Mayo_ClosureOptionsAnalysis_20181114

Mayo Plant Ash Basin Closure Options Analysis
Summary Report
This summary report (Report) presents the Closure Options evaluation for the ash basin located at Duke
Energy Progress Mayo Station, located at 10660 Boston Road, near Roxboro, Person 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
Mayo that is protective of the environment, safely closes the Ash Basin, minimizes the other associated
risks, and was the least cost to customers. A permit -level design was developed for that option in 2016.
The company then paused that work, pending determination that the site would meet the requirements
for a low -risk impoundment classification pursuant to N.C. Coal Ash Management Act (CAMA), as
amended by House Bill 630. Duke Energy has completed those requirements at the Mayo site for a low -
risk classification. Stormwater management (downstream impacts) was identified as a concern for the
closure -in -place option in the 2016 analysis. In 2018, the grading plan for the Closure -in -Place option
has been revised to direct the majority of stormwater runoff towards Mayo Reservoir rather than down
Crutchfield Branch.
SITE BACKGROUND
Duke Energy's Mayo Station is a single -unit, 727-megawatt coal-fired plant located near Roxboro, N.C,
less than one-half mile south of the North Carolina -Virginia line. It began commercial operation in 1983,
and the station is currently in active operation. Mayo operates one impoundment for storing wet -
sluiced ash, which is referred to as the Active Ash Basin (Ash Basin). Historically, both bottom ash and fly
ash have been sluiced to the Ash Basin, but in 2013/2014 Mayo converted to dry ash handling systems.
Bottom ash and fly ash have been disposed of in the on -site lined landfill starting in 2014.
Summary— Page 1

The station has two related facilities considered and regulated as dams by the North Carolina
Department of Environmental Quality (DEQ): a single ash basin (NCDENR ID=PERSO-035), and two dams
associated with the FGD Pond (NCDENR ID=PERSO-036, NCDENR ID=PERSO-037) which are shown in the
figure below.
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Figure 1. Ash Basin
CLOSURE OPTIONS
For the Mayo Station, under the direction of Duke Energy, AECOM developed the following conceptual
closure options that remain under evaluation:
• Option 1: Hybrid Closure
• Option 2: Closure -In -Place
• Option 3: Closure -By -Removal (Existing On -Site Landfill)
Option 1 consists of excavating ash materials from the proposed Closure -by -Removal Areas depicted on
Figures A1A and A1B and the subsequent placement of these ash materials within the proposed
consolidated Hybrid Ash Closure Area. The Hybrid Ash Closure Area reduces the Ash Basin footprint, but
due to site geometry, also incorporates a lateral lined expansion into a small greenfield area outside the
Summary— Page 2

current basin boundary. Following these excavation and placement activities, the Hybrid Ash Closure
Area will be capped with an infiltration barrier/cover system meeting the requirements of the Federal
Coal Combustion Residuals (CCR) Rule and CAMA (Figure A4). The Ash Basin dam will be breached as a
final step in this option to enable release of stormwater.
Option 2 consists of leaving the ash material within the Ash Basin, graded to facilitate stormwater
drainage which will be capped with an infiltration barrier/cover system meeting the requirements of the
Federal CCR Rule and CAMA as shown on Figures A2A, A2B, and A4. The Ash Basin dam will remain in
place and stormwater is routed through a modification of the current discharge channel to Mayo Lake.
Option 3 consists of excavating all ash materials from the Ash Basin, and placing these ash materials in a
new, lined phase which would be permitted and constructed within the existing landfill Site Suitable
area as depicted in Figure A3. This 30-acre phase would be constructed with a base liner system and an
infiltration barrier/cover system meeting the requirements of the Federal CCR Rule and CAMA (Figure
A4). The Ash Basin dam will be breached as a final step in this option to enable release of stormwater.
Options earlier evaluated but not carried forward included Option 3B (closure -by -removal with existing
and new on -site landfill) and Option 4 (closure -by -removal with off -site landfill) which were removed
from consideration from the Options Analysis for reasons of availability of on -site landfill space and
excessive schedule/cost.
Tables 1, 2, and 3 of this report present a tabulated summary of each evaluated closure option,
estimated quantities of ash and soil materials associated with each closure option, and a more detailed
overview of each closure option presented.
Attachment A of this report includes figures depicting conceptual -level plan drawings and cross
sections/details for each closure option.
The figures included in Attachment A are as follows:
• Figure A1A — Option 1 Hybrid Closure Plan View
• Figure A1B — Option 1 Hybrid Closure Profile and Section Views
• Figure A2A—Option 2 Closure -In -Place Plan View
• Figure A2B — Option 2 Closure -In -Place Profile and Section Views
• Figure A3 — Option 3 Closure -By -Removal to Existing On -Site Landfill Plan View
• Figure A4 — Cover and Liner System 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 each of the
various site locations. This scoring evaluation tool can be found in Attachment C and considers the
following primary criteria:
Summary— Page 3

