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HomeMy WebLinkAboutNC0024406_BCSS_Appendix G_20191231Corrective Action Plan Update December 2019 Belews Creek Steam Station APPENDIX G SynTerra UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT FOR BELEWS CREEK STEAM STATION, BELEWS CREEK, NORTH CAROLINA DECEMBER 2019 PREPARED FOR DUDE ENERGY. CAROLINAS DUKE ENERGY CAROLINAS, LLC INVESTIGATORS RONALD W. FALTA, PH. D. - FALTA ENVIRONMENTAL LLC REGINA GRAZIANO, M.S. - SYNTERRA CORPORATION YOEL GEBRAI, M.S. - SYNTERRA CORPORATION LAWRENCE C. MURDOCH, PH.D. - FRx, INC. RONG YU, PH. D. - SYNTERRA CORPORATION Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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 Belews Creek Steam Station (BCSS, Site, Station). Duke Energy Carolinas, LLC (Duke Energy) owns and operates the BCSS located in Belews Creek, Stokes County, North Carolina. Model simulations were developed using flow and transport models MODFLOW and MT3DMS. Due to historical ash management at the Site, a numerical model was developed to evaluate transport of inorganic constituents of interest (COIs) in the groundwater downgradient of the ash basin. 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 basin. 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). 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). BCSS is a two -unit coal-fired electricity generating plant with a combined capacity of 2,240 megawatts (MW). The station began commercial operations in 1974 with Unit 1 (1,120 MW) followed by Unit 2 (1,120 MW) in 1975. Cooling water for BCSS is provided by Belews Reservoir, which was built for this purpose. Wastewater and coal combustion residuals (CCR) have been managed in the Site's ash basin, on -Site landfills, and a structural fill. Inorganic compounds in the wastewater and ash have dissolved and have migrated in groundwater downgradient of the ash basin. 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 basin. The predictive simulations presented herein are not intended to represent a final detailed closure design. These simulations use conceptual designs that are subject to change as the closure plans are finalized. 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. It should be noted that, for groundwater modeling purposes, a reasonable assumption was made about initiation dates for each of the closure options. The assumed dates were based on information that is currently evolving and might vary from dates provided in contemporary documents. The potential variance in closure dates presented in the groundwater model is inconsequential to the results of the model. This modeling report Page ES-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina is intended to provide basic model development information and simulations of conceptual basin closure designs. The groundwater is in compliance with North Carolina Administrative Code, Title 15A, Subchapter 02L, Groundwater Classification and Standards (02L), and therefore, groundwater corrective action simulations are not required. The model simulations were developed using flow and transport models MODFLOW and MT3DMS. Boron was the constituent of interest (COI) selected to estimate the time to achieve compliance because it is mobile in groundwater and tends to have the largest extent of migration. Chloride and total dissolved solids (TDS) were also modeled because they are conservative COIs that are also migrating out of the ash basin. The less mobile, more geochemically controlled constituents (i.e. arsenic, selenium, chromium,) will follow the same flow path as boron, but to a lesser extent. The less mobile, geochemically controlled constituents do not have discernable plumes and are modeled separately using a geochemical model. This report describes refinements that have improved the accuracy and resolution of details in the model of the Belews Creek site since previous versions (HDR, 2016; SynTerra 2018). The model includes recent revisions to the designs of the closure scenarios developed by AECOM. The model includes data from new deep wells located along the dam. The grid has been refined in some areas to improve the model calibration results. A comprehensive dataset (through second quarter of 2019) of hydraulic heads and boron concentrations was used to recalibrate the model. Results of the simulations indicate that boron concentrations in groundwater greater than the 02L standard are present north and west of the ash basin. Dropping the hydraulic head in the ash basin in year 2020 by decanting and subsequent closure will result in the creation of a strong groundwater divide along Middleton Loop Road to the west of the ash basin dam that will greatly reduce the hydraulic driving force for COI migration. The simulations include an evaluation of two closure scenarios, one that involves closure -by -excavation and another that involves a hybrid closure -in -place design. Additional predictive simulations of the two closure scenarios with remediation that achieves compliance in less than 30 years post -closure are also considered. The remediation design modeled in these scenarios utilizes both extraction and recharge to achieve compliance. Preliminary modeling results suggest that extraction alone will not achieve compliance in a reasonable timeframe due to reduced flow rates after decanting and the limited effect that extraction systems have on COIs present in the unsaturated Page ES-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina zone. The maximum boron concentration in any non -ash layer results for 14 and 164 years post -closure for the closure -by -excavation scenario and 18 and 168 years post - closure for the hybrid closure -in -place scenario are displayed in Figure ES-1. The time series of the maximum boron concentration in any non -ash layer at three representative locations downgradient of the ash basin is shown in Figure ES-2. The results for 18 and 14 years post -closure for the closure scenario simulations predict results decades after decanting, whereas the results for 168 and 164 years post -closure show a long-term prediction. Results of the simulations show the extent of where the boron concentration in groundwater is greater than the 02L standard. For both closure scenarios, the boron plume is present beyond the ash basin compliance boundary 18 years post -closure for the hybrid scenario and 14 years post -closure for the closure -by -excavation scenario and similarly for 168 years post -closure for the hybrid scenario and 164 years post -closure for the closure -by -excavation scenario (Figure ES-1). The maximum boron concentration comparisons indicate the closure scenarios are equally effective in reducing plume migration for the excavation and hybrid design (Figure ES-1 and ES-2). The time needed to achieve compliance with the 02L standard at the compliance boundary is over 200 years for both the closure -by -excavation and hybrid closure -in - place designs with no corrective action other than source control and natural attenuation. Three reference locations near Middleton Loop Road (Point 1), downgradient of the dam (Point 2) and near the Dan River (Point 3) were also used to evaluate changes in boron concentrations over time for the two closure designs (Figure ES-2). The boron concentrations decrease over the next 200 years with compliance unattained at Point 1 by 164 years post -closure for the closure -by -excavation scenario and 168 years post - closure for the hybrid scenario. There is no apparent difference noted between the two closure options at Point 1. At Point 2, the boron concentrations decrease to less than the 02L standard relatively quickly by around 14 years for the closure -by -excavation scenario and 18 year post -closure for the hybrid scenario with no significant difference in the two closure options. The reference location at Point 3 shows an increase in boron concentration until approximately 68 years post -closure for the hybrid scenario and 64 years post -closure for the closure -by -excavation scenario. Compliance is achieved by about 93 years post -closure for the hybrid scenario and 89 years post -closure for the closure -by -excavation scenario with no significant difference between the two closure scenarios. The simulation assumptions and the predicted distributions of boron concentrations over time are described in the report. Page ES-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina The effect of active groundwater remediation to each of the closure scenarios is presented in Figure ES-3. The considered remediation design consists of 113 extraction wells pumping at a total extraction rate of 92 gallons per minute (gpm), 47 clean water infiltration wells injecting water at a combined rate of 54 gpm, and a 900-foot horizontal well that introduces 110 gpm of clean water to the aquifer. The results show a significant reduction in the time to reach compliance for both scenarios. There is only a slight difference between the performance of the system on the closure -by -excavation and hybrid -closure -in -place designs. Data from recent ash pore water and saprolite pumping tests and new deep bedrock wells near the ash basin dam were included in this revision of the model. The numerical and analytical pumping tests analyses indicate that the average hydraulic conductivity of the ash ranges from 0.94 feet per day (ft/d) to 2.9 ft/d in the vicinity of the pumping test wells. It was assumed that this general distribution is representative of the hydraulic conductivity of the ash and an averaged value of 2.5 ft/d was used throughout the basin. Three bedrock wells were drilled along the dam during 2019. Each well was drilled to boring depths of approximately 300 feet. Boron was present in these deep wells, but the concentrations were less than the 02L standard of 700 µg/L. The model is calibrated to reflect the boron concentrations observed in these deep wells. The model simulations indicate that there are no exposure pathways associated with the groundwater flow through the ash basin and the water supply wells in the vicinity of the Belews Creek site. Water supply wells are outside, or upgradient of the groundwater flow system that contains the ash basin. Groundwater migration of constituents from the ash basin do not affect water supply wells under pre -decanting conditions, pre -closure conditions, nor in the future under the different closure options simulated. Page ES-4 HYBRID SCENARIO 18 YEARS POST -CLOSURE w - - '. ,. -.-.r .. _. ._....�-�.. , n POINT 2 POINT 1 +r. - is aid' HYBRID SCENARIO 168 YEARS POST -CLOSURE POINT 2 POINT 1 A LEGEND REFERENCE POINTS BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L — - — - ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). CLOSURE BY EXCAVATION SCENARIO 14 YEARS POST -CLOSURE POINT 2 POINT 1 �1f _- ;.. . CLOSURE BY EXCAVATION SCENARIO 164 YEARS POST -CLOSURE Aj POINT 1 i _. F . 3T,; (' DGRAPHIC SCALE DUKE 1,300 O1, 300 2,600 ENERGY CAR,. (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 141P REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com FIGURE ES-1 COMPARISON OF SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 9000 8000 7000 e 6000 0 W 5000 m c u 4000 e 0 `0 3000 m 2000 1000 0 Point 1, Maximum boron concentration in all layers Hybrid --4-- Closure by Excavation — — 2L std = 700 ug/L -------- r-------r--I 2025 900 800 700 c 600 0 500 u 400 c 0 `0 300 m 200 100 0 2025 2125 2225 Year Point 3, Maximum boron concentration in all layers 2125 Year Hybrid Closure by Excavation — 2 L std = 700 ug/L 2500 2000 c 0 1500 c m 0 1000 0 `o m 500 01-- 2025 Point 2, Maximum boron concentration in all layers f Hybrid Closure by Excavation ——2Lstd=700ug/L 2125 2225 Year Location 1 is near Middleton Loop Road. Location 2 is downgradient of the dam. Location 3 is near the Dan River. DUKE DRAWN BY: Y. GEBRAI DATE: 10/10/2019 FIGURE ES-2 ENERGY REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 SUMMARY OF MAXIMUM BORON CONCENTRATION IN ALL LAYERS AS CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 FUNCTIONS OF TIME FOR THE TWO CLOSURE SCENARIOS APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT AT REFERENCE LOCATIONS ,010 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT synTerra BELEWS CREEK STEAM STATION www.synterracorp.com BELEWS CREEK, NORTH CAROLINA HYBRID SCENARIO 18 YEARS POST -CLOSURE HYBRID SCENARIO 168 YEARS POST -CLOSURE 1 w R LEGEND 0 EXTRACTION WELLS ♦ CLEAN WATER INFILTRATION WELLS HORIZONTAL CLEAN WATER INFILTRATION WELL BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION WELLS, 113 ADDITIONAL GROUNDWATER EXTRACTION WELLS, 47 CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER INFILTRATION WELLARE IN OPERATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). CLOSURE BY EXCAVATION SCENARIO 14 YEARS POST -CLOSURE i 17 (' DUKE 290 GRAPHIC SC LE 580 ENERGY CAR,. (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/10/2019 CHECKED BY: A. ALBERT DATE: 12/10/2019 APPROVED BY: C. EADY DATE: 12/10/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com FIGURE ES-3 COMPARISON OF SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS WITH REMEDIATION SCENARIOS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE OF CONTENTS SECTION PAGE ExecutiveSummary........................................................................................................... ES-1-1 1.0 Introduction..................................................................................................................1-1 1.1 General Setting and Background..........................................................................1-1 1.2 Objectives.................................................................................................................1-2 2.0 Conceptual Model........................................................................................................2-1 2.1 Aquifer System Framework.................................................................................. 2-1 2.2 Groundwater Flow System....................................................................................2-1 2.3 Hydrologic Boundaries.......................................................................................... 2-2 2.4 Hydraulic Boundaries............................................................................................ 2-2 2.5 Sources and Sinks....................................................................................................2-2 2.6 Water Budget...........................................................................................................2-2 2.7 Modeled Constituents of Interest......................................................................... 2-3 2.8 Constituent Transport............................................................................................ 2-3 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............................................................................................4-2 4.3 Flow Model Boundary Conditions.......................................................................4-3 4.4 Flow Model Sources and Sinks............................................................................. 4-4 4.5 Flow Model Calibration Targets........................................................................... 4-6 4.6 Transport Model Parameters.................................................................................4-6 4.7 Transport Model Boundary Conditions.............................................................. 4-8 4.8 Transport Model Sources and Sinks.....................................................................4-8 4.9 Transport Model Calibration Targets.................................................................. 4-9 5.0 Model Calibration To Pre -decanted Conditions....................................................5-1 5.1 Flow Model Calibration......................................................................................... 5-1 5.2 Flow Model Sensitivity Analysis.......................................................................... 5-4 5.3 Historical Transport Model Calibration.............................................................. 5-4 5.4 Transport Model Sensitivity Analysis................................................................. 5-6 Page i Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina 6.0 Predictive Simulations Of Closure Scenarios........................................................ 6-1 6.1 Interim Models with Ash Basin Decanted (2020-2032 or 2020-2036) .............. 6-2 6.2 Hybrid Closure -in -Place with Monitored Natural Attenuation ...................... 6-3 6.3 Hybrid Closure -in -Place with Active Remediation........................................... 6-4 6.4 Closure -by -Excavation with Monitored Natural Attenuation ......................... 6-6 6.5 Closure -by -Excavation with Active Remediation.............................................. 6-7 6.6 Conclusions Drawn from the Predictive Simulations ....................................... 6-7 7.0 References......................................................................................................................7-1 Page ii Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina LIST OF FIGURES Figure ES-1 Comparison of simulated maximum boron concentrations in all non -ash layers for both closure scenarios Figure ES-2 Summary of maximum boron concentrations in all model layers as a function of time for the two closure scenarios at reference locations Figure ES-3 Comparison of simulated boron concentrations in all non -ash layers with remediation scenarios Figure 1-1 USGS location map of the Belews Creek Steam Station Figure 4-1 Numerical model domain Figure 4-2 Fence diagram of the 3D hydrostratigraphic model Figure 4-3 Computational grid used in the model Figure 4-4 Hydraulic conductivity estimated from slug tests performed in ash at 14 sites in North Carolina Figure 4-5 Hydraulic conductivity estimated using slug tests performed in saprolite at 10 Piedmont sites in North Carolina Figure 4-6 Hydraulic conductivity estimated using slug tests performed in the transition zone at 10 Piedmont sites in North Carolina Figure 4-7 Hydraulic conductivity estimated using slug tests performed in fractured rock at 10 Piedmont sites in North Carolina Figure 4-8 Distribution of recharge zones Figure 4-9 Model surface water features outside the ash basin Figure 4-10 Model surface water features inside the ash basin Figure 4-11 Location of water supply wells in the model area Figure 5-1 Model hydraulic conductivity zones in ash layer 3 Figure 5-2 Cross-section through ash basin dam showing hydraulic conductivity (colors) and hydraulic heads (lines) Figure 5-3 Model hydraulic conductivity zones in saprolite, layers 10-12 Figure 5-4 Model hydraulic conductivity zones in saprolite layers 13-14 Figure 5-5 Model hydraulic conductivity zones in transition zone layer 15 Figure 5-6 Model hydraulic conductivity zones in transition zone layer 16 Figure 5-7 Model hydraulic conductivity zones in upper fractured bedrock layers 17-18 Figure 5-8 Model hydraulic conductivity zones in upper fractured bedrock layers 19-21 Figure 5-9 Model hydraulic conductivity zones in upper fractured bedrock layers 22-24 Figure 5-10 Model hydraulic conductivity zones in deep bedrock layers 25-30 Page iii Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina Figure 5-11 Comparison of observed and computed heads from the calibrated steady state flow model Figure 5-12 Simulated heads in the transition zone layer 15 Figure 5-13 Simulated heads in the second fractured bedrock layer 17 Figure 5-14 Simulated drains and layer 15 transition zone hydraulic heads Figure 5-15 Groundwater divide and flow directions Figure 5-16 COI source zones for the historical transport model Figure 5-17 Simulated pre -decanting boron concentrations in all non -ash layers Figure 5-18 Simulated pre -decanting chloride concentrations in all non -ash layers Figure 5-19 Simulated pre -decanting TDS concentrations in all non -ash layers Figure 6-1 Existing groundwater extraction wells near Middleton Loop Road Figure 6-2 Simulated hydraulic heads in the transition zone after ash basin decanting Figure 6-3 Simulated boron concentrations in all non -ash layers after decanting Figure 6-4 Hybrid closure design used in simulations Figure 6-5 Drains used in the hybrid design simulation Figure 6-6 Simulated hydraulic heads for the hybrid scenario Figure 6-7a Simulated boron concentrations in all non -ash layers 18 years post - closure for the hybrid scenario Figure 6-7b Simulated boron concentrations in all non -ash layers 68 years post - closure for the hybrid scenario Figure 6-7c Simulated boron concentrations in all non -ash layers 118 years post -closure for the hybrid scenario Figure 6-7d Simulated boron concentrations in all non -ash layers 168 years post -closure for the hybrid scenario Figure 6-8 Simulated hydraulic heads in the transition zone layer 15 for the hybrid closure option with active groundwater remediation Figure 6-9a Simulated boron concentrations in all non -ash layers after 27 years of active groundwater remediation for the hybrid scenario with active remediation Figure 6-9b Simulated boron concentrations in all non -ash layers after 77 years of active groundwater remediation for the hybrid scenario with active remediation Figure 6-9c Simulated boron concentrations in all non -ash layers after 127 years of active groundwater remediation for the hybrid scenario with active remediation Page iv Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina Figure 6-9d Simulated boron concentrations in all non -ash layers after 177 years of active groundwater remediation for the hybrid scenario with active remediation Figure 6-10a Simulated chloride concentrations in all non -ash layers after 27 of active groundwater remediation for the hybrid scenario with active remediation Figure 6-10b Simulated TDS concentrations in all non -ash layers after 27of active groundwater remediation for the hybrid scenario with active remediation Figure 6-11 Closure by excavation design used in simulations (from AECOM, 2019) Figure 