Mayo Low Volume Waste Ponds Response Letter_20190719

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Director
Paul Draovitch
Senior Vice President
Environmental, Health & Safety
Duke Energy
526 South Church Street
Mail Code EC3XP
Charlotte, North Carolina 28202
NORTH CAROLINA
Environmental Quality
July 19, 2019
Subject: Low Volume Waste Ponds — Mayo Steam Electric Plant
Dear Mr. Draovitch:
On June 26, 2019, the North Carolina Department of Environmental Quality Division of Water Resources
(Division) received an email (attached) from Kimberlee Witt to Raleigh Regional Office Staff regarding
the Low Volume Waste Ponds (LVWPs) at the Mayo Steam Electric Plant. The request was to confirm
that evaluation of the LVWPs is required. Based on the information provided by Duke Energy in the
referenced email, the Division has determined that an evaluation of the LVWPs is not required at this time.
However, assessment may be required once the LVWPs are proposed for closure since they are currently
active and part of NPDES Permit NC0038377. At that time, the Division recommends contacting the
Raleigh Regional Office for further guidance on the closure process and subsequent assessment.
If you have any questions, please contact Eric Rice (Raleigh Regional Office) at [phone] or Steve
Lanter (Central Office) at [phone].
Sincerel , +�
n Risg d, Chief
Animal • eeding Operations and Groundwater Section
Attachment: Email from Kimberlee Witt to Eric Rice and Rick Bolich dated June 26, 2019
cc: RRO WQROS Regional Office
Sergei Chernikov — Division of Water Resources Water Quality Permitting Section
WQROS Central File Copy
North Carolina Department of Environmental Quality I Division of Water Resources
•/ 512 North Salisbury Street 1 1636 Mail Service Center I Raleigh, North Carolina 27699-1636
919.707.9000

Smith, Eric G
From: Witt, Kimberlee <[e-mail]>
Sent: Wednesday, June 26, 2019 3:55 PM
To: Rice, Eric; Bolich, Rick
Cc: Lanter, Steven; Smith, Eric G; Sullivan, Ed M; Davies, Scott E.; Toepfer, John R; Wylie, Jerry
-synterracorp
Subject: [External] Duke Energy Mayo Steam Electric Plant Low Volume Waste Pond Evaluation
Requirement - CONFIRMATION REQUESTED
to
RESPONSE REQUESTED
Good afternoon Eric and Rick -
As previously discussed, Duke Energy requests the NCDEQ Raleigh Regional Office review the requirement for evaluation
of the Mayo Steam Electric Plant (Mayo) "low volume waste ponds" (LVPs) based on the technical guidance for
primary/secondary source assessment and corrective action guidance provided by NCDEQ and historical operations
noted below to confirm evaluation of the LVPs is required.
In a letter dated September 8, 2017 from NCDEQ to Duke Energy (Zimmerman to Sullivan), technical direction for
assessment and corrective action for sources of groundwater and soil contamination at coal ash facilities noted Duke
Energy must address soil and groundwater contamination from primary and secondary sources at coal ash facilities
noting:
• primary sources - CCR storage areas, raw coal piles, and structural fills
• secondary sources - residual soil and groundwater contamination from primary sources
A set of two ponds noted as the "low volume ponds" (LVP) was identified in a draft reference list of primary/secondary
sources to be reviewed by the NCDEQ Raleigh Regional Office during a June 26, 2018 Mayo Comprehensive Site
Assessment review meeting where NCDEQ and Duke Energy were present.
On April 5, 2019 in a letter from NCDEQ to Duke Energy (Hallman to Draovitch), the LVP at Mayo identified as a
primary/secondary source requiring evaluation for soil and groundwater contamination.
Duke Energy has performed an internal review of historical documents and operations related to the "low volume
ponds". CCR material has not been nor is currently stored in the LVPs.
Supporting Historical Information
The two ponds noted as LVPs were designed and constructed in the early 1980s as a chemical cleaning waste basin
(north), currently referred to as the low volume waste treatment basin, and oily waste basin (south). Both basins were
constructed with a 6" thick concrete bottom and 4" thick concrete side slopes. The chemical cleaning waste basin was
coated with a urethane bitumen sealant prior to placing in service.
Both basins are included in the current Mayo NPDES Permit No. NCO038377.
• The basins are noted as the "oily water basin" and "low volume waste treatment basin" in the NPDES
permit documents
• Pages 41 and 42 of the permit application describe the oily waste basin and the low volume waste treatment
basin as contributing to the ash basin (002) discharge

• Pages 47 lines 7 and 8 of the permit application describe the two basins
Wastewater flows into each basin consist of:
• oily water basin — historically and currently receives water from the oily water separator
• low volume waste treatment basin -
o received only the initial discharge of boiler chemical cleaning wastewater; subsequent boiler chemical
cleaning wastewater was sent to frac tanks for offsite disposal, the urethane bitumen sealant was
removed and basin restored to the concrete surface;
o was lined with a HDPE liner to temporarily receive Thermal Evaporator brine during commissioning of the
unit; in 2014 the brine and liner were removed and basin cleaned, and
o is currently used as a cooling pond to reduce the temperature of boiler water prior to traveling in HDPE
piping.
Please call or email if you need additional information related to this request for confirmation -
Kim
Kimberlee Witt, PE, ME
DUKE ENERGY
Sr. Engineer - Environmental Services
2500 Fairfax Road
Greensboro, NC 27407
336-215-4576 m
336-632-3750 d