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HomeMy WebLinkAboutMarshall_ClosureOptionsAnalysis_20181115Summary – Page 1 Marshall Station Closure Ash Basin Closure Options Analysis Summary Report This summary report (Report) presents the Closure Options evaluation for the ash basin located at Duke Energy Marshall Station, located on the west bank of Lake Norman (Catawba River) at 8320 NC Highway 150, in Catawba 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 Marshall 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 N.C. Coal Ash Management Act (CAMA), as amended by House Bill 630. Duke Energy has completed those requirements at the Marshall site for a low-risk classification. SITE BACKGROUND The Marshall Steam Station began operations in 1965 as a coal-fired electric generating station and currently operates four coal-fired units. Units 1 and 2 began operation in 1965 and 1966, respectively, and originally generated nearly 350 Megawatts (MW) of electricity each. Units 3 and 4 began operation in 1969 and 1970, respectively, and originally generated approximately 648 MW each. Improvements since 1970 have increased the cumulative electric generating capacity to 2,090 MW. The Marshall Steam Station ash basin has a single impoundment regulated as a dam by the North Carolina Department of Environmental Quality (DEQ), formerly known as the Department of Environment and Natural Resources (DENR): (NCDENR ID=CATAW-054), which is shown on the Figure 1 below: Summary – Page 2 Figure 1. Marshall Steam Station Ash Basin CLOSURE OPTIONS For the Marshall Station, under the direction of Duke Energy, AECOM developed the following conceptual closure options that remain under evaluation: • Option 1: Hybrid Closure • Option 3: Closure-By-Removal (On-Site Landfill) • Option 5: Closure-In-Place Prior alternatives that had been listed as Option 2 (Hybrid Closure #2 with five fingers of the ash basin being excavated and the ash placed in the Close-In-Place Area) and Option 4 (Closure-By-Removal #2 to Summary – Page 3 off-site third-party landfill) were removed from consideration from this Options Analysis. Option 2 was removed since it would require stabilization features at five different locations at the interface of the Closure-In-Place and the excavation areas. The total combined length for the five stabilization features being approximately 3,500 linear feet compared to Option 1 Hybrid Closure requiring a stabilization feature of only 700 linear feet. Option 4 was removed since the on-site landfill can be expanded to provide the capacity for the excavated material at a much lower cost and has less off-site traffic impacts. Option 1 consists of excavating ash materials from the proposed excavation areas depicted on Figures A1A and A1B and the subsequent placement of these ash materials within the proposed consolidated Hybrid ash closure area. The Hybrid ash closure area reduces the Ash Basin footprint by approximately 184 acres and is contained within the existing ash basin footprint. A stability feature would be constructed along the transition slope below the consolidation area. Following these excavation and placement activities, the Hybrid ash closure area would be capped with an infiltration barrier/cover system meeting the requirements of the Federal Coal Combustion Residuals (CCR) Rule and N.C. Coal Ash Management Act (CAMA). Typical cover system details are shown on Figure A6. Option 1 also includes construction of a final cover meeting the requirements of the Federal CCR Rule and CAMA over the 45-acre Phase II of the 1804 Landfill (NCDEQ Permit No. 1804-INDUS) and the 84- acre Structural Fill (NCDEQ Permit No. CCB0031). Both of these inactive, permitted CCR disposal units are unlined and were closed in accordance with then applicable North Carolina regulations using a soil cover. Option 3 consists of excavating all ash materials from the proposed excavation areas depicted on Figures A3A and A3B and the subsequent placement of these materials in a new lined on-site landfill expansion to be built to the east and southeast of the existing Industrial Landfill within Duke Energy property. This 199-acre landfill expansion would rise to 175 feet in height above current grade and be capped with an infiltration barrier/cover system meeting the requirements of the Federal CCR Rule and CAMA. Figures A3A and A3B present the closure-by-removal concept for Option 3. No siting or other studies have been performed to verify the ability to permit this location but no fatal flaws were identified based on limited review during the options development work. Option 5 consists of Closure-In-Place for all of the areas depicted on Figures A5A and A5B. The closure areas would be capped with an infiltration barrier/cover system meeting the requirements of the Federal Coal Combustion Residuals (CCR) Rule and N.C. Coal Ash Management Act (CAMA). Typical cover system details are shown on Figure A6. 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: Summary – Page 4 Summary of Current Estimates Option Closure Option Estimated Construction Cost Estimated O&M Cost (30 Years) 1 Hybrid Option #1 $386,787,619 $69,295,727 3 Closure-by-Removal (On-Site Landfill) $1,067,649,043 $52,227,326 5 Closure-in-Place $207,478,232 $95,660,483 Option 5 has the lowest estimated construction cost which is primarily due to substantially-less material excavation and associated dewatering activities. 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 (Option 3), a substantial amount of effort is anticipated for site preparation and dewatering activities, which dictates the longer estimated initiation times. In terms of duration of work and closure time, the Closure-In-Place option is expected to complete in 15 years, the Hybrid option is expected to complete in 14.5 years, and the Closure-By-Removal option is expected to complete in 32.4 years. The Closure-In-Place and Hybrid options have the shorter durations but would not appear to be able to be completed before the CAMA deadline of 2029. However, the scope includes features (fill areas) not subject to CAMA. Because of the size of the basin, cover system installation of the up-gradient basin surfaces could overlap with dewatering and regrading in the downgradient portion of the basin to enable potential completion within the CAMA deadline of 2029. This does present substantial challenges to manage contact stormwater from the upgradient surfaces while the downstream cover system is in progress or in a completed state. Additional resources to increase the production rates shown below would be required to complete within the CAMA deadline. A major driver in the estimated construction durations is the assumed material excavation/movement of 1,000,000 cubic yards/year; therefore, the Closure-By-Removal option has a longer construction duration, due to the requirement to move of 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. Summary – Page 5 Evaluation Criteria This Options Analysis was developed as a decision-making tool in the selection of closure options when multiple methods are allowed under applicable regulations. The intent was to develop a decision framework that used weighted scoring 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 within each criterion, including surface water impacts, groundwater impacts, 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. The weighting of environmental considerations is slightly higher than that of cost when considering that some of the regional/community factors were effectively environmental factors as well. The scoring matrix provided in Attachment C, rates 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 Marshall closure options are summarized below: Scoring Summary Criterion Option 1 3 5 Environmental Protection and Impacts 1.83 2.34 2.80 Cost 2.64 0.70 2.80 Schedule 1.41 0.00 1.40 Regional Factors 1.16 0.03 1.20 Constructability 0.20 0.20 0.40 Total Score 7.24 3.27 8.59 Summary – Page 6 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 Marshall that demonstrates groundwater near the basin responds similarly for several decades in all closure options evaluated. 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, the Closure-In-Place option is expected to be completed in 15 years, the Hybrid option is expected to be completed in 14.5 years, and the Closure-By-Removal option is expected to be completed in 32.4 years. The Closure-In-Place option has nearly the shortest duration but would have to employ alternative means and methods and/or expanded work hours in order to meet the CAMA deadline of 2029. However, the scope includes some features (fill areas) not subject to CAMA. Because of the size of the basin, cover system installation of the upgradient basin surfaces could overlap with dewatering in the downgradient portion of the basin to potentially enable completion of the Closure-In-Place option or the Hybrid option within the CAMA deadline of 2029. 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, and geosynthetics. For all options construction-related traffic will be mingled with typical traffic on the main roads leading to or accessing the Marshall site. This would include Highway 150, Sherrills Ford Road, and Island Point Road. At Marshall, the active on-site landfill is located within the Station limits so transportation of ash using a public roadway is not required for the Closure-By- Removal option. 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 as described above. The viewshed for work related to the closure of the ash basin would be predominantly from Sherrills Ford Road and Island Point Road. The most visible feature would be the landfill during and after the Hybrid or Closure-by-Removal options. The new landfill would be a prominent feature along Island Point Road, rising to the same height as the current 1804 Phase II landfill under the Hybrid option, and rising to 50 feet higher than the 1804 Phase II landfill under the Closure- by-Removal option. The Closure-By-Removal is five times the estimated cost of the Closure-In-Place option and causes other unnecessary community impacts with little environmental benefit. Based on the results to date and the preliminary groundwater model, all three scenarios, Closure-By-Removal, Closure-In-Place, and the Hybrid option, show similar concentrations of boron in 100 years. The Closure-by-Removal option takes substantially longer to implement and therefore delays improvement to the groundwater. The 2050 groundwater predictive model shows slightly higher concentrations within the footprint of the basin for the Hybrid option when compared to the Closure-In-Place option. Summary – Page 7 CONCLUSION Based on the conceptual designs for the selected closure options and evaluation of the criteria established (environmental protection/impacts, cost, schedule, regional factors, and constructability), Closure-In-Place option (#5) or the Hybrid option (#1) were identified as the preferred options that best balance the various considerations associated with basin closure. Attachments: A – Closure Options Figures B – Closure Options Cost Estimates C – Closure Options Scoring Matrix and Groundwater Sub-Scoring Worksheet Table 1 – Closure Options Summary Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy Option Description Option #1 – Hybrid Closure • Install stormwater controls. • Install free water removal and water treatment system. • Decant free water. • Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. • Install deep mixing method wall or stabilized soil wedge as needed. • Excavate ash, and place excavated ash material within the Hybrid ash closure area. • Remove one foot of residual soil in the ash excavation areas. • Regrade Closure-in-Place areas as needed to establish final cover grades. This includes ash basin finger areas, the 1804 Phase II Landfill, and the Structural Fill. • Install closure cover system over Hybrid consolidated ash closure area as well as the Closure-in-Place areas. • Partial dam removal and restore disturbed areas. • Groundwater corrective action and long-term monitoring pursuant to CAMA. Option #3 – Closure- by-Removal (On-Site Landfill) • Install stormwater controls. • Install free water removal and water treatment systems. • Decant free water. • Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. • Excavate ash and one foot of residual soil within the footprint of the future permitted Industrial Landfill footprint (see Figure A3A) which includes portions of the Industrial Landfill and the ash basin finger areas beneath and the 1804 Phase II landfill and the ash basin fingers beneath. Stockpile all material within the designated, on-site staging area until the new landfill expansion can be constructed and permitted. • Construct and permit the new expanded Industrial Landfill • Excavate remaining ash material from the ash basin, 1804 Phase I Landfill, and the Structural Fill areas and the ash basin fingers beneath. • Place and compact excavated ash material within the newly constructed and expanded Industrial Landfill, and install cover system. • Partially remove Dam, regrade Closure-by-Removal area, and restore disturbed areas. • Groundwater corrective action and long-term monitoring pursuant to CAMA. Table 1 – Closure Options Summary Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy Option Description Option #5 – Closure-in- Place • Install stormwater controls. • Install free water removal and water treatment systems. • Decant free water. • Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. • Regrade ash basin, 1804 Landfill (Phases I and II), and the Structural Fill as needed to establish final cover grades, and construct closure cover system. • Restore disturbed areas. • Groundwater corrective action and long-term monitoring pursuant to CAMA. Table 2 – Quantity Summary Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy Item Tons Volume (CY) Area (Ac) Existing Ash Ash Basin – Ash 16,832,000 14,026,700 360 1804 Ash Landfill (Phase I) – Ash 626,400 522,000 13 1804 Ash Landfill (Phase II) – Ash 4,876,800 4,064,000 45 Structural Fill – Ash 6,492,000 5,410,000 84 Existing Ash Total 28,827,200 24,022,700 502 Option 1 (Hybrid Closure) Hybrid Closure Area (Ash to Remain in Place) 28,827,200 15,892,700 318 Closure-by-Removal (Includes 1-ft Over Excavation) N/A* 8,426,853 184 Option 1 Total N/A* 24,319,553 502 Option 3 (Closure-by-Removal – On-Site Landfill) Closure-by-Removal (Includes 1-ft Over Excavation) N/A* 24,832,593 502 Option 5 (Closure-in-Place) Closure-in-Place 28,827,200 24,022,700 502 Ash Regrading 3,288,000 2,740,000 N/A Available On-Site Soil Dam Soil Volume (Option 1 and 3) N/A* 600,000 N/A On-Site Soil Borrow Area (As Needed) N/A* TBD TBD Soil Needed Option 1 (Hybrid Closure) Hybrid Closure Area Cap System (1.5-ft) N/A* 251,680 104 Hybrid Closure Area Cap System Topsoil (0.5-ft) N/A* 83,893 104 Closure-in-Place Area Cap System (1.5-ft) N/A* 517,880 214 Closure-in-Place Area Cap System Topsoil (0.5-ft) N/A* 172,627 214 Closure-by-Removal Area Regrading (1.5-ft) N/A* 445,280 184 Closure-by-Removal Area Regrading Topsoil (0.5-ft) N/A* 148,427 184 Option 1 Total Soil Needed N/A* 1,619,787 N/A Option 3 (Closure-by-Removal – On-Site Landfill) New Phases of the Industrial Landfill Subgrade N/A* 1,870,000 199 New Phases of the Industrial Landfill Area Cap System (1.5-ft) N/A* 481,580 199 New Phases of the Industrial Landfill Area Cap System Topsoil (0.5-ft) N/A* 160,527 199 Closure-by-Removal Area Backfill/Regrading (1.5-ft) N/A* 767,140 317 Closure-by-Removal Area Backfill/Regrading Topsoil (0.5-ft) N/A* 255,713 317 Option 3 Total Soil Needed N/A* 3,534,960 N/A Option 5 (Closure-in-Place) Closure-in-Place Cap System (1.5-ft) N/A* 1,214,840 502 Closure-in-Place Cap System Topsoil (0.5-ft) N/A* 404,947 502 Option 5 Total Soil Needed N/A* 1,619,787 N/A * Not calculated due to not having a defined conversion rate for over excavated and/or borrow soil. Table 2 – Quantity Summary Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy Table 3.1 - Option 1 Overview: Hybrid Closure Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy 1 Subject Description Description 1. Install stormwater controls. 2. Install free water removal and water treatment system. 3. Decant free water. 4. Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. 5. Install deep mixing method wall or stabilized soil wedge as needed. 6. Excavate ash, and place excavated ash material within the Hybrid ash closure area. 7. Regrade areas as needed to establish final cover grades. This includes ash basin finger areas, the 1804 Phase II Landfill, and the Structural Fill. 8. Install closure cover system over Hybrid consolidated ash closure area as well as the ash basin finger areas, the 1804 Phase II Landfill, and the Structural Fill. 9. Partial dam removal and restore disturbed areas. 10. Groundwater corrective action and long-term monitoring pursuant to CAMA. Details 1. Install run-on controls to divert and manage non-contact stormwater 2. Design and install temporary free water decanting and water treatment system to manage dewatering activities and contact stormwater. 3. Decanting and treatment of free water. 4. Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. 5. Construct a deep mixing method (DMM) wall or stabilized soil wedge to stabilize the slope at the Hybrid interface. Feature will be approximately 700 feet wide across the basin. 6. Excavate an estimated 8,130,000 cy of ash material from within the closure-by-removal area, and place the excavated ash material within the Hybrid ash closure area. 7. Excavate an estimated 296,853 cy of residual soil material (1 foot below ash) from the Closure-by-Removal areas, and place the excavated material within the Hybrid ash closure area (total estimated excavation = 8,426,853 cy). 8. Regrade ash basin finger areas, the 1804 Phase II Landfill, and the Structural Fill as needed to establish final cover grades. 9. Install closure cover system over the Hybrid ash closure area as well as the ash basin finger areas, the 1804 Phase II Landfill, and the Structural Fill. Estimated as 318 acres. 10. Complete partial dam removal and tie-in with closure cover system. 11. Restore areas disturbed during closure. 12. Groundwater corrective action and long term monitoring pursuant to CAMA. Table 3.1 - Option 1 Overview: Hybrid Closure Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy 2 Subject Description Environmental Protection and Impacts 1. Air emissions off-site (based on miles removing ash from Marshall site) – N/A (not driving off-site). 2. Air emissions on-site (based on gallons of fuel consumed) from closure implementation – this will be second best option (mid-range consumption) based on construction work and duration 3. Greenfield disturbance - On-site borrow area only. Potential for off-site topsoil soil borrow area. Cost 1. Capital costs ≈ $386,787,619. 2. Long-term O&M and monitoring ≈ $2,309,858 annually. Schedule 1. Initiation time (to begin ash removal) = 36 months (includes dewatering and design/permitting, and is a function of the stabilized soil feature construction). 2. Design and permitting = 24 months. 3. Construction = 138 months. 4. Total closure duration = 174 months or 14.5 years for the entire 318 acres. Potential for the 179 acres over the consolidated ash basin surface to be completed earlier but management of contact water on upstream portions becomes significant challenge. This would extend beyond CAMA deadline and potentially the CCR deadline. 5. Post-closure = 30 years. Regional Factors 1. Plan or potential for beneficial reuse of site – None. 2. Imported soil needs – cover and grading soil assumed to come from on- site sources. Topsoil assumed to be from off-site sources. 3. CCR beneficial reuse – None. 4. Transportation impact (based on miles driven) - N/A (ash is not being driven off-site). 5. Noise impact due to on-site activity (based on proximity of neighbors) - Construction noise level approximately equivalent for each option, therefore scoring is based on construction duration. 6. There will be line-of-site visual on final stages of construction based on height of Hybrid design, as well as potential grading and borrow activities in the viewshed. Final height of Hybrid ash closure area will be equivalent to the 1804 Phase II Landfill. Top elevation of 925 feet. Constructability 1. High internal slopes within the basin at the Hybrid transition will require a stabilization feature. 2. Dewatering will include free water decanting and treatment as needed to provide a stable working surface. Interstitial pore water removal and treatment will be needed as part of ash excavation and cover system grading and placement. Table 3.3 - Option 3 Overview: Closure-by-Removal - On-Site Landfill (Extension of Industrial Landfill) Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy 1 Subject Description Description 1. Install stormwater controls. 2. Install free water decanting and water treatment systems. 3. Decant free water. 4. Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. 5. Excavate and move ash to develop subgrade for new Industrial Landfill expansion. 6. Construct and permit the new and expanded Industrial Landfill (see Figure A3A). 7. Excavate remaining ash material from the ash basin, 1804 Phase I Landfill, and the Structural Fill areas and the ash basin fingers beneath. 8. Place and compact excavated ash material within the newly constructed and expanded Industrial Landfill, and install cover system. 9. Partially remove Dam, regrade Closure-by-Removal areas for positive drainage, and restore disturbed areas. 10. Groundwater corrective action and long-term monitoring pursuant to CAMA. Details 1. Install stormwater run-on controls to divert stormwater from the ash basin and Industrial Landfill areas where possible. 2. Design and install temporary free water decanting and water treatment system to manage dewatering activities and influent (contact) stormwater. 3. Decanting and treatment of free water. 4. Perform interstitial dewatering of ash material to provide safe and stable working surfaces. 5. Excavate ash and 1 foot of residual soil within the footprint of the future permitted Industrial Landfill (see Figure A3A) which includes portions of the Industrial Landfill and the ash basin finger areas beneath and the 1804 Phase II landfill and the ash basin fingers beneath. Stockpile all material within the designated, on-site staging area until the new landfill expansion can be constructed and permitted. 6. Construct the new and expanded Industrial Landfill. The expansion area of the Industrial Landfill is 199 acres. 7. Place and compact the previously excavated material within the newly constructed Industrial Landfill. 8. Excavate remaining ash material from the ash basin, 1804 Phase I Landfill, and the Structural Fill areas and the ash basin fingers beneath, place and compact it in the newly constructed expanded Industrial Landfill. Previously-removed ash in the staging area is also removed to be placed and compacted it in the newly constructed expanded Table 3.3 - Option 3 Overview: Closure-by-Removal - On-Site Landfill (Extension of Industrial Landfill) Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy 2 Subject Description Industrial Landfill. Total excavated and removed ash is estimated as 24,022,700 cy. 9. Excavate the residual soil material (1 foot below ash) from the Closure- by-Removal areas, place and compact it in the newly constructed expanded Industrial Landfill. Total residual soil estimated as 809,893 cy. 10. Install landfill cover system over the Industrial Landfill expansion. Portion of the landfill remains open to support on-going generation. 11. Complete partial dam removal and tie-in with closure cover system. 12. Restore areas disturbed during closure. 13. Groundwater corrective action and long-term monitoring pursuant to CAMA. Environmental Protection and Impacts 1. Air emissions off-site (based on miles driven round-trip hauling CCR and CCR contaminated soil) = N/A (not driving off-site). 2. Air emissions on-site (based on gallons of fuel consumed) from closure implementation – this will be the highest consumption based on construction work and duration 3. Greenfield disturbance = On-site borrow area and Industrial Landfill expansion area. Potential for off-site topsoil soil borrow area. Cost 1. Capital costs = $1,067,649,043 2. Long-term operations, maintenance, and monitoring= $1,740,911 annually. (includes the new phases of the Industrial Landfill). Schedule 1. Initiation time (to begin ash removal) = 54 months (includes dewatering, design/permitting, landfill construction, etc.). 2. Design and permitting = 48 months. 3. Construction = 335 months. 4. Total duration = 389 months or 32.4 years. Well beyond CAMA and CCR dates 5. Post-closure = 30 years. Regional Factors 1. Permitting for expanded landfill required. 2. Constructing expanded landfill in greenfield (industrial) area. 3. Plan or potential for beneficial reuse of site - None. 4. Imported soil needs – cover and grading soil assumed to come from on-site sources. Topsoil assumed to be from off-site sources and would be trucked in. 5. CCR beneficial reuse - None. 6. Transportation impact (based on miles driven) - N/A (ash is not being driven off-site). 7. Noise impact due to on-site activity (based on proximity of neighbors) - Construction noise level approximately equivalent for each option, Table 3.3 - Option 3 Overview: Closure-by-Removal - On-Site Landfill (Extension of Industrial Landfill) Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy 3 Subject Description therefore scoring is based on construction duration. 8. There will be line-of-site visual on final stages of construction based on height of expanded Industrial Landfill design, as well as potential grading and borrow activities in the viewshed. Final height of Industrial landfill will be an elevation of 970 feet. This is 50 feet higher than the current 1804 Phase II Landfill. Constructability 1. Development of the Industrial Landfill requires considerable movement and staging of ash and soil before construction can begin. 2. Ash excavation and active construction site over an lengthy period. Table 3.5 - Option 5 Overview: Closure-in-Place Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy 1 Subject Description Description 1. Install stormwater controls. 2. Install free water decanting and water treatment systems. 3. Decant free water. 4. Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. 5. Regrade ash basin, 1804 Phase I and II Landfills, and Structural Fill, as needed to establish final cover grades, and construct closure cover system. 6. Restore disturbed areas. 7. Groundwater corrective action and long-term monitoring pursuant to CAMA. 8. Dam remains in place following closure. Details 1. Install stormwater run-on controls to divert and manage non-contact stormwater 2. Design and install temporary free water removal and water treatment system to manage dewatering activities and influent (contact) stormwater. 3. Decanting and treatment of free water. 4. Perform interstitial dewatering of ash material as needed to provide safe and stable working surfaces. 5. Regrade the ash basin, 1804 Phase I and II Landfills, and the Structural Fill for positive drainage. Cut and fill volumes of ash are expected to be balanced. Estimated ash movement to develop grading is approximately 2,700,000 cy. 6. Install closure cover system over the ash basin, 1804 Phase I and II Landfills, and the Structural Fill. Total cover system is estimated as 502 acres. 7. Restore areas disturbed during closure. 8. Groundwater corrective action and long term monitoring pursuant to CAMA. Environmental Protection and Impacts 1. Air emissions off-site (based on miles driven off-site hauling CCR and CCR contaminated soil) - N/A. 2. Air emissions on-site (based on gallons of fuel consumed) from closure implementation – this will be the lowest consumption based on construction work and duration 3. Greenfield disturbance - On-site borrow area only. Potential for off-site topsoil soil borrow area. Cost 1. Capital costs = $207,478,232 2. Long-term operations, maintenance, and monitoring = $3,188,683 annually. Table 3.5 - Option 5 Overview: Closure-in-Place Ash Basin Closure Options Evaluation Marshall Steam Station Duke Energy 2 Subject Description Schedule 1. Initiation time (to begin ash removal) = 30 months (includes design, permitting, dewatering, etc.). 2. Design and permitting = 18 to 24 months. 3. Construction = 150 months for the entire 502 acres. Potential for the 360 acres over the ash basin to be completed earlier but management of contact water on upstream portions becomes significant challenge. 4. Total duration = 180 months or 15 years. This would extend beyond CAMA deadline and potentially the CCR deadline. 5. Post-closure = 30 years. Regional Factors 1. Plan or potential for beneficial reuse of site - None. 2. Imported soil needs – cover and grading soil assumed to come from on-site sources. Topsoil assumed to be from off-site sources and would be trucked in. 3. CCR beneficial reuse – None. 4. Transportation impact (based on miles removing ash from Marshall site) - N/A (not driving off-site). 5. Noise impact due to on-site activity (based on proximity of neighbors) - Construction noise level approximately equivalent for each option, therefore scoring is based on construction duration. 6. There will be minimal line-of-site visual on construction activities, limited to potential grading and borrow activities in the viewshed. – equivalent to current conditions. Constructability 1. Stormwater management within basin represents challenges for diverting, staging, and segregating contact and non-contact water. Attachment A INDUSTRIAL LANDFILLPERMIT NO. 1812(INCLUDING FUTUREPHASES 1 THROUGH 5)T R A N SM I S S I O N L I N E C O R R I D O R TRANSMISSION LINECORRIDORFGD LANDFILLPERMIT NO. 1809TRANSMISSIONLINE CORRIDORASBESTOS LANDFILLPERMIT NO. 1804DEMOLITION LANDFILLPERMIT NO. 1804PROPOSED STORMWATER PONDFREE WATER SURFACE LEVEL = 7601""1234102030TENTHS0DWG SIZEREVISIONFORDRAWING NO.FILENAME:DWG TYPE:JOB NO:DATE:SCALE:DES:DFTR:CHKD:ENGR:APPD:2345786A22.0"x34.0"ANSI DSEAL123ABBCD78623456cDUKE ENERGYCLOSURE OPTIONS EVALUATIONCATAWBA COUNTY, NORTH CAROLINAMARSHALL STEAM STATION6057284911/02/2018CCCNOT FOR CONSTRUCTIONDRAFTAS SHOWN050010001500 (IN FEET)GRAPHIC SCALECLOSURE OPTION #1HYBRID CLOSURE #1 - PLAN VIEWA1AMSRMSRJBRJBRJBHYBRID CLOSURE #1 - PLAN VIEW56 102030TENTHS0DWG SIZEREVISIONFORDRAWING NO.FILENAME:DWG TYPE:JOB NO:DATE:SCALE:DES:DFTR:CHKD:ENGR:APPD:2345786A22.0"x34.0"ANSI DSEAL123ABBCD78623456cDUKE ENERGYCLOSURE OPTIONS EVALUATIONCATAWBA COUNTY, NORTH CAROLINAMARSHALL STEAM STATION6057284911/02/2018CCCNOT FOR CONSTRUCTIONDRAFTAS SHOWNCLOSURE OPTION #1HYBRID CLOSURE #1 - PROFILE VIEWA1BMSRMSRJBRJBRJBHYBRID CLOSURE #1 - PROFILE VIEW050010001500 (IN FEET)HORIZONTAL SCALE050100150 (IN FEET)VERTICAL SCALE T R A N S M I S S I O N L I N E C O R R I D O R TRANSMISSION LINECORRIDORTRANSMISSIONLINE CORRIDORPROPOSED STORMWATER PONDFREE WATER SURFACE LEVEL = 760INDUSTRIAL LANDFILLPERMIT NO. 1812(INCLUDING FUTUREPHASES 1 THROUGH 5)FGD LANDFILLPERMIT NO. 1809ASBESTOS LANDFILLPERMIT NO. 1804DEMOLITION LANDFILLPERMIT NO. 1804AAA3BA3B102030TENTHS0DWG SIZEREVISIONFORDRAWING NO.FILENAME:DWG TYPE:JOB NO:DATE:SCALE:DES:DFTR:CHKD:ENGR:APPD:2345786A22.0"x34.0"ANSI DSEAL123ABBCD78623456cDUKE ENERGYCLOSURE OPTIONS EVALUATIONCATAWBA COUNTY, NORTH CAROLINAMARSHALL STEAM STATION6057284911/02/2018CCCNOT FOR CONSTRUCTIONDRAFTAS SHOWNCLOSURE OPTION #3 - CLOSURE-BY-REMOVAL(ON-SITE LANDFILL) - PLAN VIEWA3AMSRMSRJBRJBRJBCLOSURE-BY-REMOVAL #1 - PLAN VIEW050010001500 (IN FEET)GRAPHIC SCALE 102030TENTHS0DWG SIZEREVISIONFORDRAWING NO.FILENAME:DWG TYPE:JOB NO:DATE:SCALE:DES:DFTR:CHKD:ENGR:APPD:2345786A22.0"x34.0"ANSI DSEAL123ABBCD78623456cDUKE ENERGYCLOSURE OPTIONS EVALUATIONCATAWBA COUNTY, NORTH CAROLINAMARSHALL STEAM STATION6057284911/02/2018CCCNOT FOR CONSTRUCTIONDRAFTAS SHOWN050010001500 (IN FEET)HORIZONTAL SCALE050100150 (IN FEET)VERTICAL SCALECLOSURE OPTION #3 - CLOSURE-BY-REMOVAL(ON-SITE LANDFILL) - PROFILE & SECTION VIEWSA3BMSRMSRJBRJBRJBCLOSURE-BY-REMOVAL #1 - PROFILE VIEWS AA5BT R A N SM I S S I O N L I N E C O R R I D O R TRANSMISSION LINECORRIDORTRANSMISSIONLINE CORRIDORLAKE NORMANAPPROX. ELEV = 760AINDUSTRIAL LANDFILLPERMIT NO. 1812(INCLUDING FUTUREPHASES 1 THROUGH 5)FGD LANDFILLPERMIT NO. 1809A5BASBESTOS LANDFILLPERMIT NO. 1804DEMOLITION LANDFILLPERMIT NO. 18041102030TENTHS0DWG SIZEREVISIONFORDRAWING NO.FILENAME:DWG TYPE:JOB NO:DATE:SCALE:DES:DFTR:CHKD:ENGR:APPD:2345786A22.0"x34.0"ANSI DSEAL123ABBCD78623456cDUKE ENERGYCLOSURE OPTIONS EVALUATIONCATAWBA COUNTY, NORTH CAROLINAMARSHALL STEAM STATION6057284911/02/2018CCCNOT FOR CONSTRUCTIONDRAFTAS SHOWNCLOSURE OPTION #5CLOSURE-IN-PLACE - PLAN VIEWA5AMSRMSRJBRJBRJBCLOSURE-IN-PLACE - PLAN VIEW050010001500 (IN FEET)GRAPHIC SCALE1231 102030TENTHS0DWG SIZEREVISIONFORDRAWING NO.FILENAME:DWG TYPE:JOB NO:DATE:SCALE:DES:DFTR:CHKD:ENGR:APPD:2345786A22.0"x34.0"ANSI DSEAL123ABBCD78623456cDUKE ENERGYCLOSURE OPTIONS EVALUATIONCATAWBA COUNTY, NORTH CAROLINAMARSHALL STEAM STATION6057284911/02/2018CCCNOT FOR CONSTRUCTIONDRAFTAS SHOWNCLOSURE OPTION #5CLOSURE-IN-PLACE - PROFILE & SECTION VIEWSA5BMSRMSRJBRJBRJBCLOSURE-IN-PLACE - PROFILE & SECTION VIEWS050010001500 (IN FEET)HORIZONTAL SCALE050100150 (IN FEET)VERTICAL SCALE STANDARD LANDFILLLINER SYSTEM ALTERNATE ASH BASIN CLOSUREAND LANDFILL CAP SYSTEM ALTERNATE LANDFILLLINER SYSTEMSTANDARD ASH BASIN CLOSUREAND LANDFILL CAP SYSTEM····102030TENTHS0DWG SIZEREVISIONFORDRAWING NO.FILENAME:DWG TYPE:JOB NO:DATE:SCALE:DES:DFTR:CHKD:ENGR:APPD:2345786A22.0"x34.0"ANSI DSEAL123ABBCD78623456cDUKE ENERGYCLOSURE OPTIONS EVALUATIONCATAWBA COUNTY, NORTH CAROLINAMARSHALL STEAM STATION6057284911/02/2018CCCNOT FOR CONSTRUCTIONDRAFTAS SHOWNLINER AND CAP DETAILSA6MSRMSRJBRJBRJBLINER AND CAP DETAILS Attachment B PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Cost Summary CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:CALCULATION SHEETAsh BasinHybrid 60432116 / 60572849ACTIVITY:CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 - Hybrid Rob Boeing 11/9/2018 John BoveCost (2018 Dollars)$7,807,771$174,709,249$86,764,216$28,911,548$7,637,311$76,457,524$4,500,000$386,787,619Cost (2018 Dollars)$17,237,760$33,159,132$12,599,223$6,299,612$69,295,727$456,083,346Engineering Costs (10%)Total Post-Closure of CCR Impoundment = Total Closure & Post-Closure of CCR Impoundment Cost = Post-Closure Tasks Groundwater Monitoring Operations & Maintenance (O&M)Contingency (25%) CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYPreliminary Project Costs SheetsCost Summary: Hybrid Cost Estimate for CCR ImpoundmentContingency (25%)Closure TasksMobilization / Site Prep / DemobilizationDewatering / Earthwork for Close-in-PlaceClosure System ConstructionTotal Closure Cost of CCR Impoundment = Dewatering / Excavation for Closure-by-Removal / Convey MaterialStormwater Management / E&S Controls / Site RestorationMarshall Active Ash Basin -- OPTION 1: Hybrid OptionClosure & Post-Closure Cost SummaryEngineering Support (Design & CQA)11/12/20181 of 6 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Hybrid Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Hybrid60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 - Hybrid Rob Boeing 11/09/18 John Bove2018Not Used502Not Used502Not Used31818415,904,0008,130,00024,034,00044,200700INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTMOBILIZATION / SITE PREP / DEMOBILIZATION1 MOBILIZATION / DEMOBILIZATION LS 1 $3,072,575 $3,072,5752 REMOVAL OF OUTLET STRUCTURES / PIPING LS 1$994,112 $994,1123 REMOVAL & FILTRATION OF FREE WATER MONTHS 36 $103,919 $3,741,084DEWATERING / EXCAVATION FOR CLOSURE-BY-REMOVAL / CONVEY MATERIAL4REMOVAL & TREATMENT OF PORE WATER WITHIN ASH IN CLOSURE-BY-REMOVAL AREAMONTHS 138 $225,832 $31,164,8165EXCAVATE ASH FOR CLOSURE-BY-REMOVAL / STOCKPILE ASHCY8,130,000 $8.00 $65,040,0006EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH TO CLOSE-IN-PLACE AREACY8,130,000 $8.43 $68,535,9007OVER EXCAVATE SOIL FROM CLOSURE-BY-REMOVAL / LOAD/ HAUL CCR-IMPACTED SOIL TO CLOSE-IN-PLACE AREACY296,853 $10.00 $2,968,5338DEEP MIXING METHOD (DMM) WALL TO STABILIZE CUT-SLOPE AT CLOSE-IN-PLACE / CLOSE-BY-REMOVAL INTERFACEL.F. 700 $10,000 $7,000,0009 EXCAVATE / LOAD / HAUL CCR MATERIAL (OFF-SITE)CY0 $57.00 $010 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFF-SITE)CY0 $57.00 $0 include if applicableDEWATERING / EARTHWORK FOR CLOSE-IN-PLACE11 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 0 $225,832 $012SPREAD AND COMPACT MATERIAL FROM CLOSURE-BY-REMOVAL AREACY8,130,000 $7.56 $61,462,80013 ASH REGRADING TO ESTABLISH CROWN CY 2,403,400 $9.24 $22,207,41614 RING DRAIN INSTALLATION L.F. 44,200 $58.00 $2,563,600AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)DEWATERING / EXCAVATION FOR CLOSURE-BY-REMOVAL / CONVEY MATERIALIMPOUNDMENT AREA TO BE CLOSED-IN-PLACE (AC)LENGTH OF CUT-SLOPE AT CLOSE-IN-PLACE / CLOSE-BY-REMOVAL INTERFACE (L.F.)HYBRID ESTIMATED COSTSMob/Demob & insurance: (1% of Total EPC Bid Price) includes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup).AVG. DEPTH OF FREE WATER (FT)IMPOUNDMENT AREA TO BE CLOSED-BY-REMOVAL (AC)TOTAL ASH VOLUME FROM CLOSURE-BY-REMOVAL (CY)MOBILIZATION /SITE PREP /DEMOBILIZATIONEXISTING ASH VOLUME IN AREA TO BE CLOSED-IN-PLACE (CY)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsCost Summary: Hybrid Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY:TOTAL IMPOUNDMENT AREA (AC)VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESStep 2: Assume CCR material must be stockpiled within impoundment area to decant prior to loading. Done in conjunction with Step 1. Decant water collected and treated along with pore water from Step 1. Assume DMM wall for large ponds that require excavating a portion of the pond and stacking excavated material on remaining portion.Assume outlet structures and piping will be excavated and removed.Already accounted for on a monthly basis in line item 4, hence not repeated herein.Quantity of earthwork (cut-to-fill) using existing ash to achieve positive slope prior to installation of closure system. Assumes 10% of close-in-place volume.Spread dewatered ash excavated from closure-by-removal area in thin lifts over close-in-place areaPERIMETER OF CLOSED-IN-PLACE IMPOUNDMENT (L.F.)TOTAL (FINAL) ASH VOLUME TO BE CLOSED-IN-PLACE (CY)DEWATERING / EARTHWORK FOR CLOSE-IN-PLACEBased on Initiation timeSTEP 1: Start dewaterting for Construction time. Based on Construction Time.Step 3: Once material has decanted, CCRs must be excavated out of stockpile, loaded on trucks and hauled to close-in-place areainclude if applicableAssume 1 foot of additional material to be removed over total close-by-removal impoundment area.Linear feet of the perimeter around the close-in-place area.11/12/20182 of 6 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Hybrid Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Hybrid60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 - Hybrid Rob Boeing 11/09/18 John Bove2018Not Used502Not Used502Not Used31818415,904,0008,130,00024,034,00044,200700INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTAREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)IMPOUNDMENT AREA TO BE CLOSED-IN-PLACE (AC)LENGTH OF CUT-SLOPE AT CLOSE-IN-PLACE / CLOSE-BY-REMOVAL INTERFACE (L.F.)HYBRID ESTIMATED COSTSAVG. DEPTH OF FREE WATER (FT)IMPOUNDMENT AREA TO BE CLOSED-BY-REMOVAL (AC)TOTAL ASH VOLUME FROM CLOSURE-BY-REMOVAL (CY)EXISTING ASH VOLUME IN AREA TO BE CLOSED-IN-PLACE (CY)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsCost Summary: Hybrid Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY:TOTAL IMPOUNDMENT AREA (AC)VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF CLOSED-IN-PLACE IMPOUNDMENT (L.F.)TOTAL (FINAL) ASH VOLUME TO BE CLOSED-IN-PLACE (CY)15 PERIMETER DITCH / TEMP. DIVERSION BERM GRADING L.F. 44,200$12.00 $530,400Linear feet of the perimeter around the close-in-place area.11/12/20183 of 6 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Hybrid Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Hybrid60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 - Hybrid Rob Boeing 11/09/18 John Bove2018Not Used502Not Used502Not Used31818415,904,0008,130,00024,034,00044,200700INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTAREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)IMPOUNDMENT AREA TO BE CLOSED-IN-PLACE (AC)LENGTH OF CUT-SLOPE AT CLOSE-IN-PLACE / CLOSE-BY-REMOVAL INTERFACE (L.F.)HYBRID ESTIMATED COSTSAVG. DEPTH OF FREE WATER (FT)IMPOUNDMENT AREA TO BE CLOSED-BY-REMOVAL (AC)TOTAL ASH VOLUME FROM CLOSURE-BY-REMOVAL (CY)EXISTING ASH VOLUME IN AREA TO BE CLOSED-IN-PLACE (CY)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsCost Summary: Hybrid Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY:TOTAL IMPOUNDMENT AREA (AC)VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF CLOSED-IN-PLACE IMPOUNDMENT (L.F.)TOTAL (FINAL) ASH VOLUME TO BE CLOSED-IN-PLACE (CY)CLOSURE SYSTEM CONSTRUCTION16 18" PROTECTIVE COVER SOIL CY 769,560 $13.00 $10,004,28017 6" TOPSOIL CY 256,520 $13.00 $3,334,76018 COMPACTED CLAY CY 0 $15.00 $019 FLEXIBLE MEMBRANE LINER (FML) SQ. FT. 15,237,288 $0.42 $6,430,13620 GEOCOMPOSITE DRAINAGE LAYER SQ. FT. 15,237,288 $0.60 $9,142,37321 GEOSYNTHETIC CLAY LINER (GCL) SQ. FT. 0 $0.72 $0STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION22 PERMANENT RIPRAP STORMWATER CHANNELS TONS 25,085 $50.00 $1,254,25023 SITE EROSION AND SEDIMENT CONTROL ACRE 502 $2,000 $1,004,00024 BACKFILL AND REGRADING OF CLOSURE-BY-REMOVAL AREA CY 445,280 $3.50 $1,558,48025 TOPSOIL CY 148,427 $13.00 $1,929,54726 SEED / FERTILIZE / MULCH ACRE 502 $3,767 $1,891,034CONTINGENCY / ENGINEERING SUPPORT27 CONTINGENCY (25%) LS 1 $76,457,524 $76,457,52428 ENGINEERING SUPPORT (DESIGN AND CQA) LS 1 $4,500,000 $4,500,000POST-CLOSURE 29 GROUNDWATER MONITORING ANNUAL 30 $574,592 $17,237,76030 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $1,105,304 $33,159,132CONTINGENCY / ENGINEERING COSTAssume total area to be restored will require site erosion and sediment control.Assume 6 inches of top soil needed (obtained off-site) to establish vegetative stabilization over total closure-by-removal area.Assume 18 inches of additional soil material (obtained on-site) graded over total closure-by-removal area.Annual groundwater monitoring costs for each CCR impoundment are based on current groundwater monitoring system.POST-CLOSURE STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATIONAssume total area of disturbance will be mulched, fertilized, and seeded.Assume 10 ft wide x 1 ft thick, 145 pcf riprap lined stormwater channels. Assumes 34,600 LF of stormwater channels.Annual O&M costs are $3475.80/ac/yr. Based on Q3 2018 Post Closure Maintenance data for closed area with cap.CONTINGENCY / ENGINEERING SUPPORTAlternate Cap System Only: Flexible membrane liner placed over close-in-place area. Assume quantity needed is 10% more than close-in-place area. Alternate Cap System Only: Geocomposite drainage layer placed over close-in-place area. Assume quantity needed is 10% more than close-in-place area.Not used.CLOSURE SYSTEM CONSTRUCTION18 inches of low perm. protective cover soil (Kv<1x10^-5) placed over close-in-place area.6 inches of topsoil placed over close-in-place area.Not used.11/12/20184 of 6 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Hybrid Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Hybrid60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 - Hybrid Rob Boeing 11/09/18 John Bove2018Not Used502Not Used502Not Used31818415,904,0008,130,00024,034,00044,200700INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTAREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)IMPOUNDMENT AREA TO BE CLOSED-IN-PLACE (AC)LENGTH OF CUT-SLOPE AT CLOSE-IN-PLACE / CLOSE-BY-REMOVAL INTERFACE (L.F.)HYBRID ESTIMATED COSTSAVG. DEPTH OF FREE WATER (FT)IMPOUNDMENT AREA TO BE CLOSED-BY-REMOVAL (AC)TOTAL ASH VOLUME FROM CLOSURE-BY-REMOVAL (CY)EXISTING ASH VOLUME IN AREA TO BE CLOSED-IN-PLACE (CY)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsCost Summary: Hybrid Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY:TOTAL IMPOUNDMENT AREA (AC)VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF CLOSED-IN-PLACE IMPOUNDMENT (L.F.)TOTAL (FINAL) ASH VOLUME TO BE CLOSED-IN-PLACE (CY)31 CONTINGENCY (25%) LS 1 $12,599,223 $12,599,22332 ENGINEERING COST (10%) LS 1 $6,299,612 $6,299,612TOTAL$456,083,346CONTINGENCY / ENGINEERING COST11/12/20185 of 6 PROJECTPLANT NAME: CLOSURE TYPE: SHEET REV. NO. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYMarshall CCR Rule & CAMA Compliant Hybrid Assumptions CSUBJECTIMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.Ash Basin Hybrid 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 - Hybrid Rob Boeing 11/09/18 John Bove1234567891011 Assume an over-excavation of 1 foot is necessary to achieve closure-by-removal conditions.1213141516Common soil for embankment and protective cover soil construction are available on-site and topsoil would come from off-site.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.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.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. 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.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.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.CALCULATION SHEETPreliminary Project Costs SheetsACTIVITYHybid Closure AssumptionsEngineering design and CQA cost has been included for this cost estimate based on reasonable assumptions.KEY ASSUMPTIONSThe unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience.Free water removal and treatment was assumed to continue throughout the project initiation period.Interstitial water treatment was assumed to continue until construction is completed.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. The following key assumptions and limitations are associated with the project design, implementation and performance: The cost estimates were prepared using 2018 dollars and do not include any escalation.A 25% contingency has been included for this cost estimate.Ash to be moisture conditioned and compacted in the stack area.11/12/20186 of 6 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Cost Summary CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:CALCULATION SHEETAsh BasinClose-by-Removal 60432116 / 60572849ACTIVITY:CLOSURE OPTION: LAST UPDATED BY:DATE LAST MODIFIED: REVIEWED BY:Option 3 - Closure-by-Removal (On-Site Landfill)RJB 11/9/2018 John BoveCost (2018 Dollars)$15,072,265$476,469,475$341,457,367$17,120,127$212,529,809$5,000,000$1,067,649,043Cost (2018 Dollars)$17,237,760$20,745,750$9,495,878$4,747,939$52,227,326$1,119,876,369Engineering Costs (10%)Total Post-Closure of CCR Impoundment = Total Closure & Post-Closure of CCR Impoundment Cost = Post-Closure Tasks Groundwater Monitoring Operations & Maintenance (O&M)Contingency (25%)Close-by-Removal TasksMobilization / Site Prep / DemobilizationMarshall Active Ash Basin -- OPTION 3: Closure-by-Removal Option (On-site Landfill)Closure & Post-Closure Cost SummaryEngineering Support (Design & CQA) CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYPreliminary Project Costs SheetsCost Summary: Close-by-Removal Cost Estimate for CCR Impoundment (On-Site Landfill)Contingency (25%)Total Closure Cost of CCR Impoundment = Achieve Closure-by-Removal / Convey MaterialStormwater Management / E&S Controls / Site RestorationOn-Site Landfill Construction, Disposal, and Closure11/12/20181 of 5 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Close-by-Removal Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Close-by-Removal 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 3 - Closure-by-Removal (On-Site Landfill)RJB 11/09/18 John Bove2018Not Used502Not Used502Not Used24,022,700Not UsedINSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTMOBILIZATION / SITE PREP / DEMOBILIZATION1 MOBILIZATION / DEMOBILIZATION LS 1 $8,466,527 $8,466,5272 REMOVAL OF OUTLET STRUCTURES / PIPING LS 1$994,112 $994,1123 REMOVAL & FILTRATION OF FREE WATER MONTHS 54 $103,919 $5,611,626ACHIEVE CLOSURE-BY-REMOVAL / CONVEY MATERIAL4 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 335 $225,832$75,653,7205 EXCAVATE ASH FOR CLOSURE-BY-REMOVAL / STOCKPILE ASHCY24,022,700 $8.00 $192,181,6006 EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH (DISPOSE ON-SITE)CY24,022,700 $8.43 $202,511,3617 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (ON-SITE)CY809,893 $7.56 $6,122,7948 EXCAVATE / LOAD / HAUL CCR MATERIAL (OFF-SITE LF)CY0 $57.00 $09 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFF-SITE LF)CY0 $57.00 $0ON-SITE LANDFILL CONSTRUCTION, DISPOSAL AND CLOSURE10 CONSTRUCT ON-SITE LANDFILL AND ASSOCIATED COMPONENTS AC199 $803,245 $159,845,755TOTAL CLOSURE-BY-REMOVAL AREA (AC)AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)AVG. DEPTH OF FREE WATER (FT)Assume outlet structures and piping will be excavated and removed.CLOSE-BY-REMOVAL ESTIMATED COSTSVOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF CLOSURE-BY-REMOVAL AREA (L.F.)VOLUME OF ASH IN CLOSURE-BY-REMOVAL AREA (CY)MOBILIZATION /SITE PREP /DEMOBILIZATIONMob/Demob & insurance: (1% of Total EPC Bid Price) includes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup).Based on Initiation time Assume landfill designed and constructed in accordance with CAMA and CCR Rules. Cost includes landfill construction and all associated components, including: double liner system, leachate management, stormwater management, access roads, closure system, and all associated components,etc., for new phases of the expanded Industrial Landfill.Only include if disposing CCRs at an off-site landfill (assume density of 1.2 tons/cy).ON-SITE LANDFILL CONSTRUCTION, DISPOSAL AND ACHIEVE CLOSURE-BY-REMOVAL /CONVEY MATERIAL Assume 1 foot of additional material to be removed over total impoundment area.STEP 1: Start dewaterting for Construction time. Based on Construction Time.Step 3: Once material has decanted, CCRs must be excavated out of stockpile, loaded on trucks and hauled to on-site landfill.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 and treated along with pore water from Step 1. CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsClose-by-Removal Costs: Closure-by-Removal Cost Estimate for CCR Impoundment (On-Site Landfill) CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITYOnly include if disposing CCRs at an off-site landfill (assume density of 1.2 tons/cy).11/12/20182 of 5 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Close-by-Removal Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Close-by-Removal 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 3 - Closure-by-Removal (On-Site Landfill)RJB 11/09/18 John Bove2018Not Used502Not Used502Not Used24,022,700Not UsedINSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTTOTAL CLOSURE-BY-REMOVAL AREA (AC)AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)AVG. DEPTH OF FREE WATER (FT)CLOSE-BY-REMOVAL ESTIMATED COSTSVOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF CLOSURE-BY-REMOVAL AREA (L.F.)VOLUME OF ASH IN CLOSURE-BY-REMOVAL AREA (CY)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsClose-by-Removal Costs: Closure-by-Removal Cost Estimate for CCR Impoundment (On-Site Landfill) CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY11DISPOSE/SPREAD/COMPACT ASH AND CCR-IMPACTED MATERIALS FROM CLOSURE-BY-REMOVAL AREA IN ON-SITE LANDFILL CY24,022,700 $7.56 $181,611,61212 ON-SITE LANDFILL CLOSURE SYSTEMAC199 $0Place, spread and compact in thin lifts dewatered ash and CCR-impacted materials excavated from closure-by-removal area into landfill.CLOSUREIncluded with landfill construction under line item 1011/12/20183 of 5 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Close-by-Removal Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Close-by-Removal 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 3 - Closure-by-Removal (On-Site Landfill)RJB 11/09/18 John Bove2018Not Used502Not Used502Not Used24,022,700Not UsedINSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTTOTAL CLOSURE-BY-REMOVAL AREA (AC)AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)AVG. DEPTH OF FREE WATER (FT)CLOSE-BY-REMOVAL ESTIMATED COSTSVOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF CLOSURE-BY-REMOVAL AREA (L.F.)VOLUME OF ASH IN CLOSURE-BY-REMOVAL AREA (CY)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsClose-by-Removal Costs: Closure-by-Removal Cost Estimate for CCR Impoundment (On-Site Landfill) CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITYSTORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION13 PERMANENT RIPRAP STORMWATER CHANNELS TONS 18,560 $50.00 $928,00014 SITE EROSION AND SEDIMENT CONTROL ACRE 502 $2,000 $1,004,00015 BACKFILL AND REGRADINGCY767,140 $13.00 $9,972,82016 TOPSOILCY255,713 $13.00 $3,324,27317 SEED / FERTILIZE / MULCH ACRE 502 $3,767 $1,891,034CONTINGENCY / ENGINEERING SUPPORT18 CONTINGENCY (25%) LS 1 $212,529,809 $212,529,80919 ENGINEERING SUPPORT (DESIGN AND CQA) LS 1 $5,000,000 $5,000,000POST-CLOSURE 20 GROUNDWATER MONITORING ANNUAL 30$574,592 $17,237,76021 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30$691,525 $20,745,750CONTINGENCY / ENGINEERING COST22 CONTINGENCY (25%) LS 1 $9,495,878 $9,495,87823 ENGINEERING COST (10%) LS 1 $4,747,939 $4,747,939TOTAL$1,119,876,369STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATIONAssume 10 ft wide x 1 ft thick, 145 pcf riprap lined stormwater channels. Assumes 25,600 LF of stormwater channels.Assume total area to be restored will require site erosion and sediment control.Annual groundwater monitoring costs for each CCR impoundment are based on current groundwater monitoring system.Annual O&M costs are $3,475/acre/yr for the landfill cap area (includes leachate collection system maintenance). Based on Q3 2018 Post Closure Maintenance data. Assume total area of disturbance will be mulched, fertilized, and seeded.Assume 18 inches of additional soil material (obtained on-site) graded over total closed-by-removal area and not covered by the Industrial LandfillAssume 6 inches of top soil needed (obtained off-site) to establish vegetative stabilization over total closed-by-removal area and not covered by the Industrial LandfillCONTINGENCY / ENGINEERING SUPPORTCONTINGENCY / ENGINEERING COSTPOST-CLOSURE 11/12/20184 of 5 PROJECTPLANT NAME: CLOSURE TYPE: SHEET REV. NO. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYMarshall CCR Rule & CAMA Compliant Close-by-Removal Assumptions CSUBJECTIMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.Ash Basin Close-by-Removal 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 3 - Closure-by-Removal (On-Site Landfill)RJB 11/09/18 John Bove12345678910111213Groundwater 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.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.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.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.CALCULATION SHEETPreliminary Project Costs SheetsACTIVITYClose-by-Removal AssumptionsThe following key assumptions and limitations are associated with the project design, implementation and performance: KEY ASSUMPTIONSInterstitial water treatment was assumed to continue until construction is completed.AECOM has assumed an over-excavation of 1 foot is necessary to achieve closure-by-removal conditions.Costs for onsite landfill construction was based on a per acre basis as provided by Duke.Engineering design and CQA cost has been included for this cost estimate based on reasonable assumptions.The cost estimates were prepared using 2018 dollars and do not include any escalation.A 25% contingency has been included for this cost estimate.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. Free water removal and treatment was assumed to continue throughout the project initiation period.The unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience.11/12/20185 of 5 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Cost Summary CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:CALCULATION SHEETAsh BasinClose-in-Place 60432116 / 60572849ACTIVITY:CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 5 - Close-in-Place RJB 11/9/2018 John BoveCost (2018 Dollars)$5,760,817$64,449,400$45,592,135$47,860,234$40,915,646$2,900,000$207,478,232Cost (2018 Dollars)$17,237,760$52,333,500$17,392,815$8,696,408$95,660,483$303,138,715Total Closure Cost of CCR Impoundment = Dewatering / Earthwork / Subgrade Prep.Closure System ConstructionStormwater Management / E&S Controls / Site RestorationContingency (25%)Engineering Support (Design & CQA)Engineering Costs (10%)Total Post-Closure of CCR Impoundment = Total Closure & Post-Closure of CCR Impoundment Cost = Post-Closure Tasks Groundwater Monitoring Operations & Maintenance (O&M)Contingency (25%)Close-in-Place TasksMobilization / Site Prep CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYPreliminary Project Costs SheetsCost Summary: Close-in-Place Cost Estimate for CCR ImpoundmentMarshall Steam Station -- OPTION 5: Close-in-Place OptionClosure & Post-Closure Cost Summary11/12/20181 of 5 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Close-in-Place Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Close-in-Place 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY:DATE LAST MODIFIED: REVIEWED BY:Option 5 - Close-in-Place RJB 11/09/18 John Bove2018Not Used502Not Used502Not Used24,022,70075,100INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTMOBILIZATION / SITE PREP1 MOBILIZATION LS 1 $1,649,135 $1,649,1352 ABANDON OUTLET STRUCTURES / PIPING LS 1$994,112 $994,1123 REMOVAL & FILTRATION OF FREE WATER MONTHS 30 $103,919 $3,117,570DEWATERING / EARTHWORK / SUBGRADE PREP4 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 150 $225,832$33,874,8005 RING DRAIN INSTALLATION L.F. 75,100 $58.00 $4,355,8006 ASH REGRADING TO ESTABLISH CROWN CY 2,740,000 $9.24 $25,317,6007 PERIMETER DITCH / TEMP. DIVERSION BERM GRADING L.F. 75,100$12.00 $901,2008 CONTACT STORM WATER TREATMENTGALCLOSURE SYSTEM CONSTRUCTION9 18" PROTECTIVE COVER SOIL CY 1,214,840 $13.00 $15,792,920AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)NOTESBased on Initiation TimeAVG. DEPTH OF FREE WATER (FT)Mob/Demob & insurance: (1% of Total EPC Bid Price includes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup).CLOSE-IN-PLACE ESTIMATED COSTSTOTAL IMPOUNDMENT AREA (AC)VOLUME OF ASH IN IMPOUNDMENT (CY)PERIMETER OF IMPOUNDMENT (L.F.)VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)DEWATERING / EARTHWORK / SUBGRADE PREPMOBILIZATION /SITE PREPQuantity of earthwork (cut-to-fill) using existing ash to achieve positive slope prior to installation of closure system. Quantity calculated using AutoCAD. 18 inches of common soil placed over close-in-place area (assume on-site soils available)Abandon existing outlet structures and piping.Based on Construction TimeLinear feet around the proposed cap.Linear feet around the perimeter of impoundment.CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsACTIVITY:Cost Summary: Close-in-Place Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY11/12/20182 of 5 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Close-in-Place Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Close-in-Place 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY:DATE LAST MODIFIED: REVIEWED BY:Option 5 - Close-in-Place RJB 11/09/18 John Bove2018Not Used502Not Used502Not Used24,022,70075,100INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTAREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)NOTESAVG. DEPTH OF FREE WATER (FT)CLOSE-IN-PLACE ESTIMATED COSTSTOTAL IMPOUNDMENT AREA (AC)VOLUME OF ASH IN IMPOUNDMENT (CY)PERIMETER OF IMPOUNDMENT (L.F.)VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsACTIVITY:Cost Summary: Close-in-Place Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY10 6" TOPSOIL CY 404,947 $13.00 $5,264,30711 COMPACTED LOW PERM. SOILS (Kv<1x10^-5 cm/sec) CY 0 $15.00 $012 FLEXIBLE MEMBRANE LINER (FML) SQ. FT. 24,053,832 $0.42 $10,102,60913 GEOCOMPOSITE DRAINAGE LAYER SQ. FT. 24,053,832 $0.60 $14,432,29914 GEOSYNTHETIC CLAY LINER (GCL) SQ. FT. 0 $0.72 $0STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION15 SITE EROSION AND SEDIMENT CONTROL ACRE 502 $2,000 $1,004,00016 STORMWATER MANAGEMENT / CHANNELS / LET-DOWNS L.F. 60,600$742 $44,965,20017 SEED / FERTILIZE / MULCH ACRE 502 $3,767 $1,891,034CONTINGENCY / ENGINEERING SUPPORT18 CONTINGENCY (25%) LS 1 $40,915,646 $40,915,64619 ENGINEERING SUPPORT (DESIGN AND CQA) LS 1 $2,900,000 $2,900,000POST-CLOSURE 20 GROUNDWATER MONITORING FOR ASH BASIN ANNUAL 30 $574,592 $17,237,76021OPERATIONS & MAINTENANCE (O&M) FOR CLOSURE-IN-PLACE CAP AREAANNUAL 30 $1,744,450 $52,333,500Not used.STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATIONAssume rip-rap lined stormwater conveyance channels and rip-rap lined let-downs off of cap. Assume 60,600 LF of stormwater channels / let downs.CLOSURE SYSTEM CONSTRUCTIONAlternate Cap System Only: Flexible membrane liner placed over close-in-place area. Assume quantity needed is 10% more than close-in-place area. Alternate Cap System Only: Geocomposite drainage layer placed over close-in-place area. Assume quantity needed is 10% more than close-in-place area.Annual groundwater monitoring costs for each CCR impoundment are based on current groundwater monitoring systemAnnual O&M costs are $3475/acre/yr for the total closed area with cap. Based on Q3 2018 Post Closure Maintenance dataPOST-CLOSURE CONTINGENCY / ENGINEERING SUPPORTNot used.6 inches of topsoil (obtained off-site) placed over closure-by-removal area.Assume total area to be restored will require site erosion and sediment control.Assume total area to be restored will be mulched, fertilized, and seeded.11/12/20183 of 5 PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Marshall CCR Rule & CAMA Compliant Close-in-Place Costs CSUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:Ash Basin Close-in-Place 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY:DATE LAST MODIFIED: REVIEWED BY:Option 5 - Close-in-Place RJB 11/09/18 John Bove2018Not Used502Not Used502Not Used24,022,70075,100INSTALLED IMPOUNDMENT TASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTAREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)NOTESAVG. DEPTH OF FREE WATER (FT)CLOSE-IN-PLACE ESTIMATED COSTSTOTAL IMPOUNDMENT AREA (AC)VOLUME OF ASH IN IMPOUNDMENT (CY)PERIMETER OF IMPOUNDMENT (L.F.)VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsACTIVITY:Cost Summary: Close-in-Place Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYCONTINGENCY / ENGINEERING COST22 CONTINGENCY (25%) LS 1 $17,392,815 $17,392,81523 ENGINEERING COST (10%) LS 1 $8,696,408 $8,696,408TOTAL$303,138,715CONTINGENCY / ENGINEERING COST11/12/20184 of 5 PROJECTPLANT NAME: CLOSURE TYPE: SHEET REV. NO. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYMarshall CCR Rule & CAMA Compliant Close-in-Place Assumptions CSUBJECTIMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.Ash Basin Close-in-Place 60432116 / 60572849CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 5 - Close-in-Place RJB 11/09/18 John Bove12345678910111213Groundwater 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.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. The cost estimates were prepared using 2018 dollars and do not include any escalation.A 25% contingency has been included for this cost estimate.The unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience.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.Common soil for embankment and protective cover soil construction are available onsite and topsoil would come from offsite.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. 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.To establish the positive slopes, assume existing ash will be utilized to establish crown. Preliminary Project Costs SheetsACTIVITYClose-in-Place AssumptionsCALCULATION SHEETKEY ASSUMPTIONSThe following key assumptions and limitations are associated with the project design, implementation and performance: Engineering design and CQA cost has been included for this cost estimate based on reasonable assumptions.Interstitial water treatment was assumed to continue until construction is completed.Free water removal and treatment was assumed to continue throughout the project initiation period.11/12/20185 of 5 Attachment C 1 of 3 Site Name: Marshall Steam Station 1 = Option-Specific User Input 11/13/2018 1 = Calculated Value Option 1 Hybrid Closure Option - Hybrid footprint over areas within ash basin waste boundary while closing-in-place the Ash Basin "fingers." 2 Hybrid Closure Option #2 - Hybrid footprint over areas within ash basin waste boundary and excavating the ash Basin "fingers." 3 Closure-by-Removal - On-site landfill within Ash Basin waste boundary. 4 Closure-by-Removal #2 -Off-site third party landfill 5 Closure-In-Place Not carried through for further consideration. Environmental Protection and Impacts Weight:30% Criterion Scoring System Required Input Units Option 1 Option 3 Option 5 Option 1 Option 3 Option 5 Modeled plume intersecting surface water Refer to GW Sub-Scoring Sheet 0 5 10 23.8%7.1% Modeled groundwater impact beyond the current compliance boundary Refer to GW Sub-Scoring Sheet 10 10 10 23.8%7.1% Modeled off-site impact Refer to GW Sub-Scoring Sheet 10 10 10 23.8%7.1% Relative rank based on visual interpretation of modeled boron plume Refer to GW Sub-Scoring Sheet 0 10 5 13.6%4.1% Air emissions off-site (based on miles driven round- trip hauling CCR and CCR contaminated soil) Interpolation. Min value scores 10. Max value scores 0.Truck miles driven Miles 0 0 0 0 0 10 10 10 5.0%1.5% Air emissions on-site cubic yards of excavation/movement Interpolation. Min value scores 10. Max value scores 0. Volume of material excavation/movement CY 8,426,853 24,832,593 2,740,000 2,740,000 24,832,593 7 0 10 5.0%1.5% Avoidance of greenfield disturbance Interpolation. Min value scores 10. Max value scores 0. Disturbed acres of greenfield Acres 50 247 50 50 247 10 0 10 5.0%1.5% 1.83 2.34 2.80 Cost Weight:35% Criterion Scoring System Required Input Units Option 1 Option 3 Option 5 Option 1 Option 3 Option 5 Closure Cost Closure Cost USD $386,787,619 $1,067,649,043 $207,478,232 207,478,232.00$ 1,067,649,043.00$ 7.9 0.0 10.0 80.0%28.0% Operation, Maintenance and Monitoring Cost OM&M Cost USD $69,295,727 $52,227,326 $95,660,483 52,227,326.00$ 95,660,483.00$ 6.1 10.0 0.0 20.0%7.0% 2.64 0.70 2.80 Schedule Weight:15% Criterion Scoring System Required Input Units Option 1 Option 3 Option 5 Option 1 Option 3 Option 5 Initiation Time Time to move first ash Months 36 54 30 30 54 8 0 10 30.0%4.5% Construction Duration Estimated durations Months 138 335 150 138 335 10 0 9 70.0%10.5% 1.41 0.00 1.40 1. Provide continued geotechnical stability meeting appropriate safety factors under applicable loading conditions Threshold Criteria: All closure options must comply with the following threshold criteria based on Duke Energy Guiding Principals for Ash Basin Closure 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) Scoring for Evaluation of Closure Options Closure Options Evaluation Worksheet Ash Basin Closure - Master Programmatic Document Duke Energy Contribution to Total Score Value that Scores 0 Contribution to Total Score User Input Please refer to the Groundwater Sub-Scoring Document for details Calculated or User Selected Score Criterion Weight Calculated or User Selected Score Criterion Weight User Input Value that Scores 10 Value that Scores 10 Value that Scores 0 Please refer to the Groundwater Sub-Scoring Document for details Please refer to the Groundwater Sub-Scoring Document for details Criterion WeightValue that Scores 0 Calculated or User Selected Score Weighted Totals (Contribution to Total Score) Contribution to Total Score User Input Value that Scores 10 Interpolation Minimum value scores 10 Please refer to the Groundwater Sub-Scoring Document for details Interpolation. Min value scores 10. Max value scores 0. Weighted Totals (Contribution to Total Score) Weighted Totals (Contribution to Total Score) Zero (0) values have been entered in "Calculated or User Selected Score" under Beneficial Reuse to prevent division by zero error text in calculated score cells. 2 of 3 Site Name: Marshall Steam Station 1 = Option-Specific User Input 11/13/2018 1 = Calculated Value Scoring for Evaluation of Closure Options Closure Options Evaluation Worksheet Ash Basin Closure - Master Programmatic Document Duke Energy Zero (0) values have been entered in "Calculated or User Selected Score" under Beneficial Reuse to prevent division by zero error text in calculated score cells. Regional Factors Weight:15% Criterion Scoring System Required Input Units Option 1 Option 3 Option 5 Option 1 Option 3 Option 5 Plan or potential for beneficial reuse of site Subjective 0 0 0 5.0%0.8% Imported soil needs Interpolation. Min value scores 10. Max value scores 0.Soil Imported CY 1,619,787 4,374,960 1,619,787 1,619,787 4,374,960 10 0 10 5.0%0.8% Beneficial reuse of CCR Interpolation. Max value scores 10. Zero value scores 0.Fraction Used None 0 0 0 0 0.0 0 0 0 15.0%2.3% Transportation impact (based on miles driven) Interpolation. Min value scores 10. Max value scores 0.Miles Driven Miles 0 10 0 0 10 10 0 10 65.0%9.8% Noise impact due to on-site activity (based on proximity of neighbors to on-site work areas) Subjective 0 to 10: 10 is the least noise; 0 is the most noise.8 4 10 5.0%0.8% View impact (based on final height of storage facility and land uses within viewshed) Subjective 0 to 10; 10 is the least visual; 0 is the most visual.7 0 10 5.0%0.8% 1.16 0.03 1.20 Constructability Weight:5% Criterion Scoring System Required Input Units Option 1 Option 3 Option 5 Option 1 Option 3 Option 5 Consider stormwater management, geotechnical, and dewatering Subjective 0 to 10: 10 is the least commplicated; 0 is the most complicated 4 4 8 100.0%5.0% 0.20 0.20 0.40 7.24 3.27 8.59 Value that Scores 0 Total Score For Each Option (On a Scale of 0 to 10) Weighted Totals (Contribution to Total Score) User Input Value that Scores 10 Value that Scores 0 Calculated or User Selected Score Value that Scores 10 Weighted Totals (Contribution to Total Score) Not Used For Subjective Scoring User Input Calculated or User Selected Score Contribution to Total Score Criterion Weight Not Used For Subjective Scoring Not Used For Subjective Scoring 3 of 3 Criteria for Evaluation of Closure Options Closure Options Evaluation Worksheet Ash Basin Closure - Master Programmatic Document Duke Energy 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 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 Air emissions off-site (based on miles driven round-trip)Based on truck miles driven for hauling CCR and 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 Operation, Maintenance and Monitoring Cost Initiation Time 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 for hauling CCR and CCR-impacted soil. Noise impact due to on-site activity Based on proximity of neighbors to specific on-site work areas. View impact Based on final height of storage facility and land uses within viewshed. Constructability Consider stormwater management, geotechnical, and dewatering Subjective and relative comparison to other options Regional Factors From rough order-of-magnitude cost estimate or detailed cost estimate. Threshold Criteria: All closure options must comply with the following threshold criteria based on Duke Energy Guiding Principals for Ash Basin Closure From preliminary schedule for designing, permitting, bidding and constructing the option. 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 Environmental Protection and Impacts Cost Schedule 3. Effectively mitigate groundwater impacts 4. Comply with applicable state and federal regulations (e.g. North Carolina Coal Ash Management Act) Environmental Groundwater Sub‐scoring WorksheetClosure Options Evaluation Duke EnergyScored by: TH, RC, CMCriteria 1.  Modeled Plume Intersecting Surface Water ScoreModeled plume1 does not intersect surface waters after 10 years10Modeled plume1 does not intersect surface waters after 100 years5Modeled plume1 does not intersect surface waters after 200 years0(Option 1) (Option 3) (Option 5)Hybrid OptionClosure‐By‐Removal: Existing On‐site Landfill Closure‐In‐Place 0510Criteria 2.  Groundwater Impact Beyond the current2 Compliance Boundary ScoreModeled plume1 is within current compliance boundary after 10 years10Modeled plume1 is within current compliance boundary after 100 years5Modeled plume1 is within current compliance boundary after 200 years0(Option 1) (Option 2) (Option 3A)(Option 1) (Option 3) (Option 5)Hybrid OptionClosure‐By‐Removal: Existing On‐site Landfill Closure‐In‐Place 10 10 10Criteria 3.  Modeled Off‐site Impact ScoreModeled plume1 does not go off‐site 10Modeled plume1 is predicted to remain off‐site after 100 years5Modeled plume1 is predicted to remain off‐site after 200 years0(Option 1) (Option 3) (Option 5)Hybrid OptionClosure‐By‐Removal: Existing on‐site Landfill Closure‐In‐Place 10 10 10Criteria 4.  Relative rank based on visual interpretation of modeled boron plume ScoreRanked #1 among the three Closure Options based on visual interpretation of modeled boron plume  10Ranked #2 among the three Closure Options based on visual interpretation of modeled boron plume  5Ranked #3 among the three Closure Options based on visual interpretation of modeled boron plume  0(Option 1) (Option 3) (Option 5) Hybrid OptionClosure‐By‐Removal: Existing On‐site Landfill Closure‐In‐Place 0105Note 2: The current compliance boundary is the compliance boundary found in the figure "Ash Basin Waste and Compliance Boundaries" provided to NCDEQ on 12/19/17Station/Plant Name: Marshall Steam StationEvaluation Criteria: Criteria 1 ScoreMarshall Ash Basin Groundwater Sub‐Scoring DocumentNote 1: Based on avaliable data at the time of scoring, the modeled plume considered boron at a concentration of 4,000 ug/l 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.Criteria 2 ScoreCriteria 3 ScoreCriteria 4 Score Environmental Groundwater Sub‐scoring WorksheetClosure Options Evaluation Duke Energy(Option 1) (Option 3) (Option 5)Justification NotesHybrid OptionClosure‐By‐Removal: Existing On‐site Landfill Closure‐In‐Place 0510Based on the predictive model for the year 2050 and 2300, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the hybrid option with natural attenuation showed boron of 4,000 ppb or greater intercepting a future surface water body. In the hybrid option for Marshall Steam Station, ash is removed from the southern portion of the ash basin and moved north to consolidate the waste footprint.  After removal of the ash, a small pond will form in the former footprint of the ash basin.  It is Duke Energy understanding that the new pond within the southern portion of the former ash basin footprint will be considered Waters of the State.Based on the predictive model for the year 2050 and 2100, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the Closure‐by‐Removal option with natural attenuation showed boron of 4,000 ppb or greater intercepting a future surface water body until 2100. In the Closure‐by‐Removal option for Marshall Steam Station, ash is removed from the southern portion of the ash basin placed in an existing on‐site landfill.  After removal of the ash, a small pond will form in the southern portion of the former footprint of the ash basin.  It is Duke Energy understanding that the new pond within the southern portion of the former ash basin footprint will be considered Waters of the State.Based on the predictive model for the year 2050, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the Closure‐In‐Place option with natural attenuation did not show boron of 4,000 ppb or greater intercepting a surface water body.10 10 10Based on the predictive model for the year 2050, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the hybrid option showed boron of 4,000 ppb or greater within the current compliance boundary in 2050.   A score of 10 was determined to be most appropriate.Based on the predictive model for the year 2050, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the Closure‐by‐Removal option showed boron of 4,000 ppb or greater within the current compliance boundary in 2050.   A score of 10 was determined to be most appropriate.Based on the predictive model for the year 2050, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the Closure‐In‐Place option showed boron of 4,000 ppb or greater within the current compliance boundary in 2050.   A score of 10 was determined to be most appropriate.10 10 10Based on the predictive model for the year 2050, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the hybrid option with natural attenuation did not show boron of 4,000 ppb or greater outside of the current Duke Energy property boundary in 2050.  A score of 10 was determined to be most appropriate.Based on the predictive model for the year 2050, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the Closure‐by‐Removal option with natural attenuation did not show boron of 4,000 ppb or greater outside of the current Duke Energy property boundary in 2050.  A score of 10 was determined to be most appropriate.Based on the predictive model for the year 2050, found in the November 2018 Revised Groundwater Flow and Transport Modeling Report for Marshall Steam Station, simulated boron concentrations for the Closure‐In‐Place option with natural attenuation did not show boron of 4,000 ppb or greater outside of the current Duke Energy property boundary in 2050.  A score of 10 was determined to be most appropriate.0105Based on a review of boron concentrations found in the November 2018 Revised Groundwater Flow and Transport Modeling Report, this option  is not marginally better than Option 3 (Closure‐by‐Removal) or Option  5 (Closure‐In‐Place). Based on a review of boron concentrations found in the November 2018 Revised Groundwater Flow and Transport Modeling Report, this option  is marginally better than Optoin 1 (Hybrid Option) and Option 5 (Closure‐In‐Place).Based on a review of boron concentrations found in the November 2018 Revised Groundwater Flow and Transport Modeling Report, this option  is marginally better than Option 3 (Closure‐by‐Removal).Marshall Ash Basin Groundwater Sub‐Scoring Document JustificationNotes:1. Based on avaliable data at the time of scoring, the modeled plume considered boron at a concentration of 4,000 ug/l 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 "Ash Basin Waste and Compliance Boundaries" provided to NCDEQ on 12/19/17.Criteria 1.  Modeled Plume Intersecting Surface WaterCriteria 2.  Groundwater Impact Beyond the Current Compliance Boundary Criteria 3.  Modeled Off‐site Impact Criteria 4.  Relative rank based on visual interpretation of modeled boron plume