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HomeMy WebLinkAboutNC0004979_Allen_Appendix G_20191231Corrective Action Plan Update December 2019 Duke Energy Carolinas, LLC - Allen Steam Station APPENDIX G SynTerra UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT FOR ALLEN STEAM STATION BELMONT, NC DECEMBER 2019 PREPARED FOR DUDE ENERGY. CAROLINAS DUKE ENERGY CAROLINAS, LLC INVESTIGATORS LAWRENCE C. MURDOCH, PH.D. - FRX PARTNERS JOHNATHAN F. EBENHACK, M.S. - SYNTERRA CORPORATION BONG YU, PH. D. - SYNTERRA CORPORATION REGINA GRAZIANO, M.S. - SYNTERRA CORPORATION RONALD W. FALTA, PH.D. - FALTA ENVIRONMENTAL, LLC Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina EXECUTIVE SUMMARY This groundwater flow and transport model report provides basic model development information and simulations of basin closure designs as well as results of corrective action simulations for the Allen Steam Station (Allen, Site, Station). The Site is owned and operated by Duke Energy Carolinas, LLC (Duke Energy) and is located near (south of) Belmont, Gaston County, North Carolina. Model simulations were developed using flow and transport models MODFLOW and MT3DMS. Due to historical ash management and wastewater discharge activities at the Site, a numerical model was developed to evaluate transport of inorganic constituents of interest (COIs) in the vicinity of the ash basins. Numerical simulations of groundwater flow and transport have been calibrated to pre -decanting conditions and used to evaluate different scenarios being considered as options for closure of the ash basins. The simulations were also used to design a corrective action system that would achieve compliance with North Carolina Administrative Code, Title 15A, Subchapter 02L, Groundwater Classification and Standards (02L) by the end of year 2029. This model and report is an update of a previous model developed by SynTerra in conjunction with Falta Environmental, LLC and Frx Partners (SynTerra, 2018b). The Site encompasses 1009 acres on the west bank of Lake Wylie, a portion of the impounded Catawba River. Duke Energy also owns property along the discharge canal to the east and west of South Point Rd (NC Highway 273). In addition to the power station property, Duke Energy also owns and operates the Catawba-Wateree Project [Federal Energy Regulatory Commission (FERC) Project No. 2232]. The Station is a five -unit coal-fired electricity -generating facility with a capacity of 1,155 megawatts (MW). Commercial operations at the Station began in 1957. Coal combustion residuals (CCRs) have historically been managed at ash basins located within two natural drainages impounded in part by earthen embankments south of the Station. The Active Ash Basin (AAB), the southernmost ash basin, is approximately 169 acres and contains some free water. Mechanical decanting began in June 2019 to remove the free water in the AAB. The Inactive Ash Basin, also referred to as the Retired Ash Basin (RAB), covers approximately 132 acres and has been inactive since 1973. It is north of the AAB. Two ash storage areas, two structural fill areas, and a double -lined ash landfill were constructed within the waste boundary of the RAB. Groundwater at the Site generally flows from west to east toward Lake Wylie. Discharge from the AAB is currently permitted by the North Carolina Department of Environmental Quality (NCDEQ) Division of Water Resources (DWR) under National Pollutant Discharge Elimination System (NPDES) Permit NC0004979. Duke Energy operates the on -site Industrial Landfill (RAB Ash Landfill) in accordance with the NCDEQ Solid Waste Section (SWS) Page ES-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina under Permit 3612-INDUS-2008. Coal has been stored north and northeast of the RAB within two separate piles, the main coal pile and the live coal pile. Collectively, the coal piles are referred to as the "coal pile area". The coal pile area is downgradient of the RAB. The predictive simulations presented herein related to closure and corrective action are not intended to represent final detailed closure or corrective action designs. These simulations use current closure designs developed by AECOM and are subject to change as the closure plans are finalized (AECOM 2019a,b). The simulations are intended to show the key characteristics of groundwater flow and mobile constituent transport that are expected to result from the closure actions and corrective actions. Completion dates for each of the closure options in the groundwater simulations are based on estimates provided by AECOM. As closure activities proceed, these dates are subject to change. Based on preliminary modeling (SynTerra, 2018b), variance in the start dates and completion dates of the closure does not produce significant changes in the results of the simulations. Boron, sulfate, and total dissolved solids (TDS) were the COIs selected to evaluate performance of the closure actions and corrective actions. These constituents are present beyond the compliance boundary and exhibit plume characteristics. These COIs are relatively unreactive with subsurface solids and are readily transported and therefore are a reasonable indicator of the maximum extent of COIs transported in groundwater derived from the ash basins and/or the coal pile area. Transport of less mobile constituents (i.e., arsenic, selenium) are controlled by chemical reactions affecting sorption and are not within the scope of this report. The calibrated model was adjusted to represent conditions that would occur during two closure scenarios. Closure -by -excavation involves excavating ash and placing it in an on -site landfill, and closure -in -place involves grading and covering the ash with a low permeability cap. Closure -by -excavation is designed to be complete by year 2042 and closure -in -place is designed to be complete in 2029. Model simulations were conducted to predict approximately 500 years into the future, and the results describing the distribution of COI concentrations (Figure ES-1a through Figure ES-1c) were used to evaluate the performance of the two closure scenarios. Corrective action simulations were used to design a system of pumping and low-pressure injection wells that could achieve 02L compliance by the end of 2029. The compliance boundary used to evaluate the performance of the two closure scenarios as well as the corrective action simulation is established by 15A NCAC 02L .0107 as 500 feet from the waste boundary or at the property boundary, whichever is closer to the source. Page ES-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina The current distribution of boron in the saprolite, transition zone, and bedrock adjacent to the ash basins resulted from hydrologic and mass loading conditions during operation of the ash basins. These conditions will change as the AAB is decanted, and as ash is regraded, removed, or covered during closure construction. Decanting will consist of removal of free water within the AAB to within 3 feet of the ash surface. These changes are predicted to cause the hydraulic head to drop by almost 50 feet, and the inferred groundwater flow direction to shift more strongly to the east toward Lake Wylie. Saprolite is relatively thick at the Site and the maximum extent of COIs is typically greater in the saprolite and transition zone than in the underlying bedrock. Under pre - decanting conditions, the model predicts boron at concentrations greater than the 02L standard beyond the compliance boundary along parts of the eastern boundary of the Site where groundwater under the ash basins discharges to Lake Wylie. Sulfate and TDS concentrations that are detected greater than the 02L standard beyond the compliance boundary are limited primarily to a region around the coal pile area and the Station power block. COI concentrations shown under Lake Wylie do not represent surface water concentrations in Lake Wylie (Figure ES-1a). Model simulations predict that the COI distribution will be similar under the two closure scenarios (Figure ES-1a through Figure ES-1c). Without additional corrective action beyond basin closure, the time to reach 02L compliance for sulfate and TDS is around year 2200 for both closure scenarios. The 02L standard for sulfate is 250 milligrams per liter (mg/L) and the 02L standard for TDS is 500 mg/L. The time to reach 02L compliance for boron is predicted to be longer for the closure -by -excavation scenario. The 02L standard for boron is 700 micrograms per liter (µg/L). A small patch of boron, with a maximum concentration of approximately 900 µg/L, persist just east of well cluster AB-10 until at least year 2500 under closure -by -excavation. Boron is predicted to achieve 02L compliance around year 2300 under closure -in -place. Time series plots were created at representative locations west and east of the AAB, in the coal pile area, and in the northeast corner of the RAB (Figure ES-2). Boron concentrations greater than 02L occur at Points 2 and 4 but, whereas it is less than 02L at the other points. The time to reach boron 02L compliance is shorter for closure -in -place by about 10 years at Point 4 and by 120 years at Point 2 (Figure ES-3a). Sulfate concentrations greater than 02L only occur at Point 3 for both closure scenarios and the response to decanting and closure is roughly the same for both closures (Figure ES-3b). TDS concentrations greater than 02L occur at Points 2a and 3 under both closure Page ES-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina scenarios (Figure ES-3c). At Point 4 TDS concentrations greater than 02L occur under closure -by -excavation but not under closure -in -place. Two remedial system designs for corrective action were developed using hydraulic control measures. These systems include vertical extraction wells that extend along the eastern side of the Site and around the coal pile, and low-pressure vertical and/or horizontal clean water infiltration wells located within and around the coal pile and in the footprint of the Station power block. The first remedial system, alternative 3A, consists of conventional vertical extraction wells and vertical clean water infiltration wells (Figure ES-4a). The second remedial system, alternative 3B, consists of conventional vertical extraction wells, vertical clean water infiltration wells, and horizontal clean water infiltration wells (Figure ES-4b). The difference in the two systems is that alternative 3B utilizes horizontal clean water infiltration wells below the coal pile area that are installed and operated while the coal pile is still in use and alternative 3A uses vertical clean water infiltration wells in this area that are installed and operated after the coal pile is no longer in use. The timing of the Station decommissioning process and access to areas for well installation is the reason the two options were evaluated. Both corrective action designs could be implemented in stages as safe access becomes available as Station decommissioning proceeds. The flexibility in the approach allows corrective action to be implemented prior to Station decommissioning with the full remedial systems being implemented as access becomes available during or after decommissioning. The corrective action simulations indicate that boron, TDS, and sulfate can be brought into compliance by approximately 10 years after implementing either of the two remedial systems (Figure ES-4a and Figure ES-4b). The simulations indicate that corrective action using techniques that are readily available and accepted in the environmental industry would reduce boron, sulfate, and TDS concentrations less than 02L beyond the compliance boundary before completion of closure -by -excavation and soon after completion of closure -in -place. The simulations show that the Site will come into 02L compliance with both closure scenarios, but this will require several centuries in the absence of corrective actions. These long times are controlled by the slow transport under hydrologic conditions following closure. However, corrective actions using hydraulic control can rapidly recover COIs and markedly shorten the time required to reach compliance to approximately one decade after implementing corrective action. Page ES-4 LOSURE BY XCAVATION, YEARS AFTER CLOSURE ` r• 1 YEARS AFTER CLOSURE CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE .lord ( DUKE CALER 1,250 GOAPHICS1,2 0 2,500 ENERGY. >L11VA5 N FEET, LEGEND � � � ASH BASIN COMPLIANCE ' DRAWN BY: J. R. KIEKHCK DATE: 12/20/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 BOUNDARY � APPROVED BY: L. DRAGO DATE: 12/20/2019 BORON > 700 ug/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN ASH ' LANDFILL COMPLIANCE BOUNDARY RETIRED ASH BASIN WASTE Terra CHECKED BY: L. DRAGO DATE:12/20/2019 PROJECT MANAGER: C. SUTTELL www.synterracorD.com FIGURE ES -la COMPARISON OF SIMULATED BORON ' BOUNDARY NOTES: ALL BOUNDARIES AREAPPROXIMATE. CONCENTRATIONS IN ALL NON -ASH LAYERS SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS MODELING REPORT COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION SYSTEMIFIPS320BEEN SET 0(NAD83) WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE BELMONT, NORTH CAROLINA LOSURE BY XCAVATION, YEARS AFTER CLOSURE ` r•lw LEGEND ASH BASIN COMPLIANCE BOUNDARY SULFATE > 250 ug/L RETIRED ASH BASIN ASH LANDFILL COMPLIANCE ACTIVE ASH BASIN WASTE BOUNDARY BOUNDARY RETIRED ASH BASIN WASTE - BOUNDARY I YEARS AFTER CLOSURE CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE NOTES: ALL BOUNDARIES ARE APPROXIMATE. SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). (ALE DUKE 1,300 GORAPHICSC1,300 2,600 ENERGY. (IN FEET, >uIVAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 APPROVED BY: L. DRAGO DATE: 12/20/2019 CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerid PROJECT MANAGER: C. SUTTELL www.s nterracor .com FIGURE ES -lb COMPARISON OF SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LOSURE BY XCAVATION, YEARS AFTER CLOSU VW' 1 YEARS AFTER CLOSURE CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE _ 'yip-/r� R .► CALEm- ( DUKE 1,250 GOAPHICS1,2 0 2,500 ENERGY. N FEET, >L11VA5 LEGEND ASH BASIN COMPLIANCE DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 ' BOUNDARY APPROVED BY: L. DRAGO DATE: 12/20/2019 TDS > 500 ug/L RETIRED ASH BASIN ASH CHECKED BY: L. DRAGO DATE: 12/20/2019 ACTIVE ASH BASIN WASTE ' LANDFILL COMPLIANCE synTerra PROJECT MANAGER: C. SUTTELL BOUNDARY BOUNDARY RETIRED ASH BASIN WASTE www.synterracorD.com -'-' BOUNDARY FIGURE ES -lc NOTES: COMPARISON OF SIMULATED TDS ALL BOUNDARIES AREAPPROXIMATE. CONCENTRATIONS IN ALL NON -ASH LAYERS SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS MODELING REPORT COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION SYSTEMIFIPS320BEEN SET 0(NAD83) WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE BELMONT, NORTH CAROLINA .. r LEGEND REFERENCE LOCATION ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY i a.. RAPHIC SC DUKE 580 G580 1,160 NOTES: *"ENERGY. ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) THE LOCATION LABELED "POINT 2A" FOR SULFATEAND TDS WAS CHOSEN TO CAPTURE THE MAXIMUM DRAWN BY: J. EBENHACK DATE: 11/18/2019 CONCENTRATIONS IN THAT REGION. REVISED BY: R. KIEKHAEFER DATE: 12/29/2019 APPROVED BY: L. DRAGO DATE: 12/29/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/29/2019 PROJECT MANAGER: C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE synTerra SYSTEM FIPS 3200 (NAD83). WWW.svnterracorD.com FIGURE ES-2 REFERENCE LOCATIONS USED FOR TIME SERIES DATASETS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA i M M a 2,000 = C-by- R: Point 1 1,800 1 C-by-R: Point 2 ; C-by-R: Point 3 1,500 C-by- R: Point 4 '0 1,400 ==--C-in-P: Point 1 —=—=C-in-P: Point 2 p 1,200 d�% —=—=C-in-P: Point 3 1,000 " �% � _ —--C-in-P: Point 4 — — — 02L 5td = 700 µgf L S00 — — — — — — — — — — — — — _ _ _ _ _ _ _ _ 600 % r D % .� 400 200� R 0 00 m o � o N N � N N ry N m -y N N � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE ES-3a fENJERGY, REVISED BY. SUMMARY OF MAXIMUM BORON IN ALL NON -ASH MODEL LAYERS AS FUNCTIONS CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB OF TIME AT REFERENCE LOCATIONS 1, 2, 3, AND 4 FOR CLOSURE-BY-ECAVATION PROJECT MANAGER: C. SUTTELL AND CLOSURE -IN -PLACE UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION synTerra www.synterracorp.com BELMONT, NORTH CAROLINA Sulfate C-by-R: Point 1 2,000 C-by-R: Point 2a - C-by-R: Point 3 _ C-by-R: Point 4 bb C-in-P: Point 1 __-- C-in-P: Point 2a 0 ---- C-in-P: Point 3 -- -- C-in-P: Point 4 �, � 1,000 w — — — 02L Std = 250 µgf L c� 0 U % Qj +j 500 cn ________________________ rq �c a Ln o L1 C) rl N N N N N N N N rq Year � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE ES-3b fENJERGY, REVISED BY. SUMMARY OF MAXIMUM SULFATE IN ALL NON -ASH MODEL LAYERS AS CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB FUNCTIONS OF TIME AT REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR CLOSURE -BY - PROJECT MANAGER: C. SUTTELL ECAVATION AND CLOSURE -IN -PLACE `10 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION synTerra VAM synterracorp.com BELMONT, NORTH CAROLINA 4,000 1­1 3,500 J to E 3,000 Q 2,500 12 L 2,000 N V 0 1,500 CIS 1,000 TDS ti — C-by-R: Point 1 C-by-R: Point 2a — C-by-R: Point 3 C-by-R: Point 4 ----C-in-P: Point 1 ====C-in-P: Point 2a --=-C-in-P: Point 3 ----C-in-P: Point 4 — — — 02L 5td = 500 µg f L 50o---f__ _________________________ r%- H QD rq LO CD un CD un C) rn CD CD H � � °N° m m rl N rq N r.I r.1 N N r q N Yea r eDUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE ES-3C n ENERGY REVISED BY: SUMMARY OF MAXIMUM TDS IN ALL NON -ASH MODEL LAYERS AS FUNCTIONS OF CAROLINAS CHECKED BY: K. WEBB APPROVED BY: K. WEBB TIME AT REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR CLOSURE-BY-ECAVATION PROJECT MANAGER: C. SUTTELL AND CLOSURE -IN -PLACE UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA SyflTerrd www.synterracorp.com I BORON l h .h" 0 s S 630 \ "S 1 TDS SULFATE ( 1,300 GRAPHIC SC ALE 'DUKE ,300 2,600 4 ENERGY N FEET) CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 APPROVED BY: L. DRAGO DATE: 12/20/2019 CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerrd PROJECT MANAGER: C. SUTTELL www_svntarracnrn_mm s 1 - so s LEGEND 1 VERTICAL EXTRACTION WELLS y ", \,= o ♦ VERTICAL CLEAN WATER INFILTRATION WELLS s�630 ACTIVE ASH BASIN WASTE BOUNDARY s RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY i• .-- RETIRED ASH BASIN ASH LANDFILL WASTE BOUNDARY - - - - HYDRAULIC HEAD (FEET) NOTES: Boron Sulfate ALL BOUNDARIES ARE APPROXIMATE. > 700 Ng/L > 250 mg/L CONTOUR INTERVAL IS 5 FEET. FIGURE SHOWS ALTERNATIVE 3A REMEDIATION SYSTEM TES AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. > 500 mg/L DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83 AND NAVD88). FIGURE ES-4a SIMULATED COI CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA BORON SULFATE s2s �2s o sops sons S9S y N o o u� o S9S i,� s cn,vl c SO ti0 580 �O •a'A l 411 , GO APHIC SCALE,300 TDS i DUKE 1,300 2,600 s, ENERGY CAROLINAS (IN FEET) s S8p' DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 ~ APPROVED BY: L. DRAGO DATE: 12/20/2019 �S CHECKED BY: L. DRAGO DATE: 12/20/2019 ss synTerra PROJECT MANAGER: C. SUTTELL 90 oo� www_svntarrarnrn_rnm LEGEND $ VERTICAL EXTRACTION WELLS s or A VERTICAL CLEAN WATER INFILTRATION WELLS s o's 2 ' HORIZONTAL CLEAN WATER INFILTRATION WELLS s ao sus ACTIVE ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE 7 al BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN ASH LANDFILL r ' . WASTE BOUNDARY HYDRAULIC HEAD (FEET) NOTES: Boron Sulfate ALL BOUNDARIES ARE APPROXIMATE. > 700 Ng/L > 250 mg/L CONTOUR INTERVAL IS 2 FEET. FIGURE SHOWS ALTERNATIVE 3B REMEDIATION SYSTEM TI]S AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. > 500 mg/L DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FI PS 3200 (NAD83 AND NAVD88). FIGURE ES-4b SIMULATED COI CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 313 REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE OF CONTENTS SECTION PAGE EXECUTIVE SUMMARY.................................................................................................... ES-1 1.0 Introduction..................................................................................................................1-1 1.1 General Setting and Background..........................................................................1-1 1.2 Objectives.................................................................................................................1-4 2.0 Conceptual Site Model................................................................................................2-1 2.1 Groundwater System Framework........................................................................2-1 2.2 Flow System.............................................................................................................2-2 2.3 Hydrologic Boundaries.......................................................................................... 2-4 2.4 Hydraulic Boundaries............................................................................................ 2-4 2.5 Sources and Sinks....................................................................................................2-4 2.6 Water Budget...........................................................................................................2-5 2.7 Modeled Constituents of Interest......................................................................... 2-5 2.8 Constituent Transport............................................................................................ 2-6 3.0 Computer Model..........................................................................................................3-1 3.1 Model Selection....................................................................................................... 3-1 3.2 Model Description.................................................................................................. 3-1 4.0 Groundwater Flow and Transport Model Construction......................................4-1 4.1 Model Domain and Grid........................................................................................4-1 4.2 Hydraulic Parameters............................................................................................4-3 4.3 Flow Model Boundary Conditions.......................................................................4-4 4.4 Flow Model Sources and Sinks............................................................................. 4-4 4.5 Flow Model Calibration Targets........................................................................... 4-6 4.6 Transport Model Parameters.................................................................................4-7 4.7 Transport Model Boundary Conditions............................................................ 4-10 4.8 Transport Model Sources and Sinks...................................................................4-11 4.9 Transport Model Calibration Targets................................................................ 4-11 5.0 Model Calibration to Pre -decanted Conditions.....................................................5-1 5.1 Flow Model Calibration......................................................................................... 5-1 5.2 Flow Model Sensitivity Analysis.......................................................................... 5-7 5.3 Historical Transport Model Calibration.............................................................. 5-8 5.4 Transport Model Sensitivity Analysis................................................................. 5-9 Page i Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE OF CONTENTS (CONTINUED) 6.0 Predictive Simulations of Closure Scenarios......................................................... 6-1 6.1 Interim (Post -Decanted) Models with Active Ash Basin Decanted (2020-2029 or2020-2042)............................................................................................................ 6-2 6.2 Closure -by -Excavation with Monitored Natural Attenuation ......................... 6-4 6.3 Closure -in -Place with Monitored Natural Attenuation .................................... 6-8 6.4 Corrective Action Simulation.............................................................................. 6-11 6.5 Conclusions Drawn From the Predictive Simulations .................................... 6-13 7.0 References......................................................................................................................7-1 Page ii Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina LIST OF FIGURES Figure ES-1a Comparison of simulated boron concentrations in all non -ash layers Figure ES-1b Comparison of simulated sulfate concentrations in all non -ash layers Figure ES-1c Comparison of simulated TDS concentrations in all non -ash layers Figure ES-2 Reference locations used for time series datasets Figure ES-3a Summary of maximum boron in all non -ash model layers as functions of time at reference locations 1, 2, 3, and 4 for closure -by -excavation and closure -in -place Figure ES-3b Summary of maximum sulfate in all non -ash model layers as functions of time at reference locations 1, 2a, 3, and 4 for closure -by -excavation and closure -in -place Figure ES-3c Summary of maximum TDS in all non -ash model layers as functions of time at reference locations 1, 2a, 3, and 4 for closure -by -excavation and closure -in -place Figure ES-4a Simulated COI concentrations in all non -ash layers after 7 years of operating the alternative 3A remediation system Figure ES-4b Simulated COI concentrations in all non -ash layers after 7 years of operating the alternative 3B remediation system Figure 1-1 USGS location map Figure 4-1 Numerical model domain Figure 4-2 Fence diagram of the 3D hydrostratigraphic model used to construct the model grid Figure 4-3a Computational grid used in the model with 3x vertical exaggeration Figure 4-3b Model computational grid in plan view Figure 4-3c Model computational grin in the vicinity of the ash basin Figure 4-4 Hydraulic conductivity estimated from slug tests performed in ash at 14 sites in North Carolina Figure 4-5 Hydraulic conductivity estimated from slug tests performed in saprolite at 10 piedmont sites in North Carolina Figure 4-6 Hydraulic conductivity estimated from slug tests performed in the transition zone at 10 piedmont sites in North Carolina Figure 4-7 Hydraulic conductivity estimated from slug tests performed in fractured rock at 10 piedmont sites in North Carolina Figure 4-8 Distribution of model recharge zones Figure 4-9 Model surface water features Figure 4-10 Location of water supply wells in model area Figure 5-1a Model hydraulic conductivity zones in ash layers 4 and 5 Figure 5-1b Model hydraulic conductivity zones in ash layers 6 and 7 Page iii Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina LIST OF FIGURES (CONTINUED) Figure 5-1c Model hydraulic conductivity zones in ash layers 8 through 10 Figure 5-1d Model hydraulic conductivity zones in ash layer 11 Figure 5-2a Model hydraulic conductivity zones in saprolite layer 12 Figure 5-2b Model hydraulic conductivity zones in saprolite layer 13 Figure 5-2c Model hydraulic conductivity zones in saprolite layer 14 Figure 5-3a Model hydraulic conductivity zones in transition zone layer 15 Figure 5-3b Model hydraulic conductivity zones in transition zone layer 16 Figure 5-4a Model hydraulic conductivity zones in Fractured bedrock layer 17 Figure 5-4b Model hydraulic conductivity zones in Fractured bedrock layer 18 Figure 5-4c Model hydraulic conductivity zones in Fractured bedrock layer 19 Figure 5-5a Model hydraulic conductivity zones in lower bedrock layer 20 Figure 5-5b Model hydraulic conductivity zones in lower bedrock layers 21 and 22 Figure 5-5c Model hydraulic conductivity zones in lower bedrock layer 23 Figure 5-5d Model hydraulic conductivity zones in lower bedrock layer 24 Figure 5-5e Model hydraulic conductivity zones in lower bedrock layers 25 through 31 Figure 5-6 Simulated heads as a function of observed heads from the calibrated steady state flow model Figure 5-7 Simulated hydraulic heads in the saprolite under pre -decanted conditions (model layer 14) Figure 5-8 Simulated groundwater flow system in saprolite under pre -decanted conditions (model layer 14) Figure 5-9 Control volume used to calculate the water balance under pre -decanted conditions Figure 5-10a Boron source zones for the historical transport model in ash layers 4 to 8 Figure 5-10b Boron source zones for the historical transport model in ash layer 9 Figure 5-10c Boron source zones for the historical transport model in ash layers 10 and 11 and the coal pile source in layer 12 Figure 5-11a Sulfate source zones for the historical transport model in ash layers 4 through 8 Figure 5-11b Sulfate source zones for the historical transport model in ash layer 9 Figure 5-11c Sulfate source zones for the historical transport model in ash layers 10 and 11 and the coal pile source in layer 12 Figure 5-12a TDS source zones for the historical transport model in ash layers 4 through 8 Figure 5-12b TDS source zones for the historical transport model in ash layers 9 through 11 and the coal pile source in layer 12 Page iv Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina LIST OF FIGURES (CONTINUED) Figure 5-13a Simulated 2020 maximum boron concentrations in all non -ash layers Figure 5-13b Simulated 2020 maximum sulfate concentrations in all non -ash layers Figure 5-13c Simulated 2020 maximum TDS concentrations in all non -ash layers Figure 6-1 Simulated hydraulic heads in saprolite after decanting (model layer 14) Figure 6-2 Simulated groundwater flow system in saprolite after decanting (model layer 14) Figure 6-3a Simulated maximum boron concentrations in all non -ash layers after 8.8 years of decanted conditions when closure -in -place is completed Figure 6-3b Simulated maximum sulfate concentrations in all non -ash layers after 8.8 years of decanted conditions when closure -in -place is completed Figure 6-3c Simulated maximum TDS concentrations in all non -ash layers after 8.8 years of decanted conditions when closure -in -place is completed Figure 6-4a Simulated maximum boron concentrations in all non -ash layers after 22 years of decanted conditions when closure -by -excavation is completed Figure 6-4b Simulated maximum sulfate concentrations in all non -ash layers after 22 years of decanted conditions when closure -by -excavation is completed Figure 6-4c Simulated maximum TDS concentrations in all non -ash layers after 22 years of decanted conditions when closure -by -excavation is completed Figure 6-5 Closure -by -excavation design used in the simulations (AECOM, 2019a) Figure 6-6 Simulated local ash basin groundwater flow system in saprolite after the ash basin is closed by closure -by -excavation Figure 6-7a Simulated maximum boron concentrations in all non -ash layers in 2050 for the closure -by -excavation scenario Figure 6-7b Simulated maximum boron concentrations in all non -ash layers in 2100 for the closure -by -excavation scenario Figure 6-7c Simulated maximum boron concentrations in all non -ash layers in 2150 for the closure -by -excavation scenario Figure 6-7d Simulated maximum boron concentrations in all non -ash layers in 2200 for the closure -by -excavation scenario Figure 6-8a Simulated maximum sulfate concentrations in all non -ash layers in 2050 for the closure -by -excavation scenario Figure 6-8b Simulated maximum sulfate concentrations in all non -ash layers in 2100 for the closure -by -excavation scenario Figure 6-8c Simulated maximum sulfate concentrations in all non -ash layers in 2150 for the closure -by -excavation scenario Figure 6-8d Simulated maximum sulfate concentrations in all non -ash layers in 2200 for the closure -by -excavation scenario Page v Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina LIST OF FIGURES (CONTINUED) Figure 6-9a Simulated maximum TDS concentrations in all non -ash layers in 2050 for the closure -by -excavation scenario Figure 6-9b Simulated maximum TDS concentrations in all non -ash layers in 2100 for the closure -by -excavation scenario Figure 6-9c Simulated maximum TDS concentrations in all non -ash layers in 2150 for the closure -by -excavation scenario Figure 6-9d Simulated maximum TDS concentrations in all non -ash layers in 2200 for the closure -by -excavation scenario Figure 6-10 Reference locations used for time series datasets. Figure 6-11 Summary of maximum boron in all non -ash layers as functions of time at reference locations 1, 2, 3, and 4 for the closure -by -excavation scenario Figure 6-12 Summary of maximum sulfate in all non -ash layers as functions of time at reference locations 1, 2a, 3, and 4 for the closure -by -excavation scenario Figure 6-13 Summary of maximum TDS in all non -ash layers as functions of time at reference locations 1, 2a, 3, and 4 for the closure -by -excavation scenario Figure 6-14 Closure -in -place design used in the simulations (AECOM, 2019b) Figure 6-15 Simulated groundwater flow system in saprolite under closure -in -place (model layer 14). Figure 6-16a Simulated maximum boron concentrations in all non -ash layers in 2050 for the closure -in -place scenario Figure 6-16b Simulated maximum boron concentrations in all non -ash layers in 2100 for the closure -in -place scenario Figure 6-16c Simulated maximum boron concentrations in all non -ash layers in 2150 for the closure -in -place scenario Figure 6-16d Simulated maximum boron concentrations in all non -ash layers in 2200 for the closure -in -place scenario Figure 6-17a Simulated maximum sulfate concentrations in all non -ash layers in 2050 for the closure -in -place scenario Figure 6-17b Simulated maximum sulfate concentrations in all non -ash layers in 2100 for the closure -in -place scenario Figure 6-17c Simulated maximum sulfate concentrations in all non -ash layers in 2150 for the closure -in -place scenario Figure 6-17d Simulated maximum sulfate concentrations in all non -ash layers in 2200 for the closure -in -place scenario Figure 6-18a Simulated maximum TDS concentrations in all non -ash layers in 2050 for the closure -in -place scenario Page vi Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina LIST OF FIGURES (CONTINUED) Figure 6-18b Simulated maximum TDS concentrations in all non -ash layers in 2100 for the closure -in -place scenario Figure 6-18c Simulated maximum TDS concentrations in all non -ash layers in 2150 for the closure -in -place scenario Figure 6-18d Simulated maximum TDS concentrations in all non -ash layers in 2200 for the closure -in -place scenario Figure 6-19 Summary of maximum boron in all non -ash layers as functions of time at reference locations 1, 2, 3, and 4 for the closure -in -place scenario Figure 6-20 Summary of maximum sulfate in all non -ash layers as functions of time at reference locations 1, 2a, 3, and 4 for the closure -in -place scenario Figure 6-21 Summary of maximum TDS in all non -ash layers as functions of time at reference locations 1, 2a, 3, and 4 for the closure -in -place scenario Figure 6-22 Comparison of simulated boron concentrations in non -ash layers Figure 6-23 Comparison of simulated sulfate concentrations in non -ash layers Figure 6-24 Comparison of simulated TDS concentrations in non -ash layers Figure 6-25 Simulated hydraulic head in saprolite (model layer 14) with the alternative 3A remediation system operating Figure 6-26 Simulated hydraulic head in saprolite (model layer 14) with the alternative 3B remediation system operating Figure 6-27a Simulated boron concentrations in all non -ash layers after 4 years of operating the alternative 3A remediation system Figure 6-27b Simulated boron concentrations in all non -ash layers after 7 years of operating the alternative 3A remediation system Figure 6-27c Simulated boron concentrations in all non -ash layers after 10 years of operating the alternative 3A remediation system Figure 6-28a Simulated sulfate concentrations in all non -ash layers after 4 years of operating the alternative 3A remediation system Figure 6-28b Simulated sulfate concentrations in all non -ash layers after 7 years of operating the alternative 3A remediation system Figure 6-28c Simulated sulfate concentrations in all non -ash layers after 10 years of operating the alternative 3A remediation system Figure 6-29a Simulated TDS concentrations in all non -ash layers after 4 years of operating the alternative 3A remediation system Figure 6-29b Simulated TDS concentrations in all non -ash layers after 7 years of operating the alternative 3A remediation system Figure 6-29c Simulated TDS concentrations in all non -ash layers after 10 years of operating the alternative 3A remediation system Page vii Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina LIST OF FIGURES (CONTINUED) Figure 6-30a Simulated boron concentrations in all non -ash layers after 4 years of operating the alternative 3B remediation system Figure 6-30b Simulated boron concentrations in all non -ash layers after 7 years of operating the alternative 3B remediation system Figure 6-30c Simulated boron concentrations in all non -ash layers after 10 years of operating the alternative 3B remediation system Figure 6-31a Simulated sulfate concentrations in all non -ash layers after 4 years of operating the alternative 3B remediation system Figure 6-31b Simulated sulfate concentrations in all non -ash layers after 7 years of operating the alternative 3B remediation system Figure 6-31c Simulated sulfate concentrations in all non -ash layers after 10 years of operating the alternative 3B remediation system Figure 6-32a Simulated TDS concentrations in all non -ash layers after 4 years of operating the alternative 3B remediation system Figure 6-32b Simulated TDS concentrations in all non -ash layers after 7 years of operating the alternative 3B remediation system Figure 6-32c Simulated TDS concentrations in all non -ash layers after 10 years of operating the alternative 3B remediation system Page viii Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina LIST OF TABLES Table 5-1 Observed, computed, and residual heads for the calibrated flow model Table 5-2 Calibrated hydraulic conductivity parameters Table 5-3 Water balance on the groundwater flow system for pre -decanted conditions Table 5-4 Flow model sensitivity analysis Table 5-5 Ash basin COI source concentrations used in the historical transport model Table 5-6a Observed and computed boron (µg/L) concentrations in monitoring wells Table 5-6b Observed and computed sulfate (mg/L) concentrations in monitoring wells Table 5-6c Observed and computed TDS (mg/L) concentrations in monitoring wells Table 5-7a Transport model sensitivity to the boron Ka values Table 5-7b Transport model sensitivity to the sulfate Kd values Table 5-7c Transport model sensitivity to the TDS Kd values Table 6-1 Water balance on the groundwater flow system for decanted conditions Page ix Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 1.0 INTRODUCTION This groundwater flow and transport model report provides basic model development information and simulations of basin closure designs as well as results of corrective action simulations for the Allen Steam Station (Allen, Site, Station). The Site is owned and operated by Duke Energy Carolinas, LLC (Duke Energy) and is located near (south of) Belmont, Gaston County, North Carolina. The Station is situated on the west bank of the Catawba River portion of Lake Wylie, which provides water for Station operations (Figure 1-1). Model simulations were developed using flow and transport models MODFLOW and MT3DMS. Due to historical ash management and wastewater discharge activities at the Site, a numerical model was developed to evaluate transport of inorganic constituents of interest (COIs) in the groundwater downgradient of the ash basins. Numerical simulations of groundwater flow and transport have been calibrated to pre -decanting conditions and used to evaluate different scenarios being considered as options for closure of the ash basins. The simulations were also used to design a corrective action system that would achieve compliance with North Carolina Administrative Code, Title 15A, Subchapter 02L, Groundwater Classification and Standards (02L) by approximately the end of year 2029. This model and report is an update of a previous model developed by SynTerra in conjunction with Falta Environmental, LLC and Frx Partners (SynTerra, 2018b). 