Allen_ClosureOptionsAnalysis_20181115

Summary – Page 1
Allen Steam Station Ash Basin Closure Options Analysis
Summary Report

This summary report (Report) presents the Closure Options evaluation for the Ash Basins located at
Duke Energy Carolinas, LLC’s (Duke Energy’s) Allen Steam Station, located in Gaston 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
Allen that is protective of the environment, safely closes the Ash Basins, minimizes the other associated
risks, and was the least cost to customers. A permit-level design was developed for that option in 2016.
The company then paused that work, pending determination that the site would meet the requirements
for a low-risk impoundment classification pursuant to CAMA, as amended by House Bill 630. Duke
Energy has completed those requirements at the Allen site for a low-risk classification and now has
updated this analysis.
This updated Closure Options Evaluation includes updates to the Closure-In-Place option per the most
recent design. In addition, unit costs and material quantities have been updated where appropriate for
all options.
SITE BACKGROUND
Allen Station is located along the west shore of Lake Wylie, a man-made reservoir created by the
impoundment of the Catawba River. Allen Station is a five-unit, 1,140 megawatts, coal-fired generating
facility. Allen Station began commercial operation in 1957 with units 1 and 2. Unit 3 began operation in
1959, unit 4 in 1960, and unit 5 in 1961.
Allen Station historically wet sluiced coal combustion residual (CCR) products into two surface
impoundments located on the property. These surface impoundments are known as the Retired Ash
Basin (RAB) which is also referred to as the Inactive Ash Basin (IAB) and Active Ash Basin (AAB), which
are impounded by the following dams:

Summary – Page 2
• Retired Ash Basin (GASTO-016)
• Active Ash Basin (GASTO-061)
The RAB received CCR products from initial operation in 1957 until 1973, when it reached capacity and
was retired. Allen Station then commissioned the AAB and began wet sluicing CCR products into this
new basin. In 2009, Allen Station replaced its fly ash wet sluicing operation with a dry ash handling
system and began placing dry fly ash into a landfill constructed over a portion of the RAB (Permit No. 36-
12). Allen Station currently wet sluices only bottom ash into the AAB and this operation will cease once
the dry bottom ash system becomes operational, which is scheduled to occur in early 2019.
Based on currently available information, the ash basins are estimated to contain a total of
approximately 19,515,700 tons of ash (16,263,000 cubic yards) which includes ash associated with the
landfill. This estimate is based on Duke’s Ash Inventory dated July 31, 2018 and the 2017-2018 Annual
Landfill Capacity Report (August 2, 2018) which includes data from an aerial survey obtained on May 9,
2018. The RAB Landfill is active at this time and is estimated to have capacity (Phase 1, Cells 1 and 2)
until 2029 based on projected future ash generation from station operations. Figure 1 presents the
Active and Retired Ash Basins and associated dams.

Figure 1. Active and Retired Ash Basins
HOLDING

Summary – Page 3
CLOSURE OPTIONS
For the Allen Steam Station, under the direction of Duke Energy, AECOM developed the following
conceptual closure options that remain under evaluation:
Option 1. Closure-in-Place: Closure-in-Place of AAB and RAB with limited footprint reduction in
western CCR removal areas.

Option 2. Hybrid Option – Excavation of a portion of the ash basins while capping the remainder
of the basins resulting in a reduced closure footprint within the ash basins compared to
Option 1.

Option 4. Closure-by-Removal: Closure-by-Removal and construction of new onsite landfill within
AAB footprint

Option 5. Closure-by-Removal: Closure-by-Removal and disposal of excavated ash in an offsite
landfill

Option 1 consists of excavating ash from the southwestern portion of the RAB to fill and regrade the
northern area of Ash Fill 2 and the area to the north of the RAB Landfill. In addition, ash from the
western portion of the AAB will be excavated and used to fill and regrade the remaining area of the AAB.
This excavation will focus on fingers of the basins closest to residential neighbors, moving the ash
farther from them. Following these excavation and placement activities, the ash basins will 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).
Option 2 consists of excavating ash from both the southwestern and northwestern portions of the RAB
to fill and regrade Ash Fill 2 and the area to the north of the RAB Landfill. In addition, the western and
southeastern portions of the AAB will be excavated and used to fill and regrade the remaining area of
the AAB. This option further reduces/optimizes the footprint of the final AAB closure area in comparison
to Option 1. Following these excavation and placement activities, the ash basins will be capped with an
infiltration barrier/cover system meeting the requirements of the Federal CCR Rule and CAMA. This
option also involves partial removal of the AAB dam.
Option 3 was an alternate hybrid option similar to Option 2 but it consolidated the ash into a footprint in
the corner opposite from Option 2 and against the dam. Option 2 was preferable for the final footprint
location so Option 3 was removed from this updated analysis.
Option 4 consists of the excavation of all ash materials from the RAB and AAB including the ash storage
areas, structural fills, and double-lined landfill constructed within the RAB and the placement of these
excavated materials into a new, on-site, lined landfill system. The new landfill would be built with a
base liner system and an infiltration barrier/cover system meeting the requirements of the Federal CCR
Rule and CAMA. The new onsite landfill would cover an area of approximately 91 acres and would rise to
an elevation approximately 45 feet in height above the current grade. It is proposed that the new
landfill system be located within the area of the current AAB to reduce the material handling and
hauling effort. This option also involves full removal of the RAB and AAB dam. No siting or other studies

Summary – Page 4
have been performed to verify the ability to permit this location but it appears feasible based on limited
review during the options development work.
Option 5 consists of the same elements as Option 4, but the excavated ash materials are to be disposed
in an existing, off-site, lined landfill facility. This option also involves full removal of the RAB and AAB
dams.
Tables 1, 2, and 3 of this report present a tabulated summary of each evaluated closure option,
estimated quantities of ash and soil materials associated with each closure option, and a more detailed
overview of each closure option presented.
Attachment A of this report includes figures depicting conceptual plan drawings and cross
sections/details for each closure option.
The figures included in Attachment A are as follows:
• Figure A1-1 – Option 1 Closure-In-Place Plan View
• Figure A1-2 – Option 1 Closure-In-Place Profile and Section Views
• Figure A2-1 – Option 2 Hybrid 1 Closure Plan View
• Figure A2-2 – Option 2 Hybrid 1 Closure Profile and Section Views
• Figure A4-1 – Option 4 Closure-by-Removal: Closure by Removal and Construction of New Onsite
Landfill within AAB Footprint Plan View
• Figure A4-2 – Option 4 Closure-by-Removal: Closure by Removal and Construction of New Onsite
Landfill within AAB Footprint Profile and Section Views
• Figure A5-1 – Option 5 Closure-by-Removal and Disposal of Excavated Ash in an Offsite Landfill
Closure Plan View
• Figure A5-2 – Option 5 Closure-by-Removal and Disposal of Excavated Ash in an Offsite Landfill
Profile and Section Views
• Figure A6 – Details
Attachment B includes rough order of magnitude (ROM) cost estimates for each closure option.
Attachment C contains the scoring matrix which summarizes the composite scores of the various closure
options, the assumptions of which are outlined in Table 3 for each particular option.
METHODOLOGY
A scoring matrix was prepared to provide consistent evaluation of closure options for various site
locations. This scoring evaluation tool can be found in Attachment C and considers the following
primary criteria:
• Environmental Protection and Impacts
• Cost

Summary – Page 5
• Schedule
• Regional Factors
• Constructability
Rough Order of Magnitude Costs
A rough order of magnitude (ROM) Class 5 cost estimate was prepared for each of the closure options,
based on information and quantities developed during the conceptual design activities. The estimated
costs include construction, permitting, engineering design, post-construction O&M, and groundwater
monitoring. A tabulated summary of the preliminary closure cost estimates is provided below:
Summary of Current ROM Cost Estimates
Option Closure Option Estimated
Construction Cost
Estimated O&M
Cost (30 Years)
1 Closure-in-Place $185,156,251 $63,558,594
2 Hybrid Option 1 $280,723,031 $44,995,340
4
Closure-by-Removal and
Construction of New Onsite Landfill
within AAB Footprint
$558,836,985 $34,596,491
5 Closure-by-Removal and Disposal of
Excavated Ash in an Offsite Landfill $1,229,189,724 $1,813,625

Option 1: Closure-in-Place has the lowest estimated construction cost based on a reasonable balance
between ash excavation volume, final cover area, and geotechnical stabilization needs compared to
other options. Detailed tabulated ROM cost estimates are included in Attachment B.
Schedule
Within the scoring evaluation, estimates of the length of time required to initiate closure activities and
the anticipated construction duration are provided for each option. For the Closure-By-Removal options
(4 and 5), 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 (i.e., initiation time and construction duration), the
Closure-In-Place option (#1) would be expected to be completed in 8.8 years and Hybrid Option 1 (#2) in
10.3 years, while the two Closure-By-Removal options (#4 and #5) are expected to take 22 and 19.7
years, respectively. The two Closure-By-Removal options would extend beyond both the CAMA deadline
of 2029 and the CCR deadline of 2034. The Closure-In-Place option and Hybrid option could be
completed by the CAMA deadline of 2029 if work were to begin in early-2020.
A major driver in the estimated construction durations is the assumed material excavation/movement of
1,000,000 cubic yards/year. As a result, the Closure-By-Removal options have longer construction
durations, as they require the movement of all ash materials, compared to the Hybrid and Closure-In-
Place options.

Summary – Page 6
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 scorings to balance environmental factors, cost and the safety of
workers and the public. The Options Analysis incorporates Duke Energy’s obligation as a regulated utility
to ensure that its closure decisions are protective of the environment and communities, while also being
prudent from a cost-effectiveness perspective.
The analysis considered multiple aspects 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.
The company then combined these elements to provide a weighted sum for each criterion using the
following weights: environmental considerations (30%), cost (35%), schedule (15%), regional/community
factors (15%) and constructability (5%.) Duke Energy placed primary emphasis on environmental factors
and cost, which were approximately equal in weight. When considering all of the criteria and associated
weightings, the environmental considerations have a slightly higher weight than cost with the inclusion
of certain regional/community factors (transportation impact, noise impact, view impact) which are
effectively environmental considerations.
The scoring matrix provided in Attachment C, scores each option on a scale of 0 (least favorable) to 10
(most favorable) for each of the specified criteria. The scores for each option are then summed based
on the specified criterion weighting, resulting in an overall weighted score for each option. The results
of the scoring evaluation for the Allen closure options are summarized in the following table:
Summary of Closure Options Evaluation Scoring
Criterion Options
1 2 4 5
Environmental Protection and Impacts 3.0 2.8 2.4 2.2
Cost 2.8 2.8 2.1 0.7
Schedule 1.5 1.3 0.0 0.5
Regional Factors 1.1 1.2 1.0 0.3
Constructability 0.3 0.0 0.2 0.5
Total Score 8.7 8.0 5.7 4.2

