NC0001422_00_CAP Update 2020 Cover Ltr Signed_20200814

('DUKE
ENERGY.
August 3, 2020
Ms. Sheila Holman
Assistant Secretary for Environment
North Carolina Department of Environmental Quality
1611 Mail Service Center
Raleigh, North Carolina 27699-1611
Paul Draovitch
Senior Vice President
ENS, Operations Support 8 CCP
526 S. Church Street
Mail Code.- EC3XP
Charlotte, NC 28202
[phone]
Subject: Updated Corrective Action Plan Report for the L.V. Sutton Energy Complex, Wilmington,
New Hanover County, North Carolina, NPDES Permit No. NC0001422
Dear Ms. Holman:
Duke Energy submits the enclosed updated Corrective Action Plan (CAP) for the L.V. Sutton Energy
Complex. As specified in the North Carolina Department of Environmental Quality (NCDEQ) letter dated
February 26, 2020, this updated CAP incorporates multi -media data collected in and around the 1971 &
1984 ash basins, former process area (FPA), former ash disposal area (FADA) and former coal pile area
(FCPA) inclusive through Quarter 1 of 2020.
The enclosed updated CAP recommends the following corrective actions at Sutton:
• Continued operation of the present nine well groundwater extraction and treatment system;
• Monitored natural attenuation (MNA) along with a restricted groundwater use designation (RS
designation) for an area that includes a portion of the FCPA and a part of the cooling pond; and
• Implementation of a post -excavation Effectiveness Monitoring Plan (EMP) with a five-year
review period to monitor the effectiveness of corrective action.
MNA is proposed for use in the areas with limited constituent of interest (C01) migration beyond the ash
basin compliance boundary. The use of MNA is based on generally stable or decreasing COI
concentration trends in groundwater samples collected at the site. A groundwater restricted use
designation (RS designation) can be used to prevent installation of water supply wells in a portion of
cooling pond and a portion of the FCPA.
As detailed in the enclosed updated CAP, source removal by excavation was recently completed,
including removal of coal from the FCPA by 2015, complete excavation of the 1971 and 1984 ash basins
in 2019 and excavation of the FPA and FADA in 2020. The COI concentrations downgradient of the
source areas vary, but are generally stable or decreasing based on groundwater data collected to date.
Evidence of conditions favorable for natural attenuation are indicated based on recent post -excavation
data. The reduction in hydraulic head and mass contribution from the former source areas is anticipated
to be sufficient for natural attenuation processes to reduce COI concentrations beyond the compliance
boundary. Post -excavation effectiveness monitoring is proposed to confirm the preliminary stable or
decreasing C01 concentration trends currently indicated.

The enclosed updated CAP report also concludes there was no evidence of unacceptable risks to humans
and wildlife at Sutton attributed to coal or coal ash constituent migration in groundwater from the ash
basins, FADA, FPA and FCPA. This conclusion is further supported by decades of water quality and
biological assessments conducted by Duke Energy as part of NPDES and other site monitoring programs.
If you have any questions on the enclosed information, please contact Ed Sullivan at 980-373-3719.
incerel ,
Pa Draovitch
Senior Vice President
EFTS, Operations Support and CCP
Enclosure: Updated Corrective Action Plan, L.V. Sutton Energy Complex
cc: Rick Bolich — NCDEQ Central Office
Morelia Sanchez -King — NCDEQ Wilmington Regional Office
Ed Sullivan — Duke Energy
Kathy Webb — SynTerra Corp.
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