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Home My WebLink AboutBC_ClosureOptionsAnalysis_20181115REV 1 Belews Creek Steam Station Ash Basin Closure Options Analysis Summary Report This summary report (Report) presents the Closure Options evaluation for the ash basin located at Duke Energy Carolinas, LLC's (Duke Energy's) Belews Creek Steam Station, located in Stokes County, North Carolina. The Closure Options evaluation involved developing ash basin closure strategies and evaluating these options relative to one another to determine which option to advance to more detailed engineering and closure plan development. The strategies discussed in the Closure Options evaluation are representative of the range of possible approaches for basin closure, and do not constitute final closure plans as described in N.C. Gen. Stat. sec. 130A-309.214(a)(4). Final closure plans will be submitted in 2019, as required by law, supported by detailed engineering designs and any necessary updates to groundwater modeling and related analysis. Duke Energy developed programmatic guidance for the closure analysis effort in early 2016 to provide fleet -wide consistency to ash basin closure plan development. Duke Energy developed a relative weighting and scoring system with input from the National Ash Management Advisory Board. Using this system, Duke Energy evaluated and scored the alternatives using an options analysis framework designed to identify the best solution that balances environmental protection, cost, schedule and local community impacts. It is noted that internal working draft versions of these 2015-2016 Options Analyses for Allen, Belews Creek, Cliffside, Marshall, Mayo, and Roxboro were provided to NCDEQ at its request in May and June 2018. The 2016 internal working draft Options Analysis identified closure -in -place as the preferred solution for Belews Creek that is protective of the environment, safely closes the ash basin, minimizes the other associated risks, and was the least cost to customers. A permit -level design was developed for that option in 2016. The company then paused that work, pending determination that the site would meet the requirements for a low -risk impoundment classification pursuant to CAMA, as amended by House Bill 630. Duke Energy has completed those requirements at the Belews Creek site for a low -risk classification and now has updated this analysis. Earlier this year, a subsurface investigation was performed within the ash basin area that is normally submerged to evaluate the thickness of ash at select locations. The results of this investigation indicated that most of the areas investigated had ash thicknesses less than five feet, which is significantly less than had been previously estimated. Based on this additional information, a new hybrid closure option (designated Option 6) was developed which is a refined version of the previous hybrid (Option 2). Option 6 closes almost half the ash basin by excavation and the other half by Closure - In -Place and provides for the management of stormwater to minimize scouring of the channel and flooding impacts to downstream properties including infrastructure (road and railroad). Based on the updated ash thickness information, the northern edge of the hybrid cover was reconfigured to use a compacted ash stabilization approach which provided cost savings and reduction in uncertainty with regard to constructability. The updated Closure Options Analysis includes this new hybrid option in the analysis. Summary — Page 1 REV 1 In addition, prior alternatives that had been listed as Option 2 (Hybrid), Option 3 (Closure -By -Removal with a new landfill inside the basin footprint), and Option 5 (Closure -By -Removal to an off -site landfill) were removed from consideration from the Options Analysis for reasons of optimized design, excessive schedule/cost, and availability of on -site landfill space. SITE BACKGROUND The Belews Creek Steam Station is located in Stokes County, North Carolina along Belews Lake, a man- made lake constructed on Belews Creek in the early 1970s. Belews Creek Steam Station is a two -unit, coal-fired power generation facility that is one of the largest steam plants in the Carolinas, with a capacity of 2,240 megawatts. Belews Creek Steam Station has been in service since 1974. Belews Creek operates one impoundment for storing wet -sluiced ash, which is referred to as the Active Ash Basin (Ash Basin). In 1984, Belews Creek converted to a dry fly ash handling system, but the ability to sluice fly ash to the ash basin remained available. In accordance with the requirements in CAMA, the units were converted to a 100% dry fly ash disposal system in March 2018 and a dry bottom ash disposal system in May 2018. The most significant volume of wastewater streams placed into the ash basin is FGD wastewater. The volume of wastewater discharge to the ash basin has been reduced over the years owing to less runtime for generating units since the units are reserved to provide electricity during peak periods. The ash basin includes two embankment structures functioning as dams. These include the Ash Basin Dam situated on the north side of the ash basin and the Roadway Embankment situated on the east side of the ash basin at Pine Hall Road. The ash basin dam and roadway embankment are regulated by NCDEQ's Dam Safety Program and have been assigned the State ID STOKE-116. Figure 1 presents the ash basin and the dams. Summary— Page 2 REV 1 Figure 1. Ash Basin CLOSURE OPTIONS For the Belews Creek Steam Station, under the direction of Duke Energy, AECOM developed the following conceptual closure options that remain under evaluation: 1. Closure In -Place 4. Closure -By -Removal: Onsite Landfill Outside the Ash Basin 6. Hybrid Closure (2018) - Closure -By -Removal for areas under water and Closure In -Place for the ash delta/higher elevation portion. Reduced closure footprint within the ash basin with a stabilized ring buttress of compacted ash for stability, and downstream flood control via a retention/staging feature within the excavated portion. Option 1 consists of leaving the ash material within the ash basin, which would be capped with an infiltration barrier/cover system meeting the requirements of the Federal Coal Combustion Residuals Summary — Page 3 REV 1 (CCR) Rule and N.C. Coal Ash Management Act (CAMA). Figures A1A and A1B present the Closure -In Place concept for Option 1. Option 4 consists of excavating all ash materials from the ash basin and placing these ash materials in a new lined on -site landfill to be built within the wooded area south of and adjacent to Pine Hall Road within Duke Energy property. This 83-acre landfill would rise to 200 feet in height above current grade, be capped with an infiltration barrier/cover system meeting the requirements of the Federal CCR Rule and CAMA. Figures A4A and A413 present the closure -by -removal concept for Option 4. No siting or other studies have been performed to verify the ability to permit this location but it appears feasible based on limited review during the options development work. Option 6 is an updated version of the previous Option 2, but was developed with the insights gained from the 2018 subsurface investigation and downstream flood control needs due to pond closure. It can be considered an optimized version of Option 2. The hybrid ash closure area would be capped with an infiltration barrier/cover system meeting the requirements of the Federal CCR Rule and CAMA. Figures A6A and A613 present the Closure -In -Place concept for Option 6. Options earlier evaluated but not carried forward included: Option 2 (hybrid) — replaced by Option 6; Option 3 (closure -by -removal with new landfill in basin footprint); and Option 5 — Closure -By -Removal with off -site landfill were removed from consideration from the Options Analysis for reasons of optimized design, excessive schedule/cost, and availability of on -site landfill space. Tables 1, 2, and 3 of this report present a tabulated summary of each evaluated closure option, estimated quantities of ash and soil materials associated with each closure option, and a more detailed overview of each closure option presented. Attachment A of this report includes figures depicting conceptual -level plan drawings and cross sections/details for each closure option. The figures included in Attachment A are as follows: • Figure A1A—Option 1 Closure -In -Place Plan View • Figure A1B — Option 1 Closure -In -Place Profile and Section Views • Figure A4A — Option 4 Removal to New On -site Landfill Outside the Ash Basin Plan View • Figure A413 — Option 4 Removal to New On -site Landfill Outside the Ash Basin Profile and Section Views • Figure A6A — Option 6 Hybrid (2018) Closure Plan View • Figure A613 — Option 6 Hybrid (2018) Closure Profile and Section Views • Figure A7 — Details Attachment B includes rough order of magnitude (ROM) cost estimates for each closure option. Attachment C contains the scoring matrix which summarizes the composite scores of the various closure options, the assumptions of which are outlined in Table 3 for each particular option. Summary — Page 4 REV 1 METHODOLOGY A scoring matrix was prepared to provide consistent evaluation of closure options for each of the various site locations. This scoring evaluation tool can be found in Attachment C and considers the following primary criteria: • Environmental Protection and Impacts • Cost • Schedule • Regional Factors • Constructability Rough Order of Magnitude Costs A rough order of magnitude (ROM) Class 5 cost estimate was prepared for each of the closure options, based on information and quantities developed during the conceptual design activities. The estimated costs include construction, permitting, engineering design, post -construction O&M, and groundwater monitoring. A tabulated summary of the preliminary closure cost estimates is provided below: Current Estimates (October 2018) Option Closure Option Estimated Estimated O&M Construction Cost Cost (30 Years) 1 Closure In -Place $142,510,635 $58,546,084 4 Removal: Onsite Landfill Outside $478,050,826 $32,021,385 the Ash Basin 6 Hybrid Closure (2018) $135,236,370 $40,480,614 Option 6: Hybrid Closure (2018) option has the lowest estimated construction cost based on a reasonable balance between ash excavation volume, final cover area, and geotechnical stabilization needs compared to other options. Detailed tabulated ROM cost estimates are included in Attachment B. Schedule Within the scoring evaluation, estimates of the length of time required to initiate closure activities and the anticipated construction duration are provided for each option. For the Closure -By -Removal option (4), a substantial amount of effort is anticipated for site preparation and dewatering activities, which dictates the longer estimated initiation times. Summary — Page 5 REV 1 A major driver in the estimated construction durations is the assumed material excavation/movement of 1,000,000 CY/year; therefore, the Closure -By -Removal option has longer construction durations, due to the requirement to move all ash materials, compared to the Hybrid and Closure -In -Place options where material movement quantities are less. Another driver is the assumed capping rate of 50 acres/year for completing the closure