1.1 General Setting and Background The site encompasses 1009 acres along the west bank of Lake Wylie (a portion of the impounded Catawba River). Duke Energy also owns property along the discharge canal to the east and west of South Point Rd (NC Highway 273). In addition to the power plant property, Duke Energy also owns and operates the Catawba-Wateree Project [Federal Energy Regulatory Commission (FERC) Project No. 2232]. Allen Steam Station is a five -unit coal-fired electricity -generating facility with a capacity of 1,155 megawatts (MW). The Station began commercial operation in 1957 with Units 1 and 2 (330 MW total). Unit 3 (275 MW) was placed into commercial operation in 1959 followed by Unit 4 (275 MW) in 1960 and Unit 5 (275 MW) in 1961. The Station currently remains in service. Coal combustion residuals (CCRs) have historically been managed at ash basins located within two natural drainages impounded in part by earthen embankments south of the Station. The closest drainage south of the Station (the North drainage in Figure 1-1) was impounded to create a 132-acre ash basin, which was in use from 1957 to 1973. The North drainage historically consists of two tributaries to Lake Wylie that converged at the eastern edge of the Retired Ash Basin (RAB) before discharging into Lake Wylie. Page 1-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina The drainage south of the RAB (the South drainage in Figure 1-1) was impounded and used as an ash basin starting in 1973. It covers approximately 169 acres and is called the Active Ash Basin (AAB). The AAB stopped receiving sluiced ash in January 2019 and stopped receiving all wastewater inputs in February 2019. The AAB is currently being mechanically decanted to remove free water. Two ash storage areas, two structural fill areas, and a double -lined ash basin landfill were constructed within the waste boundary of the RAB. Groundwater at the Site generally flows from west to east toward Lake Wylie. Discharge from the AAB is currently permitted by the North Carolina Department of Environmental Quality (NCDEQ) Division of Water Resources (DWR) under National Pollutant Discharge Elimination System (NPDES) Permit NC0004979. Duke Energy operates the on -Site Industrial Landfill (RAB Ash Landfill) in accordance with the NCDEQ Solid Waste Section (SWS) on the property under Permit 3612- INDUS-2008. Coal has been stored north and northeast of the RAB within two separate piles, the main coal pile and the live coal pile. Collectively, the coal piles are referred to as the "coal pile area". The coal pile area is downgradient of the RAB. There are two earthen embankments impounding the ash basins: the East Dike, located along the west bank of Lake Wylie, and the North Dike, separating the AAB and RAB. The East Dike is classified as two separate regulated dams. North Carolina State ID GASTO 016 pertains to the RAB dike and North Carolina State ID GASTO 061 pertains the AAB Dike. The RAB is the original ash basin at the Site. It was formed in 1957 by constructing the North Dike and the north portion of the East Dike over former tributaries to Lake Wylie. As the original ash basin capacity diminished, the AAB was formed in 1973 by constructing the southern portion of the East Dike. Primary ponds 1, 2, and 3 were constructed in approximately 2004 over the north portion of the AAB. Fly ash that is precipitated from flue gas and bottom ash collected in the bottom of the boilers was sluiced into the primary ponds using conveyance water withdrawn from Lake Wylie. Since 2010, primary pond 1 only received stormwater and stormwater runoff (although still treated as wastewater due to probable contact with CCR material), while primary ponds 2 and 3 were used for settling purposes. Other inflows to the AAB included flows from coal pile runoff, landfill leachate, flue -gas desulfurization (FGD) wastewater, the station yard drain sump, and stormwater flows. Due to variability in Station operations and weather, inflows to the AAB were variable (SynTerra, 2018). These flows, with exception to stormwater sheet flow, were discontinued to the AAB in February 2019 and sent to the newly built Lined Retention Basin (LRB). Page 1-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Also located within the waste boundary of the RAB, there are two unlined dry ash storage areas, two unlined structural fill units, and the RAB Ash Landfill. The dry ash storage areas were constructed in 1996 under the NCDEQ DWR Deposition of Residual Solids (DORS) Program. Construction of the structural fill units also occurred under the DORS Program between 2003 and 2009. The double -lined RAB CCP Landfill was constructed in 2009. Dry fly ash (DFA) handling began in 2008; the DFA is either sent off -Site for beneficial reuse or disposed of at the on -Site RAB Ash Landfill. In early 2019, Duke Energy converted to dry handling of bottom ash at the Site. Groundwater requirements are based on the compliance boundary established by 15A NCAC 02L .0107 as 500 feet from the waste boundary or at the property boundary, whichever is closer to the source. The extent of the compliance boundaries for the AAB and RAB are defined by the 500 foot buffer to the north and south of the basins, by property boundaries to the west, and by the lakefront to the east (Figure 1-1). Groundwater influenced by the ash basins flows primarily west to east toward Lake Wylie. The approximate locations of the coal piles have remained consistent throughout the operating history of the Site. Minor changes to the coal pile footprint occur depending upon the volume of coal stockpiled on Site, which can vary substantially throughout the year. The main coal pile is positioned such that the western portion lies within the ash basins compliance boundary. The remainder of the main coal pile and the live coal pile are beyond the compliance boundary. Coal is not waste and therefore the coal piles do not have waste or compliance boundaries. The coal piles are not lined. However, in 2018, a lined holding basin was built in the southeast corner of main coal pile footprint as part of a water redirect project. It is anticipated that the coal piles will remain in place until the Station is decommissioned, at which time, the coal would be removed. The Site is situated within the Charlotte terrane, one of several tectonostratigraphic terranes that have been defined in the southern and central Appalachians, and it is in the western portion of the larger Carolina superterrane (HDR, 2015a). Topography consists of rounded hills and rolling ridges cut by small streams and drainages. Topographic divides are located to the west of the AAB and RAB (approximately along South Point Road), to the south of the AAB (approximately along Reese Wilson Road), and to the north of the RAB (approximately along Plant Allen Road). Natural topography at the Site generally slopes eastward from the divide toward Lake Wylie. Ground surface elevations in the area of the Site range from 690 feet in the southwestern portion of the Site to 570 feet along the west bank of Lake Wylie. Elevations in this report use the North American Vertical Datum of 1988 (NAVD88). Page 1-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Geology beneath the Site is classified into three units: saprolite (regolith), transition zone (below the saprolite and above the bedrock, characterized primarily by partially weathered rock), and bedrock (SynTerra, 2018). The bedrock is predominantly metamorphosed quartz diorite and meta-diabase. The water table occurs in the saprolite or ash at depths of less than 20 feet at most locations. The porosity of the saprolite and transition zone is generally more than an order of magnitude greater than the underlying rock, so the volume of water stored per unit of thickness is typically greater in the saprolite and transition zone than in the underlying bedrock. The hydraulic conductivity in the bedrock generally decreases with depth, and the groundwater flux in the saprolite and transition zone is typically much greater than the flux in the underlying bedrock. The water table elevation generally follows topographic changes, implying that groundwater flows from local recharge zones in topographically high areas, such as ridges, toward groundwater discharge zones, such as stream valleys. A groundwater flow and transport model was first developed in 2015 by HDR, Inc. in conjunction with University of North Carolina at Charlotte as part of the Corrective Action Plan (CAP) Part 1 (HDR, 2015b). The model was revised in the CAP Part 2 (HDR, 2016a) and again in the 2017 modeling report (HDR, 2017). SynTerra, in conjunction with Falta Environmental, LLC and Frx Partners, provided a preliminary update to the HDR model in 2018 (SynTerra, 2018b) that incorporated new data and expanded the model domain to refine the model. 1.2 Objectives The 2018 groundwater flow and transport model has been further refined to gain a better understanding of Site conditions. Model boundaries have been extended laterally to include uplands east of Lake Wylie to better simulate the groundwater flow system in the vicinity of the lake. This change avoids assumptions about the location of a no -flow groundwater divide under Lake Wylie. Stratigraphic layers have been refined with additional boring log data and the number of model layers was increased from 26 to 31 to sharpen resolution. Additional supply wells east of Lake Wylie were also included. Additional assessment activities, such as the installation of additional groundwater monitoring wells and multiple groundwater sampling events, have resulted in an increase of data describing hydraulic head and constituent of interest (COI) distribution, and are also included in the model. This report describes the current understanding of the groundwater flow and transport processes of mobile constituents at the Site. Page 1-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina The following data sources were used during calibration of the revised groundwater flow and fate and transport model: • Average Site -wide water levels measured in CAMA/CCR/Compliance groundwater monitoring wells through March 2019. • Groundwater quality data obtained from CAMA/CCR/Compliance sampling events conducted through March 2019. • Surface water elevations, as described in the Comprehensive Site Assessment (CSA) Update (SynTerra, 2018), and from surface water surveys conducted in 2019. • AAB pond water elevation during June 2019, provided by Duke Energy. • Estimated recharge, as described in HDR modeling report (HDR, 2017). • Information on private supply wells within a 0.5-mile radius of the ash basins (HDR, 2014a and 2014b) • Information on three public supply wells within a 0.5-mile radius of the AAB and RAB compliance boundaries, and one public supply well outside of the 0.5-mile radius and inside the model domain, based on the HDR well survey reports (HDR, 2014a and 2014b) and information provided by Aqua North Carolina Inc. (January and February 2017) and by Duke Energy (September to November 2018). • Well abandonment records for three of the four public supply wells, provided by SAEDACCO Inc. in October 2018. The model revision consisted of three activities: re -calibration of the steady-state groundwater flow model to hydraulic heads averaged through 2019; calibration of a transient model of the transport of boron, sulfate, and total dissolved solids (TDS) using the revised flow model and COI concentrations measured through 2019; and development of predictive simulations of closure scenarios and corrective action at the Site. One closure scenario, called closure -by -excavation, assumes that all the ash is excavated and placed in an on -Site landfill (AECOM 2019a). Another closure scenario, called closure -in -place, assumes the ash is graded and covered with a low permeability cap (AECOM 2019b). Corrective action measures designed to accelerate groundwater remediation are simulated to meet North Carolina Administrative Code (NCAC) Title 15A, Subchapter 02L, Groundwater Classification and Standards (02L) compliance by approximately the end of 2029, prior to the completion of closure -by -excavation and approximately at the same time as the completion of closure -in -place. Page 1-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina The predictive simulations described above are not intended to represent a final detailed closure design. These simulations use current designs that are subject to change as the closure plans are finalized. Corrective action designs might vary from those presented as proposed pilot testing progresses and additional field data is collected. The simulations are intended to show the key characteristics of groundwater flow and mobile constituent transport that are expected to result from the closure actions and corrective actions. Page 1-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 2.0 CONCEPTUAL SITE MODEL The conceptual site model of the Allen site is primarily based on the Comprehensive Site Assessment (CSA) Report (HDR, 2015a), the CSA Supplement Report (HDR, 2016b) the CSA Update (SynTerra, 2018) and the Corrective Action Plan (CAP) Update (SynTerra, 2019). These CSA reports contain extensive detail and data related to most aspects of the conceptual site model. 2.1 Groundwater System Framework The Site, located in the Piedmont Physiographic Province, conforms to the general hydrogeologic framework for sites in the Blue Ridge/Piedmont area, which are characterized by groundwater flow in a slope -aquifer system within a local drainage basin with a perennial stream (LeGrand, 2004). The groundwater system at the Site is unconfined and includes three hydrostratigraphic units: regolith (containing residuum/saprolite), transition zone, and bedrock. Saprolite can be up to 130 feet thick. A transition zone of partially weathered rock underlies saprolite and is up to 65 feet thick. The Site is underlain by fractured metamorphic rock. The degree of fracturing is spatially variable and generally decreases downward. Water was produced episodically when drilling through the transition zone and upper 50 feet to 100 feet of competent rock; this was inferred to indicate the occurrence of mildly productive fractures (SynTerra, 2018). The permeability is moderate in many of the bedrock wells, and it is inferred that the fracture density and hydraulic conductivity decrease downward, consistent with descriptions by Legrand (1988). The saprolite/transition zone is typically saturated in the vicinity of the ash basins, streams and lakes, and is partially saturated in most upland areas. A majority of the ash contained in the AAB and approximately half of the ash contained in the RAB is saturated (SynTerra, 2018). The ash fills two alluvial valleys, the North and South drainages, and is up to approximately 100 feet thick (SynTerra, 2018). Hydraulic conductivity at Allen was measured in the field using slug tests in the various hydrostratigraphic units. Pumping tests were also performed in ash and saprolite at two sites with multi -depth well installations. These pumping tests were analyzed by SynTerra using analytical methods in AQTESOLV (SynTerra, 2019). Thirty-nine slug tests and two pumping tests were performed in the coal ash at Allen. Hydraulic conductivity of the ash spans more than 4 orders of magnitude, from 0.03 feet per day (ft/d) to 200 ft/d, and the geometric mean is 2.5 ft/d. Seventy-one slug tests and two pumping tests were performed in the saprolite. Results indicate the hydraulic conductivity ranges from less than 0.01 ft/d to 115 ft/d with a geometric mean of 0.57 Page 2-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina ft/d. Eighty-seven slug tests were performed in the transition zone, and results indicate the hydraulic conductivity ranges from 0.04 ft/d to 280 ft/d with a geometric mean of 1.4 ft/d. The hydraulic conductivity of the bedrock was estimated from 26 slug tests and the results span a broad range, from 1E-5 ft/d to 11 ft/d with a geometric mean of 0.03 ft/d. The low values of hydraulic conductivity in bedrock were likely measured at wells that have poorly connected fractures and potentially large sections of unfractured rock. The high values of hydraulic conductivity were measured at wells that potentially intersect connected fracture zones in the rock. The range of observed hydraulic conductivity in the ash, saprolite, transition zone, and bedrock wells highlights the large degree of heterogeneity in the groundwater system. 2.2 Flow System The groundwater system is recharged by precipitation and from water that infiltrates through the ash basins. Mean annual recharge to shallow, unconfined aquifers in the Piedmont ranges from 4.0 inches per year (in/yr) to 9.7 in/yr (Daniel, 2001). Regional recharge was estimated at 8.3 in/yr (HDR, 2017), or 0.0019 ft/d. It was assumed that recharge was negligible in the vicinity of the Station power block, RAB Ash Landfill, the ash basin Primary Ponds and impoundment, Lake Wylie/Catawba River (Lake Wylie), the South Fork Catawba River (South Fork), the discharge canal, and the dikes and dams. Specific values assumed for the recharge are given in Section 4.4. The RAB was built in 1957, and it received sluiced ash until 1973. The AAB began receiving sluiced ash in 1973. Three primary ponds were constructed over the northern portion of the AAB in 2004 and were used for sluicing and settling until 2019. In January 2019 the AAB stopped receiving sluiced bottom ash and in February 2019 the AAB stopped receiving all discharge, including wastewater. Effluent from the primary ponds was routed to an impounded area in the southeast portion of the AAB via a partially -lined channel that flowed west approximately around the AAB then back east to the impounded area. Effluent in the impoundment then discharged to Lake Wylie from a weir box structure to a 42-inch diameter high -density polyethylene pipe to a concrete vault at the toe of the dam (NPDES Permit NC0004979, Outfall 002). The surface water elevation in the impoundment was controlled by the use of stop logs in the weir box structure. Until sluicing and wastewater discharge stopped and mechanical decanting began in June 2019, the elevation in the impoundment was maintained at about 634 feet. Page 2-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Water sluiced during operation of the RAB was accounted for within the model using an increased recharge relative to background values, at a flux of 12.7 in/yr (0.0029 ft/d). Hydraulic heads in the AAB were maintained by the general (fixed) head boundary condition that was assigned to the primary ponds and standing water, which matches measured surface water elevation. The regional hydraulic head is 565 feet to the east at Lake Wylie and to the west at South Fork, and approximately 570 feet to the north at the discharge canal. The head rises to a maximum of approximately 638 feet along a groundwater divide that occurs west and upgradient of the ash basins. The divide separates areas where recharge flows to the east to discharge in Lake Wylie from areas where recharge flows to the west or northwest to discharge to the discharge canal or the South Fork. The hydraulic head in the primary ponds is similar to the head along the regional groundwater divide. According to the 2015 CSA report (HDR, 2015), 219 private water supply wells were identified within a 0.5-mile radius of the AAB compliance boundary and former RAB compliance boundary. All 219 private water supply wells are located inside the model domain and were included in the simulations. Screen elevations were available for a small portion of the supply wells, whereas pumping rates are unknown for most of them. The average daily water use in North Carolina is 60 to 70 gallons per person (Treece, et. al. 1990). Therefore, a well providing water for a family of four people would be pumped at approximately 280 gallons per day (gal/day). This was the assumption used in the model. Four public water supply wells were identified inside the model domain. Three of the four wells are within a 0.5-mile radius of the AAB compliance boundary and RAB compliance boundary. The four public supply wells were/are owned and operated by Aqua North Carolinas Inc. (Aqua). Screen elevations and pumping rates for the public supply wells were provided by Aqua. Well depth ranges from 340 feet below ground surface (bgs) to 900 feet bgs (HDR, 2014a). According to information provided by Aqua to Duke Energy in January and February 2017, two of the wells at the Heather Glen/Highland community water system each yielded an average flow rate of 8,600 gal/day. One well at the South Point Landing community water system yielded an average of 4,400 gal/day. One well at the River Lakes community water system, which is outside of the 0.5-mile radius, yielded an average of 7,300 gal/day. The South Point Landing system served a neighborhood of 24 homes, and the other two systems were combined to serve two neighborhoods of 53 households. Page 2-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina In September 2018, Aqua abandoned the three wells within the 0.5-mile radius of the ash basin compliance boundaries, including two at Heather Glen/Highland and one at South Point Landing. This was because Duke Energy has implemented a permanent water solution which provides owners of the surrounding properties with water supply wells within a 0.5-mile radius of the ash compliance boundary with access to an alternate water supply via connections to the City of Belmont municipal water supply system. Therefore, Aqua no longer benefited from maintaining the wells. The Aqua well outside of the 0.5-mile radius at River Lakes remains in service. Residential sanitary wastewater is assumed to be disposed of through septic systems from homes with a private water supply well in the vicinity of the Site, which causes much of the water that is pumped from the aquifer to infiltrate into the vadose zone through septic drain fields. This septic return recharges the aquifer. Radcliffe et al. (2006) studied septic drain fields in the southeastern United States and found that 91 percent of the water used by a household was discharged to the septic drain field. This corresponds to a consumptive use of 9 percent. This is consistent with the data presented by Treece et al. (1990), who concluded that consumptive use is less than 6 percent. Daniels et al. (1997) developed a groundwater model of the Indian Creek watershed in North Carolina and used the analysis of Treece et al. (1990) to characterize pumping and septic return rates. These assumptions were used in the model. 2.3 Hydrologic Boundaries The major discharging locations for the shallow water system, such as Lake Wylie, the discharge canal, and the South Fork serve as hydrologic boundaries to the shallow groundwater system. 2.4 Hydraulic Boundaries The shallow groundwater system does not appear to contain impermeable barriers or boundaries in the study area. The current model assumes that the bedrock was impermeable below the depth of the bottom modeled layer, and a no -flow boundary was used to represent this condition. 2.5 Sources and Sinks Recharge is the major source of water in the uplands and ash basins. Most of the groundwater discharges to unnamed tributary streams, Lake Wylie, South Fork, and the discharge canal. Groundwater discharges into the ash basin and flows as pore water through the ash basin. As a result, the ash basin pore water acts as both a source of, and sink for, groundwater. A source is defined herein as a place where water enters the groundwater system, and a sink is where water leaves the system. Page 2-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Free standing water occurs in the three primary ponds and the impounded, southeast portion of the AAB, which appears to be largely a result of historical sluicing. Some of the free standing water might infiltrate to recharge groundwater, or it might receive discharge from ash basin pore water. Approximately 219 private water supply wells and four public water supply wells act as sinks to groundwater in the vicinity of the Site. These supply wells remove only a small amount of water from the overall hydrologic system. 2.6 Water Budget The long-term average rate of water inflow is assumed to equal the long-term average rate of water outflow from the study area. Water enters the groundwater system through distributed recharge or leakage of ash basin pore water, and leaves through discharge to streams, drains, wells, Lake Wylie, the South Fork, or water bodies in the ash basins. 2.7 Modeled Constituents of Interest Antimony, arsenic, beryllium, boron, cadmium, chromium (hexavalent and total), cobalt, iron, manganese, molybdenum, nickel, pH, selenium, strontium, sulfate, thallium, total dissolved solids (TDS), and vanadium have been identified as constituents of interest (COIs) at the Allen Site (SynTerra, 2018). Of these COIs, antimony, chromium (total), cobalt, iron, manganese, pH, and vanadium were also detected at concentrations greater than their respective 02L standard or Interim Maximum Allowable Concentration (IMAC) in Site background wells, upgradient of the ash basin. Cobalt, iron, manganese, and vanadium are commonly detected in shallow groundwater in the Piedmont of North Carolina. Three conservative COIs that are present beyond the compliance boundary and that have characteristics of groundwater plumes were selected for inclusion in the transport model at the Site. These COIs include boron, sulfate, and TDS. Boron is present in significant concentrations in the AAB and RAB. The boron plume extends east and northeast beyond the compliance boundaries of the AAB and RAB. Sulfate and TDS are present at concentrations greater than the 02L standard beyond the compliance boundary, primarily in the northeastern portion of the RAB near the coal pile (Figure 1- 1). There are two primary source areas for sulfate and TDS that contribute to concentrations greater than the 02L standard beyond the compliance boundary. One is a small area (6.5 acres) in the northern RAB, west-southwest of the coal pile. Mill rejects from the coal pile with high pyrite content were disposed of in this area, which resulted in low pH and greater sulfate concentrations. This area is referred to as the 'Low pH Page 2-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Region' in this report. The other source of sulfate and TDS is the coal pile, north of the RAB. Boron, sulfate, and TDS are assumed to be non -reactive with subsurface solids and therefore a conservative estimate and indicator of constituent transport in groundwater. Groundwater concentrations for boron and sulfate within and downgradient of the ash basins are significantly greater than background concentrations making source and plume delineation unambiguous. 2.8 Constituent Transport COIs present in coal ash can dissolve into the ash pore water. As water infiltrates through the basins, water containing COIs can enter the groundwater system through the bottom of the ash basins. Once in the groundwater system, COIs are transported by advection and dispersion, subject to retardation due to adsorption to solids. Similarly, water that infiltrates through the coal pile area can transport COIs into the groundwater system below the coal piles. If COIs reach a hydrologic boundary or water sink, they are removed from the groundwater system and enter the surface water system, where in general, they are greatly diluted. Page 2-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 3.0 COMPUTER MODEL 3.1 Model Selection The numerical groundwater flow model was developed using MODFLOW (McDonald and Harbaugh, 1988), a three-dimensional (3D) finite difference groundwater model created by the United States Geological Survey (USGS). The chemical transport model is the Modular 3-D Transport Multi -Species (MT3DMS) model (Zheng and Wang, 1999). MODFLOW and MT3DMS are widely used in industry and government, and are considered to be industry standards. The models were assembled using the Aquaveo GMS 10.3 graphical user interface (http://www.aquaveo.com/). 3.2 Model Description MODFLOW uses Darcy's law and the conservation of mass to derive water balance equations for each finite difference cell. MODFLOW considers 3D transient groundwater flow in confined and unconfined heterogeneous systems, and it can include dynamic interaction with pumping wells, recharge, evapotranspiration, rivers, streams, springs, lakes, and swamps. Several versions of MODFLOW have been developed since its inception. This study uses the MODFLOW-NWT version (Niswonger, et al., 2011). The NWT version of MODFLOW provides improved numerical stability and accuracy for modeling problems with variable water tables. That improved capability is helpful in the present work where the position of the water table in the ash basin can fluctuate depending on the conditions under which the basin is operated and on the closure action activities. MT3DMS uses the groundwater flow field from MODFLOW to simulate 3D advection and dispersion of the dissolved COIs, including the effects of retardation due to COI adsorption to the soil and rock matrix. Page 3-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 4.0 GROUNDWATER FLOW AND TRANSPORT MODEL CONSTRUCTION The flow and transport model of the Site was built through a series of steps: • Step 1: Build a 3D model of the Site hydrostratigraphy based on field data. • Step 2: Determine the model domain and construction of the numerical grid. • Step 3: Populate the numerical grid with flow parameters. • Step 4: Calibrate the steady-state flow model to pre -decanting hydraulic heads with adjustments of the flow parameters. • Step 5: Develop a transient model of historical flow and transport to provide time -dependent constituent transport development. • Step 6: Calibrate to recent boron, sulfate, and TDS concentration analytical data to reproduce the observed COI plumes within the model. 