC0004987
SPECIAL ORDER BY CONSENT EMC SOC WQ S17-009
QUARTERLY PROGRESS REPORT
MARSHALL STEAM STATION
APRIL 23, 2020

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 WQ 517-009 (SOC) applicable to the
Marshall Steam Station (Marshall).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 Marshall. 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 Marshall Steam Station is located in Sherrills Ford, NC (Catawba County), on the west bank of Lake
Norman.Lake Norman is a man-made reservoir created by the impoundment of the Catawba River.Marshall
is a four-unit, 2090 megawatts, coal-fired generating facility. The Marshall Station began commercial
operation in 1965 and 1966 with Units 1 and 2, respectively. Unit 3 began operation in 1969
and Unit 4 in 1970.
Marshall's ash basin has a single impoundment, which is regulated by the North Carolina Department of
Environmental Quality. The ash basin covers approximately 394 acres with a current ash inventory of
approximately 16.8 million tons of ash as of February 2020.
Marshall 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:
• Active Ash Basin (CATAW-054)
The Ash Basin received CCR products from its initial operation in 1965 until 2018, when wet sluicing of
bottom ash ceased. In early 2005, Marshall replaced its fly ash wet sluicing operation with a dry ash
handling system and began placing dry fly ash into a landfill. Marshall ceased wet sluicing of bottom ash
in September 2018,when the dry bottom ash system became operational. The Ash Basin was removed
from service in March 2019 upon the completion of dry bottom ash handling and 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 Marshall. Purchase Orders were awarded in January 2019 for the pad
and electrical infrastructure installations,as well as a Purchase Order for the water treatment supplier. Duke
Energy commenced construction of the infrastructure and system in April 2019, which was completed and
began operation in September 2019.The decanting process by gravity flow began on July 16,2019,when the
stop logs were removed from the final ash basin discharge structure. Duke Energy provided advance notice
for the projected start date of decanting and installation of a wastewater treatment system to NCDEQ on
Marshall: 2

June 27, 2019, as required by the NPDES Permit. Mechanical Decanting of the Ash Basins began on
September 13, 2019. Written notification for the initiation of decanting per the SOC was submitted to
NCDEQ on September 30, 2019. Decanting of the Ash basin continues. As of March 29,2020,the elevation
was approximately 779.3 feet. The elevation of the water level since mechanical decanting began is
currently about 7 feet lower with approximately 7 feet remaining to finish decanting and enter into
dewatering.
Marshall: 3
1