system for the Hybrid and Closure -In -Place options. Evaluation Criteria This Options Analysis was developed as a decision -making tool to assist in selection of closure options when multiple methods are allowed under applicable regulations. The intent was to develop a decision framework that used weighted scorings to balance environmental factors, cost, and the safety of workers and the public. The Options Analysis incorporates Duke Energy's obligation as a regulated utility to ensure that its closure decisions are protective of the environment and communities, while also being prudent from a cost-effectiveness perspective. The analysis considered multiple aspects in each criterion, including surface water, groundwater, air emissions, greenfield disturbance, construction duration, imported soil needs, transportation and noise impacts, stormwater management, long-term maintenance needs and post -closure monitoring. These elements were combined to provide a weighted sum for each criterion using the following weights: environmental considerations (30%), cost (35%), schedule (15%), regional/community factors (15%) and constructability (5%.) Duke Energy placed primary emphasis on environmental factors and cost, which were approximately equal in weight. When considering all of the criteria and associated weightings, the environmental considerations have a slightly higher weight than cost with the inclusion of certain regional/community factors (transportation impact, noise impact, view impact) which are effectively environmental considerations. The scoring matrix provided in Attachment C scores each option on a scale of 0 (least favorable) to 10 (most favorable) for each of the specified criteria. The scores for each option are then summed based on specified criterion weighting, resulting in an overall weighted score for each option. The results of the scoring evaluation for the Belews Creek closure options are summarized below: Scoring Summary (October 2018) Criterion Option 1 4 6 Environmental Protection and Impacts 1.99 2.13 2.21 Cost 2.72 0.70 3.29 Schedule 1.50 0.00 1.20 Regional Factors 1.17 0.03 1.16 Constructability 0.50 0.30 0.30 Total Score 7.88 3.16 8.16 Summary — Page 6 REV 1 DISCUSSION The Options Analysis finds relatively similar rankings for environmental considerations, such as impacts to groundwater, surface water, and avoidance of greenfield disturbance. The analysis incorporates the latest groundwater modeling at Belews Creek that demonstrates groundwater near the basin responds similarly for several decades in all closure options evaluated. The current modeling does not incorporate capping or removal of other potential sources, subject to different legal requirements. If these additional areas were included, the closure would take longer, cost more, and potentially disturb more habitat. The most effective step the company can take to improve groundwater is to safely decant the free water from the ash basin, which will occur in any closure approach. In terms of duration of work and closure time (i.e., initiation time and construction duration), the Closure -In -Place option (#1) would be expected to be completed in 8.8 years and the Hybrid option (#6) in 10.3 years. The Closure -In -Place option (#1) and Hybrid option (#6) would be challenged to complete by the current CAMA deadline of 2029 unless work were to begin in early 2020. The Closure -By -Removal option (#4) would be expected to take up to 16 years and would extend beyond the current CAMA deadline of 2029 and possibly the CCR deadline of 2034. It remains in our Options Analysis despite this for full transparency of the alternative. Other aspects the company considered are regional impacts to the surrounding community related to traffic and noise generated by each of the options. Traffic to and from the site will occur through the duration for each option noted above. That will include workers, trucks for deliveries or movement of soil, topsoil, stone, geosynthetics. For the Closure -In -Place option (#1) and Hybrid option (#6) traffic will be mingled with typical traffic on the main roads leading to Belews Creek and Pine Hall Road in particular. Closure -By -Removal option (#4) requires up to 200 truck crossings per work day of Pine Hall Road over the approx. 11-year excavation period to access the new landfill. The noise generated for each the options would be similar to someone near the site, but the duration of the work and the exposure to that noise varies directly with the time required for each option and would be longer for Closure -by -Removal. Along with increased duration and truck trips comes higher levels of emissions for the Closure -by -Removal option as well. The Closure -By -Removal option is more than triple the estimated cost of the Closure -In -Place options and causes other unnecessary community impacts with little compelling environmental benefit. While long-term modeling indicates a quicker reduction in the boron plume within the immediate vicinity of the basin footprint for the Closure -By -Removal scenario, compared to the Closure -In -Place scenario, the modeled concentrations at downstream points are nearly identical for all the closure options at each evaluated point in time. Moreover, the quicker reduction is partially offset by the fact that the modeled improvement is delayed in the Closure -By -Removal scenario, compared to the Closure -In - Place scenario, due to the extended construction time. In any event, the minor change in modeled plume size, within the immediate vicinity of the basin footprint, is not enough to justify the cost of the Closure -by -Removal scenario —particularly when the impact and improvement do not materially affect neighbors or other potential receptors. The Hybrid Closure option (#6) and the Closure -In -Place option rank the highest, respectively. The Hybrid Closure option is estimated to have lower capital and O&M costs. It also removes the dam and Summary — Page 7 REV 1 brings the potential to beneficially reuse the dam material for closure. Utilizing the excavated portion of the basin footprint in this option enables retention/staging of stormwater in large rain events to provide protection of downstream features in the tributary of the Dan River. These factors combined make the Hybrid Closure (Option #6) the preferred closure option. CONCLUSION Based on the concept designs for the selected closure options and evaluation of the criteria established (environmental protection/impacts, cost, schedule, regional factors and constructability), Hybrid Closure (Option #6) was identified as the preferred option that best balance the various considerations associated with basin closure. Summary — Page 8 REV 1 Table 1 — Closure Options Summary Ash Basin Closure Options Evaluation Belews Creek Steam Station Duke Energy Description • Install stormwater controls • Install free water decanting and water treatment system • Decant free water • Perform interstitial dewatering of ash material as needed to provide stable working surfaces • Regrade ash basin waste boundary and construct closure cap. • Balance of cover material required from dam lowering and onsite borrow area. • Minimal dam removal and restore disturbed areas. • Groundwater corrective action and long-term monitoring pursuant to CAMA/CCR • Install stormwater controls. • Install free water decanting and water treatment system • Decant free water • Perform interstitial dewatering of ash material as needed to provide stable working surfaces. • Design, permit, and construct a lined landfill outside the ash basin footprint within the site property. • Excavate the ash from the basin, place in the landfill, cap using the soil from the dam (in addition to geosynthetics). • Complete dam removal and restore excavated areas to stable and non -erodible condition. • Groundwater corrective action and long term monitoring pursuant to CAMA/CCR. • Install stormwater controls • Install free water decanting and water treatment system • Decant free water • Perform interstitial dewatering of ash material as needed to provide stable working surface and removal of ash • Construct ring buttress to stabilize the slope • Excavate ash, and place excavated ash material within the Hybrid ash closure area. • Install closure cap system • Removal of dam • Groundwater corrective action and long-term monitoring pursuant to CAMA/CCR. REV 1 Table 2 — Quantity Summary Ash Basin Closure Options Evaluation Belews Creek Steam Station Duke Energy Item Volume (CY) Area (AC) 21) Surface 31) Surface Existing Ash Ash Basin Area (for engineering purposes) NA 270 NA In Place Ash 9,975,833 270 NA Ash Basin Dam 1,100,000 15 NA 1-Foot Overexcavation 435,194 270 NA Option 1: Closure in Place Closed contained ash 9,975,833 270 275 Approximate cut/fill volume 2,000,000 NA NA 1-Foot Overexcavation 0 0 NA Dam soil cut volume 360,000 NA NA 2 ft soil cover 887,333 270 275 Option 4: Onsite Landfill Outside the Excavated Ash Basin Closed contained ash 9,975,833 83 88 Ash excavation volume 9,975,833 NA NA 1-Foot Overexcavation 435,600 270 NA Landfill baseliner system (2-ft soil + synthetics) 282,981 NA 88 Landfill cover system (2-ft soil + synthetics) 282,981 NA 88 Dam soil cut volume 1,100,000 NA NA Option 6: Hybrid Option 2018 Closed contained ash 9,975,833 144 146 Ash excavation volume 2,600,000 NA NA 1-Foot Overexcavation 203,280 126 NA Ash stabilization area (cut sluiced ash and recompact ash) 1,100,000 NA NA 2 ft soil cover 471,093 NA 146 Dam soil cut volume 1,100,000 NA NA REV 1 Subject Table 3.1 — Option 1 Overview: Closure in Place Ash Basin Closure Options Evaluation Belews Creek Steam Station Duke Energy Description — Option 1 1. Install stormwater controls 2. Install free water decanting and water treatment system 3. Decant free water 4. Perform interstitial dewatering of ash material as needed to provide stable working surfaces 5. Regrade ash basin waste boundary and construct closure cap. 6. Balance of cover material required from dam lowering and onsite borrow area. 7. Minimal dam removal and restore disturbed areas. 8. Groundwater corrective action and long-term monitoring pursuant to CAMA/CCR 9. Dam remains in place following closure 1. Install stormwater run-on controls to divert stormwater from the ash basin where possible. 2. Design and install temporary water treatment system to manage decanting, interstitial dewatering, and (contact) stormwater. 3. Decanting & treatment of free water. 4. Regrade the close -in -place area to direct stormwater to the existing permitted outfall. 5. Grade the ash surface to promote positive drainage. Limited ash excavation and stacking within the ash basin are anticipated. Cut and fill volumes are expected to be balanced. Estimated total cut and fill volume is about 2.0 million cubic yards in the water covered area and ash delta. Limited dewatering of ash entrained water may be needed at certain locations to support access and future placement of the cover system. 6. Start partial removal of dam. Final volume of soil to be removed from the dam is estimated to be about 360,000 cubic yards. 