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Home My WebLink AboutNC0043176_Speculative Limits_20170228NPDES DOCUMENT !;CANNING COVER :SHEET NC0043176 Dunn WWTP NPDES Permit: Document Type: Permit Issuance Wasteload Allocation Authorization to Construct (AtC) Permit Modification Complete File - Historical Engineering Alternatives (EAA) Correspondence Owner Name Change Instream Assessment (67b) Speculative Limits Environmental Assessment (EA) Document Date: February 28, 2017 This document its printed on reuse paper -ignore any content on the re -weir -me side ROY COOPER Governor MICHAEL S. REGAN Secreran Water Resources S. JAY ZIMMERMAN ENVIRONMENTAL QUALITY Direct/or February 28, 2017 Mr. Dean Gaster Director of Public Works City of Dunn P.O. Box 1065 Dunn, North Carolina 28335 Subject: Speculative Effluent Limits Dunn WWTP Permit No. NC0043176 Harnett County Cape Fear River Basin Dear Mr. Gaster: This letter provides speculative effluent limits for a proposed 4.9 MGD discharge at the Dunn WWTP, which is currently permitted for 3.75 MGD with a discharge to the Cape Fear River. The Division received the speculative limits request in a letter dated May 16, 2016. 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 current discharge is to the middle Cape Fear River, which has a stream classification of WS-V. Waters with this classification have a best usage for water supply, aquatic life propagation and maintenance of biological integrity, wildlife, secondary recreation and agriculture. The summer 7Q10 flow is 586.6 cfs and the annual average flow is 3601 cfs. The current permitted flow of 3.75 MGD represents 1% of the low summer streamflow. The City also requested evaluation for a potential discharge to the Black River, since it is located closer to the Dunn WWTP and would be a cheaper alternative. The Black River at Dunn is classified C, Swamp. Proposed Discharge to Black River At this time the Division cannot provide speculative limits for a discharge to the Black River. If the option to discharge to the Black River is to be pursued, you must develop a nutrient response model. 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. State of North Carolina I Environmental Quality I Water Resources 1617 Mail Service Center 1 Raleigh, North Carolina 27699-1617 919 807 6300 Proposed Discharge to the middle Cape Fear River High chlorophyll -a and algae blooms are a concern in the middle Cape Fear River from Buckhorn Dam to Lock and Dam 3. The Division is in the process of developing a nutrient model for the Cape River that will include this section of the river. While the model is being developed new or expanding discharges are allowed with nutrient limits if the permittee performs a nutrient model or limits equivalent to existing loads. Speculative limits for Total Nitrogen and Total Phosphorus presented in this letter correspond to existing loads for the past 5 years. When the Division finalizes the model and develops a TMDL these limits may be modified to follow to the TMDL requirements. Speculative Effluent Limits. Based on Division review of receiving stream conditions and water quality modeling results, speculative limits for the proposed expansion to 4.9 MGD in the middle Cape Fear River are presented in Tables 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 receipt of a formal NPDES permit application. Some features of the speculative limit development include the following: • BOD/NH3 Limits. The speculative limits are based on the current permitting strategy in the Cape Fear River Basin Plan. Expanding facilities with discharges > 1 MGD are assigned BOD limit of 5 mg/1 limit and ammonia limit of 1 mg/1. • Nutrient Limits. A TMDL to address nutrient loading to the Cape Fear Estuary is projected to be completed in the future. In this interim period prior to TMDL finalization, these speculative nutrient limits are based on the following interim permitting guidance: 1) for total nitrogen (TN) and total phosphorus (TP) which have no limits in the current permit, freeze the actual TN and TP mass loads based on the historical loading from January 2012 through December 2016. The final TMDL results will ultimately override these speculative limits, and may result in more stringent nutrient requirements. As recommended in the permitting strategy the TN and TP limits are implemented as summer only (April 1 through October 31). TABLE 1. Speculative Limits for City of Dunn WWTP (Proposed Expansion to 4.9 MGD) Effluent -Characteristic 'Afftuenfi;`Luxut _., _ -. _ _ -__.. ..... , v_� _ ti _ mm on_ _ f Average - . _.i W e dy Average ,a y Maximum Flow 4.9 MGD BOD5 5 mg/L 7.5 mg/L NH3 as N 1 mg/L 3 mg/L Dissolved Oxygen Daily average >5 mg/L TSS 30 mg/ L 45 mg/ L TRC 17 ug/1 Fecal coliform (geometric mean) 200/100 ml 400/100 ml Total Nitrogen 15,243 lb/season Total Phosphorus 4,843 lb/season Chronic Toxicity Pass/Fail (Quarterly test) Pass @ 1.3 % effluent concentration 2 44, 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. 