4.1 Model Domain and Grid The initial steps in the model grid generation process were the determination of model domain, and construction of a 3D hydrostratigraphic model (Figure 4-1). The model has dimensions of approximately 3.1 miles (-16,500 feet) by 2.5 miles (-13,000 feet). The model is generally bounded to the west by the South Fork and extends to the uplands east of Lake Wylie. The distance to the north and south boundaries from the ash basins is large enough to prevent boundary conditions from artificially affecting results near the basins. In 2014, topographic and bathymetric elevation contours and spot elevations were produced from surveys conducted at Allen by Duke Energy. Those surveys covered part of the modeled area, so elevation data extracted from the North Carolina Floodplain Mapping Program's 2010 laser imaging detection and ranging (LiDAR) elevation data were also used. At the Site, Lake Wylie and the AAB free water bathymetry data were incorporated in the surface interpolation (HDR, 2017). Elevation contours of the original ground surface were digitized in computer -aided design (CAD) software from engineering drawings supplied by Duke Energy. These data were imported into GIS and georeferenced. These contours were trimmed to the areas underlying the AAB and RAB, dams, dikes, and ash storage areas. The source data used in the existing surface were then replaced by the original surface data where there was overlap. Elevation data from coal storage areas were removed. The pre - construction surface was then created using the combination of original surface Page 4-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina elevations, 2014 survey elevations, and 2010 LiDAR elevations (HDR, 2017). The bathymetry of Lake Wylie was digitized in ArcGIS using a USGS topographic map provided in ArcGIS. This surface was combined with topographic data to define the top of saprolite (layer 12). The hydrostratigraphic model (called a solids model in GMS) consists of six units: additional ash pile-up, ash, saprolite, transition zone, fractured bedrock, and bedrock (Figure 4-2). Five solids were created and then subdivided after the computational mesh was developed. The lower contact between the ash basin and underlying saprolite was assumed to be the original ground surface prior to construction of the ash basins. The additional ash pile-up solid was included to account for potential re -graded ash under closure. Contacts between the saprolite, transition zone, and underlying bedrock were determined by interpolating data measured in borings. While the contacts between the upper units (ash, saprolite, transition zone, bedrock) are well defined, the division of the bedrock into an upper fractured zone and deeper bedrock is subjective. For purposes of model construction, values were extrapolated in areas outside of the ash basins where data were sparse or unavailable. Extrapolation was performed with the Kriging geostatistical gridding method using the Surfer (Golden Software) contouring and 3D surface mapping software. A contact between fractured and relatively unfractured bedrock was assumed to occur 50 feet below the bottom of the transition zone, based on general field observations and data from boring logs interpretation. The bottom of the model was set at approximately 900 feet below bottom of fractured bedrock. The numerical model grid consists of 31 layers representing the hydrostratigraphic units (Figure 4-3a through Figure 4-3c). The model grid was set up to conform to the hydrostratigraphic contacts from the solids model. The model grid layers correspond to the hydrostratigraphic units as follows: Hydrostratigraphic layer Grid layer Additional Ash Pile -Up 1-3 Ash 4-11 Saprolite 12-14 Transition zone 15-16 Fractured bedrock 17-19 Bedrock 20-31 Page 4-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Grid layers 1-11 were set as inactive outside of the region of the ash basin as determined from aerial photos and the CSA Update (SynTerra, 2018). Grid layers 4-11 represent the current ash within the ash basins, whereas layers 1-3 were created to account for ash that might be consolidated during closure. The numerical grid consists of rectangular blocks arranged in columns, rows and layers. There are 189 columns, 186 rows, and 31 layers (Figure 4-3a through Figure 4-3c). The grid contains a total of 794,505 active cells. The maximum width is 148 feet for the rows and 191 feet for the columns. The size of the grid blocks is refined in the vicinity of both ash basins at approximately 40 feet in width. 4.2 Hydraulic Parameters The horizontal hydraulic conductivity and the horizontal to vertical hydraulic conductivity anisotropy ratio are the main hydraulic parameters in the model. The distribution of these parameters is based primarily on the model hydrostratigraphy, with additional horizontal and vertical heterogeneity. The geometries and parameter values of the heterogeneous distributions were determined largely during the flow model calibration process. Initial estimates of parameters were based on literature values; results of slug tests, pumping tests, and core tests; and simulations performed using the previous flow model. The hydraulic parameter values were adjusted during the flow model calibration process (described in Section 5.0) to provide the best fit to observed water levels in observation wells. The hydraulic conductivity of coal ash measured at 14 sites in North Carolina ranges over 4 orders of magnitude, with a geometric mean value of approximately 1.8 ft/d. Ash hydraulic conductivity values estimated by interpreting slug test and pumping test data at Allen spans 4 orders of magnitude and range from 0.03 ft/d to 200 ft/d with a geometric mean of 2.5 ft/d (Figure 4-4). The hydraulic conductivities from hundreds of slug tests performed in saprolite wells at 10 Duke Energy sites within the Piedmont range over 4 orders of magnitude and have a geometric mean value of 0.9 ft/d (Figure 4-5). Saprolite hydraulic conductivity values estimated by interpreting slug test and pumping test data at Allen range from 0.01 ft/d to 115 ft/d with a geometric mean of 0.6 ft/d. Transition zone hydraulic conductivities from hundreds of slug tests at 10 Duke Energy sites within the Piedmont range over 5 orders of magnitude, with a geometric mean value of 0.9 ft/d (Figure 4-6). Transition zone hydraulic conductivity values estimated by interpreting slug test data at Allen range from 0.04 ft/d to 280 ft/d with a geometric mean of 1.4 ft/d. Page 4-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Fractured bedrock hydraulic conductivities from hundreds of slug tests at 10 Duke Energy sites within the Piedmont in North Carolina (Figure 4-7) range over 6 orders of magnitude, with a geometric mean value of 0.3 ft/d. Fractured bedrock hydraulic conductivity values estimated by interpreting slug test data at Allen range from 11 ft/d to 1E-5 ft/d with a geometric mean of 0.03 ft/d. 4.3 Flow Model Boundary Conditions The model is bounded on the west by South Fork, and on the north, south and east by upland areas. South Fork is represented by a specified head boundary at 565 feet, which is the typical stage of the lake. The upland areas are represented using specified head boundaries at 5 feet below the ground surface. These specified head boundaries are applied to the upper most active layer of the model. 4.4 Flow Model Sources and Sinks Flow model sources and sinks on the interior of the model consist of recharge, Lake Wylie, the South Fork, unnamed tributary streams, primary ponds and ash basin impoundments, wetlands, discharge canal and an internal channel within the AAB, and groundwater pumping through supply wells. Recharge is a key hydrologic parameter in the model (Figure 4-8). As described in Section 2.2, the recharge rate for upland areas of the Site was assumed to be 0.0019 ft/d. The recharge rate was set to zero in the regions around the lakes that serve as groundwater discharge zones. The recharge rate for the Station was set to 0.0001 ft/d, due to the large areas of roof and pavement. The recharge rate at the double -lined RAB CCP Landfill was set to 10-5 ft/d after its construction in 2009. Recharge on the East Dam and the North Dam was set to 10-5 ft/d because of the low permeability of these features. Recharge on the RAB was assumed to be greater than ambient conditions during sluicing (1957 to 1973) and was set to 0.0029 ft/d. Recharge over the primary ponds and the southeast impoundment area in the AAB was set to zero during its operation (1973 to present), because these areas were represented with specified head boundary conditions. Recharge to the remaining portion of the AAB was assumed to be the same as that to the upland areas (0.0019 ft/d). Recharge was omitted from the surface water on the Lake Wylie, South Fork, and the discharge canal (Figure 4-8). Recharge was not adjusted during the model calibration process, but it is included in the sensitivity analysis. The reason for not including recharge as a calibration parameter is that for steady-state flow, the hydraulic heads are determined primarily by the ratio of recharge to hydraulic conductivity, so the two parameters are not independent. In situations where groundwater discharges to a flow measuring point, (for example, a gauged stream in a watershed), the flow measurement can be used to calibrate the Page 4-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina recharge value, allowing both the recharge rate and the hydraulic conductivity to be simultaneously calibrated. However, no streams were gauged at the Allen Site, so recharge was fixed. Lakes and rivers were represented as specified head boundaries (called "General Head" boundaries in MODFLOW) with the head set to their respective stages (Figure 4-9). Lake Wylie and the South Fork were maintained at an elevation of 565 feet above NAVD88 datum based on the CSA Update Report (SynTerra, 2018). The discharge canal was set at 570 feet, the primary ponds were set at approximately 636 feet for Pond 1, 639 feet for Pond 2, and 637 feet for Pond 3, based on surface water measurements collected by Duke. The stage of the two southwest ponds in the AAB were set to approximately 638 feet and 637 feet based on surface water measurements. The impounded southeast portion of the AAB was set at 634 feet, according to field measurement performed by Duke Energy during the modeled period. The channel through the AAB was represented as a general head boundary, even though streams elsewhere in the model were treated as drains. This was done to allow water to flow into or out of the channel as it flows through the AAB. Based on the surface LiDAR elevation, the stage of the channel ranged from 632 feet to 639 feet. The conductance of the bottom of the general head boundaries was set to 100 square feet per day (ft2/day), a relatively large value that will cause negligible head loss, and was not adjusted during calibration. Unnamed tributary streams outside of the ash basins and drains inside the ash basins were represented as type 3 boundary conditions, called "drains" in MODFLOW (Figure 4-9). A "drain" condition specifies the maximum head at the boundary, but the head can drop below this value. The streams exert significant local control on the hydraulic head in the model. The elevation of the streams was set to the ground surface elevation determined from the LiDAR and adjusted locally during calibration. The drain conductance was set to 100 ft2/day and was not adjusted during calibration. The hydraulic history of the ash basins was represented by assuming present conditions approximate the conditions in the basin since they were built. Exceptions to this include the recharge distribution on the basins. Recharge was assumed to be equal to the ambient recharge in the uplands in the AAB until 1973 when recharge in the ponded regions is set to zero. Recharge over the RAB was set at a value higher than the ambient flux during sluicing prior to 1973, and then it was decreased to ambient when the sluicing stopped in 1973. Recharge over the double -lined RAB Ash Landfill was further reduced after the installation of a liner system in 2009 (Figure 4-8). Page 4-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Relatively little information was available about the private wells in the model area. The locations of identified water supply wells in the model area are shown on Figure 4- 10. Screen elevations for part of the wells were obtained through water supply well surveys (HDR, 2014a and 2014b); those with no information were assumed to have screen elevations within bedrock similar to adjacent wells. Pumping rates were mostly unknown and were assumed to be 280 gals/day, which is an average daily water use for a family of four (Treece et al. 1990; North Carolina Water Use, 1987, and 1995). Septic return was assumed to be 94 percent of the pumping rate, based on Treece et al. (1990), Daniels et al. (1997) and Radcliffe et al. (2006). Septic return was injected into saprolite (layer 14) in the model. The four public supply wells (owned by Aqua North Carolina, Inc.) had reported flow rates ranging from 4,400 gal/day to 8,600 gal/day. Three out of the four public wells were abandoned in September 2018. Those three wells are included in the model at their average flow rate until they were abandoned. The well that serves the River Lakes community water system located beyond than 0.5 mile radius of the compliance boundary is still in operation at an average pumping rate of 7,300 gal/day, and it was assumed that this well would continue to operate in the future. This well is located approximately 3/4 of a mile west of the AAB waste boundary. 4.5 Flow Model Calibration Targets The flow model steady-state calibration targets were determined by averaging water levels, between June 2015 and March 2019. Water level measurements were taken from 198 groundwater monitoring wells. In general, wells with an S designation at the end of the name are screened either in the ash or the saprolite, wells with a D designation at the end of the name are screened in the transition zone, and wells with a BR designation are screened in the upper bedrock. Wells with a SS designated are installed in saprolite beneath the footprint of the ash basins. Wells with the BRL or BRLL designation were screened in the lower bedrock. Wells with the AP designation are screened in ash pore water. For comparison, the previous HDR 2017 flow model was calibrated with data from 154 wells obtained in September 2016 and the previous SynTerra model was calibrated with data from 179 wells (SynTerra 2018b). This updated model was calibrated with data from 198 wells, which includes additional wells that were installed and sampled since or concurrent with the 2018 preliminary model update report. These additional wells included wells installed within ash pore water in the basins; in groundwater in saprolite beneath the ash basins; and in saprolite, transition zone, upper bedrock, and lower bedrock downgradient of the ash basins and coal pile. Page 4-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Water levels used for this round of calibration were determined by taking the average value for head data. Water levels are expected to vary on an annual period due to seasonal changes in recharge. These fluctuations in water level are not simulated because the flow model is steady state. The average water level values are the best available estimates of the steady state hydraulic heads, so they were used for calibration. The observed hydraulic head was considerably below the simulated hydraulic head at well location, AB-23BRU, and considerably above the hydraulic head at well location CCR-3S. The hydraulic heads in AB-23BRU fluctuated up to 100 feet over multiple sampling events, presumably because the well was completed in bedrock with a very low permeability, and therefore was slow to respond after water was removed during sampling. The anomalously low observed head probably occurred because the well had not equilibrated with the ambient head when the water level was measured. As a result, well AB-23BRU was not used in the calibration. The hydraulic head at well CCR-3S was consistent over the four years of water level measurements. However, the head in CCR-3S was 6 to 8 feet higher than water levels in CCR-4S, and 10 to 14 feet higher than water levels in CCR-5S, which are screened at similar depths in the vicinity of CCR-3S. The elevated head at CCR-3S appears to result from a localized anomaly that is unrepresentative of the unconfined aquifer in this area. This anomaly was difficult to explain within the constraints of the hydrogeologic style used to calibrate the head model, so CCR-3S was not used as a basis to adjust the distribution of hydraulic conductivity. CCR-3S was included in the transport calibration. 4.6 Transport Model Parameters The transport model uses a sequence of steady-state MODFLOW simulations to provide the time -dependent groundwater velocity field. The MODFLOW simulation was started January 1957 and continued through June 2020, which is the estimated time for completion of ash basin decanting. When the Station began operations in 1957, the original ash basin (current RAB) began to receive ash. This basin appears to have been an impounded water body during its operation, but information on operation of this ash basin is unavailable. The operation of the RAB was represented by increasing the recharge rate to account for sluicing, and by assuming the concentration of boron in the ash basin has been constant. The history of the AAB starts in 1973 and includes the creation of the three primary ponds. The flow model assumes that the hydraulic heads are maintained at the same level as they were prior to decanting. Page 4-7 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina The key transport model parameters are the constituent source concentration in the ash basins and the constituent soil -water distribution coefficients (Kd). Secondary parameters are the longitudinal, transverse, and vertical dispersivities, and the effective porosity. Constituent source concentrations were estimated from recently measured ash pore water concentrations in monitoring wells. Temporal changes in concentration are poorly constrained (no historical concentration data), so it was assumed that concentrations have remained constant through time and equal to the concentrations determined during the calibration process. The numerical treatment of adsorption in the model requires special consideration because part of the system is a porous media (the ash, saprolite, and transition zone) with a relatively high porosity, whereas the bedrock is a fractured media with very low matrix porosity and permeability. As a result, transport in the fractured bedrock occurs almost entirely through the fractures. The MODFLOW and MT3DMS flow and transport models used here simulate fractured bedrock as an equivalent porous media. With this approach, an effective hydraulic conductivity is assigned to the fractured rock zones so that it produces the correct volumetric flux (volume of water flowing per area of rock per time) for a given hydraulic gradient. However, because the water flows almost entirely through the fractures, this approach requires that a small effective porosity value (0.05 or less) be used for the transport calculations to compute a realistic pore velocity. The velocity of a COI, Vc, is affected by both the porosity, 0, and the retardation factor, R, as: v, OR (la) where the COI retardation factor is computed internally in the MT3DMS code using a conventional approach: R=1+pbK a 0 and V is the volumetric flux (Darcy velocity), pb is the bulk density and Kd is the distribution coefficient assuming linear equilibrium sorption. The retardation factor for boron in fractured rock is expected to be in the same range as R for porous media. However, it is apparent from (1b) that R can become large if 0 is reduced and Kd is held constant. This is unrealistic, and it is the reason why a small Kd value is assigned to the bedrock, where the effective porosity is due to the fractures, and is low. This reduction of Kd is justified on physical grounds because COIs in fractured rock interact with only a Page 4-8 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina small fraction of the total volume in a grid block, whereas COIs in porous media are assumed to interact with the entire volume. The Kd for boron in the bedrock layers of the model was reduced by scaling it to the bedrock porosity. This causes the retardation factor in the fractured rock to be similar to R in the saprolite and transition zone. Ash leaching tests were performed on five samples from the Allen ash basins using USEPA Method 1316 (LEAF). Linear adsorption Kd values for boron were determined based on the leaching data. The results range from 0.1 milliliter per gram (mL/g) to 0.3 mL/g with an average of 0.2 mL/g. The modeling approach for the predictive simulations of future boron transport allows the boron concentration in the ash to vary with time in response to flushing by groundwater. Using the Kd value that is derived from ash leaching tests provides a realistic approach to estimating the model response of the boron in the ash to groundwater flushing. Twelve samples of aquifer material from different locations and depths (saprolite, transition zone, and bedrock) at the Site were analyzed previously using batch and column experiments to estimate Kd values for boron in the aquifer material (Langley and Oza, 2015; Langley and Kim, 2016). In the batch experiment, Kd values were determined assuming a linear isotherm. Only five (5) out of the 24 batch experiments showed linear adsorption and the results ranged from 0.1 mL/g to 3.0 mL/g. Adsorption in the rest of the experiments was non -linear and Kd cannot be determined. In the column experiments, linear adsorption Kd values were estimated from the breakthrough curve data. Boron breakthrough was fast compared to the sampling interval and Kd could be estimated for only one (1) out of 12 samples (70 mL/g for a bedrock sample). This value (Kd = 70 mL/g) is more than an order of magnitude greater than other measurements. A sensitivity analysis to further evaluate the effect of Kd values on COI transportation is given in Section 5.5. The Kd value for COIs in aquifer material outside of the ash basins was treated as a potential calibration parameter. Values of Kd = 0.2 mL/g were assumed for boron in the saprolite and transition zone based on laboratory values measured in ash. Values of Kd in the fractured bedrock and competent bedrock were reduced to 0.02 mL/g to maintain a consistent retardation factor with depth. This is because the retardation factor is proportional to the ratio of the Kd and porosity (eq. 1b), and the porosity was assumed to decrease with depth. Values of Kd = 0.1 mL/g were assumed for sulfate and TDS in the saprolite and transition zone based on laboratory values measured in ash. Values of Kd in the fractured bedrock and competent bedrock were reduced to 0.01 mL/g to maintain a consistent retardation factor with depth. Page 4-9 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Porosity used in the transport analysis was assumed to be uniform across grid layers, but to decrease with depth according to the following distribution: Layer Effective Porosity 1-11 0.3 12-14 0.2 15-16 0.1 17-19 0.05 20-26 0.01 The longitudinal dispersivity was assigned a value of 20 feet, the transverse dispersivity was set to 2 feet, and the vertical dispersivity was set to 0.2 feet for all COIs. These values were estimated using guidelines in Gelhar (1986) for a plume several hundred feet long. The dry bulk density was assumed to be 1.6 g/mL. Porosity, dispersivity, and dry bulk density are poorly constrained by data from the Site, so values were based on estimates from other locations or studies. Values of porosity in the upper grid layers are based on general estimates for ash and saprolite, and these values were assumed to decrease with depth to the unfractured rock (approximately 0.01). Values of dispersivity are scale and location dependent. The dispersivity was estimated to be consistent with a plume length of several hundred feet, according to data summarized by Gelhar (1986). 4.7 Transport Model Boundary Conditions The transport model boundary demonstrates no -flow conditions on the exterior edges of the model except where general head boundaries exist [specified as a concentration of 0 micrograms per liter (µg/L)]. All of the general head water bodies have a fixed concentration of 0 µg/L . As water containing dissolved constituents enters these zones, the dissolved mass is removed from the model. Infiltrating rainwater is assumed to lack COIs, and it enters from the upper active layer of the model. The initial condition for the pre -decanted conditions transport model is zero concentration of COIs in groundwater. No background concentrations are considered. The COI concentrations in the RAB are assumed to be at the observed concentrations at the start of the simulation (year 1957). The COI concentrations in the AAB are zero at the start of the simulation and they increase to the observed concentrations in 1973 when the AAB is constructed. Page 4-10 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 4.8 Transport Model Sources and Sinks The ash basins are the primary source of boron, sulfate, and TDS in the model and the coal pile is an additional source of sulfate and TDS. In the ash basin the primary source location for sulfate and TDS is the "Low pH Region" of the RAB where mill rejects were deposited. The ash basin sources are simulated by holding the COI concentrations constant in cells located inside the ash basins. This allows infiltrating water to carry dissolved constituents from the ash into the groundwater system in the model. The coal pile sources are simulated by holding the sulfate and TDS concentrations constant in the upper layer of saprolite (layer 12) within the coal pile. Chemical analyses from 21 wells were used to characterize the distribution of COI concentrations within the ash basins. The concentrations observed in the wells were assumed to represent the concentrations in ash in the vicinity of the well throughout the calibration simulation. This resulted in patch -like zones of concentrations. At certain locations inside the ash basin, different COI concentrations were observed at different depths, so different specified concentration zones were assigned to different layers. During model calibration, the concentrations of COIs in the ash basins and coal pile area were subdivided into additional zones to match COI concentrations observed in monitoring wells outside the ash basins. The transport model sinks are the lakes, channels, ponds, and rivers represented in the flow model using a general head boundary condition. As groundwater enters these features, it is removed from the groundwater system along with dissolved COI mass. Similarly, COI mass is removed when COIs are transported to extraction wells. 4.9 Transport Model Calibration Targets Transport model calibration targets are COI concentrations measured in 199 monitoring wells between the third quarter of 2018 and first quarter of 2019. The most recent COI concentration data for a given well was used for calibration. All sampled wells are included in the calibration. Page 4-11 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 5.0 MODEL CALIBRATION TO PRE -DECANTED CONDITIONS 5.1 Flow Model Calibration The flow model was calibrated in stages starting with a model that assumed homogeneous conditions in most formations. Calibration was done by manual adjustments of parameters. As the effort continued, some formations were given different properties in different layers. Calibration was done by seeking the simplest configuration of parameters that matched the observed heads and geologic conditions. The layer properties were initially homogeneous across the model domain, and then local zones of different hydraulic conductivity were created to improve the ability of the model to predict hydraulic heads observed in the field. The hydraulic conductivity zones are shown in Figure 5-1 through Figure 5-5, and the calibrated hydraulic conductivity values assigned to each zone in each layer are listed in Table 5-2. Zones where the hydraulic conductivity contrasts with enveloping material, similar to the zones used in the model (Figures 5-1 through Figure 5-5), are recognized in fractured crystalline rock. For example, flat -lying zones of interconnected fractures several hundred feet or more across were described in crystalline rock at the USGS Mirror Lake research site (e.g. Tiedeman et al. 2001), and similar fracture zones have been recognized at other fractured rock sites. Vertical fracture zones are also recognized in crystalline rock, and in some cases, vertical fractures zones are inferred to underlie linear topographic features (lineaments). Quartz cement, or weathering that produces an accumulation of clay minerals can create zones in saprolite where the hydraulic conductivity is less than the average value. The flow calibration was done iteratively with transient transport simulations. This was necessary in order to match both the heads and the COI concentration distributions. The flow model was calibrated by starting with uniform parameters and adjusting them to match the average hydraulic head data up to the first quarter of 2019. After an initial calibration that matched the observed heads, the flow model was used to conduct a transport analysis. The distribution of hydraulic conductivity was adjusted further to improve the match between predicted and observed concentrations. This adjustment included reducing or increasing the hydraulic conductivity in some locations below ash. This reduced or increased the downward flux of COIs, which improved the match to observed concentrations. After hydraulic conductivities were adjusted to improve the match to concentrations, predicted and observed heads were compared again and additional adjustments were made accordingly. Page 5-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Results of slug tests for the different hydrostratigraphic units at Allen and pumping tests conducted in ash and saprolite at Allen were compiled with slug test results from wells screened in ash pore water from 14 similar sites, and slug test results from wells screened in saprolite, transition zone, and fractured bedrock from 10 similar sites (Figure 4-4 to Figure 4-7). This resulted in a significant database of hydraulic conductivity estimates based on slug tests and pumping tests, including 205 measurements in ash, 334 in saprolite, 584 measurements in transition zone, and 370 measurements of hydraulic conductivity in fractured bedrock. The subset of Allen data for the hydrostratigraphic units fall within the range of the overall datasets (Figure 4-4 to Figure 4-7). There is variation between the geometric mean calculated from the total datasets compared to the geometric mean calculated from the Allen specific datasets. For example, the geometric mean for transition zone hydraulic conductivity at Allen (1.4 ft/d) is approximately twice the geometric mean calculated from the total dataset (0.7 ft/d) and the geometric mean for bedrock at Allen (0.02 ft/d) is an order of magnitude lower than the geometric mean for the total bedrock dataset (0.2 ft/d). Based on this compilation of measurements from multiple sites as well as the Allen site, the mean hydraulic conductivities for the hydrostratigraphic units are approximately 2 ft/d for ash, 1 ft/d for saprolite and transition zone, and 0.2 ft/d for fractured rock. The baseline hydraulic conductivities for the different hydrostratigraphic units were adjusted during calibration to provide the best fit to the data. After calibration, the model -wide baseline hydraulic conductivity for ash in layers 6-11 is 2 ft/d; layers 1-3 were assigned a high hydraulic conductivity of 300 ft/d to represent no ash for the pre -decanted condition; layers 4-5 that represent the top of the present ash surface was given a conductivity of 10 ft/d to represent loose materials on top of the ash and to better match field observations. During calibration the baseline hydraulic conductivity values given above were adjusted to improve the model fit. The calibrated baseline hydraulic conductivity of saprolite is K =1 ft/d, and the transition zone hydraulic conductivity is K = 2 ft/d. The calibrated baseline hydraulic conductivity value for the fractured rock is K = 0.075 ft/d. A baseline value of K = 0.005 ft/d was used for the lower bedrock. This is consistent with the low end of values estimated using slug tests in fractured rock (Figure 4-7). The hydraulic conductivities of heterogeneities range over two to three orders of magnitude in all of the hydrostratigraphic units to improve the fit between the simulated and observed heads (Figure 5-1 to Figure 5-5 and Table 5-2). Page 5-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina A zone of increased hydraulic conductivity in the saprolite and transition zone (Zones #12 through #16 in Figure 5-2 and Figure 5-3 and Table 5-2) is inferred to occur approximately along the axis of the north drainage in the RAB (Figure 1-1). Hydraulic conductivities in this zone are 3 times to 8 times greater than baseline values. Another heterogeneity is inferred to occur north of the RAB between the "Low pH Region" and the coal pile (Figure 5-2a through Figure 5-5c). Heads in this area, including in well clusters CCR-3, CCR-4, CCR-5, CCR-6, and GWA-6 have a strong downward gradient. The heterogeneity structure includes a low hydraulic conductivity zone that extends from southeast of the CCR-6 well cluster to the northwest and wraps around the RAB along a structural high between the discharge canal and the RAB (Figure 5-1a through Figure 5-1c and Table 5-2). The easternmost portion of this structure extends into the transition zone (Figure 5-2a , Figure 5-2b, and Table 5-2). Below this low hydraulic conductivity zone is a relatively high hydraulic conductivity zone in the fractured and lower bedrock that extends from well clusters CCR-3, CCR-4, CCR-5, CCR-6, and GWA- 6, northeast to Lake Wylie (Figure 5-4a to Figure 5-5c and Table 5-2). The lower hydraulic conductivity region in the saprolite extends further west and southwest along the structural ridge to GWA-16 and GWA-19. Other heterogeneities were inferred below the east dike in the AAB and in the uplands south of the AAB during calibration. The heterogeneous structure in the saprolite includes hydraulic conductivities 2 times to 9 times greater than baseline below the dike trending north to south, and a region of decreased hydraulic conductivities along the uplands south of the AAB trending approximately west-southwest from the dike (Figure 5-2). Zones where hydraulic conductivity is greater than baseline in the bedrock are inferred to be locations of connected fractures (Figure 5-4 and Figure 5-5). The resulting distribution of hydraulic conductivity creates good matches to both observed heads and concentrations. The calibrated flow model has a mean head residual of 0.09 feet and a root mean squared head residual of 1.82 feet. The total span of historical average head ranges about 77 feet, from approximately 566 feet to 643 feet. Using this range to normalize the residual gives a normalized root mean square error of 0.024 (2.4 percent). A comparison of the observed and simulated hydraulic heads is listed in Table 5-1, and the observed and simulated heads are cross -plotted in Figure 5- 6. Most of the residuals between predicted and observed heads are less than 4 feet, one residual is between 4 feet and 8 feet, and one residual (well CCR-3S) is greater than 8 feet. Page 5-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina The calibrated flow model has the following volume rate balance: Volume Rate Balance in Steady -State Model in ft3/d1 Feature Input Output General Head 2,207,313 2,124,493 Recharge 314,607 0 Wells 0 10,103 Septic field 6,653 0 Drains (streams) 0 393,977 Total 2,528,573 2,528,573 Difference In - Out = 0.00 Notes• 1. Cubic feet per day = ft3/d The difference between the input and output rates is less than 0.01 ft3/d, which is a volume balance error of less than 10-6. This small volume balance error confirms that a valid solution to the head distribution has been obtained. The major input to the model is from general head boundary with a lesser amount from recharge. General head boundaries generate input around the outer boundary of the model, but this has no effect on the vicinity of the ash basins. The flow output is mainly to general head boundary with a lesser rate discharging to drains. The major general head boundary is Lake Wylie and the South Fork, and the drains represent streams. Less than 0.4 percent of the water input is removed through wells, according to the model. The calibrated model predicts the highest hydraulic heads, approximately 640 feet, occur along the groundwater divide west of the AAB. The second highest heads occur below primary pond 2 where the stage of the pond is held at 639.4 feet (Figure 5-7). The hydraulic heads below the pond are slightly lower than in the pond because of a downward vertical head gradient. A regional groundwater divide occurs west and upgradient of the ash basins, according to the results of the model (Figure 5-8). The divide separates areas where groundwater discharges to the east into Lake Wylie or streams that discharge into Lake Wylie, from groundwater that discharges to the west and north to the South Fork or discharge canal or streams that discharge into the South Fork. The regional groundwater divide trends to the west of the waste boundary along South Point Road to the west of the RAB. The divide curves to the east at the northern portion of the RAB and cuts through a small Page 5-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina portion of the northwestern section of the RAB (Figure 