NC0004774_Modification_20191217 (3)

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ROY COOPER , ; )<
Governor ,
MICHAEL S.REGAN
Secretary
LINDA CULPEPPER *44Q.00
Director NORTH CAROLINA
Environmental Quality
December 17, 2019
Mr. Paul Draovitch, Senior Vice President
Environmental, Health and Safety
Duke Energy Carolinas, LLC
Mail Code EC 13K
P.O. Box 1006
Charlotte, North Carolina 28201-1006
Subject: Permit Major Modification
Permit NC0004774
Buck Combined Cycle Station
Rowan County
Facility Class I
Dear Mr. Draovitch:
The Division has received your request to eliminate temperature requirements for the
coal-fired units due to the conversion to the natural gas. The request has been granted. This
modification becomes effective immediately. Enclosed with this letter are 4 pages that include
necessary changes. Please replace the existing permit pages with the modified pages.
The permit modification contains the following significant changes from your
current permit:
• Elimination of the footnote temperature requirements for Outfall OO1A and Outfall 006.
No other changes have been made. This permit modification is issued pursuant to the
requirements of North Carolina General Statute 143-215.1 and the Memorandum of Agreement
between North Carolina and the U.S. Environmental Protection Agency.
Please take notice that this permit is not transferable. Part II, E.4. addresses the
requirements to be followed in case of change in ownership or control of this discharge.
If you have any questions or need additional information, please contact Sergei
Chernikov, telephone number [phone] or email: [e-mail].
Sincerely,
of Linda Culpepper, Director
Division of Water Resources
cc: Central Files
NPDES Files
Mooresville Regional Office/Water Quality
WSS/Aquatic Toxicology Unit(e-copy)
EPA Region IV (e-copy)
E Q,.1
North Catulma Department of Environmental Quality Diynion of Water Resources
512 North Salisbury Street 11617Mail Service Ceram Raleigh North Carolina 27699 1611

Permit NC0004774
A.(3.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (Outfall 001A-CTCC
Operations)
[15A NCAC 02B .0400 et seq.,02B .0500 et seq.]
a. During the period beginning upon both elimination of all remaining waste flows from the Buck Steam
Station and diversion of CTCC Plant flows to Outfall 001A and lasting until diversion of CTCC Plant
flows to Outfall 006 or until permit expiration,whichever is first,the Permittee is authorized to
discharge wastewaters,as described herein,from Outfall 001A.Such discharges shall be limited and
monitored by the Permittee as specified below:
EFFLUENT LIMITATIONS MONITORING REQUIREMENTS
PARAMETER Monthly Daily Measurement Sample Sample
Average Maximum Frequency Type Location
i
Daily Pump logs Effluent
Flow,MGD or similar readings
pH >_ 6.0 and <_ 9.0 standard units Daily2 Grab Effluent
Temperature
35°C 95
of Daily Grab Effluent
Intake and
Temper
ature Daily Grab Effluent
Total Nitrogen mg/L3
Monthly Grab Effluent
9 ,
Total Phos horns mg/L Monthly Grab
Effluent
P
Total Suspended Solids 23.0 mg/L 74.0 mg/L 2/Month Grab Effluent
Oil and Grease 11.0 mg/L 15.0 mg/L 2/Month Grab Effluent
Total Residual Chlorine 4 28.0 pg/L 2/Month Grab Effluent
Free Available Chlorine 4 200 pg/L 500 pg/L 2/Month Grab Effluent
Total Hardness,mg/L as CaCO3 2/Month Grab Effluent
Total Arsenic, pg/L 5 Quarterly Grab Effluent
Total Selenium, pg/L 5 Quarterly Grab Effluent
Total Mercury, ng/L 5 Quarterly Grab Effluent
Total Aluminum, mg/L 5 Quarterly Grab Effluent
Total Antimony,pg/L 5 Quarterly Grab Effluent
Total Chromium 5-6 200 pg/L 200 ug/L 2/Month Grab Effluent
Total Copper 5 Quarterly Grab Effluent
Total Nickel, pg/L 5 Quarterly Grab Effluent
Total Zinc 5-6 1,000 pg/L 1,000 pg/L 2/Month Grab Effluent
Total Fluoride, mg/L Quarterly Grab Effluent
Chloroform, pg/L 7 Quarterly Grab Effluent
Chronic Toxicity 8 P/F @ 0.1% Quarterly Grab Effluent
The 126 priority pollutants
except Total Chromium and No detectable amount Annually Grab Effluent
Total Zinc 5,6
Footnotes:
1. Effluent sampling shall be conducted below the final treatment unit and prior to mixing with any other waste
streams.Intake means the facility's raw water intake.
2. Upon completing at least three consecutive months of daily pH readings,the Permittee may request that pH
monitoring be reduced to Weekly.Such request should demonstrate to the Division's satisfaction that the results of
weekly monitoring will adequately represent the measure and variability of effluent pH.If a request was approved
for Outfall 001A,the approval may be extended to Outfall 006 without requiring resubmittal of the request.
(Footnotes continue on next page.).
5