6-12 Drain network used in the closure -by -excavation simulations Figure 6-13 Simulated hydraulic heads for the closure -by -excavation scenario Figure 6-14a Simulated boron concentrations in all non -ash layers 14 years post - closure for the closure -by -excavation scenario Figure 6-14b Simulated boron concentrations in all non -ash layers 64 years post - closure for the closure -by -excavation scenario Figure 6-14c Simulated boron concentrations in all non -ash layers 114 years post -closure for the closure -by -excavation scenario Figure 6-14d Simulated boron concentrations in all non -ash layers 164 years post -closure for the closure -by -excavation scenario Figure 6-15 Simulated hydraulic heads in the transition zone layer 15 for the closure -by -excavation scenario with active groundwater remediation Figure 6-16a Simulated boron concentrations in all non -ash layers after 27 years of active groundwater remediation for the closure -by -excavation scenario with active remediation Figure 6-16b Simulated boron concentrations in all non -ash layers after 77 years of active groundwater remediation for the closure -by -excavation scenario with active remediation Figure 6-16c Simulated boron concentrations in all non -ash layers after 127 years of active groundwater remediation for the closure -by -excavation scenario with active remediation Figure 6-16d Simulated boron concentrations in all non -ash layers after 177 years of active groundwater remediation for the closure -by -excavation scenario with active remediation Page v Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina Figure 6-17a Simulated chloride concentrations in all non -ash layers after 27 years of active groundwater remediation for the closure -by - excavation scenario with active remediation Figure 6-17b Simulated TDS concentrations in all non -ash layers after 27 years of active groundwater remediation for the closure -by -excavation scenario with active remediation Page vi Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina LIST OF TABLES Table 5-1 Comparison of observed and computed 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 5-5a Ash basin boron source concentrations used in historical transport model Table 5-5b Ash basin chloride source concentrations used in historical transport model Table 5-5c Ash basin TDS source concentrations used in historical transport model Table 5-6a Observed and computed boron in monitoring wells Table 5-6b Observed and computed chloride in monitoring wells Table 5-6c Observed and computed TDS in monitoring wells Table 5-7 Transport model sensitivity to the boron Ka values Table 6-1 Water balance on the groundwater flow system for post -decanting conditions Table 6-2 Groundwater clean water infiltration and extraction well depths Page vii Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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 Belews Creek Steam Station (BCSS, Site, Station). Duke Energy Carolinas, LLC (Duke Energy) owns and operates the BCSS located in Belews Creek, Stokes County, North Carolina (Figure 1-1). The Site is located on 6100 acres and includes the Belews Reservoir (3800 acres) that is used for cooling. The Dan River is located north of the Site. 1.1 General Setting and Background The BCSS became operational in 1974. It currently operates two coal-fired units with a 2,240 Megawatts (MW) generating capacity. A 283-acre ash basin is located northwest of the plant. Coal combustion residuals (CCR) were historically sluiced to this basin. In 1984, BCSS converted to a dry fly ash handling system, but the ability to sluice to the ash basin was maintained, though limited to certain situations. Discharge from the ash basin to the Dan River is permitted by the North Carolina Department of Environmental Quality (NCDEQ) under a National Pollutant Discharge Elimination System (NPDES) permit. The Pine Hall Road (PHR) Landfill, located near the southern edge of the ash basin, began operation in late 1984 after BCSS converted to dry handling of fly ash. In 2008, an engineered cover system was installed over a 37.9-acre area of the unlined landfill to close a part of the landfill. The total area of the PHR Landfill is 52 acres, and this landfill is located in the watershed that drains to the ash basin. Between 2004 and 2009, an unlined structural fill that consists of compacted fly ash was constructed immediately south of Pine Hall Road. An engineered cover system was installed over the structural fill in 2012. The structural fill is located south of a divide that separates the watershed that includes the ash basin from the Belews Reservoir watershed. The Site is located in the Piedmont region of North Carolina. The topography in the area is hilly with elevations ranging from approximately 578 feet at the Dan River, north of the Station to approximately 878 feet near the intersection of Pine Hall Road and Middleton Loop Road. Belews Reservoir, which serves as the cooling lake for the Station, has a pool elevation of approximately 725 feet. The ash basin water was typically maintained at level of 750 feet. The elevation of the ash basin relative to the surrounding topography and the Dan River results in groundwater flow toward the river from the northern part of the basin. A groundwater divide exists south and east of Page 1-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina the ash basin, and approximately follows Pine Hall Road. This divide appears to hydraulically separate the ash basin from Belews Reservoir. The subsurface at the Site is composed of saprolite, a transition zone, and bedrock. The upper part of the bedrock is generally fractured and the majority of water bearing fractures are encountered in the upper 50 feet of bedrock. The groundwater flow is unconfined and the water table surface might occur in the saprolite, the transition zone, or in the fractured bedrock. The groundwater flow and constituent transport model for the Site was initially developed in 2015 (HDR, 2015b). The present model domain has been greatly expanded compared to the 2015 model, and the number of model layers has been tripled. The earlier model was calibrated to hydraulic heads and COI concentrations measured in 2015. Since that time, significant Site activities have taken place including the installation of many additional monitoring wells. The current model has been completely revised with respect to the 2015 model. 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. The updated model presented herein has been refined based on observations from data collected since April 2018. The grid has been refined in the transition zone and the bedrock. The 2019 flow model calibration used historically averaged hydraulic heads based on water elevation data collected from monitoring wells until the second quarter of 2019. New hydraulic head and boron concentration data collected from deep bedrock wells near the ash basin dam were incorporated for calibration. The hydraulic conductivity setup was revised to reflect the results of groundwater pumping tests conducted in the ash basin in September 2018. The 2019 boron calibration used boron concentration data measured for samples obtained from the 4th quarter of 2018 to the second quarter of 2019 (SynTerra, 2019c). 1.2 Objectives The overall objectives of the groundwater flow and transport modeling are to predict the performance of the two closure scenarios, and to guide decisions during the selection of closure actions. The flow and transport models have been undergoing a process of continuous improvement and refinement by including new field data. The continuous improvement process is designed to increase the accuracy and reliability of the performance predictions. The objective of this report is to describe the results of the most recent refinement of the flow and transport models. These models were developed in early and mid-2019 using Page 1-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina data through the second quarter of 2019. Furthermore, a goal is to present results of simulations of boron transport in all flow zones. The predictive simulations shown in this report are not intended to represent a final detailed closure design. These simulations use conceptual designs that are subject to change as the closure plans are finalized. 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 1-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina 2.0 CONCEPTUAL MODEL The conceptual site model of the Belews Creek site is based primarily on the 2015 Comprehensive Site Assessment (CSA) report (HDR, 2015a) and the 2017 CSA Update (SynTerra, 2017). The 2017 CSA report contains extensive detail and data related to most aspects of the conceptual site model. 2.1 Aquifer System Framework The aquifer system at the Site is unconfined. Depending on the local topography and hydrogeology, the water table surface might exist in the saprolite, the transition zone, or in the fractured bedrock. At some isolated locations along streambeds, the upper units (saprolite and transition zone) are absent. At other locations, the upper units might be unsaturated, with the water table located in deeper units. The hydraulic conductivity at the Site was measured in a series of slug tests in the different units. Fifteen slug tests were performed in the coal ash, with conductivities ranging from 0.08 ft/d to 35 ft/d. Twenty-seven slug tests performed in saprolite wells yielded hydraulic conductivities ranging from 0.01 ft/d to 11 ft/d. Sixty-four slug tests performed in deeper transition zone wells were analyzed and hydraulic conductivity estimates ranging from 0.001 ft/d to 32 ft/d obtained. Forty-four slug tests conducted in bedrock wells gave hydraulic conductivity values ranging from 0.0003 ft/d to 73 ft/d. Most of the bedrock wells are screened near the top of the bedrock surface; the conductivity of the deeper bedrock is expected to be less. The range of observed conductivity in the saprolite, transition zone, and bedrock wells (from nearly 0 ft/d to 73 ft/d) highlights the large degree of heterogeneity in the system. 2.2 Groundwater Flow System The unconfined groundwater system at the Site is currently dominated by flow from the ponded water in the ash basin, which until recently was maintained at an elevation of 750 feet (elevations in this report are based on the NAVD88 datum). The ponded water in the ash basin is currently being decanted, with an expected completion date of October 2020. The ash basin was formed by damming a valley that runs toward the Dan River. Groundwater flow from the ash basin is generally toward the north and northwest, towards the Dan River with an elevation of approximately 578 ft. A groundwater divide exists south and east of the ash basin, approximately along Pine Hall Road. To the south and east of this divide, groundwater flows toward Belews Reservoir at an elevation of 725 feet. A second groundwater divide approximately follows Middleton Loop Road north from the intersection with Pine Hall Road. This Page 2-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina groundwater divide is not present under pre -decanting conditions in the Middleton Loop Road area near the ash basin dam. Inside the groundwater divides, groundwater flows toward the ash basin. The groundwater system is recharged from infiltrating rainwater, and from water that infiltrates from the ash basin. The average value of recharge in the vicinity of the Site was estimated at 8 inches per year (in/yr). The North Carolina map of recharge by Haven (2003) does not show values for Stokes County, but the average value in adjacent counties is consistent with this estimate. A reduced rate of recharge (1 in/yr) was assumed for the power plant, and an infiltration rate of 0 in/yr was assumed for constructed wetland areas. The constructed wetland area was recently converted to a lined retention basin. The capped areas of the PHR Landfill and structural fill were assigned very low infiltration rates of 0.00054 in/yr based on results from landfill cover simulations. There is one public supply well and 50 private water wells that have been identified within one-half mile of the ash basin compliance boundary (SynTerra, 2017). Most of these wells are located northeast of the ash basin along Pine Hall Road and Middleton Loop, and west and southwest of the ash basin along Middleton Loop, Old Plantation Road, Pine Hall Road, and Martin Luther King Jr. Road. Pumping rates of the private wells were not available; completion depths were only available for a few wells. 2.3 Hydrologic Boundaries Belews Reservoir and the Dan River serve as major hydrologic boundaries in the area. 2.4 Hydraulic Boundaries The groundwater system does not appear to contain impermeable barriers or hydraulic boundaries in the study area. 2.5 Sources and Sinks Groundwater flows out of the ash basin pond and areal recharge are sources of water to the groundwater system. Groundwater discharges to the Dan River, Belews Reservoir, and to numerous small streams. The water supply wells within the model area remove only a small amount of water from the overall hydrologic system. 2.6 Water Budget The long-term average rate of water inflow to the study area is equal to the rate of water outflow from the study area. Water enters the groundwater system from the ash basin pond and through recharge. Water leaves the system through discharge to the Dan River, Belews Reservoir, several small creeks, and through supply wells. Page 2-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina 2.7 Modeled Constituents of Interest Antimony, arsenic, barium, beryllium, boron, cadmium, chloride, chromium (hexavalent and total), cobalt, iron, manganese, molybdenum, selenium, strontium, sulfate, TDS, thallium, and vanadium have been identified as constituents of interest (COIs) for groundwater at the Site (SynTerra, 2017). Three conservative COIs that are present beyond the compliance boundary were selected for modeling. The COIs selected consist of boron, chloride, and TDS. Of those three constituents, boron is the most prevalent in groundwater. Boron is present at relatively greater concentrations in the ash basin, near and beneath the PHR Landfill, and near the structural fill. A boron plume extends to wells north and west of the ash basin. Boron is found in wells screened in the saprolite, the transition zone, and the bedrock. Boron concentrations in background wells are considerably less than the North Carolina Administrative Code, Title 15A, Subchapter 02L, Groundwater Classification and Standard (02L), and are generally less than the detection limit. Because boron is the dominant mobile constituent, this report will focus primarily on boron. TDS and chloride are not as prevalent as boron, but they are both similarly present in relatively greater concentrations in the ash basin. TDS also is present in greater concentrations near and beneath the PHR Landfill and near the structural fill. 2.8 Constituent Transport The COIs that are present in the coal ash dissolve into the ash pore water. As water infiltrates through the ash, water containing COIs can enter the groundwater system. Once in the groundwater system, the COIs are transported by advection and dispersion, subject to retardation due to adsorption to solids. If the COIs reach a hydrologic boundary or water sink, they are removed from the groundwater system, and they enter the surface water system, where in general, they are greatly diluted. At this Site, boron, chloride, and TDS are the primary constituents that are migrating from the ash basin. The less mobile, more geochemically controlled constituents (i.e., arsenic, selenium, chromium) will follow the same flow path as boron, but to a lesser extent. The less mobile, geochemically controlled constituents do not have discernable plumes and are modeled separately using a geochemical model. Page 2-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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 (31)) 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 10.4 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 31) 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 activities. Some of the Site's flow models were challenging to run due to the topography and layers that become unsaturated in the model. It was found that using the NWT solver options "MODERATE" with the xMD matrix solver could overcome these difficulties. 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 on the soil and rock matrix. Page 3-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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 construct 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, chloride, 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 the model domain and the construction of a 3D hydrostratigraphic model. The model has dimensions of approximately 13,000 feet by 13,000 feet, and it is oriented in a north - south orientation (Figure 4-1). The model is bounded generally to the north by the Dan River and Town Fork Creek. It is bounded by Belews Reservoir to the south and east. The model boundary is located several deep creek drainages away from the ash basin to the west, and the northeast. The distance to the boundary from the ash basin is large enough to prevent boundary conditions from artificially affecting the results near the basin. The ground surface of the model was developed by HDR and was interpolated from the North Carolina Floodplain Mapping Program's 2010 LiDAR elevation data. These data were supplemented by on -Site surveys conducted by Duke Energy in 2014. The elevations used for the top of the ash surface in the ash basin were modified from the bathymetric data to provide a model surface that can accommodate planned regrading of ash under different closure options. For pre -decanting conditions simulations, this part of the ash in the model is given a large hydraulic conductivity to represent the open water conditions in the basin. The hydrostratigraphic model (called a solids model in GMS) consists of five units: ash, saprolite, transition zone, upper fractured bedrock, and deeper bedrock. The elevation of contacts between the units (ash, saprolite, transition zone, and bedrock) were determined from boring logs from previous studies by HDR (2015a, 2016). The contact Page 4-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina elevations were estimated by HDR for locations where well logs were not available by extrapolation of the borehole data using the Leapfrog Hydro geologic modeling tool. This program was used by HDR to develop surfaces defining the top of the saprolite, transition zone, and bedrock. While the contact 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 was subjective. For the purposes of model construction, the upper fractured zone is assumed to be 216 feet thick. The deeper bedrock extends another 494 feet below the upper zone for a total bedrock thickness of 710 feet in the model. The upper bedrock zone in the model was given a heterogeneous hydraulic conductivity distribution to represent more and less fractured zones. Figure 4-2 shows a fence diagram of the 3D hydrostratigraphic unit viewed from the northwest, with a vertical exaggeration of 2x. The light grey material corresponds to the ash basin, the yellow material is the saprolite, the light tan material is the transition zone, the orange material is the upper fractured part of the bedrock, and the dark grey material is the deep bedrock. The numerical model grid is shown in Figure 4-3. The grid is discretized in the vertical direction using the solids model (Figure 4-2) to define the numerical model layers. The top 9 model layers represent the ash basin, including the dams that form the basin, the PHR Landfill, and the structural fill. Model layers 10-14 represent the saprolite. Model layers 15 and 16 represent the transition zone. Layers 17-24 represent the upper fractured part of the bedrock, while layers 25 to 30 represent deeper parts of the bedrock (which also may be fractured). The model varies in thickness from about 730 feet to 810 feet. The discretization in the horizontal direction is variable with smaller grid cells in and around the ash basin area. The minimum horizontal grid spacing in the finely divided areas is approximately 20 feet, while the maximum grid spacing near the outer edges of the model is approximately 150 feet. The grid contains a total of 1,130,386 active cells in 30 layers. 