NCG500582_Biocide Use Review Packet_20210212 (4)

Southern Power
January 21, 2021
Ms. Susan Meadows
Division of Water Resources
Aquatic Toxicology Unit
1621 Mail Service Center
Raleigh, NC 27699-1621
Re: Submission of BiocidelChemical Treatment Worksheet — Form 101
Dear Ms. Meadows:
Southern Power Company
3535 Colonnade Parkway
Birmingham, AL 35243
Southern Power Company (SPC) is submitting the attached BiocidelChemical Treatment Worksheet — Form
101 for the Plant Rowan County Power Station which is covered under general permit NCG500582, The
permit covers discharges originating from cooling tower blowdown, non -contact cooling water, and
occasional drainage from operational systems. The facility is located at 5755 NC HWY 801 in Salisbury,
NC and discharges to Second Creek through Outfall 002. The station consists of five combustion turbine
units, one steam turbine unit, and a cooling tower.
SPC has been using Gengard 7004 as a corrosion inhibitor since January 14, 2020 but is seeking approval
to use Gengard 8020 instead. For this Biocide form, SPC used a 7Q10 flow of 6.9 cfs for Second Creek,
which was provided by Ms. Teresa Rodriguez with the Division of Water Resources (DWR) on November
11, 2015. The volume of the system was determined to be 1.5 million gallons per day (MGD) based on the
capacity of the cooling tower and the associated piping, and the average daily discharge was determined to
be 0.216 MGD. The dosage rate of Gengard 8020 was determined to be 16 gallons/day (or 68,638
grams/day). SPC also assumed no decay rate when calculating the degradation factor. Using the Safety
Data Sheet, SPC determined the lowest LC501EC50 for Gengard 8020 to be 3,628 mg/L for Daphnia
magna (static renewal bioassay, 48-hour, pH adjusted).
Using the worksheet, SPC determined that its usage of Gengard 8020 is compliant with regulated
limitations.
Please review the attached Biocide form and supporting documentation. Should you have any questions or
require additional information, please do not hesitate to contact Corey Ladner at 205.992.0050 or via email
at [e-mail]. We look forward to hearing from you in the near future.
Sincerely,
J=;se E
'-- ant M
Southern -•wer Company

BIOCIDE/CHEMICAL TREATMENT
WORKSHEET-FORM 101
The following calculations are to be performed on any biocidal products ultimately discharged to the surface waters of
North Carolina. This worksheet must be completed separately for each biocidal product in use. This worksheet is to be
returned with all appropriate data entered into the designated areas with calculations performed as indicated.
I. Facility Name: Southern Power Plant Rowan
NPDES # NC: NCG500582 Outfall #002
County: Rowan County
Receiving Stream: Second Creek 7Q10: 6.9 (cfs)
(All above information supplied by the Division of Water Quality)
What is the Average Daily Discharge (A.D.D.) volume of the water handling systems to the receiving water body?
A.D.D. = 0.216 (in M.G.D.)
Please calculate the Instream Waste Concentration (IWC in percent) of this discharge using the data entered
above.
(A.D.D.) X 100 ( 0.216 ) X 100 0
IWC = (7Q10)(0.646) + (A.D.D) = ( 6.9 )(0.646) + ( 0.216 ) = 4.62 /o
This value (IWC) represents the waste concentration to the receiving stream during low flow conditions.
II. What is the name of the whole product chemical treatment proposed for use in the discharge identified in Part I?
Gengard 8020
Please list the active ingredients and percent composition:
Maleic Acid (CAS# 110-16-7) 0.1-1
What feed or dosage rate (D.R.) is used in this application? The units must be converted to maximum grams
of whole product used in a 24hr period.
D.R.= 68,638 grams/24hr period
Please note, fluid ounces (a volume) must be converted to grams (a mass). The formula for this conversion is:
Grams of product = fluid oz. of product X 1 gal. water X 8.34 lbs. X specific gravity of product X 453.59g.
128 fl. oz. 1 gal. water 1 Ib.

