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HomeMy WebLinkAboutNC0001422_Modification_20200121 DUKE L V. Sutton Energy Complex 801 Sutton Steam Plant Rd `, ENERGY® Wilmington, NC 28401 PROGR i. - o:910 341 4750 f 910 341 4790 January 21,2020 RECEIVED JAN 2 7 2020 Ms.Julie Grzyb NC Division of Water Resources NCDEQ/DWR/NPDES 1617 Mail Service Center Raleigh,NC 27699-1617 Subject: Duke Energy Progress, LLC. L.V. Sutton Energy Complex NPDES Permit NC0001422 NPDES Permit Modification Request Dear Ms. Grzyb: This letter and the attached materials are provided in support of Duke Energy Progress, LLC's(Duke Energy)request to modify the L.V. Sutton NPDES permit. Duke Energy requests the following modifications be made to the permit to reflect updated operating conditions and/or align the terms with other Duke Energy permits for similar activities: 1. Duke Energy requests modified permit limits at outfall 001 based on the enclosed CORMIX model demonstration undertaken in accordance with permit condition A(22). Condition A (22) of the subject permit provides that"The permittee may elect to conduct a water quality model of the dilution factor for Outfall 001. Contingent upon EPA approval of the Lower Cape Fear Modeling and its results, the Reasonable Potential Analysis will be conducted again and the permit limits will be based on the new flow numbers established by the model." Duke Energy contracted Geosyntec to develop a water quality model of the dilution factor for Outfall 001 for revising the WQBELs. Geosyntec completed the development of a mixing zone model to simulate the dilution of constituents of concern in the Cape Fear River due to discharge from Outfall 001. Duke Energy presented a draft report to document the data, model inputs, assumptions, and results for both the EFDC model and the CORMIX model to NCDEQ during a meeting on October 10, 2018. The final CORMIX dilution model is included with this submittal as Attachment 1. 2. Duke Energy requests extension of the compliance schedule for copper at outfall 008 to perform water effects ratio(WER)study Condition A(29) of the subject permit provides a compliance schedule for copper and nickel at outfall 008. Duke Energy requests an additional 2 years for compliance with copper at outfall 008. The required copper and nickel evaluation study plan was submitted to DEQ in July of 2018, as well as two required progress reports describing the findings of the evaluation study. L.V. Sutton Electric Plant NPDES Permit NC0001422 NPDES Modification Request The evaluation and progress reports failed to find any current source of copper from the plant. However,the former coal generating unit which operated at the Sutton Plant from the 1950s until 2013 utilized condenser tubes made in part from copper. These tubes were in contact with the recirculated cooling water and were the primary source of copper in the wastewater. The natural gas combined cycle plant, brought online with the retirement of the coal units, uses titanium condenser tubes. It is likely that existing copper in the cooling pond is due to legacy coal operations making short term reductions challenging. Duke Energy is undertaking a WER study in accordance with a plan to be approved by the Divisions Aquatic Toxicity Unit. This demonstration is anticipated to be successful but will likely take beyond the existing compliance date of October 1, 2020. The nickel permit limit at outfall 001 was based on two data points that were above the water quality standard. Since the permit effective date, nickel has been non-detect or below the water quality standard. Duke Energy believes compliance with the nickel limit should not be an issue. 3. Duke Energy requests the addition of wastewater flows from LOLA excavation to outfall 001. The excavation of CCR materials in the lay of land area(LOLA) area is currently underway. As this area is excavated, groundwater and ash contact water are filling the area left void by the excavation. This area is currently segregated from other areas via sheet pile walls. Duke Energy requests that future wastewater discharge from the LOLA be added as a contributory source to outfall 001. The characteristics of the wastewater from this area would be consistent with historic ash pond dewatering discharges from the 1984 and 1971 basins. A map identifying the location of the LOLA area is included at Attachment 2. 