NC0086665_Approval_20240306

North Carolina Department of Environmental Quality | Division of Water Resources | Bio Lab
4401 Reedy Creek Road | 1621 Mail Service Center | Raleigh, North Carolina 27699-1621
919.743.8400

March 6, 2024

To: Joyce Dishmon
Duke Energy
(via email: [e-mail])

From: Cindy Moore
Aquatic Toxicity Branch

Subject: Biocide Use Review
Rockingham County Combustion Turbine Facility
NPDES # NC0086665
Rockingham County

Rockingham County Combustion Turbine Facility has requested approval of the chemical, FQS 1.5
Microbicide. This product will be discharged from Outfall 001 and into an UT to Little Jacobs Creek.

Calculations predict the use of this product, at the stated dosage rate of 0.13 grams/day, calculated
below, will not cause toxic impacts to aquatic life in the receiving stream, the Lumber River. Therefore,
the use of this product as an additive to the cooling tower blowdown, non-contact cooling water, and
occasional draining from other operational systems at the Rockingham County Combustion Turbine
Facility is acceptable.

17 gallons biocide = x gallons biocide
1.4 MG fuel oil 1000 gallons of oil in OWS

17,000 gallons = 0.012 gallons biocide
1,400,000 gallons per year

0.012 gal/year x 3.783 L/gallon x 1000 mil/liter x 1 g/ml x 1.06 = 48.14 g/ 365 days (because OWS only sees
1000 gallons/year oil) = 0.13 g/day

If you have any questions or concerns, please contact Molly Nicholson at [phone] or
[e-mail].

Sincerely,

Cindy Moore, Supervisor
Aquatic Toxicology Branch
Division of Water Resources, NCDEQ

cc: Sergei Chernikov, DWR (via email: [e-mail])
Jenny Graznak, WSRO (via email: [e-mail])
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