Summary – Page 7
DISCUSSION
The options analysis finds relatively similar rankings for environmental protection and impacts which
considers impacts to groundwater, surface water, and avoidance of greenfield disturbance.
The analysis incorporates the latest groundwater modeling for the Retired Ash Basin and Active Ash
Basin that demonstrates groundwater response patterns are similar in all closure options modeled, but
the times to reach 2L compliance vary. Note that only 3 of the 4 closure options were included in the
current preliminary groundwater modeling; Option 1: Closure-in-Place, Option 2: Hybrid Option 1, and
Option 5: Closure-by-Removal with Offsite Landfill. The Closure-in-Place design simulation indicates
compliance with the 2L standard for boron will be achieved faster than the other closure options,
followed by the Hybrid design and then Closure-by-Removal.
In terms of duration of work and closure time (i.e., initiation time and construction duration), the
Closure-in-Place option (#1) would be expected to be completed in 8.8 years and Hybrid Option 1 (#2) in
10.3 years, while the two Closure-by-Removal options (#4 and #5) are expected to take 22 and 19.7
years, respectively. The two Closure-by-Removal options would extend beyond both the CAMA deadline
of 2029 and the CCR deadline of 2034. They remain in the Options Analysis despite this for full
transparency of the alternatives. The Closure-in-Place option and Hybrid option could be completed by
the CAMA deadline of 2029 if work were to begin in early-2020.
Other aspects considered are regional impacts to the surrounding community related to traffic and
noise generated by each of the options. Traffic to and from the site will occur through the duration for
each option noted above. That will include workers, trucks for deliveries or movement of soil, topsoil,
stone, geosynthetics, etc. For the Closure-in-Place option (#1) and Hybrid option (#2) traffic will be
mingled with typical traffic on the main roads leading to Plant Allen and Canal Road in particular.
Closure-By-Removal option (#5) requires a significant number of trucks entering Highway 273 per work
day over the approx. 17-year excavation/construction period to access the chosen offsite landfill. The
noise generated for each the options would be similar to someone near the site, but the duration of the
work and the exposure to that noise varies directly with the time required for each option and would be
longer for Closure-by-Removal. Along with increased duration and truck trips comes higher levels of
emissions for the Closure-by-Removal option as well.
The Closure-by-Removal with disposal of ash in a new on-site landfill is three times the estimated cost of
the Closure-in-Place option while the Closure-by-Removal with disposal of ash in an off-site landfill is
over six times the estimated cost of the Closure-in-Place option. The Closure-by-Removal options cause
other unnecessary community impacts with little compelling environmental benefit.

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),
Option #1: Closure-In-Place or Option #2: Hybrid were identified as the preferred options that best
balance the various considerations associated with basin closure.

Summary – Page 8

Attachments:
A – Closure Options Figures
B – Closure Options Cost Estimates
C – Closure Options Scoring Matrix and Groundwater Sub-Scoring Worksheet

1

Table 1 – Closure Options Summary
Ash Basin Closure Options Evaluation
Allen Steam Station
Duke Energy

Option Description
1. Closure-in-
Place with
Limited
Footprint
Reduction
 Install stormwater controls.
 Install free water decanting and water treatment system.
 Decant free water.
 Perform interstitial dewatering of ash material as needed to provide
stable working surfaces. Install temporary water treatment system, as
needed.
 Excavate ash from the southwest finger of the RAB, and use the
excavated ash to regrade Ash Fill 2 and the area to the north of the
RAB Landfill. Excavate ash from the western portion of the AAB, and
use the excavated ash to regrade the remaining area of the AAB.
 Backfill excavated areas with soil to promote positive surface water
drainage.
 Construct cover system over the remaining Ash Basin footprint.
 Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA.
2. Hybrid Option
 Install stormwater controls.
 Install free water decanting and water treatment system.
 Decant free water.
 Perform interstitial dewatering of ash material as needed to provide
stable working surfaces. Install temporary water treatment system, as
needed.
 Excavate ash from the southwest finger and northwest finger and Ash
Storage Area within the RAB, and use the excavated ash to fill and
regrade the northern portion of Ash Fill 2 and the area to the north of
the RAB Landfill.
 Excavate ash from the western and southeastern portions of the AAB,
and use the excavated ash to fill and regrade the remaining area of
the AAB. Stack the excavated ash away from the excavation slope.
 Construct a new perimeter berm for the Ash Basin closure areas.
Construct a stabilized slope wedge or Deep Mixing Method (DMM)
wall as needed.
 Backfill excavated areas in the RAB with soil to promote positive
surface water drainage.
 Construct cover system over the remaining Ash Basin footprints.
 Perform partial dam removal and restore excavated areas to stable
and non-erodible condition. Soils obtained from the partial dam
removal will be used as cover material in closure areas.
 Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA.
2
4.Closure-by-
Removal and
Construction of
New Onsite
Landfill within
AAB Footprint
Install stormwater controls.
Install free water decanting and water treatment system.
Decant free water.
Perform interstitial dewatering of ash material as needed to provide
stable working surfaces. Install temporary water treatment system, as
needed.
Partially excavate ash from the AAB within the proposed Onsite
Landfill footprint, construct the required sub base, construct the first
lined cell and start placing ash. Continue the sequence until all ash
from the AAB and RAB is excavated and placed in the proposed
Onsite Landfill. Stack the excavated ash away from the excavation
slope.
Construct cover system over the Onsite Landfill when complete.
Complete dam removal and restore excavated areas to stable and
non-erodible condition. Soils obtained from the dam removal will be
used as cover material for the Onsite Landfill.
Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA.
5. Closure-by-
Removal and
Disposal of
Excavated Ash
in an Offsite
Landfill.
Install stormwater controls.
Install free water decanting and water treatment system.
Decant free water.
Perform interstitial dewatering of ash material as needed to provide
stable working surfaces. Install temporary water treatment system, as
needed.
Excavate ash from the AAB and RAB. Dewater ash sufficiently to
facilitate handling, and transport to an approved Offsite Landfill
assumed to be within a 50-mile radius of the site. Stack the
excavated ash away from the excavation slope. 1,000,000 cubic
yards per year assumed. Transport by truck is assumed due to
limitations of space on site for developing rail infrastructure.
Backfill excavated areas with soil to promote positive surface water
drainage.
Complete dam removal and restore excavated areas to stable and
non-erodible condition.
Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA.

1

Table 2 – Quantity Summary

Ash Basin Closure Options Evaluation
Allen Steam Station
Duke Energy

Item Volume  Units Area 
(Acres) 
Existing Ash
Ash Basin Area (regulatory boundary) NA 293
In Place Ash Volume 19,515,700
16,263,100
Tons
CY 293
Ash Basin Dam Soil Volume 1,650,000 CY NA
Option 1: Closure-in-Place with Limited Footprint Reduction
Ash Volume in Final Closure Footprint 16,263,100 CY 274
Ash Excavation Volume (Excavated Area) 530,000 CY 19
Over Excavation Volume (1 ft.) 31,000 CY 19
Ash Regrading 3,953,000 CY NA
Dam Soil Cut Volume 0 CY NA
Additional Soil Needed (Backfill Excavated Area and
18” Cover Soil) 865,000 CY NA
Additional Topsoil Needed (6” for Final Cover) 215,000 CY 322
Option 2: Hybrid Option
Ash Volume in Final Closure Footprint 16,263,100 CY 164
Ash Excavation Volume (Excavated Area) 4,230,900 CY 103
Over Excavation Volume (1 ft.) 166,000 CY 103
Ash Regrading 6,377,000 CY NA
Dam Soil Cut Volume 740,000 CY NA
Soil Needed (2’ Backfill in Excavated Area and 18”
Cover Soil in Capped Area) 665,000 CY 164
Additional Topsoil Needed (6” for Excavated and
Capped Areas) 194,000 CY 267
Option 4: Closure-by-Removal and Construction of New Onsite Landfill within AAB Footprint
Ash Excavation Volume (Closure by Removal Area) 16,263,100 CY 267
Over Excavation Volume (1 ft.) 473,000 CY 293
Dam Soil Cut Volume 1,650,000 CY NA
Soil Needed (2’ Backfill in Closure-by-Removal Area
+ Onsite Landfill: 2’ Soil Liner + 18” Cover Soil for
Closure Cap)
1,206,000 CY NA
Additional Topsoil Needed (6” over Closure-by-
Removal Area and Onsite Landfill Closure Cap) 246,000 CY 305

2

Option 5: Closure-by-Removal and Disposal of Excavated Ash in an Offsite Landfill
Ash Excavation Volume (Closure-by-Removal Area) 16,263,100 CY 293
Over Excavation Volume (1 ft.) 473,000 CY 293
Dam Soil Cut Volume 1,650,000 CY NA
Soil Needed (2’ Backfill in Closure-by-Removal Area) 947,400 CY 293
Additional Topsoil Needed (6” over Closure-by-
Removal) 237,000 CY 293

*Volumes will be determined as part of the final design if the respective option is selected as the closure
option.

1

Table 3.1 – Option 1 Overview: Closure-In-Place with Limited Footprint Reduction
Ash Basin Closure Options Evaluation
Allen Steam Station
Duke Energy

Subject Description – Option 1
Description
1. Install stormwater controls.
2. Install dewatering/wastewater treatment system.
3. Decant & treat free water.
4. Remove & treat interstitial pore water in ash material as needed to
provide stable working surfaces during construction within the Closure-
In-Place area.
5. Excavate a limited amount of ash from the southwest finger of the RAB,
and use the excavated ash to regrade Ash Fill 2 and the area to the
north of the RAB Landfill. Excavate ash from the western portion of the
AAB, and use the excavated ash to regrade the remaining area of the
AAB.
6. Remove one foot of residual soil in excavated areas.
7. Backfill excavated areas with soil to promote positive surface water
drainage.
8. Construct closure cap over the remaining Ash Basin footprint.
9. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA and CCR.
10. Dam remains in place.
Details
1. Install stormwater run-on controls to divert stormwater from the ash
basin where possible.
2. Design and install temporary wastewater treatment system to manage
dewatering activities and influent (contact) stormwater.
3. Decant & treatment of free water.
4. Removal & treatment of pore water in ash material within the close-in-
place area as necessary for construction and placement of the cap.
5. Regrade the close-in-place area to direct stormwater to the existing
permitted outfall.
6. Backfill excavated areas with soil to promote positive drainage.
Excavate limited quantities of ash from the western areas of the RAB and
AAB, and stack within the eastern Ash Basin. Cut and fill volumes are
expected to be balanced. Estimated total cut and fill volume is 3,953,000
CY in the RAB and AAB. Limited removal of interstitial water may be
needed at certain locations to support access and future placement of
the cover system.
7. Grade closure area and construct cover system over ash basin areas
using soils from onsite borrow source. Total soil cover volume is
estimated to be about 1,080,000 CY based on 2-ft of backfill in excavated
areas and a 2-ft thick soil cover system (in addition to geosynthetics), of
which approximately 215,000 CY is topsoil. The total footprint of the
closure area is 274 acres. Total in-place ash is approximately
19,515,700 tons.