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 variation. Most of the hydraulic parameter distributions in the model were heterogeneous across a model layer. The geometries and parameter values of the heterogeneous distributions were determined during the flow model calibration process. Initial estimates of parameters were based on literature Page 4-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina values, results of slug and core tests, and simulations performed using a preliminary flow model. The hydraulic parameter values were adjusted during the flow model calibration process (described in Section 5.0) to provide a best fit to observed water levels in observation wells. Slug test data from hundreds of wells at the Duke Energy coal ash basin sites in North Carolina are shown in Figure 4-4 through Figure 4-7. The hydraulic conductivity of coal ash measured at 14 sites in North Carolina varies by more than 4 orders of magnitude, with a geometric mean value of approximately 1.8 ft/d (Figure 4-4). Ash hydraulic conductivity values measured in slug tests at the Site ranged from 0.07 ft/d to 35 ft/d. The pre -decanted conditions flow model is insensitive to the ash conductivity, but predictive simulations can be sensitive to the ash conductivity. Two pumping tests were performed in the ash basin on -site at BCSS to help refine the value of this parameter. One test was performed in the ash and another in the saprolite. The pumping tests were analyzed both analytically and numerically and are plotted in Figure 4-4 (SynTerra 2019a; SynTerra 2019b). The hydraulic conductivities from hundreds of slug tests performed in saprolite wells at 10 Piedmont sites are shown in Figure 4-5. The range of hydraulic conductivity estimates varies over 4 orders of magnitude with a geometric mean value of 0.9 ft/d. Saprolite slug tests performed at the Site ranged from 0.01 ft/d to 11 ft/d. Transition zone hydraulic conductivities from hundreds of slug tests at 10 Piedmont sites are shown in Figure 4-6. These range over 6 orders of magnitude, with a geometric mean value of 0.9 ft/d. The measured values at the Site range from 0.001 ft/d to 32 ft/d. Results from slug tests in bedrock from hundreds of wells at 10 sites in the Piedmont geologic province (Figure 4-7) range over 6 orders of magnitude, with a geometric mean value of 0.3 ft/d. There are three reasons it is probable that the geometric mean value is more than the true average value for bedrock. First, the bedrock wells are almost all screened in the uppermost bedrock (within tens of feet), which is expected to be more highly fractured than deeper bedrock zones. Second, the wells are normally screened in zones with visible flowing fractures rather than in zones with intact, unfractured rock. Finally, wells that do not produce water are not slug tested. These factors likely bias the slug test data to higher values than are representative of the bedrock as a whole. At the Site, the measured values from slug tests in shallow bedrock ranged from 0.0003 to 73 ft/d. 4.3 Flow Model Boundary Conditions Belews Reservoir forms the hydraulic boundary south and east of the ash basin. The reservoir is treated as a specified head boundary in the uppermost active model layer Page 4-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina with an elevation of 725 feet. The Dan River and Town Fork Creek are located north and northeast of the ash basin, and these are treated as specified head boundaries in the uppermost active model layer. The water elevations here range from a maximum of 590 feet in the western part of Town Fork Creek, to 575 feet in the eastern part of the Dan River. The western model boundary does not align with any clearly defined hydraulic features. This boundary is located approximately one mile from the ash basin. There are several deep creek valleys between the model boundary and the ash basin. Most of the western boundary is treated as a general head boundary with the head set to an elevation of 20 feet below the top of the saprolite, except in stream valleys, where a no - flow boundary is used perpendicular to the streams. The flow in these valleys is dominated by flow towards the streams, which are modeled as drains. The northeastern boundary is treated as a no -flow boundary as it crosses several stream valleys approximately perpendicular to the streams, which are treated as drains in the model. This boundary is also approximately one mile from the ash basin. All deeper model boundaries are treated as no -flow boundaries. 4.4 Flow Model Sources and Sinks The flow model sources and sinks consist of Belews Reservoir, the Dan River, and Town Fork Creek, the ash basin pond, recharge, streams, and wet areas that are assumed to directly drain into the ash basin pond. Recharge is a significant hydrologic parameter in the model, and the distribution of recharge zones in the model is shown in Figure 4-8. As described in Section 2.2, the recharge rate for the BCSS site was estimated at 8 in/yr. The recharge rate for the BCSS plant was set to 1 inch per year due to large areas of roof and pavement. The ash basin ponded area is treated as a specified head boundary and has 0 rainfall recharge, but the part of the basin south of the ponded area has a reduced rate of 4 in/yr except near the ponded area, where the rate was set to 0 in/yr. The water table in this location is close to the ground surface, and heavy rain events may result in runoff to the basin rather than infiltration to the groundwater system. The use of higher recharge rates in the model in this area resulted in unrealistic flooding of the top of the model. The recharge rate in the dam was set to 2 in/yr, and it was set to 0 in/yr in the stream valley downgradient of the dam (the groundwater discharge area). The recharge rate was set to 0 in/yr within the former constructed wetlands areas, which are lined. The recharge rate through the PHR Landfill and structural fill covers were set to 1.23 x 10-7 in/yr based on landfill cover simulations. Page 4-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina Belews Reservoir, the Dan River, Town Fork Creek, and the ponded water in the ash basin were treated as specified head zones in the model (Figure 4-9 and Figure 4-10). Belews Reservoir is maintained at an elevation of 725 feet. The ponded water in the ash basin was maintained at an elevation of 750 feet (pre -decanting conditions). Town Fork Creek and the Dan River range from an elevation of 590 feet (in the upstream part of Town Fork Creek) to an elevation of 575 feet (in the downstream part of Dan River). The many creeks exert significant local control on the hydrology in the model. These features are shown as green lines in Figure 4-9. The position of each creek was primarily determined from the topographic map (Figure 1-1). In addition, three (3) site visits to inspect drainage near the ash basin contributed to determining the position. The elevation of locations along the creeks was determined using surface LiDAR elevation data, and the creeks were assumed to be approximately 2 feet below the ground surface (bgs). The creeks were modeled using the DRAIN feature in MODFLOW with a high conductance value (500 ftz/d/ft). The southern part of the ash basin contains several areas of standing water, along with two main sluicing channels. Inspection of these wet areas suggests that they drain to the main ash basin ponded area during periods of high water. These areas and the sluice channels were treated as drains in the pre -decanting conditions model (Figure 4-10). The ash basin dam contains a blanket drain at an approximate elevation of 648 feet, which is included in the model (Figure 4-9). Figure 4-11 shows the location of public and private water supply wells in the model area. There is one public supply well in the model domain, located in the northeastern part of the model, along Pine Hall Road at the Withers Chapel United Methodist Church. The average flow rate from this well is not known, and was assumed to be 7500 gallons per day in the model. The depth of this well is not known but it was assumed that it is drawing from the lower transition zone model layer (layer 16). There are 64 private wells inside the model boundary, which is more than the 50 wells identified within a 0.5 mile radius of the ash basin compliance boundary (SynTerra, 2017). The model extends approximately one mile beyond the ash basin waste boundary, which accounts for the additional wells. Where depth data were available, the private wells were screened over the known depth. In most cases, the well depths were not known, and the wells were assumed to be screened in the transition zone in model layer 16. The pumping rates were also not known, but it was assumed that the wells were pumped at 280 gals per day, which is an average water use for a family of four (Treece et al., 1990; USGS, 1987, 1995). Septic return was assumed to be 94 percent Page 4-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina of the pumping rate (Treece et al., 1990; Daniels et al., 1997; Radcliffe et al., 2006). The septic return was injected into layer 10 of the model. 4.5 Flow Model Calibration Targets The flow model steady-state calibration targets were determined by averaging water levels and available flow rates. Measurements taken at 168 observation wells through the second quarter of 2019 and the flow rate of water leaking through and immediately underneath the ash basin dam was averaged. The flow was measured at location S-11 in the stream, just downstream from the dam. The flow rate measured at S-11 appears to be variable in time, with an average rate of approximately 180 gpm. Results from all wells sampled were included in the calibration. The wells included those screened in each of the hydrostratigraphic units and many sets of nested wells. 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 started January 1974, and it continued through April 2019. The transient flow field was approximated as a series of flow fields corresponding to conditions at different times during the period that the PHR Landfill and the structural fill were being capped with an engineered cover system. The transient flow field was modeled as four successive steady-state flow fields. One flow field corresponding to the Site conditions before the PHR Landfill and structural fill locations were capped (from 1974 through 2008); one corresponding to conditions after the PHR Landfill was capped, but before the structural fill was capped (from 2008 through 2012); one flow field corresponding to the period after both were capped (from 2012 through 2017); and a final steady-state flow field corresponding to the period after the interim extraction well system was installed (from 2017 through April 2019). Capping of the PHR Landfill and the structural fill was simulated by reducing the recharge rates of those areas from 8 in/yr to 1.23 x 10-7 in/yr. The key transport model parameters (in addition to the flow field) are the boron, chloride, and TDS source concentrations in the ash; and the boron, chloride, and TDS soil -water distribution coefficients (Ka). Other parameters are the longitudinal, transverse, and vertical dispersivities, and effective porosity. The source concentrations in the ash basin, PHR Landfill, and structural fill were initially estimated from the ash pore water concentrations and from concentrations in nearby wells. During the transport model calibration process, the basin and other areas were subdivided, and different concentrations were assigned to different zones at different times. The timing of COI sources appearing in the PHR Landfill and structural fill locations corresponds to the time when they became active (1985 and 2004, respectively). Source concentrations of the COIs were held constant at the specified levels in the ash layers Page 4-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina during the historical transport simulation, but they were allowed to vary in time during the predictive simulations that follow. The numerical treatment of adsorption in the model requires special consideration because part of the system consists of porous media (the ash, saprolite, and transition zone) with relatively high porosity, while the bedrock is 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 simulated the 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 Darcy flux (volume of water per area of rock per time) for a given hydraulic gradient. However, because the water flows almost entirely through the fractures, this approach requires 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 (1a) where the COI retardation factor is computed internally in the MT3DMS code using a conventional approach: R =1 +'°bK a 0 (1b) and V is the volumetric flux (Darcy velocity), pb is the bulk density and Ka 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 Ka is held constant. This is unrealistic, and it is the reason why a small Ka value is assigned to the bedrock, where the effective porosity is due to the fractures, and is low. This reduction of Ka is justified on physical grounds because COIs in fractured rock interact with only a small fraction of the total volume in a grid block, whereas COIs in porous media are assumed to interact with the entire volume. The Ka for COIs 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. Page 4-7 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina Ash leaching tests were performed on five (5) samples from the BCSS ash basin using USEPA Method 1316 (LEAF). The leaching data were analyzed to develop a Ka value for boron in the coal ash. The average of those test values was 0.46 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 Ka value that is derived from ash leaching tests ensures that the model response of the boron in the ash to groundwater flushing is realistic. The Ka values for the boron outside of the ash basin were treated as a calibration parameter. Boron is expected to be mobile, and to have a low Ka value. The calibrated Ka values for the saprolite and transition zone layers were 0.4 mL/g. In the fractured bedrock, a significantly lower value was used as described above of 0.02 mL/g. The Ka values used for chloride in the model were 0.15 mL/g in the ash, 0.1 mL/g in the saprolite and transition zone, and 0.01 mL/g in the bedrock. The Ka values used for TDS in the model were also 0.15 mL/g in the ash, 0.1 mL/g in the saprolite and transition zone, and 0.01 mL/g in the bedrock. 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 0.02 ft. The effective porosity was set to a value of 0.3 in the unconsolidated layers, and to 0.01 in all of the bedrock layers. The soil dry bulk density was set to 1.6 g/mL. 4.7 Transport Model Boundary Conditions The transport model boundary demonstrates no -flow conditions on the exterior edges of the model except where constant head boundaries exist (specified as a concentration of 0 µg/L. All of the constant head water bodies (lakes, river, and pond) have a fixed concentration of 0 µg/L. As water containing dissolved constituents enters these zones, the dissolved mass is removed from the model. The infiltrating rainwater is assumed to be clean and enters from the top of the model. The ash basin pond receives special treatment, where the water level is maintained using a constant head hydraulic boundary, but the boron concentration is specified in model cells below the water surface. The initial condition for the historical transport model assumes a boron concentration of 0 µg/L throughout the Site in 1974. No background concentrations are considered. 4.8 Transport Model Sources and Sinks The ash basin, PHR Landfill, and structural fill are the sources of boron in the model. During the historical transport simulation, these sources are simulated by holding the boron concentration constant in cells located inside the ash in these zones. The boron Page 4-S Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina concentrations from the historical transport simulation form the initial condition for the predictive simulations of future transport at the Site. The predictive simulations do not hold the boron concentrations constant in the ash source zones, and these mobile constituents can wash out of the ash over time. The boron Ka value used for the ash was measured in ash leaching tests using ash from the Site to ensure that the simulated boron leaching rate is realistic. Effected soil and rock at the Site can serve as a secondary source for groundwater COIs like boron, chloride, and TDS at the Site. This is accounted for in the model by continuously tracking the COI concentrations over time in the saprolite, transition zone, and bedrock materials throughout the model. The historical transport model simulates the migration of COIs through the soil and rock from the ash basin, and these results are used as the starting concentrations for the predictive simulations. The transport model sinks are the constant head lakes, river, ponds, creeks, and drains. As groundwater enters these features, it is removed along with any dissolved constituent mass. Similarly, if water containing a constituent were to encounter a pumping well, the constituent is removed with the water. 4.9 Transport Model Calibration Targets The transport model calibration targets are boron concentrations measured in 157 monitoring wells in the second quarter of 2019. All sampled wells are included in the calibration. New wells and data that have been collected since that timeframe were not included in the updated model calibration process. Fall 2019 data from newly installed wells suggest the model predictions are conservative; the model over -predicts the actual groundwater concentrations in some isolated areas. Page 4-9 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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 relatively simple layered model. Calibration was done by manual adjustments of parameters, simultaneously matching the recent water levels measured in observation wells (Table 5-1), and matching the groundwater flow through and immediately under the ash basin dam measured at S-11. An additional flow model calibration was required to further match the pre -decanted conditions of COI distribution. The primary calibration parameters are the three-dimensional distributions of hydraulic conductivity. Each model layer has been subdivided into hydraulic conductivity zones. These model hydraulic conductivity zones are shown in Figure 5-1 through Figure 5-10, and the calibrated hydraulic conductivity values assigned to each zone in each layer are listed in Table 5-2. Starting at the top, in layers 1-9, the layers represent both the coal ash and the ash basin dam. It was necessary to calibrate the conductivity of the dam fill material in these layers (Figure 5-1 and Figure 5-2) to match the high head values in wells located in and near the dam and to match the substantial groundwater flow through the dam. The dam fill material is thicker in deeper layers to approximate a 3:1 dam slope (Figure 5-2), and it has a calibrated conductivity of 0.8 ft/d. This relatively high value for the conductivity of the dam fill was required to simultaneously match hydraulic heads of wells in and below the dam, and the leakage through and immediately under the dam. In the pre -decanting steady-state flow model, the ponded area in the ash basin has a very high conductivity value (200 ft/d) to simulate open water (Figure 5-1 and Figure 5-2). The hydraulic conductivity of the ash was estimated to be 2.5 ft/d from analytical and numerical pumping test analyses (SynTerra 2019a; SynTerra 2019b), the results of which are included in Figure 4-4. The pre -decanting conditions flow model is insensitive to the ash conductivity because the water levels around the ash basin are controlled by the ash basin ponded water elevation. The value of 2.5 ft/d used is close to the median of more than 200 slug tests performed at 14 coal ash basin sites in North Carolina shown in Figure 4-4, and it falls within the range of values measured at Belews Creek. The calibrated background hydraulic conductivity for the saprolite (layers 10-14) was 0.5 ft/d, which is near the average value for slug tests performed in saprolite at 10 coal ash basin sites in the Piedmont geologic province in North Carolina, and for slug tests performed at Belews Creek (Figure 4-5). This material is heterogeneous and zones of both higher and lower conductivity were required to match the hydraulic heads, flow Page 5-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina under the dam, and boron transport near the dam (Figure 5-3 and Figure 5-4; Table 5- 2). The range of saprolite conductivity in the model ranges from 0.05 ft/d to 4.0 ft/d, which is within the range of values measured in slug tests in the 10 Piedmont sites shown in Figure 4-5. The conductivity of the saprolite (and transition zone) below the dam appears to be relatively high. Those units are thin below the center of the dam, but a significant amount of water leaks through and immediately under the dam. Just south and west of the dam, zones of high conductivity were required to recreate the observed boron transport in this area. To the east of the dam, a zone of low permeability was needed to match the low boron concentrations seen in wells in this area. To the south, a zone of significantly low conductivity was needed along the Pine Hall Road ridge to recreate the high hydraulic heads observed here. The calibrated background conductivity for the transition zone (layers 15 and 16) was 1.0 ft/d. This value falls near the average value for slug tests performed in the transition zone at 10 Piedmont Sites in North Carolina (Figure 4-6). The transition zone is heterogeneous, with values ranging from 0.01 ft/d to 7.0 ft/d (Figure 5-5 and Figure 5-6 and Table 5-2). The highest conductivity zone is located below the center of the dam along the former creek drainage, where it contributes to leakage of water under the dam. The lowest conductivity zone is present near the northwest compliance boundary and extends beyond Middleton Loop Road. This zone was added to improve the boron calibration in that area by preventing boron from migrating into the bedrock. A low conductivity zone was placed along the Pine Hall Road ridge south of the ash basin to match the high hydraulic heads seen there. Another low conductivity zone was placed below the ridge west of the dam, which was needed to simulate the low boron concentrations observed in that area. The upper bedrock zone is 216-feet-thick and has been partitioned into three layer ranges: layers 17-18; layers 19-21; and layers 22-24. There are relatively fewer wells in the bedrock than in saprolite and the transition zone at the Site. Almost all bedrock wells are in the upper tens -of -feet of the bedrock. Three wells (AB-01BRD, AB-02BRD, and AB-03BR) were installed at depths of approximately 300 feet along the ash basin dam in March 2019. Packer tests were performed along several intervals along each of these wells and the hydraulic conductivities ranged from 0.0006 ft/d to 20 ft/d. Those wells had heads measured at approximately 50 feet less than the wells screened above them, suggesting that the wells were hydraulically isolated from shallower formations. The background conductivity value used for model layers 17-18 is 0.1 ft/d and for layers 19-21 a value of 0.04 ft/d was selected. The background hydraulic conductivity value for model layers 22-24 is 0.005 ft/d (Figure 4-7). All of these values fall within the range of Page 5-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina values measured from slug tests at 10 Piedmont sites in North Carolina, and in slug tests performed at Belews Creek (Figure 4-7). The background conductivity value used in the model is somewhat lower than the geometric mean value measured in slug tests, but