7. Construct closure cap over ash basin area using soils from dam excavation and onsite borrow area. Total soil cover soil volume is estimated to be about 890,000 cubic yards based on a 2-ft thick soil cover system. The total soil cover 3-D surface area is 275 acres. Total 2-D footprint of the closure area is 270 acres. Total in place ash volume as of July 31, 2018 is 11,971,000 tons (9,975,833 cubic yards). 8. Decommission temporary wastewater treatment facility. 9. Complete minimal dam removal and tie-in with closure cap. 10. Groundwater corrective action and long term monitoring pursuant to CAMA/CCR. REV 1 Subject Description — Option 1 1. Air emissions off -site (based on miles driven) — NA 2. Air emissions on -site (based on gallons of fuel consumed) from closure implementation — this will be best option as construction work is limited. 3. Avoidance of greenfield disturbance — On -site borrow area only. 1. Capital costs = $142,510,635 2. Long-term operations maintenance and monitoring = $1,951,536 annually. 1. Initiation time (to begin ash removal) = 30 months (includes design/permitting and dewatering). 2. Design and permitting = 12 months. 3. Construction = 76 months 4. Post -closure = 30 years. 5. Total duration =106 months 1. Plan or potential for beneficial reuse of site — none. 2. Imported soil needs — Reuse partial dam removal soil. 3. CCR beneficial reuse - None 4. Transportation impact (based on miles driven) — No offsite miles. Onsite limited within ash basin footprint — minimal construction compared to other options. 5. Noise impact due to on -site activity (based on proximity of neighbors) — very little. 6. Visual impact (based on final height of storage facility, land uses within the viewshed) — better than current conditions (i.e. almost none). 1. Relative to other options, this one has easier construction. 2. No high excavations within the ash. 3. Dewatering will include free water removal and treatment and (as needed to provide a stable working surface) interstitial pore water removal and treatment as part of ash excavation and cover system placement In REV 1 Table 3.4 — Option 4 Overview: Removal - Onsite Landfill Outside the Ash Basin Ash Basin Closure Options Evaluation Belews Creek Steam Station Duke Energy Subject Description — Option 4 1. Install stormwater controls 2. Install free water decanting and water treatment system 3. Decant free water 4. Perform interstitial dewatering of ash material as needed to provide stable working surfaces 5. Construct a lined landfill outside the ash basin footprint within the site property. 6. Excavate the ash from the basin, place in the landfill, cap using the soil from the dam (in addition to geosynthetics). 7. Complete dam removal and restore excavated areas to stable and non - erodible condition. 8. Groundwater corrective action and long term monitoring pursuant to CAMA/CCR. 1. Install stormwater run-on controls to divert stormwater from the ash basin and industrial landfill areas where possible. 2. Design and install temporary water treatment system to manage decanting, interstitial dewatering, and (contact) stormwater. 3. Decanting & treatment of free water. 4. Removal & treatment of interstitial pore water in ash material as needed to provide stable working surfaces during construction within the closure -by -removal area. 5. Construct a lined landfill outside the ash basin footprint within the site property. Landfill 2D (plan -view) area is 83 acres. 6. Excavate the ash from the ash basin and haul to the landfill. Excavation volume estimated to be 9.9 million cubic yards. 7. Start partial dam removal. 8. Place ash in the landfill and cap. Total ash contained in landfill is 960,000 cubic yards (intent is to expand and contain the full amount of ash). Total soil cover soil volume is estimated to be 280,000 cubic yards based on a 2-ft thick soil cover system (in addition to geosynthetics). The total soil cover 3-D surface area is 88 acres. 9. Complete dam removal and restore excavated areas to stable and non - erodible condition. Final volume of soil to be removed from the dam is estimated to be 1,100,000 cubic yards. 10. Complete partial dam removal and tie-in with closure cap. 11. Groundwater corrective action and long term monitoring pursuant to CAMA/CCR. 1. Air emissions off -site (based on miles driven) — NA REV 1 Subject Description — Option 4 2. Air emissions on -site (based on gallons of fuel consumed) from closure implementation — this will have the most impact due to hauling needs among the onsite options. 3. Avoidance of offsite greenfield disturbance — This impacts the onsite industrial greenfield area. 1. Capital costs = $478,050,826 2. Long-term operations maintenance and monitoring = $1,067,280 annually. 3. Avoided costs — Off -site hauling ash, costs managed through minimizing material handling. 1. Initiation time (to begin ash removal) = 54 months (includes dewatering and design and permitting) 2. Design and permitting = 24 months. 3. Construction = 138 months 4. Post -closure = 30 years. 5. Total Duration = 192 months 1. Siting/permitting of new landfill (landfill location assumed to suitable but not fully studied) 2. Constructing landfill in greenfield (industrial) area near to the Belews Lake and some water supply wells. 3. Plan or potential for beneficial reuse of site — Restore to nature 4. Imported soil needs — Reuse dam removal soil. Potential additional soil needs to meet hydraulic conductivity requirements and cap landfill. 5. CCR beneficial reuse - None 6. Transportation impact (based on miles driven) — No offsite miles. Onsite hauling across Pine Hall Road 7. Noise impact due to on -site activity (based on proximity of neighbors). 8. Visual impact (based on final height of storage facility, land uses within the viewshed) — Need to consider Landfill Viewshed. 1. Relatively manageable construction option. 2. Excavation can be in layers and safe. 3. Dewatering will include free water removal and treatment and (as needed to provide a stable working surface) interstitial pore water removal and treatment as part of ash excavation and cover system placement. E. REV 1 Table 3.6 — Option 6 Overview: Hybrid Closure Option 2018 (Removal for areas under water and Closure in Place for the ash delta) - Reduced Closure Footprint Within the Ash Basin Ash Basin Closure Options Evaluation Belews Creek Steam Station Duke Energy Subject Description — Option 6 1. Install stormwater controls 2. Install free water decanting and water treatment system 3. Decant free water 4. Perform interstitial dewatering of ash material as needed to provide stable working surfaces. Install stabilized ash wedge as needed 5. Excavate the selected ash areas that were mainly under water at the start of the project, and place excavated ash material within the Hybrid ash closure area. 6. Install closure cap system 7. Removal of dam 8. Groundwater corrective action and long-term monitoring pursuant to CAMA/CCR. 1. Install stormwater run-on controls to divert stormwater from the ash basin where possible. 2. Design and install temporary water treatment system to manage decanting, interstitial dewatering, and (contact) stormwater. 3. Decanting & treatment of free water. Removal & treatment of interstitial pore water in ash material as needed to provide stable working surfaces during construction within the closure -in -place and closure -by - removal areas. Excavate and re -compact ash along the hybrid stack tie-in with hybrid in -place sluiced ash perimeter to serve as a ring buttress. 4. Excavate the selected ash areas that were mainly under water at the start of the project. Stack the excavated ash on top of the existing ash delta, away from the excavation slope initially. Excavation volume estimated to be about 2,600,000 cubic yards. 5. Construct small new perimeter berm at one location for the hybrid closure area. 6. Start dam removal. Final volume of soil to be removed from the dam is estimated to be about 1,100,000 cubic yards. 7. Grade closure area and construct closure cap using soils from dam excavation. Total cut/fill volume is estimated to be about 2,600,000 million cubic yards. Total soil cover soil volume is estimated to be 500,000 cubic yards based on a 2-ft thick soil cover system. The total soil cover 3-D surface area is 146 acres. Total 2-D (plan view) footprint of the closure area is 144 acres. Total in place ash volume as of July 31, 2018 is 11,971,000 tons (9,975,833 cubic yards). REV 1 Subject Description — Option 6 8. Complete dam removal and restore excavated areas to stable and non - erodible condition. 9. Complete I dam removal and tie-in with closure cap. 10. Groundwater corrective action and long term monitoring pursuant to CAMA/CCR. 1. Air emissions off -site (based on miles driven) — NA 2. Air emissions on -site (based on gallons of fuel consumed) from closure implementation — this will be second best option based on construction work, along with Option 5. 3. Avoidance of greenfield disturbance — On -site borrow area only. 1. Capital costs = $135,236,370 2. Long-term operations maintenance and monitoring = $1,349,354 annually. 3. Avoided costs — Off -site hauling ash, costs managed through minimizing material handling. 1. Initiation time (to begin ash removal) = 36 months (includes dewatering and design/permitting. 2. Design and permitting = 18 months. 3. Construction = 88 months 4. Post -closure = 30 years 1. Plan or potential for beneficial reuse of site — Partially restore to nature and use for hybrid closure footprint. 2. Imported soil needs — Reuse dam removal soil. 3. CCR beneficial reuse - None 4. Transportation impact (based on miles driven) — No offsite miles. Onsite limited within ash basin footprint. 5. Noise impact due to on -site activity (based on proximity of neighbors) — little to minimal. 6. Visual impact (based on final height of storage facility, land uses within the viewshed) — minimal. 1. Construction can be more challenging than Options 1 and 4. 2. High excavations within the ash and overfilling ash delta. Need stabilization. 3. Dewatering will include free water removal and treatment and (as needed to provide a stable working surface) interstitial pore water removal and treatment as part of ash excavation and cover system placement. E. 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'r �, :; -``- ' a �� `�� -` _ - `�. -� I` `,. � -\\ \ �� ` � \ _ � -- � ' � III I I Il Jk\\ � )I f1l �� II III( � �� -- J////l ME -'`v;ti, - �' `' r' ' , ' ` _ - �'_' • r�,� '�.s��'` ��,.. - - w� � - � \ \ \ , I \ �) ! / I) II (/Jn 1\ \� J %\\\ 111\ I � \� � // (�( . , � �, _ ��fi: •�; ��'; :�:;- •� �'"�'��'� � l - _ y�i i - �'-� � _; I ` \ ! / �- / / �/ �J III I J11I �\\\ \\.�/ �� \\ = // 1 I (�� 11 \\ \� 1 �. •F: y a�..!• i // r boll ON �m Ill / //l/// .yiy . . r,•r �� '�f'W;,, �'~ • �• i .ems '? , i ,� . � Q // / / / � %/ T f /d `� L � i\ �\ \ \\\\ � � 1 \ 4} /// , MM /II N 928000_ �"\vA\YII\\\ \\\ P:;..• .04 fmIIVIOA� ilkI Ill/o/�1JT DAM A. 40 . _ .rr�' •�i �' � i�, ® - \ � / � 2� - // I / / /� /III \ \\ — ' r \\\ Aw // p?JCS J)O j////I(I =x I ////i//!,�•� a�� .,� •,_ / /��liib }Y f of "/s. h••: y.'[ J,_ �, '..r •a // 'I'N 1 / i.- _= -= �� //// O �/ ��- / 1(/ I \ J // 1/ 1-- N 927000 .,,'�.;'��h.