Permit NC0004774
A.(3.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (cont.)
Footnotes(cont):
3. Total Nitrogen=NO2-N+NO3-N+TKN
4. The Division shall consider all effluent TRC values reported below 50 µg/L to be in compliance with the permit.
However,the permittee shall continue to record and submit all values reported by a North Carolina certified
laboratory(including field certified),even if these values fall below 50 µg/L. Neither free available chlorine(FAC)
nor TRC may be discharged from any single generating unit for more than two hours in any single day,and not
more than one unit in the plant may discharge FAC or TRC,unless the discharger demonstrates to the Division that
the unit(s)cannot operate at or below this level of chlorination.
5. See Special Condition C.(6.)Metals Analyses.
6. See Special Condition C.(7.)Priority Pollutant Limitations and Analysis.
7. See paragraph(g)of this condition.
8. See Special Condition C.(8.)Chronic Toxicity Permit Limit.
b. Authorized waste flows from the CTCC Plant are potable,service,and process water treatment
wastes;floor drain wastes;cooling tower blowdown;heat recovery steam generator(HRSG)and
auxiliary boiler blowdowns;and stormwater flows draining to the sump.Such waste flows shall not
pass through the ash settling pond prior to discharge.c. There shall be no discharge of metal cleaning waste or chemical metal cleaning waste.
d. There shall be no discharge of floating solids or visible foam in other than trace amounts.
e. This condition is not intended to authorize concurrent waste discharges through both Outfalls 001A
and 006 except to the extent necessary to make an orderly transition to the newer outfall.The
Permittee shall cease discharge at Outfall 001A as soon as practical after bringing Outfall 006 online.
f. Unless it has already done so in accordance with Special Condition A.(2.) (e),the Permittee shall
analyze a representative sample of the CTCC Plant Wastewater Sump discharge and submit a
complete and accurate EPA Application Form 2C for the sump discharge no later than the date
established per Condition A.(2.)(e).
g. If chloroform monitoring was waived in accordance with conditions A.(2.)(a)and(f),the monitoring
requirement specified in paragraph(a)of this condition is waived for the remainder of the permit
term. If the initial chloroform analysis is conducted while this condition is effective,and if the initial
analysis does not yield a reportable concentration of chloroform(PQL<2.0 pg/L),chloroform
monitoring specified in paragraph(a)of this condition is waived for the remainder of the permit term.
h. The mixing zone for thermal discharges from the Buck facility is defined as that portion of the Yadkin
River(High Rock Lake)extending from the Buck Combined Cycle Station water intake to High Lake Dam.TheRock
thermal variance and mixingg
zone terminate on expiration of this permit.The Director
may reopen the permit to extend or modify the variance based on the findings of the Thermal Mixing
Zone Study(see Special Condition C.(13.))or other new information.
i. When High Rock Lake,as measured at the intake of the Buck Combined Cycle Station,is drawn down
10 feet or greater,the Permittee shall on a daily average basis ensure that the minimum unheated daily
average stream flow does not fall below one third of the 7-day 10-year low flow(7Q10).
j. The Permittee shall notify the Division in writing no later than seven calendar days prior to diversion
of CTCC Plant flows to Outfall 006;see Special Condition C.(2.)Notifications and Submittals.
6