for reasons described in Section 4.2, the slug test values may be biased toward the higher values that occur in shallow fracture zones. The upper bedrock conductivity ranges from 0.0002 to 0.7 in the model (Figure 5-7, Figure 5-8, Figure 5-9; Table 5-2). The lowest hydraulic conductivity values were used to replicate the low boron concentrations observed in three wells (GWA-19BR, GWA- 20BR, and GWA-27BR) west of the ash basin dam and one well (AB-02BRD) along the dam. Other shallow bedrock wells in the area, such as AB-01BR, have high boron levels. The uncertain nature of fracture flow transport makes it difficult to determine if boron is absent in the shallow bedrock around GWA-19BR, GWA-20BR, and GWA-27BR. The deep bedrock extends 250 feet (layers 25-30) below the upper bedrock, and was assigned a uniform value of 0.005 ft/d. The flow model calibration is marginally sensitive to this value, but the model conductivity is high enough to allow some water flow in the deep bedrock. The combined effect of the low rock porosity (0.01) and the high mobility of boron, results in the predicted migration of boron beneath the ash basin dam. Some transport of boron was observed in the new deep bedrock wells (AB- 01BRD, AB-02BRD, and AB-03BR) that were installed along the dam although the concentrations are less than 700 µg/L. The final calibrated flow model has a mean head residual of -0.19 feet, a root mean squared error (RMSE) of 4.02 feet, and a normalized root mean square error (NRMSE) of 1.98 percent. The range of heads at the Site is approximately 204 feet. A comparison of the observed and simulated water levels is listed in Table 5-1 and the observed and simulated levels are cross -plotted in Figure 5-11. Table 5-2 lists the best -fit hydraulic parameters from the calibration effort. The computed heads in the transition zone (model layer 15) are shown in Figure 5-12. Figure 5-13 shows the simulated heads in the upper fractured bedrock model layer (model layer 17). These are similar to the shallower heads. A close view of the heads around the ash basin dam is shown in Figure 5-14. The green lines and polygon in this figure show the blanket drain that is installed in the dam at an elevation of approximately 648 feet, a seep near the western abutment of the dam, and the creek that forms downgradient of the dam. The water flow that leaks through and immediately under the dam is measured at location S-11, near well MW-200S, and roughly averaged 180 gpm (pre -decanting conditions). The value calculated by the calibrated flow model is 150 gpm. Page 5-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina The purple line in Figure 5-15 traces the groundwater divide around the ash basin. This divide wraps around the west, south, east, and part of the northern side of the basin area. On the inside of the divide, groundwater flows toward the ash basin (blue arrows); outside of the divide, groundwater flows away from the ash basin. Groundwater from the ash basin flows to the north and northwest near the dam and the northwestern corner of the ash basin (orange arrows) under pre -decanting conditions. The approximate water balance in the ash basin watershed is summarized in Table 5-3. The size of the watershed that contributes to groundwater flow toward the ash basin depends on the locations of the groundwater divides that can change over time (e.g., ash basin is excavated or capped) and vary with depth. Under pre -decanting conditions, the watershed area contributing flow towards the basin is estimated at approximately 620 acres. Removing the areas that are capped (PHR Landfill, constructed wetlands areas) and the ash basin, the remaining area is approximately 270 acres, resulting in approximately 120 gpm of groundwater flow from recharge. Additional recharge in the south part of the ash basin adds another 20 gpm of flow, and the drains in this area remove approximately 70 gpm. Water leakage from the ponded water in the ash basin to the groundwater system is calculated to be 200 gpm, while flow through and immediately under the dam is approximately 150 gpm (pre -decanting conditions). To complete the water balance, it is estimated that approximately 120 gpm of groundwater flows through the ridge to the west and deep under the dam to the north when the ash basin water level was 750 feet. Subject to uncertainty, the estimate is related to the subsurface hydraulic conductivity distribution. 5.2 Flow Model Sensitivity Analysis A parameter sensitivity analysis was performed by varying the main hydraulic parameters (recharge, ash conductivity, saprolite conductivity, transition zone conductivity, and upper and lower bedrock conductivity) in the pre -decanting conditions flow model. Each parameter, beginning with the calibrated model, was halved and doubled to evaluate the model sensitivity. The baseline hydraulic conductivity values and recharge rate, which are the primary hydraulic parameters, were varied in this analysis. Table 5-4 shows the results of the flow parameter sensitivity analysis. The model is highly sensitive to the recharge rate and is moderately sensitive to the saprolite, transition zone, and bedrock hydraulic conductivities. The model is insensitive to ash hydraulic conductivity. 5.3 Historical Transport Model Calibration The transient flow model used for transport simulations consisted of a series of four (4) steady-state flow fields: one (1) that represents the period after the ash basin was built, but before the PHR Landfill was capped (from 1974 through 2008); one (1) that Page 5-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina represents the capped PHR Landfill, but the structural fill was not capped (from 2008 through 2012); one (1) that represents the period after the structural fill was capped (from 2012 through 2017); and one (1) that represents the period that begins when the interim extraction well system was installed (from 2017 through April 2019). The transport simulations used eight (8) spatial zones of specified boron source concentration (Figure 5-16; Tables 5-5a-c). The ash basin was split into five (5) zones: one (1) zone that represents the northern part of the ash basin; one (1) that represents the southern part of the basin, and three (3) that were used to represent boron concentrations near the dam. These zones were assigned similar boron concentrations. The PHR Landfill was divided into a northern and southern section to improve the transport model calibration. The structural fill was treated as a separate boron source zone. The concentration of boron, chloride, and TDS was held constant in ash material in these zones during historical transport simulations. The calibrated Ka values for the boron was 0.4 mL/g in saprolite and transition zone materials, and 0.02 mL/g in bedrock. The calibrated Ka values for chloride and TDS were 0.1 mL/g in the saprolite and transition zone materials, and 0.01 mL/g in bedrock. The effective porosity was set to 0.3 in the unconsolidated layers and 0.01 in the bedrock layers, and the dry bulk density of all layers was set to 1.6 g/mL. The dry bulk density was used solely to compute the retardation factor in MT3DMS, where it is multiplied by the Ka value. Tables 5-6a through 5-6c compare measured (second quarter 2019) and simulated boron, chloride, and TDS concentrations. The simulated boron concentrations in all non -ash model layers are shown in Figure 5-17. The model predicts boron transport at greater than 02L standards from the ash basin to the west and north of the compliance boundary near the ash basin dam. This boron migration appears to occur in the saprolite and transition zone primarily, but transport in the bedrock is also predicted, including some transport in deeper bedrock. The three (3) deep bedrock wells were installed at boring depths of approximately 300 feet along the dam. These wells had some boron detected but less than the 02L standard of 700 µg/L. The transport model reflects these observations, with a simulated value of 645 µg/L in well AB-01BRD (observed value of 422 µg/L); a simulated value of 75 µg/L in well AB-02BRD (observed value of 20 µg/L); and a simulated value of 602 µg/L in well AB-03BR (observed value of 538 µg/L). Some boron migration from the structural fill occurs in the simulation, but the model is not able to reproduce the high boron concentrations observed in wells GWA-23S and GWA-23D. These wells are located cross -gradient from the structural fill, and there is a deeply cut stream valley between these wells and the structural fill. Page 5-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina The results for the chloride and TDS calibrations are shown in Figures 5-18 and 5-19 and Tables 5-6b and 5.6c. The chloride and TDS plumes are not as prevalent boron. However, both chloride and TDS are present in concentrations greater than the 02L limit beyond the compliance boundary in the northwest. Overall, the simulated COI concentrations appear to reasonably match the observed concentrations in most areas, and the model -simulated boundary where the concentration is greater than the 02L standard is similar to the observed locations. The normalized root mean square error (NRMSE) of the predicted boron values is 10.2 percent and it is 14.1 percent for the predicted chloride values. For TDS, the NRMSE is 24.3 percent which is higher than for boron and chloride. The simulation results are generally consistent with the monitoring well data that show no effects on water supply wells from the ash basin, structural fill, or landfills. 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 boron Ka values by a factor of 5 from their calibrated values (0.4 mL/g in the saprolite and transition zone, and 0.02 mL/g in the bedrock). The model was then run using the adjusted Ka values, and the NRMSE was calculated and compared to the NRMSE for the calibrated model. The calibrated transport model simulates boron concentrations with NRMSE values of 1.77 percent for boron (Table 5-7). Decreasing the boron Ka by multiplying by a factor of one -fifth increases the NRMSE to 11.3 percent and increasing the boron Ka by 5 times increases the NRMSE to 12.1 percent (Table 5-7). The simulation results are seen to be sensitive to the Ka value range tested here. The sensitivity analysis results indicate that the Kd values used for boron are near optimal values. In terms of the boron plume behavior, the low Ka simulation over -predicts the extent of boron migration, while the high Kd simulation under -predicts the extent of boron migration. Page 5-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina 6.0 PREDICTIVE SIMULATIONS OF CLOSURE SCENARIOS The simulated pre -decanted boron distribution was used as the initial condition in closure simulations of future flow and transport at the BCSS. There are two simulated closure scenarios: one in which the ash in the ash basin is excavated and placed in an on -site landfill on the east side of the basin and a hybrid design where part of the ash is excavated and moved to the southern part of the ash basin where it is capped with a final cover system. Predictive simulations have also been performed for scenarios that consider each closure design with corrective action to achieve 02L compliance in a reasonable timeframe. The remediation design utilizes recharge and extraction to remediate the plume for the COIs modeled. A design with only extraction wells is not considered in this report due to poor performance demonstrated by preliminary modeling. Decanting of the ash basin began in spring 2019. The decanting is expected to be complete in October 2020. Decanting the basin will have a significant effect on the groundwater flow field. The basin water level will be lowered by approximately 70 feet, removing most free-standing water. This will result in the creation of a strong groundwater divide along Middleton Loop Road to the west of the ash basin dam, and it will greatly reduce the hydraulic driving force of COI transport. After the ash basin decanting, the final Site closure activities will continue for several years. It is anticipated that the closure -by -excavation construction could be completed within 16 years; the hybrid closure construction could be completed within 12 years. The predictive simulations are run in two steps. The first step is a simulation that uses the groundwater flow field after the ash basin is decanted. The starting boron distribution is the simulated pre -decanted conditions concentration distribution. This simulation step continues until 12 years or 16 years after decanting is completed (assumed years for hybrid and closure by excavation construction to be completed). The second step assumes that construction activities for basin closure have been completed and uses the final system flow field for transport simulations. The simulations start in 2032 or 2036 and continue for nearly 200 years after closure An interim action remediation system consisting of 10 extraction wells was been operating along the edge of Middleton Loop Road just west of the ash basin dam. These wells started operating in March 2018 and are currently pumping at a combined rate of approximately 10 gpm. Figure 6-1 shows the locations of the current extraction wells. A flow simulation was performed by matching the pre -decanted ash basin water Page 6-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina level with those observed flow rates. These well flow rates are predicted to decrease as the ash basin is decanted and groundwater levels decrease. The extraction well screens extend to the top of the bedrock surface in the model and are operated so that the water level is maintained five (5) feet above the top of the bedrock using the DRAIN feature in MODFLOW in a single gridblock per well. The DRAIN conductance for each well was calibrated based on the observed well flow rates and drawdowns. The 10 extraction wells as the interim action remediation system are assumed to remain in operation in each of the predictive simulations considered. 6.1 Interim Models with Ash Basin Decanted (2020-2032 or 2020-2036) The interim models with the ash basin decanted simulation represents a period after the basin is decanted, but before the closure -by -excavation or the hybrid closure construction is completed. Decanting the basin is simulated by removing the specified head zone that represents the water level during pre -decanting conditions flow simulation, and replacing it with a small drain area at an elevation of 680 feet, which is 70 feet below the pre -decanting water surface. The drain area is located in the deepest part of the current ash basin. Recharge at a rate of 8 in/yr is added to the ash basin. COI initial conditions come from the historical transport simulation. COI concentrations in the ash are no longer held constant. COIs can leach from the ash according to the Ka value (derived from ash leaching tests). COIs present in the underlying soil and rock are mobile and move in response to the groundwater flow with adsorption occurring according to the soil or rock Ka value. The surface drains in the southern part of the ash basin remain in this simulation. Figure 6-2 shows the simulated steady-state hydraulic heads after the basin is decanted. This case includes the 10 well interim action system, but the well flow rates are reduced due to the significantly lower groundwater levels after de -canting. A water balance was calculated and the results are summarized in Table 6-1. Direct recharge to the ash basin results in a total contribution of 119 gpm because ash basin is decanted. Contributions to the groundwater system from recharge outside of the ash basin are estimated to be 100 gpm. Drainage in the basin due to decanting is estimated to be 174 gpm. Post - decanting, the 10 interim action wells are predicted to have a combined yield of approximately 2.5 gpm in the simulation. The low flow rates from these wells reduces their effectiveness and have little effect on the water balance and transport simulations. Flow through and under the dam is estimated to be reduced to 45 gpm. This results in a predicted reduction of groundwater lost to deep flow to nearly 0 gpm. Figure 6-3 shows Page 6-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina the simulated maximum boron concentrations in all non -ash model layers in 12 years after the ash basin has been decanted. 6.2 Hybrid Closure -in -Place with Monitored Natural Attenuation The hybrid design simulations begin in 2032 using the boron distributions from the decanted simulations described earlier. The hybrid design is based on a closure plan option developed by AECOM in 2019. This design, illustrated in Figure 6-4 (from AECOM, 2019a), involves excavation of the coal ash from the northern part of the ash basin following decanting of the ash basin. This ash would be placed in the southern part of the ash basin, forming a stack in the center of the southern part of the basin. The hybrid design results in a maximum ash stack elevation of 840 feet and an overall footprint of approximately 148 acres. The design calls for the ash elevation in the ash basin fingers to gently grade toward the main ash stack. A small retention basin with a water level of 650 feet is included in the former dam location. The regraded ash would be covered with an impermeable geomembrane, soil and grass surface. The center elevated ash stack has relatively steep slopes and is surrounded by a perimeter ditch that drains toward the excavated area. The elevation of the perimeter ditch around the ash stack ranges from approximately 750 feet on the southern side of the stack to approximately 735 feet on the northern side of the stack. The regraded ash and cover system slopes downward to the north, end at an elevation of approximately 650 feet at the edge of the retention basin. The ash in the remaining part of the basin would be graded to maintain slopes of at least 1 percent toward the perimeter ditch around the ash stack. Shallow swales are built into each finger of the ash basin to direct surface water An under -drain system has been included in this simulation to collect water in the ash below the cap. These drains are located 5 feet below the elevation of the cover system in a network that follows the surface drainage ditches from the ash basin fingers [the central perimeter ditch that drains water around the main ash stack (Figure 6-4 and Figure 6-5)]. The underdrain node elevations were provided by AECOM. The ash cover system is simulated by setting the recharge rate to 0.00054 in/yr, as it is in the final cover system simulation. The excavated part of the ash basin is simulated by increasing the hydraulic conductivity of the ash to a significantly high value by restoring the recharge to the background level of 8 in/yr and by adding a drain network along the base of the excavation in former valleys. This drain network is intended to simulate springs and streams that will form in the excavated area (Figure 6-5). Boron concentrations in the excavated ash layers are set to 0 µg/L, while initial boron, chloride, Page 6-3 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina and TDS concentrations in the deeper layers come from the decanted ash basin simulation. The COI initial conditions in the remaining ash also come from the decanted ash basin simulation. The COI concentrations in the ash are variable in time, and the Kd value for boron in the ash is set to the value measured in ash leaching tests performed with ash from the basin (0.46 mL). The simulation includes the 10 well interim action system, but these wells are predicted to only be capable of low flow rates due to the lower levels of groundwater compared to pre -decanting conditions. As before, the wells are assumed to extend to the bedrock surface and the water level is maintained 5 feet above the top of bedrock. The steady-state hydraulic heads in the transition zone are shown in Figure 6-6. This design also creates a strong groundwater divide along Middleton Loop Road, west of the ash basin. An approximate water balance was calculated from the hybrid flow model. The watershed that contributes groundwater flow to the basin area for this case is approximately 653 acres. The cover over the ash basin occupies approximately 148 acres. The former constructed wetlands area (now used for surface water collection) is approximately 27 acres. The enlarged cover over the PHR Landfill is approximately 53 acres. This results in a net area of approximately 425 acres that contributes recharge to the groundwater system in the ash basin area at an average rate of approximately 176 gpm. The underdrain system beneath the ash basin cover removes 93 gpm. The springs and streams in the excavated area and just below the dam, remove 55 gpm. The retention basin south of the dam removes 8.5 gpm. The 10 extraction wells remove a total of approximately 2 gpm. This balance indicates that the deep groundwater flow in the ash basin area is only a few gpm, which is a reduction by a factor of approximately 10 from the pre -decanting conditions simulation. The simulated maximum boron concentrations in all non -ash model layers are shown in Figure 6-7a through Figure 6-7d. The compliance boundaries in these figures are shown for the current ash basin (dashed pink line) and Pine Hall Road (dashed yellow line). The hybrid design simulation suggests that boron might continue to migrate beyond the current ash basin compliance boundary at Middleton Loop Road and north of the ash basin dam for more than 100 years with basin closure and natural attenuation. 