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Home My WebLink AboutNC0048879_Permit (Modification)_20231106 North Carolina Department of Environmental Quality Division of Water Resources 512 North Salisbury Street 1611 Mail Service Center Raleigh, North Carolina 27699-1611 919.707.9000 November 6, 2023 Mr. Jamie Revels, Utilities Director Town of Cary P.O. Box 8005 Cary, North Carolina 27512 Subject: Minor NPDES Permit Modification Permit NC0048879 North Cary WRF Wake County Grade IV Biological WPCS SIC Code 4952 Dear Mr. Revels: The Division of Water Resources (Division) received a letter from the Town of Cary (Town) on November 3, 2023 requesting a minor modification to NPDES Permit NC0048879 North Cary WRF to remove the conditional effluent monitoring requirement, limit and associated footnotes for Total Residual Chlorine (TRC). The Division has had numerous conversations with the Town to date regarding TRC requirements. The Town has been informed and understands the following: • The inclusion of the requirement for TRC monitoring and limitation was only applicable if, in an emergency situation, the Town found that its UV system, including its redundancies, was inoperable and the Town decided to employ chlorination as a means of disinfection. • The Division’s practice is to only issue Authorization to Construct (ATC) permits for permanent fixtures and would not require an ATC for a temporary activity such as temporary chlorination while a UV system is undergoing repair. • Opening and modifying the NPDES permit to add TRC requirements would take a length of time which is likely longer than the temporary chlorination activity. • Without the TRC language in the NPDES permit, the Town is not permitted to use chlorine as a means of disinfection. Should the Town find itself in a situation where it chooses to use chlorine disinfection as a temporary means of disinfection, the Town would be in violation with NPDES permit NC0048879. As each of these points has been clearly conveyed to the Town, the Division approved your request to remove the total residual chlorine requirements and associated footnotes from Section A.(1.) of the permit. Please insert the attached pages into your permit and discard the original pages. If any parts, measurement frequencies or sampling requirements contained in this permit are unacceptable to you, you have the right to an adjudicatory hearing upon written request within thirty (30) days following receipt of this letter. This request must be in the form of a written petition, conforming to Chapter 150B of the North Carolina General Statutes, and filed with the Office of Administrative Hearings (6714 Mail Service Center, Raleigh, North Carolina 27699-6714). Unless such demand is made, this decision shall be final and binding. DocuSign Envelope ID: 69CE8065-074A-42DF-BFD7-F33DE0331AD4 North Carolina Department of Environmental Quality Division of Water Resources 512 North Salisbury Street 1611 Mail Service Center Raleigh, North Carolina 27699-1611 919.707.9000 Please note that this permit is not transferable except after notice to the Division. The Division may require modification or revocation and reissuance of the permit. This permit does not affect the legal requirements to obtain other permits which may be required by the Division of Water Resources or any other Federal, State, or Local governmental regulations. If you have any questions concerning this permit, please contact Nick Coco at (919) 707-3609 or via email at nick.coco@deq.nc.gov. Sincerely, for Richard E. Rogers, Jr., Director Division of Water Resources, NCDEQ Hardcopy: NPDES Files Central Files Ecopy: US EPA Region 4 DWR/Raleigh Regional Office/Water Quality/Vanessa Manuel Town of Cary/Plant Manager/Jonathan Bulla DocuSign Envelope ID: 69CE8065-074A-42DF-BFD7-F33DE0331AD4 Permit NC0048879 Page 3 of 14 Modified 11/6/2023 PART I A.