�' //./� _ - 111 --__ /w `v/ i // , II - __ �� w /;• / / / 11 I \ \ ( / \ I `� ` \ ��; / ,//%.. / / / / 1 Ill 11 I /%// 01 ASH DELTA AREA WILL \ \ — \ / / \ \ J / // / //f /// � BELEWS / .r f�\��l\\� LAKE GRADED USING A ROL HILL PATTE N / /J/ / '•i/�� I,,,, IN N 925000 J } Ij//� ,/� \\\ �i' �I /1� J•,, I � \\ l \ \ •" � �� -� �� .ter \\/ �r� 11� ' �-` 1 � 1 \ � � � \ J/� / - v — J — --tL r7 Ill, 1 I I } — / /i. / 1 ,•Il i / / /1// /I1 II 1/ s ) )JII i //r / \ \ �, =� / ~ \\\\�� I (/ / X�)(�^J/ / / \IIII \�\�l\\L1 \ \ ✓/ s J �� \ /\ \ , / //, �, \\� / / % /�/ // /„//: _=_ �� \ — - - \ ��l ✓ �, ii \J)I\\ I/1 (/ ��l\1 I��l \\\ ( III \I \\\�., I11 /• y �< /// �,\, /� 1 e\ \\�,II ILV :�k. r:. /.' l ljll /✓ /////. //��\\\\\\\ \mac---\, - _ \ �C \ \ ( I \\� Ir / J. /i%/ / .. • (Il/ ( /�i /�//• /�\\ \\�\ t i/�\�J1\c�� / •�/ ///i / �L \� \ \\�. \� (/ (� \ .—_ \ / 1 \ C PI J > ICI\\\ 11 f/ /�/ /�/ •. /r. /� > \ \ \ \ \\ \ \\ 1 �) ) > > \\ �. `\_,/ �!/�. 11 \ \ , \ / /\ .� -� � //�� , ,�i//i J I�_—.y •,— j(1 l \<•-�%s„_�,— I�llll�\ "— \� � � �-.�r\;'zyhr�ll 11 / \ \ \ \\ \ \ J / i -- \ _ / / - .. 11 \ .//i C ((� -/ "\ 'l✓ Rid:` ,;• ?', - / /, r// / PINE RO D\ } � ASH LAILL O l //�,,>„/� /_ / /�/ /� �f� /i�/ CLOSED /�/// / .. / / '�> J , �_- �) / `.J /\ \ // _--��lIz f/j STRUCTURAL \. \ I � , r /` / / �- / I \\ // i /// I Jl / / FILL 4. / I —:o �1,�';A 'p �� ll~r \ 1� _ �t-�, �.��;, // \ / l 1 i /,�� /A16. ,: - �� —�:\\\III/ .- �� =i �� ,�'�' I I 1 I J 1 I (( �� %�<l\� /�� If�1 '• 1 '`\� - �� - .' "',�!.Ji/ll _n /...J / Q' (/ j11 \ \ � �// — J/ r ) / / / � \ \� \ \\ \.�\\ `%//Ill �. ,�"'��. .., , `' ,\-- �/ // � -•l / �,PEL ' 711 /rJ�l /' ;: �. / I \ / ^�\ O � \\ •.\ ../ w'/ /i \� IIII\I Ac0 � > 00 coco k N 922Lu �,•' \\ "`/l _� _ / /\ 11 \ \/ll>�/ 1 (_//i/ // \l �', �) % \ �) !��I'' \ \�_�� I I lei \_`\�' /Iyi(r- `"�• � /. f[..ri ' �_ / ♦(` 111\ ///�n)f�/iL.. \ \ 1 %,\ ) \ \\\\ ill \ ! _//.1 It - N 928000 N 926000 N 925000 N 922000 01 IV/- . ,� r � J �..-, %;./ _ — - ' � � � I I— ! / �J l //� i 11J1 JJI � \ \\ �// \\� _,l/\ Iln�� 1 '�;4 � .� - �;.� J� I�--;./ _\\\� �� `—/�-� ��5 III IIII)1�\��111/I� ��JI IIII ��1////I/ 6V 'p A A DAM r E A Q 4t, A P A441 -i�' V\ 'Ml' P /IIIM\ dk r > J o/ )J) r tl /10 \ Ili ., � ,'�1\ � ( ///J / //( \1\_// J /\�,� \\\\\ %) �e BELEWS Wa LAKE V 7, ..'.� '; .T li�l /��% �\ i /ice/. � ��\\\ (%�-%�l�/1\ /:�1 r...I^ \ 1111= __`` /�/�� i'^� 'd. I- _j 41- J ilr U 7/1 ra; f v� I 7 �vq W!"WW \\Q 911 ON \ 77) I // Ni , J� A Z/ -71 11// P .1Cfp y 11r iA VAP -�OC� 1 mot hr - _01NE HAILI,'ROAD E) I f LL ASH LANc' Abel CLOSED% )V jj/ STRUCTURAL, FILL � or- \�� / / J, 1 1111 \ 11( ;-'- �, .- / � P / / / � %/ %/� � \ j ' � � I l /I I III I I / / / . ,- -- .� `•y LA VX L t VV 4t5 C�tmk %V W,777—, J\N uf� V_ \q MUMS, k ' 111 \I\� jam\ �\ J Jl\1, �j+} 'N \\\\\� > \� �i/////S��P .: h\ /X/411�\\ oo co Lu LLJ 0 A j I" N4 k BELEWS LAKE co 00 "J, 99-- uj uj uj uj N 929000' N 927000'i N 925000 N 924000 N 923000 WN %fit/ SPILLWAY OUTLET CONDUIT EASEMENT ACTIVE SPILLWAY RISER INTAKE STRUCTURE ' rA ijj CLOSURE BY i�• REMOVAL f ai y�� ove Rr �1, ill/< !✓�///%�%! �% � "`- <<'��' HALL ROAD\) �: ; A-� � ��\� �� f � SH LANDFILL : � a Q ,/ �irn rf i �\�k\�� - 11} "ILA <<ew �rg ``\\ b iw Amm"� /ram -� �� /��\�� J� l ,�, �� I JJ� IWC 10 Ak )A CD CD co 00 _ co _ W w w n" nN V 5 REV 0 C C E [-ll04■f• I104 18 IN MIN. STANDARD ASH BASIN CLOSURE CAP SYSTEM N.T.S GEOCOMPOSITE DRAINAGE LAYER FLEXIBLE MEMBRANE LINER (FML) 2 FT MIN. i - ALTERNATE ASH BASIN CLOSURE CAP SYSTEM N.T.S Nf)TF- EITHER STANDARD ASH BASIN CLOSURE AND CAP SYSTEM OR ALTERNATE ASH BASIN CLOSURE AND CAP SYSTEM WILL BE USED IN: • IN -PLACE CLOSURE OPTION • 2015/2016 HYBRID CLOSURE OPTION • 2018 HYBRID CLOSURE OPTION LANDFILL COVER SYSTEM WILL BE DEVELOPED BASED ON SELECTED LINER SYSTEM GEOCOMPOSITE DRAINAGE LAYER FLEXIBLE MEMBRAN LINER (FML) �`� ram■ �'�' - -�- r�r■ - - �' �r COMPACTED SOIL LAYER 2 FT MIN. (KV<1x10-7 CM/SEC) - - - - SUBGRADE \\\ EX. SUBSURFACE SOILS /\\\ \\\� 5 FT. MIN. \\\ / ORSOIL FILL SEASONAL HIGH GROUNDWATER ' STANDARD LANDFILL LINER SYSTEM GEOCOMPOSITE DRAINAGE LAYER FLEXIBLE MEMBRANE LINER (FML) NOTE: N.T.S ASH MATERIAL PREPARED SUBGRADE 1 FT MIN. GEOSYNTHETIC CLAY LINER � . (GC L) SUBGRADE EX. SUBSURFACE SOILS, 5 FT. MIN OR SOIL FILL SEASONAL HIGH GROUNDWATER ALTERNATE LANDFILL LINER SYSTEM N.T.S EITHER STANDARD LANDFILL LINER SYSTEM OR ALTERNATE LANDFILL LINER SYSTEM WILL BE USED IN: • ONSITE LANDFILL INSIDE EXCAVATED ASH BASIN • ONSITE LANDFILL OUTSIDE THE EXCAVATED ASH BASIN COVER AND LINER SYSTEM DETAILS DUKE ENERGY BELEWS CREEK ASH BASIN CLOSURE BELEWS CREEK, NORTH CAROLINA FOR BELEWS CREEK STEAM STATION DUKE SCALE: N.T.S. fi� DWG TYPE: OB 2891 vow. ENErbfm%%/® DATE: 110178/2018 _ FILENAME: FIGURE A7 com DWG SIZE DRAWING NO. DES: NP DFTR: NP CHKD : KK ENGR: KK/NP APPD : KK REVISION 0 F71 6 1 2 3 1 ITENTHS 10 20 30 ANSI D 22.0"x 34.0" FIGURE A7 1 REV 1 Attachment B REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: �CO CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule&CAMACompliant Cost Summary B SUBJECT: IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET Preliminary Promect Costs Sheets ActNeAsh Basin Close -in -Place 60432132,60572891 ACTIVITY: CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Close -in -Place Cost Estimate for CCR Surface Impoundment Option 1: Closure -in -Place Kula Kulasingam 10/24/2018 Nick Popko—ki Belews Creek Active Ash Basin -- OPTION 1: Closure -in - Place Closure & Post Closure Cost mary Close -in -Place Tasks Cost (2018 Dollars) Mobilization / Site Prep $5,246,207 Dewatering / Earthwork / Subgrade Prep. $37,043,254 Closure System Construction $23,322,024 Stormwater Management / E&S Controls / Site Restoration $46,077,023 Contingency (25%) $27,922,127 Engineering Support (Design and CQA) $2,900,000 Total Closure Cost of CCR Impoundment = $142,510,635 Post -Closure Tasks Cost (2018 Dollars) Groundwater Monitoring $14,424,990 Operations & Maintenance (O&M) $28,153,980 Contingency (25%) $10,644,743 Engineering Costs (10%) $5,322,371 Total Post -Closure of CCR Impoundment = $58,546,084 Total Closure & Post -Closure of CCR Impoundment Cost = $201,056,719 Preliminary based on information available as of 10/24/2018 10/25/2018 1 of 6 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: MX A. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule&CAMA Compliant Cost Summary B SUBJECT: IMPOUNDMENT NAME: CLOSURE METHOD: AECOMJOBNO.: CALCULATION SHEET Preliminary Promect Costs Sheets Active Ash Basin Close -in -Place 60432132,60572891 ACTIVITY: CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Close -in -Place Costs Option 1: Closure -in -Place Kula Kulasingam 10/24/18 Nick Popkowski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT (CY) 9,975,800 PERIMETER OF IMPOUNDMENT (L.F.) 20,000 MOBILIZATION/ SITE PREP DEWATERING / EARTHWORK / SUBGRADE PREP CLOSURE SYSTEM CONSTRUCTION CLOSE -IN -PLACE ESTIMATED COSTS INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COST NOTES MOBILIZATION 1 SITE PREP Mob/Demob & insurance: (1 % of Total EPC Bid Price 1 MOBILIZATION LS 1 $1,134,540 $1,134,540 includes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup). 2 ABANDON OUTLET STRUCTURES / PIPING LS 1 $994,112 $994,112 Abandon existing outlet structures and piping. 3 REMOVAL & FILTRATION OF FREE WATER MONTHS 30.0 $103,919 $3,117,555 Initiation time DEWATERING 1 EARTHWORK 1 SUBGRADE PREP 4 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 76.0 $225,832 $17,163,254 Construction time 5 RING DRAIN INSTALLATION L.F. 20,000 $58 $1,160,000 Linear feet around the proposed cap. Quantity of earthworK (cut -to -fill) using existing ash to 6 ASH REGRADING TO ESTABLISH CROWN CY 2,000,000 $9.24 $18,480,000 achieve min. 2 % slope prior to installation of closure system. Quantity calculated using AutoCAD. 7 PERIMETER DITCH / TEMP. DIVERSION BERM GRADING L.F. 20,000 $12 $240,000 Linear feet around the perimeter of impoundment. CLOSURE SYSTEM CONSTRUCTION 8 18" PROTECTIVE COVER SOIL CY 653,400 $13 $8,494,200 18 inches of common soil placed over closure by removal area (obtained off -site) 9 6" TOPSOIL CY 217,800 $13 $2,831,400 6 inches of topsoil (obtained offsite) placed over total impoundment area. 10 COMPACTED CLAY CY 0 $15 $0 Not used 11 FLEXIBLE MEMBRANE LINER (FML) SQ. FT. 11,761,200 $0.42 $4,939,704 Alternate Cap System Only: Flexible membrane liner placed over total impoundment area. 10/25/2018 2 of 6 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: JIL CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule&CAMA Compliant Cost Summary B SUBJECT: IMPOUNDMENT NAME: CLOSURE METHOD: AECOMJOBNO.: CALCULATION SHEET Preliminary Promect Costs Sheets Active Ash Basin Close -in -Place 60432132,60572891 ACTIVITY: CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Close -in -Place Costs Option 1: Closure -in -Place Kula Kulasingam 10/24/18 Nick Popkowski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) 7PERIMETER Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT (CY) 9,975,800 OF IMPOUNDMENT (L.F.) 20,000 CLOSE -IN -PLACE ESTIMATED COSTS INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COST NOTES 12 GEOCOMPOSITE DRAINAGE LAYER SQ. FT. 11,761,200 $0.60 $7,056,720 Alternate Cap System Only: Geocomposite drainage layer placed over total impoundment area. 13 GEOSYNTHETIC CLAY LINER (GCL) SQ. FT. 0 $0.72 $0 not used 10/25/2018 3 of 6 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: JIL CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule&CAMA Compliant Cost Summary B SUBJECT: IMPOUNDMENT NAME: CLOSURE METHOD: AECOMJOBNO.: CALCULATION SHEET Preliminary Promect Costs Sheets Active Ash Basin Close -in -Place 60432132,60572891 ACTIVITY: CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Close -in -Place Costs Option 1: Closure -in -Place Kula Kulasingam 10/24/18 Nick Popko—ki BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) 7PERIMETER Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT ICY) 9,975,800 OF IMPOUNDMENT (L.F.) 20,000 CLOSE -IN -PLACE ESTIMATED COSTS INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COST NOTES STORMWATER MANAGEMENT 1 E&S CONTROLS 1 SITE RESTORATION 14 EROSION AND SEDIMENT CONTROL ACRE 270 $2,000 $540,000 Assume total area to be restored will require site erosion STORMWATER and sediment control. MANAGEMENT/ E&S CONTROLS / Assume rip -rap lined stormwater conveyance channels and SITE 15 STORMWATER MANAGEMENT / CHANNELS / LET -DOWNS L.F. 60,000 $742 $44,520,000 rip rap lined let -downs off of cap. Quantity assumed at 3 RESTORATION times perimeter 16 SEED / FERTILIZE / MULCH ACRE 270 $3,767 $1,017,023 Assume total area to be restored will be mulched, fertilized, and seeded. CONTINGENCY 1 ENGINEERING SUPPORT CONTINGENCY/ ENGINEERING 17 CONTINGENCY(25%) LS 1 $27,922,127 $27,922,127 SUPPORT 18 ENGINEERING SUPPORT (DESIGN AND CQA) LS 1 $2,900,000 $2,900,000 POST -CLOSURE Annual groundwater monitoring costs for each CCR POST -CLOSURE 19 GROUNDWATER MONITORING ANNUAL 30 $480,833 $14,424,990 impoundment are based on current groundwater monitoring system Annual O&M costs are $3475/acre/yrforthe total closed 20 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $938,466 $28,153,980 area with cap. Based on Q3 2018 Post Closure Maintenance data CONTINGENCY 1 ENGINEEIING COST CONTINGENCY / ENGINEERING 21 CONTINGENCY (25%) LS 1 $10,644,743 $10,644,743 COST 22 ENGINEERING COST (10%) LS 1 $5,322,371 $5,322,371 TOTAL $201,056,719 10/25/2018 4 of 6 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: JIL CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule&CAMA Compliant Cost Summary B SUBJECT: IMPOUNDMENT NAME: CLOSURE METHOD: AECOMJOBNO.: CALCULATION SHEET Preliminary Promect Costs Sheets Active Ash Basin Close -in -Place 60482182,60572891 ACTIVITY: CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Close -in -Place Costs Option 1: Closure -in -Place Kula Kulasingam 10/24/18 Nick Popkowski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) 7PERIMETER Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT (CY) 9,975,800 OF IMPOUNDMENT (L.F.) 20,000 CLOSE -IN -PLACE ESTIMATED COSTS TASK ITEM UNIT QUANTITY INSTALLED UNIT COST IMPOUNDMENT CLOSURE COST NOTES Preliminary based on information available as of 10/24/2018 10/25/2018 5 of 6 REV 1 PROJECT PLANT NAME: CLOSURE TYPE: SHEET REV. NO. =CVMCCR A. IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule&CAMA Compliant Close -in -Place Assumptions B SUBJECT IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO. CALCULATION SHEET Preliminary Promect Costs Sheets Active Ash Basin Close -in -Place 60432132,60572891 ACTIVITY CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Close -in -Place Assumptions Option 1: Closure -in -Place Kula Kulasingam 10/24/18 Nick Popko—ki KEY ASSUMPTIONS The following key assumptions and limitations are associated with the project design, implementation and performance: 1 The cost estimates were prepared using 2018 dollars and do not include any escalation. 