6.3 Hybrid Closure -in -Place with Active Remediation The hybrid closure scenario with groundwater corrective action such that compliance is achieved in a reasonable timeframe is simulated in two steps. The first step begins three (3) years after the decanting of the ash basin, which assumes that the construction of the remedial system outside of the ash basin is completed by 2023. It is assumed that COI Page 6-4 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina concentrations have not changed significantly 3 years after decanting has been completed. The resulting flow field is then used for the transport simulation until the completion of the hybrid basin closure in 12 years after decanting has been complete. After the hybrid basin closure has been completed, the remediation system is included in the hybrid model and the new flow field is created and used to run the transport simulation until 02L compliance is achieved. The corrective action primarily occurs northwest and west of the dam at BCSS (Figure 6-8). The remedial system considered consists of 113 extraction wells pumping a total extraction rate of 92 gpm (Table 6-2). Forty-seven (47) clean water infiltration wells are considered to introduce a total of 54 gpm of clean water to the system. The extraction wells are simulated using a vertical series of MODFLOW DRAIN points. The DRAIN bottom elevations are set to the center of the gridblock containing the drain. This simulates a condition where the water is being pumped out of the well casing to maintain a water level near the bottom of the well. 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 Ox and Az, the DRAIN conductance for a gridblock is computed as: C= 2;cKOz In 0.208Ax rW The conductance value is reduced by 50 percent to account for well skin effects. Clean water infiltration wells are treated similarly, using the General Head Boundary (GHB) condition in MODFLOW, with a conductance calculated the same way, but with a reduction of 75 percent to account for well clogging. The clean water infiltration well heads have been set to 10 feet above the ground surface. A 900 feet horizontal recharge well screened at a depth of 60 feet bgs in saprolite is included in the corrective action design. The horizontal clean water infiltration well is flowing at a rate of 110 gpm and is pressurized with a specified head of 10 feet above the ground surface. The computed heads are shown in Figure 6-8. Figure 6-9a through Figure 6-9d shows the maximum boron distribution in all non -ash layers at 50-year intervals starting 18 years after closure. The remediation system nearly achieves 02L compliance 18 years after becoming fully operational (Figure 6-9a), and compliance is achieved completely in the simulation 27 years after becoming fully Page 6-5 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina operational (not shown). There are low hydraulic conductivities zones in the model to the west of the dam in the transition zone and upper bedrock where the boron persists the longest. A groundwater divide also intersects these low hydraulic conductivity polygons in the model to the west of the dam which contributes to the challenge of achieving 02L compliance in that area due to the reduced groundwater velocities. The additional COIs considered, chloride, and TDS are shown in Figures 6-10a through Figure 6-10b and will be within compliance 18 years following full operation. 6.4 Closure -by -Excavation with Monitored Natural Attenuation The excavation design involves excavation of the ash in the ash basin, with construction of an on -Site landfill in the northern part of the ash basin footprint (Figure 6-11). This new landfill, referred to as the North Landfill, will occupy approximately 97 acres and construction is predicted to be completed by 2036. The simulation of excavation with MNA begins in 2036 using the boron distribution from the decanted pond simulation described previously. Excavation is simulated by setting the boron concentration in the ash layers in the ash basin to 0 µg/L. The concentrations of boron in the remaining soil underneath the ash basin are set to the values from the decanted pond simulation. The ash layers and dam are given a very high hydraulic conductivity (they are removed), and the previous ash basin surface water features are removed. The ash that is removed from the North Landfill area is replaced with a lower hydraulic conductivity (K=0.1 ft/d) material. Recharge occurs in the excavated part of the ash basin footprint is set to the background level of 8 inches per year except in the North Landfill, where it is set to 0.00054 in/yr. A small stream network is added to the ash basin, after initial drainage along the top of the saprolite surface. This drain network simulates the springs and streams that will form in the basin and connects to a retention pond at an elevation of 644 feet in the former dam location (Figure 6-12). An underdrain system is simulated beneath the North Landfill. This is used to maintain groundwater levels below the base of the landfill. Those drains follow the original ground surface along drainage pathways, and are simulated as MODFLOW DRAINs with a conductance of 1 ft2/d/ft along the DRAIN arc. The steady-state hydraulic heads in the transition zone are shown in Figure 6-13 for the case where there are 10 interim action extraction wells operating. The groundwater levels are now at or below the original ground surface. There is a strong groundwater divide along Middleton Loop Road, west of the ash basin. An approximate water balance was calculated from the excavation flow model. The watershed that contributes groundwater flow to the basin area increases in size to approximately 680 acres due to the lower water levels that cause the groundwater divides to move outward somewhat. The capped areas inside this watershed include the constructed wetland areas (being Page 6-6 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina converted to a surface water management area) and the Pine Hall Road Landfill. Therefore, the net area contributing recharge is approximately 511 acres. This area contributes approximately 211 gpm to the basin. The stream network inside the basin removes approximately 170 gpm (most of the water) and an additional 8 gpm discharges to the retention basin immediately upstream from the former dam location. The underdrains beneath the proposed landfill remove 17 gpm. The 10 extraction wells remove a total of approximately 2 gpm. Therefore, in this case, the net deep groundwater flow is calculated to be only a few gallons per minute. The simulated boron concentrations for all non -ash layers are shown for 14 years after closure, 64 years after closure, 114 years after closure, and 164 years after closure for the closure -by -excavation scenario with MNA in Figure 6-14a through Figure 6-14d. The dashed pink line in these figures is the current ash basin compliance boundary and the dashed yellow line represents the Pine Hall Road Landfill compliance boundary. These simulations show that boron could continue to migrate beyond the compliance boundary at Middleton Loop Road and north of the ash basin dam for more than 100 years. 6.5 Closure -by -Excavation with Active Remediation The remediation system described in Section 6.3 is applied to the closure -by -excavation scenario. The computed heads are shown in Figure 6-15 and the well information in Table 6-2 summarizes the design for this scenario. The boron distribution in Figures 6- 16a through Figure 6-16d show the boron plume at various times. The current compliance boundary is included in the figures in red. A small amount of boron persists 14 years after closure and compliance is not achieved until approximately 23 years after the system is fully functional. The area northwest of the current compliance boundary is where the plume persists the longest in this scenario because of the calibrated low conductivity zone. Sixty-four years after implementation, the plumes for the COIs considered are within the compliance boundary. The hydraulics and the evolution of the plume are similar to those predicted for the hybrid closure system, Figures 6-8 and Figure 6-9a through Figure 6-9d. The effects on chloride and TDS are also significant. Figures 6-17a through Figure 6-17b show that compliance is achieved 14 years after implementation for those COIs. 6.6 Conclusions Drawn from the Predictive Simulations The following conclusions are based on the results of the groundwater flow and transport simulations: • Predicted future boron concentrations at and beyond the current compliance boundary are similar for the excavation and hybrid design closure simulations. Page 6-7 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina • Boron is predicted to exceed 02L at the current northwest compliance boundary for 100 to 200 years without corrective action. • With corrective action measures, the predictive simulations suggest that it is possible to achieve 02L compliance in a reasonable timeframe (between 30-40 years) with the current compliance boundary. • Simulations indicate that chloride and TDS distributions respond similar to boron distributions and respond effectively to each of the active remediation approaches. • New field data are not likely to change the conclusion that excavation and the hybrid closure actions result in a similar boron, chloride, and TDS transport at the current compliance boundary. Page 6-8 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina 7.0 REFERENCES AECOM, 2019a, Conceptual Underdrain System Layout, Belews Creek Steam Station, 2018 Closure Plan (Draft 100% Permit Set), February 8, 2019. AECOM, 2019b, North Landfill Final Cover Grades, Belews Creek Steam Station, Drawing number 6, July 23, 2019. Anderson, M.P., and W.W. Woessner, 1992, Applied Groundwater Modeling Simulation of Flow and Advective Transport, Academic Press, Inc, New York NY, 381p. 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. Haven, W. T. 2003. Introduction to the North Carolina Groundwater Recharge Map. Groundwater Circular Number 19. North Carolina Department of Environment and Natural Resources. Division of Water Quality, 8 p. HDR, 2015a. Comprehensive Site Assessment Report, Belews Creek Steam Station Ash Basin, September, 2015. HDR, 2015b. Corrective Action Plan Part 1. Belews Creek Steam Station Ash Basin. December, 2015. HDR, 2016. Comprehensive Site Assessment (CSA) Supplement 2, Belews Creek Steam Station Ash Basin, August 11, 2016. 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-. 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. Page 7-1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina SynTerra, 2017, 2017 Comprehensive Site Assessment Update, October 31, 2017. SynTerra, 2018, Preliminary Updated Groundwater Flow and Transport Modeling Report for Belews Creek Steam Station, Belews Creek. November 2018. SynTerra, 2019a, Ash Basin Pumping Test Report for Belews Creek, January 2019. SynTerra, 2019b, Pumping Test Numerical Simulation Report for Belews Creek SynTerra, 2019c, Corrective Action Plan Update Belews Creek Steam Station - Duke Energy Carolinas, LLC - Belews Creek, North Carolina. December 2019. 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. USGS, 1987. 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. USGS, 1995. North Carolina; Estimated Water Use in North Carolina, 1995. USGS Fact Sheet FS-087-97. 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 7-2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina FIGURES HYBRID SCENARIO 18 YEARS POST -CLOSURE w - - '. ,. -.-.r .. _. ._....�-�.. , n POINT 2 POINT 1 +r. - is aid' HYBRID SCENARIO 168 YEARS POST -CLOSURE POINT 2 POINT 1 A LEGEND REFERENCE POINTS BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L — - — - ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. SIMULATIONS DO NOT INCLUDE ACTIVE REMEDIATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). CLOSURE BY EXCAVATION SCENARIO 14 YEARS POST -CLOSURE POINT 2 POINT 1 �1f _- ;.. . CLOSURE BY EXCAVATION SCENARIO 164 YEARS POST -CLOSURE Aj POINT 1 i _. F . 3T,; (' DGRAPHIC SCALE DUKE 1,300 O1, 300 2,600 ENERGY CAR,. (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 141P REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com FIGURE ES-1 COMPARISON OF SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 9000 8000 7000 e 6000 0 W 5000 m c u 4000 e 0 `0 3000 m 2000 1000 0 Point 1, Maximum boron concentration in all layers Hybrid --4-- Closure by Excavation — — 2L std = 700 ug/L -------- r-------r--I 2025 900 800 700 c 600 0 500 u 400 c 0 `0 300 m 200 100 0 2025 2125 2225 Year Point 3, Maximum boron concentration in all layers 2125 Year Hybrid Closure by Excavation — 2 L std = 700 ug/L 2500 2000 c 0 1500 c m 0 1000 0 `o m 500 01-- 2025 Point 2, Maximum boron concentration in all layers f Hybrid Closure by Excavation ——2Lstd=700ug/L 2125 2225 Year Location 1 is near Middleton Loop Road. Location 2 is downgradient of the dam. Location 3 is near the Dan River. DUKE DRAWN BY: Y. GEBRAI DATE: 10/10/2019 FIGURE ES-2 ENERGY REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 SUMMARY OF MAXIMUM BORON CONCENTRATION IN ALL LAYERS AS CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 FUNCTIONS OF TIME FOR THE TWO CLOSURE SCENARIOS APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT AT REFERENCE LOCATIONS ,010 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT synTerra BELEWS CREEK STEAM STATION www.synterracorp.com BELEWS CREEK, NORTH CAROLINA HYBRID SCENARIO 18 YEARS POST -CLOSURE HYBRID SCENARIO 168 YEARS POST -CLOSURE 1 w R LEGEND 0 EXTRACTION WELLS ♦ CLEAN WATER INFILTRATION WELLS HORIZONTAL CLEAN WATER INFILTRATION WELL BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION WELLS, 113 ADDITIONAL GROUNDWATER EXTRACTION WELLS, 47 CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER INFILTRATION WELLARE IN OPERATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). CLOSURE BY EXCAVATION SCENARIO 14 YEARS POST -CLOSURE i 17 (' DUKE 290 GRAPHIC SC LE 580 ENERGY CAR,. (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/10/2019 CHECKED BY: A. ALBERT DATE: 12/10/2019 APPROVED BY: C. EADY DATE: 12/10/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com FIGURE ES-3 COMPARISON OF SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS WITH REMEDIATION SCENARIOS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA Q\ - vDAN RIVEtN �S° PARCEL �� • ��_ �1 �� o DASH BASIN •� COMPLIANCE BOUNDARY -mil • ■ �p LINED RETENTION BASIN ASH BASIN PARCEL ♦ STA 03 LINE J / 0 1 \• � \COAL Q PILE o �� • 1 w POWER PLANT \\JJ z ■ PINE HALL �p Lu1NER SR Q ROAD LANDFILL (CLOSED) STRUCTURAL (CLOSED) o FILL) v FGD LANDFILL (2 Soo 800 � � gOp I Rile• • . CRAIG LANDFILL q[•T N ROAD �_ L MHP RD 8 ,p ■ ■ Q .gyp v Ll SOURCE: 2016 USGS TOPOGRAPHIC MAP, BELEWS LAKE QUADRANGLE, OBTAINED FROM THE USGS STORE AT p o https://store.usgs.gov/map-locator.STOKES r� DUKE COUNTY FIGURE 1-1 USGS LOCATION MAP ENERGY® CAROLINAS MNSTON-SALEM UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ASHEVILLE • BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA synTerra CHARLOTTE DRAWN BY: B. YOUNG DATE:05/15/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 CHECKED 3BY A. A L B E R T DATE: 12/20/2019 APPROVED BY: A. ALBERT DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT GRAPHICSCALE 1,000 0 1,000 2,000 (IN FEET)www.synterracorp.com I •loiwo I 1 r ,+ rl i q :..✓wit-i. I L.. LEGEND ASH BASIN WASTE BOUNDARY ASH BASIN COMPLIANCE BOUNDARY LANDFILL BOUNDARY (CLOSED) STRUCTURAL FILL BOUNDARY (CLOSED) LANDFILL COMPLIANCE BOUNDARY COAL PILE STORAGE AREA DUKE ENERGY CAROLINAS BELEWS CREEK PLANT SITE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY (> DUKE ENERGY 950 GRAPHIC SCALE 1,900 CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI REVISED BY: R. KIEKHAEFER DATE: 10/10/2019 DATE: 12/20/2019 100,11 CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 — Yw PROJECT MANAGER: A. ALBERT �J/` , r� M wwwsvnterracaro.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 4-1 THE MODEL BOUNDARY WAS SET AT A DISTANCE FROM THE ASH BASIN SUCH THAT NUMERICAL MODEL DOMAIN THE YCONDITIONSDIDNOTARTIFICIALLYAFFECTTHERESULTSNEAR THE ASH BASIN. UPDATED GROUNDWATER FLOW AND TRANSPORT PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY CAROLINAS. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLEEARTH PRO ONJUNE11,2019. BELEWS CREEK STEAM STATION AERIALWASCOLLECTEDONFEBRUARY3,2019. BELEWS CREEK, NORTH CAROLINA DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). r f' DUKE ENERGY DRAWN BY: Y. GEBRAI REVISED BY: R. KIEKHAEFER DATE: 10/10/2019 DATE: 12/20/2019 CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY PROJECT MANAGER: A. ALBERT DATE: 12/20/2019 www.synterracorp.com synTem FIGURE 4-2 FENCE DIAGRAM OF THE 3D HYDROSTRATIGRAPHIC MODEL USED TO CONSTRUCT THE MODEL GRID UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA DUKE ENERGY DRAWN BY: Y. GEBRAI REVISED BY: R. KIEKHAEFER DATE: 10/10/2019 DATE: 12/20/2019 CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY PROJECT MANAGER: A. ALBERT DATE: 12/20/2019 �1 J www.synterracorp.com synTerra 1 -1-1 1 I-M -- UPPER BEDROCK _ BEDROCK The smaller vertical grid spacing intersects the ash basin. FIGURE 4-3 COMPUTATIONAL GRID USED IN THE MODEL WITH 2X VERTICAL EXAGGERATION UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 1.000 1 :11 111112111111 0.200 0.000 4- 0.001 • All Sites ♦Marshall slug test Marshall pumping test analytical solution O Marshall pumping test numerical solution ♦ Model Number w • 0.010 0.100 1.000 10.000 100.000 K ft/d Analytical and numerical solutions for a coal ash pumping test at Belews Creek are included and show agreement with the slug test values. f' DUKE ENERGY DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 FIGURE 4-4 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT COAL ASH AT 14 SITES IN NORTH CAROLINA UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION *p synTerra BELEWS CREEK, NORTH CAROLINA www.synterracorp.com NON 0.2 0 1.00E-03 f' DUKE ENERGY CAROLINAS *' synTerra • All Sites ♦ Belews Creek ♦ Model Value Y' 00 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 K ft/d DRAWN BY: Y. GEBRAI DATE: 10/10/2019 FIGURE 4-5 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN CHECKED BY: A. ALBERT DATE: 12/20/2019 SAPROLITE AT 10 PIEDMONT SITES IN NORTH CAROLINA APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A.ALBERT UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA www.synterracorp.com 1 WK • All Sites ♦ Belews Creek ♦ Model Value 0.2 AkA* •� ffffim 1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 K ft/d f' DUKE ENERGY DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 FIGURE 4-6 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT THE TRANSITION ZONE AT 10 PIEDMONT SITES IN NORTH CAROLINA UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION *p synTerra BELEWS CREEK, NORTH CAROLINA www.synterracorp.com le1F:31111111 0.2 Ira or 0 *Ole 00 Ak*& * 0*/ 1.00E -05 1.00E-04 1.00E-03 1.00E-02 1.00E-01 K ft/d 1.00E+00 1.00E+01 1.00E+02 • All Sites ♦ Belews Creek ♦ Model Values Each model value corresponds to main background values in the model layer intervals used for calibration. f' DUKE ENERGY DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 FIGURE 4-7 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT THE BEDROCK AT 10 PIEDMONT SITES IN NORTH CAROLINA UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION *p S)/rlTerf dF BELEWS CREEK, NORTH CAROLINA www.synterracorp.com Creek Below Dam k'-� Dam Ash Basin Ponded Water Ash Basin Near Ponded Water \ �h Basin Pine H111 -" � Road Landfill .I •' ` '^"� ? J,_ �r (Closed) ;" .rr> 77% 1' -ram` �» 1� Structural Fill (Closed) ` w LEGEND Q RECHARGE ZONE Q FLOW AND TRANSPORT MODEL BOUNDARY V Former Constructed Wetland Treatment System z � �� _ __ Steam Station of NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). (> DUKE ENERGY CAROLINAS 100 synTerra ftf.. GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT FIGURE 4-8 DISTRIBUTION OF MODEL RECHARGE ZONES UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 'k , F �> GRAPHIC SCALE DUKE 950 G 50 1,900 LEGEND ENERGY CAROLINAS N FEET) Q CONSTANT HEAD ZONES DRAWN BY: Y. GEBRAI DATE: 10/10/2019 DRAINS REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 CHECKED BY: A. ALBERT DATE: 12/20/2019 GROUNDWATER DISCHARGE DRAINS APPROVED BY: C. EADY DATE: 12/20/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY s MTerya PROJECT MANAGER: A. ALBERT �/� �Q www.synterracorl).com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 4-9 CONSTANT HEAD ZONES ARE IN THE UPPERMOST ACTIVE MODEL MODEL SURFACE WATER FEATURES OUTSIDE ASH BASIN LAYER. UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING FEATURES THE BOUNDARYARE REPORT REPORT ACCOUNTED FOR IN THE E MODENG L. AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON BELEWS CREEK STEAM STATION JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK, NORTH CAROLINA DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). ( DUKE 950 GRAPHIC SCALE 950 1,900 LEGEND le'ENERGY CAROLINAS (IN FEET) ASH BASIN PONDED WATER DRAWN BY: Y. GEBRAI DATE: 10/10/2019 DRAINS REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 10 CHECKED BY: A. ALBERT DATE: 12/20/2019 GROUNDWATER DISCHARGE DRAINS APPROVED BY: C. EADY DATE: 12/20/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY s MTerya �Q PROJECT MANAGER: A. ALBERT �/� www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 4-10 ASH BASIN PONDED WATER HEAD IS MAINTAINED AT 750 FEET IN MODEL SURFACE WATER FEATURES INSIDE ASH BASIN THE MODEL. UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING DRAINS ARESET TO ROXIMATE GROUND OR WATER SURFACEELEVATION REPORT N THE MODE L. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON BELEWS CREEK STEAM STATION JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK, NORTH CAROLINA DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). LEGEND ie WATER SUPPLY WELLS ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY DUKE ENERGY CAROLINAS BELEWS CREEK PLANT SITE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY CAROLINAS. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). (> 1,000 GRAPHIC SCALE DUKE 000 2,000 ENERGY CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 101,11 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 synTerra PROJECT MANAGER: A. ALBERT www.svnterracorn-com FIGURE 4-11 LOCATION OF WATER SUPPLY WELLS IN MODEL AREA UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 'r . \� ., .ram! „i ._.