Facility Name: Southern Power Plant Rowan NPDES #: NC NCG500582
Estimate total volume of the water handling system between entry of biocidal product and NPDES discharge
point. On an attached sheet please provide justification for this estimate (system volume, average cycles per
blowdown, holding lagoon size, etc.)
Volume= 1.5 million gallons
What is the pH of the handling system prior to biocide addition? If unknown, enter N/A. 8 S.U.
What is the decay rate (D.K.) of the product? If unknown, assume no decay (D.K.=0) and proceed to asterisk.
The degradation must be stated at pH level within 1/2 pH standard unit within handling system. Enter the half life
(Half Life is the time required for the initial product to degrade to half of its original concentration). Please
provide copies of the sources of this data.
H.L. = Days
The decay rate is equal to H1L X 0.69 = 0
=Decay Rate (D.K.)
Calculate degradation factor (D.F.). This is the first order loss coefficient.
* D.F. - (V.D.D.)ome) + (D.K.) = S ( 115 ))
l + ( 0 ) = 0.144
Calculate Steady State Discharge Concentration:
Dischg Conc. _ (D.R.) ( 68,638 )
(D.F.)(Volume)(3785) - ( 0.144 )( 1.5 )(3785)
Calculate concentration of biocide instream during low flow conditions.
(Receiving Stream Concentration)
(Dischg. Conc.) x (IWC%) ( 83.95 ) x ( 4.62 )
100 - 100
83.95 mg/I
= 3.88 mg/I
Receiving Stream Concentration
III. Calculate regulated limitation.
List all LC50 and EC50 data available for the whole product according to the following columns. (Note that units
should be in mg/I). Please provide copies of the sources of this data.
Organism Test Duration LC50/EC50 (mg/1)
Fathead Minnow 96 hour 5,814 ma1L (LC50)
Daphnia manna
Rainbow Trout
48 hour 3,628 mg/L (LC50)
96 hour 7,071 ma1L (LC501
D. W Q. Fonn 101 (12019) 2

Facility Name: Southern Power Plant Rowan NPDES #: NC NCG500582
Choose the lowest LC501EC50 listed above:
Enter the LC501EC50: 3,628
If the half life (H.L.) is less than 4 days, perform the following calculation.
Regulated Limitation = 0.05 x LC50 = mg/I
If the half life (H.L.) is greater than or equal to 4 days or unknown, perform the following calculation.
Regulated Limitation = 0.01 x LC50 = 36.28 mg/I
Choose the appropriate regulated limitation from the calculations immediately above and place in this blank:
36.28 mglliter
From Part II enter the receiving stream concentration:
3.88 mg/liter
IV. Analysis.
If the receiving stream concentration is greater than the calculated regulated limitation, then this biocide is
unacceptable for use.
Person in Responsible Charge
Na � rint)
Signature
LA.-6tirkcvCo" -X g- (0601
Email Address & Phone Number
- Si 5T Pc
Date Physical Address of Facility
n Com • This Worksheet (If different from above)
Amanda Mueller amuelleraectinc.com 919-861-8888
Please submit to:
klYri Ard&
Signature
Division of Water Quality
Aquatic Toxicology Unit
1621 Mail Service Center
Raleigh, NC 27699-1621
Email Address & Phone Number
11/19/20
Date
Contact Info.: Cindy Moore (cindy.a.moore@ ncdenr.gov) or Susan Meadows ([e-mail])
D.W.Q. Forn 101 (112019)
3

Facility Name: Southern Power Plant Rowan NPDES #: NC NCG500582
Supplemental Metals Analysis
If copper, zinc, or chromium are present in the proposed biocidal compound, complete this worksheet. A separate form
must be used for each metal and/or metal compound present in the biocide. List the metal, its chemical formula, molecular
weight (MW), formula weight (FW), and the concentration of the metal compound in the biocide (MCC). Complete a
separate form for every metal present in the biocide.
Metal Chemical Formula Molecular Weight of Metal Formula Weight Concentration in Biocide
EXAMPLE
Copper CuSO4 5N2O 63.546 g/mole 249.680 g/mole 0.2 %
Dosage rate of Biocide (DR) (from page 1):
DR = grams/day
Average Daily Discharge (ADD) (from page 1):
ADD = million gallons/day
Discharge Concentration (DC) of Biocide:
DR ( Trams/day)
DC = ADD - ( million gallons/day)
Convert DC to microgramslliter (ppb):
- grams/million gallons
1 x 106 pg/g
DC (pg/I) = DC (grams/million gal) x _._.. - __WgJI
3.785 x 106 liters/million gal.
Calculate the fraction of metal in the metal -containing compound (MF):
MF = FW - (
MW ( grams/mole)
grams/mole) -
Calculate the fraction of metal in the biocidal compound (BF):
MCC (%) %
BF = MF x 100 = x (100)
Calculate the concentration of metal in the discharge (M):
M = DC x BF = pgll x = pgll
Calculate the instream metal concentration (IMC) at low flow conditions:
IMC = M x IW1 d0%) pgll x
Regulated limitation of metal (from below):
100 -
pgll
pgll
NC General Statutes 15A NCAC 28.0211 define:
Copper- 7 pgll water quality action level' Zinc- 50 pgll water quality action level*
Chromium- 50 pgll water quality standard
("Values which exceed action levels must be addressed directly by aquatic toxicity testing.)
D.W.Q. Form 101 (1/2019)