4. Duke Energy requests toxicity monitoring return to a quarterly frequency at outfall 001. Since the permit effective date, the L.V. Sutton Energy complex has conducted acute toxicity testing monthly. The testing has shown no significant acute mortality at a concentration of 90% in all 26 samples. Quarterly toxicity testing would more than sufficient to determine any aggregate toxic effect on aquatic organisms from the outfall 001 discharge. 5. Duke Energy requests the language in the footnote related to the use of physical-chemical treatment at outfall 001 be aligned with other Duke Energy permits language. 6. Duke Energy requests removal of internal outfalls 005,006,007,and 009. Duke Energy requests removal of NPDES permit coverage from internal outfalls 005, 006, 007, and 009. Flows from these outfalls are composed of wastewater from the combined and simple cycle units and some stormwater runoff. The flows themselves do not consist of a categorical flow that must meet certain limits prior to commingling. Additionally,the flows L. V. Sutton Electric Plant NPDES Permit NC0001422 NPDES Modification Request contribute to the aggregate discharge at outfall 008 to Sutton lake have the same permit limits as all of the internal outfalls. The discharge of these outfalls is to the effluent channel and then to Sutton Lake via outfall 008. The monitoring requirements for outfall 008 are protective of surface water quality and adequate to characterize the discharge to Sutton Lake from these minor internal sources. A map of the outfall locations is included as Attachment 3. 7. Remove NPDES coverage for ash basin outfalls 002 and 004. Duke Energy requests the removal of NPDES permit coverage from outfalls 002 and 004. These outfalls are from the now excavated 1971 and 1984 ash basins. The basins no longer have an outfall structure or mechanism to discharge to Sutton Lake,with the 1984 basin being dry. Duke Energy proposes, upon approval of this modification,to discharge the remaining wastewater in the 1971 basin via outfall 001. Thank you for your consideration of the above-requested items. If there are any questions, please contact either: • Ms. Lori Tollie, Environmental Specialist, at(336)854-4916 or email Lori.Tollie@duke- energy.com, or • Mr. Kent Tyndall, Environmental Professional for the L. V. Sutton Energy Complex Plant;phone (910)341-4775 or e-mail Kent.Tyndall@duke-energy.com. I certify, under penalty of law, that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility offines and imprisonment for knowing violations. Sincerely, on Talbot Station Manager Enclosures Attachment 1 - CORMIX Model • Prepared for: eirak, DUKE '-‘,-" v ENERGY® PROGRESS Duke Energy Progress, LLC 526 South Church Street Charlotte, North Carolina 28202 MIXING ZONE ANALYSIS, Addendum L.V. SUTTON ENERGY COMPLEX 801 Sutton Steam Plant Road Wilmington, North Carolina Prepared by: Geosyntec° consultants I totinlrC Cun.oltunts DINE,Pl Geosyntec Consultants of NC, PC 1300 South Mint Street Suite 300 Charlotte, North Carolina 28203 License No. C-295 Project No. GC6463 January 2020 L.V.Sutton Energy Complex Mixing Zone Analysis Geosyntec° consultants TABLE OF CONTENTS 1. INTRODUCTION 1 2. MIXING ZONE METHODOLOGY 2 2.1 CORMIX Model Inputs 2 2.1.1 Discharge Characterization 2 2.1.2 Outlet Structure Configuration 2 3. MODEL RESULTS 3 3.1 Embayment Model 3 3.2 River Model 3 4. REVISED PERMIT LIMITS 5 LIST OF TABLES Table 1: Updated Embayment Model Inputs with Effluent Flow of 0.35 MGD 7 Table 2: Updated Embayment Model Inputs with Effluent Flow of 3.5 MGD .7 Table 3: Updated Inputs for CORMIX River Model with Effluent Flow of 0.35 MGD 8 Table 4: Updated Inputs for CORMIX River Model with Effluent Flow of 3.5 MGD .8 Table 5: Current and Revised Effluent Limits for Outfall 001 at L.V. Sutton Energy Complex 9 LIST OF FIGURES Figure 1: Simulated Dilution of Outfall 001 Effluent in the Embayment for the Maximum Stratification Scenario with 0.35 MGD Discharge 11 Figure 2: Simulated Dilution of Outfall 001 Effluent in the Embayment for the Maximum Stratification Scenario with 3.5 MGD Discharge 12 Figure 3: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for the Maximum Stratification Scenario with 0.35 MGD Discharge 13 Figure 4: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for the Maximum Stratification Scenario with 3.5 MGD Discharge 13 Figure 