Permit NC0004774
A.(4.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (Outfall 006-CTCC
Operations)
[15A NCAC 02B .0400 et seq.,02B .0500 et seq.]
a. During the period beginning upon both elimination of all remaining waste flows from the Buck Steam
Station and diversion of CTCC Plant flows to Outfall 006 and lasting until permit expiration,the
Permittee is authorized to discharge wastewaters,as described herein,from Outfall 006.Such
g
discharges shall be limited and monitored by the Permittee as specified below:
EFFLUENT LIMITATIONS MONITORING REQUIREMENTS
PARAMETER
Monthly Daily Measurement Sample Sample
Average Maximum Frequency Type Location 1
Flow, MGD Daily Pump logs Effluent
or similar readings
pH >_ 6.0 and <_ 9.0 standard units Daily2 Grab Effluent
Temperature 35°C(95°F) Daily Grab Effluent
Temperature Daily Grab Intake and
Effluent
Total Nitrogen, mg/L3 Monthly Grab Effluent
Total Phosphorus, mg/L Monthly Grab Effluent
Total Suspended Solids 23.0 mg/L 74.0 mg/L 2/Month Grab Effluent
Oil and Grease 11.0 mg/L 15.0 mg/L 2/Month Grab Effluent
Total Residual Chlorine 4 28.0 pg/L 2/Month Grab Effluent
Free Available Chlorine 4 200 pg/L 500 pg/L 2/Month Grab Effluent
Total Hardness, mg/L as CaCO3 2/Month Grab Effluent
Total Arsenic, L
N9/ 5 Quarterly Grab Effluent
Total Selenium, pg/L 5 Quarterly Grab Effluent
Total Mercury, ng/L 5 Quarterly Grab Effluent
Total Aluminum, mg/L 5 Quarterly Grab Effluent
Total Antimony, pg/L 5 Quarterly Grab Effluent
Total Chromium 5.6 200 pg/L 200 pg/L 2/Month Grab Effluent
Total Copper 5 Quarterly Grab Effluent
Total Nickel, pg/L 5 Quarterly Grab Effluent
Total Zinc 5.6 1,000 pg/L 1,000 pg/L 2/Month Grab Effluent
Total Fluoride, mg/L Quarterly Grab Effluent
Chloroform, pg/L 7 Quarterly Grab Effluent
Chronic Toxicity 8 P/F @ 0.1% Quarterly Grab Effluent
The 126 priority pollutants
except Total Chromium and No detectable amount Annually Grab Effluent
Total Zinc 5,6
Footnotes:
1. Effluent sampling shall be conducted below the final treatment unit and prior to mixing with any other waste
streams.Intake means the facility's raw water intake.
2. Upon completing at least three consecutive months of daily pH readings,the Permittee may request that pH
monitoring be reduced to Weekly.Such request should demonstrate to the Division's satisfaction that the results of
weekly monitoring will adequately represent the measure and variability of effluent pH.If a request was approved
for Outfall 001A,the approval may be extended to Outfall 006 without requiring resubmittal of the request.
(Footnotes continue on next page.)
7

Permit NC0004774
A.(4.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (cont.)
Footnotes(cont.):
3. Total Nitrogen=NO2-N+NO3-N+TKN
4. The Division shall consider all effluent TRC values reported below 50 µg/L to be in compliance with the permit.
However,the permittee shall continue to record and submit all values reported by a North Carolina certified
laboratory(including field certified),even if these values fall below 50 µg/L. Neither free available chlorine(FAC)
nor TRC may be discharged from any single generating unit for more than two hours in any single day,and not
more than one unit in the plant may discharge FAC or TRC,unless the discharger demonstrates to the Division that
the unit(s)cannot operate at or below this level of chlorination.
5. See Special Condition C.(6.)Metals Analyses.
6. See Special Condition C.(7.)Priority Pollutant Limitations and Analysis.
7. See paragraph(g)of this condition.
8. See Special Condition C.(8.)Chronic Toxicity Permit Limit.
b. Authorized waste flows from the CTCC Plant are potable,service,and process water treatment
wastes;floor drain wastes;cooling tower blowdown;heat recovery steam generator(HRSG)and
auxiliary boiler blowdowns;and stormwater flows draining to the sump.Such waste flows shall not
pass through the ash settling pond prior to discharge.
c. There shall be no discharge of metal cleaning waste or chemical metal cleaning waste.
d. There shall be no discharge of floating solids or visible foam in other than trace amounts.
e. Conditions A.(3.)and A.(4.)are not intended to authorize concurrent waste discharges through both
Outfalls 001A and 006 except as necessary to make an orderly transition to the new outfall.The
Permittee shall cease discharge at Outfall 001A as soon as practical after bringing Outfall 006 online.
f. Unless it has already done so in accordance with Special Condition A.(2.) (e)or A.(3.)(f),the Permittee
shall analyze a representative sample of the CTCC Plant Wastewater Sump discharge and submit a
complete and accurate EPA Application Form 2C for the sump discharge no later than the date
established in condition A.(2.)(e).
g. If chloroform monitoring was waived in accordance with conditions A.(2.)a)and(f)or conditions
A.(4.)(a)and(g),the monitoring requirement specified in paragraph(a)of this condition is waived for
the remainder of the permit term.If the initial chloroform analysis is conducted while this condition is
effective,and if the initial analysis does not yield a reportable concentration of chloroform(PQL<2.0
pg/L),chloroform monitoring specified in paragraph(a)is waived for the remainder of the permit
term.
h. The mixing zone for thermal discharges from the Buck facility is defined as that portion of the Yadkin
River(High Rock Lake)extending from the Buck Combined Cycle Station water intake to High Rock
Lake Dam.The thermal variance and mixing zone terminate on expiration of this permit.The Director
may reopen the permit to extend or modify the variance based on the findings of the Thermal Mixing
Zone Study(see Special Condition C.(13.))or other new information.
i. When High Rock Lake,as measured at the intake of the Buck Combined Cycle Station,is drawn down
10 feet or greater,the Permittee shall on a dailyaverage basis ensure that the minimum unheated daily
average stream flow does not fall below one third of the 7-day 10-year low flow(7Q10).
j. The Permittee shall notify the Division in writing no later than seven calendar days following the
closure of Outfall 001A to confirm its closure;see Special Condition C.(2.)Notifications and
Submittals.
8