2

Subject Description – Option 1
8. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA and CCR.
9. Decommission temporary wastewater treatment facility.
Environmental
Protection and
Impacts
1. Air emissions offsite (based on miles driven) – NA (not driving offsite).
2. Air emissions onsite (based on volume of material excavated/moved)
from closure implementation – this will be the best option as the schedule
is shorter than other options.
3. Avoidance of greenfield disturbance – On-site borrow area only.
Cost
1. Capital costs = $185,156,251
2. Long-term operations maintenance and monitoring = $2,118,620 per
year over 30 years.
Schedule
1. Initiation time (to begin ash removal) = 30 months (includes
design/permitting and dewatering).
2. Design and permitting = 12 months.
3. Construction = 76 months.
4. Total duration = 106 months = 8.8 years.
5. Post-closure = 30 years.
Regional Factors
1. Plan or potential for beneficial reuse of site – none.
2. Imported soil needs – Onsite soil is assumed to accommodate general
soil needs. Topsoil will need to be imported.
3. CCR beneficial reuse - None
4. Transportation impact (based on miles driven) – No offsite miles. Onsite
transportation limited within Ash Basin footprint – Minimal construction
compared to other options.
5. Noise impact due to on-site activity (proximity to neighbors is
approximately equivalent for all options; therefore, scoring is based on
construction duration).
6. Visual impact (based on final height of storage facility, land uses within
the viewshed) – Minimal increase in elevation for positive drainage.
Constructability
1. Relative to other options, this option is easier to construct due to the
lower amount of ash that needs to be moved and shorter construction
duration.
2. No deep excavations within the ash are necessary.
3. Dewatering will include free water removal and treatment and (as needed
to provide a stable working surface) interstitial pore water removal and
treatment as part of ash excavation and cover system placement.

3

-
Table 3.2 – Option 2 Overview: Hybrid Option
Ash Basin Closure Options Evaluation
Allen Steam Station
Duke Energy

Subject Description – Option 2
Description
1. Install stormwater controls.
2. Install dewatering/wastewater treatment system.
3. Decant & treat free water.
4. Remove & treat interstitial pore water in ash material as needed to
provide stable working surfaces during construction within the Closure-
In-Place area.
5. Excavate ash from the southwest finger and northwest finger of the
RAB and the Ash Storage Areas within the RAB, and use the
excavated ash to fill and regrade Ash Fill 2 and the area to the north of
the RAB Landfill.
6. Excavate ash from the western and southeastern portions of the AAB,
and use the excavated ash to fill and regrade the remaining area of the
AAB. Stack the excavated ash away from the excavation slope.
7. Remove one foot of residual soil in excavated area.
8. Install stabilized ash wedge as needed
9. Backfill excavated areas with soil to promote positive surface water
drainage.
10. Construct cover system over the remaining Ash Basin footprint.
11. Perform partial dam removal and restore excavated areas to stable and
non-erodible condition. Soils obtained from the partial dam removal will
be used as cover material in the Closure-In-Place areas.
12. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA and CCR.
Details
1. Install stormwater run-on controls to divert stormwater from the ash
basin where possible.
2. Design and install temporary wastewater treatment system to manage
dewatering activities and influent (contact) stormwater.
3. Decant & treatment of free water.
4. Dewatering of excavated ash material within ash basin waste boundary.
5. Excavate the southwest finger and northwest finger of the RAB and the
Ash Storage Areas within the RAB. Excavate the western and
southeastern portions of the AAB. Stack the excavated ash away from
the excavation slope. Ash excavation volume estimated to be
approximately 4,230,900 CY.
6. Construct new perimeter berm for the hybrid closure area. Construct a
stabilized slope wedge or Deep Mixing Method (DMM) wall as needed.
7. Partially remove dam in the southeastern section of the AAB and restore
excavated areas to stable and non-erodible condition. Final volume of
soil to be removed from the dam is estimated to be approximately
740,000 CY.

4

Subject Description – Option 2
8. Grade closure area and construct closure cap over the Closure-In-Place
area using onsite borrow sources. Total backfill volume is estimated to
be about 333,000 CY, which will be obtained from onsite sources. Total
soil cover volume is estimated to be about 442,000 CY based on a 2-ft
thick soil cover system (in addition to geosynthetics), of which
approximately 111,000 CY is topsoil. Total 2-D footprint of the closure
area is 190 acres. Total closed contained ash volume is approximately
16,263,100 CY.
9. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA.
Environmental
Protection and
Impacts

1. Air emissions offsite (based on miles driven) – NA (not driving offsite).
2. Air emissions onsite (based on volume of material excavated/moved)
from closure implementation – This will be better than most of the other
options, but not as good as Option 1.
3. Avoidance of greenfield disturbance – On-site borrow area only.
Cost
1. Capital costs = $280,723,031
2. Long-term operations maintenance and monitoring = $1,499,845 per
year for 30 years.
Schedule
1. Initiation time (to begin ash removal) = 36 months (includes dewatering
and design/permitting, and is a function of the assumed DMM
wall/stabilization construction).
2. Design and permitting = 18 months.
3. Construction = 88 months
4. Total duration = 124 months = 10.3 years.
5. Post-closure = 30 years
Regional Factors
1. Plan or potential for beneficial reuse of site – Partially restore to nature
and use for hybrid closure footprint.
2. Imported soil needs – Reuse dam removal soil.
3. CCR beneficial reuse - None
4. Transportation impact (based on miles driven) – No offsite miles.
Onsite limited within ash basin footprint.
5. Noise impact due to on-site activity (proximity to neighbors is
approximately equivalent for all options; therefore, scoring is based on
construction duration).
6. Visual impact (based on final height of storage facility, land uses within
the viewshed) – minimal.
Constructability
1. Construction can be more challenging than other options.
2. Deep excavations within the ash will require stabilization.
3. Dewatering will include free water removal and treatment and (as needed
to provide a stable working surface) interstitial pore water removal and
treatment as part of ash excavation and cover system placement.

5

Table 3.4 – Option 4 Overview: Closure-by-Removal and Construction of New
Onsite Landfill within AAB Footprint
Ash Basin Closure Options Evaluation
Allen Steam Station
Duke Energy

Subject Description – Option 4
Description
1. Install stormwater controls
2. Install dewatering/wastewater treatment system
3. Decant & treat free water.
4. Remove & treat interstitial pore water in ash material as needed to
provide stable working surfaces during construction within the Closure-
by-Removal area.
5. Install stabilized ash wedge or another feature.
6. Partially excavate ash from the AAB within the proposed Onsite Landfill
footprint, construct the first lined cell and start placing ash.
7. Remove one foot of residual soil in Closure-By-Removal area.
8. Construct cover system over the Onsite Landfill when complete.
9. Complete dam removal and restore excavated areas to stable and non-
erodible condition.
10. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA and CCR.
Details
1. Install stormwater run-on controls to divert stormwater from the ash
basin where possible.
2. Design and install temporary wastewater treatment system to manage
dewatering activities and influent (contact) stormwater.
3. Decant & treatment of free water.
4. Dewatering of excavated ash material within ash basin waste boundary.
5. Partially excavate ash from the AAB within the proposed Onsite Landfill
footprint. Stack the excavated ash away from the excavation slope.
6. Construct perimeter berm for the landfill area as part of the sequenced
cell construction. Construct a stabilized slope wedge or Deep Mixing
Method (DMM) wall as needed.
7. Construct the first cell of the Onsite Landfill.
8. Excavate ash from the remainder of the AAB and the RAB. Total ash
excavation volume estimated to be approximately 16,263,100 CY.
9. Remove one foot of residual soil in Closure-By-Removal area.
10. Backfill and grade excavated areas with 2-ft of soil to promote positive
drainage.
11. Place excavated ash and soil within the constructed cell of the proposed
Onsite Landfill.
12. Constructed lined Onsite Landfill in the excavated AAB footprint is
estimated to be 91 acres. Total liner soil volume is estimated to be about
293,000 CY based on a 2-ft thick soil liner system (in addition to
geosynthetics). Total soil cover volume is estimated to be about 293,000
CY based on a 2-ft thick soil cover system (in addition to geosynthetics),
of which approximately 73,000 CY is topsoil. Cover soil other than topsoil
will be obtained from onsite sources.

6

Subject Description – Option 4
13. Complete dam removal and restore excavated areas to stable and non-
erodible condition. Final volume of soil to be removed from the dam is
estimated to be approximately 1,650,000 CY.
14. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA and CCR.
Environmental
Protection and
Impacts
1. Air emissions offsite (based on miles driven) – NA (not driving offsite).
2. Air emissions onsite (based on volume of material excavated/moved)
from closure implementation – this will be fourth best option based on
construction work.
3. Avoidance of greenfield disturbance – On-site borrow area only.
Cost
1. Capital costs ≈ $558,836,985
2. Long-term operations maintenance and monitoring ≈ $1,153,216 per
year over 30 years.
Schedule
1. Initiation time (to begin ash placement in landfill) = 54 months (includes
dewatering and design and permitting).
2. Design and permitting = 24 months.
3. Construction = 210 months.
4. Total duration = 264 months = 22 years.
5. Post-closure = 30 years.
Regional Factors
1. Plan or potential for beneficial reuse of site – Partially restore to natural
setting and use for landfill footprint.
2. Imported soil needs – Reuse dam removal soil for common soil needs.
Approximately 70,000 CY of topsoil needed for final cover system.
Potential for additional soil needs to meet hydraulic conductivity
requirements of landfill.
3. CCR beneficial reuse - None
4. Transportation impact (based on miles driven) – No offsite miles. Onsite
transportation limited within Ash Basin footprint.
5. Noise impact due to on-site activity (proximity to neighbors is
approximately equivalent for all options; therefore, scoring is based on
construction duration).
6. Visual impact (based on final height of landfill inside of basin area) is
minor.
Constructability
1. Most difficult option to construct due to complex construction sequencing
and very large quantities of ash per year that need to be moved.
2. Deep excavations within the ash will require stabilization.
3. Landfill to be constructed adjacent to deep ash cut.
4. Dewatering will include free water removal and pore water removal as
part of ash excavation.

7

Table 3.5 – Option 5 Overview: Closure-By-Removal and Disposal of Excavated
Ash in an Offsite Landfill
Ash Basin Closure Options Evaluation
Allen Steam Station
Duke Energy

Subject Description – Option 5
Description
1. Install stormwater controls
2. Install dewatering/wastewater treatment system
3. Decant & treat free water.
4. Remove & treat interstitial pore water in ash material as needed to
provide stable working surfaces during construction within the Closure-
by-Removal area.
5. Excavate ash from the AAB and RAB, moisture condition to be ready
for hauling, to dispose of in an approved Offsite Landfill assumed to be
within a 50-mile radius of the site. Stack the excavated ash away from
the excavation slope. Transport by truck is assumed due to limitations
of space on site for developing rail infrastructure.
6. Remove one foot of residual soil in the excavated area.
7. Backfill excavated areas with soil to promote positive surface water
drainage.
8. Complete dam removal and restore excavated areas to stable and non-
erodible condition.
9. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA and CCR.
Details
1. Install stormwater run-on controls to divert stormwater from the ash
basin where possible.
2. Design and install temporary wastewater treatment system to manage
dewatering activities and influent (contact) stormwater.
3. Decant & treatment of free water.
4. Dewatering of excavated ash material within ash basin waste boundary.
5. Excavate the ash from the Ash Basins and moisture condition as needed
to prepare for offsite transport. Ash excavation volume estimated to be
approximately 16,263,100 CY.
6. Haul and dispose of ash in an Offsite Landfill assumed to be within a 50
-mile radius of the site.
7. Complete dam removal and restore excavated areas to stable and non-
erodible condition. Final volume of soil to be removed from the dam is
estimated to be approximately 1,650,000 CY.
8. Conduct groundwater corrective action and long-term monitoring
pursuant to CAMA and CCR.
Environmental
Protection and
Impacts
1. Air emissions offsite (based on miles driven) greater impacts than other
options since it is only option that requires offsite transport of ash.
2. Air emissions onsite (based on volume of material excavated/moved)
from closure implementation – This will have increased impacts due to
excavation and hauling as well as relatively long construction duration.