5-8). West of the AAB the regional divide trends to the east and crosses the waste boundary in a small region of the southwestern most portion of the AAB (Figure 5-8). A local groundwater divide occurs within the AAB, according to the simulations (Figure 5-8). The local divide extends roughly east -west along the topographic high between the North and South drainages and beneath primary pond 2. Groundwater on the north side of the local divide flows toward the RAB and some discharges to the drainage canal located between the AAB and RAB and the remainder discharges to Lake Wylie east of the RAB. Groundwater on the south side of the divide stays within the AAB footprint and discharges to Lake Wylie east of the AAB or flows southeast out of the AAB and discharges to Lake Wylie southeast of the AAB. This local divide is primarily due to the elevated heads in the primary ponds which were maintained prior to decanting. Groundwater flow directions are commonly inferred from hydraulic head contours. Where hydraulic conductivity is isotropic in the horizontal plane and uniform, the groundwater flow direction will be parallel to, and in a direction opposite from the horizontal hydraulic head gradient vector. This implies that the groundwater flow direction is perpendicular to hydraulic head contours where the assumption of isotropic and uniform hydraulic conductivity is valid. In fractured rock, it is widely recognized that hydraulic conductivity is rarely uniform and it can commonly be idealized as anisotropic. Nevertheless, it is common to use hydraulic head contours to estimate the groundwater flow direction, which implies that the effects of anisotropy and heterogeneity are small compared to other uncertainties. Therefore, this approach was used for estimating groundwater flow directions in the saprolite. According to the simulation, the flow field in the saprolite is similar to flow within the transition zone and upper portions of the fractured bedrock system. The distribution of hydraulic heads in the saprolite implies that groundwater flow in the RAB is predominantly to the east. A local wet area in the western most finger of the RAB creates a small local sink that perturbs flow directly around it (Figure 4-9 and Figure 5-8). Flow is generally outward from the AAB to the north toward the RAB, to the east toward Lake Wylie, and to the southeast. Groundwater flow directions along the eastern side of the Site are to the east where groundwater is inferred to discharge to Lake Wylie. Groundwater is inferred to flow to the southeast along the southern side of the Site. Groundwater is inferred to flow to the northeast along the northern side of the Site in the vicinity of the ash basins. Page 5-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Groundwater flow directions are of particular interest along the western side of the Site due to the high density of former water supply wells there. The groundwater divide is near to and crosses the waste boundary in the southwestern corner of the AAB (Figure 5-8). Hydraulic head gradients near the divide are small so the horizontal groundwater flow rates are expected to be small. A small flow rate could limit the travel distance of COIs, so the effects on wells west of this region are uncertain based on inferred flow direction alone. Boron concentrations in monitoring wells between the AAB waste boundary and water supply wells to the west are less than the Site background level of 50 µg/L, and the former water supply wells also show no boron concentrations greater than background level. These observations as well as results from the calibrated transport model discussed in this report indicate that boron concentrations greater than the 02L standard have remained within the compliance boundary in this area. Another region of interest is the northwestern region of the RAB where the simulation predicts regional divide crosses a portion of the RAB (Figure 5-8). Flow directions inferred from simulated hydraulic heads suggest flow in this region is in a east- northeast direction away from all public or private supply wells and into Duke Energy property. Inferred flow directions indicate water from within the waste boundary flows north and discharges to the discharge canal on Duke Energy property (Figure 5-8). The domestic and public water supply wells shown in Figure 4-10 are included in the model, but only the public supply wells have a discernable effect on the hydraulic heads in Figure 5-8. The screens of the public supply wells were assumed to extend from the top of fractured bedrock (layer 17) to the total depth of the well. Public supply wells were simulated by applying well boundary conditions at the bottom of the screen and by increasing the hydraulic conductivity in overlying cells to 10 ft/d up to layer 17. Flow budget analysis shows that the simulated flow rate is consistent with the reported flow rates. Only one public supply well is included in the pre -decanted conditions model because three of the four wells were decommissioned in September 2018. The public supply well causes drawdown near the South Fork, which creates closed contours in the hydraulic head distribution near the western edge of Figure 5-7. The effect of the private supply wells on the head contours are undetectable on the map. The reason for this is because the net rate at which water is removed by the domestic wells (the difference between the pumping rate of 280 gal/day and the septic return of 263 gal/day) is small. Based on an average recharge rate of 0.0019 ft/day, each domestic well will capture recharge over approximately 1200 ft2, which is approximately 10 m x 10 m. The domestic wells have a small capture radius based on these assumptions. Page 5-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina A water balance for the vicinity of the ash basin was determined from the results of the calibrated model. The water budget analysis identified a local groundwater flow system in the vicinity of the ash basins. The ash basin groundwater flow system is assumed to be bounded by a groundwater divide west of the ash basins, by the southern boundary of the AAB, by the northern boundary of the RAB, and by Lake Wylie in the east (Figure 5-9). This boundary was defined to determine the total groundwater flow in and out of the ash basins. This includes inflow from a region upgradient from the ash basins, and outflow through the dam and to the northeast toward the coal pile. Zones were defined within GMS, and the Zone Budget tool in MODLFOW was used to determine components of the water balance. Figure 5-9 shows the control volume used to conduct the water balance. The results indicate that the ash basin ponds act as a source and sink in the groundwater flow system with a net input to the groundwater flow system of 273 gpm, which is the largest input to the groundwater flow system in the water balance. The next largest inputs into the system are recharge to the watershed outside of the ash basin (57 gpm), recharge to the RAB (41 gpm), and recharge to the AAB (40 gpm). Discharge in the groundwater flow system includes discharges to wet areas and streams outside of the ash basin (27 gpm), flow to wells outside of the ash basin (1 gpm), discharges to wet areas in the ash basin (39 gpm), and flow from the ash basin groundwater flow system to the surrounding groundwater flow system. The primary flows to the surrounding groundwater include flow through and under the dam (293 gpm), flow to the northeast towards the coal pile (25 gpm), flow to the southeast out of the AAB (17 gpm), and flow north from the RAB to the discharge canal (5 gpm). The water balance for pre -decanting conditions is summarized in Table 5-3. 5.2 Flow Model Sensitivity Analysis A parameter sensitivity analysis was performed on the calibrated model by systematically increasing the parameters by a factor of 2x and decreasing them by a factor of 0.5x and then recalculating the heads and the NRMSE values (Table 5-4). The baseline hydraulic conductivity values and recharge rate, which are the primary hydraulic parameters, were varied in this study. The NRMSE of the flow model showed the highest degree of sensitivity to the regional recharge and showed moderate sensitivity to the hydraulic conductivities of the saprolite, transition zone, and lower ash. The NRMSE was only weakly sensitive to the hydraulic conductivities of the upper ash and the fractured and competent bedrock. Page 5-7 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 5.3 Historical Transport Model Calibration The transient flow model used for transport simulations includes three steady-state head fields: one that represents the period when the RAB was in operation (1957-1973); one that represents the period when the AAB was in use (1973-2009); and one that represents when the recharge was reduced in the double -lined RAB Ash Landfill while the AAB was still in operation (2009-present). The model was set up so that the three steady-state head simulations were used in a single transient transport simulation. The model allows the boundary conditions in the head simulations to change with time, but it requires that the type of boundary conditions specified at a particular location remains unchanged. The flow model specified the recharge on the RAB and the head in the AAB in order to simulate the pre - decanting Site conditions. A recharge value of 0.0029 ft/d was used in the RAB during the initial period (1957-1973). This value is greater than the ambient recharge (0.0019 ft/d) and the larger value was used to simulate the increased recharge that would occur during sluicing in the RAB. The recharge at the RAB was decreased to ambient values when sluicing stopped in 1973, and it was decreased further in the landfill footprint when the landfill was created in 2009. The hydraulic head in the AAB was maintained at its pre -decanting level throughout the simulation. This overestimates the head in the AAB during the period 1957-1973, and it might underestimate the head in the AAB at some points during operation. COI concentrations in ash were assumed to be zero in the AAB from 1957-1973 because the basin was not in operation at this time. COI concentrations were assumed to increase to the values used for calibration in 1973. These values are maintained from 1973 to 2020. COI concentrations in the RAB are assumed to be constant until 2020 and equal to the values determined through calibration. Sulfate and TDS concentrations within the coal pile source area are also assumed to be constant until 2020 with values determined through calibration. The source concentration in the ash basin and coal pile area are the primary calibration variable in the simulation. The initial source concentrations in the ash basins were based on COI concentrations from wells located within ash. COI concentrations in ash pore water are assumed to be representative of zones around the wells, which creates zones of source concentrations throughout the ash basins. The source concentrations were further modified with additional heterogeneities both laterally and vertically within the ash to obtain better fits to COI concentration data in monitoring wells outside of the ash basin. The source concentration in the coal pile source area was similarly adjusted to obtain better fits to COI concentrations in nearby monitoring wells. Page 5-8 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina This calibration process resulted in source zones with concentrations as shown in Figure 5-10 through Figure 5-12 and Table 5-5. As the transport model was calibrated, it was necessary to adjust some aspects of the flow model in order to reproduce the observed COI distribution. This primarily included adjusting the distribution of hydraulic conductivity under the ash. The Ka value is also considered as a calibration variable in the transport simulation. Ka values were adjusted to help predict the boron concentration data near the CP-5 well cluster in the saprolite, transition zone, and upper fractured bedrock and near the AB-10 well cluster in the bedrock. The Kd values in these areas were decreased by up to an order of magnitude to increase boron transport in these regions. Adjusting Ka values had an effect on the boron distribution in these areas; however, adjusting source concentrations and hydraulic conductivity were more effective calibration tools for improving the fit of the simulation. Results of the calibrated transport simulation concentrations reasonably match most of the observed COI concentrations obtained through the first quarter of 2019. The normalized root mean square error (NRMSE) for boron is 0.043 (4.3 percent), using the concentration of 8,470 µg/L at well AB-21PWA as the normalizing factor (Table 5-6a). The NRMSE is 0.064 (6.4 percent) for sulfate, using a concentration of 2,200 milligrams per liter (mg/L) at well CCR-6S for normalization (Table 5-6b). The NRMSE is 0.070 (7.0 percent) for TDS, using a concentration of 3,400 mg/L at well CP-2D for normalization (Table 5-6c). The calibrated maximum concentrations of boron, sulfate, and TDS in all non -ash layers are shown in Figure 5-13a through Figure 5-13c. Concentrations that are an exact match in Table 5-6a through Table 5-6c are from wells in the ash basin where concentrations were set as boundary conditions in the model. Some of the observation wells where COIs were detected are in areas where the predicted concentration gradients are steep (beneath or adjacent to the ash basins, for example), so small changes in location similar to the dimension of a grid block result in significant changes in concentration. This is one factor that explains the differences between predicted and observed concentrations. 5.4 Transport Model Sensitivity Analysis A parameter sensitivity analysis was conducted to evaluate the effects of Ka on the NRMSE. Kd is assumed to be uniform across each grid layer and to vary with depth, as described in Section 4.6. The sensitivity analysis was performed on the calibrated transport model by systematically increasing and decreasing COI Kd values by a factor of 5 from their calibrated values (Table 5-7a through Table 5-7c). The model was then Page 5-9 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina run using the revised Kd values, and the NRMSE was calculated and compared to the NRMSE for the calibrated model. The calibrated transport model simulates COI concentrations with NRMSE values of 4.3 percent for boron, 6.4 percent for sulfate, and 7.0 percent for TDS (Table 5-6a through Table 5-6c). Decreasing the boron Kd by multiplying by a factor of one -fifth increases the NRMSE to 4.6 percent and increasing the boron Kd by 5 times increases the NRMSE to 4.8 percent (Table 5-7a). Decreasing the sulfate Kd by multiplying by a factor of one - fifth increases the NRMSE to 7.0 percent and increasing the sulfate Kd by 5 times increases the NRMSE to 6.9 percent (Table 5-7b). Decreasing the TDS Kd by multiplying by a factor of one -fifth increases the NRMSE to 7.8 percent and increasing the TDS Kd by 5 times increases the NRMSE to 7.6 percent (Table 5-7b). The sensitivity analysis results indicate that the Kd values used for boron, sulfate, and TDS are near optimal values. It also suggests that the average difference between simulated and observed COI concentrations is only moderately affected by changes in the Kd values. Page 5-10 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 6.0 PREDICTIVE SIMULATIONS OF CLOSURE SCENARIOS The calibrated model was used to predict COI distributions in the future. This process includes simulating the interim (post -decanting) conditions during decanting and construction, conditions following closure, and effects of potential corrective actions to achieve 02L compliance. The closure actions include a closure -in -place option that involves regrading and covering ash with a low permeability cap, and a closure -by - excavation option that involves excavating and placing ash in an on -site landfill. The potential corrective action includes a remediation system that uses hydraulic control with extraction wells and clean water infiltration wells. The simulation of post -decanted conditions involves accounting for transport from the present to the time when the closure action implementation has begun. This involves simulating the lowering of the water level by decanting the AAB. Decanting of the AAB began in June 2019 and is estimated to be completed by June 2020. The post - decanting model begins in 2020 and runs until implementation of the closure options is expected to be completed. The predicted COI distributions from the post -decanting model at the time of closure are used as the starting COI distributions for the closure simulations. Closure construction activities are expected to take several years after decanting is completed. Closure -in -place construction is planned for completion by 2029. Closure - by -excavation is planned for completion by 2042. The distribution of recharge, locations of drains, and distribution of material were modified to represent the different closure actions. The hydraulic head distribution was recalculated and transport was simulated for each case. The closure action changed the hydraulic head in the vicinity of the ash basins as the engineered designs interacted with the hydrogeological conditions. This interaction altered the groundwater flow and the transport of dissolved compounds. The compliance boundary for the two closure actions is assumed to be identical to the current compliance boundary. The closure simulations were conducted without corrective action to predict the change in COI concentrations and distribution due to natural attenuation for each of the closure options. These simulations were used to evaluate the effectiveness of monitored natural attenuation (MNA) remediation strategies. The corrective action simulation begins during the post -decanting period and runs until after the two closure options are completed. Assuming implementation in the year 2020, the remediation system in the corrective action simulation was designed to reach 02L Page 6-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina compliance by approximately the end of 2029 (or approximately 10 years following implementation). 6.1 Interim (Post -Decanted) Models with Active Ash Basin Decanted (2020-2029 or 2020-2042) The Interim period from the present to the completion of closure action construction were simulated to determine the initial conditions for the closure action simulations. Simulations began by extending the analysis of pre -decanting conditions to June 2020. The simulations of pre -decanting conditions are outlined above. The interim scenario simulations begin at year 2020 and assume that the sluicing stops and the AAB is decanted. After sluicing is stopped and the AAB is decanted, it is expected that water levels in the ash basin will drastically lower. The general head boundaries used for the primary ponds, ponds in the western AAB, and internal canal system in the simulation are converted to drains. This allows these features to remove water from the system but does not maintain the elevated hydraulic heads created by sluicing. Observed water levels in these features decreased rapidly after discharge to the system was stopped in February 2019 and are expected to be dry or mostly dry after decanting is completed. Some water may remain in these features intermittently due to direct precipitation, storm water runoff, and groundwater discharge. Decanting is represented by using a "drain" to hold the head at a maximum of 615 feet in the impoundment area in the southeast portion of the basin. This elevation is slightly above the expected elevation of ash in the bottom of the pond. The ambient recharge rate of 0.0019 ft/d was assumed to occur uniformly over the entire AAB. Water will discharge into the ash during the interim period. It is assumed that water will discharge to the pond and canal systems and that drains may be constructed within the basin to capture discharging water (Figure 6-1). The concentration of boron in the recharge was assumed to be zero. Transport was simulated during the interim period using initial concentrations from the historical transport simulation for year 2020. Kd values were unchanged. COI concentrations in the ash basin were allowed to vary with time. The time period the interim model runs depends on the closure scenario. The interim model was ran for approximately 22 years (until June 2042) for the closure -by - excavation scenario and for approximately 9 years (until April 2029) for the closure -in - place scenario. These times were based on AECOM's estimated times for closure (AECOM 2019a, AECOM 2019b). Potential variance in closure start and completion dates presented in the groundwater model is inconsequential, as it does not produce substantial changes in the results of the simulations. Page 6-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Results The hydraulic head drops throughout much of the AAB after sluicing stops and decanting is completed. The head drops approximately 25 feet in saprolite beneath the center of primary pond 2, from 639 feet during pre -decanting conditions to approximately 614 feet during post -decanted conditions. The head drops approximately 42 feet in saprolite beneath the center of primary pond 3, from 632 feet during pre -decanting conditions to approximately 590 feet during post -decanted conditions. During pre -decanting conditions, the horizontal hydraulic head gradient is relatively flat under the ash basin and is steep under the dam. Under post -decanted conditions, the gradients become more uniform under the ash basin and dam and ranges from about 0.006 feet per foot (ft/ft) to 0.06 ft/ft (Figure 6-1). Hydraulic head contours are relatively straight and parallel to the shore of Lake Wylie, indicating the groundwater flow direction is relatively uniform to the east (assuming the hydraulic conductivity is isotropic; Figure 6-1). The regional groundwater divide near the western portion of the AAB is similar under post -decanted conditions compared to pre - decanted conditions (Figure 6-2). During the interim period, discharge through and under the dam is reduced from approximately 293 gpm to 113 gpm and flow toward the coal pile is reduced from approximately 25 gpm to 19 gpm. The water balance for decanting conditions is summarized in Table 6-1. The model included a "drain" boundary condition set to 615 feet in the southeast impounded area (Figure 6-1), but the head drops below this level as the hydrologic system re -equilibrated in the absence of sluice water input. This suggests that once sluicing is stopped, it will cause the water table to drop below the level of ash in portions of the basin. Decanting will shorten the time to remove water from the basin. However, some areas along the native perennial streams may remain saturated. Results of the transport simulation show that the distribution of COIs at concentrations greater than the 02L standards vary slightly during the interim period (Figure 6-3 and Figure 6-4) compared to pre -decanting conditions (Figure 5-13). The 02L standard is 700 µg/L for boron, 250 mg/L for sulfate, and 500 mg/L for TDS. In year 2029, at the time of closure -in -place completion, the extent of the boron plume has reduced slightly beyond the compliance boundary north of the northeast corner of the RAB compared to pre -decanting conditions, but it is unchanged elsewhere (Figure 5-13a and Figure 6-3a). The extent of the sulfate (Figure 6-3b) and TDS (Figure 6-30 plumes in 2029 are roughly the same as the extent of sulfate (Figure 5-13b) and TDS (Figure 5-13c) plumes under pre -decanting conditions. The primary difference between the sulfate and TDS plumes in 2029 compared to the sulfate and TDS plumes under pre -decanting conditions is that Page 6-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina concentrations within the extent of the plume are slightly reduced because of natural attenuation mechanisms. At the time of closure -by -excavation completion (year 2042) the concentrations in the sulfate and TDS plumes are further reduced in the main plumes near the coal pile (Figure 6-4b and Figure 6-4c) compared to pre -decanting conditions (Figure 5-13b and Figure 5-13c) but are still greater than 02L standards. TDS concentrations greater than 02L standards east of the AAB near Outfall 002, which extended beyond the compliance boundary under pre -decanting conditions (Figure 5-13c), have receded behind the compliance boundary (Figure 6-4c). In 2042, the extent of the boron plume beyond the compliance boundary is further reduced (Figure 6-4a) compared to pre -decanting conditions (Figure 5-13a) but remains greater than 02L. 6.2 Closure -by -Excavation with Monitored Natural Attenuation Simulations of the closure -by -excavation scenario use results from the interim scenario at year 2042 for initial conditions. The boundary conditions, recharge, and geometry were adjusted to represent excavation and the simulations were conducted to evaluate how COI concentrations changed with time. The design of the model was based on the most recent AECOM closure designs (Figure 6-5; AECOM 2019a). The compliance boundary remains the same for closure -by -excavation (Figure 6-6). Model Setup The closure -by -excavation scenario assumes that ash within the ash basin (not including ash in the RAB Landfill) is excavated and stored in a new on -site landfill built within the footprint of the AAB (Figure 6-5). Ash layers in the excavated region are given a high hydraulic conductivity (150 ft/d) to simulate removal of ash material. The hydraulic conductivities in the landfills are the same as pre -decanting conditions values. The simulation assumes that outside of the landfills some regrading is done to reestablish drainage in the RAB and to create a drainage system around the new on -site landfill (Figure 6-5 and Figure 6-6). The drainages are simulated as drain boundary conditions (Figure 6-6). It is assumed that the dam east of the ash basins is breached in two places. One breach is east of the AAB at approximately the location of the NPDES Outfall 002 (Figure 6-5). The other breach is in the northeastern corner of the RAB. Retention ponds are located at each of these breaches and water in the ponds is assumed to be maintained at an elevation of 566 feet. The retention ponds are simulated as general head boundaries (Figure 6-6). Recharge on the excavated regions is assumed to be 0.0019 ft/d, the same as the ambient recharge rate on natural surfaces in the watershed. Recharge on the RAB Landfill and Page 6-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina new on -site landfill is assumed to be 10-5 ft/d, and recharge on the dam is maintained at 10-4ft/d. Recharge to the retention ponds is assumed to be zero. Results The hydraulic head drops and the horizontal head gradient becomes more uniform when the closure -by -excavation scenario is implemented compared to the pre -decanting or interim periods. For example, the hydraulic head in the center of primary pond 2 drops from 639 feet during operation to approximately 585 feet during the closure -by - excavation scenario (Figure 6-6). This is an additional 29 feet of head drop compared to the interim conditions. The horizontal hydraulic head gradient ranges from approximately 0.01 ft/ft to 0.04 ft/ft in the AAB and from approximately 0.005 ft/ft to 0.04 ft/ft in the RAB during the closure -by -excavation scenario. The new drainage systems in the RAB and AAB perturb head contours and are gaining along some reaches (Figure 6-6). In the gaining reaches, it is expected that drainages will receive groundwater discharge as well as storm flow. Based on the simulation, the RAB drainage system, which includes a small section that originates in the AAB, removes approximately 71 gpm, and the AAB drainage system removes approximately 31 gpm. The retention ponds can behave as both sinks and sources for groundwater. The simulation shows that with a maintained water level average of approximately 566 feet, the RAB retention pond removes approximately 17 gpm and the AAB retention pond removes approximately 19 gpm from the groundwater system. The pattern of the groundwater flow changes in response to the newly developed drainage system and recharge distribution (Figure 6-6). One of biggest changes is the shift in the regional groundwater divide under the closure -by -excavation scenario. The groundwater divide moves approximately 700 feet to the west and no longer crosses the AAB (Figure 6-6). Groundwater flow directions are eastward across the compliance boundary toward the Site along the western portion of the AAB during closure -by - excavation (Figure 6-6). In general, groundwater flows in the excavated ash basins are east toward Lake Wylie and toward the gaining portions of the drainages (Figure 6-6). Distribution of Boron Boron concentrations greater than the 02L standard (700 µg/L) beyond the compliance boundary only occur along the eastern side of the site at the time of closure -by - excavation (year 2042) (Figure 6-4a). Boron concentrations greater than 02L in saprolite occur along the entire eastern side of the Site. Boron concentrations greater than 02L in the underlying bedrock occur in the southeastern portion of the AAB near the current NPDES Outfall 002 and extend down approximately 200 feet according to the simulations. The simulations also indicate that boron concentrations greater than 02L in Page 6-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina bedrock occur in the northeastern corner of the RAB between well clusters GWA-5 and CP-6 and extend down 110 feet into the upper fractured bedrock. After closure is implemented, the extent of boron at concentrations greater than 02L standards beyond the compliance boundary begins to recede. By year 2100, boron concentrations greater than 02L only occur in three places along the compliance boundary, including the two locations with bedrock boron concentrations greater than 02L and a location just east of the primary ponds (Figure 6-7b). Boron concentrations greater than 02L remain persistent in these three areas, slightly above the 02L standard, until approximately year 2200 (Figure 6-7c,d). In year 2200, the only boron concentrations greater than 02L occur east of the AAB near Outfall 002 and where concentrations greater than 02L standards occur in saprolite down to upper fractured bedrock. The simulation was conducted until year 2500 at which time there is still a small patch of boron with a maximum concentration of approximately 900 µg/L beyond the compliance boundary, slightly east of well cluster AB-10 below Lake Wylie in the upper saprolite. Distribution of Sulfate and TDS At the time of closure -by -excavation completion (year 2042), the only location where sulfate is greater than the 02L standard beyond the compliance boundary occurs north of the RAB (Figure 6-4b). TDS concentrations greater than the 02L standard beyond the compliance boundary occur north of the RAB and east of the AAB near Outfall 002 (Figure 6-4c). The sulfate and TDS plumes north of the RAB extend approximately 1,400 feet north of point 3 (Figure 6-10) at the compliance boundary within the footprint of the Station power block. The maximum concentrations of sulfate and TDS occur below and downgradient of the coal pile and the Low pH Region source areas. Figures 6-8a through Figure 6-9d show the progression of the sulfate and TDS plume through time. TDS concentrations east of the AAB decrease to below the 02L standard beyond the compliance boundary by approximately year 2085. Sulfate and TDS concentrations greater than the 02L standard persist beyond the compliance boundary north of the RAB until approximately year 2340. Time Series Five points were identified to summarize transient concentrations in the vicinity of the compliance boundary (Figure 6-10). Point 1 is located in the southwestern corner of the AAB and was chosen because it lies along a potential pathway to the former domestic wells. Point 2 is located on the eastern side of the AAB, near Outfall 002, and was chosen because of the persistent boron in this area. Point 2a is located approximately 300 feet south of Point 2 and was chosen because it characterizes the highest TDS and Page 6-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina sulfate concentrations in this area. Point 3 is north of the RAB and located along the flow path from the low pH area to the coal pile. Point 4 is in the northeastern corner of the RAB and was chosen because of the persistent boron in this area. Time series of the maximum boron in all layers were plotted to be consistent with previous figures. Model results indicate that at Point 1 maximum boron concentrations are less than the Site background value, 50 µg/L, throughout the simulation (Figure 6-11). Sulfate and TDS concentrations at Point 1 are near or less than Site background values for sulfate and TDS (Figure 6-12 and Figure 6-13). Maximum boron concentrations at Point 2 increase to greater than the 02L standard shortly after the AAB is put into operation (Figure 6-11 and Figure 6-13). Boron concentrations reach a maximum of approximately 1930 µg/L by 2020 and remains at that concentration until about 2025. Maximum boron concentrations at Point 2 begin decreasing around 2025 and concentrations at Point 2 drop to less than the 02L standard around 2300 (Figure 6-11). The simulation shows that boron concentrations east of this point in saprolite below Lake Wylie remain greater than 02L standards until at least year 2500. Maximum TDS concentrations at Point 2a reach a maximum of approximately 620 mg/L around 2029 and fall to less than the 02L standard between 2050 and 2060 (Figure 6-13). Sulfate concentrations at Point 2a are never greater than 02L standards (Figure 6-12). Boron concentrations at Point 3 reach a maximum of approximately 400 µg/L but are never greater than 02L standards (Figure 6-11). Maximum sulfate and TDS concentrations at Point 3 are both greater than 02L standards at the start of the simulation because the point is located in a source zone (the coal pile) which is held at a constant concentration until decanting begins. These concentrations begin decreasing as soon as decanting begins and drop to less than 02L standards around year 2150 for sulfate and 2130 for TDS (Figure 6-12 and Figure 6-13). The simulation shows that sulfate and TDS concentrations greater than the 02L standard occur east and downgradient of Point 3 in saprolite down to fractured bedrock beyond these times (Figure 6-8b,c and Figure 6-9b,c). Maximum boron concentrations at Point 4 increase to greater than 02L standards around 1978 and reach a maximum concentration of approximately 1400 µg/L around 2020. Maximum boron concentrations at Point 4 drop to less than 02L standards around 2160 (Figure 6-11). Based on the simulation, maximum sulfate and TDS concentrations reach the 02L standards at Point 4 around 2070. Sulfate and TDS concentrations remain above the 02L standards until around year 2115 (Figure 6-13). Page 6-7 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 6.3 Closure -in -Place with Monitored Natural Attenuation Simulations of the closure -in -place scenario use results from the interim scenario at year 2029 for initial conditions. Boundary conditions, recharge, and geometry were adjusted to represent the closure -in -place design and the simulations were run to evaluate how boron concentrations changed with time. The design of the model was based on the most recent AECOM closure designs (Figure 6-14; AECOM 2019b). The compliance boundary remains the same for closure -in -place (Figure 6-15). Model Setup The closure -in -place scenario is simulated by assuming ash is graded and then capped with a low permeability cover that limits infiltration. The capped area includes the current extent of ash in both the AAB and the RAB. It assumes that ash is removed from the upstream reaches of the North and South drainages and these areas are graded to drain surface water (Figure 6-14). The ash in the AAB will be graded into a pile and surface water drains will