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Home My WebLink AboutNC0020737_Speculative Limits_20220107DocuSign Envelope ID: 9686938F-2ABO-4656-BAD5-9E5CD43228FF ROY COOPER Governor DIONNE DELLI-GATTI Secretary S. DANIEL SMITH NORTH CAROLINA Director Environmental Quality January 7, 2022 Jeff deBessonet, P.E. Water Environment Consultants PO Box 2221 Mount Pleasant, South Carolina 29465 Subject: Speculative Effluent Limits City of Kings Mountain Cleveland County Broad River Basin Dear Mr. deBessonet: This letter provides speculative effluent limits for a new WWTP serving the City of Kings Mountain located on Dixon Branch with proposed flows of 4.0 and 6.0 MGD. A second location for the discharge was also considered for Kings Creek. These speculative limits replace those dated July 13, 2021 to incorporate total phosphorus limits recommended by the South Carolina Department of Health and Environmental Control. Please recognize that speculative limits may change based on future water quality initiatives, and it is highly recommended that the applicant verify the speculative limits with the Division's NPDES Unit prior to any engineering design work. Receiving Streams. Dixon Branch is located within the Broad River Basin. Dixon Branch has a stream classification of C, and waters with this classification have a best usage for aquatic life propagation and maintenance of biological integrity, wildlife, secondary recreation, and agriculture. Dixon Branch has a summer 7Q10 flow of 0.27 cfs, a winter 7Q10 flow of 0.49 cfs, a 30Q2 flow of 0.62 cfs, and an annual average flow of 1.58 cfs. Kings Creek is currently listed as an impaired waterbody on the 2018 North Carolina 303(d) Impaired Waters List for exceeding benthic criteria. There are no specific permitting strategies or TMDL for Kings Creek, therefore, the Division cannot permit a new discharge that may cause or contribute to an impairment and these speculative limits are for Dixon Branch only. Based upon a review of information available from the North Carolina Natural Heritage Program Online Map Viewer, there are not any Federally Listed threatened or endangered aquatic species identified within a 5-mile radius of the proposed discharge location. If there are any identified threatened/endangered species, it is recommended that the applicant discuss the proposed project with the US Fish and Wildlife Service to determine whether the proposed discharge location might impact such species. Speculative Effluent Limits. Based on Division review of receiving stream conditions and water quality modeling results, speculative limits for a proposed new facility at 4.0 MGD and 6.0 MGD are presented in Table 1. A complete evaluation of these limits and monitoring requirements for NORTH DE Department of Envlrenme„ teI Quality North Carolina Department of Environmental Quality 1 Division of Water Resources 512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617 919.707.9000 DocuSign Envelope ID: 9686938F-2ABO-4656-BAD5-9E5CD43228FF metals and other toxicants, as well as potential instream monitoring requirements, will be addressed upon receipt of a formal NPDES permit application. Some features of the speculative limit development include the following: • BOD/NH3 Limits. Assimilative capacity to protect the instream dissolved oxygen standard of 5.0 mg/L was modeled with a NC specific Streeter -Phelps model. NH3 limits are the stricter of that needed to protect instream DO and NH3 toxicity. Please note that this proposed WWTP will have an interacting discharge with the Kings Mountain Travel Plaza (NC0032867) and the combined discharges will use all available assimilative capacity for NH3 toxicity in the stream. The Division will expect connection of the Travel Plaza to the new WWTP to be evaluated in the EAA requirements discussed below. The resultant limits are considered technologically feasible. • Nutrients. To protect downstream uses, the South Carolina Department of Health and Environmental Control recommends that total phosphorus be limited to 1.0 mg/L. TABLE 1. Speculative Limits for City of Kings Mountain proposed new facility. Effluent Characteristic Effluent Limitations Monthly Average Weekly Average Daily Maximum Flow 4.0/6.0 MGD BOD5 5.0 mg/L 7.5 mg/L NH3 as N (Apr. -Oct.) 1.0 mg/L 3.0 mg/L NH3 as N (Nov. -Mar.) 1.8 mg/L 5.7 mg/L Dissolved Oxygen (minimum daily average) 6.0 mg/L Total Phosphorus 1.0 mg/L Monitor & Report (mg/1) TSS 30 mg/L 45 mg/L TRC 17 ug/1 Fecal coliform (geometric mean) 200/100 ml 400/100 ml Chronic Toxicity Pass/Fail (Quarterly test) 90% Engineering Alternatives Analysis (EAA). Please note that the Division cannot guarantee that an NPDES permit for a new or expanding discharge will be issued with these speculative limits Final decisions can only be made after the Division receives and evaluates a formal permit application for the new/expanded discharge. In accordance with North Carolina Administrative Code 15A NCAC 2H.0105(c), the most environmentally sound alternative should be selected from all reasonably cost-effective options. Therefore, as a component of all NPDES permit applications for new or expanding flow, a detailed engineering alternatives analysis (EAA) must be prepared. The EAA must justify requested flows and provide an analysis of potential wastewater treatment alternatives. EAA guidance can be found at: State Environmental Policy Act (SEPA) EA/EIS Requirements. A SEPA EA/EIS document may be required for projects that: 1) involve $10 Million or more of state funds; or 2) will significantly and permanently impact 10 or more acres of public lands. Please check with the Page 2 of 3 DocuSign Envelope ID: 9686938F-2ABO-4656-BAD5-9E5CD43228FF DWR SEPA coordinator (David Wainwright, 919-707-9045) as to whether your project requires SEPA review. For projects that are subject to SEPA, the EAA requirements discussed above will need to be folded into the SEPA document. Additionally, if subject to SEPA, the NPDES Unit will not process an NPDES permit application for a new/expanding discharge until the Division has approved the SEPA document and sent a Finding of No Significant Impact (FONSI) to the State Clearinghouse for review and comment. Should you have any questions about these speculative limits or NPDES permitting requirements, please feel free to contact David Hill at david.hill@ncdenr.gov or (919) 707- 3612. Respectfully, Michael Montebello Supervisor, NPDES Municipal Permitting Unit Electronic Copy: NC WRC, West Piedmont Coordinator, Olivia.munzer@ncwildlife.org US Fish and Wildlife Service, sara_ward@fws.gov DWR/Water Quality Regional Office/Mooresville DWR/Basinwide Planning DWR/NPDES Server>Specs SCDHEC Wade Cantrell, cantrewm@dhec.sc.gov City of Kings Mountain, rickyd@cityofkm.com Page 3 of 3