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Home My WebLink AboutNC0021474_Speculative Limits_20201028ROY COOPER Governor MICHAEL S. REGAN Secretary S. DANIEL SMITH Director Dennis Hodge Water Resources Director City of Mebane 106 East Washington St. Mebane, North Carolina 27302 Dear Mr. Hodge: NORTH CAROLINA Environmental Quality October 28, 2020 Subject: Speculative Effluent Limits Mebane WWTP Permit No. NCO021474 Alamance County Cape Fear River Basin This letter provides speculative effluent limits for expansion to 3.0 and 5.3 MGD at the Mebane WWTP. The Division received the speculative limits request in a letter dated April 6, 2020 from Dennis Hodge, Water Resources Director for Mebane. 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. Moadams Creek is located within the Cape Fear River Basin. The Moadams Creek has a stream classification of WS-IV, NSW and waters with this classification have a best usage for aquatic life propagation and maintenance of biological integrity, wildlife, secondary recreation, agriculture, and as a water supply source for drinking, culinary, and food -processing purposes. The stream has a supplemental classification of nutrient sensitive water (NSW) because of downstream chlorophyll a impairment in Jordan Lake. The stream has a summer 7Q 10 flow of 0 cfs, a winter 7Q10 flow of 0 cfs, and an annual average flow of 0.9 cfs. Moadams Creek at this location is not listed on the 303(d) list of impaired waters. 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. D E Qbi�� 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 vOry rN Cx:40:.itiA � o .—Io E�.w��a�:r� /� 919.707.9000 Speculative Effluent Limits. Based on Division review of receiving stream conditions and water quality modeling results, speculative limits for the proposed expansions to 3.0 and 5.3 MGD are presented in Tables 1 and 2. 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 receipt of a formal NPDES permit application. Some features of the speculative limit development include the following: BOD/NH3 Limits. Biochemical oxygen demand (BOD) and ammonia -nitrogen limits are based on water quality modeling for the receiving stream, minimum treatment levels for streams with zero flow but with a positive 30Q2 flow [15A NCAC 2B .0206(d)(1)], and protection for ammonia toxicity. Nutrients: Total Nitrogen (TN) and Total Phosphorus (TP) mass limits are assigned according to the Jordan Lake nutrient management rules, 15A NCAC 2B .0270. The facility must demonstrate the ability to comply with these limits upon expansion or obtain additional nutrient allocation per 2B .0270. TABLE 1. Speculative Limits for Mebane WWTP (3.0 MGD) Effluent Characteristic Effluent Limitations Monthly Average Weekly Average Daily Maximum Flow 3.0 MGD OD5 5.0 mg/L 7.5 mg/L H3 as N (Apr. -Oct.) 1.0 mg/L 3.0 mg/L H3 as N (Nov. -Mar.) 1.8 mg/L 5.4 mg/L TSS 30.0 mg/L 45.0 mg/L Dissolved Oxygen Minimum Daily Average > 6.0 mg/L TRC (if used for disinfection) _F 17 µg/L TN' 40,225 lbs/ ear TP2 5,056 lbs/year Fecal coliform (geometric mean) 200/100 mL 400/100 mL Chronic Toxicity, Pass/Fail (Quarterl test) 90% Notes- 1. Equivalent to a concentration of 4.4 mg/L. 2. Equivalent to a concentration of 0.55 mg/L. TABLE 2. Speculative Limits for Mebane WWTP (5.3 MGD) Effluent Characteristic Effluent Limitations Monthly Average Weekly Average Daily Maximum Flow 5.3 MGD OD5 5.0 mg/L 7.5 mg/L H3 as N (Apr. -Oct.) 1.0 mg/L 3.0 mg/L H3 as N (Nov. -Mar.) 1.8 mg/L 5.4 mg/L Page 2 of 3 TSS 30.0 mg/L 1 45.0 mg/L Dissolved Oxygen Minimum Daily Avera e > 6.0 mg/L TRC (if used for disinfection) 17µg/L TN' 40,225 lbs/ ear TP2 5,056 lbs/year Fecal coliform (geometric mean) 200/100 mL 400/100 mL 7 Chronic Toxicity, Pass/Fail (Quarterly test) 90% Notes: 1. Equivalent to a concentration of 2.4 mg/L. 2. Equivalent to a concentration of 0.31 mg/L. Engineering Alternatives AnalysisEAA). 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 the EAA can be found at: h"s://deu.nc.Lyov/about/divisions/water-resources/water-aualitv-DennittinL/nndes- wastewater/npdes-permitting-process Should you have any questions about these speculative limits or NPDES permitting requirements, please feel free to contact David Hill at david.hillkncdenr.gov (919) 707-3612. Respectfully, DocuSigned by: Hal 2E35935DF84D4AE... David Hill Environmental Specialist II, NPDES Industrial Permitting Unit Hardcopy: NPDES Permit File Electronic Copy: NC Wildlife Resources Commission, Inland Fisheries, shannon.deaton@ncwildlife.org US Fish and Wildlife Service, Sarah_mcrae@fws.gov DWR/Water Quality Regional Operations/Winston-Salem DWRBasinwide Planning, Ian McMillan DWR/NPDES Server>Specs Page 3 of 3