5: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for the Three Scenarios with 0.35 MGD Discharge 14 Figure 6: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for Maximum Stratification with 3.5 MGD Discharge 15 GC6462/2020(0114)_SuttonMixingZoneAnalysis 1 January 2020 L.V Sutton Energy Complex Mixing Zone Analysis Geosyntec consultants 1. INTRODUCTION Geosyntec Consultants of North Carolina, PC (Geosyntec) has prepared this report addendum to document the updated results of a mixing zone study completed on behalf of Duke Energy Progress, LLC (DEP). The L.V. Sutton Energy Complex(Sutton or Site) is currently permitted to discharge into Lower Cape Fear River (LCFR) through Outfall 001 under National Pollutant Discharge Elimination System(NPDES) Discharge Permit No.NC0001422 (NCDEQ, 2017). This report serves as an addendum to the original report submitted in February 2019 to address feedback from the North Carolina Department of Environmental Quality (NCDEQ) to update the effluent flow from Outfall 001 to 0.35 million gallon per day (MGD) or the current representative flow from Outfall 001. In addition, the report includes modeling of the revised configuration for Outfall 001 as a 12"pipe which was constructed in 2019. DEP also requested an additional model run to account for potential future discharge increase to 3.5 MGD. The following sections discuss the data review and analysis to develop the Cornell Mixing Zone Model (CORMIX)model inputs to account for both NCDEQ and DEP requests. GC6462/2020(0114)_SuttonMixingZoneAnalysis 1 January 2020 L.V.Sutton Energy Complex p Mixing Zone Analysis Geosyntec consultants 2. MIXING ZONE METHODOLOGY Geosyntec conducted a mixing zone study to simulate the dispersion of the discharge plume from Outfall 001 in the LCFR under three scenarios for the 0.35 MGD discharge including: maximum stratification,minimum stratification,and off-site design scenarios.The scenarios are described in detail in the main report (Geosyntec 2019). The most conservative scenario (maximum stratification) was used to simulate the increased effluent flow of 3.5 MGD. 2.1 CORMIX Model Inputs Available outfall configuration, receiving water, and discharge characteristics data were used as inputs to the CORMIX model to simulate dilution of the discharge plume from Outfall 001 into the LCFR. Outfall 001 discharges into a small embayment which then enters the LCFR(Figure 10 in the main report). As discussed in the main report, CORMIX modeling was completed in two steps for the embayment model and the river model. Receiving water characteristics input data were kept consistent with the approach in the main report. Input data for discharge characteristics and outfall configuration for Outfall 001 was updated in the embayment model and the river model. Table 1 and Table 2 summarize the input for the embayment model,while Table 3 and Table 4 summarizes inputs for the river model. The following sections document the input data updates. 2.1.1 Discharge Characterization The mixing zone model needs to include the effluent characteristics such as flow rate,temperature, and concentration to simulate the effluent plume in the river. In this application, the discharge input parameters were kept consistent with the approach in the main report except effluent flow. As recommended by the NCDEQ, the average effluent flow of 0.35 MGD between August 2016 and October 2019 was used as an input into the CORMIX model. An additional model run with 3.5 MGD was done using the maximum stratification scenario to account for a future discharge increase from 1971 Basin. This increased effluent discharge number was based on the discussions between DEP and NCDEQ staff. 2.1.2 Outlet Structure Configuration CORMIX requires specification of pipe outfall diameter and its distance from the nearest bank (shoreline).DEP has completed the separation of Cooling Pond water discharge from Lake Sutton and the coal combustion residuals (CCR)basin wastewater, as per the requirement in the NPDES Permit NC0001422 dated December 2015. The CCR basin wastewater now discharges through a 12"pipe directly into the embayment of the LCFR. Outfall 001 was modeled as a 12"pipe located 10 feet away from embayment shoreline. The pipe height above the stream bed for each scenario was estimated based on the design drawings and the water depth of each scenario (Tables 1 and 2). GC6462/2020(0114)_SuttonMixingZoneAnalysis 2 January 2020 L.V.Sutton Energy Complex Mixing Zone Analysis Geosyntec consultants 3. MODEL RESULTS The embayment model and river model were used to simulate the mixing of the discharge from Outfall 001 in the embayment and the LCFR respectively. The following sections discuss the results of the CORMIX model simulations. 