8

Subject Description – Option 5
3. Greenfield disturbance – No impact onsite. Impacts may be offsite and
are not known at this time. Assumed the total landfill acreage of 91 acres
offsite, as greenfield disturbance.
Cost
1. Capital costs ≈ $1,229,189,724
2. Long-term operations maintenance and monitoring ≈ $60,454 per year
over 30 years.
Schedule
1. Initiation time (to begin ash removal) = 36 months (includes dewatering
and design and permitting).
2. Design and permitting = 24 months.
3. Construction = 200 months.
4. Total duration = 236 months = 19.7 years.
5. Post-closure = 30 years.
Regional Factors
1. Plan or potential for beneficial reuse of site – restore to natural setting.
2. Imported soil needs – None.
3. CCR beneficial reuse – None.
4. Transportation impact (based on miles driven) – Significant offsite miles.
5. Noise impact due to on-site activity (proximity to neighbors is
approximately equivalent for all options; therefore, scoring is based on
construction duration).
6. Visual impact (based on final height of storage facility, land uses within
the viewshed) – None onsite.
Constructability
1. Relatively easy to construct, but requires large quantities of ash per year
to be moved.
2. Excavation can be in layers and safer than other options.
3. Dewatering will include free water removal and pore water removal as
part of ash excavation.

Attachment A

Figure A1-1.dwg
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DATE:
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CHKD:
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APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
FIGURE A1-1
CLOSURE OPTION #1
CLOSURE IN PLACE - PLAN VIEW
1"=300'
LEGEND:
NOTES:
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JOB NO:
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CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
Appendix B2.dwg
FIGURE A1-2
CLOSURE OPTION #1
CLOSURE IN PLACE - SECTIONS
1"=150'
HORIZ. SCALE
CROSS SECTION A - CLOSURE IN PLACE FINAL GRADESA
21
VERT. SCALE
CROSS SECTION B - CLOSURE IN PLACE FINAL GRADESB
21
CROSS SECTION C - CLOSURE IN PLACE FINAL GRADESC
21
LEGEND
INACTIVE ASH BASIN ASH STORAGE AREA
ASH FILL 2
ASH FILL 1 RAB LANDFILL
ACTIVE ASH BASIN
LAKE WYLIE/
CATAWBA RIVER
LAKE WYLIE/
CATAWBA RIVER
RAB LANDFILL
ACTIVE ASH BASIN
NOTES:
10 20 30TENTHS0
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JOB NO:
DATE:
SCALE:DES:
CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
Figure A2-1.dwg
FIGURE A2-1
CLOSURE OPTION #2
HYBRID OPTION 1- PLAN VIEW
1"=300'
NOTES:
LEGEND:
10 20 30TENTHS0
2 3 4 5 7 86
A
1 2 3
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DWG SIZE REVISION
FOR
DRAWING NO.
FILENAME:
DWG TYPE:
JOB NO:
DATE:
SCALE:DES:
CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
Appendix B3.dwg
FIGURE A2-2
CLOSURE OPTION #2
HYBRID OPTION 1- SECTIONS
1"=150'
HORIZ. SCALE
CROSS SECTION A - HYBRID OPTION 1 FINAL GRADESA
21
VERT. SCALE
CROSS SECTION B - HYBRID OPTION 1 FINAL GRADESB
21
CROSS SECTION C - HYBRID OPTION 1 FINAL GRADESC
21
HORIZ. SCALE
VERT. SCALE
INACTIVE ASH BASIN ASH STORAGE AREA
ASH FILL 2
ASH FILL 1 RAB LANDFILL
ACTIVE ASH BASIN
LAKE WYLIE/
CATAWBA RIVER
LAKE WYLIE/
CATAWBA RIVER
RAB LANDFILL
ACTIVE ASH BASIN
LEGEND
NOTES
10 20 30TENTHS0
2 3 4 5 7 86
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1 2 3
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DRAWING NO.
FILENAME:
DWG TYPE:
JOB NO:
DATE:
SCALE:DES:
CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
Figure A4-1.dwg
FIGURE A4-1
CLOSURE OPTION #4
CLOSURE BY REMOVAL ONSITE LANDFILL - PLAN VIEW
1"=300'
NOTES:
LEGEND:
10 20 30TENTHS0
2 3 4 5 7 86
A
1 2 3
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DWG SIZE REVISION
FOR
DRAWING NO.
FILENAME:
DWG TYPE:
JOB NO:
DATE:
SCALE:DES:
CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
Appendix B5.dwg
FIGURE A4-2
CLOSURE OPTION #4
CLOSURE BY REMOVAL ONSITE LANDFILL - SECTIONS
1"=150'
CROSS SECTION A - CLOSURE BY REMOVAL WITH ONSITE LANDFILL FINAL GRADESA
21
CROSS SECTION B - CLOSURE BY REMOVAL WITH ONSITE LANDFILL FINAL GRADESB
21
CROSS SECTION C - CLOSURE BY REMOVAL WITH ONSITE LANDFILL FINAL GRADESC
21
INACTIVE ASH BASIN ASH STORAGE AREA
ASH FILL 2
ASH FILL 1 RAB LANDFILL
ACTIVE ASH BASIN
LAKE WYLIE/
CATAWBA RIVER
RAB LANDFILL
ACTIVE ASH BASIN
HORIZ. SCALE
VERT. SCALE
LEGEND
NOTES:
HORIZ. SCALE
VERT. SCALE
NOTES:
570
565
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JOB NO:
DATE:
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CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
Figure A5-1.dwg
FIGURE A5-1
CLOSURE OPTION #5
CLOSURE BY REMOVAL OFFSITE LANDFILL- PLAN
1"=300'
NOTES:
LEGEND:
10 20 30TENTHS0
2 3 4 5 7 86
A
1 2 3
A
BB
C
D
7 8623456
c
DWG SIZE REVISION
FOR
DRAWING NO.
FILENAME:
DWG TYPE:
JOB NO:
DATE:
SCALE:DES:
CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CLOSURE OPTIONS EVALUATION
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60572629
10/26/2018
1 11
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG DMB
SSK
APPD
ENGR
JDM
Appendix B6.dwg
FIGURE A5-2
CLOSURE OPTION #5
CLOSURE BY REMOVAL OFFSITE LANDFILL - SECTIONS
1"=150'
CROSS SECTION A - CLOSURE BY REMOVAL WITH OFFSITE LANDFILLA
21
CROSS SECTION B - CLOSURE BY REMOVAL WITH OFFSITE LANDFILLB
21
CROSS SECTION C - CLOSURE BY REMOVAL WITH OFFSITE LANDFILLC
21
INACTIVE ASH BASIN ASH STORAGE AREA
ASH FILL 2
ASH FILL 1 RAB LANDFILL
ACTIVE ASH BASIN
LAKE WYLIE/
CATAWBA RIVER
RAB LANDFILL
ACTIVE ASH BASIN
HORIZ. SCALE
VERT. SCALE
LEGEND
NOTES:
HORIZ. SCALE
VERT. SCALE
NOTES:
570
565
VEGETATIVE COVER
6 IN MIN.
18 IN MIN.
ASH MATERIAL
COMPACTED SOIL LAYER
(KV<1x10-5 CM/SEC)
-
VEGETATIVE COVER SOIL
VEGETATIVE COVER
GEOCOMPOSITE
DRAINAGE LAYER
FLEXIBLE
MEMBRANE
LINER (FML)
2 FT
MIN.
ASH MATERIAL
VEGETATIVE COVER SOIL
GEOCOMPOSITE
DRAINAGE LAYER
SUBGRADE
SEASONAL HIGH
GROUNDWATER
FLEXIBLE MEMBRANE
LINER (FML)
5 FT. MIN.
2 FT MIN.
EX. SUBSURFACE SOILS
OR SOIL FILL
ASH MATERIAL
-
-7
COMPACTED SOIL LAYER
(KV<1x10-7 CM/SEC)
FLEXIBLE MEMBRANE LINER (FML)
GEOCOMPOSITE
DRAINAGE LAYER
SUBGRADE
SEASONAL HIGH
GROUNDWATER
GEOSYNTHETIC CLAY LINER
(GCL)
5 FT. MIN
1 FT MIN.
EX. SUBSURFACE SOILS
OR SOIL FILL
ASH MATERIAL
PREPARED SUBGRADE
ALTERNATE ASH BASIN CLOSURE CAP SYSTEM
N.T.S
ALTERNATE LANDFILL LINER SYSTEM
N.T.S
STANDARD ASH BASIN CLOSURE CAP SYSTEM
N.T.S
STANDARD LANDFILL LINER SYSTEM
N.T.S
NOTE:
EITHER STANDARD ASH BASIN CLOSURE AND CAP SYSTEM OR ALTERNATE ASH BASIN CLOSURE AND CAP SYSTEM WILL BE USED IN:
·CLOSURE IN-PLACE OPTION
·HYBRID CLOSURE OPTION - 1
·HYBRID CLOSURE OPTION -2
LANDFILL COVER SYSTEM WILL BE DEVELOPED BASED ON SELECTED LINER SYSTEM
NOTE:
EITHER STANDARD LANDFILL LINER SYSTEM OR ALTERNATE LANDFILL LINER SYSTEM WILL BE USED IN:
·ONSITE LANDFILL INSIDE EXCAVATED ASH BASIN
10 20 30TENTHS0
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DATE:
SCALE:DES:
CHKD:
ENGR:
APPD:
22.0"x34.0"
ANSI D
SEAL
DFTR:
DUKE ENERGY
CQA PLAN
GASTON COUNTY, NORTH CAROLINA
ALLEN STEAM STATION
60432103
3/31/2016
A AA
1"=300'
NOT FOR CONSTRUCTION
DRAFT
TITLE
.DWG
SSK
Appendix B7.dwg
FIGURE A6
CLOSURE OPTIONS
CAP AND LINER DETAILS
SSK