• Environmental Protection and Impacts
• Cost
• Schedule
• Regional Factors
• Constructability
Rough Order of Magnitude Costs
A rough order of magnitude (ROM) Class 5 cost estimate was prepared for each of the closure options,
based on information and quantities developed during the conceptual design activities. The estimated
costs include construction, permitting, engineering design, post -construction O&M, and groundwater
monitoring. A tabulated summary of the preliminary closure cost estimates is provided below:
Current Estimates (October 2018)
Option
Closure Option
Estimated
Estimated O&M
Construction Cost
Cost (30 Years)
1
Hybrid Closure
$109,290,046
$32,093,144
2
Closure -In -Place
$74,626,681
$40,408,995
3
Closure -By -Removal
$199,751,368
$24,637,553
(Existing On -Site Landfill)
Option 2: Closure -In -Place has the lowest estimated construction cost which is primarily due to the
substantial reduction in material excavation and associated dewatering activities. Detailed tabulated
ROM cost estimates are included in Attachment B.
Schedule
Within the scoring evaluation, estimates of the length of time required to initiate closure activities and
the anticipated construction duration are provided for each option.
Option 1 is estimated to take 96 months or 8 years. Option 2 is estimated to take 66 months or 5.5
years. Option 3 is estimated to take 120 months, or 10 years.
A major driver in the estimated construction durations is the assumed material excavation/ movement
rate of 1,000,000 cubic yards/year; therefore, the Closure -By -Removal option has longer construction
duration, due to the requirement to move all ash materials, compared to the Hybrid and Closure -In -
Place options where material movement quantities are less. Another driver is the assumed capping rate
of 50 acres/year for completing the closure system for the Hybrid and Closure -In -Place options.
Summary— Page 4

Options 1 and 2 are the only options that could be completed by the CAMA deadline of 2029, assuming
work could begin in 2020.
Evaluation Criteria
This Options Analysis was developed as a decision -making tool to assist in selection of closure options
when multiple methods are allowed under applicable regulations. The intent was to develop a decision
framework that used weighted scorings to balance environmental factors, cost, and the safety of
workers and the public. The Options Analysis incorporates Duke Energy's obligation as a regulated utility
to ensure that its closure decisions are protective of the environment and communities, while also being
prudent from a cost-effectiveness perspective.
The analysis considered multiple aspects in each criterion, including surface water impacts, groundwater
impacts, air emissions, greenfield disturbance, construction duration, imported soil needs,
transportation and noise impacts, stormwater management, long-term maintenance needs and post -
closure monitoring.
These elements were combined to provide a weighted sum for each criterion using the following
weights: environmental considerations (30%); cost (35%); schedule (15%); regional/ community factors
(15%) and constructability (5%.). Duke Energy placed primary emphasis on environmental factors and
cost, which were approximately equal in weight. 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, rates each option on a scale of 0 (least favorable) to 10
(most favorable) for each of the specified criteria. The scores for each option are then summed based
on specified criterion weighting, resulting in an overall weighted score for each option. The results of
the scoring evaluation for the Mayo closure options are summarized below:
Summary— Page 5

Scoring Summary (October 2018)
Criterion
Option
1
2
3
Environmental Protection and Impacts
2.75
2.44
2.55
Cost
2.39
2.80
0.70
Schedule
0.74
1.50
0.00
Regional Factors
1.16
1.12
0.14
Constructability
0.15
0.40
0.30
Total Score
7.18
8.26
3.69
DISCUSSION
The Options Analysis finds relatively similar rankings for environmental considerations, such as impacts
to groundwater, surface water, and avoidance of greenfield disturbance. The analysis incorporates the
latest groundwater modeling at Mayo that demonstrates groundwater near the basin responds similarly
for several decades in all closure options evaluated. The most effective step the company can take to
improve groundwater is to safely decant the free water from the ash basin, which will occur in any
closure approach.
In terms of duration of work and closure time, the Closure -In -Place option (#2) and Hybrid option (#1)
scenarios would be expected to be completed in 5.5 years and 8 years, respectively and could be
completed by the CAMA deadline of 2029, while the Closure -By -Removal option (#3) is expected to take
10 years. The excavation scenario (#3) would extend beyond the current CAMA deadline of 2029.
However, it remains in our options analysis despite this for full transparency of the alternatives.
Other aspects the company considered are regional impacts to the surrounding community related to
traffic and noise generated by each of the options. Traffic to and from the site will occur through the
duration for each option noted above. That will include workers, trucks for deliveries or movement of
soil, topsoil, stone, and geosynthetics. For the Closure -In -Place option (#2) and Hybrid option (#1) traffic
will be mingled with typical traffic on the main roads leading to Mayo Station and Boston Road in
particular. Closure -By -Removal option (#3) requires a significant number of truck crossings per work day
of Boston Road over the approximate 10-year excavation period to access the 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. At the Mayo site, the on -site landfill is located
across a public highway, which would present a degree of safety risk and road congestion issues in
excavation scenarios.
Summary— Page 6