2 A 25% contingency has been included for this cost estimate. 3 Engineering design and CQA cost has been included for this cost estimate based on reasonable assumptions. 4 The unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience. 5 Free water removal and treatment was assumed to continue throughout the project initiation period. 6 Interstitial water treatment was assumed to continue until construction is completed. 7 Abandonment of existing structures/piping includes the demolition in -place or bulkheading of existing pipes and inlets/outlet structures, grouting of outlet pipes that extend beyond the limits of waste, and backfilling of existing structures in -place for the purposes of a close -in -place closure of an impoundment. 8 To establish the minimum top slopes of 2%, assume existing ash will be utilized to establish crown. 9 Cap cross section for the CCR impoundment will consist of flexible membrane liner, geocomposite drianage layer, and 18-inches of protective cover soil (Kv<1x10-5 cm/sec) overlain by 6-inches of topsoidin 10 Common soil for embankment and protective cover soil construction are available onsite and topsoil would come from offsite. 11 Groundwater monitoring costs are for the existing network system. Groundwater monitoring costs do not include costs incurred for any additional well installation. Maintenance costs for wells are include post-closure O&M costs. 12 O&M costs include, but are not limited to, the monitoring and maintenance/repair of the groundwater monitoring system, cap system, and storm water controls. 13 Statements of Probable Construction Cost prepared by AECOM represent AECOM's judgment as a design professional familiar with the construction industry. It is recognized, however, that neither AECOM nor the Owner has control over the cost of labor, materials or equipment nor over the contractor's methods of determining the bid price or other competitive bidding, market, or negotiating conditions. Accordingly, AECOM cannot and does not warrant or represent that proposals, bids or actual construction costs will not vary from any statement of Probable Construction Cost or other estimates or evaluations prepared by AECOM. Preliminary based on information available as of 10/24/2018 1 10/25/2018 6 of 6 REV 1 ,�cOM ' - ■ PROJECT: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY PLANT NAME: Bel —Creek CLOSURE TYPE: CCR Rule& CAMA Compliant SHEET: Cost Summary REV. NO.: B SUBJECT: IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET Preliminary Promect Costs Sheets Ash Basin Closure by Removal 60432132,60572891 ACTIVITY: CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Closure by Removal Cost Estimate for CCR Impoundment (Onsite 4- Removal and Landfill Landfill Outside the Basin) Outside Basin Kula Kulasingam 10/24/2018 Nick Popk—ski Belews Creek Active Ash Basin -- OPTION 4: Removal with Onsite Landfill Outside the Basin Closure & Post Closure Cost mary Clean -Closure Tasks Cost (2018 Dollars) Mobilization / Site Prep / Demobilization $10,402,154 Dewatering / Excavation / Convey Material $201,653,522 Onsite Landfill Construction, Disposal and Closure $150,279,145 Stormwater Management / E&S Controls / Site Restoration $16,105,840 Contingency (25%) $94,610,165 Engineering Support (Design and CQA) $5,000,000 Total Closure Cost of CCR Impoundment = $478,050,826 Post -Closure Tasks Cost (2018 Dollars) Groundwater Monitoring $14,424,990 Operations & Maintenance (O&M) $8,863,290 Contingency (25%) $5,822,070 Engineering Costs (10%) $2,911,035 Total Post -Closure of CCR Impoundment = $32,021,385 Total Closure & Post -Closure of CCR Impoundment Cost = $510,072,211 Preliminary based on information available as of 10/24/2018 10/25/2018 1 of 6 REV 1 MMCM A. PROJECT: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY PLANT NAME: Belms Creek CLOSURE TYPE: CCR Rule & CAMA Compliant SHEET: Closure -by -Removal Costs REV. NO.: B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET Preliminary Promect Costs Sheets Ash Basin Closure by Removal 60432132,60572891 ACTIVITY CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Closure by Removal Costs: Closure by Removal Cost Estimate for CCR Impoundment (Onsite 4- Removal and Landfill Landfill Outside the Basin) Outside Basin Kula Kulasingam 10/24/18 Nick Popkmski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT (CY) 9,975,800 PERIMETER OF IMPOUNDMENT (L.F.) 6,000 MOBILIZATION/ SITE PREP/ DEMOBILIZATION ACHIEVE CLOSURE -BY - REMOVAL/ CONVEY MATERIAL ONSITE LANDFILL CONSTRUCTION, DISPOSAL AND n ncl 117E CLOSURE -BY -REMOVAL ESTIMATED COSTS INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COST NOTES MOBILIZATION I SITE PREP I DEMOBILIZATION Mob/Demob & insurance: (1 % of Total EPC Bid Price) 1 MOBILIZATION / DEMOBILIZATION LS 1 $3,796,443 $3,796,443 includes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup). 2 REMOVAL OF OUTLET STRUCTURES / PIPING LS 1 $994,112 $994,112 Assume outlet structures and piping will be excavated and removed. 3 REMOVAL & FILTRATION OF FREE WATER MONTHS 54.0 $103,919 $5,611,599 Based on Initiation Time DEWATERING I EXCAVATION I CONVEY MATERIAL STEP 1: Start dewaterting for Construction time. Based 4 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 138.0 $225,832 $31,164,856 on Construction Time Step 2: Assume CCR material must be stockpiled within impoundment area to decant prior to loading. Done in 5 EXCAVATE ASH FOR CLOSURE -BY -REMOVAL / STOCKPILE ASH CY 9,975,800 $8.00 $79,806,400 conjunction with Step 1. Decant water collected and treated along with pore water from Step 1. EXCAVATE ASH FROM STOCKPILE /LOAD /HAUL ASH (DISPOSE ON- Step 3: Once material has decanted, CCRs must be 6 SITE) CY 9,975,800 $8.43 $84,095,994 excavated out of stockpile, loaded on trucks and hauled to onsite disposal site 7 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (ON -SITE) CY 871,200 $7.56 $6,586,272 Assume 2 feet of additional material to be removed over total impoundment area. 8 EXCAVATE / LOAD / HAUL CCR MATERIAL (OFF -SITE LF) CY 0 $57 $0 Only include if disposing CCRS at an off -site landfill 9 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFF -SITE LF) CY 0 $57 $0 Only include if disposing CCRS at an off -site landfill ONSITE LANDFILL CONSTRUCTION, DISPOSAL AND CLOSURE Assume landfill designed and constructed in accordance with CAMA and CCR Rules. Cost includes 10 CONSTRUCT ON -SITE LANDFILL AND ASSOCIATED COMPONENTS AC 85 $803,245 $68,275,825 landfill construction and all associated components, including: liner system, leachate management, stormwater management, access roads, closure system and all associated components,etc. 10/25/2018 2 of 6 REV 1 AM PROJECT: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY PLANT NAME: Belms Creek CLOSURE TYPE: CCR Rule &LAMA Compliant SHEET: Closure -by -Removal Costs REV. NO.: B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET PreliminarV Promect Costs Sheets Ash Basin Closure by Removal 60432132,60572891 ACTIVITY CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Closure by Removal Costs: Closure by Removal Cost Estimate for CCR Impoundment (Onsite 4- Removal and Landfill Landfill Outside the Basin) Outside Basin Kula Kulasingam 10/24/18 Nick Popkmski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT (CY) 9,975,800 PERIMETER OF IMPOUNDMENT (L.F.) 6,000 CLOSURE -BY -REMOVAL ESTIMATED COSTS INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COST NOTES yLVJVI" Place, spread and compact in thin lifts dewatered ash DISPOSE/SPREAD/COMPACT ASH AND CCR-IMPACTED MATERIALS 11 CY 10,847,000 $7.56 $82,003,320 and CCR-impacted materials excavated from closure -by FROM CLOSURE -BY -REMOVAL AREA IN ON -SITE LANDFILL removal area. 12 ON -SITE LANDFILL CLOSURE SYSTEM AC 85 $0 Included with landfill construction under line item 10 10/25/2018 3 of 6 REV 1 AM PROJECT: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY PLANT NAME: BelewsCreek CLOSURE TYPE: CCR Rule & CAMA Compliant SHEET: Closure -by -Removal Costs REV. NO.: B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET PreliminarV Promect Costs Sheets Ash Basin Closure by Removal 60432132,60572891 ACTIVITY CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Closure by Removal Costs: Closure by Removal Cost Estimate for CCR Impoundment (Onsite 4- Removal and Landfill Landfill Outside the Basin) Outside Basin Kula Kulasingam 10/24/18 Nick Popkowski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT (CY) 9,975,800 PERIMETER OF IMPOUNDMENT (L.F.) 6,000 CLOSURE -BY -REMOVAL ESTIMATED COSTS AL INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COST NOTES STORMWATER MANAGEMENT I E&S CONTROLS I SITE RESTORATION 10 PERMANENT RIPRAP STORMWATER CHANNELS L.F. 7,250 $50 $362,500 Assume If x ftwidex 1 ftthick, 145 pcf riprap n lined stormwatewater channels. STORMWATER 11 SITE EROSION AND SEDIMENT CONTROL ACRE 270 $2,000 $540,000 Assume total area to be restored will require site MANAGEMENT / erosion and sediment control. E&S CONTROLS / 12 BACKFILL AND REGRADING CY 873,000 $13.00 $11,349,000 Assume 2 feet of additional soil material (obtained SITE onsite) graded over total closure -by -removal area. RESTORATION Assume 6-inches of top soil needed (obtained offsite) 13 TOPSOIL CY 218,250 $13.00 $2,837,250 to establish vegetative stabilization over total closure -by - removal area. 14 SEED /FERTILIZE /MULCH ACRE 270 $3,767 $1,017,090 Assume total area of disturbance will be mulched, fertilized, and seeded. CONTINGENCY I ENGINEERING SUPPORT CONTINGENCY/ ENGINEERING 15 CONTINGENCY(25%) LS 1 $94,610,165 $94,610,165 SUPPORT 16 ENGINEERING SUPPORT (DESIGN AND CQA) LS 1 $5,000,000 $5,000,000 POST -CLOSURE POST -CLOSURE Annual groundwater monitoring costs for each CCR 15 GROUNDWATER MONITORING ANNUAL 30 $480,833 $14,424,990 impoundment are based on current groundwater monitoring system. Annual O&M costs are $3475/acre/yr for the total 16 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $295,443 $8,863,290 closed area with cap. Based on Q3 2018 Post Closure Maintenance data. CONTINGENCY I ENGINEERING COST CONTINGENCY/ 17 CONTINGENCY(25%) LS 1 $5,822,070 $5,822,070 ENGINEERING COST 18 ENGINEERING COST (10%) LS 1 $2,911,035 $2,911,035 10/25/2018 4 of 6 REV 1 AM PROJECT: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY PLANT NAME: Belms Creek CLOSURE TYPE: CCR Rule &LAMA Compliant SHEET: Closure -by -Removal Costs REV. NO.: B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET PreliminarV Promect Costs Sheets Ash Basin Closure by Removal 60432132,60572891 ACTIVITY CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Closure by Removal Costs: Closure by Removal Cost Estimate for CCR Impoundment (Onsite 4- Removal and Landfill Landfill Outside the Basin) Outside Basin Kula Kulasingam 10/24/18 Nick Popkmski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL AREA TO BE RESTORED (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used VOLUME OF ASH IN IMPOUNDMENT (CY) 9,975,800 PERIMETER OF IMPOUNDMENT (L.F.) 6,000 CLOSURE -BY -REMOVAL ESTIMATED COSTS TASK ITEM UNIT QUANTITY INSTALLED UNIT COST IMPOUNDMENT CLOSURE COST NOTES TOTAL $510,072,211 Preliminary based on information available as of 10/24/2018 10/25/2018 5 of 6 REV 1 a COM /� •' ■ PROJECT CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY PLANT NAME: Bel —Creek CLOSURE TYPE: CCR Rule & CAMA Compliant SHEET Closure -by -Removal Assumptions REV. NO. B SUBJECT IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO. CALCULATION SHEET Preliminary Project Costs Sheets Ash Basin Closure by Removal 60432132,60572891 ACTIVITY CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: 4 - Removal and Landfill Closure by Removal Assumptions: Outside Basin Kula Kulasingam 10/24/18 Nick Popk—ski KEY ASSUMPTIONS The following key assumptions and limitations are associated with the project design, implementation and performance: 1 The cost estimates were prepared using 2018 dollars and do not include any escalation. 2 A 25% contingency has been included for this cost estimate. 3 Engineering design and CQA cost has been included for this cost estimate based on reasonable assumptions. 4 The unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience. 5 Free water removal and treatment was assumed to continue throughout the project initiation period. 6 Removal of existing structures/piping includes the excavation and disposal of existing structures within the limits of waste and the bulkheading or grouting of existing outlet pipes that extend beyond the limits of waste. This will be performed during the Closure -by -Removal of an impoundment. 7 Interstitial water treatment was assumed to continue until construction is completed. 8 Assumed all CCR material excavated must be stockpiled in close proximity to the impoundment to be decanted. After decanting, the material will be excavated, loaded, and hauled to the on -site landfill for disposal. 9 Costs for onsite landfill construction was based on a per acre basis as provided by Duke. 10 AECOM has assumed an over -excavation of 1 foot is necessary to achieve closure -by -removal conditions. 11 Groundwater monitoring costs are for a reduced groundwater network system as compared to the existing system. Groundwater monitoring costs do not include costs incurred for any additional well installation. Maintenance costs for wells are included in post -closure O&M costs. 12 O&M costs include, but are not limited to, the maintenance/repair of the groundwater monitoring system and general maintenance of the former CCR impoundment area. 13 Statements of Probable Construction Cost prepared by URS represent URS's judgment as a design professional familiar with the construction industry. It is recognized, however, that neither AECOM nor the Owner has control over the cost of labor, materials or equipment nor over the contractor's methods of determining the bid price or other competitive bidding, market, or negotiating conditions. Accordingly, AECOM cannot and does not warrant or represent that proposals, bids or actual construction costs will not vary from any statement of Probable Construction Cost or other estimates or evaluations prepared by AECOM. Preliminary based on information available as of 10/24/2018 1 10/25/2018 6 of 6 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: 4=C CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule& CAMA Compliant Cost Summary B SUBJECT: IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET PreliminaW Promect Costs Sheets Ash Basin Hybrid 60432132,60572891 ACTIVITY: CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Hybrid 2018 Cost Estimate for CCR Impoundment Option 6-Hybrid 2018 Kula Kulasingam 10/24/2018 Nick Popko—ki Belews Creek Active Ash Basin -- OPTION 6: Hybrid Option 2018 Closure & Post Closure Cost mary Closure Tasks Cost (2018 Dollars) Mobilization / Site Prep / Demobilization $5,815,269 Dewatering / Excavation for Closure -by -Removal / Convey Material $55,894,382 Dewatering / Earthwork for Close -in -Place $24,962,248 Closure System Construction $13,092,022 Stormwater Management / E&S Controls / Site Restoration $4,825,175 Contingency (25%) $26,147,274 Engineering Support (Design and CQA) $4,500,000 Total Closure Cost of CCR Impoundment = $135,236,370 Post -Closure Tasks Cost (2018 Dollars) Groundwater Monitoring $14,424,990 Operations & Maintenance (O&M) $15,015,456 Contingency (25%) $7,360,112 Engineering Costs (10%) $3,680,056 Total Post -Closure of CCR Impoundment = $40,480,614 Total Closure & Post -Closure of CCR Impoundment Cost = $175,716,984 Preliminary based on information available as of 10/24/2018 10/25/2018 1 of 7 REV 1 10/25/2018 2 of 7 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: w— /q CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Belews Creek CCR Rule & CAMACompliant Hybrid Costs B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET Preliminary Pro'ect Costs Sheets Ash Basin Hybrid 60432132, 60572391 ACTIVITY : CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Hybrid 2018 Cost Estimate for CCR Impoundment Option 6- Hybrid 2013 KulaKulasingam 10/24/13 Nick Popkowski BASIS OF THE ESTIMATE YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL AREA TO BE RESTORED (AC) 297 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used IMPOUNDMENT AREA TO BE CLOSED -IN -PLACE (AC) 144 IMPOUNDMENTAREA TO BE CLOSED -BY -REMOVAL (AC) 126 EXISTING ASH VOLUME IN AREA TO BE CLOSED -IN -PLACE (CY) 8,959,400 TOTAL ASH VOLUME FROM CLOSURE -BY -REMOVAL (CY) 1,016,400 TOTAL (FINAL) ASH VOLUME TO BE CLOSED -IN -PLACE (CY) 9,975,800 PERIMETER OF CLOSED IN PLACE IMPOUNDMENT (L.F.) 10,000 LENGTH OF CUT -SLOPE AT CLOSE -IN -PLACE / REMOVAL INTERFACE (L.F.) 2,000 MOBILIZATION/ SITE PREP/ DEMOBILIZATION DEWATERING / EXCAVATION FOR CLOSURE -BY - REMOVAL/ CONVEY MATERIAL DEWATERING / EARTHWORK FOR CLOSE -IN -PLACE HYBRID ESTIMATED COSTS INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COST NOTES MOBILIZATION / SITE PREP / DEMOBILIZATION Mob/Demob & insurance: (1 % of Total EPC Bid Price) includes administration MOBILIZATION / DEMOBILIZATION LS 1 $1,080,091 $1,080,091 (mtgs, health & safety, trailer, ph one/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup). REMOVAL OF OUTLET STRUCTURES / PIPING LS 1 $994,112 $994,112 Assume outlet structures and piping will be excavated and removed. REMOVAL & FILTRATION OF FREE WATER MONTHS 36.0 $103,919 $3,741,066 Based on Initiation time DEWATERING/EXCAVATION FOR CLOSURE -BY -REMOVAL/ CONVEY MATERIAL REMOVAL & TREATMENT OF PORE WATER WITHIN ASH IN MONTHS 88.0 $225,832 $19,873,242 STEP 1: Start dewaterting for Construction time. Based on Construction Time CLOSURE -BY -REMOVAL AREA Step 2: Assume CCR material must be stockpiled within impoundment area to decant prior to loading. Done in conjunction with Step 1. Decant water collected EXCAVATE ASH FOR CLOSURE -BY -REMOVAL / STOCKPILE ASH CY 1,016,400 $8.00 $8,131,200 and treated along with pore water from Step 1. EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH TO CY 1,016,400 $8.43 $8,568,252 Step 3. Once material has decanted, CCRs must be excavated out of stockpile, CLOSURE -BY -REMOVAL AREA loaded on trucks and hauled to close -in -place area OVER EXCAVATE SOIL FROM CLOSURE -BY -REMOVAL AREA/ CY 203,280 $10.00 $2,032,800 Assume 1 feet of additional material to be removed over total closure by removald LOAD / HAUL CCR-IMPACTED SOIL TO CLOSE -IN -PLACE AREA impoundment area. ASH STABILIZATION BY EXCAVATING AND RECOMPACTING CY 1,111,111 $16 $17,P88,889 Ash stabilization along the stack and sluiced ash perimeter by excavating and recompacting ash. EXCAVATE / LOAD / HAUL CCR MATERIAL (OFF -SITE) CY 0 $57 $0 include if applicable EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFF -SITE) CY 0 $57 $0 include if applicable DEWATERING / EARTHWORK FOR CLOSE -IN -PLACE REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 0.0 $225,832 $0 Accounted for in closure by removal time frame. SPREAD AND COMPACT MATERIAL FROM CLOSURE -BY- CY 1,219,680 $7.56 $9,220,781 Spread dewatered ash excavated from closure -by -removal area in thin lifts over REMOVAL AREA close -in -place area. ASH REGRADING TO ESTABLISH CROWN CY 1,671,023 $9.24 $15,440,253 Quantity of earthwory (cut -to -fill) using existing ash to achieve min. 2 % slope prior to installation of closure system. Quantity calculated using AutoCAD. RING DRAIN INSTALLATION L.F. 10,000 $58 $181,215 Linear feet around the close -in -place area 10252018 3 of 7 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Belews Creek CCR Rule 8 CAMACompliant Hybrid Costs B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET Preliminary Pro'ect Costs Sheets Ash Basin Hybrid 60432132, 60572391 ACTIVITY : CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Hybrid 2018 Cost Estimate for CCR Impoundment Option 6- Hybrid 2013 KulaKulasingam 10/24/13 Nick Popkowski BASIS OF THE ESTIMATE IMF - YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL AREA TO BE RESTORED (AC) 297 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used IMPOUNDMENT AREA TO BE CLOSED -IN -PLACE (AC) 144 IMPOUNDMENTAREA TO BE CLOSED -BY -REMOVAL (AC) 126 EXISTING ASH VOLUME IN AREA TO BE CLOSED -IN -PLACE (CY) 8,959,400 TOTAL ASH VOLUME FROM CLOSURE -BY -REMOVAL (CY) 1,016,400 TOTAL (FINAL) ASH VOLUME TO BE CLOSED -IN -PLACE (CY) 9,975,800 PERIMETER OF CLOSED IN PLACE IMPOUNDMENT (L.F.) 10,000 LENGTH OF CUT -SLOPE AT CLOSE -IN -PLACE / REMOVAL INTERFACE (L.F.) 2,000 HYBRID ESTIMATED COSTS TASK ITEM UNIT QUANTITY INSTALLED UNIT COST IMPOUNDMENT CLOSURE COST NOTES PERIMETER DITCH /TEMP. DIVERSION BERM GRADING L.F. 10,000 $12 $120,000 Linear feet around the perimeter of impoundment. 10252018 4 of 7 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Belews Creek CCR Rule & CAMACompliant Hybrid Costs B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET Preliminary Pro'ect Costs Sheets Ash Basin Hybrid 60432132, 60572391 ACTIVITY : CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Hybrid 2018 Cost Estimate for CCR Impoundment Option 6- Hybrid 2013 KulaKulasingam 10/24/13 Nick Popkowski BASIS OF THE ESTIMATE IMF - YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL AREA TO BE RESTORED (AC) 297 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used IMPOUNDMENT AREA TO BE CLOSED -IN -PLACE (AC) 144 IMPOUNDMENTAREA TO BE CLOSED -BY -REMOVAL (AC) 126 EXISTING ASH VOLUME IN AREA TO BE CLOSED -IN -PLACE (CY) 8,959,400 TOTAL ASH VOLUME FROM CLOSURE -BY -REMOVAL (CY) 1,016,400 TOTAL (FINAL) ASH VOLUME TO BE CLOSED -IN -PLACE (CY) 9,975,800 PERIMETER OF CLOSED IN PLACE IMPOUNDMENT (L.F.) 10,000 LENGTH OF CUT -SLOPE AT CLOSE -IN -PLACE / REMOVAL INTERFACE (L.F.) 2,000 ::LOSURE SYSTEM CONSTRUCTION STORMWATER MANAGEMENT/ E&S CONTROLS / SITE RESTORATION CONTINGENCY/ ENGINEERING SUPPORT POST -CLOSURE HYBRID ESTIMATED COSTS TASK ITEM UNIT QUANTITY INSTALLED UNIT COST IMPOUNDMENT CLOSURE COST NOTES CLOSURE SYSTEM CONSTRUCTION 18" PROTECTIVE COVER SOIL CY 348,480 $13 $4,530,240 18 inches of common soil placed over closure by removal area (obtained off -site) 6" TOPSOIL CY 116,160 $13 $1,510,080 6 inches of topsoil (obtained offsite) placed over closure by removal area. COMPACTED LOW PERM. SOILS (Kv<1x1015 cm/sec) CY 0 $15 $0 not used. FLEXIBLE MEMBRANE LINER (FML) SQ. FT. 6,899,904 $0.42 $2,911,759 Flexible membrane liner placed over close -in -place area. Assume quantity needed is 10 %more than close -in -place area. GEOCOMPOSITE DRAINAGE LAYER SQ. FT. 6,899,904 $0.60 $4,139,942 Geocomposite drainage layer placed over close -in -place area. Assume quantity needed is 10 %more than close -in -place area. GEOSYNTHETIC CLAY LINER (GCL) SQ. FT. 0 $0.72 $0 not used. STORMWATER MANAGEMENT/ E&S CONTROLS / SITE RESTORATION PERMANENT RIPRAP STORMWATER CHANNELS Tons 7,250 $50 $362,500 Assume 10,000 If x 10 ft widex 1 ft thick, 145 pcf riprap lined stormwater channels. SITE EROSION AND SEDIMENT CONTROL ACRE 297 $2,000 $594,000 Assume total area to be restored will require site erosion and sediment control. BACKFILL AND REGRADING OF CLOSURE -BY -REMOVAL AREA CY 407,400 $3.50 $1,425,900 Assume 2 feet of additional soil material (obtained onsite) graded over total closure - by -removal area. TOPSOIL CY 101,850 $13 $1,324,050 Assume 6-inches of top soil needed (obtained offsite) to establish vegetative stabilization over total closure -by -removal area. SEED / FERTILIZE / MULCH ACRE 297 $3,767 $1,118,725 Assume total area of disturbance will be mulched, fertilized, and seeded. CONTINGENCY/ ENGINEERING SUPPORT 1 CONTINGENCY(25%) LS 1 $26,147,274 $26,147,274 2 ENGINEERING SUPPORT (DESIGN AND CQA) LS 1 $4,500,000 $4,500,000 POST -CLOSURE GROUNDWATER MONITORING ANNUAL 30 $480,833 $14,424,990 Annual groundwater monitoring costsfor each CCR impoundment are based on current groundwater monitoring system 10252018 5 of 7 REV 1 PROJECT: PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.: CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Belews Creek CCR Rule & CAMACompliant Hybrid Costs B SUBJECT: IMPOUNDMENTNAME: CLOSURE METHOD: AECOM JOB NO.: CALCULATION SHEET Preliminary Pro'ect Costs Sheets Ash Basin Hybrid 60432132, 60572391 ACTIVITY : CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Hybrid 2018 Cost Estimate for CCR Impoundment Option 6- Hybrid 2013 KulaKulasingam 10/24/13 Nick Popkowski BASIS OF THE ESTIMATE IMF - YEAR COST BASIS 2018 AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC) Not Used TOTAL IMPOUNDMENT AREA (AC) 270 AVG. DEPTH OF FREE WATER (FT) Not Used TOTAL AREA TO BE RESTORED (AC) 297 VOLUME OF FREE WATER IN IMPOUNDMENT (GAL) Not Used IMPOUNDMENT AREA TO BE CLOSED -IN -PLACE (AC) 144 IMPOUNDMENTAREA TO BE CLOSED -BY -REMOVAL (AC) 126 EXISTING ASH VOLUME IN AREA TO BE CLOSED -IN -PLACE (CY) 8,959,400 TOTAL ASH VOLUME FROM CLOSURE -BY -REMOVAL (CY) 1,016,400 TOTAL (FINAL) ASH VOLUME TO BE CLOSED -IN -PLACE (CY) 9,975,800 PERIMETER OF CLOSED IN PLACE IMPOUNDMENT (L.F.) 10,000 LENGTH OF CUT -SLOPE AT CLOSE -IN -PLACE / REMOVAL INTERFACE (L.F.) 2,000 CONTINGENCY/ ENGINEERING COST HYBRID ESTIMATED COSTS AL TASK ITEM UNIT QUANTITY INSTALLED UNIT COST IMPOUNDMENT CLOSURE COST NOTES OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $500,515 $15,015,456 Annual O&M costs are 3475.80/ac/yr for closed area with cap. Based on Q3 2018 Post Closure Maintenance data. CONTINGENCY/ ENGINEERING COST 1 CONTINGENCY(25%) LS 1 $7,360,112 $7,360,112 2 ENGINEERING COST(10%) LS 1 $3,680,056 $3,680,056 TOTAL $175,716,985 Preliminary based on information available as of 10/24/2018 10252018 6 of 7 REV 1 PROJECT PLANT NAME: CLOSURE TYPE: SHEET REV. NO. �cOM CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY Bel —Creek CCR Rule & CAMA Compliant Hybrid Assumptions B SUBJECT IMPOUNDMENT NAME: CLOSURE METHOD: CLOSUREYEAR: AECOM JOB NO. �'■ CALCULATION SHEET Preliminary Promect Costs Sheets Ash Basin Hybrid 0 60432132,60572891 ACTIVITY CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY: Cost Summary: Hybrid 2018 Cost Estimate for CCR Impoundment Option 6-Hybrid 2018 Kula Kulasingam 10/24/18 Nick Popk—ski KEY ASSUMPTIONS The following key assumptions and limitations are associated with the project design, implementation and performance: 1 The cost estimates were prepared using 2018 dollars and do not include any escalation. 2 A 25% contingency has been included for this cost estimate. 3 Engineering design and CQA cost has been included for this cost estimate based on reasonable assumptions. 4 The unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience. 5 Free water removal and treatment was assumed to continue throughout the project initiation period. 6 Interstitial water treatment was assumed to continue until construction is completed. 7 Ash to be moisture conditioned and compacted in the stack area. 8 Removal of existing structures/piping includes the excavation and disposal of existing structures within the limits of waste and the bulkheading or grouting of existing outlet pipes that extend beyond the limits of waste. This will be performed during the closure -by -removal of an impoundment. 9 AECOM has assumed all CCR material excavated must be stockpiled in close proximity to the impoundment to be decanted. After decanting, the material will be excavated, loaded, and hauled to an on -site impoundment to be closed -in -place. 10 AECOM has assumed all material excavated from areas to be closed by removal will be used for crown construction/soil regrading for closed -in -place areas. 11 AECOM has assumed an over -excavation of 1 foot is necessary to achieve closure -by -removal conditions. 12 Cap cross section for the CCR impoundment will consist of flexible membrane liner, geocomposite drianage layer, and 18-inches of protective cover soil (Kv<1x10-5 cm/sec) overlain by 6-inches of topsoil. 13 Common soil for embankment and protective cover soil construction are available onsite and topsoil would come from offsite 14 AECOM has assumed groundwater monitoring costs are for the existing network system. Groundwater monitoring costs do not include costs incurred for any additional well installation. Maintenance costs for wells are included in post -closure O&M costs. 15 O&M costs include, but are not limited to, the maintenance/repair of the groundwater monitoring system and general maintenance of the former CCR impoundment area. 16 Statements of Probable Construction Cost prepared by URS represent URS's judgment as a design professional familiar with the construction industry. It is recognized, however, that neither AECOM nor the Owner has control over the cost of labor, materials or equipment nor over the contractor's methods of determining the bid price or other competitive bidding, market, or negotiating conditions. Accordingly, AECOM cannot and does not warrant or represent that proposals, bids or actual construction costs will not vary from any statement of Probable Construction Cost or other estimates or evaluations prepared by AECOM. Preliminary based on information available as of 10/24/2018 1 10/25/2018 7 of 7 REV 1 Attachment C REV 1 Preliminary Scoring for Evaluation of Closure Options Closure Options Evaluation Worksheet Ash Basin Closure - Master Programmatic Document Duke Energy Site Name: Belews Creek Plant F= Option -Specific User Input 1 01� = Calculated Value Threshold Criteria: All closure options must comply with the following threshold criteria based on Duke Energy Guiding Principles for Ash Basin Closure 1. Provide continued geotechnical stability meeting appropriate safety factors under applicable loading conditions 2. Provide flow capacity and erosion resistance during design storm and flooding conditions 3. Effectively mitigate groundwater impacts (in conjunction with GW remediation where present) 4. Comply with applicable state and federal regulations (e.g. North Carolina Coal Ash Management Act) Option Description 1 Option 1- Closure in Place 2 Option 2 - Hybrid 2016 Closure Option - Reduced Closure Footprint Within the Ash Basin 3 Option 3 - Removal: Onsite Landfill Inside the Excavated Ash Basin 4 Option 4 - Removal: Onsite Landfill Outside the Ash Basin 5 1 Option 5 - Removal: Offsite Landfill 6 Option 6 - Hybrid 2018 Closure Option - Reduced Closure Footprint Within the Ash Basin Not carried through for further consideration. Environmental Protection and Impacts Weight: 30% Refer to 71 Modeled plume intersecting surface water Please refer to the Groundwater Sub -Scoring Document for details GW Sub -Scoring Sheet 24% 7.1% Modeled groundwater impact beyond the current Refer to Please refer to the Groundwater Sub -Scoring Document for details compliance boundary GW Sub -Scoring Sheet 24% 7.1% Refer to Modeled off -site groundwater impact Please refer to the Groundwater Sub -Scoring Document for details GW Sub -Scoring Sheet 24% 7.1% Relative rank based on visual interpretation of Refer to Please refer to the Groundwater Sub Scoring Document for details modeled boron plume GW Sub -Scoring Sheet 14% 4.1/° ° Air emissions off -site (based on miles driven off -site Interpolation. Min value hauling CCR and CCR contaminated soil) scores 10. Max value scores 0. Truck miles driven Miles 0 0 10 10 10 5% 1.5 /° ° Air emissions on -site cubic yards of Interpolation. Min value Volume of material excavation/movement scores 10. Max value scores 0. excavation/movemen t Cu.Yds 111 111 1 111 off .11 111 2,000,000 10,000,000 10 0 9 5% 1.5% Interpolation. Min valueDisturbed Avoidance of greenfield disturbance acres of scores 10. Max value scores 0. g reenfield Acres 1 1 1 30 130 8 0 10 5% ° 1.5 /° 1.99 2.13 2.21 Cost Weight: 35% Closure Cost Interpolation. Min value scores 10. Max value scores 0. Closure Cost USD 111 111 : 111 111 111 111 $ 134,000,000.00 $ 478,000,000.00 9.7 0.0 10.0 80% Operation, Maintenance and Monitoring Cost OM&M Cost USD 111 111 111 111 � 1 111 111 $ 32, 100,000.00 $ 59,000,000.00 0.0 10.0 7.0 20% 7.0% 2.72 0.70 3.29 Schedule Weight: 15% RYFIDMiT Time to move first Initiation Time Interpolation. Min value 10. Max value scores 0.Construction ash Months 30 54 10 0 87::3:07%: :4.5%scores Duration Estimated durations Months 76 138 10 0 8 1.50 0.00 1.20 REV 1 Preliminary Scoring for Evaluation of Closure Options Closure Options Evaluation Worksheet Ash Basin Closure - Master Programmatic Document Duke Energy Site Name: Belews Creek Plant = option -Specific User Input 1 = Calculated Value Regional Factors Weight: 15% Plan or potential for beneficial reuse of site Subjective Not Used For Subjective Scoring • • • 5%° ..8% Interpolation. Min value Imported soil needs scores 10. Max value