be built around the periphery of the pile. Likewise, surface water drains will be constructed in the RAB to recover stormwater. Based on findings at other sites, it was assumed that all the surface water drainage swales were underlain by "drain" boundary conditions approximately 5 feet below the engineered covery system. This type of boundary condition will cause the hydraulic head to be equal to, or less than, the specified head. As a result, the "drain" boundary conditions have no effect at locations where the groundwater table is below the drain. This allows drains to be used in the model to intercept groundwater, but they have no effect on the results where groundwater is lower than the drain. The network of drains used in the model is shown using green lines in Figure 6-15. If this closure option is selected, the discharge from these drains might need to be collected, treated, and discharged per the NPDES permit for a period of time. The landfill in the RAB will be left in place and the area will be covered with a low permeability engineered cap/cover system. A recharge rate of 10-7 ft/d was assumed to characterize flow through the cap/cover, based on expected flow rates through synthetic engineered caps/covers estimated by AECOM. The closure -in -place simulation was started in 2029 and results were exported at intervals of every few years early in the simulation and the interval between the saved results increased with time. This results in finer temporal resolution at early times than later in the simulation, when changes are expected to be slow. Results Hydraulic heads in the closure -in -place scenario drop below the ground surface in most locations. As a result, most groundwater drains used in the model are dry. Recharge Page 6-8 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina through the engineered cap/cover is limited, and most groundwater discharges toward Lake Wylie. The hydraulic head below the center of primary pond 2 is approximately 592 feet. The horizontal hydraulic head gradient ranges from approximately 0.008 ft/ft to 0.04 ft/ft in the AAB and from approximately 0.007 ft/ft to 0.04 ft/ft in the RAB during the closure -by -excavation scenario. Groundwater flow directions are generally eastward under closure -in -place. The groundwater divide near the AAB moves to the west approximately 300 feet compared to pre -decanting conditions and no longer crosses the AAB (Figure 6-15). Groundwater flow directions are eastward across the compliance boundary toward the Site along the western portion of the AAB during closure -in -place (Figure 6-15). Distribution of Boron Boron distribution prior to closure -in -place and under closure -in -place are similar to the distribution before and under closure -by -excavation. Boron concentrations greater than the 02L standard (700 µg/L) beyond the compliance boundary only occur along the eastern side of the Site (Figure 6-3a). Boron concentrations greater than 02L in saprolite occur along the entire eastern side of the site and boron concentrations greater than 02L in bedrock occur near Outfall 002 and the northeastern portion of the RAB. Boron concentrations greater than 02L near Outfall 002 extend down approximately 200 feet based on the simulations and boron concentrations greater than 02L in the northeastern corner of the RAB between well clusters GWA-5 and CP-6 extend down approximately 110 feet. The progression of the boron plume during closure -in -place is similar to the progression during closure -by -excavation. The extent of boron concentrations greater than 02L standards beyond the compliance boundary begin to recede soon after closure and by year 2100 boron concentrations greater than 02L are limited to three locations (Figure 6-16b). In year 2200 boron concentrations greater than 02L only occur east of the AAB Outfall 002 in saprolite down to upper fractured bedrock. Based on the simulation, boron concentrations outside of the compliance boundary decrease to less than 02L standards by approximately year 2300. Distribution of Sulfate and TDS At the time of closure -in -place (year 2029), sulfate concentrations greater than the 02L standard occur north of the RAB and TDS concentrations greater than the 02L standard occur north of the RAB and east of the AAB (Figure 6-3b and Figure 6-3c). Compliance of TDS east of the AAB is met in approximately year 2065. The sulfate and TDS plume north of the RAB extends approximately 1,400 feet north of point 3 (Figure 6-10) with maximum concentrations below and downgradient of the two source areas. Page 6-9 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina The sulfate and TDS plume at years 2050, 2100, 2150, and 2200 are similar for the two closure options. One difference is the plumes under closure -in -place are slightly smaller than the plumes under closure -by -excavation (Figures 6-8a through Figure 6-9d and Figures 6-17a through Figure 6-18d). Compliance for sulfate and TDS under closure -in -place is reached by approximately year 2330 for sulfate and year 2300 for TDS. Time Series Under closure -in -place, maximum boron, sulfate, and TDS concentrations remain less than or near Site background values at Point 1 (Figure 6-19 through Figure 6-21). Under closure -in -place, the maximum boron concentration at Point 2, approximately 1930 µg/L, occurs around year 2020 and concentrations begin receding around 2025 (Figure 6-19). This response is similar to boron concentrations at Point 2 under closure - by -excavation (Figure 6-11). Under closure -in -place the rate of decrease in maximum boron concentrations is slightly greater than the rate in decrease under closure -by - excavation and boron concentrations fall to less than 02L standards around year 2180 for closure -in -place compared to year 2300 for closure -by -excavation (Figure 6-19 and Figure 6-11). Under closure -in -place, the maximum TDS concentration at Point 2a, approximately 600 mg/L, occurs around year 2025 (Figure 6-21). TDS compliance at Point 2a is reached around year 2060 (Figure 6-21). The response of TDS at Point 2a is very similar under both closure scenarios (Figure 6-13 and Figure 6-21). Maximum sulfate concentrations are never greater than 02L standards at Point 2a under closure -in - place (Figure 6-20). Under closure -in -place, boron concentrations at Point 3 reach a maximum of approximately 400 µg/L but are never greater than the 02L standard (Figure 6-19). Maximum sulfate and TDS concentrations at Point 3 are both greater than 02L standards at the start of the simulation and begin decreasing as soon as decanting begins. Sulfate and TDS concentrations at Point 3 drop to less than 02L standards around year 2150 for both COIs (Figure 6-20 and Figure 6-21). The simulation shows that sulfate and TDS concentrations greater than the 02L standard occur east and downgradient of Point 3 in saprolite down to fractured bedrock beyond year 2150 under closure -in -place (Figure 6-17b,c and Figure 6-18b,c). Time series graphs for boron, sulfate, and TDS at Point 3 are similar under closure -in -place and closure -by - excavation (Figure 6-11 through Figure 6-13 and Figure 6-19 through Figure 6-21). At Point 4, the maximum boron concentration increases to greater than 02L around year 1978 and reaches a maximum concentration of approximately 1400 µg/L around year 2020 (Figure 6-19). The maximum boron concentration at Point 4 drops to less than 02L Page 6-10 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina around year 2150 (Figure 6-19). The response of boron under closure -in -place is similar to the response under closure -by -excavation (Figure 6-11 and Figure 6-19). Based on the simulation the maximum sulfate and TDS concentrations at Point 4 are never greater than the 02L standard under closure -in -place (Figure 6-20 and Figure 6-21) 6.4 Corrective Action Simulation The corrective action simulation was conducted to develop a design that could meet 02L compliance by the end of year 2029. Two remediation systems that use hydraulic control were evaluated. One remedial system, alternative 3A, consists of conventional vertical extraction wells and vertical low-pressure clean -water infiltration wells. The second remedial system, alternative 3B, consists of conventional vertical extraction wells, vertical low-pressure clean -water infiltration wells, and horizontal low-pressure clean -water infiltration wells. The simulations assume that portions of the systems will begin operation prior to partial plant decommissioning. The remainder portions of the remedial systems will be constructed and operated as safe access becomes available as Station decommissioning proceeds. The two remedial systems are identical except for in the coal pile area. Alternative 3B was designed to target COIs below the coal pile with horizontal injection wells while the coal pile is still in use. Alternative 3A targets COIs below the coal pile after the coal pile is removed. It is assumed that corrective actions would occur during the period simulated by the Interim model described in Section 6.1 and would be complete at approximately the time closure construction was complete (closure -in -place) or before (closure -by - excavation). As a result, the corrective action simulations are based on the model described for the Interim period, which was modified by including wells in various locations along the east side of the site, near the coal pile area, and in the footprint of the Station power block. Alternative 3A Layout Remediation alternative 3A consists of 87 extraction wells and 76 vertical low-pressure clean -water infiltration wells (Figure 6-25). Sixty-nine extraction wells are completed at the bottom of the transition zone and 18 extraction wells are completed in bedrock. The total flowrate from the extraction wells is approximately 955 gpm. The vertical low- pressure clean -water infiltration wells would injection approximately 380 gpm of clean water. Page 6-11 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Alternative 313 Layout Remediation alternative 3B consists of 87 vertical extraction wells, 48 vertical low- pressure clean -water infiltration wells, and 22 horizontal low-pressure clean -water infiltration wells (Figure 6-26). Sixty-nine extraction wells are completed at the bottom of the transition zone and 18 extraction wells are completed in bedrock. The total flowrate from the extraction wells is approximately 970 gpm. The vertical low-pressure clean -water infiltration wells would inject approximately 225 gpm of clean water and the horizontal low-pressure clean -water infiltration wells would inject approximately 175 gpm of clean water. Extraction and Injection Well Setup The extraction wells are simulated using a vertical series of MODFLOW drain points to simulate wells that extend through multiple model layers. The bottom drain point in the vertical series is given a drain elevation equal to the bottom elevation of the lowest grid cell. The drain elevation for the remainder points in the vertical series are set to the center node elevation of the grid cells. This simulates a condition where the water level is maintained near the bottom of the well, which represents an aggressive, but feasible, pumping design. The drain conductance values are estimated by considering radial flow to a well, which follows the Anderson and Woessner (1992) approach. For a horizontal hydraulic conductivity of K, a well radius of rW, and horizontal and vertical grid spacing of Ax and Az, the drain conductance for a gridblock is computed as: C = E11, 2/TKAz In 0.208Ax rW (2) where EW is the well efficiency, which accounts for well skin effects. A well efficiency of EW = 0.5 was used for extraction wells. Vertical low-pressure clean -water infiltration wells are simulated using the general head boundary condition in MODFLOW, with a conductance calculated the same way, but with EW = 0.25 to account for clogging of the screen and filter pack during injection. Hydraulic heads in the vertical low-pressure clean -water infiltration wells were set 10 to 15 feet above the ground surface, which could be maintained without risk of formation damage. Horizontal low-pressure clean - water infiltration wells are also simulated using the general head boundary condition in MODFLOW. The general head conductance term in the grid blocks where the horizontal low-pressure clean -water infiltration wells are located is assumed to equal the conductance calculated for vertical injection wells in those grid blocks. Hydraulic heads in a horizontal well are assumed to be equal along the length of the horizontal Page 6-12 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina well. The hydraulic head along an individual horizontal well is set to approximately 10 to 15 feet above ground surface above the horizontal well. Results The performance of alternative 3A and alternative 3B are similar. Assuming implementation begins in 2020 (as assumed in the model), both are able to achieve 02L compliance by approximately the end of 2029 (or approximately 10 years following implementation). Both remediation alternatives create a large cone of depression along the eastern side of the Site (Figure 6-25 and Figure 6-26). This head change reverses flow directions east of the compliance boundary and pulls water and COIs back from beneath Lake Wylie. Clean water inflow from Lake Wylie helps improve COI extraction by flushing COIs back toward the extraction wells. Near the coal pile and Station power block, extraction wells create localized capture zones that remove COIs while low-pressure vertical and/or horizontal injection wells create hydraulic head mounds. These mounds create barriers to flow farther north, south and east to the discharge canal. These mounds also improve mass removal by flushing COIs with clean water toward the extraction wells where they are removed. The horizontal low- pressure clean -water infiltration wells in alternative 3B start flushing COIs out from beneath the coal pile sooner than the vertical low-pressure clean -water infiltration wells in alternative 3A. This is the primary difference in the two remediation alternatives. However, alternative 3A is as effective at flushing COIs out from beneath the coal pile by 2029 compared to alternative 3B and is able to achieve this in a shorter period of time. Figure 6-27a through Figure 6-32c shows the progression of the boron, sulfate, and TDS plumes with the two remediation alternatives. The simulations show that both remedial systems are effective at reducing the extent of COI concentrations greater than 02L beyond the compliance boundary prior to the completion of closure -by -excavation and approximately at the time of closure -in -place completion. The simulations predict that after approximately 7 years of operation both remediation alternatives reduce boron concentrations below the 02L standard beyond the compliance boundary. After approximately 10 years of operation both alternatives reduce sulfate and TDS concentrations below the 02L standard beyond the compliance boundary. 6.5 Conclusions Drawn From the Predictive Simulations The following conclusions are based on the results of the groundwater flow and transport simulations: • Predicted future COI concentrations at and beyond the compliance boundary are similar for the closure -by -excavation and closure -in -place scenarios. Page 6-13 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina • The time needed for sulfate and TDS concentrations to reach 02L compliance without active remediation is approximately the same for the two closure scenarios. • The time needed for boron concentrations to reach 02L compliance is predicted to be slightly longer during the closure -by -excavation scenario. • The simulations suggest that the cessation of sluicing and the decanting of the ash basin will reduce COI concentrations at or beyond the compliance boundary. Furthermore the reductions are similar for each closure scenario. • Two remedial system designs have been evaluated that could be implemented using conventional hydraulic control techniques with vertical and/or horizontal wells to rapidly reduce COI concentrations. • The simulations indicate that boron, TDS, and sulfate in groundwater could be less than their respective 02L values beyond the compliance boundary in approximately 10 years following implementation of corrective actions, or by approximately the end of year 2029 if operations begin in year 2020 as modeled. This is before completion of closure -by -excavation or approximately at the time of completion for closure -in -place. This can be accomplished by implementing corrective actions using techniques that are readily available and accepted in the environmental industry. Page 6-14 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina 7.0 REFERENCES AECOM, 2016, Narrative Description of Options Considered (Draft), February 19, 2016. AECOM, 2018, Duke Energy Allen Steam Station 2018 Closure Plan Update (60% Draft), Retired Ash Basin and Active Ash Basin Closure Plan Report. July 27, 2018. AECOM, 2019a, Final Grading Cross Section Layout Plan, Allen Steam Station, Closure Plan for Closure by Excavation (100% Draft), Gaston County, North Carolina, Drawing No. ALN_C901.021.018 Rev. B, October 11, 2019 AECOM, 2019b, Proposed Active Ash Basin Final Cover Grading Plan, Allen Steam Station, 2018 Closure Plan Updates, Gaston County, North Carolina, Drawing No. ALN_C901.021.019 Rev. C, January 30, 2019 Daniel, C.C., Douglas G. Smith, and Jo Leslie Eimers, 1997, Hydrogeology and Simulation of Ground -Water Flow in the Thick Regolith-Fractured Crystalline Rock Aquifer System of Indian Creek Basin, North Carolina, USGS Water -Supply 2341. Daniel, C.C., III. 2001. Estimating ground -water recharge in the North Carolina Piedmont for land use planning [abs.], in 2001 Abstracts with Programs, 50th Annual Meeting, Southeastern Section, April 5-6, 2001: Raleigh, N.C., The Geological Society of America, v. 33, no. 2, p. A-80. Gelhar, L.W. 1986. Stochastic subsurface hydrology from theory to applications. Water Resources Research. V. 22, no. 9, 1355-1455. HDR, 2014a, Allen Steam Station - Ash Basin Drinking Water Supply Well and Receptor Survey. Belmont, NC. September 30, 2014. HDR, 2014b, Allen Steam Station - Ash Basin Supplement to Drinking Water Supply Well and Receptor Survey. Belmont, NC. November 6, 2014. HDR, 2015a, Comprehensive Site Assessment Report Allen Steam Station Ash Basin, Belmont, NC. August 23, 2015. HDR, 2015b, Corrective Action Plan Part 1, Allen Steam Station Ash Basin, Belmont, NC. November 20, 2015. Page 7-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina HDR, 2016a, Corrective Action Plan Part 2, Allen Steam Station Ash Basin, Belmont, NC. February 19, 2016. HDR, 2016b, Comprehensive Site Assessment Supplement 2: Allen Steam Station Ash Basin, Belmont, NC. August 2, 2016. HDR, 2017, Revised Groundwater Flow and Transport Model, Allen Steam Station Ash Basin, Gaston County, NC. April 21, 2017. HDR and SynTerra, 2017. Statistical Methods for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities. HDR Engineering, Inc. and SynTerra Corporation. Langley, W.G. and Oza, S. 2015. Soil Sorption Evaluation, Allen Steam Station. University of North Carolina -Charlotte, NC. October 30, 2015. Langley, W.G. and Kim, D. 2016. Addendum to Soil Sorption Evaluation, Allen Steam Station Gaston County, NC. University of North Carolina -Charlotte, NC. Jan 11, 2016. Legrand, H. 1988. Piedmont and Blue Ridge. Back, W., J. Rosenshein, and P. Seaber, eds. 1988. Hydrogeology: The Geology of North America 0-2: The Decade of North American Geology. Boulder, Colorado: Geological Society of America. Geological Society of America. P. 201-208. McDonald, M.G. and A.W. Harbaugh, 1988, A Modular Three -Dimensional Finite - Difference Ground -Water Flow Model, U.S. Geological Survey Techniques of Water Resources Investigations, book 6, 586 p. Niswonger, R.G.,S. Panday, and I. Motomu, 2011, MODFLOW-NWT, A Newton formulation for MODFLOW-2005, U.S. Geological Survey Techniques and Methods 6-A37, 44-. North Carolina Water Supply and Use, in "National Water Summary 1987 - Hydrologic Events and Water Supply and Use". USGS Water -Supply Paper 2350, p. 393-400. North Carolina; Estimated Water Use in North Carolina, 1995, USGS Fact Sheet FS-087- 97 Page 7-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina Radcliffe, D.E., L.T. West, L.A. Morris, and T. C. Rasmussen. 2006. Onsite Wastewater and Land Application Systems: Consumptive Use and Water Quality, University of Georgia. SynTerra, 2018a, Comprehensive Site Assessment Report Update, Allen Steam Electric Plant, Belmont, NC. January 31, 2018. SynTerra, 2018b, Preliminary Updated Groundwater Flow and Transport Modeling Report For Allen Steam Station, Belmont, NC. November, 2018. SynTerra, 2019, Ash Basin Pumping Test Report, Allen Steam Station, Belmont, NC. January, 2019. Tiedeman, C.R. and P.A. Hseih. 2001. Assessing and open hole aquifer test in fractured crystalline rock. Ground Water, v. 39, n.1, p 68-78. Treece, M.W, Jr., Bales, J.D., and Moreau, D.H., 1990, North Carolina water supply and use, in National water summary 1987 Hydrologic events and water supply and use: U.S. Geological Survey Water -Supply Paper 2350, p. 393-400. Zheng, C. and P.P. Wang, 1999, MT3DMS: A Modular Three -Dimensional Multi - Species Model for Simulation of Advection, Dispersion and Chemical Reactions of Contaminants in Groundwater Systems: Documentation and User's Guide, SERDP-99-1, U.S. Army Engineer Research and Development Center, Vicksburg, MS. Page 7-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina FIGURES LOSURE BY XCAVATION, YEARS AFTER CLOSURE ` r• 1 YEARS AFTER CLOSURE CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE .lord ( DUKE CALER 1,250 GOAPHICS1,2 0 2,500 ENERGY. >L11VA5 N FEET, LEGEND � � � ASH BASIN COMPLIANCE ' DRAWN BY: J. R. KIEKHCK DATE: 12/20/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 BOUNDARY � APPROVED BY: L. DRAGO DATE: 12/20/2019 BORON > 700 ug/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN ASH ' LANDFILL COMPLIANCE BOUNDARY RETIRED ASH BASIN WASTE Terra CHECKED BY: L. DRAGO DATE:12/20/2019 PROJECT MANAGER: C. SUTTELL www.synterracorD.com FIGURE ES -la COMPARISON OF SIMULATED BORON ' BOUNDARY NOTES: ALL BOUNDARIES AREAPPROXIMATE. CONCENTRATIONS IN ALL NON -ASH LAYERS SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS MODELING REPORT COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION SYSTEMIFIPS320BEEN SET 0(NAD83) WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE BELMONT, NORTH CAROLINA LOSURE BY XCAVATION, YEARS AFTER CLOSURE ` r•lw LEGEND ASH BASIN COMPLIANCE BOUNDARY SULFATE > 250 ug/L RETIRED ASH BASIN ASH LANDFILL COMPLIANCE ACTIVE ASH BASIN WASTE BOUNDARY BOUNDARY RETIRED ASH BASIN WASTE - BOUNDARY I YEARS AFTER CLOSURE CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE NOTES: ALL BOUNDARIES ARE APPROXIMATE. SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). (ALE DUKE 1,300 GORAPHICSC1,300 2,600 ENERGY. (IN FEET, >uIVAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 APPROVED BY: L. DRAGO DATE: 12/20/2019 CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerid PROJECT MANAGER: C. SUTTELL www.s nterracor .com FIGURE ES -lb COMPARISON OF SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LOSURE BY XCAVATION, YEARS AFTER CLOSU VW' 1 YEARS AFTER CLOSURE CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE _ 'yip-/r� R .► CALEm- ( DUKE 1,250 GOAPHICS1,2 0 2,500 ENERGY. N FEET, >L11VA5 LEGEND ASH BASIN COMPLIANCE DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 ' BOUNDARY APPROVED BY: L. DRAGO DATE: 12/20/2019 TDS > 500 ug/L RETIRED ASH BASIN ASH CHECKED BY: L. DRAGO DATE: 12/20/2019 ACTIVE ASH BASIN WASTE ' LANDFILL COMPLIANCE synTerra PROJECT MANAGER: C. SUTTELL BOUNDARY BOUNDARY RETIRED ASH BASIN WASTE www.synterracorD.com -'-' BOUNDARY FIGURE ES -lc NOTES: COMPARISON OF SIMULATED TDS ALL BOUNDARIES AREAPPROXIMATE. CONCENTRATIONS IN ALL NON -ASH LAYERS SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS MODELING REPORT COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION SYSTEMIFIPS320BEEN SET 0(NAD83) WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE BELMONT, NORTH CAROLINA .. r LEGEND REFERENCE LOCATION ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY i a.. RAPHIC SC DUKE 580 G580 1,160 NOTES: *"ENERGY. ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) THE LOCATION LABELED "POINT 2A" FOR SULFATEAND TDS WAS CHOSEN TO CAPTURE THE MAXIMUM DRAWN BY: J. EBENHACK DATE: 11/18/2019 CONCENTRATIONS IN THAT REGION. REVISED BY: R. KIEKHAEFER DATE: 12/29/2019 APPROVED BY: L. DRAGO DATE: 12/29/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/29/2019 PROJECT MANAGER: C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE synTerra SYSTEM FIPS 3200 (NAD83). WWW.svnterracorD.com FIGURE ES-2 REFERENCE LOCATIONS USED FOR TIME SERIES DATASETS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA i M M a 2,000 = C-by- R: Point 1 1,800 1 C-by-R: Point 2 ; C-by-R: Point 3 1,500 C-by- R: Point 4 '0 1,400 ==--C-in-P: Point 1 —=—=C-in-P: Point 2 p 1,200 d�% —=—=C-in-P: Point 3 1,000 " �% � _ —--C-in-P: Point 4 — — — 02L 5td = 700 µgf L S00 — — — — — — — — — — — — — _ _ _ _ _ _ _ _ 600 % r D % .� 400 200� R 0 00 m o � o N N � N N ry N m -y N N � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE ES-3a fENJERGY, REVISED BY. SUMMARY OF MAXIMUM BORON IN ALL NON -ASH MODEL LAYERS AS FUNCTIONS CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB OF TIME AT REFERENCE LOCATIONS 1, 2, 3, AND 4 FOR CLOSURE-BY-ECAVATION PROJECT MANAGER: C. SUTTELL AND CLOSURE -IN -PLACE UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION synTerra www.synterracorp.com BELMONT, NORTH CAROLINA Sulfate C-by-R: Point 1 2,000 C-by-R: Point 2a - C-by-R: Point 3 _ C-by-R: Point 4 bb C-in-P: Point 1 __-- C-in-P: Point 2a 0 ---- C-in-P: Point 3 -- -- C-in-P: Point 4 �, � 1,000 w — — — 02L Std = 250 µgf L c� 0 U % Qj +j 500 cn ________________________ rq �c a Ln o L1 C) rl N N N N N N N N rq Year � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE ES-3b fENJERGY, REVISED BY. SUMMARY OF MAXIMUM SULFATE IN ALL NON -ASH MODEL LAYERS AS CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB FUNCTIONS OF TIME AT REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR CLOSURE -BY - PROJECT MANAGER: C. SUTTELL ECAVATION AND CLOSURE -IN -PLACE `10 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION synTerra VAM synterracorp.com BELMONT, NORTH CAROLINA 4,000 1­1 3,500 J to E 3,000 Q 2,500 12 L 2,000 N V 0 1,500 CIS 1,000 TDS ti — C-by-R: Point 1 C-by-R: Point 2a — C-by-R: Point 3 C-by-R: Point 4 ----C-in-P: Point 1 ====C-in-P: Point 2a --=-C-in-P: Point 3 ----C-in-P: Point 4 — — — 02L 5td = 500 µg f L 50o---f__ _________________________ r%- H QD rq LO CD un CD un C) rn CD CD H � � °N° m m rl N rq N r.I r.1 N N r q N Yea r eDUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE ES-3C n ENERGY REVISED BY: SUMMARY OF MAXIMUM TDS IN ALL NON -ASH MODEL LAYERS AS FUNCTIONS OF CAROLINAS CHECKED BY: K. WEBB APPROVED BY: K. WEBB TIME AT REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR CLOSURE-BY-ECAVATION PROJECT MANAGER: C. SUTTELL AND CLOSURE -IN -PLACE UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA SyflTerrd www.synterracorp.com I BORON l h .h" 0 s S 630 \ "S 1 TDS SULFATE ( 1,300 GRAPHIC SC ALE 'DUKE ,300 2,600 4 ENERGY N FEET) CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 APPROVED BY: L. DRAGO DATE: 12/20/2019 CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerrd PROJECT MANAGER: C. SUTTELL www_svntarracnrn_mm s 1 - so s LEGEND 1 VERTICAL EXTRACTION WELLS y ", \,= o ♦ VERTICAL CLEAN WATER INFILTRATION WELLS s�630 ACTIVE ASH BASIN WASTE BOUNDARY s RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY i• .-- RETIRED ASH BASIN ASH LANDFILL WASTE BOUNDARY - - - - HYDRAULIC HEAD (FEET) NOTES: Boron Sulfate ALL BOUNDARIES ARE APPROXIMATE. > 700 Ng/L > 250 mg/L CONTOUR INTERVAL IS 5 FEET. FIGURE SHOWS ALTERNATIVE 3A REMEDIATION SYSTEM TES AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. > 500 mg/L DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83 AND NAVD88). FIGURE ES-4a SIMULATED COI CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA BORON SULFATE s2s �2s o sops sons S9S y N o o u� o S9S i,� s cn,vl c SO ti0 580 �O •a'A l 411 , GO APHIC SCALE,300 TDS i DUKE 1,300 2,600 s, ENERGY CAROLINAS (IN FEET) s S8p' DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 ~ APPROVED BY: L. DRAGO DATE: 12/20/2019 �S CHECKED BY: L. DRAGO DATE: 12/20/2019 ss synTerra PROJECT MANAGER: C. SUTTELL 90 oo� www_svntarrarnrn_rnm LEGEND $ VERTICAL EXTRACTION WELLS s or A VERTICAL CLEAN WATER INFILTRATION WELLS s o's 2 ' HORIZONTAL CLEAN WATER INFILTRATION WELLS s ao sus ACTIVE ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE 7 al BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN ASH LANDFILL r ' . WASTE BOUNDARY HYDRAULIC HEAD (FEET) NOTES: Boron Sulfate ALL BOUNDARIES ARE APPROXIMATE. > 700 Ng/L > 250 mg/L CONTOUR INTERVAL IS 2 FEET. FIGURE SHOWS ALTERNATIVE 3B REMEDIATION SYSTEM TI]S AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. > 500 mg/L DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FI PS 3200 (NAD83 AND NAVD88). FIGURE ES-4b SIMULATED COI CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 313 REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 10 ALLEN STEAM STATION PARCEL LINE s� Ro�U 0 DISCHARGE CANAL OUTFALL 001 I UU 'UYU RETIRED ASH BASIN (�//' ASH LANDFILL CCOMPLIANCE BOUNDARY RETIRED ASH BASIN / WASTE BOUNDARY_ ACTIVE ASH BASIN yr WASTE BOUNDARY a 4qASH =LANDFILL A-" _ II SOUTH DRAINAGE r;. __W_-�S_[o e ASH BASIN COMPLIANCE —BOUNDARY NOTE: WATER FEATURES DEPICTED WITHIN WASTE BOUNDARIES OF THEASH BASINS ON THE 2016 USGS TOPOGRAPHIC MAP DO NOT REPRESENT CURRENT CONDITIONS. THE CONDITIONS DEPICTED ARE SIMILAR TO THOSE SHOWN ON THE 1968 AND 1973 USGS TOPOGRAPHIC MAPS OF THE AREA (1968 WEST CHARLOTTE (1:24000) AND 1973 BELMONT (1:24000). SOURCE: 2016 USGS TOPOGRAPHIC MAP, BELMONT & CHARLOTTE WEST QUADRANGLE, OBTAINED FROM THE USGS STORE AT hftps:Hstore.usgs.gov/map-locator. (' DUKE ENERGY CAROLINAS GASTON COUNTY rg� RETIRED ASH BASIN: ASH LANDFILL BOUNDARY —RETIRED ASH BASIN NPDES OUTFALL 002 So 2 FIGURE 1-1 USGS LOCATION MAP UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA DRAWN BY: B. YOUNG DATE: 05/02/2019 GRAPHIC SCALE REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 i,000 o i,000 z,000 CHECKED BY: L. DRAGO DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 (IN FEET)) PROJECT MANAGER: C. SUTTEL LEGEND SITE FEATURE ACTIVE ASH BASIN WASTE BOUNDARY . RETIRED ASH BASIN WASTE BOUNDARY . ■ ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL WASTE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY • DORS FILLS BOUNDARIES DUKE ENERGY CAROLINAS ALLEN PLANT SITE BOUNDARY O FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. THE MODEL BOUNDARY WAS SET AT A DISTANCE FROM THE ASH BASIN SUCH THAT THE BOUNDARY CONDITIONS DID NOT ARTIFICIALLY AFFECT THE RESULTS NEAR THE ASH BASIN. PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY CAROLINAS. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). DUKE ENERGY CAROLINAS 10 synTerra GRAPHIC SCALE 1,000 0 1,000 2,000 (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL FIGURE 4-1 NUMERICAL MODEL DOMAIN UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA c/� DUKE DRAWN BY: J. EBENHACK ENERGY. REVIS`u CAROLINAS B CHECKED BY: K. WEBB CHECKED APPROVED BY: K. WEBB PROJECT MANAGER: C. SUTTELL ,16' synTerra NN DATE: 12/7/2019 1 FIGURE 4-2 FENCE DIAGRAM OF THE 3D HYDROSTRATIGRAPHIC MODEL USED TO CONSTRUCT THE MODEL GRID UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA www.synterracorp.com �� DUKE DRAWN BY: J. EBENHACK ENERGY REVISED BY: CAROLINAS CHECKED BY: K. WEBB APPROVED BY: K. WEBB PROJECT MANAGER: C. SUTTELL ,16' synTem MASH WSAPROLITE =TRANSITION ZONE W UPPER (FRACTURED) BEDROCK =LOWER BEDROCK DATE:12/7/2019 FIGURE 4-3a COMPUTATIONAL GRID USED IN THE MODEL WITH 3X VERTICAL EXAGGERATION UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA www.synterracorp.com .......... owl. ................................ I ........... ................ ..................................................... ...................................... ....................................... ..................... I I I 11. IN: i 111. 11. U.N., ............................... 111. 111. .. I .. I .. .................................... 1., 11111 IM III .... I I IN 1: 1 .......... 1 .... .......... .... loll .................. i I H H., 11 ........ .1 .1 iciiLt!TlM. E V 1.0 0.8 0.6 0.4 0.2 0.0 Ash Hydraulic Conductivities • All Sites ■ Allen slug test Allen pumpingtest analytical solution Model Number AK 0.001 0.010 0.100 1.000 10.000 100.000 K (ft/d) L!� DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE 4-4 Z ENERGY. REVISED BY: HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN ASH CAROLINAS CHECKED BY: K. WEBB APPROVED BY: K. WEBB AT 14 SITES IN NORTH CAROLINA PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT 4'rlp ALLEN STEAM STATION BELMONT, NORTH CAROLINA synTerra www.synterracorp.com 1 0.8 n m 0 0.6 CL m 0.4 E I 0.2 4 Saprolite Hydraulic Conductivities * All Sites ■ AI len ❑Allen purnpingtest analytical solution Model Number 1.00E-03 1.00E-02 frS DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 ENERGY REVISED B CAROLINAS CHECKED BY: K. WEBB APPROVED BY: K. WEBB PROJECT MANAGER: C. SUTTELL ,11116' synTerra www.synterracorp.com 1.00E-01 1.00E+00 1.00E+01 1.00E+02 (ft d) FIGURE 4-5 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN SAPROLITE AT 10 PIEDMONT SITES IN NORTH CAROLINA UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 1 • 0.8 n 0 0.6 L- IL ICU 4-' 0.4 E 0.2 Transition Zone Hydraulic Conductivities • All Sites ■ AI len • Model Number AM 19 A A& *V Ag 0400 1.00E-06 1.00E-05 1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 K (ft/d) L!� DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE 4-6 Z ENERGY. REVISED BY: HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN THE CAROLINAS CHECKED BY: K. WEBB TRANSITION ZONE AT 10 PIEDMONT SITES IN NORTH CAROLINA APPROVED BY: K. WEBB PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA synTerra www.synterracorp.com �aw E 0.2 • 0 1.00E-05 Upper Bedrock Hydraulic Conductivities • All Sites • AI len * Model Number • elk • • A11W 1.00E-04 1, 00 E-03 1.00E-02 1.00E-01 1.00E+00 1, 00 E+01 1.00E+02 (ft d ) L!� DRAWN BY: J. EBENHACK r ENERGY. REVISED CAROLINAS CHECKED BY: CHECKED BY: K. WEBB APPROVED BY: K. WEBB PROJECT MANAGER: C. SUTTELL ,1116' synTerra DATE: 12/7/2019 FIGURE 4-7 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN FRACTURED ROCK AT 10 PIEDMONT SITES IN NORTH CAROLINA UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA www.synterracorp.com r F a4 J~ LEGEND RECHARGE RATE` 0 ft/d ` DUKE GRAPHIC SCALE 1,100 0 1,100 2,200 ENERGY 0.00001 ft/d CAROLINAS N FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 0.0001 ft/d REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 0.0019 ft/d CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL synTerra www.synterracorD.com FIGURE 4-8 NOTES: DISTRIBUTION OF MODEL RECHARGE ZONES ALL BOUNDARIES AREAPPROXIMATE. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13,2018. AERIAL WAS COLLECTED ON MARCH 30,2018. MODELING REPORT DRAWINGITH A PROJECTION FPS3 00(NAD83) OF NORTH CAROLINA STATE PLANE COORDINATE SYST M ALLEN STEAM STATION BELMONT, NORTH CAROLINA .` -F , Tp Discharge Canal South Fork (Catawba River) Primary Primary Pond 1 Pond 2 Lake Wylie (Catawba River) Primary Pond 3 Ash Basin Ponded Water �� DUKE 1100 GO APHIC SCALE 1,100 2,200 LEGEND ENERGY CAROW. (IN FEET) CHANNELS DRAWN BY: J. EBENHACK DATE: 11/18/2019 STREAMS REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 - SURFACE WATER FEATURES APPROVED BY: L. DRAGO DATE: 12/26/2019 WETLANDS CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra www.synterracorD.com NOTES: FIGURE 4-9 ALL BOUNDARIES ARE APPROXIMATE. MODEL SURFACE WATER FEATURES STREAMS ARE INCLUDED IN THE MODEL AS DRAINS. LAKES, PONDS, UPDATED GROUNDWATER FLOW AND TRANSPORT CHANNELS, AND PONDED WATER IN THE ASH BASIN ARE INCLUDED IN THE MODEL AS GENERAL HEAD ZONES. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER ALLEN STEAM STATION 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE BELMONT, NORTH CAROLINA PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). LEGEND ie PRIVATE SUPPLY WELLS ij� PUBLIC SUPPLY WELLS ACTIVE ASH BASIN WASTE BOUNDARY - - - • RETIRED ASH BASIN WASTE BOUNDARY DUKE GRAPHIC SCALE 1,100 0 1,100 2,200 - ASH BASIN COMPLIANCE BOUNDARY ENERGY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE CAROLI�. (IN FEET) • BOUNDARY DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 DUKE ENERGY CAROLINAS ALLEN PLANT SITE APPROVED BY:L.DRAGO DATE: 12/26/2019 - - - BOUNDARY CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra www.synterracorD.com NOTES: FIGURE 4-10 ALL BOUNDARIESARE APPROXIMATE. LOCATION OF WATER SUPPLY WELLS IN MODEL AREA PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY CAROLINAS. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER MODELING REPORT 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200(NAD83). p BELMONT, NORTH CAROLINA LEGEND HYDRAULIC CONDUCTIVITY ■ ■ s t Nm DUKE 1,100 GRAPHIC SCALE 0 1,100 2,200 FLOW AND TRANSPORT ENERGY 0 N FEET, MODEL BOUNDARY CAROLINAS ■ ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 �� ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.s nterracor .com NOTES: FIGURE 5-la ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY ASH LAYERS 4 AND 5 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTA LE 5-2. FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, MODELING REPORT 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA HYDRAULIC CONDUCTIVITY ■ ■ s #1, 0.03 FLOW AND TRANSPORT ENERGY MODEL BOUNDARY (IN FEET) ■ ■ CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 �� ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.svnterracorD.com NOTES: FIGURE 5-lb ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY ASH LAYERS 6 AND 7 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, MODELING REPORT 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA Ids #2, 0.1 LEGEND HYDRAULIC CONDUCTIVITY ■ ■ s y - GRAPHIC SCALE FLOW AND TRANSPORT % DUKE 1,100 O 1,100 2,200 O ENERGY MODEL BOUNDARY (IN FEET) � ■ ■ ■ ■ ■ CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 �r ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.svnterracorlo.com NOTES: FIGURE 5-1c ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY ASH LAYERS 8 THROUGH 10 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTA LE 5-2. FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, MODELING REPORT 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA #3, 0.3` F. N;f wIN #2, 0.1 ai F r. r, LEGEND HYDRAULIC CONDUCTIVITY ■ a % DUKE GRAPHIC SCALE 1,100 0 1,100 2,200 FLOW AND TRANSPORT ENERGY ■ MODEL BOUNDARY N FEET) ■ CAROLINAS ■ ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ ■ �� REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ WnTerra www.svnterracorD.com NOTES: FIGURE 5-1d ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY ASH LAYER 11 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTA LE 5-2. FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ S ALLEN TEAM STATION DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA -#13, 4.0 #14, 5.0 roa.. LEGEND ^ HYDRAULIC CONDUCTIVITY •, ■ ■ a f� DUKE GRAPHIC SCALE 1,10 O 1,10 2,20 FLOW AND TRANSPORT ENERGY ■ MODEL BOUNDARY N FEET) ■ CAROLINAS ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ �� REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.synterracorio.com NOTES: FIGURE 5-2a ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY SAPROLITE LAYER 12 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTA LE 5-2. FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ S ALLEN TEAM STATION DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA ME LEGEND HYDRAULIC CONDUCTIVITY lF ' ' ■ y - ■ a i DUKE 1,100 GORAPHICSCALE 1,100 2,20 FLOW AND TRANSPORT O ENERGY N FEET) MODEL BOUNDARY CAROLINAS ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 �� APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.synterracorio.com NOTES: FIGURE 5-2b ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY SAPROLITE LAYER 13 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTA LE 5-2. FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ S ALLEN TEAM STATION DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA ■ ■ ■ ■ ■ V^-V' ,^V DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 �� ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.s nterracor .com NOTES: FIGURE 5-2c ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY SAPROLITE LAYER 14 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, MODELING REPORT 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA P LEGEND HYDRAULIC CONDUCTIVITY ■ ■ s FLOW AND TRANSPORT DUKE 1,100 0 1,10o 2,200 MODEL BOUNDARY ENERGY ■ ■ ■ ■ ■ ■ CAROLINAS ® (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 �� ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.synterracorio.com NOTES: FIGURE 5-3a ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY TRANSITION ZONE LAYER 15 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, MODELING REPORT 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA t, LEGEND HYDRAULIC CONDUCTIVITY ■ ■ s #11, 10.0 #7, 3 QFLOW AND TRANSPORT ENERGY MODEL BOUNDARY (IN FEET) ■ ■ CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 �� ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 ■ ■ synTerra PROJECT MANAGER: C. SUTTELL www.svnterracorD.com NOTES: FIGURE 5-3b ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY TRANSITION ZONE LAYER 16 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, MODELING REPORT 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA LEGEND HYDRAULIC CONDUCTIVITY ■ ■ s #13, 5.0 #12, 4.0 #1, 0.001 #4, 0.03 #10, 2.0 gmllT #3, 0.01 14 #1, 0.001 #2, 0.005 #7, 0.1 #9, 1.0 I #6, 0.075 i DUKE 7' 1,10 1,10 2,20 0 FLOW AND TRANSPORT ENERGY MODEL BOUNDARY (IN FEET) CAROLINAS ■ DRAWN BY: 1, EBENHACK DATE: 11/18/2019 ■ REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 �� APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.synterracorio.com NOTES: FIGURE 5-4a ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYER 17 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA LEGEND HYDRAULIC CONDUCTIVITY ■ s #8, 0.5 #12, 4 #1, 0.001 #9, 1.0 #4, 0.03 #9, 1.0 #10, 2.0 mill #3, 0.01 #1, 0.001 TFV, V 5 #2, 0.005 #7, 0.1 #9, 1.0 I #6, 0.075 f�ALE DUKE 1,100 GORAPHICSC1,100 2,20 0 FLOW AND TRANSPORT ENERGY MODEL BOUNDARY (IN FEET) CAROLINAS ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 �� APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.svnterracorlo.com NOTES: FIGURE 5-4b ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYER 18 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA HYDRAULIC CONDUCTIVITY ■ s #13, 5.0 #10, 2.0 #8, 0.5 #12, 4.0 #1, 0.001 #4, 0.03 #3, 0.01 #10, 2.0 - #3, 0.01 #1, 0.001 #2, 0.005 #7, 0.1 #9, 1.0 I #6, 0.075 DUKE u , , 1,10 D 1,10 2,20 FLOW AND TRANSPORT ENERGY 0 N FEET) MODEL BOUNDARY CAROLINAS ■ ■ DRAWN BY: 1, EBENHACK DATE: 11/18/2019 ■ REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 �� APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.synterracorio.com NOTES: FIGURE 5-4c ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYER 19 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELIS FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. EDINTA LE 5-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA #5, 0 V ur 7tV, nJ V V ,r #7, 0.05 <�#l, 0.0005 LEGEND HYDRAULIC CONDUCTIVITY ■ a GRAPHIC SCALE FLOW AND TRANSPORT % DUKE 1,100 0 1,100 2,200 ■ MODEL BOUNDARY ENERGY (IN FEET) ■ CAROLINAS ■ ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 �� ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 ■ ■ WnTerra PROJECT MANAGER: C. SUTTELL www.synterracorio.com NOTES: FIGURE 5-5a ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYER 20 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, MODELING REPORT 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ ALLEN TEAM STATION S DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA #5, 0.02 #4, 0.015 4 LEGEND HYDRAULIC CONDUCTIVITY ■ ■ a DUKE GRAPHIC SCALE 1,10 O 1,10 2,20 ENERGY ■ FLOW AND TRANSPORT CAROLINAS N FEET) ■ MODEL BOUNDARY ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ �� REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ synTerra www.synterracorio.com NOTES: FIGURE 5-5b ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYERS 21 AND 22 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ S ALLEN TEAM STATION DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA #5, 0.02 #4, 0.015 r. LEGEND HYDRAULIC CONDUCTIVITY ■ a a % DUKE GRAPHIC SCALE 1,10 O 1,10 2,20 O FLOW AND TRANSPORT ENERGY N FEET) MODEL BOUNDARY ■ CAROLINAS ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ �� REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ WnTerra www.synterracorip.com NOTES: FIGURE 5-5c ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYER 23 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTA LE 5-2. FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ S ALLEN TEAM STATION DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA #2, 0.005 m #6 LEGEND HYDRAULIC CONDUCTIVITY ■ ■ a a % DUKE GRAPHIC SCALE 1,10 O 1,10 2,20 O FLOW AND TRANSPORT ENERGY N FEET) ■ MODEL BOUNDARY CAROLINAS ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ �� REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ WnTerra www.svnterracorlo.com NOTES: FIGURE 5-5d ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYER 24 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ S ALLEN TEAM STATION DRAWING HAS BEEN SET WITH A COORDINATE SYSTEMFPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA #2, 0.605 i!l .- f LEGEND HYDRAULIC CONDUCTIVITY ■ ■ a iDUKE GRAPHIC SCALE 1,10 O 1,10 2,20 OFLOW AND TRANSPORT ENERGY ■ MODEL BOUNDARY CAROLINAS N FEET) ■ ■ DRAWN BY: J. EBENHACK DATE: 11/18/2019 ■ �� REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 ■ ■ CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL ■ ■ WnTerra www.synterracorio.com NOTES: FIGURE 5-5e ALL BOUNDARIES AREAPPROXIMATE. MODEL HYDRAULIC CONDUCTIVITY ZONES IN ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY FRACTURED BEDROCK LAYERS 25 THROUGH 31 AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC OF TO VERTICAL ANISOTROPY UPDATED GROUNDWATER FLOW AND TRANSPORT FONDUMBERYVALUESAN ARELISEDINTAZONTAL FOR NUMBERED POLYGONS ARE LISTED IN TABLE 6-2. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. �+ S ALLEN TEAM STATION DRAWING HAS BEEN SET WITH A COORDINATE SYSTEM RIPS 200(NAD83).TION OF NORTH CAROLINA STATE PLANE BELMONT, NORTH CAROLINA Computed vs. Observed Values Head 650 640 620 M M 610 2 w 600 CL 590 E D U 580 570 560 L 560 fen DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 ENERGY REVISED CAROLINAS B CHECKED BY: K. WEBB APPROVED BY: K. WEBB PROJECT MANAGER: C. SUTTELL ,16' synTerra www.synterracorp.comL.- r 59 0 600 610 620 64C 650 Observed Heads (ft) FIGURE 5-6 SIMULATED HEADS AS A FUNCTION OF OBSERVED HEADS FROM THE CALIBRATED STEADY STATE FLOW MODEL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA .L-4 1 M, m Si O N0 o os o 0 i� MEN LEGEND ■ HEAD OBSERVATIONS ERROR BARS HYDRAULIC HEAD (FEET) (RESIDUALS) ACTIVE ASH BASIN WASTE BOUNDARY < 4 ft ENERGY . RETIRED ASH BASIN WASTE BOUNDARY . ASH BASIN COMPLIANCE BOUNDARY 4 - 8 ft CAROLINAS N FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 ip synTerra RETIRED ASH BASIN ASH LANDFILL COMPLIANCE • BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY > 8 ft REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL www.synterracorio.com NOTES: FIGURE 5-7 ALL BOUNDARIES ARE APPROXIMATE. CONTOUR INTERVAL IS 5 FEET. HEADS ARE SHOWN PRIOR TO DECANTING. SIMULATED A /+ A �+ �+A HYDRAULIC HEADS IN THE S -PROLITE UNDER RESIDUALS ARE SHOWN AT EACH OBSERVATION POINT AND ARE EQUAL TO PRE -DECANTED CONDITIONS (MODEL LAYER 14) PREDICTED HEAD -OBSERVED HEAD. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. MODELING REPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE ALLEN STEAM STATION PLANE COORDINATE SYSTEM FIPS 3200 (NAD83AND NAVD88). BELMONT, NORTH CAROLINA Fj 1 586 �JI t e< 568 586i� LEGEND HYDRAULIC HEAD (FEET) FLOW WITHIN LOCAL SYSTEM DUKE FLOW OUTSIDE LOCAL SYSTEM GRAPHIC SCALE 1,100 0 1,100 2,200 GROUNDWATER LEAVING LOCAL SYSTEM � ENERGY LOCAL GROUNDWATER DIVIDE REGIONAL GROUNDWATER DIVIDE CAROLINAS (IN FEET) ACTIVE ASH BASIN WASTE BOUNDARY DRAWN BY: J. EBENHACK DATE: 11/18/2019 RETIRED ASH BASIN WASTE BOUNDARY REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 ASH BASIN COMPLIANCE BOUNDARY APPROVED BY: L. DRAGO DATE: 12/26/2019 RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY CHECKED BY: L. DRAGO DATE: 12/26/2019 synTerra PROJECT MANAGER: C. L O FLOW AND TRANSPORT MODEL BOUNDARY www.s nterrterracor .com NOTES: FIGURE 5-8 ALL BOUNDARIES ARE APPROXIMATE. ARROWS INDICATE INFERRED DIRECTION ONLY, NOT MAGNITUDE. SIMULATED GROUNDWATER FLOW SYSTEM IN SAPROLITE CONTOUR INTERVAL IS 2 FEET. HEADS ARE SHOWN IN MODEL LAYER 14 UNDER PRE -DECANTED CONDITIONS (MODEL LAYER 14) PRIOR TO DECANTING. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON MODELING REPORT DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE ALLEN STEAM STATION PLANE COORDINATE SYSTEM FIPS 3200 (NAD83 AND NAVD88). BELMONT, NORTH CAROLINA 0 SgS , f� r 07 57 t. o E rc� R LEGEND CONTROL VOLUME DUKE GRAPHIC SCALE 1,100 1,100 2,200 0 HYDRAULIC HEAD (FEET) ENERGY ACTIVE ASH BASIN WASTE BOUNDARY (IN FEET) CAROLINAS • RETIRED ASH BASIN WASTE BOUNDARY DRAWN BY:J. EBENHACK DATE:11/18/2019 • ASH BASIN COMPLIANCE BOUNDARY REVISED BY: R. KIEKHAEFER DATE: 12/17/2019 = : = APPROVED BY: L. DRAGO DATE: 12/17/2019 RETIRED ASH BASIN ASH LANDFILL COMPLIANCE CHECKED BY: L. DRAGO DATE: 12/17/2019 9 BOUNDARY PROJECT MANAGER: C. SUTTELL Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra www.s nterracor .com NOTES: FIGURE 5-9 ALL BOUNDARIES ARE APPROXIMATE. CONTROL VOLUME USED TO CALCULATE THE WATER CONTOUR INTERVAL IS 5 FEET. HEADS ARE SHOWN PRIOR TO DECANTING FOR MODEL LAYER14. BALANCE UNDER PRE -DECANTED CONDITIONS AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON UPDATED GROUNDWATER FLOW AND TRANSPORT DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE MODELING REPORT PLANE COORDINATE SYSTEM FIPS 3200(NAD83 AND NAVD88). ALLEN TEAM STATION S BELMONT, NORTH CAROLINA , . #3 .' s. #2 �s { #3 MEN&NUU, I .41 #1 � - / #9#20 #2� O BORON SOURCE ZONES NOTES: ALL BOUNDARIES ARE APPROXIMATE. SOURCES ARE PRESENT IN ASH LAYERS 4 THROUGH 8. NUMBER LABELS CORRESPOND TO CONCENTRATION DATA IN TABLE 5-5. SOURCES IN THE RAB ARE ACTIVE FROM 1957 TO 2020. SOURCES IN THE AAB ARE ACTIVE FROM 1973 TO 2020. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). DUKE GRAPHIC SCALE 580 0 580 1,160 4ENERGY CAROLINAS IN FEET) ( DRAWN BY: J. EBENHACK DATE: REVISED BY: R. KIEKHAEFER DATE: 11/18/2019 12/26/2019 161, APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 synTerra PROJECT MANAGER: C. SUTTELL www.svnterracori).com FIGURE 5-10a BORON SOURCE ZONES FOR THE HISTORICAL TRANSPORT MODEL IN ASH LAYERS 4 TO 8 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA #4 #14 IR a I 1 r#' r_LI11 BORON SOURCE ZONE NOTES: ALL BOUNDARIES ARE APPROXIMATE. SOURCES ARE PRESENT IN ASH LAYER 9. NUMBER LABELS CORRESPOND TO CONCENTRATION DATA IN TABLE 5-5. SOURCES IN THE RAB ARE ACTIVE FROM 1957 TO 2020. SOURCES IN THE AAB ARE ACTIVE FROM 1973 TO 2020. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). m DUKE GRAPHIC SCALE 575 0 575 1,150 4ENERGY CAROLINAS N FEET, DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL www svnterracnrn cnm synTer FIGURE 5-10b BORON SOURCE ZONES FOR THE HISTORICAL TRANSPORT MODEL IN ASH LAYER 9 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA Z t a.V. #10 1#161 ..#7 #6 { #20 #22 #13 #14 #9 #3 #4 #9 ##3 #9 "?#14 #15 !F" lb #5 #21 #11 - a. #4 #9 #20 #14 #18 #22 _ #24 #17 - ALE ��DUKE 580 GORAPHICSC580 1,160 ENERGY LEGEND CAROLINAS N FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 Q BORON SOURCE ZONES 161, APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 synTerra PROJECT MANAGER: C. SUTTELL www.synterracori).com NOTES, FIGURE 5-10c ALL BOUNDARIES AREAPPROXIMATE. BORON SOURCE ZONES FOR THE HISTORICAL SOURCES ARE PRESENT IN ASH LAYERS 10 AND 11 AND ACOAL PILE SOURCE IS PRESENT IN TRANSPORT MODEL IN ASH LAYERS 10 AND 11 LAYER 12 (#16). NUMBER LABELS CORRESPOND TO CONCENTRATION DATA IN TABLE 5-5. SOURCES IN THE RAB AND COAL PILE ARE ACTIVE FROM 1957 TO 2020. SOURCES IN THE AAB AND THE COAL PILE SOURCE IN LAYER 12 ARE ACTIVE FROM 1973 TO 2020. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL U PDATED GROU N DWATER FLOW AN D WAS COLLECTED ON MARCH 30,2018. TRANSPORT MODELING REPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200(NAD63). ALLEN STEAM STATION BELMONT, NORTH CAROLINA f ft •�• ,i `i J #10 #26 #25 #1 yN , LEGEND SULFATE SOURCE ZONES sm DUKE ALE 580 GORAPHICSC580 1,160 4ENERGY CAROLINAS N FEET) DRAWN BY: J. EBENHACK DATE: REVISED BY: R. KIEKHAEFER DATE: 11/18/2019 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL www svnterracnrn cnm synTer 5-11a ALL BOUNDARIES ARE APPROXIMATE. SOURCE SULFATE ZONES FOR THE SOURCES ARE PRESENT IN ASH LAYERS 4 THROUGH 8. NUMBER LABELS CORRESPOND TO CONCENTRATION DATA IN TABLE 5-5. SOURCES IN THE RAB ARE ACTIVE FROM 1957 TO 2020. HISTORICAL TRANSPORT MODEL IN SOURCES IN THE AAB ARE ACTIVE FROM 1973 TO 2020. ASH LAYERS 4 THROUGH 8 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30,2018. UPDATED GROUNDWATER FLOW AND DRAWING 2WITH APROJECTION OFNORTH CAROLINASTATE PLANE COORDINATE SYSTEM 00(NAD83). TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LEGEND 3 SULFATE SOURCE ZONES r�L #11 #9 #15 w 7 n . #13 - #3 ... �• �} lk DUKE VENERGY CAROLINAS l0p synTerra sm GRAPHIC SCALE 580 0 580 1,160 (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL NOTES: FIGURE 5-11 b ALL BOUNDARIES ARE APPROXIMATE. SULFATE SOURCE ZONES FOR THE HISTORICAL SOURCES ARE PRESENT IN ASH LAYER 9. NUMBER LABELS CORRESPOND TO CONCENTRATION TRANSPORT MODEL IN ASH LAYER 9 DATA IN TABLE 5-5. SOURCES IN THE RAB ARE ACTIVE FROM 1957 TO 2020. SOURCES IN THE AAB ARE ACTIVE FROM 1973 TO 2020. UPDATED GROUNDWATER FLOW AND AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13,2018. AERIAL TRANSPORT MODELING REPORT WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE ALLEN STEAM STATION SYSTEM FIRS 3200 (NAD83). BELMONT, NORTH CAROLINA #26 #10 ' #25 5: #1 N 17 #12 - GRAPHIC SCALE 580 0 580 1,160 4DUKE ENERGY LEGEND (IN FEET) CAROLINAS SULFATE SOURCE ZONES DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY:. EKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 synTerrc- PROJECT MANAGER: C. SUTTELL www.synterracorr).com NOTES, FIGURE 5-11c ALL BOUNDARIES AREAPPROXIMATE. SULFATE SOURCE ZONES FOR THE HISTORICAL SOURCES ARE PRESENT IN ASH LAYERS 10 AND 11 AND A COAL PILE SOURCE IS PRESENT IN TRANSPORT MODEL IN ASH LAYERS 10 AND 11 LAYER 12. NUMBER LABELS CORRESPOND TO CONCENTRATION DATA IN TABLE 5-5. SOURCES IN THE RAB AND COAL PILE ARE ACTIVE FROM 1957 TO 2020. SOURCES IN THE AAB ARE ACTIVE AND THE COAL PILE SOURCE IN LAYER 12 FROM 1973 TO 2020. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL UPDATED GROUNDWATER FLOW AND WAS COLLECTED ON MARCH 30,2018. TRANSPORT MODELING REPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). ALLEN STEAM STATION BELMONT, NORTH CAROLINA LEGEND ` 3 TDS SOURCE • f ^� �y 1 �� 1 #24 #5 19 a GRAPHIC SCALE 4DUKE 580 0 580 1,160 ENERGY ( CAROLINAS IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 synTerra PROJECT MANAGER: C. SUTTELL www.svnterracori).com NOTES, FIGURE 5-12a ALL BOUNDARIES AREAPPROXIMATE. TDS SOURCE ZONES FOR THE SOURCES ARE PRESENT IN ASH LAYERS 4 THROUGH 8. NUMBER LABELS CORRESPOND TO HISTORICAL TRANSPORT MODEL IN CONCENTRATION DATA IN TABLE 5-5. SOURCES IN THE RAB ARE ACTIVE FROM 1957 TO 2020. SOURCES IN THE AAB ARE ACTIVE FROM 1973 TO 2020. ASH LAYERS 4 THROUGH 8 AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL U PDATED GROU N DWATER FLOW AN D WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE TRANSPORT MODELING REPORT SYSTEM RIPS 3200 (NAD83). ALLEN STEAM STATION BELMONT, NORTH CAROLINA '•_^ ' '� ♦' �y ✓fit Tea" i ��'."�`���J r '` ','�`•+y #10 #30 ' #26 17* #1; Q TDS SOURCE ZONES #15 #24 #19 _ #3 ,. _. lk DUKE ENERGY • CAROLINAS 161 synTerra GRAPHIC SCALE 580 0 580 1,160 (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL NOTES: FIGURE 5-12b ALL BOUNDARIES AREAPPROXIMATE. TDS SOURCE ZONES FOR THE HISTORICAL SOURCES ARE PRESENT IN ASH LAYERS 9 THROUGH 11 AND A COAL PILE SOURCE IS PRESENT TRANSPORT MODEL IN ASH LAYERS 9 THROUGH IN LAYER 12. NUMBER LABELS CORRESPOND TO CONCENTRATION DATA IN TABLE 5-5. SOURCES IN THE RAB AND COAL PILE ARE ACTIVE FROM 1957 TO 2020. SOURCES IN THE AAB 11 AND THE COAL PILE SOURCE IN LAYER 12 ARE ACTIVE FROM 1973 TO 2020. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL U PDATED GROU N DWATER FLOW AN D WAS COLLECTED ON MARCH 30,2018. TRANSPORT MODELING REPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200(NAD83). ALLEN STEAM STATION BELMONT, NORTH CAROLINA ' 1Wa!y 7 Zt tilt+>�� �1�'►Jr +�. ,.R _' r�.±\� 1•aDi-/ 5t. 40 # AK LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY . RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY . RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). w DUKE GRAPHIC SCALE 580 0 580 1,160 4ENERGY CAROLINAS IN FEET) ( DRAWN BY: J. EBENHACK DATE: REVISED BY: R. KIEKHAEFER DATE: 11/18/2019 12/26/2019 161, APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 synTerra PROJECT MANAGER: C. SUTTELL www.svnterracori).com FIGURE 5-13a SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS (MODEL YEAR 2019) UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LEGEND SULFATE > 500 ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - ASH BASIN COMPLIANCE BOUNDARY - RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). GRAPHIC SCALE 4DUKE 580 0 580 1,160 ENERGY N FEET) CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 10 REVISED BY: R. KIEKHAEFER DATE: 12/18/2019 APPROVED BY: L. DRAGO DATE: 12/18/2019 CHECKED BY: L. DRAGO DATE: 12/18/2019 synTerra PROJECT MANAGER: C. SUTTELL www.synterracorp.com FIGURE 5-13b SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS (MODEL YEAR 2019) UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA `--a--�- .. ♦ " - �^ .tit .Y 1 1• LEGEND TDS > 600 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY - RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). DUKE ENERGY CAROLINAS 161 synTerra GRAPHIC SCALE 580 0 580 1,160 (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 APPROVED BY: L. DRAGO DATE: 12/26/2019 CHECKED BY: L. DRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL FIGURE 5-13c SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS (MODEL YEAR 2020) UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 60p 570 570 0 595 OQ, ti� - o h 590-2,t . u u u, u ,c, 2 o J A � I tie' � � f . �- ♦ _ �4i 63p C �. CID o 635 LEGEND DUKE 580 GORAPHICSCALE 580 1,160 ENERGY (IN FEET) INTERIM DRAIN CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 HYDRAULIC HEAD (FEET) REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 ACTIVE ASH BASIN WASTE BOUNDARY APPROVED BY: L. DRAGO DATE: 12/26/2019 — - — RETIRED ASH BASIN WASTE BOUNDARY CHECKED BY: L. DRAGO DATE: 12/26/2019 ASH BASIN COMPLIANCE BOUNDARY synTerra PROJECT MANAGER: C. SUTTELL RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY WWW.S nterracor .com NOTES: FIGURE 6-1 ALL BOUNDARIES ARE APPROXIMATE. SIMULATED HYDRAULIC HEADS IN SAPROLITE CONTOUR INTERVAL IS5FEET AFTER DECANTING (MODEL LAYER 14) INTERIM DRAIN HEAD IS HELD AT 615 FEET. UPDATED GROUNDWATER FLOW AND AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13,2018. AERIAL TRANSPORT MODELING REPORT WAS COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200(NAD83 AND NAVD88). BELMONT, NORTH CAROLINA STA 57. 57?- -a i I 1 1 C 1 LEGEND —HYDRAULIC HEAD (FEET) _ RETIRED ASH BASIN WASTE } FLOW WITHIN LOCAL SYSTEM BOUNDARY } FLOW OUTSIDE LOCAL SYSTEM • ASH BASIN COMPLIANCE BOUNDAR NOTES: ALL BOUNDARIES ARE APPROXIMATE. ARROWS INDICATE INFERRED DIRECTION ONLY, NOT MAGNITUDE. CONTOUR INTERVAL IS 2 FEET. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83 AND NAVD88). I Y � n j�gg � .i,ti, • l DUKE 575 GRAPHIC SCALE 0 575 1,150 t ENERGY (IN FLLT) DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/17/2019 APPROVED BY: L. DRAGO DATE: 12/17/2019 CHECKED BY: L. DRAGO DATE: 12/17/2019 synTerra PROJECT MANAGER: C. SUTTELL www.s nterracor .corn FIGURE 6-2 SIMULATED GROUNDWATER FLOW SYSTEM IN SAPROLITE AFTER DECANTING (MODEL LAYER 14) UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA I I_.. .....r- Y: LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH COMPLIANCE BOUIN ASH NDARY�NDFILL (' DUKE 580 GRAPHIC SCALE 580 1,160 ENERGY N FEET) NOTES: CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 ALL BOUNDARIES AREAPPROXIMATE. REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerid DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200(NAD83). www.synterracorr).com FIGURE 6-3a SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 8.8 YEARS OF DECANTED CONDITIONS WHEN CLOSURE -IN -PLACE IS COMPLETED UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 77 _ r� • . J I' S fit' I i� 11 Y: LEGEND SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH COMPLIANCE B UINDARYN ASH LANDFILL (' DUKE 580 GORAPHICSCALE 580 1,160 4 ENERGY N FEET) NOTES: CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 ALL BOUNDARIES AREAPPROXIMATE. REVISED BY: R. KIEKHAEFER DATE: 12/19/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS 10 APPROVED BY: L. DRAGO DATE: 12/19/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/19/2019 synTerid PROJECT MANAGER: C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). www.S nterracor .COATI FIGURE 6-3b SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 8.8 YEARS OF DECANTED CONDITIONS WHEN CLOSURE -IN -PLACE IS COMPLETED UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA �I r S r _ i1 TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY } - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL GRAPHIC SCALE COMPLIANCE BOUNDARY V' N E DU580 0 580 1,160 NOTES: CAROLINAS (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 ALL BOUNDARIES ARE APPROXIMATE. REVISED BY: R. KIEKHAEFER DATE: 12/19/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/19/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/19/2019 synTerid DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200(NAD83). www.synterracorD.com FIGURE 6-3c SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 8.8 YEARS OF DECANTED CONDITIONS WHEN CLOSURE -IN -PLACE IS COMPLETED UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA I ,2µY� r r' ter,. LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY } RETIRED ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL GRAPHIC SCALE(' DUKE 580 0 580 1,160 COMPLIANCE BOUNDARY A ENERGY NOTES: CAROLINAS (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 ALL BOUNDARIES ARE APPROXIMATE. REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerid DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200(NAD83). www.synterracorD.com FIGURE 6-4a SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 22 YEARS OF DECANTED CONDITIONS WHEN CLOSURE -BY -EXCAVATION IS COMPLETED UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA ft LEGEND SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - ASH BASIN COMPLIANCE BOUNDARY Y JIN a RETIRED ASH BASIN ASH LANDFILL GRAPHIC SCALE COMPLIANCE BOUNDARY 4' N E DU580 0 580 1,160 NOTES: CAROLINAS (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 ALL BOUNDARIES ARE APPROXIMATE. REVISED BY: R. KIEKHAEFER DATE: 12/19/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/19/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/19/2019 synTerid PROJECT MANAGER C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200(NAD83). www.synterracorD.com FIGURE 6-4b SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 22 YEARS OF DECANTED CONDITIONS WHEN CLOSURE -BY -EXCAVATION IS COMPLETED UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LEGEND TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY - — - RETIRED ASH BASIN WASTE BOUNDARY - — - ASH BASIN COMPLIANCE BOUNDARY a RETIRED ASH BASIN ASH LANDFILL GRAPHIC SCALE COMPLIANCE BOUNDARY 4S N E DU580 0 580 1,160 NOTES: CAROLINAS (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 ALL BOUNDARIES ARE APPROXIMATE. REVISED BY: R. KIEKHAEFER DATE: 12/19/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/19/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/19/2019 synTerid PROJECT MANAGER C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200(NAD83). www.svnterracorr).com FIGURE 6-4c SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 22 YEARS OF DECANTED CONDITIONS WHEN CLOSURE -BY -EXCAVATION IS COMPLETED UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 1 �I f, 1 � wi a { 77 +R+ql 1 F i 4 � IrE 1 +` D PROPOSED MAJOR CONTOUR(25 FOOT) PROPOSED MINOR CONTOURS FOOT) NOTES L+ LIMITSOF EXISTING RAB LANDFILL LINER of EXISTING MAJOR CONTOUR(25 FOOT) 1. RAB LANDFILL INTENDED TO BE IN OPERATION, FINAL GRADES NOT SHOWN HERE. EXISTING MINOR CONTOUR IS FOOT) DUKE ENERGY PROPERTY BOUNDARY 2. TO IMPROVE CLARITY, ONLY 5-FOOT CONTOURS ARE SHOWN ON THIS SHEET +� ++ APPROXIMATE LIMITS OF IMPOUNDED ASH/UMITSOF CLOSURE CAP ASH STORAGE BOUNDARY 100YR FLOOD LINE 04WsEMOURE PROPOSED UNPAVED ROADS r* — +•-' T — CCR UNIT BOUNDARY DRAWN BY: J. EBENHACK DATE: 12/11/2019 FIGURE 6-5 %DUKE ENERGY REVISED BY: CLOSURE -BY -EXCAVATION DESIGN USED IN CAROtINAS CHECKED BY: K. Webb THE SIMULATIONS AECOM, 2019a UPDATED GROUNDWATER FLOW AND APPROVED BY: K. Webb TRANSPORT MODELING REPORT `10 �r PROJECT MANAGER: C. SUTTELL ALLEN STEAM STATION BELMONT, NORTH CAROLINA SYrlTerrd www.synterracorp.com .F LEGEND CLOSURE DRAINS � ACTIVE ASH BASIN WASTE BOUNDARY GRAPHIC SCALE f 0 580 1,160 DUKE 580 Q LANDFILL FOOTPRINT . RETIRED ASH BASIN WASTE BOUNDARY ENERGY RETENTION PONDS . . . ASH BASIN COMPLIANCE BOUNDARY CAROLINAS (IN FEET) HYDRAULIC HEAD (FEET) RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY DRAWN BY: J. EBENHACK DATE: 11/18/2019 _ � REGIONAL GROUNDWATER DIVIDE REVISED BY: R. KIEKHAEFER DATE: 12/12/2019 FLOW WITHIN LOCAL SYSTEM APPROVED BY: L. DRAGO DATE: 12/12/2019 FLOW OUTSIDE LOCAL SYSTEM CHECKED BY: L. DRAGO DATE: 12/12/2019 GROUNDWATER LEAVING LOCAL SYSTEM WnTerra I PROJECT MANAGER: C. SUTTELL www.svnterracorD.com FIGURE 6-6 NOTES: ALL BOUNDARIES ARE APPROXIMATE. ARROWS INDICATE INFERRED SIMULATED GROUNDWATER FLOW SYSTEM IN SAPROLITE DIRECTION ONLY, NOT MAGNITUDE. UNDER CLOSURE -BY -EXCAVATION (MODEL LAYER 14) CONTOUR INTERVAL IS 5 FEET. HEADS ARE SHOWN AFTER CLOSURE BY EXCAVATION. IN MODEL LAYER 14 UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON MODELING REPORT DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200(NAD83). BELMONT, NORTH CAROLINA � i�y k�Y ` e�• +. ale.: 4 w3a M { f a! i!• , �ii 5t�!!M17�r h'Ma��YY'R'd` yy__4.t�.'t• '.,.,' a' _ . - f .A .�, e•4in ,1 �.. i S' -" wi. LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY ) - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY ��p)y t_P ... DUKE 580 o �r 880 1,160 NOTES: *ENERGY. ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 10 CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Terra www.synterracorr).com FIGURE 6-7a SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2050 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA w tit+>G�� ,�,.JX �a ., t\ i�aDi./ •,R _. -55��'l147ts7`Ztr .a�,�a,Yror^ Wy��• ` y '`'" ' .40 a LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY - - RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY DUKE 580 o �r s`so 1,160 NOTES: *ENERGY. ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 10 CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Terra www.synterracorp.com FIGURE 6-7b SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2100 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA h LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY ) - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY DUKE 580 o �r 880 1,160 NOTES: *ENERGY. ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 10 CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Terra www.synterracorp.com FIGURE 6-7c SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2150 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA BORON > 700 Ng/L imb ACTIVE ASH BASIN WASTE BOUNDARY ; ,, - - RETIRED ASH BASIN WASTE BOUNDARY ; - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY (' DUKE 580 GRAPHIC SCALE 580 1,160 NOTES: 4 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-7d SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2200 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA ,hr { f V i" ��' ' '•T w�,.tiy��fG�� ,�,�JX ,yea ., i_,aDi•/ - — _ 40 _ f ialmAl O h LEGEND SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY - - RETIRED ASH BASIN WASTE BOUNDARY ) - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY -00 46, ('ALE DUKE 580 GORAPHICSC580 1,160 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-8a SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2050 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA m h LEGEND SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY - - RETIRED ASH BASIN WASTE BOUNDARY ) - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY (' ALE DUKE 580 GORAPHICSC580 1,160 4 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorr).com FIGURE 6-8b SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2100 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA _40"�' 46, h • LEGEND SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY - - RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY GRAPHIC SCALE NOTES: (' DUKE V 580 580 1,160 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS 1 APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Jy nTerra www.synterracorp.com FIGURE 6-8c SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2150 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA .' • f O Z - LEGEND SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY - - RETIRED ASH BASIN WASTE BOUNDARY ) - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY � ' 46, • '� (' ALE DUKE 580 GORAPHICSC580 1,160 4 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-8d SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2200 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA i4r-,?i`i}1 ' � • .._ ' may,•. ''ii��F� kk � /+ � x • w�,.tiy��fG�� ,�,�JX ,yea ., i_,aDi•/ - — _ 54. # a• .. f vY 40 LEGEND µ TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY GRAPHICSCALE ('DUKE 580 G580 1,160 NOTES: 4 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CARO LI NAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/111/21119 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-9a SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2050 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 4" Aga, I ".. F Am voll 40 a 1�• �'0"'?i>L. •', 'a, _i t+�w_^� - .may - P t a ,` NO _ _ ,� ..:. LEGEND µ TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY GRAPHICSCALE ('DUKE 580 G580 1,160 NOTES: 4 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CARO LI NAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBEN HACK DATE: 11/111/21119 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-9b SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2100 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 'AMEN" 1 AM � /-• a 1� ;� --- - ON �'0"'?i>`.•,, 'a, -i t+�w_�^� � - .may - Ali P t a LEGEND TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY -4104bol ' . p d4 o w ^0,� • ('DUKE 4 ENERGY CARO LI NAS GRAPHICSCALE 580 G580 1,160 (IN FEET) NOTES: ALL BOUNDARIES ARE APPROXIMATE. DRAWN BY: J. EBENHACK DATE: 11/111/21119 SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. 1 0 APPROVED BY: L. DRAGO DATE: 12/20/2019 CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Terra www.svnterracorD.com FIGURE 6-9c SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2150 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA Awl YA _j- '+ •` 40 �0'?