3.1 Embayment Model The first step in the CORMIX modeling simulated the effluent plume discharge directly from Outfall 001 into the embayment for three scenarios described in the main report using the 0.35 MGD discharge. Among the three scenarios at 0.35 MGD, the maximum stratification scenario resulted in minimum dilution of the effluent(Table 3). The most critical condition is therefore the maximum stratification scenario. The description of the results is therefore focused on the maximum stratification scenario. A three-dimensional (3-D) representation of the simulated dilution in the embayment for the maximum stratification scenario using the 0.35 MGD discharge is shown in Figure 1. The plume is dominated by the momentum of the effluent in the embayment and it attaches to the surface. The simulated centerline dilution at the edge of embayment located at 30 m, is 12.9. The width of plume is about 16.08 m.The plume extends up to 0.25 meters(m)below the water surface. Figure 2 shows a 3-D representation of the simulated dilution in the embayment for the maximum stratification scenario using the 3.5 MGD discharge. The plume is also dominated by the momentum of the effluent in the embayment and it is attached to the surface. The simulated centerline dilution at the edge of the embayment (30 m downstream of the outfall) is 14.6. The width of the plume is about 4.8 m. The plume extends up to 2.4 m below the water surface. The results of the 0.35 MGD and 3.5 MGD embayment models were used as inputs into the corresponding river model. 3.2 River Model The second step in the CORMIX modeling simulated the effluent plume discharge from embayment into the LCFR for the three scenarios described above.Among the three scenarios,the maximum stratification resulted in minimum dilution of effluent. A 3-D representation of the simulated dilution in the LCFR for the maximum stratification scenario using the 0.35 MGD discharge is shown in Figure 3. The effluent plume from the embayment into the LCFR has very little momentum and therefore quickly attaches to the river bank. A 3-D representation of the simulated dilution in the LCFR for the maximum stratification scenario using the 3.5 MGD discharge is shown in Figure 4. The effluent plume from the embayment into the LCFR for this scenario also has very little momentum and therefore quickly attaches to the river bank. Figure 5 presents the simulated dilution of the Outfall 001 effluent at 0.35 MGD under three scenarios in the LCFR. The simulated dilution at 50 m from Outfall 001 in the LCFR for the maximum stratification scenario is 104.7. GC6462/2020(0114)_SuttonMixingZoneAnalysis 3 January 2020 L.V.Sutton Energy Complex Mixing Zone Analysis Geosyntec consultants The river model was also run for the potential future discharge of 3.5 MGD using the maximum stratification scenario. The simulated dilution at 50 m from Outfall 001 in the LCFR is 115.3 (Figure 6). The simulated dilution factor was used to calculate revised permit limits for Outfall 001. GC6462/2020(0114)_SuttonMixingZoneAnalysis 4 January 2020 L.1!Sutton Energy Complex Mixing Zone Analysis Geosyntec consultants 4. REVISED PERMIT LIMITS The permit limits for Outfall 001 were recalculated based on the simulated dilution factor of 115.3 (3.5 MGD) at 50 m from Outfall 001. Table 5 presents the current limits (which assume no dilution)and revised permit limits based on the most conservative mixing zone scenario. GC6462/2020(0114)_SuttonMixingZoneAnalysis 5 January 2020 TABLES Table 1: Updated Embayment Model Inputs with Effluent Flow of 0.35 MGD Maximum Minimum Offsite Description Units Source Stratification Stratification Design Discharge Geometry: Plume Dimensions Pipe diameter 12 12 12 in DEP Above or below water surface Below Below Below m Design drawings Height of pipe above water surface 5.7 5.9 6.3 m Design drawings Distance of pipe from bank 10 10 10 ft Design drawings Discharge Flow: Plume Discharge from Embayment Flow rate 0.35 0.35 0.35 MGD NCDEQ request for 0.35 MGD