Attachment B

PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Cost Summary 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:CALCULATION SHEETAAB & RAB Closure in Place 60572629ACTIVITY:CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 DMB 10/26/2018 JDMCost (2018 Dollars)$4,989,882$55,796,268$25,933,670$59,085,180$36,451,250$2,900,000$185,156,251Cost (2018 Dollars)$15,672,150$30,552,282$11,556,108$5,778,054$63,558,594$248,714,845Closure TasksMobilization / Site Prep CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYPreliminary Project Costs SheetsCost Summary: Closure in Place Cost Estimate for CCR Surface ImpoundmentEngineering Costs (10%)Total Post-Closure of CCR Impoundment = Total Closure & Post-Closure of CCR Impoundment Cost = ALLEN OPTION 1 -- CLOSURE IN PLACEClosure & Post Closure Cost SummaryPost-Closure Tasks Groundwater Monitoring Operations & Maintenance (O&M)Contingency (25%)Total Closure Cost of CCR Impoundment = Dewatering / Earthwork / Subgrade Prep.Closure System ConstructionStormwater Management / E&S Controls / Site RestorationContingency (25%)Engineering Support (Design and CQA)
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Cost Summary 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:AAB & RAB Closure in Place 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 DMB 10/26/18 JDM2018Not Used293262931916,263,08325,694INSTALLED IMPOUNDMENT TASKITEM UNIT QUANTITY UNIT COST CLOSURE COSTMOBILIZATION / SITE PREP1 MOBILIZATION LS 1 $1,472,327 $1,472,3272 ABANDON OUTLET STRUCTURES / PIPING LS 2 $200,000 $400,0003 REMOVAL & FILTRATION OF FREE WATER MONTHS 30.0 $103,919 $3,117,555DEWATERING / EARTHWORK / SUBGRADE PREP4 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 76.0 $225,832 $17,163,2325 RING DRAIN INSTALLATION L.F. 25,694 $58.00 $1,490,252Linear feet around the proposed cap.6 ASH REGRADING TO ESTABLISH CROWN CY 3,953,000 $9.24 $36,525,720.007 OVER EXCAVATE SOIL FROM CLOSURE BY REMOVAL ARE CY 30,874 $10.00 $308,736.308 PERIMETER DITCH / TEMP. DIVERSION BERM GRADING L.F. 25,694 $12.00$308,328CLOSURE SYSTEM CONSTRUCTION9 FLEXIBLE MEMBRANE LINER (FML) SQ. FT. 11,854,016 $0.42 $4,978,68710 GEOCOMPOSITE DRAINAGE LAYER SQ. FT. 11,854,016 $0.60 $7,112,40911 GEOSYNTHETIC CLAY LINER (GCL) SQ. FT. 0 $0.72 $012 18" PROTECTIVE COVER SOIL CY 598,688 $13.00 $7,782,940CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsACTIVITY:Closure in Place Cost Estimate for CCR Surface Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYCLOSURE SYSTEM CONSTRUCTIONDEWATERING / EARTHWORK / SUBGRADE PREPMOBILIZATION/SITE PREPQuantity of earthwork (cut-to-fill) using existing ash to achieve min. 2% slope prior to installation of closure system. Quantity calculated using AutoCAD.18 inches of common soil placed over Closure in Place area (assume onsite soils available).construction timeModify existing outlet structures and piping.Linear feet around the perimeter of impoundment.Flexible membrane liner placed over Closure in Place area. Assume quantity needed is 10% more than Closure in Place area.Geocomposite drainage layer placed over Closure in Place area. Assume quantity needed is 10% more than Closure in Place area.not usedAssume 1 foot of additional material to be removed over total Closure by Removal impoundment area.AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)NOTESinitiation timeEX. AREA OF RAB LANDFILL (LIMITS OF LINER)Mob/Demob & insurance: (1% of Total EPC Bid Priceincludes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup).CLOSURE IN PLACE ESTIMATED COSTSTOTAL IMPOUNDMENT AREA (AC)VOLUME OF ASH IN IMPOUNDMENT (CY)PERIMETER OF IMPOUNDMENT (L.F.)CLOSURE BY REMOVAL AREA (BUFFER AREA) (AC)11/13/20182 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Cost Summary 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:AAB & RAB Closure in Place 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 DMB 10/26/18 JDM2018Not Used293262931916,263,08325,694INSTALLED IMPOUNDMENT TASKITEM UNIT QUANTITY UNIT COST CLOSURE COSTCALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsACTIVITY:Closure in Place Cost Estimate for CCR Surface Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYAREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)NOTESEX. AREA OF RAB LANDFILL (LIMITS OF LINER)CLOSURE IN PLACE ESTIMATED COSTSTOTAL IMPOUNDMENT AREA (AC)VOLUME OF ASH IN IMPOUNDMENT (CY)PERIMETER OF IMPOUNDMENT (L.F.)CLOSURE BY REMOVAL AREA (BUFFER AREA) (AC)13 6" TOPSOIL CY 199,563 $13.00 $2,594,31314 COMPACTED LOW PERM. SOILS (Kv<1x10^-5 cm/sec) CY 266,563 $13.00 $3,465,321STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION15 EROSION AND SEDIMENT CONTROL ACRE 293 $2,000 $586,00016 6" TOPSOIL CY 15,437 $13.00 $200,67917 STORMWATER MANAGEMENT / CHANNELS / LET-DOWNS L.F. 77,082 $742 $57,194,84418 SEED / FERTILIZE / MULCH ACRE 293 $3,767 $1,103,658Assume total area to be restored will require site erosion and sediment control.Assume total area to be restored will be mulched, fertilized, and seeded.STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATIONAssume rip-rap lined stormwater conveyance channels and rip-rap lined let-downs off of cap. Quantity assumed at 3 times perimeter.6 inches of topsoil (obtained offsite) placed over CbR areas.Backfill Excavation Areas (not including 6" of topsoil)6 inches of topsoil (obtained offsite) placed over total impoundment area.11/13/20183 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Cost Summary 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:AAB & RAB Closure in Place 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 DMB 10/26/18 JDM2018Not Used293262931916,263,08325,694INSTALLED IMPOUNDMENT TASKITEM UNIT QUANTITY UNIT COST CLOSURE COSTCALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsACTIVITY:Closure in Place Cost Estimate for CCR Surface Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYAREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)NOTESEX. AREA OF RAB LANDFILL (LIMITS OF LINER)CLOSURE IN PLACE ESTIMATED COSTSTOTAL IMPOUNDMENT AREA (AC)VOLUME OF ASH IN IMPOUNDMENT (CY)PERIMETER OF IMPOUNDMENT (L.F.)CLOSURE BY REMOVAL AREA (BUFFER AREA) (AC)CONTINGENCY / ENGINEERING SUPPORTCONTINGENCY (25%) LS 1 $36,451,250 $36,451,250ENGINEERING SUPPORT (DESIGN & CQA) LS 1 $2,900,000 $2,900,000POST-CLOSURE 19 GROUNDWATER MONITORING ANNUAL 30 $522,405 $15,672,15020 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $1,018,409 $30,552,282CONTINGENCY / ENGINEERING COSTCONTINGENCY (25%) LS 1 $11,556,108.00 $11,556,108.00ENGINEERING COST (10%) LS 1 $5,778,054.00 $5,778,054.00TOTAL$248,714,845CONTINGENCY / ENGINEERING COSTAnnual groundwater monitoring costs for each CCR impoundment are based on current groundwater monitoring system.Annual O&M costs are $3475/acre for the total impoundment area.POST-CLOSURE CONTINGENCY / ENGINEERING SUPPORT11/13/20184 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECTPLANT NAME: CLOSURE TYPE: SHEET REV. NO. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYDuke Allen CCR Rule & CAMA Compliant Close-in-Place Assumptions 3SUBJECTIMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.AAB & RAB Closure in Place 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 1 DMB 10/26/18 JDM12345678910111213KEY 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.Preliminary Project Costs SheetsACTIVITYClose-in-Place AssumptionsCALCULATION SHEETGroundwater 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 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 minimum top slopes of 2%, assume existing ash will be utilized to establish crown. 11/13/20185 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Cost Summary 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:CALCULATION SHEETAAB & RABHybrid Option 60572629ACTIVITY:CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 2 DMB 10/26/2018 JDMCost (2018 Dollars)$6,373,526$114,602,371$80,243,637$0$12,447,588$7,311,304$55,244,606$4,500,000$280,723,031Cost (2018 Dollars)$15,672,150$17,051,734$8,180,971$4,090,485$44,995,340$1,499,844.67 for 30yrs$325,718,371Engineering 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%)Closure TasksMobilization / Site Prep / DemobilizationEngineering Support (Design & CQA)ALLEN OPTION 2 -- HYBRID OPTION Closure & Post Closure Cost SummaryDewatering / Earthwork for Closure in PlaceClosure System ConstructionStormwater Management / E&S Controls / Site Restoration CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYPreliminary Project Costs SheetsCost Summary: Hybrid Option 1 Cost Estimate for CCR Surface ImpoundmentContingency (25%)Total Closure Cost of CCR Impoundment = Dewatering / Excavation for Closure by Removal / Convey MaterialLateral Expansion Areas11/13/20181 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Hybrid Costs 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD:AECOM JOB NO.:AAB & RAB Hybrid Option 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 2 DMB 10/26/18 JDM2018Not Used267Not Used26726.47216410312,170,1004,230,90014,805,95119,7833,700INSTALLED IMPOUNDMENTTASKITEM UNIT QUANTITY UNIT COST CLOSURE COSTMOBILIZATION / SITE PREP / DEMOBILIZATION1 MOBILIZATION / DEMOBILIZATION LS 1 $2,232,460 $2,232,4602 REMOVAL OF OUTLET STRUCTURES / PIPING LS 2 $200,000 $400,0003 REMOVAL & FILTRATION OF FREE WATER MONTHS 36.0 $103,919 $3,741,066DEWATERING / EXCAVATION FOR CLOSURE BY REMOVAL / CONVEY MATERIAL4REMOVAL & TREATMENT OF PORE WATER WITHIN ASH IN CLOSURE BY REMOVAL AREAMONTHS 88.0 $225,832 $19,873,2165 EXCAVATE ASH FOR CLOSURE BY REMOVAL / STOCKPILE ASHCY4,230,900 $8.00 $33,847,2006EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH TO CLOSURE IN PLACE AREACY2,635,851 $8.43 $22,220,2217OVER EXCAVATE SOIL FROM CLOSURE BY REMOVAL AREA / LOAD / HAUL CCR-IMPACTED SOIL TO CLOSURE IN PLACE AREACY166,173 $10.00 $1,661,7338DEEP MIXING METHOD (DMM) WALL TO STABILIZE CUT-SLOPE AT CLOSURE IN PLACE / CLOSURE BY REMOVAL INTERFACEL.F. 3,700 $10,000 $37,000,0009 EXCAVATE / LOAD / HAUL CCR MATERIAL (OFF-SITE)CY0 $57 $010 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFF-SITE)CY0 $57 $0DEWATERING / EARTHWORK FOR CLOSURE IN PLACE11 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 0.0 $225,832$012SPREAD AND COMPACT MATERIAL FROM CLOSURE BY REMOVAL AREACY2,635,851 $7.56 $19,927,03113 ASH REGRADING TO ESTABLISH CROWN CY 6,377,900 $9.24 $58,931,79614 RING DRAIN INSTALLATION L.F. 19,783 $58 $1,147,414 Linear feet around the close-in-place area15 PERIMETER DITCH / TEMP. DIVERSION BERM GRADING L.F. 19,783 $12 $237,396AREA 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 CLOSURE IN PLACE / CLOSURE BY REMOVAL INTERFACE (L.F.)HYBRID OPTION ESTIMATED COSTSinclude if applicableAVG. 