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Home My WebLink AboutNC0043532_Speculative Limits_20200127ROY COOPER Governor MICHAEL S. REGAN Secretary LINDA CULPEPPER Director Duane Wingo, PE Stanly County Utilities Director 1000 N. First Street, Suite 12 Albemarle, North Carolina 28001 Dear Mr. Wingo: NORTH CAROLINA Environmental Quality January 27, 2020 Subject: Speculative Effluent Limits West Stanly WWTP Permit No. NCO043532 Stanly County Yadkin -Pee Dee River Basin This letter provides speculative effluent limits for expansion to 2.5 MGD at the West Stanly WWTP. The Division received the speculative limits request from the County in a letter dated November 12, 2019. 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 Stream. The Rocky River is located within the Yadkin -Pee Dee River Basin. The Rocky River 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. The Rocky River has a summer 7Q 10 flow of 29 cubic feet per second (cfs), a winter 7Q 10 flow of 51 cfs, and an annual average flow of 920 cfs. The Rocky River is currently listed as an impaired waterbody on the 2018 North Carolina 303(d) Impaired Waters List for dissolved copper and turbidity. This impairment may affect future effluent limits for these parameters. 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 the proposed expansion to 2.5 MGD are presented in Table 1. A complete evaluation of these limits and monitoring requirements for North Carolina Department of Environmental Quality I Division of Water Resources 512 North Salisbury Street 1 1617 Mail Service Center I Raleigh, North Carolina 27699-1617 rror+rH cnrrour+n � 919.707.9000 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. These speculative limits are based on freezing current permitted BOD ultimate loading (i.e., facility will not be allowed to discharge oxygen -consuming waste above what is currently permitted). Requests for seasonal limits in accordance with 15A NCAC 02B .0404 will need to be supported by a QUAL2K or equivalent water quality model. The resultant limits at expanded flows are considered technologically -feasible. TABLE 1. Speculative Limits for the West Stanly WWTP Effluent Characteristic Effluent Limitations Monthly Average Weekly Average Daily Maximum Flow 2.5 MGD BOD5 5.0 mg/L 7.5 mg/L NH3 as N 1.8 mg/L 5.4 mg/L Dissolved Oxygen 5.0 mg/L Daily Minimum Average TSS 30.0 mg/L 45.0 mg/L TRC 28 µg/l Fecal coliform (geometric mean) 200/100 ml 400/100 ml Chronic Toxicity, Pass/Fail (Quarterly test) 4.6% ' Subject to change. Updated flows will be determined upon receipt of application for expansion. Engineering eering 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. A copy of the Division guidance for preparing EAA documents is attached. State Environmental Policy Act (SEPA) EA/EIS Requirements. A SEPA EA/EIS document maybe 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 Page 2 of 3 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 (919) 707-3612. Respectfully, Jlie Grzyb pervisor, NPDES Complex Permitting Unit Attachment: EAA Guidance Document Hardcopy: NPDES Permit File Electronic Copy: NC WRC, Inland Fisheries, shannon.deaton@ncwildlife.org US Fish and Wildlife Service, Sarah_mcrae@fws.gov DWR/Mooresville Regional Office/Water Quality Regional Operations/Corey Basinger DWR/Modeling and Assessment Branch/Pam Behm DWR/Basinwide Planning/ Ian McMillan DWR/NPDES Server>Specs Page 3 of 3