Table 2: Updated Embayment Model Inputs with Effluent Flow of 3.5 MGD Description Maximum Units Source Stratification Discharge Geometry: Plume Dimensions Pipe diameter 12 in DEP Above or below water surface Below m Design drawings Height of pipe above water 5.7 m Design drawings surface Distance of pipe from bank 10 ft Design drawings Discharge Flow: Plume Discharge from Embayment Flow rate 3.5 MGD DEP request for 3.5 MGD Table 3: Updated Inputs for CORMIX River Model with Effluent Flow of 0.35 MGD Description Maximum Minimum Offsite Units Source Stratification Stratification Design Discharge Geometry: Plume Dimensions Plume width 8.97 12.44 12.56 m Embayment model Depth of discharge channel 0.44 2.95 3.05 m Embayment model Discharge Flow: Plume Discharge from Embayment Flow rate 7.33 70.93 74.14 MGD Calculated equivalent mixing flow Predicted discharge Concentration 7.78 0.835 0.80 % excess at the edge of embayment Table 4: Updated Inputs for CORMIX River Model with Effluent Flow of 3.5 MGD Description Maximum Units Source Stratification Discharge Geometry: Plume Dimensions Plume width 4.78 m Embayment model Depth of discharge channel 2.39 m Embayment model Discharge Flow: Plume Discharge from Embayment Flow rate 8.33 MGD Calculated equivalent mixing flow Predicted discharge Concentration 6.83 % excess at the edge of embayment Table 5: Current and Revised Effluent Limits for Outfall 001 at L.V. Sutton Energy Complex Revised Limit Current Limits (3.5 MGD) Parameter Monthly Daily Monthly Daily Limit Limit Limit Limit Total Mercury(ug/L) 47 47 5,421 5,421 Total Arsenic(ug/L) 10 50 1,153 5,767 Total Selenium(ug/L) 5 56 577 6,459 Total Iron(mg//L) 1 1 115 115 Total Lead(ug/L) 25 33.8 2,884 3,898 Total Cadmium(ug/L) 2 15 231 1,730 SJ?If1DIJ Dilution S 1.0 2.2 5.0 )l.2 25.0 56.0 125.2 280.0 r u 10'lz -2 -4 x 5 0 Figure 1: Simulated Dilution of Outfall 001 Effluent in the Embayment for the Maximum Stratification Scenario with 0.35 MGD Discharge Dilution S 1 0 1 3 2.2 3 3 4 9 74 11 0 rd..) 24.3 30.3 54.0 ea5 120 0 2 Nc \-2 X -3� 2 Figure 2: Simulated Dilution of Outfall 001 Effluent in the Embayment for the Maximum Stratification Scenario with 3.5 MGD Discharge Dilution S 5 1.0 1.3 1.8 2.3 3.1 4.1 5.4 7.1 9.5 12.5 16.6 22.0 MEW -11111=11111111111111 5 44 1j, � 111111111111. 01111101111 UA -20 to Figure 3: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for the Maximum Stratification Scenario with 0.35 MGD Discharge Dilution S 1.0 1.4 2.1 3.0 4.3 6.2 8.9 12.8 18.4 26.5 38.2 55.0 UMW """Milli 1 -5 Figure 4: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for the Maximum Stratification Scenario with 3.5 MGD Discharge 700 ; r .. 600 r 500 r r 0 400 .`%ra - - LL 0 300 o i 200 5 = 104.7 30 35 40 45 50 55 60 65 70 75 80 Distance Downstream(m) Max Stratification — — —Min Stratification Off Site Design Figure 5: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for the Three Scenarios with 0.35 MGD Discharge 200 180 160 140 { .� S = 115.3 "00" 120 rts LL c 100 0 80 60 • 40 / 20 ! 0 E.*a 30 35 40 45 50 55 60 65 70 75 80 Distance Downstream(m) Figure 6: Simulated Dilution of Outfall 001 Effluent in the Lower Cape Fear River for Maximum Stratification with 3.5 MGD Discharge Attachment 2 -Lay of Land Area/ FADA- -,-, ,',.,,„4,f-7.;s4 _ "+ C R 1�C 218 uu * L S .. ,yam.___ 'l F,- e - 4. '. �= u . 197t 4uuw ASH BASIN' , CCR-122E wl4. ti fi 6 v� {t i 9: gal A �t ,rt . GW PZ-4WB 'ABAAYIA Nam} , --_ / t1 lAs _' V" CCR-107B e .` CCR-1066 wt ti: . TW- , d tigRcc 4. WI-1319 ; ;MW-13 R/MW-13R-D `4 4 „ cS " .e - .� .�. lti kd x t � MW-47BIC MW-4861C 4. .%i.jTW-L098 ,. ABMW-02/S/D u� COOLING POND (SUTTON LAKE) 4. ,a A froilA n.: TW-1024 FORMER AST ; MW-15R MW-46B/C L.V. Sutton Electric Plant NPDES Permit NC0001422 NPDES Modification Request Attachment 3 N 17(....."-° , ,i4.e 0 500 1000 c .......4 Makeup ' Meters I Pump 0 1000 2000 3000 i I a a Pe i 6 0 Outfa 1100 m' Sutton Cooling Pond New Ash Pond I (1984) 11' 00utfa11002 Outfall008(approx) Old Ash Pond(1971) 1 EffMa+ntCha*e toCavq�gFa�a CNN\ tst na ♦� Ii ; utt i,.9 Inte a new) C3trt/at mow;' i • final (external)Outfalls — — Cooling Pond • Internal Outfalls Wi hdrawal Recircu latin g Condenser 4 Cooling Water Outfal1001 Release CC Slack aiternal fluffed'006— f CC Block r Su nerg, InternalOutfali005 [ .. r'' ` • NORTH CAROLtIA Attachment 3- Site Map L.V. Sutton Energy Complex New Hanover County