►!• . c . -; tR'!C'.Yw� �. .. — ; � _ - GAF 7 P t a LEGEND TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY -410 ' 4bol . p w ,t.��,.rY .r.j1Y'1 • , GRAPHICSCALE ('DUKE 580 G580 1,160 NOTES: 4 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CARO LI NAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/111/21119 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-9d SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2200 FOR THE CLOSURE -BY -EXCAVATION SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA y` Point 3 2 ` r Point 2a LEGEND REFERENCE LOCATION r ACTIVE ASH BASIN WASTE BOUNDARY i ter,. - - RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY GORAPHICSC580 NOTES: 'ALE DUKE 580 1,160 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLI NAS (IN FEET) THE LOCATION LABELED "POINT 2A" FOR SULFATE AND TDS WAS CHOSEN TO CAPTURE THE MAXIMUM DRAWN BY: J. EBENHACK DATE: 11/18/2019 CONCENTRATIONS IN THAT REGION. REVISED BY: R. KIEKHAEFER DATE: 12/12/2019 �� APPROVED BY: L. DRAGO DATE: 12/12/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/12/2019 PROJECT MANAGER: C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE symerra SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-10 REFERENCE LOCATIONS USED FOR TIME SERIES DATASETS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA Closure -by -Excavation 2,000 1,SOD 1,6DO 1,4D0 v 1,200 r� 1,ODO 8o] 0 U I` 600 Q L Go n r� r_� r.0 H r.0 a un o un C) rn � � °° m m o o N N rl N N N nl N r q N N n! Year � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE 6-11 fENJERGY, REVISED BY: SUMMARY OF MAXIMUM BORON IN ALL NON -ASH LAYERS AS FUNCTIONS OF TIME AT CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB REFERENCE LOCATIONS 1, 2, 3, AND 4 FOR THE CLOSURE -BY -EXCAVATION SCENARIO PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA synTerra www.synterracorp.com J to E C 0 L c� 0 u ra 0.O 1,5DO 1,000 5OO O Cl osu re -by -Excavation 1� Ln r-I [A N ro O CD C) C) CD O r-I r- N N ro ro r-I r q N N N N N N N Year � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE 6-12 fENJERGY, REVISED BY: SUMMARY OF MAXIMUM SULFATE IN ALL NON -ASH LAYERS AS FUNCTIONS OF TIME AT CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR THE CLOSURE -BY -EXCAVATION SCENARIO PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA synTerra www.synterracorp.com fflo �—, 3,500 J h,D E 3,000 o z,500 1 L w 2,000 c� 0 1,500 CIS 1,000 500 Cl osu re -by -Excavation CD O N N N N Year Ln CD 1.11 ro coC) N N m m N N N N � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE 6-13 fENJERGY, REVISED BY: SUMMARY OF MAXIMUM TDS IN ALL NON -ASH LAYERS AS FUNCTIONS OF TIME AT CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR THE CLOSURE -BY -EXCAVATION SCENARIO PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT `� ALLEN STEAM STATION BELMONT, NORTH CAROLINA synTerra VAM synterracorp.com PIN to L . 'i. asp `+•Y' r '4 1 DSerrR f 1 ! AID ysa,mw- - _ '-- �• � troLtQresfv:r. i,IM' �==���ti}•�----yti: .-t L�r. .r .mow y I ++�� } L k � V �yi•.kY r • - � � I -� GBIAC*4 SIRT[ LLM 9Mi RV'S'+Yi III i �} L - f ik .i;; _ f'Eo>WLUY4Y Rr�ud.,tui[ku� ':' QilTLT L cwr4V Kwr Ai•T tom:. -: �.�'.. L4i wr�c✓'•�r:e LEGEND HATCH LEGEND PROPOSED MAJOR CONTOUR (25 FOOT) PROPOSED LIMITS OF STRUCTURAL FILL TO REPLACE REMOVED CCR MATERIAL PROPOSED MINOR CONTOUR (5 FOOT) LIMITS OF EXISTING RAB LANDFILL LINER WETLAND !` EXISTING DRAINAGE FLOW PATH —I PROPOSED DRAINAGE FLOW PATH •T — — EXISTING MAJOR CONTOUR(25 FOOT) EXISTING MINOR CONTOUR (5 FOOT) - DUKE ENERGY PROPERTY BOUNDARY r ^ APPROXIMATE LIMITS OF IMPOUNDED ASH (EXISTING) ir�rr ASH STORAGE BOUNDARY ihlF REVISED LIMITS OF CCR MATERIAL (PROPOSED) CCRUNITBOUNDARY DUKE DRAWN BY: REVISED gy, J. EBENHACK DATE: 12/11/2019 CLOSURE-IN-PLACEFIGURE ENERGY,DESIGN USED IN THE . SIMULATIONS (AECOM, 2019b) CHECKED BY: K. WEBB PROGRESS APPROVED BY: K. WEBB UPDATED GROUNDWATER FLOW AND PROJECT MANAGER: C. SUTTELL TRANSPORT MODELING REPORT ALLEN STEAM STATION synTerra www.synterracorp.com BELMONT, NORTH CAROLINA mm tallml-iol 1 vu LEGEND CLOSURE DRAINS � ACTIVE ASH BASIN WASTE BOUNDARY f DUKE GRAPHIC SCALE 580 0 580 1,160 Q CLOSURE CAP FOOTPRINT . RETIRED ASH BASIN WASTE BOUNDARY ENERGY HYDRAULIC HEAD (FEET) . . . ASH BASIN COMPLIANCE BOUNDARY CAROLINAS (IN FEET) REGIONAL GROUNDWATER DIVIDE RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY DRAWN BY: J. EBENHACK DATE: 11/18/2019 FLOW WITHIN LOCAL SYSTEM REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 FLOW OUTSIDE LOCAL SYSTEM APPROVED BY: L. O DATE: 12/26/2019 GROUNDWATER LEAVING LOCAL SYSTEM CHECKED BY: L. DRAGRAGO DATE: 12/26/2019 PROJECT MANAGER: C. SUTTELL synTerra www.svnterracorD.com FIGURE 6-15 NOTES: ALL BOUNDARIES ARE APPROXIMATE. ARROWS INDICATE INFERRED SIMULATED GROUNDWATER FLOW SYSTEM IN SAPROLITE DIRECTION ONLY, NOT MAGNITUDE. UNDER CLOSURE -IN -PLACE (MODEL LAYER 14) CONTOUR INTERVAL IS 5 FEET. HEADS ARE SHOWN IN MODEL LAYER 14 AFTER CLOSURE IN PLACE. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON MODELING REPORT DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200(NAD83). BELMONT, NORTH CAROLINA mi LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY i - - RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY DUKE 580 o �r 880 1,160 NOTES: V ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/26/2019 COLLECTED ON MARCH 30, 2018. 10 CHECKED BY: L. DRAGO DATE: 12/26/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Terra www.synterracorp.com FIGURE 6-16a SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2050 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA - - - RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY s RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY GRAPHIC SCALE NOTES: � DUKE 580 0 580 1,160 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/26/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/26/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-16b SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2100 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY i - - RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY DUKE 580 o �r 880 1,160 NOTES: V ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/26/2019 COLLECTED ON MARCH 30, 2018. 10 CHECKED BY: L. DRAGO DATE: 12/26/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Terra www.synterracorp.com FIGURE 6-16c SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2150 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LEGEND BORON > 700 Ng/L ACTIVE ASH BASIN WASTE BOUNDARY I - RETIRED ASH BASIN WASTE BOUNDARY - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY IF V DUKE 580 G0 RAPHICSC580 1,160 NOTES: *ENERGY. ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/26/2019 COLLECTED ON MARCH 30, 2018. 10 CHECKED BY: L. DRAGO DATE: 12/26/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). Terra www.synterracorp.com FIGURE 6-16d SIMULATED MAXIMUM BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2200 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 1 ' • .._ ' may,•. ,hr { f V i" ��' ' '•T w�,.tiy��fG�� ,�,�JX ,yea ., i_,aDi•/ - - _ 40 _ f ialmAl --- - r now M 1 -00 46, SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY .; ,, - - RETIRED ASH BASIN WASTE BOUNDARYlab i& - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY ('ALE DUKE 580 GORAPHICSC580 1,160 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-17a SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2050 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 46, SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - — - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY ra ;f}a � •q GRAPHICSCALE ('DUKE 580 G580 1,160 NOTES: 4 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CARO LI NAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/111/21119 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/26/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/26/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/26/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-17b SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2100 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA '��� fir• # Y rN j� 5• .40 _ f 2 1� -00 1 r/�r\111 46, Vie, - SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY .; ,, - - RETIRED ASH BASIN WASTE BOUNDARYlab imL - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY ('ALE DUKE 580 GORAPHICSC580 1,160 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-17c SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2150 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 'AMEN" � h J f v �`• ._, J t , i��x5a 40 - - , , .. - • f • � r 1� .-I C d H 1 r/�r\111 SULFATE > 250 mg/L ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY - — - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY GRAPHICSCALE ('DUKE 580 G580 1,160 NOTES: 4 ENERGY ALL BOUNDARIES ARE APPROXIMATE. CARO LI NAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/111/21119 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-17d SIMULATED MAXIMUM SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2200 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 7 _V..7J11_ TDS > 500 mglL Imb ACTIVE ASH BASIN WASTE BOUNDARY ; •( RETIRED ASH BASIN WASTE BOUNDARY ; ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY ('ALE DUKE 580 GORAPHICSC580 1,160 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-18a SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2050 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA .a a, 1 4, Q. c+ji 5t'1�67`�rr <Y:'�. as .`"la�Yror'•^ 1 rt� y ':;i" �..+ � � ' _ ram.;' �i•5', t ,i - _ . - . - a 40 .t ­WN .mot ,�•+, ,�.. . _v 46 h im _V..7J\I_ TDS > 500 mglL , lab i ACTIVE ASH BASIN WASTE BOUNDARY ; •( RETIRED ASH BASIN WASTE BOUNDARY ; - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY ('LE DUKE 580 0RAPHICSC580 1,160 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-18b SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2100 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 'AMEN" 4r-,?i`i}1 ' � • .._ ' may,•. 40 �y A ~ 4 1 ���•^ '. t _ ,ate' "' � i • '� TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY r - - RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL Sao COMPLIANCE BOUNDARY ��ALE DUKE 580 GORAPHICSC580 1,160 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-18c SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2150 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA llo� T-7 mt. 'Ona!�..•,, 'a, _i t+�w_^� - .may - -40IIIIIIIIII' 4hp, 1 CP�CAII'% TDS > 500 mg/L ACTIVE ASH BASIN WASTE BOUNDARY - - RETIRED ASH BASIN WASTE BOUNDARY ; - - ASH BASIN COMPLIANCE BOUNDARY RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY ('ALE DUKE 580 GORAPHICSC580 1,160 NOTES: ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) SIMULATION DOES NOT INCLUDE ACTIVE REMEDIATION. DRAWN BY: J. EBENHACK DATE: 11/18/2019 1 0 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83). www.synterracorp.com FIGURE 6-18d SIMULATED MAXIMUM TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN 2200 FOR THE CLOSURE -IN -PLACE SCENARIO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA o �� :044 1,600 1,400 0 1,200 +_j Co *j 1,000 c- c- 800 G U c- 600 G co r44 Closure -in -Place r- rH r-1 FD CD Ln a Ln C) Ln m 0O rN-1 r�-1 N NN M rn r-I N N N N N N N N Yea r � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE 6-19 fENJERGY, REVISED BY: SUMMARY OF MAXIMUM BORON IN ALL NON -ASH LAYERS AS FUNCTIONS OF TIME AT CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB REFERENCE LOCATIONS 1, 2, 3, AND 4 FOR THE CLOSURE -IN -PLACE SCENARIO PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA synTerra www.synterracorp.com Closure -in -Place — Point 1 2,000 — Paint 2a Point 3 _j Point 4 40 I E 1,500 — — — 02L Std = 250 µgf L Q � 1,000 N V V N 500 3 Cf} 0 r- r-1 LD 0O r_� LD a Ln a Ln m CD r N N �N-I ��-1 N N rrn M N rn! N N N r q N Yea � DUKE fENJERGY, DRAWN BY: J. EBENHACK DATE: 12/7/2019 REVISED BY: FIGURE 6-20 SUMMARY OF MAXIMUM SULFATE IN ALL NON -ASH LAYERS AS FUNCTIONS OF TIME AT CAROUNAs CHECKED BY: K. WEBB APPROVED BY: K. WEBB REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR THE CLOSURE -IN -PLACE SCENARIO PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION synTerra BELMONT, NORTH CAROLINA www.synterracorp.com Closure -in -Place 4,000 .--w 3,500 J E 3,000 Q 2,500 c 2,000 w U U 1,500 1,000 500 0 r- r_q F.0 r_� La a Ln a Ln a) m CD 0NO r-I r_- N N rrn M rl N N N N r'J N N r q N Yea � DUKE DRAWN BY: J. EBENHACK DATE: 12/7/2019 FIGURE 6-21 fENJERGY, REVISED BY: SUMMARY OF MAXIMUM TDS IN ALL NON -ASH LAYERS AS FUNCTIONS OF TIME AT CHECKED BY: K. WEBB CAROUNAs APPROVED BY: K. WEBB REFERENCE LOCATIONS 1, 2a, 3, AND 4 FOR THE CLOSURE -IN -PLACE SCENARIO PROJECT MANAGER: C. SUTTELL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT `� ALLEN STEAM STATION BELMONT, NORTH CAROLINA synTerra VAM synterracorp.com LOSURE BY XCAVATION, YEARS AFTER CLOSURE ` CLOSURE BY EXCAVATION, 108 YEARS AFTER CLOSURE I`'- - LEGEND ASH BASIN COMPLIANCE BOUNDARY BORON 700 - 4000 Ug/L ACTIVE ASH BASIN WASTE - RETIRED ASH N ASH •LANDFILL COMPLIANCE BOUNDARY BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). LOSURE BY XCAVATION, I YEARS AFTER CLOSU r CLOSURE BY EXCAVATION, 121 YEARS AFTER CLOSURE i (ALE DUKE 1,300 GORAPHICSC1,300 2,600 ENERGY. (IN FEET, >uIVAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/12/2019 APPROVED BY: L. DRAGO DATE: 12/12/2019 CHECKED BY: L. DRAGO DATE: 12/12/2019 synTerid PROJECT MANAGER: C. SUTTELL www.s nterracor .com FIGURE 6-22 COMPARISON OF SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA LOSURE BY XCAVATION, YEARS AFTER CLOSURE ` r 21 YEARS AFTER CLOSUREjj CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE GRAPHIC SCALE ( DUKE 1,300 0 1,300 2,600 ENERGY (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 LEGEND ASH BASIN COMPLIANCE BOUNDARY REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 SULFATE > 250 mg/L ' APPROVED BY: L. DRAGO DATE: 12/20/2019 RETIRED ASH BASIN ASH CHECKED BY.'L.DRAGO DATE: 12/20/2019 ACTIVE ASH BASIN WASTE LANDFILL COMPLIANCE PROJECT MANAGER:C.SUTTELL BOUNDARY BOUNDARY Terra WWW.S nterracor .com RETIRED ASH BASIN WASTE FIGURE 6-23 COMPARISON OF SIMULATED SULFATE BOUNDARY NOTES: CONCENTRATIONS IN ALL NON -ASH LAYERS ALL BOUNDARIES ARE APPROXIMATE. UPDATED GROUNDWATER FLOW AND TRANSPORT SIMULATIONS DO NOT INCLUDEACTIVE REMEDIATION. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION DRAWING WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE BELMONT, NORTH CAROLINA SYSTEM LOSURE BY XCAVATION, YEARS AFTER CLOSU VW' 1 YEARS AFTER CLOSURE CLOSURE IN PLACE, h 121 YEARS AFTER CLOSURE 13 GORAPHIC SCALE ( DUKE 1,300 1,300 2,600 ENERGY. (IN FEET) >L1iVA5 LEGEND RETIRED ASH BASIN WASTE DRAWN BY: J. EBENHACK DATE: 11/18/2019 BOUNDARY REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 APPROVED BY: L. DRAGO DATE: 12/20/2019 116rip TDS > 500 D19/L ASH BASIN COMPLIANCE CHECKED BY: L. DRAGO DATE: 12/20/2019 BOUNDARY PROJECT MANAGER: C. SUTTELL I ACTIVE ASH BASIN WASTE RETIRED ASH BASIN ASH synTerra WWW.s nterracor .com BOUNDARY - LANDFILL COMPLIANCE FIGURE 6-24 COMPARISON OF SIMULATED TDS CONCENTRATIONS BOUNDARY NOTES: IN ALL NON -ASH LAYERS ALL BOUNDARIES AREAPPROXIMATE. UPDATED GROUNDWATER FLOW AND TRANSPORT SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS COLLECTED ON MARCH 30, 2018. ALLEN STEAM STATION SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE BELMONT, NORTH CAROLINA SYSTEMIFIPS320BEEN 0(NAD83) _ i1 ♦ �♦ r1i N 'y 1 _S ul Go ul O .. ccn O LO 0 ] M - S 1 i%''�`L. '♦ -cr LEGEND HYDRAULIC HEAD (FEET)' VERTICAL EXTRACTION WELLS ♦ VERTICAL CLEAN WATER INFILTRATION WELLS ACTIVE ASH BASIN WASTE RETIRED ASH BASIN WASTE BOUNDARY - - ASH BASIN COMPLIANCE RETIRED ASH BASIN ASH LANDFILL COMPLIANCE BOUNDARY �� DUKE a80 0RaP"Ic scALF 580 1,160 NOTES: �. ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) CONTOUR INTERVAL IS 5FEET. DRAWN BY:J. EBENHACK DATE: 1111S/2019 REVISED BY: R. KIEKHAEFER DATE: 12/29/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/29/2019 COLLECTED ON MARCH 30,2018. CHECKED BY: L. DRAGO DATE: 12/29/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL RIPS PS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-25 SIMULATED HYDRAULIC HEAD IN SAPROLITE (MODEL LAYER 14) WITH THE ALTERNATIVE 3A REMEDIATION SYSTEM OPERATING UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA - . ✓w.,ay t - �y �a.� .,�1 - 555' , • ' � to Go 1 s o I1\ 771- - l LEGEND HYDRAULIC HEAD (FEET) VERTICAL EXTRACTION WELLS* ` A VERTICAL CLEAN WATER INFILTRATION WELLS i { HORIZONTAL CLEAN WATER INFILTRATION WELLS ACTIVE ASH BASIN WASTE �.I� '0 RETIRED ASH BASIN WASTE ^ o BOUNDARY - — - ASH BASIN COMPLIANCE RETIRED ASH BASIN ASH LANDFILL w + f COMPLIANCE BOUNDARY �� DUKE 580 0RaP"Ic scALF 580 1,160 NOTES: �. ENERGY ALL BOUNDARIES ARE APPROXIMATE. CAROLINAS (IN FEET) CONTOUR INTERVAL IS 5 FEET. DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/29/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/29/2019 COLLECTED ON MARCH 30,2018. CHECKED BY: L. DRAGO DATE: 12/29/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL RIPS PS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-26 SIMULATED HYDRAULIC HEAD IN SAPROLITE (MODEL LAYER 14) WITH THE ALTERNATIVE 3B REMEDIATION SYSTEM OPERATING UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA �� � k� �- •� ` � « gip,;.. •`±!{ � f a ~�{ ; Iy: - AA ♦ u y 555 J i+ • lI s �r 0 545 5 _ 6&eo Ln o •• O * r . Lo • G20 �• ,xr I - - . � ' —4 :,; - r� -fir ■ LEGEND RETIRED ASH BASIN WASTE BOUNDARY BORON > 700 Ng/L — HYDRAULIC HEAD (FEET) — . — - ASH BASIN COMPLIANCE - t BOUNDARY +` VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH VERTICAL CLEAN WATER — - — - LANDFILL COMPLIANCE ` ♦ INFILTRATION WELLS BOUNDARY } ACTIVE ASH BASIN 1 - WASTE BOUNDARY NOTES: ( DUKE 580 GRAPHIC SCALE 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. . ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 FIGURE SHOWS INITIAL ALTERNATIVE 3A REMEDIATION SYSTEM REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerid DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-27a SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 4 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA �570—� :.... 60S ., Cam'.« 1er:,•`•.1!{ � \ O' 595 �� 5j5 ♦A ♦ cn 590 _ ♦ o ♦ r S8S 4 ��. 550 S60 few.., � 1 1 \1 OD Lrl ■ \\ w 6i jj CD Ul R h\ LEGEND RETIRED ASH BASIN WASTE BOUNDARY BORON > 700 Ng/L — HYDRAULIC HEAD (FEET) - . - - ASH BASIN COMPLIANCE t BOUNDARY VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH A VERTICAL CLEAN WATER - - - - LANDFILL COMPLIANCE ♦ INFILTRATION WELLS BOUNDARY } ACTIVE ASH BASIN 1 WASTE BOUNDARY �• k NOTES: ( DUKE 575 GRAPHIC SCALE 0 575 1,150 ALL BOUNDARIES ARE APPROXIMATE. . ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 FIGURE SHOWS FINAL ALTERNATIVE 3AREMEDIATION SYSTEM REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerid PROJECT MANAGER: C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-27b SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 7 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA -570—� :.... 595 �� 5j5 ♦� ' ♦ cn 590 _ ♦ � 00 o 585.v ♦cn 550 S60 few., \ ■ w w o �v No rno°��'v,cn x, a.I !r OD en o co3 q cD.,, /f LEGEND RETIRED ASH BASIN WASTE BOUNDARY BORON > 700 Ng/L — HYDRAULIC HEAD (FEET) ASH BASIN COMPLIANCE BOUNDARY t +` VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH VERTICAL CLEAN WATER — - — - LANDFILL COMPLIANCE ♦ INFILTRATION WELLS BOUNDARY } ACTIVE ASH BASIN 1 - WASTE BOUNDARY NOTES: ( DUKE GRAPHIC SCALE 580 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. . ENERGY CONTOUR INTERVAL IS 5 FEET. CAROLINAS (IN FEET) DRAWN BY: J. EBENHACK DATE: 11/18/2019 FIGURE SHOWS FINAL ALTERNATIVE 3A REMEDIATION SYSTEM REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 PROJECT MANAGER: C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE synTerid SYSTEM RIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-27c SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA .a �570 570 � 5g5 c U' ��. C57Lo AA Ott F `u O (' o o cfl,�p � cn o ih _ _ ,. • _ V �s, .:�-' :..e-tom-,? LEGEND SULFATE > 250 mg/L ASH BASIN COMPLIANCE HYDRAULIC HEAD (FEET) BOUNDARY _ VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH t ' - LANDFILL COMPLIANCE - VERTICAL CLEAN WATER ♦ BOUNDARY INFILTRATION WELLS a ACTIVE ASH BASIN ^' o WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY NOTES: 580 DUKE GRAPHIC SCALE 0 51,160 ALL BOUNDARIES ARE APPROXIMATE. EAICDGV® CONTOUR INTERVAL IS 5 FEET. (IN FEET) CAROLINAS FIGURE SHOWS INITIAL ALTERNATIVE 3A REMEDIATION SYSTEM DRAWN BY: J. EBENHACK REVISED BY: R. KIEKHAEFER DATE: 11/111/21119 DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL RIPS PS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-28a SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 4 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA y A AA t• 550 few.^ r - O cn . cn �. cn CT, co� 7� 6) S - O S LEGEND SULFATE > 250 mg/L ASH BASIN COMPLIANCE HYDRAULIC HEAD (FEET) BOUNDARY _ VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH t ' ♦ - LANDFILL COMPLIANCE - VERTICAL CLEAN WATER BOUNDARY INFILTRATION WELLS a ACTIVE ASH BASIN ^' o WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY NOTES: 580 DUKE GRAPHIC SCALE 0 51,160 ALL BOUNDARIES ARE APPROXIMATE. EAICDGV® (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3A REMEDIATION SYSTEM DRAWN BY: J. EBENHACK REVISED BY: R. KIEKHAEFER DATE: 11/111/21119 DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE synTerra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-28b SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 7 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 56 A� a&"�* Z w few.- cy, o J, OD ol 0 CD IX) A -IT � mma_ LEGEND SULFATE > 250 mg/L ASH BASIN COMPLIANCE HYDRAULIC HEAD (FEET) BOUNDARY VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH A VERTICAL CLEAN WATER LANDFILL COMPLIANCE BOUNDARY INFILTRATION WELLS ACTIVE ASH BASIN WASTE BOUNDARY RETIRED ASH BASIN WASTE BOUNDARY NOTES: GRAPHIC SCALE DUKE 580 0 580 1,160 ALL BOUNDARIES ARE APPROXIMATE. EAICDGV® CONTOUR INTERVAL IS 5 FEET. (IN FEET) CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3AREMEDIATION SYSTEM DRAWN BY: J. EBENHACK BY: R. KIEKHAEFER DATE: 11/111/21119REVISED DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY. L. DRAGO DATE: 12/20/20191, COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA SYSTEM RIPS 3200 (NAD83 AND NAVD88). STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL synTerra www.synterracorp.com FIGURE 6-28c SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA Ll Li ' cam• ay ts•t ``'11 �� � � •�.as'.cei.Y.:,r. it t�'t� j 1 L\\ h AA A n yw few _ r, . � «cam•_ _, •- -, (( V ul - \ 0 �., '..x. � cn o ih LEGEND RETIRED ASH BASIN /f ;. WASTE BOUNDARY =` TDS > 500 mg/L _ ASH BASIN COMPLIANCE HYDRAULIC HEAD (FEET) BOUNDARY VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH VERTICAL CLEAN WATER - - LANDFILL COMPLIANCE - INFILTRATION WELLS BOUNDARY ACTIVE ASH BASIN i' 4 WASTE BOUNDARY GRAPHIC SCALE E NOTES: DUKE 580 0 5 1,160 ALL BOUNDARIES ARE APPROXIMATE. �. EAICDGV® CONTOUR INTERVAL IS 5 FEET. (IN FEET) CAROLINAS FIGURE SHOWS INITIAL ALTERNATIVE 3A REMEDIATION SYSTEM DRAWN BY: J. EBEN HACK DATE: 11/111/21119 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83 AND NAVD88). synTerra www.synterracorp.com FIGURE 6-29a SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 4 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 14 wi a' 570-91 -- i. rn0) . cn cn c, ♦. w _ r , -♦ .«cc°" =, '- .• s gyp'— Al 7� 6) - O S A � LEGEND RETIRED ASH BASIN /f ;. =` WASTE BOUNDARY TDS > 500 mg/L _ ASH BASIN COMPLIANCE HYDRAULIC HEAD (FEET) BOUNDARY ` VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH VERTICAL CLEAN WATER - - LANDFILL COMPLIANCE - INFILTRATION WELLS BOUNDARY ACTIVE ASH BASIN i' 4 WASTE BOUNDARY E DUKE GRAPHIC SCALE580 0 51,160 NOTES: ALL BOUNDARIES ARE APPROXIMATE. �. EAICDGV® CONTOUR INTERVAL IS 5 FEET. (IN FEET) CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3A REMEDIATION SYSTEM DRAWN BY: J. EBENHACK REVISED BY: R. KIEKHAEFER DATE: 11/111/21119 DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL RIPS PS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-29b SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 7 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA y +,-♦♦ _t ♦_ w -01 j 554 — cn 6 cn w _ r , -� .«cc°" =, '- .• s gyp'— , 7� 6) S - O S A � LEGEND RETIRED ASH BASIN /f WASTE BOUNDARY TDS > 500 mg/L _ ASH BASIN COMPLIANCE HYDRAULIC HEAD (FEET) BOUNDARY i VERTICAL EXTRACTION WELLS RETIRED ASH BASIN ASH ♦ VERTICAL CLEAN WATER - - LANDFILL COMPLIANCE INFILTRATION WELLS BOUNDARY ACTIVE ASH BASIN i, 4 WASTE BOUNDARY ,r s ' GRAPHIC SCALE NOTES: ` DUKE 580 0 580 1,160 ALL BOUNDARIES ARE APPROXIMATE. �. EAICDGV® (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3A REMEDIATION SYSTEM DRAWN BY: J. EBEN HACK DATE: 11/111/21119 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE synTerra PROJECT MANAGER: C. SUTTELL SYSTEM RIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-29c SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3A REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA �. �57_0i a `., , .. • • Wit: � � w'.� Y + � `' �; SAS ♦ = ♦ u � Y - .. ®♦ ` 7 Fr' `SJ^S I 1 a. . 6cn I LEGEND ACTIVE ASH BASIN• BORON > 700 Ng/L WASTE BOUNDARY — HYDRAULIC HEAD (FEET) RETIRED ASH BASIN ; WASTE BOUNDARY rD VERTICAL EXTRACTION WELLS ASH BASIN COMPLIANCE VERTICAL CLEAN WATER BOUNDARY ♦ INFILTRATION WELLS RETIRED ASH BASIN ASH i HORIZONTAL CLEAN WATER - - LANDFILL COMPLIANCE 3 " INFILTRATION WELLS BOUNDARY r;> ( DUKE GRAPHIC SCALE NOTES: 580 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. . ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS DRAWN BY: J. EBENHACK DATE: 11/18/2019 FIGURE SHOWS INITIAL ALTERNATIVE 3B REMEDIATION SYSTEM REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 synTerid PROJECT MANAGER: C. SUTTELL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-30a SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 4 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA C a 570 o i , • A AN r .? - A AA �� � � a �• � � _y:•-♦ A 550 cn C."o 0 . s 'o of x P I �.ell : I_. LEGEND ACTIVE ASH BASIN %• BORON > 700 Ng/L WASTE BOUNDARY - - HYDRAULIC HEAD (FEET) RETIRED ASH BASIN ; WASTE BOUNDARY rD VERTICAL EXTRACTION WELLS ASH BASIN COMPLIANCE VERTICAL CLEAN WATER BOUNDARY A INFILTRATION WELLS RETIRED ASH BASIN ASH i HORIZONTAL CLEAN WATER - - LANDFILL COMPLIANCE 3 " INFILTRATION WELLS BOUNDARY r;> NOTES: DUKE 580 GRAPHIC SCALE 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM FIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-30b SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 7 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 575 Sip 1 •' � "� 'M�ir'� �'0 `. �57_0 570, 595 J S ' p Fr' 555 LO J L ` 00 Do C51Lo 6'� O 2 O m CD • 6� - � r �n a LEGEND - /f • ` ACTIVE ASH BASIN % BORON > 700 Ng/L WASTE BOUNDARY - - HYDRAULIC HEAD (FEET) RETIRED ASH BASIN ; WASTE BOUNDARY rD VERTICAL EXTRACTION WELLS ASH BASIN COMPLIANCE VERTICAL CLEAN WATER BOUNDARY A INFILTRATION WELLS RETIRED ASH BASIN ASH i HORIZONTAL CLEAN WATER - - LANDFILL COMPLIANCE 3 " INFILTRATION WELLS BOUNDARY r;> NOTES: DUKE 580 GRAPHIC SCALE 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 10, CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM FIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-30c SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 510� 5g5 _ 1 ' R \ 0 L O a - LEGEND SULFATE > 250 mg/L RETIRED ASH BASIN WASTE BOUNDARY HYDRAULIC HEAD (FEET) ASH BASIN COMPLIANCE VERTICAL EXTRACTION WELLS BOUNDARY VERTICAL CLEAN WATER RETIRED ASH BASIN ASH ♦ INFILTRATION WELLS - - LANDFILL COMPLIANCE HORIZONTAL CLEAN WATER BOUNDARY INFILTRATION WELLS ACTIVE ASH BASIN WASTE BOUNDARY NOTES: DUKE 580 GRAPHIC SCALE 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS INITIAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 10, CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE synTerra PROJECT MANAGER: C. SUTTELL SYSTEM FIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-31a SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 4 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA 2 a 57A AA 550'� 0) cn J O O O O OS O - _ O LEGEND RETIRED ASH BASIN SULFATE > 250 mg/L - - WASTE BOUNDARY HYDRAULIC HEAD (FEET) ASH BASIN COMPLIANCE VERTICAL EXTRACTION WELLS BOUNDARY VERTICAL CLEAN WATER RETIRED ASH BASIN ASH INFILTRATION WELLS - - LANDFILL COMPLIANCE ` HORIZONTAL CLEAN WATER BOUNDARY INFILTRATION WELLS ACTIVE ASH BASIN WASTE BOUNDARY NOTES: DUKE GRAPHIC SCALE 580 0 580 1,160 ALL BOUNDARIES ARE APPROXIMATE. ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 10, CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE synTerra PROJECT MANAGER: C. SUTTELL SYSTEM FIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-31 b SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 7 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA C�5�7O ♦ A AA A, COD c.n o", cn cn c, cn CD CO Cn O O p Nil& --7. LEGEND RETIRED ASH BASIN SULFATE > 250 mg/L WASTE BOUNDARY HYDRAULIC HEAD (FEET) ASH BASIN COMPLIANCE VERTICAL EXTRACTION WELLS BOUNDARY VERTICAL CLEAN WATER RETIRED ASH BASIN ASH ♦ INFILTRATION WELLS LANDFILL COMPLIANCE HORIZONTAL CLEAN WATER BOUNDARY INFILTRATION WELLS ACTIVE ASH BASIN WASTE BOUNDARY NOTES: GRAPHIC SCALE DUKE 580 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. ENERGY. (IN FEET) CONTOUR INTERVAL IS 5 FEET CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY. J. EBENHACK DATE: 11/18/2019REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY. L. DRAGO DATE: 12/20/20191, COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE I SYSTEM FIPS 3200 (NAD83 AND NAVD88). Terra PROJECT MANAGER: C. SUTTELL I www.synterracorp.com FIGURE 6-31c SIMULATED SULFATE CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA .tom :ti� •�" ,O' �� �� Q . �►°\\ 56 ' �O _ l� \ \ \ T a O al LEGEND RETIRED ASH BASIN TDS > 500 mg/L WASTE BOUNDARY % f — HYDRAULIC HEAD (FEET) _ _ _ _ ASH BASIN COMPLIANCE VERTICAL EXTRACTION WELLS BOUNDARY - r S ' VERTICAL CLEAN WATER RETIRED ASH BASIN ASH A INFILTRATION WELLS LANDFILL COMPLIANCE HORIZONTAL CLEAN WATER BOUNDARY F{° INFILTRATION WELLS ACTIVE ASH BASIN WASTE BOUNDARYIL +r f GRAPHIC SCALE NOTES: ` DUKE 580 0 580 1,160 ALL BOUNDARIES ARE APPROXIMATE. �. EAICDGV® (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS INITIAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY: J. EBENHACK DATE: 11/111/21119 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL RIPS PS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-32a SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 4 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA C a 570 �:b'�. �., ,...• - _•'fir_ � '� . I •: - ♦ AA 550'C � rn • cn cn o �: w cp cn o �t ���• ,.+4+:Co e '� ■ \ 6 `9t5� I I I I I O k SO �� j �S O G - _ O p _ V LEGEND RETIRED ASH BASIN TDS > 500 mg/L WASTE BOUNDARY f HYDRAULIC HEAD (FEET) _ _ _ _ ASH BASIN COMPLIANCE VERTICAL EXTRACTION WELLS BOUNDARY - VERTICAL CLEAN WATER RETIRED ASH BASIN ASH _ INFILTRATION WELLS — - — - LANDFILL COMPLIANCE ;a HORIZONTAL CLEAN WATER BOUNDARY , INFILTRATION WELLS ' ACTIVE ASH BASIN WASTE BOUNDARY - NOTES: DUKE 580 GRAPHIC SCALE 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. ENERGY (IN FEET) CONTOUR INTERVAL IS 5 FEET. CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY: J. EBENHACK DATE: 11/18/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY: L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 101 CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE Terra PROJECT MANAGER: C. SUTTELL SYSTEM FIPS 3200 (NAD83 AND NAVD88). www.synterracorp.com FIGURE 6-32b SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 7 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA C�5�7O ♦ A A A A, __550-c c.n Jo rn cn Co - Cn 01 O O A7!0 r LEGEND RETIRED ASH BASIN TDS > 500 mg/L WASTE BOUNDARY HYDRAULIC HEAD (FEET) ASH BASIN COMPLIANCE VERTICAL EXTRACTION WELLS BOUNDARY VERTICAL CLEAN WATER RETIRED ASH BASIN ASH A INFILTRATION WELLS LANDFILL COMPLIANCE HORIZONTAL WATER LEAN BOUNDARY c WNW; INFILTRATION WELLS ACTIVE ASH BASIN WASTE BOUNDARY NOTES: GRAPHIC SCALE DUKE 580 0 580 1,160 ALL BOUNDARIES AREAPPROXIMATE. ENERGY. (IN FEET) CONTOUR INTERVAL IS 5 FEET CAROLINAS FIGURE SHOWS FINAL ALTERNATIVE 3B REMEDIATION SYSTEM DRAWN BY.J. EBENHACK DATE: 11/18/2019REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON DECEMBER 13, 2018. AERIAL WAS APPROVED BY. L. DRAGO DATE: 12/20/2019 COLLECTED ON MARCH 30, 2018. 