(1.) EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS [12.0 MGD] [15A NCAC 02B .0400 et seq., 15A NCAC02B .0500 et seq.] Grade IV Biological Water Pollution Control System [15A NCAC 08G .0302] (a.) During the period beginning on the effective date of the permit and lasting until permit expiration, the permittee is authorized to discharge treated municipal and industrial wastewater from Outfall 001. Such discharges shall be limited and monitored1 by the permittee as specified below: PARAMETER Parameter Code EFFLUENT LIMITS MONITORING REQUIREMENTS Monthly Average Weekly Average Daily Maximum Measurement Frequency Sample Type Sample Location2 Flow 50050 12.0 MGD Continuous Recording I or E Total Monthly Flow (MG) 82220 Monitor and Report Monthly Calculated E CBOD, 5 day, 20°C 3 (Apr 1 - Oct 31) 80082 4.1 mg/L 6.0 mg/L 2/week 4 Composite I and E CBOD, 5 day, 20°C 3 (Nov 1 - Mar 31) 80082 8.2 mg/L 12.3 mg/L 2/week 4 Composite I and E Total Suspended Solids3 CO530 30.0 mg/L 45.0 mg/L 2/week 4 Composite I and E NH3 as N (Apr 1 - Oct 31) CO610 0.5 mg/L 1.5 mg/L 2/week 4 Composite E NH3 as N (Nov 1 - Mar 31) CO610 1.0 mg/L 3.0 mg/L 2/week 4 Composite E Fecal Coliform (geometric mean) 31616 200/100 mL 400/100 mL 2/week 4 Grab E Dissolved Oxygen 00300 Daily Average ≥ 5.0 mg/L Daily Grab E pH 00400 Between 6.0 and 9.0 Standard Units Daily Grab E Temperature (°C) 00010 Monitor and Report Daily Grab E Total Phosphorus (mg/L) CO665 2.0 mg/L (Quarterly Average)5 Weekly Composite E TKN (mg/L) 00625 Monitor and Report Weekly Composite E NO3-N + NO2-N (mg/L) 00630 Monitor and Report Weekly Composite E Total Nitrogen 6 (mg/L) CO600 Monitor and Report Weekly Calculated E TN Load 7,8 QM600 QY600 Monitor and Report (lb/month) 143,246 lb/yr Monthly Annually Calculated E PFAS various Footnote 9 Footnote 9 Grab E Chronic Toxicity 10 TGP3B Monitor and Report Quarterly Composite E Effluent Pollutant Scan 11 NC01 Monitor and Report Footnote 11 Footnote 11 E Hardness12 -Total as CaCO3 (mg/L) 00900 Monitor and Report Quarterly Composite E Footnotes: 1. The permittee shall submit Discharge Monitoring Reports electronically using NC DWR’s eDMR application system. See Special Condition A.(10.). 2. Sample locations I-Influent, E-Effluent. 3. The monthly average effluent CBOD5 and Total Suspended Solids concentrations shall not exceed 15% of the respective influent value (85% removal). 4. Twice per week sampling must occur on any two non-consecutive days during the calendar week. 5. The quarterly average for total phosphorus shall be the average of composite samples collected during each calendar quarter (January - March, April - June, July - September, October - December). 6. For a given wastewater sample, TN = TKN + NO3-N + NO2-N, where TN is Total Nitrogen, TKN is Total Kjeldahl Nitrogen, and NO3-N and NO2-N are Nitrate and Nitrite Nitrogen, respectively. Footnotes continue on the next page. DocuSign Envelope ID: 69CE8065-074A-42DF-BFD7-F33DE0331AD4 Permit NC0048879 Page 4 of 14 Modified 11/6/2023 Footnotes continued from A.(1.) Effluent Limitations and Monitoring Requirements: 7. TN Load is the mass load of TN discharged by the permittee in a period of time. See Special Condition A.(5.). 8. Compliance with these limits shall be determined in accordance with Special Condition A.(6.), Annual Limits for Total Nitrogen. 9. See Special Condition A.(9.). 10. Chronic Toxicity (Ceriodaphnia dubia) P/F at 90% with testing in February, May, August, and November. See Special Condition A.(3.). 11. The permittee shall perform three effluent pollution scans during the term of this permit. See Special Condition A.(4.). 12. Effluent hardness shall be performed in conjunction with testing for hardness dependent metals. There shall be no discharge of floating solids or visible foam in other than trace amounts. DocuSign Envelope ID: 69CE8065-074A-42DF-BFD7-F33DE0331AD4