�,5 ., ,.1� ��-,-^" E + �' •' � �:"+" i t LEGEND r ' HYDRAULIC CONDUCTIVITY: {4 t GRAPHICSC9 DUKE 950 O 50 1,900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 05/01/2019 REVISED BY R. KIEKHAEFER DATE: 12/21/2019 ALBER CHECKED 8Y: A. ALBERT DATE: 12/21/2019 - APPROVED BY: C. EADY DATE: 12/21/2019 o synTerra PROJECT MANAGER A ALBERT FLOW AND TRANSPORT MODEL BOUNDARY www.svnterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 5-1 ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY MODEL HYDRAULIC CONDUCTIVITY ZONES IN ASH AND HORIZONTAL RTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES SEAND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY LAYER 3 FOR NUMBERED POLYGONS ARE LISTED IN TABLE5-2. UPDATED GROUNDWATER FLOW AND TRANSPORT AERAERIAL WAAL GS COOLLLECTED ONGRAPHY A EBRUARINED Y�3, 22019LE EARTH PRO ON JUNE 11, 2019. MODELING REPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK STEAM STATION COORDINATE SYSTEM RIPS 3200(NAD83). BELEWS CREEK, NORTH CAROLINA The red area represents open water HK a ie f DUKE ENERGY DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 FIGURE 5-2 CROSS-SECTION THROUGH ASH BASIN DAM SHOWING HYDRAULIC CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT CONDUCTIVITY (COLORS) AND HYDRAULIC HEADS (LINES) UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION *p S)/f1TE'fld BELEWS CREEK, NORTH CAROLINA www.synterracorp.com #8, 1.0 #7, 1.0 #10, 0.5 #9, 5.0 #13, 0.5 LEGEND HYDRAULIC CONDUCTIVIT Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE LISTED IN TABLE 5-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). #6, 2.0 M #4, 0.08 #5, 0.01 #11, 6.0 #3, 0.1 #12, 0.06 I'll ftj GRAPHIC SCALE DUKE 950 O 1,900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 '41p REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com FIGURE 5-3 MODEL HYDRAULIC CONDUCTIVITY ZONES IN SAPROLITE LAYERS 10-12 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA LEGEND HYDRAULIC CONDUCTIV #10, 0.3 116 JO #4, 0.05 _ ".,-0 #12, 0.5 #9, 4.0 #11, 0.06 #5, 0.005 #1, 0.2 #3, 0.06 r GRAPHIC SCALE DUKE 950 G 950 1,900 ENERGY CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R.K FER DATE: 12/21/2019 CHECKED 8Y: ALBER A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 5-4 ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY MODEL HYDRAULIC CONDUCTIVITY ZONES IN AND HORIZONTAL RTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES SEAND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY SAPROLITE LAYERS 13-14 FOR NUMBERED POLYGONS ARE LISTED IN TABLE5-2. UPDATED GROUNDWATER FLOW AND TRANSPORT A EARTH PRO ON JUNE 11, 2019. GS Y�3, MODELING REPORT COOLLLECTED ONGRAPHY AERAERIAL WAAL EBRUARINED 22019LE DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK STEAM STATION COORDINATE SYSTEM RIPS 3200(NAD83). BELEWS CREEK, NORTH CAROLINA #12, 0.05 #7, 0.02 #5, 0.08 #15,0.001 #1, 0.5 #11, 0.05 #4, 0.01 #8, 2.0 #9, 5.0 _ #17, 1.0 LEGEND HYDRAULIC CONDUCTIVII Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE LISTED IN TABLE 5-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). #2, 8.0 #16, 0.08 GRAPHIC SCALE DUKE 950 G 950 1,900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 '41p REVISED BY: R. KIEKHAEEER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com FIGURE 5-5 MODEL HYDRAULIC CONDUCTIVITY ZONES IN TRANSITION ZONE LAYER 15 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA #8, 0.0005 #10, 1.0m k0.001 .05 .1 r#7, #17, 1.0 'r-7 LEGEND HYDRAULIC CONDUCTIVITY 0 .0 #5, 0.05 #9, 5.0#13, 0.%U# #11, 0.01 #16, 0.04 #4, 0.08 #3, 0.5 #1, 0.5 #2, 8.0 DUKE GRAPHICSC9 950 O 50 1,900 ENERGY CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 = CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT oFLOW AND TRANSPORT MODEL BOUNDARY synTerra www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 5-6 ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY MODEL HYDRAULIC CONDUCTIVITY ZONES IN AND RTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUOCTIVITY VALRIZONTAL UES SEAND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY TRANSITION ZONE LAYER 16 FOR NUMBERED POLYGONS ARE LISTED IN TABLE5-2. UPDATED GROUNDWATER FLOW AND TRANSPORT A EARTH PRO ON JUNE 11, 2019. GS Y�3, MODELING REPORT AERAERIAL WAAL COOLLLECTED ONGRAPHY 22019LE EBRUARINED DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK STEAM STATION COORDINATE SYSTEM RIPS 3200(NAD83). BELEWS CREEK, NORTH CAROLINA 6, 0.04 #12, 0.0005 #17, 0.1 �_4 LEGEND HYDRAULIC CONDUCTIVIT` Q FLOW AND TRANSPORT MODEL BOUNDARY #10, 0.001 #2, 0. #3, 0.1 0.001 #7, 0.1 ■ #8, 0.001 #11, 0.001 #5, 0.0005 NOTES: ALL BOUNDARIES ARE APPROXIMATE. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE LISTED IN TABLE 5-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). 4, 0.02 Ak DUKE ENERGY CAROLINAS 141P synTerra GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE:12/21/2019 CHECKED BY: A. ALBERT DATE:12/21/2019 APPROVED BY: C. EADY DATE:12/21/2019 PROJECT MANAGER: A. ALBERT FIGURE 5-7 MODEL HYDRAULIC CONDUCTIVITY ZONES IN UPPER FRACTURED BEDROCK LAYER 17-18 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA #13, 0.004 LEGEND HYDRAULIC CONDUCTIVIT' #12, 0.7 #10, 0.01 #5, 0.2 #2, 0,005 #8, 0.001 #6, 0.001 0.0002 1, 0.2 #9, 0.02 #4, 0.3 DUKE ENERGY CAROLINAS 141P cunTimrm F!T , 0.05 GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY. C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT Q FLOW AND TRANSPORT MODEL BOUNDARY "J' ' www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 5-8 ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY MODEL HYDRAULIC CONDUCTIVITY ZONES IN UPPER AND HORIZONTAL RTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES SEAND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FRACTURED BEDROCK LAYER 19-21 FOR NUMBERED POLYGONS ARE LISTED IN TABLE5-2. UPDATED GROUNDWATER FLOW AND TRANSPORT A EARTH PRO ON JUNE 11, 2019. GS Y�3, MODELING REPORT 22019LE EBRUARINED COOLLLECTED ONGRAPHY AERAERIAL WAAL DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK STEAM STATION COORDINATE SYSTEM RIPS 3200(NAD83). BELEWS CREEK, NORTH CAROLINA #8, 0.001 0.04 #5, 0.2 #2, 0.005 #1, 0.01, #3, 0.0005 P# 6.#6. 0.001 #10, 0.005 LEGEND HYDRAULIC CONDUCTIVITY, Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE LISTED IN TABLE 5-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). IL , 0.3 Rm GRAPHIC SCALE DUKE % 950 O 50 1,900 ENERGY CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerra PROJECT MANAGER: A. ALBERT wwwsvnt(,rracorr).com FIGURE 5-9 MODEL HYDRAULIC CONDUCTIVITY ZONES IN UPPER FRACTURED BEDROCK LAYER 22-24 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA LEGEND HYDRAULIC CONDUCTIVITY: Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITY AND HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE LISTED IN TABLE 5-2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). GORAPHIC SCALE DUKE 950 1,900 4ENERGY CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 '41p CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerid PROJECT MANAGER: A. ALBERT wwwsvnterracorr).com FIGURE 5-10 MODEL HYDRAULIC CONDUCTIVITY ZONES IN DEEP BEDROCK LAYERS 25-30 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 820 800 780 760 y 740 = 720 700 a 0 680 U 660 640 620 0 �V � 0 r X 650 700 750 800 Observed Heads (ft) f ; DUKE DRAWN BY: Y. GEBRAI DATE: 10/10/2019 FIGURE 5-11 ,%` ENERGY REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 COMPARISON OF OBSERVED AND COMPUTED HEADS FROM THE CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. DATE: 12/20/2019 A. PROJECT MANAGER:R: A. ALBERT CALIBRATED STEADY STATE FLOW MODEL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION 11610 SyrlTerl dF-- BELEWS CREEK, NORTH CAROLINA www.synterracorp.com 580 eoo zcz r p0 o � v co pip l0 66p !Z cp op 6p�Q n. p / A 6Z0 J O�o 0 n� m o l4 h 11 ., _4- LEGEND HYDRAULIC HEAD (FEET) Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. SIMULATED HEADS ARE SHOWN PRIOR TO DECANTING. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83 AND NAVD88). l� A�' "y+ J _ ow f p 0 VtLE �p DUKE 7�9�5NOEY: GORAPHICSC950 1,900 ENERGY (IN FEET) CAROLINAS Y. GEBRAI DATE: 10/10/2019 '41p REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracoLp.com FIGURE 5-12 SIMULATED HYDRAULIC HEADS IN THE TRANSITION ZONE LAYER 15 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA U U . O . V � 4 ' 650 620 680 , 'O 730 � LEGEND HYDRAULIC HEAD (FEET) Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. SIMULATED HEADS ARE SHOWN PRIOR TO DECANTING. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83 AND NAVD88). 1 � � DUKE ENERGY CAROLINAS GRAPHICSCAE 950 O9 1,900 (IN FEET) DRAWN BY: Y. GEBRAI REVISED BY: R.KFER DATE: 10/10/2019 DATE:12/21/2019 141P ALBER CHECKED 8Y: A. ALBERT DATE: 12/21/2019 APPROVED BV: C. EADV DATE:12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www.svnterracormcom FIGURE 5-13 SIMULATED HYDRAULIC HEADS IN THE FRACTURED BEDROCK LAYER 17 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA Sa \°° - CDo / goo + Aso s�o co � g0 rf r a 620 650 6g0 u �60 o 30 / I IQ E] 01 670 660 - o• p 4 �O 730 �40 1" = 450' . } o DUKE 950 GRAPHIC SCAB E 1,900 ENERGY (IN FEET) LEGEND CAROLINAS 0 S-11 DRAWN BY: Y. GEBRAI DATE: 10/10/2019 '41p REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 DRAINS CHECKED BY: A. ALBERT DATE:12/21/2019 HYDRAULIC HEAD (FEET) APPROVED BY: C. EADY DATE: 12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER A ALBERT www.s nterracor .com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 5-14 SIMULATED HEADS ARE SHOWN PRIOR TO DECANTING. SIMULATED DRAINS AND LAYER 15 TRANSITION ZONE THE MODEL DRAINS SHOWN IN THE INSET COLLECT 150 GPM, HYDRAULIC HEADS wHii.ICHcoMPARESFAvoRABLvwITHTHEMEAsuREDVALUE ATs- UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON REPORT JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK STEAM STATION DRAWING P ANECOORDINATEISYSTEMFIPS3TH A I2O0 NAD83N OF RANDNATH OA VD 8 STATE . BELEWS CREEK, NORTH CAROLINA � O00 �o �O e h 600 600 M � " O O Ts� AK d 820 o M� ✓/ 1•��� ' �✓ x _ •�--.apra>,�,FM ,'sk e. 1. ^�O � �� 77�� ., ,1: iy LEGEND DUKE 950 GORAPHIC SCAB E 1,900 ENERGY COI TRANSPORT DIRECTION CAROLINAS N FEET, - GROUNDWATER FLOW DIRECTION DRAWN BY: Y. GEBRAI DATE: 10/10/2019 GROUNDWATER DIVIDE REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 HYDRAULIC HEAD CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT NOTES: www.synterracorp.com ALL BOUNDARIES ARE APPROXIMATE. FIGURE 5-155 SIMULATED HEADS ARE SHOWN PRIOR TO DECANTING FOR THE TRANSITION ZONE GROUNDWATER DIVIDE AND FLOW DIRECTIONS LAYER 15. UPDATED GROUNDWATER FLOW AND TRANSPORT ARROWS INDICATE DIRECTION ONLY, NOT MAGNITUDE. MODELING REPORT AERAERIAL PHOTOGRAPHY AL WAS COLLECTED ONINED EBRUARY�3, 22019LE EARTH PRO ON JUNE 11, 2019. BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK, NORTH CAROLINA COORDINATE SYSTEM RIPS 3200 (NAD83 AND NAVD88). ter,. P.t i Area 1 Dam Area 2 4, 1 f A y � Dam Area 3 Northern Ash Basin .'T Southern AB Area rc .. ', ' M N Pine Hall �. Str 1 Road Landfill Fill S Pine Hall Road Landfill i' 4. LEGEND Q COI SOURCE ZONE Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). tural ° GRAPHIC SCALE DUKE 950 0 950 1900, VENERGY CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI DATE 10/10/2019 REVISED BY: DATE 12/21/2019 CHECKED 8Y. A. A. AL ALBERTERT DATE 12/21/2019 APPROVED BY C. EADV DATE: 12/21/2019 smTerra PROJECT MANAGER A. ALBERT www.svnterracorn.com FIGURE 5-16 COI SOURCE ZONES FOR HISTORICAL TRANSPORT MODEL UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA .Z - MW-04 MW-OS OB-09 BG-03S BG-03D 1 LEGEND • WELLS WITH COI OBSERVATION DATA BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BG-02BRA BG-02D BG-02S SFMW-4D .� SFMW-3D ,. h (� LE DUKE 950 GORAPHICSC950 1,900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 '41p REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www.svnterracorp.com FIGURE 5-17 SIMULATED PRE -DECANTING BORON CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 1 S GWA-19SA GWA-19BR GWA 19D - AB-01D AB-01S AB-01 BRD GWA-10S AB-01 BR GWA-10D CCR-02S CCR-01D CCR-02D GWA-17S CCR-01S �} GWA-16DA GWA-17D GWA-18SA M W-204S GWA-18D GWA-16D _ MW-204D�+{'�' GWA-16S AB-4SAP GWA-16BR MW-04 IA, MW-O6 /1, •� � � I, OB-09 M/ 'WA2_- BG-03S BG-03D LEGEND • WELLS WITH COI OBSERVATION DATA CHLORIDE > 250 mg/L - ' ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). I- BG-O2BRA] BG-02D GWA-02S BG-01D BG-02S WA-02D MW-2016R 7404 � .'D 4F CCR-12D ` CR-12S �A. GRAPHIC SCALE DUKE 950 0 950 11900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerra PROJECT MANAGER: A. ALBERT wwwsvnt(,rracorr).com FIGURE 5-18 SIMULATED PRE -DECANTING CHLORIDE CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 5;04,1p� 1 GWA-31 D GWA-31 S � GWA-19SA GWA-19BR GWA 19D AB-01D AB-01S AB-01 BRD GWA-10S AB-01BR GWA-10D CCR-02S CCR-01D CCR-02D GWA-17S CCR-01S GWA-17D GWA-16DA GWA-18SA M W-204S GWA-18D GWA-16D _ MW-204D GWA-16S GWA -16BR AB-4SAP__ GWA-09BR OB-O6 f GWA-09D l MW-04 MW-OS OB-09 GWA-26S 6WA-2613R MW-O6 _ GWA-26D MW-01D MW-02 MW-01 C BG-03S L BG-03D GWA-2SBR LEGEND • WELLS WITH COI OBSERVATION DATA TDS > 500 mg/L - ` ASH BASIN COMPLIANCE BOUNDARY - - LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BG-02BRA BG-02D GWA-02S BG-01D BG-02S WA-02D MW-2016R MW-201D --� G A-22S GWA-22D CCR- � . CCR-09D GWA-03D " CCR-11D GWA-03S "�' CCR-11S f ' CCR-12D CCR-12S 1-104S MW-104ER V-104D MW-104BRA ti �� GWA-0.D d GWA-'6S y SFMW-3zx Y MW-202S .} M1C (� DUKE ENERGY CAROLINAS 141P synTerra r GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY. C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT FIGURE 5-19 SIMULATED PRE -DECANTING TDS CONCENTRATIONS IN ALL NON -ASH LAYERS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA r� r, It � d Alw- 1 • a ' , `K EX-1 1` 40 EX-2 r, EX 3 EX-6 ♦ ♦ ♦I EX-8 R , EX-9 ■* EX-10 T GRAPHIC SCALE 4 DUKE 950 0 950 1,900 ENERGY (IN FEET) CAROLINAS t DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 11/21/2019 LEGEND CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 � EXTRACTION WELLS synTerra www.s nterracor .com PROJECT MANAGER: A. ALBERT ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY FIGURE 6-1 QFLOW AND TRANSPORT MODEL BOUNDARY EXISTING GROUNDWATER EXTRACTION WELLS NEAR NOTES: MIDDLETON LOOP ROAD ALL BOUNDARIES ARE APPROXIMATE. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. MODELING REPORT AERAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3 00 (NAD8 BELEWS CREEK, NORTH CAROLINA 670 �COM� 700 1 " 750 620 . tr 760 �r 770 650 y'�• !�; � V �A -�1 "o CFO • .�' ' r. �p 6p �" � o 720 ." ^b 4 f' DUKE SCLE 950 G50 1,900 LEGEND ENERGY (IN FEET) CAROLINAS GROUNDWATER EXTRACTION WELLS DRAWN BY: Y. GEBRAI DATE:10/10/2019 Q DRAINS REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 HYDRAULIC HEAD (FEET) APPROVED BY: C. EADY DATE:12/21/2019 ASH BASIN COMPLIANCE BOUNDARY synTerra PROJECT MANAGER: A. ALBERT - — ' LANDFILL COMPLIANCE BOUNDARY www.synterracorp.com Q FLOW AND TRANSPORT MODEL BOUNDARY FIGURE 6-2 NOTES: SIMULATED HYDRAULIC HEADS IN THE TRANSITION ALL BOUNDARIES ARE APPROXIMATE. ZONE AFTER DECANTING IN THIS GROUNDWATERIE TRACTONWEL SAREOPERATNGTHE ASH BASIN HAS BEEN NTEDAND101NTERIM UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. MODELING REPORT AER AL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK, NORTH CAROLINA COORDINATE SYSTEM FIPS 3200 (NAD83 AND NAVD88). I LEGEND BORON 700 - 4000 IJg/L BORON > 4,000 Ng/L ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE ASH BASIN HAS BEEN DECANTED AND 10 INTERIM GROUNDWATER EXTRACTION WELLS ARE OPERATING. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). i _ .yt w GRAPHIC SCALE DUKE 950 O 1,900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 '41p REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerid PROJECT MANAGER: A. ALBERT wwwsvnterracorr).com FIGURE 6-3 SIMULATED BORON CONCENTRATIONS IN ALL NON - ASH LAYERS AFTER DECANTING UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA LEGEND 2. wsa N. Z­__ 7- N= 4, nrav,•r 5,fr ' nwu aw,sea.s,EO a..,EWw,o�ma,E,.F.,,.�Fn.w.-r�,.F NOTE NiYRaRR W E" '6' Nn O aP OFA O NNMTKOC 60V RUEREn E IE; i IV ZZ 6M 1-0 ' �/_' - J•/� � �!•'� ��b '^s / Op! IMlelpll ql SpL / A; g4EPTUAL UNDERDRAIN DETAIL in- li—a cl _ --'o�= — }1 ,a ac.,F DRAFT UONCE AL UNDERDRAIN SYSTEM A. 00CM LAYOUT W ­U­(DM­W%­USET� S­ COUNff. ­ C­INA WILE ISSUED FDR REVIEW I;MYNIHETIC ��ER, io -AIL -0-D AS. �RWT m-wl CLO�D a ST '/ox RUCTURRL' DUKE ENERGY. DRAWN BY: Y. GEBRAI REVISED BY: R. KIEKHAEFER DATE: 10/10/2019 DATE: 12/20/2019 CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 APPROVED BY: C. EADY PROJECT MANAGER: A. ALBERT DATE: 12/20/2019 F_ www.synterracorp.com synTem FIGURE 6-4 HYBRID CLOSURE DESIGN USED IN SIMULATIONS (FROM AECOM, 2019) UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 1 sir ' t �{?g+ +�'^_�� may. .,►JiY ��p`r' �.- ,l� 1 • w.#�A LEGEND GROUNDWATER EXTRACTION WELLS EXCAVATED AREA DRAIN NETWORK PROPOSED ASH BASIN UNDERDRAINS Q PROPOSED RETENTION BASIN - r ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. THE RETENTION BASIN HAS A SPECIFIED HEAD OF 650 FEET. ASH BASIN UNDERDRAINS ARE PRESENT SEVEN FEET BELOW THE COVER SYSTEM. THE DRAIN NETWORK IN THE NORTHERN ASH BASIN IS USED IN THE EXCAVATED AREA TO REPRESENT SPRINGS AND STREAMS THAT MAY FORM. THE ELEVATIONS ARE SET TO THE TOP OF THE SAPROLITE SURFACE, WHICH APPROXIMATELY CORRESPONDS TO THE ORIGINAL GROUND SURFACE IN THAT AREA OF THE BASIN. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). Amh y i -Mori r. DUKE ENERGY CAROLINAS 950 GORAPHICSC9 50 14,900 (IN FEET) DRAWN BY: Y. GEBRAI REVISED BY: R. KIEKHAEFER DATE: 10/10/2019 DATE: 12/21/2019 '41p CHECKED BY: A. ALBERT DATE:12/21/2019 APPROVED BY: C. EADY DATE:12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www-svnterracorr).com FIGURE 6-5 DRAINS USED IN THE HYBRID DESIGN SIMULATION UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA - 0 580 ) r 4 580 ppp pso ol6p X O y W Y 10 590 Mr.. o F 30 5 SILL—t' w o y CD - �80 I ♦ a �) ' e 0 1 7 820 870 ,�6p._• ��. Tl ra 790 r: s r a �` RR 17 770 r 770 - -4 LEGEND GRAPHIC SCALE DUKE 950 0 950 1,900 GROUNDWATER EXTRACTION WELLS ENERGY N FEET) EXCAVATED AREA DRAIN NETWORK CAROLINAS PROPOSED ASH BASIN UNDERDRAINS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 1p Q PROPOSED RETENTION BASIN REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 HYDRAULIC HEAD (FEET) APPROVED BY: C. EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT ASH BASIN COMPLIANCE BOUNDARY www.synterracorp.com LANDFILL COMPLIANCE BOUNDARY FIGURE 6-6 NOTES: SIMULATED HYDRAULIC HEAD FOR THE ALL BOUNDARIES ARE APPROXIMATE. HYBRID SCENARIO IN THIS SIMULATION, THE 10 EXISTING GROUNDWATER EXTRACTION WELLS ARE UPDATED GROUNDWATER FLOW AND TRANSPORT OPERATING. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. BELEWS CREEK STEAM STATION AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK, NORTH CAROLINA COORDINATE SYSTEM FIPS 3200 (NAD83 AND NAVD88). t �• - ■�I tea, - r w 41 �• ft Ali -�' xft L r w. r LEGEND ` GRAPHIC SCALE DUKE 950 0 950 1,900 GROUNDWATER EXTRACTION WELLS ENERGY (IN FEET) I BORON 700 - 4,000 Ng/L CAROLINAS BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 - ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com NOTES: FIGURE 6-7a ALL BOUNDARIES ARE APPROXIMATE. SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS FOR IN THIS SIMULATION, EXTRACTWELLS ARE OPERATING. THE 10 EXISTING GROUNDWATER THE HYBRID SCENARIO 18 YEARS POST -CLOSURE AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). e t � y . {i 0*low, Ys' ram' f�► � 1 LEGEND DUKE 950 ORAPHICSCALE 950 1,900 4' GROUNDWATER EXTRACTION WELLS ENERGY., BORON 700 - 4,000 Ng/L CAROLINAS (IN FEET) BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. MEKHAEFER DATE: 12/21/2019 ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE: 12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED BY: C. EADY DATE: 12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY PROJECT MANAGER: A. ALBERT synTerra www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-7b IN THIS SIMULATION, THE 10 EXISTING GROUNDWATER SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS FOR EXTRACTION WELLS ARE OPERATING. THE HYBRID SCENARIO 68 YEARS POST -CLOSURE AERIAL PHOTOGRAPHY OTAINED FROMPRO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT JUNE 11, 2019. AERIAL WAS COLLECTED ONOGLE FOEBRUARYY 3EARTH 0119.ON BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). BELEWS CREEK, NORTH CAROLINA w r! c 1f _tee f;�M -�F'Tz- �t immAk LEGEND (� DUKE 950 ORAPHICSC9LE 50 1,900 GROUNDWATER EXTRACTION WELLS ENERGY BORON 700 - 4,000 Ng/L CAROLINAS (IN FEET) BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY 1p CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED BY:C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-7C IN THIS SIMULATION, THE 10 EXISTING GROUNDWATER SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS FOR EXTRACTION WELLS ARE OPERATING. THE HYBRID SCENARIO 118 YEARS POST -CLOSURE AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH BELEWS CREEK, NORTH CAROLINA CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). - � - ,. �, � • - ,� ter. LEGEND GORAPHICSC950 ('ALE DUKE 4 950 1,900 GROUNDWATER EXTRACTION WELLS ENERGY. BORON 700 - 4,000 Ng/L CAROLINAS N FEET, BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com NOTES: FIGURE 6-7d ALL BOUNDARIES ARE APPROXIMATE. SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS FOR THE SIMULATION, THE 10 EXISTING GROUNDWATER IN THISCTION HYBRID SCENARIO 168 YEARS POST -CLOSURE EXTRAWELLS ARE OPERATING. UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH BELEWS CREEK, NORTH CAROLINA CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). 'J J C 710 l e AM u%q3 ' n o �w 1"=850'_ 770 720 0 ^� k d r LEGEND 950 GORAPHIC SCALE 1,900 EXTRACTION WELLS DUKE ENERGY. ♦ CLEAN WATER INFILTRATION WELLS HORIZONTAL CLEAN WATER INFILTRATION WELL CAROLINAS N FEET) HYDRAULIC HEAD (FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED BY: C. EADY DATE: 12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com NOTES: FIGURE 6-8 ALL BOUNDARIES ARE APPROXIMATE. SIMULATED HYDRAULIC HEADS IN THE TRANSITION ZONE LAYER IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION 15 FOR THE HYBRID SCENARIO WITH ACTIVE WELLS, 113 ADDITIONAL GROUNDWATER EXTRACTION WELLS, 47 CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER GROUNDWATER REMEDIATION INFILTRATION WELL ARE IN OPERATION. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON JUNE MODELING REPORT 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA BELEWS CREEK STEAM STATION STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83AND NAVD88). BELEWS CREEK, NORTH CAROLINA i 11" = Arn'i LEGEND EXTRACTION WELLS A CLEAN WATER INFILTRATION WELLS HORIZONTAL CLEAN WATER INFILTRATION WELL BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L - ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION WELLS, 113 ADDITIONAL GROUNDWATER EXTRACTION WELLS, 47 CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER INFILTRATION WELLARE IN OPERATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). r Lam of GRAPHIC SC f� DUKE 950 O 9 50 1,900 ENERGY.,, mllzzl§Kzzzzz�� CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER A. ALBERT synTerrd www.svnterracorD.com FIGURE 6-9a SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS FOR THE HYBRID SCENARIO AFTER 27 YEARS OF ACTIVE GROUNDWATER REMEDIATION UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA wt LEGEND=, } sa EXTRACTION WELLS (' DUKE 950 0 950 1,900 GRAPHIC SCALE CLEAN WATER INFILTRATION WELLS ENERGY, HORIZONTAL CLEAN WATER INFILTRATION WELL CAROLINAS (IN FEET) BORON 700 - 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 BORON > 4,000 Ng/L REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 - ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 LANDFILL COMPLIANCE BOUNDARY synTerrd PROJECT MANAGER: A. ALBERT Q FLOW AND TRANSPORT MODEL BOUNDARY www.s nterracor .com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-9b INTHISSIMULATION,THE 10INTERIM GROUNDWATER SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS EXTRION ,LElGROUNDWATER WELLS47 ANWATER INFILTRATION WELLS, FOR THE HYBRID SCENARIO AFTER 77 YEARS OF ACTIVE AND ONE OPERATIONIZONTALCLEANWATERINFILTRATIONWELLARE IN GROUNDWATER REMEDIATION AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO UPDATED GROUNDWATER FLOW AND TRANSPORT ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, JMODELING REPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH BELEWS CREEK STEAM STATION CAROLINASTATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). BELEWS CREEK, NORTH CAROLINA MAW lam LEGEND EXTRACTION WELLS ♦ CLEAN WATER INFILTRATION WELLS HORIZONTAL CLEAN WATER INFILTRATION WELL BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY O FLOW AND TRANSPORT MODEL BOUNDARY r M. ' ` - •- iN r R (� DUKE ENERGY® CAROLINAS 0 synTerra GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-9C IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS FOR THE EXTRL GROUNDWATER EXTRACTION WELLS, 47 C EANIWATER INFILTRATION WELLS, HYBRID SCENARIO AFTER 127 YEARS OF AND ONEWATER INFILTRATION WELL ARE ACTIVE ACTIVE GROUNDWATER REMEDIATION IN OPERATION. UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, BELEWS CREEK STEAM STATION 2019. BELEWS CREEK, NORTH CAROLINA DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). MEU LEGEND y:. r EXTRACTION WELLS GRAPHIC SCALE ♦ CLEAN WATER INFILTRATION WELLS DUKE 950 0 950 1,900 HORIZONTAL CLEAN WATER INFILTRATION WELL ENERGY BORON 700 - 4,000 Ng/L CAROLINAS (IN FEET) BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED Br. R. KIEKHAEFER DATE: 12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY y� eIrI Q PROJECT MANAGER: A. ALBERT www.synterracoLp.com NOTES: FIGURE 6-9d ALL BOUNDARIES ARE APPROXIMATE. SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER FOR THE HYBRID SCENARIO AFTER 177 YEARS OF ACTIVE EXTCTION WELLS, 113 GROUNDWATER EXTRACTION WELLS, 47 C EANIONAL WATER INFILTRATION WELLS, GROUNDWATER REMEDIATION HORIZONTAL CLEAN WATER INFILTRATION WELL ARE IN AND OPERATION. UPDATED GROUNDWATER FLOW AND TRANSPORT UPDATED AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO MODELING REPORT 2ON 019UNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH BELEWS CREEK, NORTH CAROLINA CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). J 1 .rev r w LEGEND EXTRACTION WELLS 950 GSCALE B E 1,900 (' DUKE ♦ CLEAN WATER INFILTRATION WELLS ENERGY c (IN FEET) HORIZONTAL CLEAN WATER INFILTRATION WELL CHLORIDE > 250 m /L 9 DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED BY. C.EADY DATE:12/21/2019 PROJECT MANAGER: A. ALBERT Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra www.synterracorp.com NOTES: FIGURE 6-10a ALL BOUNDARIES ARE APPROXIMATE. SIMULATED CHLORIDE CONCENTRATIONS IN ALL NON -ASH LAYERS FOR THE HYBRID SCENARIO AFTER 27 YEARS OF ACTIVE IN THIS SIMULATION, THE 10INTERIM GROUNDWATER EXTRACTION WELLS, 113 ADDITIONAL GROUNDWATER GROUNDWATER REMEDIATION EXTRACT ON WELLS, 47 CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER INFILTRATION WELL ARE IN UPDATED GROUNDWATER FLOW AND TRANSPORT OPERATION. MODELING REPORT AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH APROJECTION OF NORTH BELEWS CREEK, NORTH CAROLINA CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). EXTRACTION WELLS GRAPHIC SCALE 950 G9 DUKE 50 1,900 4' ♦ CLEAN WATER INFILTRATION WELLS ENERGY HORIZONTAL CLEAN WATER INFILTRATION WELL (IN FEET) CAROLINAS TDS > 500 mg/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 - ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com NOTES: FIGURE 6-10b ALL BOUNDARIES ARE APPROXIMATE. SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION FOR THE HYBRID SCENARIO AFTER 27 YEARS OF ACTIVE CLEAN WATERDNAL INFIILLTRATONWELLS,ANDONEHORIIZONTALCLEAN GROUNDWATER REMEDIATION WATER INFILTRATION WELLARE IN OPERATION. UPDATED GROUNDWATER FLOW AND TRANSPORT AERIAL PHOTOGRAPHY OTAINED FROMPRO MODELING REPORT JUNE 11, 2019. AERIAL WAS COLLECTED ONOGLE FOEBRUARYY 3EARTH 0119.ON DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA BELEWS CREEK STEAM STATION STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BELEWS CREEK, NORTH CAROLINA .l' — lrf l!✓ j iR -���- WMylm Mil4FQ+FW.PIGY414A -- - - - - -- i0.a OP.PA *d WR Mica +K%9�fr9�4�R.�lrrL iM ikM arni YL,Y,i.6.1 i iYdJ: 4�. MiML M1.a tibYfi fh YL i �AdO6 Ffuii if.aa �l6�a f�Ki��. Vx 4 i19MlM1�Fi1::•�����6waK�(::i14w�LL4. .3Lr�W4 dM lKAh11 Y�1Mi,1,J>rrnf,111dd. S.4JT�YY�G mVR1LTh L i�k.IoaLoid d.rrR h��ld:�� EOM. 4 RiiR Rfa �F �Qia Pw/arAP i ��7a, �. wnx.rn ti�a fi iY4YlY� �eao+Je.L ram �t�c..�ccr.w,• � ��xo lr!/ibiYGCTiY{Md DUKE DRAWN BY: Y. GEBRAI DATE: 10/10/2019 FIGURE 6-11 ENERGY REVISED BY: R. KIEKHAEFER DATE: 12/20/2019 CLOSURE BY EXCAVATION DESIGN USED IN SIMULATIONS (FROM AECOM, 2019) CAROLINAS CHECKED BY: A. ALBERT DATE: 12/20/2019 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT APPROVED BY: C. EADY DATE: 12/20/2019 PROJECT MANAGER: A. ALBERT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA synTerra www.synterracorp.com LEGEND GROUNDWATER EXTRACTION WELLS DRAIN NETWORK LANDFILL UNDERDRAINS Q NORTH LANDFILL FOOTPRINT Q RETENTION BASIN ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. THE DRAIN NETWORK IS USED TO REPRESENT SPRINGS AND STREAMS THAT MAY FORM. THE ELEVATIONS ARE SET TO THE TOP OF THE SAPROLITE SURFACE, WHICH APPROXIMATELY CORRESPONDS TO THE ORIGINAL GROUND SURFACE. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). mi&u., -. (' DUKE 950 GRAPHIC SCALE 1,900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 '41p REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com FIGURE 6-12 DRAIN NETWORK USED IN THE CLOSURE BY EXCAVATION SIMULATIONS UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 0 580 06 00 y80 � o 0 w At� �O h 590 6p0 11 650 pp o ol 730 _ a t'' 790 760 J o O 800 r � F J / Q, bbb �60Ak V 770. =5R LEGEND a GROUNDWATER EXTRACTION WELLS GRAPHICSCALE DRAIN NETWORK DUKE 950 0 950 1,900 LANDFILL UNDERDRAINS ENERGY (IN FEET) Q NORTH LANDFILL FOOTPRINT CAROLINAS RETENTION BASIN DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 HYDRAULIC HEAD (FEET) CHECKED BY: A. ALBERT DATE: 12/21/2019 ASH BASIN COMPLIANCE BOUNDARY APPROVED BY: C. EADY DATE: 12/21/2019 LANDFILL COMPLIANCE BOUNDARY synTerra PROJECT MANAGER: A. ALBERT Q FLOW AND TRANSPORT MODEL BOUNDARY www.synterracorp.com FIGURE 6-13 NOTES: SIMULATED HYDRAULIC HEADS IN THE CLOSURE BY ALL BOUNDARIES ARE APPROXIMATE. EXCAVATION SIMULATIONS THE FORMRAIN THEEEEVAORK IS TIIONSAREDTO REPRESENT SPRINGS AND SETTTTOTHETOPOFTTHESAPROLTEESU FACEAMS T MAY UPDATED GROUNDWATER FLOW AND TRANSPORT WHICH APPROXIMATELY CORRESPONDS TO THE ORIGINAL GROUND SURFACE. MODELING REPORT AERAERIAL PHOTOGRAPHY AL WAS COLLECTED ONINED EBRUARY�3, 22019LE EARTH PRO ON JUNE 11, 2019. BELEWS CREEK STEAM STATION DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE BELEWS CREEK, NORTH CAROLINA COORDINATE SYSTEM RIPS 3200 (NAD83 AND NAVD88). Sf� a GROUNDWATER EXTRACTION WELLS BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L - ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY 4DUKE ' ENERGY CAROLINAS GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y.GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT NOTES: FIGURE 6-14a ALL BOUNDARIES ARE APPROXIMATE. SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH IN THIS SIMULATION, THE 10 EXISTING GROUNDWATER EXTRACTION LAYERS FOR THE CLOSURE BY EXCAVATION SCENARIO WELLS ARE OPERATING. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON 14 YEARS POST -CLOSURE JUNE 11, 2019.AERIAL WAS COLLECTED ON FEBRUARY 3,2019. UPDATED GROUNDWATER FLOW AND TRANSPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA MODELING REPORT STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 1 ^ Ile i Hr MN{w ...�.► y j LEGEND a GROUNDWATER EXTRACTION WELLS BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L - ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 EXISTING GROUNDWATER EXTRACTION WELLS ARE OPERATING. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). (� DUKE ENERGY® GRAPHIC SCALE 950 O 50 1,900 CAROLINAS (IN FEET) DRAWN BY: Y. GEBRAI REVISED BY: R. KIEKHAEFER DATE: 10/10/2019 DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER A. ALBERT synTerrd www.svnterracorr).com FIGURE 6-14b SIMULATED BORON CONCENTRATIONS IN ALL NON - ASH LAYERS FOR THE CLOSURE BY EXCAVATION SCENARIO 64 YEARS POST -CLOSURE UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA Ile ^ j H�r� yNW{w ��► � j F Sr� Y- LEGEND GROUNDWATER EXTRACTION WELLS BORON 700 - 4,000 Ng/L BORON > 4,000 Ng/L ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 EXISTING GROUNDWATER EXTRACTION WELLS ARE OPERATING. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM RIPS 3200 (NAD83). A GRAPHIC SCALE DUKE 950 0 950 1,900 ENERGY (IN FEET) CAROLINAS DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY. R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT FIGURE 6-14c SIMULATED BORON CONCENTRATIONS IN ALL NON - ASH LAYERS FOR THE CLOSURE BY EXCAVATION SCENARIO 114 YEARS POST -CLOSURE UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA Ile j H�r� yNW{w ��► � j Sf� � l • / tea. gram am GROUNDWATER EXTRACTION WELLS BORON 700 - 4,000 Ng/L BORON > 4,000 gg/L - ASH BASIN COMPLIANCE BOUNDARY - - LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 EXISTING GROUNDWATER EXTRACTION WELLS ARE OPERATING. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). DUKE ENERGY CAROLINAS 141P WnTem GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT FIGURE 6-14d SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS FOR THE CLOSURE BY EXCAVATION SCENARIO 164 YEARS POST -CLOSURE UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA o " 580'�60 ,Yk� r p� p� 0� a_o o •� ,pop ,:- 0590 62p �50 640 760 w�� LEGEND GC EXTRACTION WELLS ♦ CLEAN WATER INFILTRATION WELLS HORIZONTAL CLEAN WATER INFILTRATION WELL HYDRAULIC HEAD (FEET) ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION WELLS, 113 ADDITIONAL GROUNDWATER EXTRACTION WELLS, 47 CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER INFILTRATION WELLARE IN OPERATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83 AND NAVD88). GRAPHIC SCALE (' DUKE 950 0 950 1,900 ENERGY c (IN FEET) DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED BY: R. KIEKHAEFER DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED BY: C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT FIGURE 6-15 SIMULATED HYDRAULIC HEADS IN THE TRANSITION ZONE LAYER 15 FOR THE CLOSURE BY EXCAVATION SCENARIO WITH ACTIVE GROUNDWATER REMEDIATION UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION 40 . LEGENDRY EXTRACTION WELLS GRAPHIC SCALE A CLEAN WATER INFILTRATION WELLS DUKE 950 0 950 1,900 HORIZONTAL CLEAN WATER INFILTRATION WELL ENERGY BORON 700 - 4,000 Ng/L CAROLINAS (IN FEET) BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED Br. R. KIEKHAEFER DATE: 12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.sVnterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-16a IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS CLEAN WATERDNAL INFIILLTRATON WELLS, AND ONE HORIZONTAL CLEAN FOR THE CLOSURE BY EXCAVATION SCENARIO AFTER 27 YEARS WATER INFILTRATION WELLARE IN OPERATION. OF ACTIVE GROUNDWATER REMEDIATION AERIAL PHOTOGRAPHY OTAINED FROMEARTPRO UPDATED GROUNDWATER FLOW AND TRANSPORT JUNE11,2019.AERIAL WASCOLLECT DONOGLE FOEBRUARYY3H 0119.ON DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA MODELING REPORT STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA X I ♦ LEGEND - EXTRACTION WELLS GRAPHIC SCALE A CLEAN WATER INFILTRATION WELLS DUKE 950 0 950 1,900 HORIZONTAL CLEAN WATER INFILTRATION WELL ENERGY BORON 700 - 4,000 Ng/L CAROLINAS (IN FEET) BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED Br.R. KIEKHAEFER DATE: 12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-16b IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS WELLS47 CLEAN 'WATERDINFIILLTRATON WELLS, AND ONE HORIZONTAL CNAL GROUNDWATER EXTRACTION WELLS 1LEAN FOR THE CLOSURE BY EXCAVATION SCENARIO AFTER 77 YEARS WATER INFILTRATION WELLARE IN OPERATION. OF ACTIVE GROUNDWATER REMEDIATION AERIAL PHOTOGRAPHY OTAINED FROMEARTPRO UPDATED GROUNDWATER FLOW AND TRANSPORT JUNE11,2019.AERIAL WASCOLLECT DONOGLE FOEBRUARYY3H 0119.ON DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA MODELING REPORT STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA 1" = 850' ice-: LEGEND EXTRACTION WELLS GRAPHIC SCALE ♦ CLEAN WATER INFILTRATION WELLS DUKE 950 0 950 1,900 HORIZONTAL CLEAN WATER INFILTRATION WELL ENERGY BORON 700 - 4,000 Ng/L CAROLINAS (IN FEET) BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED Br.R. KIEKHAEFER DATE:12/21/2019 - ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.sVnterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-16C IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS WELLS, 1 1 3 ADDITIONAL GROUNDWATER EXTRACTION WELLS, 47 FOR THE CLOSURE BY EXCAVATION SCENARIO AFTER 127 YEARS CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER INFILTRATION WELLARE IN OPERATION. OF ACTIVE GROUNDWATER REMEDIATION AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON UPDATED GROUNDWATER FLOW AND TRANSPORT JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. MODELING REPORT DRAWSTATEING HAS BEEN SET P PLANE COORDINATEITH A SYSTEM FIPS 3ION OF 22 0 (NAD88) NORTH CAROLINA BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA y? _ J } i LEGEND EXTRACTION WELLS GRAPHIC SCALE ♦ CLEAN WATER INFILTRATION WELLS DUKE 950 0 950 1,900 HORIZONTAL CLEAN WATER INFILTRATION WELL ENERGY BORON 700 - 4,000 Ng/L (IN FEET) CAROLINAS BORON > 4,000 Ng/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED Br. R. KIEKHAEFER DATE:12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY PROJECT MANAGER: A. ALBERT errs www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-16d IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION SIMULATED BORON CONCENTRATIONS IN ALL NON -ASH LAYERS CLEAN WATERDNAL INFIILLTRATONWELLS,ANDONEHORIIZONTALCLEAN FOR THE CLOSURE BY EXCAVATION SCENARIO AFTER WATER INFILTRATION WELLARE IN OPERATION. 177 YEARS OF ACTIVE GROUNDWATER REMEDIATION AERIAL PHOTOGRAPHY OTAINED FROMPRO JUNE11,2019.AERIAL WASCOLLECT DONOGLE FOEBRUARYY3EARTH 0119.ON UPDATED GROUNDWATER FLOW AND TRANSPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA MODELING REPORT STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA c MEM :z F LEGEND EXTRACTION WELLS A CLEAN WATER INFILTRATION WELLS HORIZONTAL CLEAN WATER INFILTRATION WELL CHLORIDE > 250 mg/L - - ASH BASIN COMPLIANCE BOUNDARY LANDFILL COMPLIANCE BOUNDARY Q FLOW AND TRANSPORT MODEL BOUNDARY NOTES: ALL BOUNDARIES ARE APPROXIMATE. IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION WELLS, 113 ADDITIONAL GROUNDWATER EXTRACTION WELLS, 47 CLEAN WATER INFILTRATION WELLS, AND ONE HORIZONTAL CLEAN WATER INFILTRATION WELLARE IN OPERATION. AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON JUNE 11, 2019. AERIAL WAS COLLECTED ON FEBRUARY 3, 2019. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). DUKE ENERGY CAROLINAS GRAPHIC SCALE 950 0 950 1,900 (IN FEET) DRAWN BY: Y. GEBRAI REVISED Br. R. KIEKHAEFER DATE: 10/10/2019 DATE: 12/21/2019 CHECKED BY: A. ALBERT DATE: 12/21/2019 APPROVED Br. C. EADY DATE: 12/21/2019 PROJECT MANAGER: A. ALBERT FIGURE 6-17a SIMULATED CHLORIDE CONCENTRATIONS IN ALL NON -ASH LAYERS FOR THE CLOSURE BY EXCAVATION SCENARIO AFTER 27 YEARS OF ACTIVE GROUNDWATER REMEDIATION UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA `r . el LEGEND GRAPHIC SCALE EXTRACTION WELLS DUKE 950 G1,900 CLEAN WATER INFILTRATION WELLS ENERGY (IN FEET) HORIZONTAL CLEAN WATER INFILTRATION WELL CAROLINAS TDS > 500 mg/L DRAWN BY: Y. GEBRAI DATE: 10/10/2019 REVISED Br.R. KIEKHAEFER DATE:12/21/2019 ' ASH BASIN COMPLIANCE BOUNDARY CHECKED BY: A. ALBERT DATE:12/21/2019 LANDFILL COMPLIANCE BOUNDARY APPROVED Br. C.EADY DATE:12/21/2019 Q FLOW AND TRANSPORT MODEL BOUNDARY synTerra PROJECT MANAGER: A. ALBERT www.synterracorp.com NOTES: ALL BOUNDARIES ARE APPROXIMATE. FIGURE 6-17b IN THIS SIMULATION, THE 10 INTERIM GROUNDWATER EXTRACTION SIMULATED TDS CONCENTRATIONS IN ALL NON -ASH LAYERS 47 CLEAN WATERDNAL INFIILLTRATON WELLS, AND ONE HORIZONTAL CLEAN FOR THE CLOSURE BY EXCAVATION SCENARIO AFTER 27 YEARS WATER INFILTRATION WELLARE IN OPERATION. OF ACTIVE GROUNDWATER REMEDIATION AERIAL PHOTOGRAPHY OTAINED FROMPRO JUNE11,2019.AERIAL WASCOLLECT DONOGLE FOEBRUARYY3EARTH 0119.ON UPDATED GROUNDWATER FLOW AND TRANSPORT DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA MODELING REPORT STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83). BELEWS CREEK STEAM STATION BELEWS CREEK, NORTH CAROLINA Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLES Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-1 COMPARISON OF OBSERVED AND COMPUTED HEADS FOR THE CALIBRATED FLOW MODEL. Well Observed Head Computed Head Residual Head AB-01 BR 734.51 728.84 5.67 AB-01BRD 672.11 673.85 -1.74 AB-01 D 734.39 739.52 -5.13 AB-01S 732.74 740.47 -7.72 AB-02BR 726.84 718.35 8.49 AB-02BRD 676.01 681.66 -5.65 AB-02D 732.46 726.08 6.37 AB-02S 741.94 733.93 8.01 AB-03BR 674.46 681.30 -6.84 AB-03D 724.41 730.13 -5.72 AB-03S 735.09 737.29 -2.20 AB-04BR 755.16 754.12 1.05 AB-04BRD 755.00 754.18 0.82 AB-04D 755.20 754.13 1.07 AB-04S 755.78 754.23 1.55 AB-04SL 755.39 754.15 1.24 AB-05D 755.47 754.88 0.59 AB-05S 755.75 754.93 0.82 AB-05SL 755.95 754.88 1.07 AB-06D 757.69 757.85 -0.16 AB-06S 758.52 757.99 0.53 AB-06SL 758.41 757.94 0.46 AB-07D 757.83 758.12 -0.29 AB-07S 759.03 758.12 0.91 AB-08D 757.48 754.86 2.62 AB-08S 757.82 755.03 2.80 AB-08SL 757.54 754.90 2.64 AB-09BR 758.28 756.63 1.65 AB-09BRD 759.58 757.04 2.54 AB-09D 758.59 755.89 2.70 AB-09S 759.27 755.43 3.84 AB-4 Ash Well 755.10 754.10 1.00 AB-4 Lower Ash 755.21 754.12 1.09 AB-4 Medium Ash 755.20 754.15 1.05 AB-4 Medium Ash 30 755.28 754.19 1.09 AB SAP2 755.18 754.03 1.15 AB-4 Upper Ash 755.24 754.21 1.03 Page 1 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-1 COMPARISON OF OBSERVED AND COMPUTED HEADS FOR THE CALIBRATED FLOW MODEL. Well Observed Head Computed Head Residual Head AB-4SAP 755.36 754.15 1.21 BG-01D 761.79 765.06 -3.27 BG-02BRA 762.80 760.49 2.31 BG-02D 765.45 760.75 4.70 BG-02S 763.57 760.86 2.71 BG-03D 815.31 814.48 0.83 BG-03S 813.55 815.36 -1.81 CCR-01 D 749.28 749.64 -0.36 CCR-01S 749.67 749.65 0.02 CCR-02D 748.59 747.27 1.32 CCR-02S 748.25 747.26 0.99 CCR-04D 741.42 743.43 -2.01 CCR-04S 740.30 743.44 -3.14 CCR-05D 705.51 706.53 -1.02 CCR-05S 723.57 716.83 6.74 CCR-06D 643.63 644.37 -0.74 CCR-06S 645.64 644.75 0.89 CCR-07D 674.01 664.36 9.65 CCR-07S 675.36 671.00 4.36 CCR-08AD 737.98 746.91 -8.93 CCR-08D 703.86 708.62 -4.76 CCR-08S 703.82 708.83 -5.01 CCR-09D 740.12 749.35 -9.23 CCR-09S 749.28 749.43 -0.15 CCR-11D 752.96 752.42 0.54 CCR-11S 753.90 752.39 1.51 CCR-12D 751.69 754.08 -2.39 CCR-12S 751.83 754.08 -2.25 CCR-13 BR 689.18 683.79 5.39 CCR-13D 690.43 684.17 6.26 CCR-1341- 690.38 683.97 6.41 GWA-01 BR 677.72 676.44 1.28 GWA-01D 717.08 712.45 4.63 GWA-01S 718.50 712.32 6.18 GWA-02D 748.22 753.35 -5.13 GWA-02S 748.66 753.96 -5.30 GWA-03D 727.47 732.02 -4.55 Page 2 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-1 COMPARISON OF OBSERVED AND COMPUTED HEADS FOR THE CALIBRATED FLOW MODEL. Well Observed Head Computed Head Residual Head GWA-03S 727.94 732.14 -4.20 GWA-06D 746.34 756.19 -9.85 GWA-06S 760.36 757.36 3.00 GWA-07D 785.85 788.88 -3.03 GWA-07SA 786.44 789.94 -3.50 GWA-08D 800.46 798.89 1.57 GWA-08S 804.18 800.72 3.46 GWA-09BR 746.78 753.62 -6.84 GWA-09D 750.38 753.72 -3.34 GWA-09S 752.40 753.82 -1.42 GWA-10D 741.44 740.37 1.07 GWA-10S 742.43 740.27 2.16 GWA-11D 724.89 731.96 -7.07 GWA-11S 729.38 732.16 -2.78 GWA-12BR 772.94 776.84 -3.90 GWA-12D 781.22 778.96 2.26 GWA-12S 781.24 779.01 2.23 GWA-16BR 749.34 750.96 -1.62 GWA-16D 748.33 751.15 -2.82 GWA-16DA 748.21 751.12 -2.91 GWA-16S 750.17 751.24 -1.07 GWA-17D 749.96 749.40 0.56 GWA-17S 750.31 749.46 0.85 GWA-18D 748.61 747.79 0.82 GWA-18SA 748.44 747.76 0.68 GWA-19BR 717.21 715.59 1.62 GWA-19D 728.97 720.49 8.48 GWA-19SA 733.62 733.55 0.07 GWA-20BR 741.37 742.65 -1.28 GWA-20D 746.76 746.77 -0.01 GWA-20SA 747.52 746.80 0.72 GWA-21D 718.49 722.58 -4.09 GWA-21S 719.86 723.90 -4.04 GWA-22D 726.84 731.63 -4.79 GWA-22S 730.62 730.69 -0.07 GWA-23D 788.00 788.48 -0.48 GWA-23S 785.39 788.50 -3.11 Page 3 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-1 COMPARISON OF OBSERVED AND COMPUTED HEADS FOR THE CALIBRATED FLOW MODEL. Well Observed Head Computed Head Residual Head GWA-24BR 616.41 623.41 -7.00 GWA-24D 627.76 623.12 4.64 