10, CHECKED BY: L. DRAGO DATE: 12/20/2019 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE PROJECT MANAGER: C. SUTTELL SYSTEM FIPS 3200 (NAD83 AND NAVD88). Terra www.synterracorp.com FIGURE 6-32c SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS AFTER 10 YEARS OF OPERATING THE ALTERNATIVE 3B REMEDIATION SYSTEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ALLEN STEAM STATION BELMONT, NORTH CAROLINA Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLES DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-1 OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE CALIBRATED FLOW MODEL Well Observed Head Computed Head Residual Head AB-01 R 621.5 621.88 -0.38 AB-02 623.68 624.90 -1.22 AB-04BR 639.68 639.16 0.52 AB-04D 638.64 639.32 -0.68 AB-04S 638.83 639.36 -0.53 AB-05 637.13 637.27 -0.14 AB-06A 571.43 573.95 -2.52 AB-06R 571.97 573.37 -1.40 AB-09D 568.44 568.63 -0.19 AB-09S 570.42 568.14 2.28 AB-10BR 569.56 573.31 -3.75 AB-10BRL 570.61 573.17 -2.56 AB-10D 566.19 570.01 -3.82 AB-10S 566.27 569.21 -2.94 AB-11D 610.42 609.19 1.23 AB-12D 638.98 638.27 0.71 AB-12S 637.8 638.34 -0.54 AB-13D 638.46 637.00 1.46 AB-13S 638.58 637.01 1.57 AB-14BR 626.8 625.54 1.26 AB-14D 626.27 625.67 0.60 AB-20D 637.02 637.37 -0.35 AB-20S 637.72 637.30 0.42 AB-21BR 636.58 636.24 0.34 AB-21BRL 636.61 636.04 0.57 AB-21D 636.61 636.26 0.35 AB-21S 636.38 636.30 0.08 AB-21SL 636.6 636.28 0.32 AB-22BR 599.9 600.19 -0.29 AB-22BRL 604.76 602.62 2.14 AB-22D 599.51 600.07 -0.56 AB-22S 594.6 593.06 1.54 AB-23S 637.68 637.50 0.18 AB-24BR 636.25 637.20 -0.95 Page 1 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-1 OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE CALIBRATED FLOW MODEL Well Observed Head Computed Head Residual Head AB-24D 635.98 637.26 -1.28 AB-24S 637.79 637.24 0.55 AB-24SL 637.65 637.32 0.33 AB-25BR 636.84 637.22 -0.38 AB-25BRU 636.97 637.86 -0.89 AB-25S 639.81 638.22 1.59 AB-25SL 637.52 638.05 -0.53 AB-26D 583.82 580.82 3.00 AB-26S 582.16 580.50 1.66 AB-27BR 620.33 618.98 1.35 AB-27D 618.32 619.71 -1.39 AB-27S 639.44 632.96 6.48 AB-28D 629.93 629.16 0.77 AB-28S 640.92 637.71 3.21 AB-29D 613.63 609.68 3.95 AB-29S 612.33 610.56 1.77 AB-29SL 612.39 609.40 2.99 AB-2D 622.75 624.88 -2.13 AB-30D 620.05 619.74 0.31 AB-30S 617.28 617.86 -0.58 AB-31D 579.05 578.87 0.18 AB-31S 578.08 579.36 -1.28 AB-32D 576.05 578.59 -2.54 AB-32S 581.55 578.95 2.60 AB-33D 594.33 595.42 -1.09 AB-33S 600.19 598.44 1.75 AB-34D 611.74 615.12 -3.38 AB-34S 612.18 615.14 -2.96 AB-35BR 621.07 621.06 0.01 AB-35D 620.9 621.12 -0.22 AB-35S 620.43 621.25 -0.82 AB-36D 621.89 624.19 -2.30 AB-36S 621.64 624.20 -2.56 AB-37D 623.63 624.50 -0.87 Page 2 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-1 OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE CALIBRATED FLOW MODEL Well Observed Head Computed Head Residual Head AB-37S 622.4 624.51 -2.11 AB-38BR 624.5 626.13 -1.63 AB-38D 624.27 626.22 -1.95 AB-38S 624.6 626.23 -1.63 AB-39D 618.86 619.08 -0.22 AB-39S 618.12 619.21 -1.09 BG-01D 635.41 633.14 2.27 BG-01DA 636.63 633.16 3.47 BG-01S 635.16 633.76 1.40 BG-02BR 586.44 587.53 -1.09 BG-02BRA-2 587.22 588.05 -0.83 BG-02D 587.85 587.40 0.45 BG-02S 589.92 587.29 2.63 BG-03D 606.9 608.06 -1.16 BG-03S 607 608.46 -1.46 BG-04BR 573.59 576.15 -2.56 BG-04D 574.04 575.73 -1.69 BG-04S 576.57 575.70 0.87 CCR-02D 617.32 617.67 -0.35 CCR-03D 594.68 593.40 1.28 CCR-03DA 592.65 594.39 -1.74 CCR-03S 611.87 602.47 9.40 CCR-04D 592.83 591.65 1.18 CCR-04DA 593.07 591.73 1.34 CCR-04SA 600.85 599.46 1.39 CCR-05D 597.43 595.20 2.23 CCR-05S 598.51 601.16 -2.65 CCR-06D 588.84 591.63 -2.79 CCR-06S 595.28 593.92 1.36 CCR-07D 588.07 586.61 1.46 CCR-07S 587.3 586.45 0.85 CCR-08D 582.24 581.05 1.19 CCR-08S 583.52 581.00 2.52 CCR-09D 578.5 575.24 3.26 Page 3 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-1 OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE CALIBRATED FLOW MODEL Well Observed Head Computed Head Residual Head CCR-09S 576.82 575.64 1.18 CCR-11 D 569.72 570.58 -0.86 CCR-11 DA 571.51 570.87 0.64 CCR-11S 571.15 569.93 1.22 CCR-14D 571.65 572.82 -1.17 CCR-14S 576.48 572.69 3.79 CCR-16D 571.91 572.03 -0.12 CCR-16S 571.21 571.88 -0.67 CCR-17D 585.47 582.64 2.83 CCR-17S 576.7 578.83 -2.13 CCR-18D 573.13 572.45 0.68 CCR-18S 570.08 570.90 -0.82 CCR-1D 623.81 623.54 0.27 CCR-1DA 624.23 623.89 0.34 CCR-20S 605.21 604.33 0.88 CCR-21D 630.78 630.71 0.07 CCR-21S 629.77 630.90 -1.13 CCR-22DA 631.01 631.75 -0.74 CCR-22S 632.15 632.78 -0.63 CCR-23D 631.91 631.60 0.31 CCR-23S 630.36 632.75 -2.39 CCR-BG-01DA 626.77 628.53 -1.76 CCR-BG-01S 627.11 628.58 -1.47 CP-01D 583.29 583.87 -0.58 CP-01S 585.38 583.67 1.71 CP-02D 576.89 575.33 1.56 CP-02S 575.82 575.28 0.54 CP-03D 568.19 567.09 1.10 CP-03S 568.27 567.05 1.22 CP-04D 568.87 567.25 1.62 CP-04S 567.86 567.26 0.60 CP-05D 570.84 570.34 0.50 CP-05S 572.2 570.25 1.95 CP-06BR 570.35 571.24 -0.89 Page 4 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-1 OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE CALIBRATED FLOW MODEL Well Observed Head Computed Head Residual Head CP-06D 571.67 569.58 2.09 CP-06S 572.46 569.08 3.38 GWA-01D 615.79 617.86 -2.07 GWA-01S 616.27 618.51 -2.24 GWA-02D 573.8 571.69 2.11 GWA-02S 570.92 571.10 -0.18 GWA-03BR 573.38 571.65 1.73 GWA-03BRA 574.42 571.65 2.77 GWA-03BRL 580.61 583.94 -3.33 GWA-03D 573.63 571.42 2.21 GWA-03S 571.55 571.12 0.43 GWA-04BR 571.59 571.16 0.43 GWA-04BRL 573.2 573.08 0.12 GWA-04D 570.92 570.41 0.51 GWA-04S 571.82 569.96 1.86 GWA-05BR 570.93 570.68 0.25 GWA-05BRA 570.54 571.11 -0.57 GWA-05BRL 573.51 574.03 -0.52 GWA-05D 570.92 570.51 0.41 GWA-05S 569.5 569.66 -0.16 GWA-06BR 588.76 590.23 -1.47 GWA-06BRA 589.27 590.36 -1.09 GWA-06BRL 592.09 590.87 1.22 GWA-06D 589.29 590.37 -1.08 GWA-06DA 591.37 590.30 1.07 GWA-06S 597.37 600.54 -3.17 GWA-07D 577.76 580.44 -2.68 GWA-07S 583.33 580.54 2.79 GWA-08D 610.33 608.85 1.48 GWA-08S 607.86 609.91 -2.05 GWA-09BR 637.33 637.81 -0.48 GWA-09D 637.05 637.85 -0.80 GWA-09S 636.95 637.99 -1.04 GWA-14D 626.43 627.25 -0.82 Page 5 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-1 OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE CALIBRATED FLOW MODEL Well Observed Head Computed Head Residual Head GWA-14DA 629.54 627.41 2.13 GWA-14S 628.15 627.31 0.84 GWA-15D 626.73 626.66 0.07 GWA-15S 626.93 626.66 0.27 GWA-16D 603.41 603.33 0.08 GWA-16S 604.85 604.64 0.21 GWA-17D 616.15 616.08 0.07 GWA-17S 616.94 616.00 0.94 GWA-18D 624.39 625.39 -1.00 GWA-18S 624.38 625.47 -1.09 GWA-19D 627 629.57 -2.57 GWA-19S 628.99 630.39 -1.40 GWA-1BR 615.76 616.84 -1.08 GWA-21 BR 635.74 637.56 -1.82 GWA-21D 636.24 638.32 -2.08 GWA-21DA 636.57 638.37 -1.80 GWA-21S 643.25 640.02 3.23 GWA-22D 631.83 631.19 0.64 GWA-22S 634.1 632.85 1.25 GWA-23D 638.77 639.15 -0.38 GWA-23S 638.79 639.23 -0.44 GWA-24BR 635.6 636.12 -0.52 GWA-24D 636.82 636.21 0.61 GWA-24S 638.99 636.34 2.65 GWA-24SA 635.04 636.27 -1.23 GWA-26D 636.72 637.81 -1.09 GWA-26S 637.14 637.90 -0.76 Prepared by: JFE Checked by: KWW Notes: Elevations are referenced to North American Vertical Datum 1988 (NAVD 88) Page 6 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-2 CALIBRATED HYDRAULIC CONDUCTIVITY PARAMETERS Hydrostratigraphic Unit Model Layers Spatial Zones (Number Corresponds to Figures 5-1 through 5-7) Horizontal Hydraulic Conductivity (ft/d) Anisotropy ratio, Kh:K„ Ash 4-11 #1 (Dam material) .03 1 4-11 #2 .1 1 4-11 #3 .3 1 4-11 #4 1 1 4-11 #5 (Baseline K for lower ash 2 1 4-11 #6 (Baseline K for u er ash 10 1 Sa rolite 12-14 #1 0.01 1 12-14 #2 0.05 1 12-14 #3 0.1 1 12-14 #4 0.2 1 12-14 #5 0.25 1 12-14 #6 0.3 1 12-14 #7 0.4 1 12-14 #8 0.5 1 12-14 #9 (Baseline K for sa rolite 1.0 1 12-14 #10 1.5 1 12-14 #11 2.0 1 12-14 #12 3.0 1 12-14 #13 4.0 1 12-14 #14 5.0 1 12-14 #15 6.0 1 12-14 #16 8.0 1 12-14 #17 9.0 1 12-14 #18 10.0 1 Transition zone 15-16 #1 0.1 1 15-16 #2 0.3 1 15-16 #3 0.5 1 15-16 #4 0.6 1 15-16 #5 1.0 1 15-16 #6 (Baseline K for transition zone 2.0 1 15-16 #7 3.0 1 15-16 #8 5.0 1 15-16 #9 6.0 1 15-16 #10 8.0 1 15-16 #11 10.0 1 Fractured Bedrock 17-19 #1 0.001 1 17-19 #2 0.005 1 17-19 #3 0.01 1 17-19 #4 0.03 1 1 Page 7 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-2 CALIBRATED HYDRAULIC CONDUCTIVITY PARAMETERS Spatial Zones Horizontal Hydrostratigraphic Model (Number Hydraulic Anisotropy Unit Layers Corresponds to Conductivity ratio, Figures 5-1 through (ft/d) Kh:K„ 5-7) 17-19 #5 0.05 1 17-19 #6 (Baseline K for 0.075 1 fractured bedrock 17-19 #7 0.1 1 17-19 #8 0.5 1 17-19 #9 1.0 1 17-19 #10 2.0 1 17-19 #11 3.0 1 17-19 #12 4.0 1 17-19 #13 5.0 1 Bedrock 20-26 #1 0.0005 1 #2 (Baseline K for 20-26 lower bedrock 0.005 1 20-26 #3 0.01 1 20-26 #4 0.015 1 20-26 #5 0.02 1 20-26 #6 0.05 1 20-26 #7 0.05 1 Notes: ft/d = feet per day Kh = horizontal hydraulic conductivity K = vertical hydraulic conductivity Prepared by: JFE Checked by: KWW Page 8 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-3 WATER BALANCE ON THE GROUNDWATER FLOW SYSTEM FOR PRE -DECANTED CONDITIONS Water Balance Components Flow In (gpm) Flow Out (gpm) Direct recharge to the Active Ash Basin 40 Direct recharge to the Retired Ash Basin 41 Direct recharge to watershed outside of ash basin 57 Ash basin ponds 428 155 Flow to drainages inside of the ash basins 39 Flow to drainages outside of the ash basin 27 Wells and septic return outside of the ash basin 12 12 Flow toward southeast of AAB 17 Flow towards drainage canal north of the RAB 5 Flow towards the coal pile 25 Flow through and under the dam 293 Notes• gpm = gallons per minute Prepared by: JFE Checked by: KWW Page 9 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-4 FLOW MODEL SENSITIVITY ANALYSIS Parameter 0.5x Calibrated Calibrated 2x Calibrated Kn in upper ash (10 ft/d) 2.38% 2.37% 2.35% Kn in lower ash (2 ft/d) 2.61% 2.37% 2.29% Kn in saprolite (1 ft/d) 3.76% 2.37% 3.30% Kn in TZ (2 ft/d) 2.66% 2.37% 2.94% Kn in upper fractured rock (0.075 ft/d) 2.48% 2.37% 2.45% Kn in bedrock (0.005 ft/d) 2.43% 2.37% 2.35% Regional recharge (0.0019 ft/d) 7.09% 2.37% 10.48% Prepared by: JFE Checked by: KWW Notes• Parameters are multiplied by 0.5 or 2 and the NRMSE is calculated. Results are expressed as normalized root mean square error (NRMSE) of the simulated and observed heads. Page 10 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-5 ASH BASIN COI SOURCE CONCENTRATIONS USED IN THE HISTORICAL TRANSPORT MODEL Source Concentration Zone ID Boron Source Concentration (Ng/L) Sulfate Source Concentration (mg/L) TDS Source Concentration (mg/L) # 1 50 5 10 #2 80 10 20 #3 100 15 30 #4 200 25 80 #5 250 40 100 #6 275 50 115 #7 350 70 160 #8 375 85 180 #9 400 100 200 #10 500 120 240 #11 650 130 260 #12 750 135 300 #13 900 140 320 #14 1000 150 400 #15 1100 160 415 #16 1200 180 450 #17 1500 200 500 #18 1600 215 515 #19 1700 250 530 #20 2000 275 550 #21 2200 300 590 #22 2500 450 600 #23 3400 800 800 #24 8400 1400 1000 #25 NA 1500 1600 #26 NA 2000 2600 #27 NA 2200 2800 #28 NA NA 3000 #29 NA NA 3100 #30 NA NA 4000 #31 NA NA 4400 Prepared by: JFE Checked by: KWW Notes: pg/L =. micrograms per liter mg/L = milligrams per liter Sources in the RAB and coal pile are active from 1957 to 2020; sources in the AAB are active from 1973 to 2020. Source concentration zone ID's for boron correspond to zone ID's in Figure 5-10a/b/c. Source concentration zone ID's for sulfate correspond to zone ID's in Figure 5-11a/b/c. Source concentration zone ID's for TDS correspond to zone ID's in Figure 5-12a/b. Page 11 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6a OBSERVED AND COMPUTED BORON (Ng/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (N9/L) Computed Boron (Ng/L) AB-01R 0 1 AB-02S 0 10 AB-02D 0 0 AB-04BR 0 21 AB-04D 0 23 AB-04S 0 30 AB-05 0 0 AB-06A 0 356 AB-06R 0 356 AB-09D 507 392 AB-09S 585 569 AB-10BR 537 1931 AB-10BRL 434 1572 AB-10D 0 1999 AB-10S 28 1376 AB-11D 0 3 AB-12D 0 0 AB-12S 0 0 AB-13D 0 0 AB-13S 0 0 AB-14BR 0 0 AB-14D 175 0 AB-20D 0 9 AB-20S 1670 1600 AB-21BRL 0 0 AB-21D 0 0 AB-21PWA 8470 8400 AB-21PWS 0 63 AB-21S 3410 3400 AB-21SL 7590 8400 AB-21SS 163 63 AB-22BR 1890 2074 AB-22BRL 1960 902 AB-22D 2040 2068 Page 12 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6a OBSERVED AND COMPUTED BORON (Ng/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) AB-22S 0 1092 AB-23BRU 0 49 AB-23S 399 380 AB-24BR 0 41 AB-24D 0 229 AB-24S 1070 1000 AB-24SL 552 500 AB-25BR 0 146 AB-25BRU 0 466 AB-25S 1220 1000 AB-25SL 825 850 AB-25SS 1250 1066 AB-26D 342 779 AB-26S 1060 1040 AB-27BR 135 259 AB-27D 318 488 AB-27S 393 400 AB-28D 89 398 AB-28S 1070 1000 AB-29D 371 456 AB-29S 364 375 AB-29SL 1700 1063 AB-29SS 631 712 AB-30D 0 327 AB-30S 86 100 AB-31S 1930 1564 AB-32D 621 1028 AB-32S 0 1625 AB-33D 230 794 AB-33S 783 1677 AB-33SS 2130 1569 AB-34D 0 36 AB-34S 325 358 AB-35BR 0 0 Page 13 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6a OBSERVED AND COMPUTED BORON (Ng/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) AB-35D 0 27 AB-35PWA 897 900 AB-35PWS 75 120 AB-35S 859 900 AB-36D 0 9 AB-36S 117 96 AB-37D 0 1 AB-37S 0 67 AB-38BR 0 20 AB-38D 0 45 AB-38S 72 75 AB-38SS 0 75 AB-39D 92 50 AB-39S 121 327 BG-01DA 0 0 BG-01S 0 0 BG-02BRA-2 0 0 BG-02D 0 0 BG-02S 0 0 BG-03D 0 0 BG-03S 0 0 BG-04BR 0 0 BG-04D 0 0 BG-04S 0 0 CP-01D 68 303 CP-01S 0 241 CP-02D 21 85 CP-02S 0 13 CP-03D 5 59 CP-03S 3 8 CP-04D 477 410 CP-04S 37 63 CP-05D 708 677 CP-05S 0 600 Page 14 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6a OBSERVED AND COMPUTED BORON (Ng/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) CP-06BR 20 0 CP-06D 1700 965 CP-06S 1530 1183 GWA-01BR 0 26 GWA-01D 40 45 GWA-01 S 0 24 GWA-02D 5 68 GWA-02S 4 6 GWA-03BRA 76 252 GWA-03D 136 753 GWA-03S 278 1008 GWA-04BR 366 8 GWA-04D 655 577 GWA-04S 1680 1215 GWA-05BRA 677 607 GWA-05D 649 889 GWA-05S 53 1179 GWA-06BRA 0 349 GWA-06DA 26 347 GWA-06S 278 0 GWA-07D 3 343 GWA-07S 0 73 GWA-08D 0 4 GWA-08S 0 0 GWA-09BR 0 6 GWA-09D 0 17 GWA-09S 0 15 GWA-14DA 0 0 GWA-14S 0 0 GWA-15D 0 1 GWA-15S 99 13 GWA-16D 0 0 GWA-16S 0 0 GWA-17D 0 2 Page 15 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6a OBSERVED AND COMPUTED BORON (Ng/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) GWA-17S 0 1 GWA-18D 0 20 GWA-18S 0 22 GWA-19D 0 0 GWA-19S 0 0 GWA-21BR 0 0 GWA-21 DA 4 0 GWA-21S 3 0 GWA-22D 0 0 GWA-22S 0 0 GWA-23D 0 0 GWA-23S 0 0 GWA-24BR 0 3 GWA-24D 0 8 GWA-24SA 0 1 GWA-26D 0 0 GWA-26S 0 0 GWA-3BRL 0 0 GWA-4BRL 244 0 GWA-5BRL 41 0 GWA-6BRL 119 0 CCR-01 DA 7 26 CCR-01S 13 95 CCR-02D 72 118 CCR-02S 4 155 CCR-03DA 14 365 CCR-03S 460 413 CCR-04DA 48 362 CCR-04SA 230 72 CCR-05D 46 258 CCR-05S 508 343 CCR-06D 27 686 CCR-06S 627 749 CCR-07D 708 587 Page 16 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6a OBSERVED AND COMPUTED BORON (Ng/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (N9/L) Computed Boron (Ng/L) CCR-07S 1540 1812 CCR-08D 1290 586 CCR-08S 1400 1868 CCR-09D 1780 1236 CCR-09S 1260 1844 CCR-11 DA 1330 821 CCR-11S 265 852 CCR-14D 557 650 CCR-14S 170 976 CCR-16BR 522 681 CCR-16D 609 871 CCR-16S 1700 1434 CCR-17D 1470 1452 CCR-17S 1380 1804 CCR-18D 314 533 CCR-18S 21 302 CCR-20D 518 777 CCR-20S 167 501 CCR-21D 520 199 CCR-21S 1440 973 CCR-22DA 14 11 CCR-22S 4 48 CCR-23 D 4 34 CCR-23S 3 72 CCR-26BR 0 308 CCR-26D 0 233 CCR-26S 238 137 CCR-BG-01BR 40 0 CCR-BG-01DA 5 0 Notes: pg/L = micrograms per liter Prepared by: JFE Checked by: KWW Page 17 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6b OBSERVED AND COMPUTED SULFATE (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) AB-01 R 119 0 AB-02 0.57 0 AB-02D 0 0 AB-04BR 3.9 4 AB-04D 1.6 4 AB-04S 10.2 5 AB-05 1.1 0 AB-06A 31.9 58 AB-06R 30.9 58 AB-09D 54.9 61 AB-09S 38.1 58 AB-10BR 48.4 97 AB-10BRL 153 90 AB-10D 30.8 90 AB-10S 20.6 65 AB-11D 0 1 AB-12D 4 0 AB-12S 0 0 AB-13D 0 0 AB-13S 1 0 AB-14BR 6.3 0 AB-14D 30.5 0 AB-20D 4.3 4 AB-20S 127 130 AB-21BRL 8.8 0 AB-21D 7.3 0 AB-21S 67.8 140 AB-21SL 139 140 AB-21SS 0.54 9 AB-22BR 33.6 111 AB-22BRL 46.4 77 AB-22D 39.7 96 AB-22S 4.2 52 Page 18 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6b OBSERVED AND COMPUTED SULFATE (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) AB-23BRU 17.1 4 AB-23S 14.9 15 AB-24BR 3.6 3 AB-24D 24.1 9 AB-24S 217 215 AB-24SL 15.1 15 AB-25BR 3.3 5 AB-25BRU 11.3 12 AB-25S 41.3 25 AB-25SL 24.4 25 AB-25SS 32 23 AB-26D 46.9 21 AB-26S 69.8 30 AB-27BR 31.9 93 AB-27D 30.6 120 AB-27S 67.4 48 AB-28D 18.2 23 AB-28S 209 250 AB-29D 48.1 106 AB-29S 38 40 AB-29SL 138 121 AB-29SS 97.6 122 AB-30D 26.3 20 AB-30S 460 450 AB-31S 131 112 AB-32D 27.8 77 AB-32S 1.9 123 AB-33D 8.7 112 AB-33S 180 204 AB-33SS 118 190 AB-34D 1.3 12 AB-34S 131 100 AB-35BR 2 0 Page 19 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6b OBSERVED AND COMPUTED SULFATE (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) AB-35D 6.1 2 AB-35PWS 6.9 9 AB-35S 84.2 85 AB-36D 5.1 1 AB-36S 1.3 5 AB-37D 2.9 0 AB-37S 2.1 3 AB-38BR 17.2 2 AB-38D 14.4 4 AB-38S 1.5 5 AB-38SS 2.6 5 AB-39D 36.9 13 AB-39S 4.4 13 BG-01BR 7.5 0 BG-01DA 1.4 0 BG-01S 0 0 BG-02BRA-2 33.3 0 BG-02D 1.3 0 BG-02S 0 0 BG-03D 0.52 0 BG-03S 0 0 BG-04BR 2.7 0 BG-04D 1.3 0 BG-04S 0 0 CCR-01 DA 1.6 2 CCR-01S 2.8 5 CCR-02D 14.2 13 CCR-02S 0.7 5 CCR-03 DA 10.4 19 CCR-03S 120 98 CCR-04DA 173 924 CCR-04SA 899 1107 CCR-05D 41.8 797 Page 20 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6b OBSERVED AND COMPUTED SULFATE (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) CCR-05S 773 1024 CCR-06D 4.9 421 CCR-06S 2200 2200 CCR-07D 97.3 108 CCR-07S 271 275 CCR-08D 91.5 79 CCR-08S 212 275 CCR-09D 162 121 CCR-09S 201 185 CCR-11 DA 84.5 59 CCR-11S 69.1 64 CCR-14D 46.7 32 CCR-14S 19.4 25 CCR-16BR 37.1 67 CCR-16D 41.1 78 CCR-16S 113 87 CCR-17D 53 63 CCR-17S 47.3 63 CCR-18D 46.8 107 CCR-18S 65.7 56 CCR-20D 47 116 CCR-20S 14.4 74 CCR-21 D 57.3 34 CCR-21S 28.4 85 CCR-22DA 26.9 4 CCR-22S 3 7 CCR-23D 2.4 7 CCR-23S 0.74 11 CCR-26BR 151 205 CCR-26D 56.9 210 CCR-26S 3.8 198 CCR-BG-01DA 1.4 0 CCR-BG-01S 1.3 0 Page 21 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6b OBSERVED AND COMPUTED SULFATE (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) CP-01D 636 780 CP-01S 304 793 CP-02D 2050 1261 CP-02S 1450 1821 CP-03D 478 1062 CP-03S 955 877 CP-04D 0.56 588 CP-04S 57.1 91 CP-05D 215 527 CP-05S 10.7 297 CP-06BR 12 0 CP-06D 108 130 CP-06S 156 108 GWA-01BR 16.1 8 GWA-01D 12 11 GWA-01S 0 5 GWA-02D 0.53 17 GWA-02S 0 2 GWA-03BRA 15.2 8 GWA-03BRL 6.2 0 GWA-03D 11.5 20 GWA-03S 42.8 31 GWA-04BR 51.3 1 GWA-04BRL 54 0 GWA-04D 75.6 51 GWA-04S 144 94 GWA-05BRA 70.1 48 GWA-05BRL 38.4 0 GWA-05D 37.4 69 GWA-05S 159 89 GWA-06BRA 150 436 GWA-06BRL 49.4 5 GWA-06DA 428 892 Page 22 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6b OBSERVED AND COMPUTED SULFATE (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) GWA-06S 1390 1100 GWA-07D 120 124 GWA-07S 85.5 105 GWA-08D 1.2 0 GWA-08S 2.3 0 GWA-09BR 12 2 GWA-09D 2.7 4 GWA-09S 14.9 2 GWA-14DA 1.9 0 GWA-14S 0 0 GWA-15D 4.1 0 GWA-15S 12.2 1 GWA-16D 1.1 0 GWA-16S 0.71 0 GWA-17D 3.5 0 GWA-17S 4.7 0 GWA-18D 2.1 2 GWA-18S 0 2 GWA-19D 3.6 0 GWA-19S 0 0 GWA-21BR 3.3 0 GWA-21 DA 1.2 0 GWA-21S 0 0 GWA-22D 0.85 0 GWA-22S 0.87 0 GWA-23D 1.7 0 GWA-23S 0.96 0 GWA-24BR 11.5 1 GWA-24D 4.7 2 GWA-24SA 0 0 GWA-26D 13.4 0 GWA-26S 0.62 0 Notes• mg/L = milligrams per liter Prepared by: JFE Checked by: KWW Page 23 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6c OBSERVED AND COMPUTED TDS (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) AB-01 R 236 0 AB-02 36 19 AB-02D 76 0 AB-04BR 164 9 AB-04D 81 8 AB-04S 71 10 AB-05 0 0 AB-06A 134 156 AB-06R 138 156 AB-09D 217 227 AB-09S 149 259 AB-10BR 285 451 AB-10BRL 506 422 AB-10D 146 384 AB-10S 118 213 AB-11D 97 3 AB-12D 0 0 AB-12S 135 0 AB-13D 119 0 AB-13S 75 0 AB-14BR 122 0 AB-14D 101 0 AB-20D 128 7 AB-20S 417 415 AB-21BRL 135 0 AB-21D 0 0 AB-21S 525 415 AB-21SL 412 415 AB-21SS 99 35 AB-22BR 285 560 AB-22BRL 299 397 AB-22D 250 430 AB-22S 60 116 Page 24 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6c OBSERVED AND COMPUTED TDS (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) AB-23BRU 0 29 AB-23S 117 112 AB-24BR 105 20 AB-24D 0 72 AB-24S 501 500 AB-24SL 108 115 AB-25BR 0 41 AB-25BRU 0 93 AB-25S 195 200 AB-25SL 160 199 AB-25SS 173 188 AB-26D 188 166 AB-26S 152 200 AB-27BR 192 295 AB-27D 145 385 AB-27S 438 325 AB-28D 182 180 AB-28S 589 590 AB-29D 182 344 AB-29S 188 300 AB-29SL 276 368 AB-29SS 235 389 AB-30D 158 144 AB-30S 797 800 AB-31S 236 363 AB-32D 168 265 AB-32S 85 318 AB-33D 158 307 AB-33S 487 449 AB-33SS 224 433 AB-34D 105 75 AB-34S 418 377 AB-35BR 100 0 Page 25 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6c OBSERVED AND COMPUTED TDS (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) AB-35D 0 35 AB-35PWS 213 121 AB-35S 516 515 AB-36D 0 27 AB-36S 209 192 AB-37D 140 2 AB-37S 121 121 AB-38BR 207 4 AB-38D 191 7 AB-38S 154 10 AB-38SS 119 10 AB-39D 222 26 AB-39S 252 26 BG-01BR 166 0 BG-01DA 110 0 BG-01S 36 0 BG-02BRA-2 222 0 BG-02D 125 0 BG-02S 133 0 BG-03D 130 0 BG-03S 136 0 BG-04BR 125 0 BG-04D 143 0 BG-04S 138 0 CCR-01 DA 133 4 CCR-01S 30 10 CCR-02D 287 25 CCR-02S 36 10 CCR-03 DA 260 38 CCR-03S 238 197 CCR-04DA 433 1510 CCR-04SA 1450 2005 CCR-05D 192 1386 Page 26 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6c OBSERVED AND COMPUTED TDS (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) CCR-05S 1190 1631 CCR-06D 133 896 CCR-06S 3150 3100 CCR-07D 233 297 CCR-07S 565 550 CCR-08D 219 252 CCR-08S 403 550 CCR-09D 294 322 CCR-09S 309 415 CCR-11DA 196 238 CCR-11S 246 238 CCR-14D 190 180 CCR-14S 112 200 CCR-16BR 166 273 CCR-16D 191 292 CCR-16S 259 225 CCR-17D 317 236 CCR-17S 222 182 CCR-18D 290 576 CCR-18S 138 140 CCR-20D 294 623 CCR-20S 141 255 CCR-21D 344 145 CCR-21S 169 346 CCR-22DA 193 9 CCR-22S 100 21 CCR-23 D 149 15 CCR-23S 66 22 CCR-26BR 381 349 CCR-26D 217 359 CCR-26S 84 345 CCR-BG-01DA 129 0 CCR-BG-01S 0 0 Page 27 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6c OBSERVED AND COMPUTED TDS (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) CP-01D 1110 1308 CP-01S 545 1369 CP-02D 3400 2288 CP-02S 2840 3113 CP-03D 908 1897 CP-03S 1460 1454 CP-04D 338 1157 CP-04S 133 178 CP-05D 506 1047 CP-05S 116 592 CP-06BR 129 0 CP-06D 263 327 CP-06S 320 249 GWA-01BR 170 30 GWA-01D 185 44 GWA-01S 74 20 GWA-02D 91 85 GWA-02S 42 8 GWA-03BRA 139 63 GWA-03BRL 126 0 GWA-03D 139 159 GWA-03S 141 196 GWA-04BR 206 5 GWA-04BRL 232 0 GWA-04D 212 211 GWA-04S 278 312 GWA-05BRA 214 205 GWA-05BRL 211 0 GWA-05D 180 245 GWA-05S 286 264 GWA-06BRA 378 729 GWA-06BRL 272 9 GWA-06DA 838 1475 Page 28 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-6c OBSERVED AND COMPUTED TDS (mg/L) CONCENTRATIONS IN MONITORING WELLS Well Name Observed Sulfate (mg/L) Computed Sulfate (mg/L) GWA-06S 2130 2200 GWA-07D 310 216 GWA-07S 164 189 GWA-08D 122 1 GWA-08S 204 0 GWA-09BR 143 4 GWA-09D 102 7 GWA-09S 98 5 GWA-14DA 145 0 GWA-14S 0 0 GWA-15D 171 2 GWA-15S 114 24 GWA-16D 92 0 GWA-16S 95 0 GWA-17D 114 1 GWA-17S 79 0 GWA-18D 113 4 GWA-18S 106 4 GWA-19D 159 0 GWA-19S 52 0 GWA-21BR 185 0 GWA-21DA 150 0 GWA-21S 30 0 GWA-22D 176 0 GWA-22S 0 0 GWA-23D 134 0 GWA-23S 26 0 GWA-24BR 163 2 GWA-24D 162 5 GWA-24SA 35 1 GWA-26D 132 0 GWA-26S 73 0 Notes• mg/L = milligrams per liter Prepared by: JFE Checked by: KWW Page 29 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7a TRANSPORT MODEL SENSITIVITY TO THE BORON Kd VALUES Well Boron (Ng/L) Boron Model Calibrated Model, Low Kd Model, High Kd NRMSE 4.3% 4.6% 4.8% AB-01R 0 1 4 0 AB-02 0 10 10 9 AB-02D 0 0 0 0 AB-04BR 0 21 35 1 AB-04D 0 23 29 4 AB-04S 0 30 33 12 AB-05 0 0 0 0 AB-06A 0 356 357 302 AB-06R 0 356 357 302 AB-09D 507 392 517 35 AB-09S 585 569 584 358 AB-10BR 537 1931 2027 1353 AB-10BRL 434 1572 1942 585 AB-10D 0 1999 2019 1576 AB-10S 28 1376 1382 1195 AB-11D 0 3 16 0 AB-12D 0 0 1 0 AB- 12S 0 0 1 0 AB-13D 0 0 0 0 AB-13S 0 0 0 0 AB-14BR 0 0 0 0 AB-14D 175 0 0 0 AB-20D 0 9 37 0 AB-20S 1670 1600 1600 1600 AB-21BRL 0 0 0 0 AB-21D 0 0 0 0 AB-21 PWA 8470 8400 8400 8400 AB-21PWS 0 63 274 3 AB-21S 3410 3400 3400 3400 AB-21SL 7590 8400 8400 8400 AB-21SS 163 63 274 3 AB-22BR 1890 2074 2104 1835 AB-22BRL 1960 902 1773 41 AB-22D 2040 2068 2078 1962 AB-22S 0 1092 1092 1082 AB-23BRU 0 49 162 1 AB-23S 399 380 394 292 AB-24BR 0 41 138 0 AB-24D 0 229 380 20 AB-24S 1070 1000 1000 1000 AB-24SL 552 500 500 500 AB-25BR 0 146 582 1 AB-25BRU 0 466 1063 16 AB-25S 1220 1000 1000 1000 AB-25SL 825 850 872 635 Page 30 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7a TRANSPORT MODEL SENSITIVITY TO THE BORON Kd VALUES Well Boron (Ng/L) Boron Model Calibrated Model, Low Ka Model, High Kd NRMSE 4.3% 4.6% 4.8% AB-25SS 1250 1066 1238 360 AB-26D 342 779 877 493 AB-26S 1060 1040 1040 1040 AB-27BR 135 259 465 18 AB-27D 318 488 534 299 AB-27S 393 400 400 400 AB-28D 89.3 398 446 205 AB-28S 1070 1000 1000 1000 AB-29D 371 456 595 45 AB-29S 364 375 375 375 AB-29SL 1700 1063 1065 935 AB-29SS 631 712 729 403 AB-30D 0 327 371 78 AB-30S 85.6 100 100 100 AB-31S 1930 1564 1562 1539 AB-32D 621 1028 1002 839 AB-32S 0 1625 1599 1491 AB-33D 230 794 810 528 AB-33S 783 1677 1733 1162 AB-33SS 2130 1569 1626 970 AB-34D 0 36 46 5 AB-34S 325 358 355 281 AB-35BR 0 0 0 0 AB-35D 0 27 61 9 AB-35PWA 896.8 900 900 900 AB-35PWS 74.7 120 153 83 AB-35S 859 900 900 900 AB-36D 0 9 15 0 AB-36S 117 96 96 81 AB-37D 0 1 1 0 AB-37S 0 67 67 65 AB-38BR 0 20 48 0 AB-38D 0 45 68 4 AB-38S 72.2 75 79 46 AB-38SS 0 75 79 46 AB-39D 91.6 50 112 1 AB-39S 121 327 365 187 BG-01 DA 0 0 0 0 BG-01S 0 0 0 0 BG-02BRA-2 0 0 0 0 BG-02D 0 0 0 0 BG-02S 0 0 0 0 BG-03D 0 0 0 0 BG-03S 0 0 0 0 BG-04BR 0 0 0 0 Page 31 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7a TRANSPORT MODEL SENSITIVITY TO THE BORON Kd VALUES Well Boron (Ng/L) Boron Model Calibrated Model, Low Kd Model, High Kd NRMSE 4.3% 4.6% 4.8% BG-04D 0 0 0 0 BG-04S 0 0 0 0 CP-01D 68.3 303 366 50 CP-01S 0 241 307 20 CP-02D 21.3 85 241 0 CP-02S 0 13 76 0 CP-03D 5 59 200 0 CP-03S 3.4 8 40 0 CP-04D 477 410 531 66 CP-04S 37 63 91 2 CP-05D 708 677 766 395 CP-05S 0 600 647 314 CP-06BR 19.9 0 4 0 CP-06D 1700 965 1062 115 CP-06S 1530 1183 1294 522 GWA-01BR 0 26 127 0 GWA-01D 40 45 168 0 GWA-01S 0 24 63 0 GWA-02D 5.2 68 257 0 GWA-02S 3.7 6 33 0 GWA-03BRA 75.9 252 400 53 GWA-03D 136 753 834 483 GWA-03S 278 1008 1011 999 GWA-04BR 366 8 29 0 GWA-04D 655 577 775 296 GWA-04S 1680 1215 1272 1068 GWA-05BRA 677 607 607 407 GWA-05D 649 889 876 677 GWA-05S 53.4 1179 1169 859 GWA-06BRA 0 349 398 173 GWA-06DA 25.7 347 392 164 GWA-06S 278 0 0 0 GWA-07D 3.4 343 394 130 GWA-07S 0 73 129 1 GWA-08D 0 4 7 0 GWA-08S 0 0 0 0 GWA-09BR 0 6 18 0 GWA-09D 0 17 27 1 GWA-09S 0 15 16 10 GWA-14DA 0 0 0 0 GWA-14S 0 0 0 0 GWA-15D 0 1 1 0 GWA-15S 98.6 13 13 8 GWA-16D 0 0 0 0 GWA-16S 0 0 0 0 Page 32 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7a TRANSPORT MODEL SENSITIVITY TO THE BORON Kd VALUES Well Boron (Ng/L) Boron Model Calibrated Model, Low Kd Model, High Kd NRMSE 4.3% 4.6% 4.8% GWA-17D 0 2 6 0 GWA-17S 0 1 2 0 GWA-18D 0 20 34 0 GWA-18S 0 22 34 1 GWA-19D 0 0 0 0 GWA-19S 0 0 0 0 GWA-21BR 0 0 0 0 GWA-21 DA 3.8 0 0 0 GWA-21S 3 0 0 0 GWA-22D 0 0 0 0 GWA-22S 0 0 0 0 GWA-23D 0 0 0 0 GWA-23S 0 0 0 0 GWA-24BR 0 3 15 0 GWA-24D 0 8 20 0 GWA-24SA 0 1 3 0 GWA-26D 0 0 0 0 GWA-26S 0 0 0 0 GWA-3BRL 0 0 0 0 GWA-4BRL 244 0 1 0 GWA-SBRL 40.7 0 0 0 GWA-6BRL 119 0 10 0 CCR-01DA 7.2 26 40 1 CCR-01S 12.8 95 96 91 CCR-02D 72.2 118 168 8 CCR-02S 4 155 160 112 CCR-03DA 13.9 365 434 106 CCR-03S 460 413 471 171 CCR-04DA 48 362 408 174 CCR-04SA 230 72 115 16 CCR-05D 45.7 258 340 36 CCR-05S 508 343 455 133 CCR-06D 27.1 686 710 418 CCR-06S 627 749 930 146 CCR-07D 708 587 614 298 CCR-07S 1540 1812 1888 1192 CCR-08D 1290 586 605 182 CCR-08S 1400 1868 1896 1087 CCR-09D 1780 1236 1360 88 CCR-09S 1260 1844 1970 324 CCR-11DA 1330 821 851 661 CCR-11S 265 852 867 534 CCR-14D 557 650 772 322 CCR-14S 170 976 976 975 CCR-16BR 522 681 833 443 Page 33 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7a TRANSPORT MODEL SENSITIVITY TO THE BORON Kd VALUES Well Boron /L Boron Model Calibrated Model, Low Kd Model, High Kd NRMSE 4.3% 4.6% 4.8% CCR-16D 609 871 955 712 CCR-16S 1700 1434 1437 1423 CCR-17D 1470 1452 1649 551 CCR-17S 1380 1804 1808 1737 CCR-18D 314 533 654 213 CCR-18S 21.4 302 303 270 CCR-20D 518 777 872 279 CCR-20S 167 501 511 422 CCR-21D 520 199 513 11 CCR-21S 1440 973 1174 280 CCR-22DA 14.3 11 45 0 CCR-22S 4.3 48 64 10 CCR-23D 4.2 34 60 2 CCR-23S 3.2 72 74 57 CCR-26BR 0 308 377 60 CCR-26D 0 233 336 6 CCR-26S 238 137 242 1 CCR-BG-01BR 39.8 0 0 0 CCR-BG-01DA 5.4 0 1 0 1 0 Prepared by: JFE Checked by: KWW Notes: Boron concentrations are shown for the calibrated model, and for models where the Kd is increased by a factor of 5 and decreased by a factor of 1/5. Page 34 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7b TRANSPORT MODEL SENSITIVITY TO THE SULFATE Kd VALUES Well Sulfate (mg/L) Sulfate Model Calibrated Model, Low Ka Model, High Ka NRMSE 6.4% 7.0% 6.9% AB-01 R 119 0 0 0 AB-02 0.57 0 0 0 AB-02D 0 0 0 0 AB-04BR 3.9 4 6 1 AB-04D 1.6 4 4 2 AB-04S 10.2 5 5 3 AB-05 1.1 0 0 0 AB-06A 31.9 58 58 57 AB-06R 30.9 58 58 57 AB-09D 54.9 61 69 16 AB-09S 38.1 58 57 47 AB-10BR 48.4 97 100 82 AB-10BRL 153 90 99 51 AB-10D 30.8 90 90 84 AB-10S 20.6 65 65 63 AB-11D 0 1 3 0 AB-12D 4 0 0 0 AB- 12S 0 0 0 0 AB-13D 0 0 0 0 AB-13S 1 0 0 0 AB-14BR 6.3 0 0 0 AB-14D 30.5 0 0 0 AB-20D 4.3 4 7 0 AB-20S 127 130 130 130 AB-21BRL 8.8 0 0 0 AB-21D 7.3 0 0 0 AB-21S 67.8 140 140 140 AB-21SL 139 140 140 140 AB-21SS 0.54 9 24 0 AB-22BR 33.6 111 112 104 AB-22BRL 46.4 77 104 12 AB-22D 39.7 96 96 93 AB-22S 4.2 52 52 52 AB-23BRU 17.1 4 7 0 AB-23S 14.9 15 15 13 AB-24BR 3.6 3 5 0 AB-24D 24.1 9 12 3 AB-24S 217 215 215 215 AB-24SL 15.1 15 15 15 AB-25BR 3.3 5 10 0 AB-25BRU 11.3 12 17 2 AB-25S 41.3 25 25 25 AB-25SL 24.4 25 25 23 AB-25SS 32 23 24 16 AB-26D 46.9 21 22 16 Page 35 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7b TRANSPORT MODEL SENSITIVITY TO THE SULFATE Kd VALUES Well Sulfate m /L Sulfate Model Calibrated Model, Low Kd Model, High Kd NRMSE 6.4% 7.0% 6.9% AB-26S 69.8 30 30 30 AB-27BR 31.9 93 110 26 AB-27D 30.6 120 121 105 AB-27S 67.4 48 48 48 AB-28D 18.2 23 24 17 AB-28S 209 250 250 250 AB-29D 48.1 106 110 53 AB-29S 38 40 40 40 AB-29SL 138 121 121 119 AB-29SS 97.6 122 122 109 AB-30D 26.3 20 21 13 AB-30S 460 450 450 450 AB-31S 131 112 112 108 AB-32D 27.8 77 76 69 AB-32S 1.9 123 122 118 AB-33D 8.7 112 114 82 AB-33S 180 204 208 163 AB-33SS 118 190 194 145 AB-34D 1.3 12 12 6 AB-34S 131 100 100 98 AB-35BR 2 0 0 0 AB-35D 6.1 2 3 1 AB-35PWS 6.9 9 10 8 AB-35S 84.2 85 85 85 AB-36D 5.1 1 1 0 AB-36S 1.3 5 5 5 AB-37D 2.9 0 0 0 AB-37S 2.1 3 3 3 AB-38BR 17.2 2 3 0 AB-38D 14.4 4 4 1 AB-38S 1.5 5 5 4 AB-38SS 2.6 5 5 4 AB-39D 36.9 13 17 1 AB-39S 4.4 13 15 4 BG-01BR 7.5 0 0 0 BG-01DA 1.4 0 0 0 BG-01S 0 0 0 0 BG-02BRA-2 33.3 0 0 0 BG-02D 1.3 0 0 0 BG-02S 0 0 0 0 BG-03D 0.52 0 0 0 BG-03S 0 0 0 0 BG-04BR 2.7 0 0 0 BG-04D 1.3 0 0 0 BG-04S 0 0 0 0 Page 36 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7b TRANSPORT MODEL SENSITIVITY TO THE SULFATE Kd VALUES Well Sulfate m /L Sulfate Model Calibrated Model, Low Kd Model, High Kd NRMSE 6.4% 7.0% 6.9% CCR-01 DA 1.6 2 3 0 CCR-01S 2.8 5 5 5 CCR-02D 14.2 13 14 3 CCR-02S 0.7 5 5 5 CCR-03 DA 10.4 19 21 11 CCR-03S 120 98 101 67 CCR-04DA 173 924 939 801 CCR-04SA 899 1107 1313 551 CCR-05D 41.8 797 814 439 CCR-05S 773 1024 1235 412 CCR-06D 4.9 421 427 354 CCR-06S 2200 2200 2200 2200 CCR-07D 97.3 108 110 72 CCR-07S 271 275 275 275 CCR-08D 91.5 79 80 44 CCR-08S 212 275 275 275 CCR-09D 162 121 123 54 CCR-09S 201 185 187 127 CCR-11 DA 84.5 59 59 54 CCR-11S 69.1 64 63 52 CCR-14D 46.7 32 39 19 CCR-14S 19.4 25 25 25 CCR-16BR 37.1 67 73 53 CCR-16D 41.1 78 81 70 CCR-16S 113 87 87 87 CCR-17D 53 63 71 37 CCR-17S 47.3 63 63 62 CCR-18D 46.8 107 118 71 CCR-18S 65.7 56 56 55 CCR-20D 47 116 122 78 CCR-20S 14.4 74 74 70 CCR-21 D 57.3 34 58 5 CCR-21S 28.4 85 93 42 CCR-22DA 26.9 4 8 0 CCR-22S 3 7 8 3 CCR-23D 2.4 7 9 2 CCR-23S 0.74 11 11 10 CCR-26BR 151 205 216 119 CCR-26D 56.9 210 238 45 CCR-26S 3.8 198 248 19 CCR-BG-01DA 1.4 0 0 0 CCR-BG-01S 1.3 0 0 0 CP-01D 636 780 810 465 CP-01S 304 793 840 368 CP-02D 2050 1261 1415 554 Page 37 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7b TRANSPORT MODEL SENSITIVITY TO THE SULFATE Kd VALUES Well Sulfate m /L Sulfate Model Calibrated Model, Low Kd Model, High Kd NRMSE 6.4% 7.0% 6.9% CP-02S 1450 1821 1902 1384 CP-03D 478 1062 1318 155 CP-03S 955 877 1127 113 CP-04D 0.56 588 663 166 CP-04S 57.1 91 107 12 CP-05D 215 527 559 351 CP-05S 10.7 297 312 199 CP-06BR 12 0 1 0 CP-06D 108 130 133 75 CP-06S 156 108 110 63 GWA-01BR 16.1 8 16 0 GWA-01D 12 11 20 0 GWA-01S 0 5 7 0 GWA-02D 0.53 17 36 1 GWA-02S 0 2 5 0 GWA-03BRA 15.2 8 11 4 GWA-03BRL 6.2 0 0 0 GWA-03D 11.5 20 21 16 GWA-03S 42.8 31 31 31 GWA-04BR 51.3 1 3 0 GWA-04BRL 54 0 0 0 GWA-04D 75.6 51 53 30 GWA-04S 144 94 94 84 GWA-05BRA 70.1 48 48 38 GWA-05BRL 38.4 0 0 0 GWA-05D 37.4 69 68 59 GWA-05S 159 89 88 78 GWA-06BRA 150 436 437 397 GWA-06BRL 49.4 5 21 0 GWA-06DA 428 892 917 742 GWA-06S 1390 1100 1100 1100 GWA-07D 120 124 128 102 GWA-07S 85.5 105 134 15 GWA-08D 1.2 0 0 0 GWA-08S 2.3 0 0 0 GWA-09BR 12 2 3 0 GWA-09D 2.7 4 4 1 GWA-09S 14.9 2 2 2 GWA-14DA 1.9 0 0 0 GWA-14S 0 0 0 0 GWA-15D 4.1 0 0 0 GWA-15S 12.2 1 1 1 GWA-16D 1.1 0 0 0 GWA-16S 0.71 0 0 0 GWA-17D 3.5 0 0 0 Page 38 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7b TRANSPORT MODEL SENSITIVITY TO THE SULFATE Kd VALUES Well Sulfate m /L Sulfate Model Calibrated Model, Low Kd Model, High Kd NRMSE 6.4% 7.0% 6.9% GWA-17S 4.7 0 0 0 GWA-18D 2.1 2 2 0 GWA-18S 0 2 2 0 GWA-19D 3.6 0 0 0 GWA-19S 0 0 0 0 GWA-21BR 3.3 0 0 0 GWA-21 DA 1.2 0 0 0 GWA-21S 0 0 0 0 GWA-22D 0.85 0 0 0 GWA-22S 0.87 0 0 0 GWA-23D 1.7 0 0 0 GWA-23S 0.96 0 0 0 GWA-24BR 11.5 1 3 0 GWA-24D 4.7 2 3 0 GWA-24SA 0 0 1 0 GWA-26D 13.4 0 0 0 GWA-26S 0.62 0 0 0 Prepared by: JFE Checked by: KWW Notes• Sulfate concentrations are shown for the calibrated model, and for models where the Kd is increased by a factor of 5 and decreased by a factor of 1/5. Page 39 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7c TRANSPORT MODEL SENSITIVITY TO THE TDS Kd VALUES Well TDS (mg/L) TDS Model Calibrated Model, Low Ka Model, High Ka NRMSE 7.0% 7.8% 7.6% AB-01 R 236 0 0 0 AB-02 36 19 19 19 AB-02D 76 0 0 0 AB-04BR 164 9 11 2 AB-04D 81 8 9 3 AB-04S 71 10 10 7 AB-05 0 0 0 0 AB-06A 134 156 156 149 AB-06R 138 156 156 149 AB-09D 217 227 258 67 AB-09S 149 259 259 220 AB-10BR 285 451 465 369 AB-10BRL 506 422 472 225 AB-10D 146 384 387 350 AB-10S 118 213 214 201 AB-11D 97 3 6 0 AB-12D 0 0 0 0 AB- 12S 135 0 0 0 AB-13D 119 0 0 0 AB-13S 75 0 0 0 AB-14BR 122 0 0 0 AB-14D 101 0 0 0 AB-20D 128 7 13 0 AB-20S 417 415 415 415 AB-21BRL 135 0 0 0 AB-21D 0 0 0 0 AB-21S 525 415 415 415 AB-21SL 412 415 415 415 AB-21SS 99 35 100 2 AB-22BR 285 560 567 516 AB-22BRL 299 397 550 59 AB-22D 250 430 432 413 AB-22S 60 116 116 115 AB-23BRU 0 29 55 3 AB-23S 117 112 114 100 AB-24BR 105 20 37 1 AB-24D 0 72 91 20 AB-24S 501 500 500 500 AB-24SL 108 115 115 115 AB-25BR 0 41 81 2 AB-25BRU 0 93 134 15 AB-25S 195 200 200 200 AB-25SL 160 199 200 185 AB-25SS 173 188 196 126 AB-26D 1 188 166 1 179 1 132 Page 40 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7c TRANSPORT MODEL SENSITIVITY TO THE TDS Kd VALUES Well TDS (mg/L) TDS Model Calibrated Model, Low Ka Model, High Ka NRMSE 7.0% 7.8% 7.6% AB-26S 152 200 200 200 AB-27BR 192 295 354 80 AB-27D 145 385 390 334 AB-27S 438 325 325 325 AB-28D 182 180 185 130 AB-28S 589 590 590 590 AB-29D 182 344 363 166 AB-29S 188 300 300 300 AB-29SL 276 368 368 357 AB-29SS 235 389 390 343 AB-30D 158 144 151 84 AB-30S 797 800 800 800 AB-31S 236 363 364 335 AB-32D 168 265 266 198 AB-32S 85 318 318 283 AB-33D 158 307 311 191 AB-33S 487 449 459 360 AB-33SS 224 433 444 324 AB-34D 105 75 77 26 AB-34S 418 377 375 356 AB-35BR 100 0 1 0 AB-35D 0 35 39 20 AB-35PWS 213 121 123 100 AB-35S 516 515 515 515 AB-36D 0 27 30 4 AB-36S 209 192 192 185 AB-37D 140 2 2 1 AB-37S 121 121 121 121 AB-38BR 207 4 7 0 AB-38D 191 7 9 2 AB-38S 154 10 10 8 AB-38SS 119 10 10 8 AB-39D 222 26 34 2 AB-39S 252 26 30 9 BG-01BR 166 0 0 0 BG-01DA 110 0 0 0 BG-01S 36 0 0 0 BG-02BRA-2 222 0 0 0 BG-02D 125 0 0 0 BG-02S 133 0 0 0 BG-03D 130 0 0 0 BG-03S 136 0 0 0 BG-04BR 125 0 0 0 BG-04D 143 0 0 0 BG-04S 138 0 0 0 Page 41 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7c TRANSPORT MODEL SENSITIVITY TO THE TDS Kd VALUES Well TDS (mg/L) TDS Model Calibrated Model, Low Ka Model, High Ka NRMSE 7.0% 7.8% 7.6% CCR-01DA 133 4 5 1 CCR-01S 30 10 10 9 CCR-02D 287 25 28 5 CCR-02S 36 10 11 9 CCR-03DA 260 38 42 22 CCR-03S 238 197 203 135 CCR-04DA 433 1510 1539 1289 CCR-04SA 1450 2005 2374 1006 CCR-05D 192 1386 1430 729 CCR-05S 1190 1631 1980 646 CCR-06D 133 896 910 724 CCR-06S 3150 3100 3100 3100 CCR-07D 233 297 307 163 CCR-07S 565 550 550 550 CCR-08D 219 252 258 105 CCR-08S 403 550 550 550 CCR-09D 294 322 337 123 CCR-09S 309 415 421 274 CCR-11DA 196 238 248 184 CCR-11S 246 238 244 162 CCR-14D 190 180 209 120 CCR-14S 112 200 200 199 CCR-16BR 166 273 303 203 CCR-16D 191 292 306 251 CCR-16S 259 225 225 223 CCR-17D 317 236 265 134 CCR-17S 222 182 183 178 CCR-18D 290 576 647 369 CCR-18S 138 140 141 136 CCR-20D 294 623 657 406 CCR-20S 141 255 257 240 CCR-21 D 344 145 245 19 CCR-21S 169 346 376 168 CCR-22DA 193 9 18 0 CCR-22S 100 21 23 9 CCR-23D 149 15 19 3 CCR-23S 66 22 22 20 CCR-26BR 381 349 371 200 CCR-26D 217 359 412 77 CCR-26S 84 345 440 32 CCR-BG-01DA 129 0 0 0 CCR-13G-01S 0 0 0 0 CP-01D 1110 1308 1370 751 CP-01S 545 1369 1465 615 CP-02D 3400 2288 2573 986 Page 42 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7c TRANSPORT MODEL SENSITIVITY TO THE TDS Kd VALUES Well TDS (mg/L) TDS Model Calibrated Model, Low Ka Model, High Ka NRMSE 7.0% 7.8% 7.6% CP-02S 2840 3113 3262 2305 CP-03D 908 1897 2363 265 CP-03S 1460 1454 1878 185 CP-04D 338 1157 1298 330 CP-04S 133 178 209 23 CP-05D 506 1047 1108 701 CP-05S 116 592 622 397 CP-06BR 129 0 2 0 CP-06D 263 327 342 158 CP-06S 320 249 261 129 GWA-01 BR 170 30 60 0 GWA-01D 185 44 77 1 GWA-01S 74 20 28 1 GWA-02D 91 85 173 5 GWA-02S 42 8 19 0 GWA-03BRA 139 63 90 30 GWA-03BRL 126 0 0 0 GWA-03D 139 159 170 129 GWA-03S 141 196 197 195 GWA-04BR 206 5 12 0 GWA-04BRL 232 0 0 0 GWA-04D 212 211 228 99 GWA-04S 278 312 316 252 GWA-05BRA 214 205 210 123 GWA-05BRL 211 0 0 0 GWA-05D 180 245 246 166 GWA-05S 286 264 264 192 GWA-06BRA 378 729 733 658 GWA-06BRL 272 9 36 0 GWA-06DA 838 1475 1523 1202 GWA-06S 2130 2200 2200 2200 GWA-07D 310 216 225 175 GWA-07S 164 189 245 26 GWA-08D 122 1 1 0 GWA-08S 204 0 0 0 GWA-09BR 143 4 6 0 GWA-09D 102 7 9 2 GWA-09S 98 5 5 4 GWA-14DA 145 0 0 0 GWA-14S 0 0 0 0 GWA-15D 171 2 2 1 GWA-15S 114 24 24 21 GWA-16D 92 0 0 0 GWA-16S 95 0 0 0 GWA-17D 114 1 1 0 Page 43 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 5-7c TRANSPORT MODEL SENSITIVITY TO THE TDS Kd VALUES Well TDS (mg/L) TDS Model Calibrated Model, Low Kd Model, High Kd NRMSE 7.0% 7.8% 7.6% GWA-17S 79 0 0 0 GWA-18D 113 4 4 1 GWA-18S 106 4 4 1 GWA-19D 159 0 0 0 GWA-19S 52 0 0 0 GWA-21BR 185 0 0 0 GWA-21DA 150 0 0 0 GWA-21S 30 0 0 0 GWA-22D 176 0 0 0 GWA-22S 0 0 0 0 GWA-23D 134 0 0 0 GWA-23S 26 0 0 0 GWA-24BR 163 2 5 0 GWA-24D 162 5 6 0 GWA-24SA 35 1 1 0 GWA-26D 132 0 0 0 GWA-26S 1 73 1 0 1 0 1 0 Prepared by: JFE Checked by: KWW Notes• TDS concentrations are shown for the calibrated model, and for models where the Kd is increased by a factor of 5 and decreased by a factor of 1/5. Page 44 DRAFT - Updated Groundwater Flow And Transport Modeling Report December 2019 Allen Steam Station, Belmont, North Carolina TABLE 6-1 WATER BALANCE ON THE GROUNDWATER FLOW SYSTEM FOR DECANTED CONDITIONS Water Balance Components Flow In (gpm) Flow Out (gpm) Direct recharge to the Active Ash Basin 71 Direct recharge to the Retired Ash Basin 41 Direct recharge to watershed outside of ash basin 60 Ash basin ponds Flow to drainages inside of the ash basins 14 Flow to drainages outside of the ash basin 15 Wells and septic return outside of the ash basin 12 13 Flow toward southeast of AAB 5 Flow towards drainage canal north of the RAB 3 Flow towards the coal pile 19 Flow through and under the dam 110 Notes: gpm =.gallons per minute Prepared by: JFE Checked by: KWW Page 45