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Home My WebLink AboutNC0036269_Fact Sheet_20130904Fact Sheet NPDES NC0036269 Permit Renewal Page 1 DENR/DWR FACT SHEET FOR NPDES PERMIT DEVELOPMENT NPDES No. NC0036269 Facility Information Applicant/Facility Name: Water & Sewer Authority of Cabarrus County/Rocky River Regional WWTP Applicant Address: PO Box 428, Concord, NC 28025 Facility Address: 6400 Breezy Lane, Concord, NC 28026 Permitted Flow 24, 26.5 & 34 MGD Type of Waste: Domestic 95% / Industrial 5% Facility/Permit Status: Class IV/renewal County: Cabarrus Miscellaneous Receiving Stream: Rocky River Regional Office: Mooresville Stream Classification: C State Grid / USGS Quad: F16E/Concord SE 303(d) Listed? Yes Permit Writer: Teresa Rodriguez HUC: 03040105 Date: 9/4/2013 Drainage Area (mi2): 278 Lat. 35 19’ 30.5” N Long. 80 32’ 9.6” W Summer 7Q10 (cfs) 25.2 Winter 7Q10 (cfs) 35.2 Average Flow (cfs): 300 IWC (%): 59.6 % (24 MGD) 62 % (26.5 MGD) 67.7 % (34 MGD) SUMMARY The Water and Sewer Authority of Cabarrus County (WSACC) currently operates a Class IV WWTP with a permitted flow of 24 MGD and phased flows of 26.5 MGD and 34 MGD. The Rocky River Regional Wastewater Treatment Plant (RRRWWTP) serves a population of 172,415 which includes the Town of Harrisburg, Town of Mount Pleasant, City of Kannapolis, City o f Concord and a portion of Charlotte Mecklenburg Utility service area. The existing WWTP consists of: influent bar screen, grit removal, four primary clarifiers, first stage aeration, four secondary-intermediate clarifiers, second stage aeration, four secondary clarifiers, chlorine disinfection, de-chlorination, sludge thickener, sludge conditioner, biosolids handling facility, centrifuges, sludge incinerator, sludge ash settling basin, odor control system, and power generator. The facility has an active pretreatment program with 2 CIU and 12 non-categorical SIUs. The permit will continue to require the WSACC to implement their pretreatment program. WSACC submitted the renewal application, Form 2-A, on April 23, 2013. The current permit expires on October 31, 2013. Two permit modifications have been issued sinc e the permit was issued in 2008; one in March 2010 to add interim limits for a flow of 26.5 MGD and one in July 2010 to further detail the transition from 24 MGD to 26.5 MGD. The current average monthly flow is still below the threshold for the tiered limit of 26.5 MGD. RECEIVING STREAM This facility discharges to Rocky River in the Yadkin-Pee Dee River Basin, classified C waters in the Lower Rocky River watershed, HUC 03040105. The Rocky River is listed as impaired for copper and turbidity in the 2012 303(d) list. The Yadkin-Pee Dee River Basin Plan lists construction activities and stormwater runoff as the possible causes of high turbidity in the stream. The cause for the copper impairment is unknown. Fact Sheet NPDES NC0036269 Permit Renewal Page 2 DMR DATA REVIEW AND VERIFICATION OF EXISTING CONDITIONS A review of the DMRs for January 2008 through April 2013 shows compliance within permit limits. Data are summarized in Table 1. Table 1. Data Summary Parameter Units Average Max Min Flow MGD 14.4 96.6 11 CBOD mg/l 5.1 20.5 < 2 NH3N mg/l 1.5 29 < 0.1 TSS mg/l 17 62 < 25 pH SU 6.4 8.1 6 DO mg/l 8.5 12.4 6.1 Temperature °C 21 26 15 TRC µg/l 26 49 < 25 TN mg/l 21.6 29.2 9.9 TP mg/l 3.2 6.4 1.0 Fecal Coliform #/100 ml 16.5 > 23000 < 1 MERCURY EVALUATION: A full mercury evaluation as prescribed in the Permitting Guidance developed for the implementation of the statewide Mercury TMDL was not completed due to a limited amount of data. The facility provided the results of four samples for mercury. Based on dilution the water quality based effluent limitation (WQBEL) for mercury is 20.1 ng/l, while the TBEL is 47 ng/l. None of the sampling results is greater than the WQBEL. All the sample results are greater than 1 ng/L, therefore a Mercury Minimization Plan will be required in the permit. A condition will be added to the permit describing the requirements for the MMP. Monitoring for mercury will be included in the permit to collect more effluent data. LIMITS AND MONITORING REQUIREMENTS: Current conditions, as well as the basis for the limits are summarized in Table 2. Violations/enforcement cases. Table 2. Current Permit Conditions and Proposed Changes Parameters Affected Permit Condition Change from Previous Permit Basis for Condition/Change CBOD5 (summer) CBOD5 (winter) 17 mg/l M.A. 25 mg/l W.A. 25 mg/l M.A. 37.5 mg/l W.A. No changes Based on modeling results for protection of DO standard NH3-N (summer) NH3-N (winter) 4 mg/l M.A. 12 mg/l W.A. 10 mg/l M.A. 30 mg/L W.A No changes Based on modeling results for protection of DO standard TSS 30 mg/l M.A. 45 mg/l W.A. No changes 40 CFR 122, T15A 2B .0400: NPDES rules for secondary treatment of domestic wastewater D.O. > 6 mg/l No changes Based on modeling results Fact Sheet NPDES NC0036269 Permit Renewal Page 3 Temperature Daily monitoring No changes State WQ standards, T15A 2B .0200 pH 6 to 9 SU No changes State WQ standards, T15A 2B .0200 Total residual chlorine 28 μg/l No changes State WQ standards, T15A 2B .0200 Fecal Coliform 200/100ml M.A. 400/100 ml W.A. No changes State WQ standards, T15A 2B .0200 TN, TP Monthly Monitoring No changes T15A 02B .0508 Total Copper Total Zinc None Quarterly monitoring Reasonable potential to exceed the action level standards Total Mercury Total Selenium None Quarterly monitoring Reasonable potential to exceed the water quality standards Total Chromium Quarterly monitoring Eliminate monitoring No reasonable potential to exceed water quality standards REASONABLE POTENTIAL ANALYSIS: A reasonable potential analysis was performed for arsenic, chromium, copper, zinc, mercury, nickel and selenium. The analysis showed that copper, mercury, selenium and zinc present reasonable potential to exceed allowable concentrations. There is limited data for mercury and selenium and since no value is greater than the allowable limi ts, monitoring will be required to obtain enough data to perform reasonable potential at the next permit renewal. See attached RPA table for results and recommendations. INSTREAM MONITORING: The permit includes instream monitoring at three instream locations, one upstream and two downstream of the discharge. Monitoring is waived based on the permittee’s participation in the Yadkin-Pee Dee River Basin Association. PRIORITY POLLUTANT ANALYSIS: The application includes the results of three priority pollutant analyses. No priority pollutants were detected in the scan. AQUATIC TOXICITY TESTING: Permit requires chronic toxicity, ceriodaphnia dubia, 59.6%, the months of February, May, August and November. The facility passed all the test except for one test on February 2011 for which an NOV was issued. SUMMARY OF PROPOSED CHANGES: 1. Based on the results of the RPA quarterly monitoring for copper, zinc, mercury and selenium will be added to the permit. 2. A special condition for a Mercury Minimization Plan will be included in the permit. PROPOSED SCHEDULE FOR PERMIT ISSUANCE Draft Permit to Public Notice: September 10, 2013 Permit Scheduled to Issue: November 4, 2013 Fact Sheet NPDES NC0036269 Permit Renewal Page 4 NPDES DIVISION CONTACT If you have questions regarding any of the above information or on the attached permit, please contact Teresa Rodriguez at 919-807-6387. NAME: DATE: REGIONAL OFFICE COMMENTS NAME: DATE: SUPERVISOR: ____ DATE: