NC0000396_SP-2020-0001_20200317

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4., DUKE Paul Draovitch, P.E.
Senior Vice President
E N E RGY� Environmental, Health&Safety
and Operations Support
526 S. Church Street
Mail Code:EC3XF
Charlotte. NC 28202
March 16,2020
Mr. Bob Sledge
North Carolina Department of Environmental Quality
1617 Mail Service Center
Raleigh NC 27699-1617 RECEIVED
RE: Response to NOV-2020-SP-0001 MAR 1 7 2020
Duke Energy Progress, LLC.
Asheville Steam Electric Plant NCDEQ/DWR/NPDES
Special Order by Consent WQ S 17-010
Dear Mr. Sledge,
Duke Energy Progress, LLC (Duke Energy) appreciates the opportunity to provides this response
and supporting information to the subject Notice of Violation (NOV). Duke Energy continues to
progress with activities at the Asheville Steam Electric Plant in efforts to safely close the stations
ash basin. Additionally, as you are likely aware,the coal fired units at the site have recently
been retired and replaced by natural gas fired combined cycle generation units.
Duke Energy has conducted a thorough evaluation as to the causes of the sample results noted in
the subject Notice of Violation. As detailed in our submittal dated January 20, 2020 re-assessing
the applicable sample locations, Duke Energy,through the consultant SynTerra, has concluded
the cause of the elevated samples was not related to the ash basin at the site. A copy of that
report is attached for ease of reference. Rather, the noted temporarily reduced pH and increased
nickel and copper concentrations are thought to have been caused by influence of naturally
occurring pyrites affecting the pH and/or downgradient transport of groundwater associated with
the coal pile. The influence from these sources was new and thought to be associated with
daylighted groundwater entering the site's stormwater management drainage system. This
daylighting of groundwater is thought to have been enhanced after rock blasting that was
necessary for the construction of the combined cycle facility.
Additional assessment, including a dye tracer study, will be included in the revised
Comprehensive Site Assessment to be submitted to NCDEQ by previously agreed upon
timeframes. In the interim, Duke Energy has undertaken several intermediate steps ahead of the
proposed removal of the coal pile and remediation of the area. A list of immediate remedial
actions taken ahead of groundwater corrective action includes:
1. Installation of limestone rip rap in the stormwater drainage ditch in order to
increase the pH and cause metals precipitation.
2. Metal removal socks were installed in the stormwater drainage ditch to further
increase the removal of metals.
www.duke-energy.com

Mr. Bob Sledge
Response to NOV SP 2020-0001
March 16, 2020
Page 2 of 3
3. Polyacrylamide logs were added in the stormwater drainage ditch to improve the
removal of TSS in the downstream sediment basin.
4. Limestone gravel was added to one of the sediment basin's rock check dam
baffles for additional pH control.
5. Analyzing in process samples after the addition of BMP's to verify these
measures are having the desired effect.
Duke Energy believes it has adequately demonstrated that the exceedances noted in the subject
NOV were not related to the ash basin. Duke Energy has identified the causes and instituted
intermediate controls on these secondary activities to avoid future exceedances. Further
assessment and mitigation proposals related to these secondary source activities will be provided
to the NCDEQ in the timeframes previously agreed upon.
Because this exceedance was not the result of migration from the ash basin, Duke Energy
requests that no stipulated penalty be assessed under the SOC.
If you have any questions regarding this letter, please contact Mr. Robert Wylie at (704) 382-
4669 or [e-mail].
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 fines and imprisonment for knowing violations.
Since ely,
\ *AO 41111 "
P.ul Draovitch,
Senior Vice President
Attachment
cc: ARO DEQ WQ Supervisor
2090 U.S. 70 Highway
Swannanoa, NC 28778-8211
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Mr. Bob Sledge
Response to NOV SP 2020-0001
March 16, 2020
Page 3 of 3
Robert Wylie - via email
Shannon Langley—via email
Chris Hallman—via email
Antonio Price—Asheville Plant manager—via email
Teresa Williams—via email
Bryson Alison—via email