NC0024406_Modification_20191212

Permit NCO024406
SUPPLEMENT TO PERMIT COVER SHEET
All previous NPDES Permits issued to this facility, whether for operation or discharge are hereby revoked. As of
this permit issuance, any previously issued permit bearing this number is no longer effective. Therefore, the
exclusive authority to operate and discharge from this facility arises under the permit conditions, requirements,
terms, and provisions included herein.
Duke Energy Carolinas, LLC is hereby authorized to:
I . Continue to discharge:
• Outfall 001: once through cooling water consisting of intake screen backwash,
recirculating cooling water, station equipment cooling water and once -through
cooling water. This outfall discharges to Belews Lake.
• Outfall 003: Stormwater and remediated groundwater. This outfall discharges to
Unnamed Tributary (UT) to Dan River.
• Internal Outfall 002: FGD wastewater (discharging to line retention basin).
• Outfall 003A/006. Discharge from the new Lined Retention Basin. Basin will
accept wastes from holding basin, ash contact water, various sumps, coal pile
runoff, stormwater runoff, cooling tower blowdown, FGD wastewater, and various
low volume wastes such as boiler blowdown, oily waste treatment,
wastes/backwash from the water treatment processes, coal pile collection basins
(collecting contact stormwater from coal piles), plant area wash down water,
cooling tower blowdown, equipment heat exchanger water, remediated
groundwater, emergency overflow (rain in excess of designed storm event), toe
drain (potential discharge to outfall 006 only), emergency release of anhydrous
ammonia, release of ammonia during quarterly testing, and treated domestic
wastewater. Outfall 003A discharges to UT to Dan River via the Outfall 003.
Construction of new Outfall 006 has been completed. Outfall 006 will discharge to
Dan River. This Outfall will be used for decanting and dewatering of the ash
basin.
• Outfall 005. This is a former stormwater outfall SW002, consisting of once
through non -contact chiller water and stormwater. This outfall discharges to
Belews Lake.
• Internal Outfall 006A. This is a temporary internal outfall for decanting and
dewatering of the ash basin, it will discharge through new Outfall 006.
• Outfall 007 (lat. - 360 16'51.604"; long. 80003'52.995"). This is an emergency
spillway for South Coal Basin. This outfall discharges to Belews Lake. The
spillway is designed for a flood greater than 100-year event. Sampling of this
spillway is waived due to unsafe conditions associated with sampling during
overflow events.
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Permit NCO024406
A. (4.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS (Internal
Outfall 006A - dewatering/decanting)
[15A NCAC 02B .0400 et seq., 02B .0500 et seq.]
During the period beginning on the commencement of decanting and lasting until expiration of the
permit, the Permittee is authorized to discharge from Outfall 006A Ash settling basin (Dewatering —
removing the interstitial water. Decanting- decanting the free water above the settled ash
layer). Such discharges shall be limited and monitored5 by the Permittee as specified below:
PARAMETER
LIMITS
MONITORING REQUIREMENTS
Monthly
Average
Daily
Maximum
Measurement
Frequency
Sample Type
Sample Location
Flow
2.0 MGD11
Daily
Pump logs or
estimate
Effluent
Oil and Grease'
15.0 mg/L
20.0 mg/L
Weekly
Grab
Effluent
Total Suspended Solids' 7
30.0 mg/L
50.0 mg/L
Weekly
Grab
Effluent
Total Arsenic
Weekly
Grab
Effluent
Chlorides, mg/L
Weekly
Grab
Effluent
Total Iron, mg/L10
1.0 mg/L
1.0 mg/L
Weekly
Grab
Effluent
Total Copper
211.3 Ng/L
231.4 Ng/L
Weekly
Grab
Effluent
Total Selenium
134.0 Ng/L
1,237 Ng/L
Weekly
Grab
Effluent
Total Molybdenum
4,289 Ng/L
4,289 Ng/L
Weekly
Grab
Effluent
Total Aluminum
174.2 mg/L
174.2 mg/L
Weekly
Grab
Effluent
Fluoride, mg/L
Weekly
Grab
Effluent
Chromium VI, Ng/L
Weekly
Grab
Effluent
Total Cadmium, Ng/L
Weekly
Grab
Effluent
Total Zinc, Ng/L
Weekly
Grab
Effluent
Total Nickel, Ng/L
Weekly
Grab
Effluent
Total Dissolved Solids, mg/L
Weekly
Grab
Effluent
Total Phosphorus, mg/L
Monthly
Grab
Effluent
Total Nitrogen (NO2 + NO3 + TKN), mg/L
Monthly
Grab
Effluent
Chronic Toxicity2
Monthly
Grab
Effluent
pH3,8
Weekly
Grab
Effluent
Bromides, mg/L
Weekly
Grab
Effluent
Total Lead
30.5 Ng/L
654.6 Ng/L
Weekly
Grab
Effluent
Total Thallium, Ng/L
Weekly
Grab
Effluent
Total Barium, mg/L
Weekly
Grab
Effluent
Sulfates, mg/L
Weekly
Grab
Effluent
Total Antimony, Ng/L
Weekly
Grab
Effluent
Total Mercury4, ng/L
Weekly
Grab
Effluent
Turbidity6, NTU
Weekly
Grab
Effluent
Total Hardness, mg/L
Weekly
Grab
Effluent
Ammonia9
1.0 mg/L
5.0 mg/L
Variable
Grab
Effluent
Notes:
1. Monitoring for TSS, oil and grease and all toxicants shall be performed concurrently with the
Chronic Toxicity test.
2. Whole Effluent Toxicity shall be monitored by chronic toxicity (Ceriodaphnia) P/F at 3.7%. See
Condition A. (14.) for details.
3. The pH shall not be less than 6.0 standard units nor greater than 9.0 standard units.
4. The facility shall employ method 1631E.
5. Please See Special Condition A. (23.).
6. The discharge from this facility shall not cause turbidity in the receiving stream to exceed 50 NTU.
If the instream turbidity exceeds 50 NTU due to natural background conditions, the discharge
cannot cause turbidity to increase in the receiving stream. Therefore, if the effluent measurement
exceeds 50 NTU, the Permittee shall sample upstream and downstream turbidity in the receiving
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