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Home My WebLink AboutNC0026441_Speculative Limits_20211210DocuSign Envelope ID: 89DD9E16-4D1 C-431 D-B97B-602931 B3912E ROY COOPER Governor ELIZABETH S. BISER Secretary S. DANIEL SMITH Director David Honeycutt, P.E. McGill Associates, PA 5 Regional Circle, Suite A Pinehurst, North Carolina 28734 Dear Mr. Honeycutt: NORTH CAROLINA Environmental Quality December 10, 2021 Subject: Speculative Effluent Limits Siler City WWTP NC0026441 Chatham County Cape Fear River Basin This letter provides speculative effluent limits for expanding the WWTP serving Siler City located on Loves Creek with a proposed flow of 6.0 MGD. These speculative limits replace the September 17, 2021 speculative limits to incorporate changes made at the request of the City to increase the weekly average limit for organic nitrogen and corrects an error in seasonal loading. Please recognize that any future speculative limits requests may change based on future water quality initiatives. Receiving Streams. Loves Creek is located within the Cape Fear River Basin. Loves Creek 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. Loves Creek has a summer 7Q10 flow of 0.0 cfs, a winter 7Q10 flow of 0.23 cfs, a 30Q2 flow of 0.32 cfs, and an annual average flow of 7.4 cfs. Loves Creek is currently listed as an impaired waterbody on the 2020 North Carolina 303(d) Impaired Waters List for exceeding benthic criteria. There are no specific permitting strategies or TMDL for this stream. Loves Creek is also part of the Middle Cape Fear River Basin, many segments of which suffer from Chlorophyll -a impairment due to excess nutrients. Nutrient criteria development and modeling are currently underway to address these impairments and may affect future permit limits. Based upon a review of information available from the North Carolina Natural Heritage Program Online Map Viewer, there are 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. NORTH 1:tE nepertment of Environmental CAROLINA ouat� North Carolina Department of Environmental Quality Division of Water Resources 512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617 919.707.9000 DocuSign Envelope ID: 89DD9E16-4D1 C-431 D-B97B-60293183912E Speculative Effluent Limits. Based on Division review of receiving stream conditions and prior water quality modeling results, speculative limits for an expansion to 6.0 MGD are presented in Table 1. A complete evaluation of these limits and monitoring requirements for metals and other toxicants, as well as potential instream monitoring requirements, will be addressed upon review of the formal NPDES permit application which is under review. Some features of the speculative limit development include the following: • BOD/NH3/TSS Limits. Assimilative capacity to protect the instream dissolved oxygen standard of 5.0 mg/L is based on prior stream modeling which showed that the receiving stream's dissolved oxygen is sensitive to organic nitrogen. Seasonal BOD limits from the prior speculative limits were dropped to comply with 15A NCAC 2B .0404. The resultant limits are considered technologically feasible. • Total Nitrogen Load Limits. The annual load is based on the June 2020 Settlement Agreement between Siler City, the Division, and the Rocky River Watch based on a treatment level of 3.0 mg/L of Total Nitrogen to protect the Rocky River watershed and Middle Cape Fear River Basin from Chlorophyll -a impacts. Please note that there is nutrient criteria development and modeling of the basin which may result in stricter limits than those found in Table 1 (at some time in the future). TABLE 1. Speculative Limits for Siler City WWTP proposed expansion. Effluent Characteristic Effluent Limitations Monthly Average Weekly Average Daily Maximum Flow 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 5.4 mg/L Dissolved Oxygen (minimum daily average) 7.0 mg/L Organic Nitrogen (Apr. -Oct.) 3.0 mg/L 4.5 mg/L Total Phosphorus (Apr -Sept.) 0.5 mg/L (quarterly average) Total Phosphorus (Oct -Mar.) 2.0 mg/L (quarterly average) Total Nitrogen Load 54,800 lbs/year 1 TSS 20 mg/L 30 mg/L TRC 17 µg/L Fecal coliform (geometric mean) 200/100 mL 400/100 mL Chronic Toxicity Pass/Fail (Quarterly test) 90% 1. Equivalent to a 3.0 mg/L concentration (on an Annual basis). Monitor and report pounds per month. 2. The total phosphorus requirements will be consistent with the existing permit. NORTH Department of Esmlmnmontel Wally North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617 919.707.9000 DocuSign Envelope ID: 89DD9E16-4D1C-431D-B97B-602931B3912E 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 evaluates the formal permit application for the 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 (in this case we have this information which is under review). The EAA must justify requested flows and provide an analysis of potential wastewater treatment alternatives. 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 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 accept 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, rlAADoo'ccuSiign''ed by: ka`1. �'e.'' ` C464531431644FE... Michael Montebello Supervisor, NPDES Municipal Permitting Unit Electronic Copy: NC WRC, Eastern Piedmont Coordinator, gabriela.garrison@ncwildlife.org US Fish and Wildlife Service, sara_ward@fws.gov DWR/Water Quality Regional Office/Raleigh/Scott Vinson DWR/Basinwide Planning/Nora Deamer DWR/Modeling and Assessment Branch/Pam Behm Siler City: Roy Lynch (rlynch@silercity.org), Chris McCorquodale (cmccorquodale@silercity.org) SELC: Blakely Hildebrand (bhildebrand@selcnc.org) , Jean Zhuang (jzhuang@selc.org) NORTH Department of Esmlmnmontel Wally North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617 919.707.9000