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Home My WebLink AboutNC0024333_Speculative Limits_20211217DocuSign Envelope ID: D791850B-0E78-43A4-AEB4-4C956A6A3901 ROY COOPER Governor ELIZABETH S. BISER Secretary S. DANIEL SMITH Director James Struve, P.E. Hazen and Sawyer 9101 Southern Pine Blvd, Ste. 250 Charlotte, North Carolina 28273 Dear Mr. Struve: NORTH CAROLINA Environmental Quality December 17, 2021 Subject: Speculative Effluent Limits Monroe WWTP NC0024333 Union County Yadkin -Pee Dee River Basin This letter provides speculative effluent limits for expanding the WWTP serving the City of Monroe located on Richardson Creek with a proposed flow of 15.4 MGD. The Division cannot provide speculative limits for the 25 MGD request due to concerns over loading to the Rocky River downstream. Limits greater than 15.4 MGD will require a site -specific calibrated model. Please recognize that any future speculative limits requests 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. Richardson Creek is located within the Yadkin -Pee Dee River Basin. Richardson 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. Richardson Creek has a summer 7Q10 flow of 1.8 cfs, a winter 7Q10 flow of 3.0 cfs, a 30Q2 flow of 4.0 cfs, and an annual average flow of 65.2 cfs. Richardson Creek is currently listed as an impaired waterbody on the 2020 North Carolina 303(d) Impaired Waters List for exceeding benthic and copper criteria. There are no specific permitting strategies or a TMDL for this stream. 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, however, there are non -aquatic threatened or endangered species in the same radius. 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 ouat\sjoll.#k" CAROLINA 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: D791850B-0E78-43A4-AEB4-4C956A6A3901 Speculative Effluent Limits. Based on Division review of receiving stream conditions and water quality modeling results, speculative limits for an expansion to 15.4 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 Limits. Assimilative capacity to protect the instream dissolved oxygen standard of 5.0 mg/L is based on a Streeter-Phelp's model and ambient monitoring station data. The resultant limits are considered technologically feasible. • Other. Modeling showed sensitivity to dissolved oxygen in the effluent, therefore the effluent limit was increased to 6 mg/L. TSS mass -loading was held constant to minimize pollutant loading to the impaired stream segments. TABLE 1. Speculative Limits for Monroe WWTP proposed expansion. Effluent Characteristic Effluent Limitations Monthly Average Weekly Average Daily Maximum Flow 15.4 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) 6.0 mg/L TSS 24.3 mg/L 36.4 mg/L TRC 17 µg/L 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 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 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: D791850B-0E78-43A4-AEB4-4C956A6A3901 above will need to be folded into the SEPA document. Additionally, if subject to SEPA, the NPDES Unit will not finalize 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, DocuSigned by: LI N AW1A1i"WW C464531431644FE... Michael Montebello Supervisor, NPDES Municipal Permitting Unit Electronic Copy: NC Wildlife Resources Commission, shannon.deaton@ncwildlif.org US Fish and Wildlife Service, sara ward@fws.gov DWR/Water Quality Regional Office/Moorseville/Corey Basinger DWR/Basinwide Planning/Jim Hawhee DWR/Modeling and Assessment Branch/Pam Behm Hazen and Sawyer: James Struve, jstuve@hazenandsawyer.com City of Monroe: Russ Colbath, rcolbath@monroenc.org NORTH Department of EmImnment.I 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