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 SheetsHybrid Option Cost Estimate for CCR Surface Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY:TOTAL IMPOUNDMENT AREA (AC)EX. AREA OF RAB LANDFILL (LIMITS OF LINER)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 for AAB. Structure will be modified in RAB.include if applicableLinear feet around the perimeter of impoundment.This cost already accounted for in Item 4Quantity of earthwork (cut-to-fill) using existing ash to achieve min. 2% slope prior to installation of closure system. Quantity calculated using AutoCAD.Spread dewatered ash excavated from Closure by Removal area in thin lifts over close-in-place area. Quantity takes into consideration reduction of volume due to dewatering of ash down to 30% moisture content.PERIMETER OF CLOSED IN PLACE IMPOUNDMENT (L.F.)TOTAL (FINAL) ASH VOLUME TO BE CLOSED IN PLACE (CY)DEWATERING / EARTHWORK FOR CLOSURE IN PLACEAssume 1 foot of additional material to be removed over total Closure by Removal impoundment area.Step 1: Start dewatering 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 Closure in Place area. Quantity takes into consideration reduction of volume due to dewatering of ash down to 30% moisture content.Mob/Demob & insurance: (1% of Total EPC Bid Priceincludes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup).Based on Initiation time11/13/20182 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Hybrid Costs 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD:AECOM JOB NO.:AAB & RAB Hybrid Option 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 2 DMB 10/26/18 JDM2018Not Used267Not Used26726.47216410312,170,1004,230,90014,805,95119,7833,700INSTALLED IMPOUNDMENTTASKITEM 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 CLOSURE IN PLACE / CLOSURE BY REMOVAL INTERFACE (L.F.)HYBRID OPTION 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 SheetsHybrid Option Cost Estimate for CCR Surface Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY:TOTAL IMPOUNDMENT AREA (AC)EX. AREA OF RAB LANDFILL (LIMITS OF LINER)NOTESPERIMETER OF CLOSED IN PLACE IMPOUNDMENT (L.F.)TOTAL (FINAL) ASH VOLUME TO BE CLOSED IN PLACE (CY)LATERAL EXPANSION AREAS16 LATERAL EXPANSION AREAS AC 0 $300,000 $0CLOSURE SYSTEM CONSTRUCTION17 FLEXIBLE MEMBRANE LINER (FML) SQ. FT. 6,567,189 $0.42 $2,758,21918 GEOCOMPOSITE DRAINAGE LAYER SQ. FT. 6,567,189 $0.60 $3,940,31419 GEOSYNTHETIC CLAY LINER (GCL) SQ. FT. 0 $0.72 $020 18" PROTECTIVE COVER SOIL CY 331,676 $13 $4,311,79121 6" TOPSOIL CY 110,559 $13 $1,437,26422 COMPACTED LOW PERM. SOILS (Kv<1x10^-5 cm/sec) CY 0 $13 $0STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION23 PERMANENT RIPRAP STORMWATER CHANNELS TON 7,250 $50 $362,50024 SITE EROSION AND SEDIMENT CONTROL ACRE 267 $2,000 $533,06025 BACKFILL AND REGRADING OF CLOSURE BY REMOVAL AREA CY 333,033 $13$4,329,43326 TOPSOIL CY 83,258 $13 $1,082,35827 SEED / FERTILIZE / MULCH ACRE 267 $3,767 $1,003,952CONTINGENCY / ENGINEERING SUPPORTCONTINGENCY (25%) LS 1 $55,244,606 $55,244,606.00ENGINEERING SUPPORT (DESIGN & CQA) LS 1 $4,500,000 $4,500,000.00POST-CLOSURE 28 GROUNDWATER MONITORING ANNUAL 30 $522,405 $15,672,15029 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $568,391 $17,051,734CONTINGENCY / ENGINEERING COSTCONTINGENCY (25%) LS 1 $8,180,971 $8,180,971.00Assume total area to be restored will require site erosion and sediment control.Assume 6-inches of topsoil needed (obtained offsite) to establish vegetative stabilization over total Closure by Removal areaAssume 2 feet of additional soil material (obtained onsite) graded over total Closure by Removal area.Annual groundwater monitoring costs for each CCR impoundment are based on current groundwater monitoring systemPOST-CLOSURE STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATIONAssume total area of disturbance will be mulched, fertilized, and seeded.CONTINGENCY / ENGINEERING COSTCONTINGENCY / ENGINEERING SUPPORTAssume 10,000 lf x 10 ft wide x 1 ft thick, 145 pcf riprap lined stormwater channels.Annual O&M costs are 3475.80/ac/yr for closed area with cap. Based on Q3 2018 Post Closure Maintenance data. LATERAL EXPANSION AREASFlexible membrane liner placed over Closure in Place area. Assume quantity needed is 10% more than Closure in Place area.Geocomposite drainage layer placed over Closure in Place area. Assume quantity needed is 10% more than Closure in Place area.not used18 inches of common soil placed over Closure in Place area (assume onsite soils available).not usedCLOSURE SYSTEM CONSTRUCTION6 inches of topsoil (obtained offsite) placed over Closure by Removal area.In areas where ash will be placed outside of the existing ash basin waste boundary, this will be considered a Lateral Expansion per the CCR regulations and will require a composite liner system.11/13/20183 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Duke Allen CCR Rule & CAMA Compliant Hybrid Costs 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD:AECOM JOB NO.:AAB & RAB Hybrid Option 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 2 DMB 10/26/18 JDM2018Not Used267Not Used26726.47216410312,170,1004,230,90014,805,95119,7833,700INSTALLED IMPOUNDMENTTASKITEM 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 CLOSURE IN PLACE / CLOSURE BY REMOVAL INTERFACE (L.F.)HYBRID OPTION 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 SheetsHybrid Option Cost Estimate for CCR Surface Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY:TOTAL IMPOUNDMENT AREA (AC)EX. AREA OF RAB LANDFILL (LIMITS OF LINER)NOTESPERIMETER OF CLOSED IN PLACE IMPOUNDMENT (L.F.)TOTAL (FINAL) ASH VOLUME TO BE CLOSED IN PLACE (CY)ENGINEERING COST (10%) LS 1 $4,090,485 $4,090,485.00TOTAL$325,718,371COST11/13/20184 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECTPLANT NAME: CLOSURE TYPE: SHEET REV. NO. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYDuke Allen CCR Rule & CAMA Compliant Hybrid Assumptions 3SUBJECTIMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.AAB & RAB Hybrid Option 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 2 DMB 10/26/18 JDM1234567891011 AECOM has assumed an over-excavation of 1 foot is necessary to achieve closure-by-removal conditions.1213141516Statements 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.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.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. Common soil for embankment and protective cover soil construction are available onsite and topsoil would come from offsiteCALCULATION SHEETPreliminary Project Costs SheetsACTIVITYHybrid Option AssumptionsThe unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience.The following key assumptions and limitations are associated with the project design, implementation and performance: KEY ASSUMPTIONSAsh to be moisture conditioned and compacted in the stack area.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.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.Interstitial water treatment was assumed to continue until construction is completed.11/13/20185 of 5Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Allen CCR Rule & CAMA Compliant Cost Summary 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:CALCULATION SHEETAAB & RABClosure by Removal Onsite 60572629ACTIVITY:CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 4 DMB 10/26/2018 JDMCost (2018 Dollars)$10,447,932$266,514,974$153,266,128$12,840,555$110,767,397$5,000,000$558,836,985Cost (2018 Dollars)$15,672,150$9,488,934$6,290,271$3,145,136$34,596,491$1,153,216.35 for 30yrs$593,433,476Engineering 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%)Closure TasksMobilization / Site Prep / DemobilizationEngineering Support (Design & CQA) ALLEN OPTION 4 -- CLOSURE BY REMOVAL ONSITEClosure & Post Closure Cost Summary CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYPreliminary Project Costs SheetsCost Summary: Closure by Removal with Onsite Landfill Cost Estimate for CCR ImpoundmentContingency (25%)Total Closure Cost of CCR Impoundment = Dewatering / Excavation / Convey MaterialStormwater Management / E&S Controls / Site RestorationOnsite Landfill Construction, Disposal and Closure11/13/20181 of 4Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Allen CCR Rule & CAMA Compliant Clean-Closure Costs 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:AAB & RAB Closure by Removal Onsite 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 4 DMB 10/26/18 JDM2018Not Used214Not Used293Not Used16,263,08325,694INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTMOBILIZATION / SITE PREP / DEMOBILIZATION1 MOBILIZATION / DEMOBILIZATION LS 1 $4,436,333 $4,436,3332 REMOVAL OF OUTLET STRUCTURES / PIPING LS 2$200,000 $400,0003 REMOVAL & FILTRATION OF FREE WATER MONTHS 54.0 $103,919 $5,611,599DEWATERING / EXCAVATION / CONVEY MATERIAL4 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 210.0 $225,832 $47,424,7205 EXCAVATE ASH FOR CLOSURE BY REMOVAL / STOCKPILE ASHCY16,263,083 $8.00 $130,104,6676EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH (DISPOSE ON-SITE)CY10,131,901 $8 $85,411,9257 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (ON-SITE)CY472,707 $8 $3,573,6628 EXCAVATE / LOAD / HAUL CCR MATERIAL (OFFSITE LF)TON0 $57 $09 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFFSITE LF)TON0 $57 $0Step 1: Start dewatering for construction time. Based on Construction Time TOTAL IMPOUNDMENT AREA (AC)Assume 1 foot of additional material to be removed over total impoundment area.CLOSURE BY REMOVAL/CONVEY MATERIAL Only include if disposing CCRS at an off-site landfill (assume density of 1.2 tons/cy).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. Step 3: Once material has decanted, CCRs must be excavated out of stockpile, loaded on trucks and hauled to onsite disposal site. Quantity takes into consideration reduction of volume due to dewatering of ash down to 30% moisture content.Only include if disposing CCRS at an off-site landfill (assume density of 1.2 tons/cy).AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)AVG. DEPTH OF FREE WATER (FT)Assume outlet structures and piping will be excavated and removed.CLOSURE BY REMOVAL W\ ONSITE LANDFILL ESTIMATED COSTSVOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF IMPOUNDMENT (L.F.)VOLUME OF ASH IN IMPOUNDMENT (CY)MOBILIZATION/SITE PREP/DEMOBILIZATIONMob/Demob & insurance: (1% of Total EPC Bid Priceincludes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup).Based on Initiation TimeCALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsClosure by Removal with Onsite Landfill Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITY11/13/20182 of 4Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Allen CCR Rule & CAMA Compliant Clean-Closure Costs 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:AAB & RAB Closure by Removal Onsite 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 4 DMB 10/26/18 JDM2018Not Used214Not Used293Not Used16,263,08325,694INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTTOTAL IMPOUNDMENT AREA (AC)AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)AVG. DEPTH OF FREE WATER (FT)CLOSURE BY REMOVAL W\ ONSITE LANDFILL ESTIMATED COSTSVOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF IMPOUNDMENT (L.F.)VOLUME OF ASH IN IMPOUNDMENT (CY)CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsClosure by Removal with Onsite Landfill Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITYONSITE LANDFILL CONSTRUCTION, DISPOSAL AND CLOSURE10 CONSTRUCT ONSITE LANDFILL AND ASSOCIATED COMPONENTSAC91 $803,245 $73,095,29511DISPOSE/SPREAD/COMPACT ASH AND CCR-IMPACTED MATERIALS FROM CLOSURE BY REMOVAL AREA IN ONSITE LANDFILL CY10,604,608 $7.56 $80,170,83312 ONSITE LANDFILL CLOSURE SYSTEMAC0$0 $0STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION10 PERMANENT RIPRAP STORMWATER CHANNELS TON 7,250 $50 $362,50011 SITE EROSION AND SEDIMENT CONTROL ACRE 214 $2,000 $428,00012 BACKFILL AND REGRADINGCY691,933 $13 $8,995,13313 TOPSOILCY172,983 $13 $2,248,78314 SEED / FERTILIZE / MULCH ACRE 214$3,767 $806,138CONTINGENCY / ENGINEERING SUPPORTCONTINGENCY (25%) LS 1 $110,767,397 $110,767,397.09ENGINEERING SUPPORT (DESIGN & CQA) LS 1 $5,000,000 $5,000,000.00POST-CLOSURE 15 GROUNDWATER MONITORING ANNUAL 30 $522,405 $15,672,15016 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $316,298 $9,488,934CONTINGENCY / ENGINEERING COSTCONTINGENCY (25%) LS 1 $6,290,271 $6,290,271.00ENGINEERING COST (10%) LS 1 $3,145,136 $3,145,135.50TOTAL$593,433,476Assume landfill designed and constructed in accordance with CAMA and CCR Rules. Cost includes landfill construction and all associated components, including: liner system, leachate management, stormwater management, access roads, closure system and all associated components,etc.Assume 10,000 lf x 10 ft widex 1 ft thick, 145 pcf riprap lined stormwater channels.Annual O&M costs are $3475/acre/yr for the total closed area with cap. Based on Q3 2018 Post Closure Maintenance data. Assume 2 feet of additional soil material (obtained onsite) graded over total Closure by Removal area. Soil obtained from the dam decommissioning can be used.Assume 6-inches of top soil needed (obtained offsite) to establish vegetative stabilization over total Closure by Removal area + 10%. Does not include topsoil for onsite landfill closure capSTORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATIONPlace, spread and compact in thin lifts dewatered ash and CCR-impacted materials excavated from Closure by Removal area into landfill.Assume total area to be restored will require site erosion and sediment control.Annual groundwater monitoring costs for each CCR impoundment after Closure by Removal assumed to be minimal.Assume total area of disturbance will be mulched, fertilized, and seeded.Included with landfill construction (Item 10)ONSITE LANDFILL CONSTRUCTION, DISPOSAL AND CLOSURECONTINGENCY / ENGINEERING COSTCONTINGENCY / ENGINEERING SUPPORTPOST-CLOSURE 11/13/20183 of 4Preliminary Based on Information Available as of 10/26/2018
PROJECTPLANT NAME: CLOSURE TYPE: SHEET REV. NO. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYAllen CCR Rule & CAMA Compliant Clean-Closure Assumptions 3SUBJECTIMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.AAB & RAB Closure by Removal Onsite 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 4 DMB 10/26/18 JDM12345678910111213The unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience.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.Interstitial 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.Free water removal and treatment was assumed to continue throughout the project initiation period.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.Groundwater monitoring costs are for a reduced groundwater network system as compared to the existing system. Groundwater monitoring costs do not include costs incurred for any additional well installation. Maintenance costs for wells are included in post-closure O&M costs.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.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. CALCULATION SHEETPreliminary Project Costs SheetsACTIVITYClosure by Removal AssumptionsThe following key assumptions and limitations are associated with the project design, implementation and performance: KEY ASSUMPTIONSEngineering 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.11/13/20184 of 4Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Allen CCR Rule & CAMA Compliant Cost Summary 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:CALCULATION SHEETAAB & RABClosure by Removal Offsite60572629ACTIVITY:CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 5 DMB 10/26/2018 JDMCost (2018 Dollars)$25,146,057$936,758,856$17,446,866$244,837,945$5,000,000$1,229,189,724Cost (2018 Dollars)$0$1,319,000$329,750$164,875$1,813,625$60,454.17 for 30yrs$1,231,003,349 CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYPreliminary Project Costs SheetsCost Summary: Closure by Removal w\ Offsite Landfill Cost Estimate for CCR ImpoundmentContingency (25%)Total Closure Cost of CCR Impoundment = Dewatering / Excavation / Convey MaterialStormwater Management / E&S Controls / Site RestorationClosure TasksMobilization / Site Prep / DemobilizationEngineering Support (Design & CQA) ALLEN OPTION 5 -- CLOSURE BY REMOVAL OFFSITEClosure & Post Closure Cost SummaryEngineering 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%)11/13/20181 of 4Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Allen CCR Rule & CAMA Compliant Clean-Closure Costs 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:AAB & RAB Closure by Removal Offsite 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 5 DMB 10/26/18 JDM2018Not Used293Not Used293Not Used16,263,08325,694INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTMOBILIZATION / SITE PREP / DEMOBILIZATION1 MOBILIZATION / DEMOBILIZATION LS 1 $9,746,057 $9,746,0572 REMOVAL OF OUTLET STRUCTURES / PIPING LS 2$200,000 $400,0003 REMOVAL & FILTRATION OF FREE WATER MONTHS 36.0 $416,667 $15,000,000DEWATERING / EXCAVATION / CONVEY MATERIAL4 REMOVAL & TREATMENT OF PORE WATER WITHIN ASH MONTHS 201.0 $225,832 $45,392,2325 EXCAVATE ASH FOR CLOSURE BY REMOVAL / STOCKPILE ASHCY16,263,083 $8.00 $130,104,6676EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH (DISPOSE ON-SITE)CY0 $8.43 $07 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (ON-SITE)CY472,707 $7.56 $3,573,6628 EXCAVATE / LOAD / HAUL CCR MATERIAL (OFFSITE LF)TON12,158,281 $57 $693,022,0239 EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFFSITE LF)TON1,134,496 $57 $64,666,272CALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsClosure by Removal w\ Offsite Landfill Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITYAssume 1 foot of additional material to be removed over total impoundment area.CLOSURE BY REMOVAL/CONVEY MATERIAL Assumed cost (tipping fee) for disposing CCRs at an Offsite Landfill (assume density of 1.2 tons/cy).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. Step 3: Once material has decanted, CCRs must be excavated out of stockpile, loaded on trucks and hauled to offsite disposal site. Quantity takes into consideration reduction of volume due to dewatering of ash down to 30% moisture content.Assumed cost (tipping fee) for disposing CCR-impacted soils at an Offsite Landfill (assume density of 1.2 tons/cy).Step 1: Start dewatering for construction time. Based on Construction Time TOTAL IMPOUNDMENT 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.CLOSURE BY REMOVAL W\ OFFSITE LANDFILL ESTIMATED COSTSVOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF IMPOUNDMENT (L.F.)VOLUME OF ASH IN IMPOUNDMENT (CY)MOBILIZATION/SITE PREP/DEMOBILIZATIONMob/Demob & insurance: (1% of Total EPC Bid Priceincludes administration (mtgs, health & safety, trailer, phone/fax/electricity, temporary facilities, utilities, roll off boxes, waste disposal, and cleanup).Based on Initiation Time11/13/20182 of 4Preliminary Based on Information Available as of 10/26/2018
PROJECT:PLANT NAME: CLOSURE TYPE: SHEET: REV. NO.:Allen CCR Rule & CAMA Compliant Clean-Closure Costs 3SUBJECT:IMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.:AAB & RAB Closure by Removal Offsite 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 5 DMB 10/26/18 JDM2018Not Used293Not Used293Not Used16,263,08325,694INSTALLED IMPOUNDMENTTASK ITEM UNIT QUANTITY UNIT COST CLOSURE COSTCALCULATION SHEETBASIS OF THE ESTIMATEYEAR COST BASISTOTAL AREA TO BE RESTORED (AC)Preliminary Project Costs SheetsClosure by Removal w\ Offsite Landfill Cost Estimate for CCR Impoundment CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYACTIVITYTOTAL IMPOUNDMENT AREA (AC)AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)AVG. DEPTH OF FREE WATER (FT)CLOSURE BY REMOVAL W\ OFFSITE LANDFILL ESTIMATED COSTSVOLUME OF FREE WATER IN IMPOUNDMENT (GAL)NOTESPERIMETER OF IMPOUNDMENT (L.F.)VOLUME OF ASH IN IMPOUNDMENT (CY)STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION10 PERMANENT RIPRAP STORMWATER CHANNELS TON 7,250 $50 $362,50011 SITE EROSION AND SEDIMENT CONTROL ACRE 293 $2,000 $586,00012 BACKFILL AND REGRADINGCY947,367 $13 $12,315,76713 TOPSOILCY236,842 $13 $3,078,94214 SEED / FERTILIZE / MULCH ACRE 293 $3,767 $1,103,658CONTINGENCY / ENGINEERING SUPPORTCONTINGENCY (25%) LS 1 $244,837,945 $244,837,945ENGINEERING SUPPORT (DESIGN & CQA) LS 1 $5,000,000 $5,000,000POST-CLOSURE 15 GROUNDWATER MONITORING ANNUAL 30 $0 $016 OPERATIONS & MAINTENANCE (O&M) ANNUAL 30 $43,950 $1,318,500CONTINGENCY / ENGINEERING COSTCONTINGENCY (25%) LS 1 $329,625 $329,625.00ENGINEERING COST (10%) LS 1 $164,813 $164,812.50TOTAL$1,231,002,661Assume total area to be restored will require site erosion and sediment control.Annual groundwater monitoring costs for each CCR impoundment after Closure by Removal assumed to be minimal.Annual O&M costs are $150/acre for the total impoundment area.Assume total area of disturbance will be mulched, fertilized, and seeded.Assume 10,000 lf x 10 ft wide x 1 ft thick, 145 pcf riprap lined stormwater channels.Assume 2 feet of additional soil material (obtained onsite) graded over total Closure by Removal area. Soil obtained from the dam decommissioning can be used.Assume 6-inches of top soil needed (obtained offsite) to establish vegetative stabilization over total Closure by Removal area.STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATIONCONTINGENCY / ENGINEERING COSTPOST-CLOSURE CONTINGENCY / ENGINEERING SUPPORT11/13/20183 of 4Preliminary Based on Information Available as of 10/26/2018
PROJECTPLANT NAME: CLOSURE TYPE: SHEET REV. NO. CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGYAllen CCR Rule & CAMA Compliant Clean-Closure Assumptions 3SUBJECTIMPOUNDMENT NAME: CLOSURE METHOD: AECOM JOB NO.AAB & RAB Closure by Removal Offsite 60572629CLOSURE OPTION: LAST UPDATED BY: DATE LAST MODIFIED: REVIEWED BY:Option 5 DMB 10/26/18 JDM12345678910111213A 25% contingency has been included for this cost estimate.Interstitial 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 offsite landfill disposal was based on a per ton basis as provided by Duke.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.CALCULATION SHEETPreliminary Project Costs SheetsACTIVITYClosure by Removal w\ Offsite Landfill AssumptionsThe following key assumptions and limitations are associated with the project design, implementation and performance: 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.KEY ASSUMPTIONSEngineering 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.Groundwater monitoring costs are for a reduced groundwater network system as compared to the existing system. Groundwater monitoring costs do not include costs incurred for any additional well installation. Maintenance costs for wells are included in post-closure O&M costs.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.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.The unit rate costs are based on data provided by Duke Energy. If no data is available, AECOM supplemented with rates from our experience.11/13/20184 of 4Preliminary Based on Information Available as of 10/26/2018

Attachment C

Site Name: Allen Steam Station1= Option‐Specific User Input1 = Calculated ValueOption12345'Not carried through for further consideration"Environmental Protection and Impacts Weight: 30%CriterionScoring SystemRequired Input Units Option 1 Option 2 Option 4 Option 5 Option 1 Option 2 Option 4 Option 5Modeled Plume Intersecting Surface Water Refer to EM Sub‐Scoring Sheet10 10 10 10 24% 7.2%Groundwater Impact Beyond the Current Compliance Boundary Refer to EM Sub‐Scoring Sheet10 10 10 10 24% 7.2%Modeled off‐site groundwater impactRefer to EM Sub‐Scoring Sheet10 10 10 10 24% 7.2%Relative rank based on visual interpretation of modeled boron plumeRefer to EM Sub‐Scoring Sheet10 5 0 0 13% 3.9%Air emissions off‐site (based on miles driven hauling CCR and CCR contaminated soil)Interpolation. Min value scores 10. Max value scores 0.Truck miles driven Miles00 0500 50 10 10 10 0 5% 1.5%Air emissions on‐site cubic yards of excavation/movementInterpolation. Min value scores 10. Max value scores 0.Volume of material excavation/movement Cu.Yds5,594,000 7,892,000 18,188,100 17,929,5005,594,000 18,188,100 10 8 0 0 5% 1.5%Avoidance of greenfield disturbanceInterpolation. Min value scores 10. Max value scores 0.Disturbed acres of greenfield Acres20 5 25 915 91 8 10 8 0 5% 1.5%3.0 2.8 2.4 2.2Cost Weight: 35%Criterion Scoring System Required Input Units Option 1 Option 2 Option 4 Option 5 Option 1 Option 2 Option 4 Option 5Closure CostClosure Cost USD$185,156,251 $280,723,031 $558,836,985 $1,229,189,724185,156,251$             1,229,189,724$          10.0 9.1 6.4 0.0 80% 28.0%Operation, Maintenance and Monitoring CostOM&M Cost USD$63,558,594 $44,995,340 $34,596,491 $1,813,6251,813,625$                 63,558,594$               0.0 3.0 4.7 10.0 20% 7.0%2.8 2.8 2.1 0.7Schedule Weight: 15%Criterion Scoring System Required Input Units Option 1 Option 2 Option 4 Option 5 Option 1 Option 2 Option 4 Option 5Initiation TimeTime to move first ashMonths30 36 54 3630 54 10 8 0 8 30% 4.5%Construction DurationEstimated durationsMonths76 88 210 20076 210 10 9 0 1 70% 10.5%1.5 1.3 0.0 0.5Closure in PlaceAsh Basin Closure ‐ Master Programmatic DocumentClosure Options Evaluation WorksheetScoring for Evaluation of Closure OptionsContribution to Total Score1. Provide continued geotechnical stability meeting appropriate safety factors under applicable loading conditionsThreshold Criteria: All closure options must comply with the following threshold criteria based on Duke Energy Guiding Principals for Ash Basin Closure2. Provide flow capacity and erosion resistance during design storm and flooding conditions3. 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)This Area Not Used For Interpretation of Environmental Modeling ResultsDuke EnergyClosure by Removal: Offsite Landfill DisposalContribution to Total ScoreValue that Scores 0DescriptionCalculated or User Selected Score Criterion WeightUser Input Value that Scores 10Calculated or User Selected Score Criterion WeightThis Area Not Used For Interpretation of Environmental Modeling ResultsCriterion WeightValue that Scores 0 Calculated or User Selected ScoreWeighted Totals (Contribution to Total Score)Contribution to Total ScoreWeighted Totals (Contribution to Total Score)Weighted Totals (Contribution to Total Score)Value that Scores 10 Value that Scores 0User InputInterpolation. Min value scores 10. Max value scores 0.Hybrid Closure Option : Footprint Reduction Within the Ash BasinAlternate Hybrid Closure Option : Additional Footprint Reduction Within the Ash BasinClosure by Removal: Onsite Landfill Within the Active Ash Basin FootprintInterpolation. Min value scores 10. Max value scores 0.User Input Value that Scores 10This Area Not Used For Interpretation of Environmental Modeling ResultsThis Area Not Used For Interpretation of Environmental Modeling Results
Site Name: Allen Steam Station1= Option‐Specific User Input1 = Calculated ValueAsh Basin Closure ‐ Master Programmatic DocumentClosure Options Evaluation WorksheetScoring for Evaluation of Closure OptionsDuke EnergyRegional Factors Weight: 15%Criterion Scoring System Required Input Units Option 1 Option 2 Option 4 Option 5 Option 1 Option 2 Option 4 Option 5Plan or potential for beneficial reuse of siteSubjective000 05% 0.8%Imported soil needsInterpolation. Min value scores 10. Max value scores 0.Soil ImportedCY215,000 194,000 246,000 237,000194000 246,000 6 10 0 2 5% 0.8%Beneficial reuse of CCRInterpolation. Max value scores 10. Zero value scores 0.Fraction UsedNone00 0 55 0 0 0 0 10 15% 2.3%Transportation impact (based on miles driven)Interpolation. Min value scores 10. Max value scores 0.Miles DrivenMiles00 0500 50 10 10 10 0 65% 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.10 7 0 25% 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.680105% 0.7%1.1 1.2 1.0 0.3Constructability Weight: 5%Criterion Scoring System Required Input Units Option 1 Option 2 Option 4 Option 5 Option 1 Option 2 Option 4 Option 5Consider stormwater management, geotechnical, and dewateringSubjective 0 to 10: 10 is the least commplicated; 0 is the most complicated50310100% 5.0%0.3 0.0 0.2 0.58.7 8.0 5.7 4.2Not Used For Subjective ScoringUser InputCalculated or User Selected ScoreContribution to Total ScoreCriterion WeightNot Used For Subjective ScoringNot Used For Subjective ScoringTotal 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 ScoreValue that Scores 10 Value that Scores 0Weighted Totals (Contribution to Total Score)
Revision JCriteria for Evaluation of Closure OptionsClosure Options Evaluation WorksheetAsh Basin Closure ‐ Master Programmatic DocumentDuke EnergyCategory CriterionGuidanceModeled Plume Intersecting Surface Water Refer to scoring system on Environmental Modeling (EM) Sub‐Scoring worksheet.Groundwater Impact Beyond the Current Compliance BoundaryRefer to scoring system on  Environmental Modeling (EM) Sub‐Scoring worksheet.Modeled off‐site groundwater impactRefer to scoring system on  Environmental Modeling (EM) Sub‐Scoring worksheet.Relative rank based on visual interpretation of modeled boron plume Refer to scoring system on  Environmental Modeling (EM) Sub‐Scoring worksheet.Air emissions off‐site Based on truck miles driven for hauling CCR and soil.Air emissions on‐site from closure implementation 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 CostOperation, Maintenance and Monitoring CostInitiation TimeConstruction DurationPlan 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 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.ConstructabilityConsider stormwater management, geotechnical, and dewatering Subjective and relative comparison to other optionsRegional FactorsFrom 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 ClosureFrom preliminary schedule for designing, permitting, bidding and constructing the option.1. Provide continued geotechnical stability under applicable loading conditions and safety factors2. Provide flow capacity and erosion resistance during design storm and flooding conditionsEnvironmental Protection and ImpactsCostSchedule3. Effectively mitigate groundwater impacts4. Comply with applicable state and federal regulations (e.g. North Carolina Coal Ash Management Act)
Environmental Groundwater Sub‐scoring WorksheetClosure Options Evaluation Duke EnergyCriteria 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 2) (Option 5)Closure In Place Hybrid Closure Option1Closure By Removal: Offsite Landfill10 10 10Criteria 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 3A) (Option 2)(Option 1) (Option 2) (Option 5)Closure In Place Hybrid Closure Option1Closure By Removal: Offsite Landfill10 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 2) (Option 5)Closure In Place Hybrid Closure Option1Closure By Removal: Offsite Landfill10 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 2) (Option 5) Closure In Place Hybrid Closure Option1Closure By Removal: Offsite Landfill10 5 0Note 2: The current compliance boundary is the compliance boundary found in the figure "Ash Basin Waste and Compliance Boundaries" provided to NCDEQ on 1/15/19Note 3: Only 3 of the 4 closure options were included in current preliminary groundwater modeling;   Option1: Closure‐in‐Place, Option 2: Hybrid Option 1, and Option 5: Closure‐by‐Removal with Offsite LandfillStation/Plant Name: Allen Steam StationEvaluation Criteria: Criteria 1 ScoreAllen Active and Retired Ash Basin Groundwater Sub‐Scoring DocumentNote 1: Based on available data at the time of scoring, the modeled plume considered boron at a concentration of 4,000 micrograms per liter (µg/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.  µg/L = parts per billion (ppb)Criteria 2 ScoreCriteria 3 ScoreCriteria 4 ScoreScored by: TH, RC, CM
Environmental Groundwater Sub‐scoring WorksheetClosure Options Evaluation Duke Energy(Option 1) (Option 2) (Option 5)Justification NotesClosure In Place Hybrid Closure Option 1Closure By Removal: Offsite Landfill10 10 10Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the closure in place scenario with natural attenuation did not show boron of 4,000 ppb or greater intercepting a surface water body based on current permit status.Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the hybrid scenario with natural attenuation did not show boron of 4,000 ppb or greater intercepting a surface water body based on current permit status.Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the excavation scenario with natural attenuation did not show boron of 4,000 ppb or greater intercepting a surface water body based on current permit status.10 10 10Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the closure in place scenario with natural attenuation did not show boron of 4,000 ppb or greater outside of the current compliance boundary.Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the hybrid scenario with natural attenuation did not show boron of 4,000 ppb or greater outside of the current compliance boundary.Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the excavation scenario with natural attenuation did not show boron of 4,000 ppb or greater outside of the current compliance boundary.10 10 10Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the closure in place scenario with natural attenuation did not show boron of 4,000 ppb or greater outside of the current Duke Energy property boundary.  Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the hybrid scenario with natural attenuation did not show boron of 4,000 ppb or greater outside of the current Duke Energy property boundary.  Based on the predictive model through the year 2300, found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report for Allen Steam Station, simulated boron concentrations for the excavation scenario with natural attenuation did not show boron of 4,000 ppb or greater outside of the current Duke Energy property boundary.  10 5 0Based on a review of boron concentrations found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report, Option 1 Closure In Place scenario is  marginally better than both Option 2 Hybrid Closure and Option 5  Closure by Removal. The Option 1 Closure In Place modeled time to reach 2L at the compliance boundaries and modeled time that boron greater than 2L continues beneath Lake Wylie is less/shorter than respective times modeled with the other two options.Based on a review of boron concentrations found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report, Option 2 Hybrid Closure scenario is  marginally worse than Option 1 Closure In Place and marginally better than Option 5  Closure by Removal. The Option 2 Hybrid Closure modeled time to reach 2L at the compliance boundaries and modeled time that boron greater than 2L continues beneath LakeWylie is between those respective times modeled with the other two options.Based on a review of boron concentrations found in the November 2018 Preliminary Groundwater Flow and Transport Modeling Report, Option 5 Closure By Removal scenario is  marginally worse than both Option 1 Closure In Place and Option 2  Hybrid Closure. The Option 5 Closure In Place modeled time to reach 2L at the compliance boundaries and modeled time that boron greater than 2L continues beneath Lake Wylie is more/longer than respective times modeled with the other two options.3. Only 3 of the 4 closure options were included in current preliminary groundwater modeling;   Option1: Closure‐in‐Place, Option 2: Hybrid Option 1, and Option 5: Closure‐by‐Removal with Offsite Landfill.Allen Active and Retired Ash Basin Groundwater Sub‐Scoring Document JustificationNotes:1. Based on available data at the time of scoring, the modeled plume considered boron at a concentration of 4,000 micrograms per liter (µg/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.  µg/L = parts per billion (ppb)2. The current compliance boundary is the compliance boundary found in the figure "Ash Basin Waste and Compliance Boundaries" provided to NCDEQ on 1/15/18.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