NCG120101_Tier Relief Letter from RRO_20180220

Energy, Mineral
and Land Resources
ENVIRONMENTAL QUALITY
Duke Energy
Attn: Tom Copolo
10660 Boston Road
Roxboro, NC 27574
f® cLR3
February 20, 2018
SUBJECT: NPDES Stormwater Permit: Request for Regulatory Relief
Mayo Electric Generating Plant -Mayo Steam Plant Monofill
General Permit No: NCG120000; COC No: NCG120101
Person County
Mr. Copolo:
ROY COOPER
Governor
MICHAEL S. REGAN
secretary
WILLIAM E. VINSON, JR,
Interim Director
In response to your request for Regulatory Relief, NCDENR-Land Quality Section staff reviewed
provided sample reports, site maps and discussed site characteristics with Lori Tollie the EHS
CCP permitting and compliance officer.
Monthly monitoring has been triggered by two consecutive exceedances of the Fecal Coliform
benchmarks at your facility. Please keep in mind that benchmark exceedances are NOT limit
violations or violations of permit conditions; however, you are obligated to follow the tiered
response actions outlined in your permit. Mayo Electric Generating Plant has been following the
tiered response actions and therefore is in compliance with the permit.
Based on your materials inventory and certification that industrial activities at Mayo Electric
Generating Plant - Mayo Steam Plant Monofill would not generate concentrated amounts of
Fecal Coliform into stormwater. For that reason, we are granting regulatory relief in the form of a
collapsed Tier 2 — Tier 3 response. Upon receipt of this letter, Mayo Electric Generating Plant
may resume the permit specified semiannual analytical monitoring for the remainder of your
current permit. Your current permit is set to expire on October 31, 2018'. This decision only
applies to the Fecal Coliform benchmarks. A benchmark exceedance of any other parameter
listed in your permit will trigger tiered response actions as described in the general permit.
You must notify this office in writing, within five business days, if you become aware of any
significant source of Fecal Coliform at your facility that has the potential to be exposed to
stormwater. The relief granted in this letter is contingent upon the current industrial practices at
Mayo Electric Generating plant -Mayo Steam Plant Monofill. if industrial practices change and
Fecal Coliform does become a significant stormwater exposure risk then this office reserves the
right to withdraw this decision and reinstate the permit specified tiered response or other actions
State of North Carolina j Environmental Quality i Energy, Mineral, and Land Resources
Raleigh Regional Office ; 1628 Mail Service Center ; Raleigh, NC 27609
919 791 4200

Duke Energy, ATTN: Tom Copolo
February 20, 2018
Page 2 of 2
that may be warranted by the new set of circumstances.
Please retain and append this letter to your Stormwater Pollution Prevention Plan (SPPP) or
permit. If you have any questions or comments concerning this letter, please contact Thad
Valentine or Diane Adams at [phone].
Sincerely,
William H. Denton, IV, PE
Regional Engineer-RRO
Enclosure
ec: Bethany Georgoulias, RCO