GWA-24S 632.16 624.54 7.62 GWA-25BR 813.71 817.12 -3.41 GWA-26BR 813.80 814.42 -0.62 GWA-26D 813.83 814.89 -1.06 GWA-26S 814.10 815.41 -1.31 GWA-27BR 726.17 735.44 -9.27 GWA-27D 744.01 742.78 1.23 GWA-27S 745.92 742.80 3.12 GWA-30D 718.77 717.85 0.92 GWA-30S 718.50 718.16 0.34 GWA-31 D 708.62 702.73 5.89 GWA-31S 700.34 703.04 -2.70 GWA-32D 681.91 684.04 -2.13 GWA-32S 688.38 682.26 6.12 MW-01 819.32 818.08 1.25 MW-01D 811.43 813.36 -1.93 MW-02 815.08 816.09 -1.01 MW-03 801.91 805.40 -3.49 MW-04 752.93 753.57 -0.64 MW-05 760.90 764.12 -3.22 MW-06 804.17 812.20 -8.03 MW-07 808.75 808.61 0.14 MW-101D 659.54 663.62 -4.08 MW-101S 664.30 664.45 -0.15 MW-102D 652.80 646.05 6.75 MW-102S 642.21 646.26 -4.05 MW-103D 678.42 688.01 -9.59 MW-103S 678.45 688.05 -9.60 MW-104BR 758.06 756.76 1.30 MW-104BRA 759.22 756.65 2.56 MW-104D 757.56 756.95 0.61 MW-104S 756.75 757.02 -0.27 MW-200BR 637.00 637.82 -0.82 MW-200D 629.99 634.59 -4.60 M W-200S 630.54 634.53 -3.99 Page 4 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-1 COMPARISON OF OBSERVED AND COMPUTED HEADS FOR THE CALIBRATED FLOW MODEL. Well Observed Head Computed Head Residual Head MW-201BR 749.39 752.99 -3.60 M W-201 D 749.90 753.39 -3.49 MW-202BR 744.07 739.55 4.52 M W-202D 742.84 739.84 3.00 MW-202S 741.93 739.75 2.18 MW-203BR 752.78 755.12 -2.34 MW-203D 752.36 755.12 -2.75 MW-203S 752.70 755.23 -2.53 MW-204D 749.80 751.11 -1.31 MW-204S 749.67 751.13 -1.46 MW2-07 763.52 767.86 -4.34 MW2-09 791.84 787.38 4.46 OB-04 754.84 755.58 -0.74 OB-05 755.05 754.22 0.83 OB-09 761.76 760.65 1.11 SFMW-1D 787.57 784.27 3.30 SFMW-2D 805.12 795.45 9.67 SFMW-3D 748.89 751.03 -2.14 SFMW-4D 756.20 755.60 0.60 SFM W-5D 771.01 761.36 9.65 Notes: Ft - feet Ft. NAVD 88 - North American Vertical Datum of 1988 Revised by: YG Checked by: AA Page 5 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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:Kv Ash Basin 1-9 #3 coal ash 2.5 16 Ash Basin (lake or excavated) 1-9 #2 lake, excavated coal ash 200 1 Ash Basin Dam 1-9 #1 ash basin dam 0.8 2 Saprolite (upper) 10-12 #13 saprolite main model 0.5 1 10-12 #1 0.2 1 10-12 #2 1.0 1 10-12 #3 0.1 1 10-12 #4 0.08 1 10-12 #5 0.01 1 10-12 #6 2.0 1 10-12 #7 1.0 1 10-12 #8 1.0 1 10-12 #9 5.0 1 10-12 #10 0.06 1 10-12 #11 6.0 1 10-12 #12 0.06 1 Saprolite (lower) 13-14 #12 saprolite main model 0.5 1 13-14 #1 0.2 1 13-14 #2 1.0 1 13-14 #3 0.06 1 13-14 #4 0.05 1 13-14 #5 0.005 1 13-14 #6 2.0 1 13-14 #7 3.0 1 13-14 #8 0.05 1 13-14 #9 4.0 1 13-14 #10 0.3 1 13-14 # 11 0.5 1 Transition zone 15 #17 TZ main model 1.0 1 15 #1 0.5 1 15 #2 8.0 1 15 #3 0.5 1 15 #4 0.01 1 15 #5 0.08 1 15 #6 0.05 1 15 #7 0.02 1 15 #8 2.0 1 15 #9 5.0 1 Page 6 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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:Kv 15 # 10 1.0 1 15 #11 0.05 1 15 #12 0.05 1 15 # 13 0.01 1 15 #14 0.1 1 15 # 15 0.001 1 15 # 16 0.08 1 Transition zone 16 #17 TZ main model 1.0 1 16 #1 0.5 1 16 #2 8 1 16 #3 0.5 1 16 #4 0.08 1 16 #5 0.05 1 16 #6 2 1 16 #7 0.005 1 16 #8 0.0005 1 16 #9 5 1 16 # 10 1 1 16 #11 0.01 1 16 #12 0.05 1 16 # 13 0.01 1 16 #14 0.1 1 16 # 15 0.001 1 16 # 16 0.04 1 Bedrock (upper) 17-18 #17 main model 0.1 1 17-18 #1 0.05 1 17-18 #2 0.005 1 17-18 #3 0.1 1 17-18 #4 0.001 1 17-18 #5 0.0005 1 17-18 #6 0.3 1 17-18 #7 0.1 1 17-18 #8 0.001 1 17-18 #9 0.5 1 17-18 #10 0.001 1 17-18 #11 0.001 1 17-18 #12 0.0005 1 17-18 #13 0.0005 1 17-18 #14 0.02 1 17-18 #15 0.001 1 17-18 # 16 0.04 1 Page 7 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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:Kv Bedrock (upper) 19-21 #13 main model 0.04 1 19-21 #1 0.05 1 19-21 #2 0.005 1 19-21 #3 0.0002 1 19-21 #4 0.3 1 19-21 #5 0.2 1 19-21 #6 0.001 1 19-21 #7 0.1 1 19-21 #8 0.001 1 19-21 #9 0.02 1 19-21 # 10 0.01 1 19-21 # 11 0.2 1 19-21 # 12 0.7 1 Bedrock (upper) 22-24 #10 main model 0.005 1 22-24 #1 0.05 1 22-24 #2 0.005 1 22-24 #3 0.0005 1 22-24 #4 0.3 1 22-24 #5 0.2 1 22-24 #6 0.001 1 22-24 #7 0.02 1 22-24 #8 0.001 1 22-24 #9 1 0.04 1 1 Bedrock (lower) 1 25-30 #1 main model 1 0.005 1 Notes: Ft/d - feet per day Kn - horizontal hydraulic conductivity K - vertical hydraulic conductivity Prepared by: YG Checked by: AA Page 8 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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 ash basin 20 Direct recharge to watershed outside of ash basin 120 Ash basin ponds 200 70 Drainage outside of the ash basin Flow through and under the dam 150 Notes: Gpm - gallons per minute Prepared by: YG Checked by: AA Page 9 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-4 FLOW MODEL SENSITIVITY ANALYSIS Parameter Decrease by 1/2 Calibrated Increase by 2 Recharge (8 in/yr) 4.69% 1.98% 6.04% Ash Kh (2.5 ft/d) 1.97% 1.98% 2.00% Saprolite Kh (0.5 ft/d) 2.14% 1.98% 2.16% TZ Kh (1.0 ft/d) 2.28% 1.98% 2.44% Upper Bedrock Kh (0.04 ft/d) 2.50% 1.98% 2.23% Lower Bedrock Kh (0.005 ft/d) 2.20% 1.98% 2.14% Prepared by: YG Checked by: AA Notes• The normalized root mean square error (NRMSE) in the calculated heads is shown In/yr - inches per year Ft/d - feet per day Page 10 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-5A ASH BASIN BORON SOURCE CONCENTRATIONS USED IN HISTORICAL TRANSPORT MODEL Northern Dam Dam Dam AB Southern N PHR S PHR Structural Date Ponded AB Area Landfill Landfill Fill Area Area Area Area #1 #2 #3 1974- 1985 13,400 13,100 0 0 0 13,400 5,000 11,000 Boron 1985- 2004 13,400 13,100 40,000 25,000 0 13,400 5,000 11,000 Boron 2004- 2019 13,400 13,100 40,000 25,000 25,000 13,400 5,000 11,000 Boron Notes: pg/L - micrograms per liter Prepared by: YG Checked by: AA Page 11 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-5B ASH BASIN CHLORIDE SOURCE CONCENTRATIONS USED IN HISTORICAL TRANSPORT MODEL Northern AB Southern N PHR S PHR Structural Dam Dam Dam Date Ponded AB Area Landfill Landfill Fill Area Area Area #1 #2 #3 Area 1974- 1985 Chloride 600 500 0 0 0 700 500 600 1985- 2004 Chloride 600 500 50 50 0 700 500 600 2004- 2019 Chloride 600 500 50 50 50 700 500 600 Notes: mg/L - milligrams per liter Prepared by: YG Checked by: AA Page 12 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-5C ASH BASIN TDS SOURCE CONCENTRATIONS USED IN HISTORICAL TRANSPORT MODEL Northern AB Southern N PHR S PHR Structural Dam Dam Dam Date Ponded AB Area Landfill Landfill Fill Area Area Area Area #1 #2 #3 1974- 1985 2,000 1,100 0 0 0 3,000 2,500 1,500 TDS 1985- 2004 2,000 1,100 3,000 2,000 0 3,000 2,500 1,500 TDS 2004- 2019 2,000 1,100 3,000 2,000 3,000 3,000 2,500 1,500 TDS Notes: mg/L - milligrams per liter Prepared by: YG Checked by: AA Page 13 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6A COMPARISON OF OBSERVED AND SIMULATED BORON CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) AB-01BR 5920 13208 AB-01BRD 422 645 AB-01D 11400 13371 AB-01S 13600 13421 AB-02BR 8870 3750 AB-02BRD 20 75 AB-02D 8390 5081 AB-02S 50 101 AB-03BR 538 602 AB-03D 2500 8449 AB-03S 11800 9995 AB-04BR 0 0 AB-04BRD 0 0 AB-04D 87 0 AB-04S 28700 13100 AB-04SL 14000 13100 AB-4SAP 0 12 AB-4 Lower Ash 0 13100 AB-05D 0 0 AB-05S 12000 13100 AB-05SL 14100 13100 AB-06D 0 0 AB-06S 103 90 AB-06SL 208 18 AB-07D 0 0 AB-07S 257 0 AB-08D 0 0 AB-08S 964 13100 AB-08SL 6010 13100 AB-09BR 0 0 AB-09BRD 0 0 AB-09D 71.8 0 AB-09S 0 0 Page 14 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6A COMPARISON OF OBSERVED AND SIMULATED BORON CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) BG-01 D 0 0 BG-02BRA 0 0 BG-02D 0 0 BG-02S 0 0 BG-03D 0 0 BG-03S 0 0 CCR-01 D 15 0 CCR-01S 25 0 CCR-02D 3660 1517 CCR-02S 4600 8690 CCR-04D 6270 7377 CCR-04S 5250 8305 CCR-05D 53.4 9706 CCR-05S 10700 13228 CCR-06D 10400 11699 CCR-06S 13300 9744 CCR-07D 5040 1668 CCR-07S 66.7 14 CCR-08AD 9360 5117 CCR-08D 9350 6582 CCR-08S 9160 6739 CCR-09D 71.6 28 CCR-09S 153 1 CCR-11D 3.9 -1 CCR-11S 4.5 1 CCR-12D 3.5 0 CCR-12S 0 0 CCR-13BR 0 452 CCR-13D 0 31 CCR-13S 0 3 GWA-01BR 0 317 GWA-01D 12 5 GWA-01S 340 90 Page 15 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6A COMPARISON OF OBSERVED AND SIMULATED BORON CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) GWA-02D 0 0 GWA-02S 0 0 GWA-03D 0 0 GWA-03S 0 0 GWA-06D 0 0 GWA-06S 38 0 GWA-07D 0 0 GWA-07SA 101 0 GWA-08D 8 0 GWA-08S 365 0 GWA-09BR 176 0 GWA-09D 0 0 GWA-09S 0 0 GWA-10D 0 7 GWA-10S 518 610 GWA-11D 614 288 GWA-11S 620 489 GWA-12BR 0 0 GWA-12D 0 0 GWA-12S 0 0 GWA-16BR 0 0 GWA-16D 39 0 GWA-16DA 0 0 GWA-16S 0 0 GWA-17D 0 0 GWA-17S 0 0 GWA-18D 20 70 GWA-18SA 706 872 GWA-19BR 50 49 GWA-19D 50 204 GWA-19SA 1760 2476 GWA-20BR 34 242 GWA-20D 9630 2584 Page 16 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6A COMPARISON OF OBSERVED AND SIMULATED BORON CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) GWA-20SA 10200 11424 GWA-21D 447 801 GWA-21S 328 457 GWA-22D 0 12 GWA-22S 0 1 GWA-23D 8140 0 GWA-23S 2630 0 GWA-24BR 0 32 GWA-24D 42 7 GWA-24S 0 2 GWA-25BR 0 0 GWA-26BR 0 0 GWA-26D 0 0 GWA-26S 0 0 GWA-27BR 0 90 GWA-27D 8250 5496 GWA-27S 96.5 204 GWA-30D 0 2 GWA-30S 0 21 GWA-31D 0 22 GWA-31S 0 9 GWA-32D 46 8 GWA-32S 181 1 MW-01 0 0 MW-01D 0 0 MW-02 0 -16 MW-03 0 0 M W-04 727 2944 MW-05 0 28 MW-06 0 0 MW-07 647 1538 MW-104BR 0 0 MW-104BRA 0 0 Page 17 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6A COMPARISON OF OBSERVED AND SIMULATED BORON CONCENTRATIONS IN MONITORING WELLS Well Name Observed Boron (Ng/L) Computed Boron (Ng/L) MW-104D 0 0 MW-104S 0 0 MW-200BR 170 150 MW-200D 84.9 119 MW-200S 43.1 77 MW-201BR 0 0 MW-201D 0 3 MW-202BR 0 0 MW-202D 0 0 MW-202S 0 0 MW-203BR 0 0 MW-203D 0 0 MW-203S 0 0 MW-204D 0 0 MW-204S 0 0 MW2-07 10600 10159 MW2-09 455 305 OB-04 11000 11510 OB-05 0 253 OB-09 25500 9898 SFMW-1D 7250 2725 SFMW-2D 0 0 SFMW-3D 0 276 SFMW-4D 3100 1938 SFMW-5D 33 103 Notes: pg/L -.micrograms per liter Prepared by: YG Checked by: AA Page 18 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6B COMPARISON OF OBSERVED AND SIMULATED CHLORIDE CONCENTRATIONS IN MONITORING WELLS Well Observed Chloride (mg/L) Computed Chloride (mg/L) AB-01BR 350 696 AB-01BRD 96 74 AB-01D 432 697 AB-01S 460 701 AB-02BR 410 395 AB-02BRD 10 40 AB-02D 369 501 AB-02S 6 10 AB-03BR 70 134 AB-03D 280 477 AB-03S 419 545 AB-04BR 2 0 AB-04BRD 1 0 AB-04D 4 0 AB-04S 904 500 AB-04SL 9 500 AB-4SAP 4 4 AB-4 Lower Ash 17 500 AB-05D 1 0 AB-05S 446 500 AB-05SL 274 500 AB-06D 2 0 AB-06S 2 5 AB-06SL 8 3 AB-07D 5 0 AB-07S 21 0 AB-08D 17 0 AB-08S 29 500 AB-08SL 7 500 AB-09BR 4 0 AB-09BRD 10 0 AB-09D 5 0 AB-09S 6 0 BG-01 D 7 0 Page 19 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6B COMPARISON OF OBSERVED AND SIMULATED CHLORIDE CONCENTRATIONS IN MONITORING WELLS Well Observed Chloride (mg/L) Computed Chloride (mg/L) BG-02BRA 3 0 BG-02D 29 0 BG-02S 31 0 BG-03D 5 0 BG-03S 2 0 CCR-01D 29 0 CCR-01S 15 0 CCR-02D 218 259 CCR-02S 212 426 CCR-04D 370 462 CCR-04S 187 464 CCR-05D 23 651 CCR-05S 382 697 CCR-06D 365 641 CCR-06S 472 597 CCR-07D 288 146 CCR-07S 86 5 CCR-08AD 385 346 CCR-08D 388 376 CCR-08S 324 379 CCR-09D 16 2 CCR-09S 15 0 CCR-11D 16 1 CCR-11S 24 0 CCR-12D 2 0 CCR-12S 3 0 CCR-13BR 24 131 CCR-13D 15 32 CCR-13S 14 8 GWA-01BR 2 71 GWA-01 D 106 6 GWA-01S 32 14 GWA-02D 2 0 GWA-02S 2 0 GWA-03D 10 0 GWA-03S 9 0 Page 20 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6B COMPARISON OF OBSERVED AND SIMULATED CHLORIDE CONCENTRATIONS IN MONITORING WELLS Well Observed Chloride (mg/L) Computed Chloride (mg/L) GWA-06D 6 0 GWA-06S 9 0 GWA-07D 23 0 GWA-07SA 18 0 GWA-08D 6 0 GWA-08S 3 0 GWA-09BR 52 0 GWA-09D 46 0 GWA-09S 2 0 GWA-10D 27 3 GWA-10S 126 34 GWA-11D 266 192 GWA-11S 89 50 GWA-12BR 1 0 GWA-12D 1 0 GWA-12S 1 0 GWA-16BR 1 0 GWA-16D 1 0 GWA-16DA 1 0 GWA-16S 1 0 GWA-17D 1 0 GWA-17S 1 0 GWA-18D 22 16 GWA-18SA 141 43 GWA-19BR 1 23 GWA-19D 3 47 GWA-19SA 144 132 GWA-20BR 31 62 GWA-20D 393 235 GWA-20SA 377 520 GWA-21D 231 212 GWA-21S 106 55 GWA-22D 12 1 GWA-22S 2 0 GWA-23D 21 0 GWA-23S 10 0 Page 21 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6B COMPARISON OF OBSERVED AND SIMULATED CHLORIDE CONCENTRATIONS IN MONITORING WELLS Well Observed Chloride (mg/L) Computed Chloride (mg/L) GWA-24BR 2 21 GWA-24D 51 2 GWA-24S 0 1 GWA-25BR 2 0 GWA-26BR 10 0 GWA-26D 10 0 GWA-26S 6 0 GWA-27BR 18 50 GWA-27D 417 336 GWA-27S 4 23 GWA-30D 6 4 GWA-30S 4 8 GWA-31 D 3 12 GWA-31S 3 4 GWA-32D 81 7 GWA-32S 22 1 MW-01 3 0 MW-01D 8 0 MW-02 3 0 MW-03 9 0 MW-04 3 17 MW-05 2 0 MW-06 7 0 MW-07 4 4 MW-104BR 4 0 MW-104BRA 4 0 MW-104D 1 0 MW-104S 1 0 M W-200BR 62 28 MW-200D 33 22 MW-200S 11 15 MW-201BR 5 0 MW-201D 6 0 MW-202BR 4 0 MW-202D 3 0 MW-202S 2 0 Page 22 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6B COMPARISON OF OBSERVED AND SIMULATED CHLORIDE CONCENTRATIONS IN MONITORING WELLS Well Observed Chloride (mg/L) Computed Chloride (mg/L) MW-203BR 15 0 MW-203D 3 0 MW-203S 2 0 MW-204D 1 0 M W-204S 3 0 MW2-07 8 18 MW2-09 3 1 OB-04 2 449 OB-05 5 11 OB-09 10 17 SFMW-1D 13 19 SFMW-2D 9 0 SFMW-3D 7 4 SFMW-4D 9 13 SFMW-5D 9 1 Notes: mg/L - milligrams per liter Revised by: YG Checked by: AA Page 23 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6C COMPARISON OF OBSERVED AND SIMULATED TDS CONCENTRATIONS IN MONITORING WELLS Well Observed TDS (mg/L) Computed TDS (mg/L) AB-01BR 660 2972 AB-01BRD 1500 301 AB-01D 952 2975 AB-01S 1060 3004 AB-02BR 1100 1795 AB-02BRD 280 184 AB-02D 845 2490 AB-02S 90 50 AB-03BR 370 375 AB-03D 678 1195 AB-03S 1000 1362 AB-04BR 179 0 AB-04BRD 133 0 AB-04D 177 0 AB-04S 2130 1100 AB-04SL 543 1100 AB-4SAP 156 8 AB-4 Lower Ash 382 1100 AB-05D 115 0 AB-05S 1140 1100 AB-05SL 1840 1100 AB-06D 89 0 AB-06S 82 11 AB-06SL 122 4 AB-07D 86 0 AB-07S 693 0 AB-08D 93 1 AB-08S 168 1100 AB-08SL 383 1100 AB-09BR 180 0 AB-09BRD 1300 0 AB-09D 229 0 AB-09S 39 0 BG-01 D 104 0 BG-02BRA 149 0 BG-02D 150 0 BG-02S 115 0 Page 24 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6C COMPARISON OF OBSERVED AND SIMULATED TDS CONCENTRATIONS IN MONITORING WELLS Well Observed TDS (mg/L) Computed TDS (mg/L) BG-03D 65 0 BG-03S 49 0 CCR-01D 152 0 CCR-01S 37 0 CCR-02D 448 863 CCR-02S 456 1419 CCR-04D 852 1708 CCR-04S 427 1834 CCR-05D 173 2781 CCR-05S 948 2979 CCR-06D 872 2760 CCR-06S 1700 2656 CCR-07D 706 396 CCR-07S 242 13 CCR-08AD 427 995 CCR-08D 458 973 CCR-08S 438 952 CCR-09D 171 6 CCR-09S 132 0 CCR-11D 250 2 CCR-11S 367 0 CCR-12D 135 0 CCR-12S 43 0 CCR-13BR 378 437 CCR-13 D 94 108 CCR-13S 60 28 GWA-01BR 118 295 GWA-01 D 261 25 GWA-01S 79 58 GWA-02D 55 0 GWA-02S 25 0 GWA-03D 93 0 GWA-03S 88 0 GWA-06D 183 0 GWA-06S 57 0 GWA-07D 212 0 GWA-07SA 108 0 Page 25 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6C COMPARISON OF OBSERVED AND SIMULATED TDS CONCENTRATIONS IN MONITORING WELLS Well Observed TDS (mg/L) Computed TDS (mg/L) GWA-08D 131 0 GWA-08S 198 0 GWA-09BR 209 0 GWA-09D 166 0 GWA-09S 26 0 GWA-10D 202 8 GWA-10S 222 113 GWA-11D 511 640 GWA-11S 164 168 GWA-12BR 106 0 GWA-12D 58 0 GWA-12S 43 0 GWA-16BR 112 0 GWA-16D 123 0 GWA-16DA 98 0 GWA-16S 25 0 GWA-17D 107 0 GWA-17S 63 0 GWA-18D 106 55 GWA-18SA 231 142 GWA-19BR 134 77 GWA-19D 128 157 GWA-19SA 257 439 GWA-20BR 193 207 GWA-20D 868 782 GWA-20SA 883 1732 GWA-21 D 430 708 GWA-21S 191 184 GWA-22D 136 3 GWA-22S 58 0 GWA-23D 2380 0 GWA-23S 1050 0 GWA-24BR 150 88 GWA-24D 124 8 GWA-24S 105 4 GWA-25BR 134 0 GWA-26BR 113 0 Page 26 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6C COMPARISON OF OBSERVED AND SIMULATED TDS CONCENTRATIONS IN MONITORING WELLS Well Observed TDS (mg/L) Computed TDS (mg/L) GWA-26D 68 0 GWA-26S 50 0 GWA-27BR 165 165 GWA-27D 978 1121 GWA-27S 44 77 GWA-30D 125 14 GWA-30S 42 28 GWA-31 D 94 41 GWA-31S 32 13 GWA-32D 299 20 GWA-32S 123 2 MW-01 38 0 MW-01D 99 0 MW-02 71 1 MW-03 41 0 M W-04 185 994 MW-05 59 3 M W-06 74 0 M W-07 147 212 MW-104BR 720 0 MW-104BRA 171 0 MW-104D 116 0 MW-104S 46 0 MW-200BR 274 93 MW-200D 142 75 MW-200S 76 52 MW-201BR 132 0 MW-201D 90 1 MW-202BR 83 0 MW-202D 65 0 MW-202S 48 0 MW-203BR 129 0 M W-203D 94 0 MW-203S 36 0 MW-204D 33 0 M W-204S 48 0 MW2-07 920 1085 Page 27 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-6C COMPARISON OF OBSERVED AND SIMULATED TDS CONCENTRATIONS IN MONITORING WELLS Well Observed TDS (mg/L) Computed TDS (mg/L) MW2-09 212 56 OB-04 2510 1005 OB-05 27 26 OB-09 1450 811 SFMW-1D 2200 1149 SFMW-2D 70 1 SFMW-3D 143 222 SFMW-4D 690 751 SFMW-5D 110 63 Notes: mg/L - milligrams per liter Revised by: YG Checked by: AA Page 28 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-7 TRANSPORT MODEL SENSITIVITY TO KD VALUES. Well Boron (lag/L) Boron model calibrated Model, low Kd Model, high Kd NRMSE 10.20% 11.30% 12.10% AB-01BR 5920 13208 13387 10487 AB-01BRD 422 645 2139 6 AB-01D 11400 13371 13397 13016 AB-01S 13600 13421 13420 13305 AB-02BR 8870 3750 5960 123 AB-02BRD 20 75 1562 0 AB-02D 8390 5081 5104 4457 AB-02S 50 101 101 101 AB-03BR 538 602 3872 1 AB-03D 2500 8449 8752 4842 AB-03S 11800 9995 9995 9972 AB-04BR 0 0 0 0 AB-04BRD 0 0 0 0 AB-04D 87 0 0 0 AB-04S 28700 13100 13100 13100 AB-04SL 14000 13100 13100 13100 A13-4SAP 0 12 124 0 AB-4 Lower Ash 0 13100 13100 13100 AB-05D 0 0 0 0 AB-05S 12000 13100 13100 13100 AB-05SL 14100 13100 13100 13100 AB-06D 0 0 0 0 AB-06S 103 90 90 90 AB-06SL 208 18 18 18 AB-07D 0 0 0 0 AB-07S 257 0 0 0 AB-08D 0 0 9 0 AB-08S 964 13100 13100 13100 AB-08SL 6010 13100 13100 13100 AB-09BR 0 0 0 0 AB-09BRD 0 0 0 0 AB-09D 72 0 0 0 AB-09S 0 0 0 0 BG-01 D 0 0 0 0 BG-02BRA 0 0 0 0 Page 29 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-7 TRANSPORT MODEL SENSITIVITY TO KD VALUES. Well Boron (lag/L) Boron model calibrated Model, low Kd Model, high Kd BG-02D 0 0 0 0 BG-02S 0 0 0 0 BG-03D 0 0 0 0 BG-03S 0 0 0 0 CCR-01D 15 0 0 0 CCR-01S 25 0 0 0 CCR-02D 3660 1517 6299 3 CCR-02S 4600 8690 9562 4490 CCR-04D 6270 7377 9881 858 CCR-04S 5250 8305 9450 2642 CCR-05D 53 9706 12874 2222 CCR-05S 10700 13228 13369 12293 CCR-06D 10400 11699 11974 10508 CCR-06S 13300 9744 9790 8914 CCR-07D 5040 1668 2887 196 CCR-07S 67 14 103 0 CCR-08AD 9360 5117 7040 354 CCR-08D 9350 6582 6848 4675 CCR-08S 9160 6739 6913 3649 CCR-09D 72 28 42 1 CCR-09S 153 1 2 0 CCR-11D 4 -1 12 -1 CCR-11S 5 1 3 0 CCR-12D 4 0 0 0 CCR-12S 0 0 0 0 CCR-13BR 0 452 3144 0 CCR-13D 0 31 801 0 CCR-13S 0 3 218 0 GWA-01BR 0 317 1675 0 GWA-01D 12 5 149 0 GWA-01S 340 90 295 0 GWA-02D 0 0 0 0 GWA-02S 0 0 0 0 GWA-03D 0 0 0 0 GWA-03S 0 0 0 0 GWA-06D 0 0 0 0 Page 30 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-7 TRANSPORT MODEL SENSITIVITY TO KD VALUES. Well Boron (lag/L) Boron model calibrated Model, low Kd Model, high Kd GWA-06S 38 0 0 0 GWA-07D 0 0 0 0 GWA-07SA 101 0 0 0 GWA-08D 8 0 0 0 GWA-08S 365 0 0 0 GWA-09BR 176 0 0 0 GWA-09D 0 0 0 0 GWA-09S 0 0 0 0 GWA-10D 0 7 71 0 GWA-10S 518 610 763 27 GWA-11D 614 288 4913 0 GWA-11S 620 489 1154 0 GWA-12BR 0 0 0 0 GWA-12D 0 0 0 0 GWA-12S 0 0 0 0 GWA-16BR 0 0 0 0 GWA-16D 39 0 0 0 GWA-16DA 0 0 0 0 GWA-16S 0 0 0 0 GWA-17D 0 0 0 0 GWA-17S 0 0 0 0 GWA-18D 20 70 411 0 GWA-18SA 706 872 955 156 GWA-19BR 50 49 726 0 GWA-19D 50 204 1205 0 GWA-19SA 1760 2476 2971 157 GWA-20BR 34 242 1832 1 GWA-20D 9630 2584 5542 194 GWA-20SA 10200 11424 11616 7108 GWA-21D 447 801 5028 0 GWA-21S 328 457 1263 0 GWA-22D 0 12 19 0 GWA-22S 0 1 2 0 GWA-23D 8140 0 0 0 GWA-23S 2630 0 0 0 GWA-24BR 0 32 704 0 Page 31 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-7 TRANSPORT MODEL SENSITIVITY TO KD VALUES. Well Boron (lag/L) Boron model calibrated Model, low Kd Model, high Kd GWA-24D 42 7 42 0 GWA-24S 0 2 21 0 GWA-25BR 0 0 0 0 GWA-26BR 0 0 0 0 GWA-26D 0 0 0 0 GWA-26S 0 0 0 0 GWA-27BR 0 90 1675 0 GWA-27D 8250 5496 7628 84 GWA-27S 97 204 538 0 GWA-30D 0 2 118 0 GWA-30S 0 21 205 0 GWA-31D 0 22 330 0 GWA-31S 0 9 98 0 GWA-32D 46 8 365 0 GWA-32S 181 1 17 0 MW-01 0 0 0 0 MW-01D 0 0 0 0 MW-02 0 -16 15 0 MW-03 0 0 0 0 M W-04 727 2944 14472 9 MW-05 0 28 34 3 MW-06 0 0 0 0 MW-07 647 1538 2943 -125 MW-104BR 0 0 0 0 MW-104BRA 0 0 0 0 MW-104D 0 0 0 0 MW-104S 0 0 0 0 MW-200BR 170 150 721 1 MW-200D 85 119 550 1 MW-200S 43 77 373 0 MW-201BR 0 0 0 0 MW-201D 0 3 4 0 MW-202BR 0 0 0 0 MW-202D 0 0 0 0 MW-202S 0 0 0 0 MW-203BR 0 0 0 0 Page 32 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 5-7 TRANSPORT MODEL SENSITIVITY TO KD VALUES. Well Boron (Ng/L) Boron model calibrated Model, low Kd Model, high Kd MW-203D 0 0 0 0 MW-203S 0 0 0 0 MW-204D 0 0 0 0 M W-204S 0 0 0 0 MW2-07 10600 10159 14754 2232 MW2-09 455 305 781 8 OB-04 11000 11510 12069 9515 OB-05 0 253 313 137 OB-09 25500 9898 10259 2268 SFMW-1D 7250 2725 10377 50 SFMW-2D 0 0 10 0 SFMW-3D 0 276 2128 0 SFMW-4D 3100 1938 6746 26 SFMW-5D 33 1 103 607 4 Prepared by: YG Checked by: AA Notes• The calibrated model has a normalized root mean square error (NRMSE) of 10.2%. Boron concentrations are shown for the calibrated model, and for models where the Kd is increased by a factor of 5 (high Kd) and decreased by a factor of 5 (low Kd). pg/L - micrograms per liter Page 33 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, 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 ash basin 119 Direct recharge to watershed outside of ash basin 100 Decanting drain inside ash basin 174 Drainage outside of the ash basin 2.5 Flow through and under the dam 45 Notes• Gpm - gallons per minute Prepared by: YG Checked by: AA Page 34 Updated Groundwater Flow And Transport Modeling Report December 2019 Belews Creek Steam Station, Belews Creek, North Carolina TABLE 6-2 GROUNDWATER CLEAN WATER INFILTRATION AND EXTRACTION WELL DEPTHS Number of Extraction Wells Formation Total Depth (ft bgs) 4 Saprolite <30 3 Saprolite 30-59 19 TRZ/Bedrock 60-89 87 Bedrock 90-119 Number of Clean Water Infiltration Wells Formation Total Depth (ft bgs) 0 Saprolite <30 2 Saprolite 30-59 22 TRZ/Bedrock 60-89 15 Bedrock 90-119 0 Bedrock 120-149 1 Bedrock 150-179 7 Bedrock 180+ Revised by: YG Checked by: AA Number of Total Length Approximate Approximate Total Horizontal of Screen GS Elevation at Spud Spud Depth6 Simulated Recharge Wells (ft) Depth (ft BGS) Flow (gpm) 1 900 595 60 110 Prepared by: YG Checked by: AA Notes: The 113 extraction wells have an average flow rate of 0.8 gpm. The extraction wells are pumped so that the water levels are near the bottom of the wells. The 47 clean water infiltration wells wells have an average flow rate of 1.2 gpm and the heads of the injection wells are maintained at 10 feet above the ground surface. The horizontal clean water infiltration well has a head maintained at 10 feet above the ground surface as well and has a total flow rate of 110 gpm. Ft - feet Bgs - below ground surface Page 35