scores 0. Soil Imported 115000 350000 6 0 10 5% 0.8% Interpolation. Max value IeJAIJI scores 10. Zero value scores 0. Beneficial reuse of CCR Fraction Used • 0 0 0 0 0 15% 2.3% Transportation impact (based on miles driven off- Interpolation. Min value scores 10. Max value scores 0. site hauling CCR and CCR contaminated soil) Miles Driven Miles • • 0 1 10 0 10 65% 9.8% Subjective 0 to 10: 10 is the Noise impact due to on -site activity (based on least noise; proximity of neighbors to on -site work areas) 0 is the most noise. Not Used For Subjective Scoring • 5% 0.8% Subjective 0 to 10; 10 is the View impact (based on final height of storage facility least visual; and land uses within viewshed) 0 is the most visual. • • 5% 0.7% 1.17 0.031 1.16 Constructability Weight: 5% Subjective 0 to 10: 10 is the Consider stormwater management, geotechnical, least commplicated; Not Used For Subjective Scoring and dewatering 0 is the most complicated •110F 100% 5.0% 0.50 0.30 0.30 III III III IIII Pill IIIIIIIII III III iiiiiiiiiiii III III •• • 7.88 3.16 8.16 REV 1 Criteria for Evaluation of Closure Options Closure Options Evaluation Worksheet Ash Basin Closure - Master Programmatic Document Duke Energy Threshold Criteria: All closure options must comply with the following threshold criteria based on Duke Energy Guiding Principles for Ash Basin Closure 1. Provide continued geotechnical stability under applicable loading conditions and safety factors 2. Provide flow capacity and erosion resistance during design storm and flooding conditions 3. Effectively mitigate groundwater impacts 4. Comply with applicable state and federal regulations (e.g. North Carolina Coal Ash Management Act) Category Criterion Guidance Modeled plume intersecting surface water Please refer to the Groundwater Sub -Scoring Document for details Modeled groundwater impact beyond the current compliance boundary Please refer to the Groundwater Sub -Scoring Document for details Modeled off -site groundwater impact Please refer to the Groundwater Sub -Scoring Document for details Relative rank based on visual interpretation of modeled boron plume Please refer to the Groundwater Sub -Scoring Document for details 11 Air emissions off -site (based on miles driven round-trip) Based on truck miles driven off -site for hauling CCR and CCR contaminated soil. Air emissions on -site cubic yards of excavation/movement Based on total cubic yards of cut and fill on site as a surrogate for gallons of fuel consumed. Avoidance of greenfield disturbance Refer to Scoring System and Required Input columns on scoring sheet. • Capital Cost From rough order -of -magnitude cost estimate or detailed cost estimate. Operation, Maintenance and Monitoring Cost Initiation Time From preliminary schedule for designing, permitting, bidding and constructing the option. Construction Duration Plan or potential for beneficial reuse of site Refer to Scoring System and Required Input columns on scoring sheet. Imported soil needs Refer to Scoring System and Required Input columns on scoring sheet. Beneficial reuse of CCR Refer to Scoring System and Required Input columns on scoring sheet. Transportation impact Based on truck miles driven off -site for hauling CCR and CCR contaminated soil. Noise impact due to on -site activity Based on proximity of neighbors to specific on -site work areas. View impact I Based on final height of storage facility and land uses within viewshed. • Consider stormwater management, geotechnical, and dewatering ISubjective and relative comparison to other options Environmental Groundwater Sub -scoring Worksheet Closure Options Evaluation Duke Energy INMAI • • • • • Station/Plant Name: Belews Creek Steam Station Evaluation Criteria: Criteria 1. Modeled Plume Intersecting Surface Water Score Modeled plume' does not intersect surface waters after 10 years 10 Modeled plume' does not intersect surface waters after 100 years 5 Modeled plume' does not intersect surface waters after 200 years 0 (Option 1) (Option 4) (Option 6) Closure By Removal: Onsite Landfill Outside Closure In Place Hybrid 2018 Closure Option the Ash Basin Criteria 1 Score 10 10 10 Criteria 2. Groundwater Impact Beyond the current z Compliance Boundary Score Modeled plume' is within current compliance boundary after 10 years 10 Modeled plume' is within current compliance boundary after 100 years 5 Modeled plume' is within current compliance boundary after 200 years 0 (Option 1) (Option 4) (Option 6) Closure By Removal: Onsite Landfill Outside Closure In Place Hybrid 2018 Closure Option the Ash Basin Criteria 2 Score 6 6 6 Criteria 3. Modeled Off -site Impact Score Modeled plume' does not go off -site 10 Modeled plume' is predicted to remain off -site after 100 years 5 Modeled plume' is predicted to remain off -site after 200 years 0 (Option 1) (Option 4) (Option 6) Closure By Removal: Onsite Landfill Outside Closure In Place Hybrid 2018 Closure Option the Ash Basin Criteria 3 Score 6 6 6 Criteria 4. Relative rank based on visual interpretation of modeled boron plume Score Ranked #1 among the three Closure Options based on visual interpretation of modeled boron plume 10 Ranked #2 among the three Closure Options based on visual interpretation of modeled boron plume 5 Ranked #3 among the three Closure Options based on visual interpretation of modeled boron plume 0 (Option 1) (Option 4) (Option 6) Closure By Removal: Onsite Landfill Outside Closure In Place Hybrid 2018 Closure Option the Ash Basin Criteria 4 Score 0 10 5 Environmental Groundwater Sub -scoring Worksheet Closure Options Evaluation Duke Energy Ash Basin Groundwater Sub -Scoring Document Justification Belews Creek A Ad (Option 6) (Option 1) (Option 4) Closure By Removal: Onsite Landfill Outside Justification Notes Closure In Place Hybrid 2018 Closure Option the Ash Basin Criteria 1. Modeled Plume Intersectinq Surface Based on the predictive model for the year 2050, found in the Based on the predictive model for the year 2050, found in the Based on the predictive model for the year 2050, found in the Water October 2018 Revised Groundwater Flow and Transport October 2018 Revised Groundwater Flow and Transport October 2018 Revised Groundwater Flow and Transport Modeling Report for Belews Creek Steam Station, simulated Modeling Report for Belews Creek Steam Station, simulated Modeling Report for Belews Creek Steam Station, simulated boron concentrations for the final cover scenario with natural boron concentrations for the hybrid scenario with natural boron concentrations for the excavation scenario with natural attenuation and existing extraction wells did not show boron of attenuation and existing extraction wells did not show boron of attenuation and existing extraction wells did not show boron of 4,000 ppb or greater intercepting a surface water body based on 4,000 ppb or greater intercepting a surface water body based on 4,000 ppb or greater intercepting a surface water body based on current permit status. current permit status. current permit status. Criteria 2. Groundwater Impact Beyond the 1 6 6 6 Current Compliance Boundary Based on the predictive model for the year 2050 and 2100, found Based on the predictive model for the year 2050 and 2100, found Based on the predictive model for the year 2050 and 2100, found in the October 2018 Revised Groundwater Flow and Transport in the October 2018 Revised Groundwater Flow and Transport in the October 2018 Revised Groundwater Flow and Transport Modeling Report for Belews Creek Steam Station, simulated Modeling Report for Belews Creek Steam Station, simulated Modeling Report for Belews Creek Steam Station, simulated boron concentrations for the final cover scenario with natural boron concentrations for the hybrid scenario with natural boron concentrations for the extraction scenario with natural attenuation and existing extraction wells showed boron of 4,000 attenuation and existing extraction wells showed boron of 4,000 attenuation and existing extraction wells showed boron of 4,000 ppb or greater outside of the current compliance boundary in ppb or greater outside of the current compliance boundary in ppb or greater outside of the current compliance boundary in 2050 and within the compliance boundary by 2100. Based on 2050 and within the compliance boundary by 2100. Based on 2050 and within the compliance boundary by 2100. Based on professional judgement, a score of 6 was determined to be most professional judgement, a score of 6 was determined to be most professional judgement, a score of 6 was determined to be most appropriate. appropriate. appropriate. Criteria 3. Modeled Off -site Impact 6 6 6 Based on the predictive model for the year 2050 and 2100, found Based on the predictive model for the year 2050 and 2100, found Based on the predictive model for the year 2050 and 2100, found in the October 2018 Revised Groundwater Flow and Transport in the October 2018 Revised Groundwater Flow and Transport in the October 2018 Revised Groundwater Flow and Transport Modeling Report for Belews Creek Steam Station, simulated Modeling Report for Belews Creek Steam Station, simulated Modeling Report for Belews Creek Steam Station, simulated boron concentrations for the final cover scenario with natural boron concentrations for the hybrid scenario with natural boron concentrations for the excavation scenario with natural attenuation and existing extraction wells showed boron of 4,000 attenuation and existing extraction wells showed boron of 4,000 attenuation and existing extraction wells showed boron of 4,000 ppb or greater outside of the current Duke Energy property ppb or greater outside of the current Duke Energy property ppb or greater outside of the current Duke Energy property boundary in 2050 and within the compliance boundary by 2100. boundary in 2050 and within the compliance boundary by 2100. boundary in 2050 and within the compliance boundary by 2100. Based on professional judgement, a score of 6 was determined to Based on professional judgement, a score of 6 was determined to Based on professional judgement, a score of 6 was determined to be most appropriate. be most appropriate. be most appropriate. Criteria 4. Relative rank based on visual interpretation of modeled boron plume Based on a review of boron concentrations found in the October Based on a review of boron concentrations found in the October Based on a review of boron concentrations found in the October 2018 Revised Groundwater Flow and Transport Modeling Report, 2018 Revised Groundwater Flow and Transport Modeling Report, 2018 Revised Groundwater Flow and Transport Modeling Report, this scenario is not marginally better than Option 4 Closure in this scenario is marginally better than Option 1 Closure In Place this scenario is marginally better than Option 1 Closure In Place. Place or Options 6 Hybrid Closure. and Option 6 Hybrid Closure. Notes: 1. Based on avaliable data at the time of scoring, the modeled plume considered boron at a concentration of 4,000 ug/I or greater; 4,000 µg/L does not represent a remediation goal, however this concentration does represent the EPA Tap Water Regional Screening Level (RSL) in resident tapwater for boron. 2. The current compliance boundary is the compliance boundary found in the figure "Waste and Compliance Boundaries" provided to NCDEQ on 2/15/18. REV 1