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 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, 919-807-6442) 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 Teresa Rodriguez at (919) 807-6387 or Julie Grzyb at (919) 807-6389. Respectfully, lr e Grzyb Acting Supervisor, NPDES Complex Permitting Unit Attachment EAA Guidance Document Hardcopy: Central Files NPDES Permit File Electronic Copy: vDWR/Water Quality Operations/Fayetteville Regional Office) �WR/Modeling, Pam Behm 1 WR/ Basinwide Planning, Ian McMillan ,"'DWR/NPDES Server>Specs Speculative Limits Request Notes February 24, 2017 City of Dunn — NC0043176 Received: May 16, 2016 Summary: The City of Dunn is requesting speculative limits to increase the permitted capacity from 3.75 MGD to 4.9 MGD. They would like the option to move the discharge from the Cape Fear to the Black River. Current permit conditions: Receiving stream: Cape Fear River Stream Classification: WS-V Sub -basin: 03-06-15 Stream index: 18-(20.7) Drainage Area (mi2): 3464 S7Q10 (m3/s): 586.6 Average Flow (m3/s): 3601 IWC (%): _ 1.3 Cape Fear Permitting Strategy: The existing discharge is to the Lower Middle Cape Fear River subwatershed. This subwatershed covers from Buckhorn Dam to Lock & Dam #1. The section of the river where the Dunn discharge is located is above Lock and Dam #3. Due to chlorophyll -a exceedances and nuisance algae blooms in 2005 the Division developed a permitting strategy for this section until modeling is completed and a TMDL is developed. This strategy was included in the 2005 Cape Fear Basin Plan. For expanding discharges > 1 MGD the strategy recommends limits of 5 mg/I for BOD and 1 mg/I for ammonia. For TN and TP limits the strategy recommends summer mass limits derived from freezing existing loads or developed as mass loads based on 6 mg/I TN and 1 mg/I TP. The strategy as presented in the Cape Fear Basin Plan from 2005 will be used since this is still the current Basin Plan. A draft strategy for the next Basin Plan is being developed and it requires expanding discharges to perform a nutrient calibrated model. The Modeling Unit agrees that speculative limits for TN and TP can be established based on freezing current loads for the existing discharge location but a nutrient response model will be required if the City wants to pursue the discharge to the Black River. Speculative Limits: BOD: Current permit limits are 24 mg/I monthly average and 18 mg/I weekly average during Summer and 24 mg/I monthly average and 36 weekly average during the winter. When the facility expanded from 3 MGD to 3.75 MGD the BOD limits were calculated by freezing the allowable loads based the permitted limit of 30 mg/I. Proposed limits are 5 mg/I monthly average and 7.5 mg/I weekly average. Ammonia: Current permit limits are 2 mg/I Monthly average and 6 mg/I weekly average during Summer and 4 mg/I monthly average and 12 weekly average during the winter. When the facility expanded from 3 MGD to 3.75 MGD this limits were established as BPJ since the previous permit did not include limits for ammonia. Proposed limits are 1 mg/I monthly average and 3 mg/I weekly average. Total Nitrogen: Proposed limit is the existing loads for the summer season for the past five years: 15,243 lb/season Total Phosphorus: Proposed limit is the existing loads for the summer season for the past five years: 4,843 lb/season TN and TP limits are interim until the TMDL and implementation strategy is developed. north carolina city of dunn PUBLIC WORKS DEPARTMENT I'OST OFFICE I3O\ 10h5 a 1)UN\, NORTH CAR01.1\A 28335 MO) 2311-3500 0 FA (')IO) 23(1-351)U w tiunn-ni.0rg Mr. Tom Belnick, Supervisor Division of Water Resources WQ Permitting Section - NPDES 1617 Mail Service Center Raleigh, NC 27699-1617 Dear Mr. Belnick: The City of Dunn is planni permitted capacity of 3.75 The City is preparing to e implementing a major se substantial investment in into the Cape Fear River The City has had dis discharge from th capital and operatio bark on a coral er rehabilitatio a new effluent di e Regi o th e respe and at a point on the Black River as shown on the attached exhibit. If you should have any questions or wish to meet and discuss, please do not hesitate to call. 40 �G„$I i\VItcf g for the exp May 16, 2016 Re: Speculative Limits Request City of Dunn, North Carolina NPDES Permit No. NC 0043176 DMP Project 120232 Vi0)-- 13), nsion of the Black River Wastewater Treatment Plant from its current Mayor Oscar N. Hams Mayor Pro Tem Billy Tart Council Members Buddy Maness Dr. Gwen McNeill Frank McLean Chuck Turnage Billy Barfield City Manager Ronald D. Autry GD to a capacity of 4.9 MGD. rehensive study of our WWTP and collection system with a goal of WWTP upgrade in 2017/18. Any increase in capacity would require charge system. We currently pump our effluent 3 miles to discharge RECEIVED/NCDE{, /DVVR MAY 19 2016 Water Quality Permitting Section cc: Randy McNeill, PE encl. P:1201211202321 Doc\Speculotive Limits request.docx Staff, and would like to explore the option of relocating the This option could save the City several million dollars in uest speculative limits both at our current discharge point, Sincerely, gP Dean Gaster Public Works Director ct►o -812- /9Ye CURRENT CAPE FEAR RIVER DISCHARGE LATITUDE: 35° 1T 31" N LONGITUDE: 78° 41' 09" W BUMPAS CREEK AcCESS DAVIS • MARTIN • POWELL dmp ENGINEERS 8 SURVEYORS airar O 0 DWNN, REQUESTED BLACK RIVER WASTEWATER DISCHARGE LATITUDE: 35° 17' 50" N LONGITUDE: 78° 38' 26" W 1 II �F�oo'. 1. `1 i L.- BLACK RIVER WASTEWATER TREATMENT PLANT Sou unitEsyri, DlgitalGlobe, GooEyo, Earthster Geographies. GNES/Airbus DS. USDA, USGS n!(fb'Fa co, CITY OF DUNN CAPE FEAR DISCHARGE DJNW •T�l Legend — — • Force Main - Roads - Rivers City Limits .c 7 0 650 1,300 2,600 3,900 mei Feet