The Closure -By -Removal option is at least double the estimated cost of the Closure -In -Place option and
causes other unnecessary community impacts with little compelling environmental benefit. While long-
term modeling indicates a quicker reduction in the boron plume within the immediate vicinity of the
basin footprint for the Closure -By -Removal scenario, compared to the Closure -in -Place scenario, the
modeled concentrations at downstream points are nearly identical for all the closure options at each
evaluated point in time. Moreover, the quicker reduction is partially offset by the fact that the modeled
improvement is delayed in the Closure -By -Removal scenario, compared to the Closure -in -Place scenario,
due to the extended construction time. In any event, the minor change in modeled plume size, within
the immediate vicinity of the basin footprint, is not enough to justify the cost of the Closure -by -Removal
scenario - particularly when the impact and improvement do not materially affect neighbors or other
potential receptors.
The Hybrid Closure option ranks most closely with Closure -In -Place but does not appear to produce
environmental benefits commensurate with the added cost and closure time. It also brings potential
construction difficulties with development of the closure area stability slope or wall.
CONCLUSION
Based on the concept designs for the selected closure options and evaluation of the criteria established
(environmental protection/impacts, cost, schedule, regional factors and constructability), Closure -In -
Place option (#2) or the Hybrid option (#1) were identified as the preferred options that best balance
the various considerations associated with basin closure.
Attachments:
A —Closure Options Figures
B — Closure Options Cost Estimates
C — Closure Options Scoring Matrix and Groundwater Sub -Scoring Worksheet
Summary— Page 7

Table 1 — Closure Options Summary
Ash Basin Closure Options Evaluation
Mayo Station
Duke Energy
Description
• Install stormwater controls
• Install free water decanting and water treatment system
• Decant free water
• Perform interstitial dewatering of ash material as needed to
provide stable working surfaces
• Install deep soil mixing method wall and/or stabilized soil wedge
• Excavate ash, and place excavated ash material within the Hybrid
ash closure area
• Remove one foot of residual soil in the ash excavation areas
• Install new liner system over about 4.5 acres of natural ridge that
would need to be incorporated as a lateral expansion in order to
facilitate a more consolidated cover geometry.
• Install closure cover system
• Removal of dam
• Groundwater corrective action and long-term monitoring pursuant
to CAMA/CCR
• Install stormwater controls
• Install free water decanting and water treatment system
• Decant free water
• Perform interstitial dewatering of ash material as needed to
provide stable working surfaces
• Regrade ash basin waste boundary and construct closure cover
• Balance of cover material required from off -site borrow source
with greenfield disturbance area of 30 acres.
• Minimal dam material removed and restore disturbed areas.
• Groundwater corrective action and long-term monitoring pursuant
to CAMA/CCR
• Install stormwater controls
• Install free water decanting and water treatment system
• Decant free water
• Perform interstitial dewatering of ash material as needed to
provide stable working surfaces
• Excavate the ash and one foot of residual soil from the basin,
place all 5.73 million CY in the existing landfill with new cell areas
(greenfield disturbance) of 30 acres, within permitted boundary.
• Remove dam, regrade closure -by -removal area, and restore
disturbed areas.
• Groundwater corrective action and long-term monitoring pursuant
to CAMA/CCR

Existing Ash
Ash Basin —Ash
1-Foot Over -Excavation (Entire
Footprint, including upstream dam
face)
Existing Ash Total
Free Water Volume
Option 1 (Hybrid)
Hybrid Closure Area (Ash to Remain in
Place)
Closure -by -Removal (Includes 1-ft
Over -Excavation)
Liner System over Lateral Expansion
Areas
Option 2 (Closure -In -Place)
Closure -In -Place
Relocation of Ash
Option 3 (Closure -by -Removal -
Existing On -Site Landfill)
Closure -by -Removal (Includes 1-ft
Over -Excavation)
Existing Soil
Dam Soil Volume (total)
Dam Soil Volume (partial removal for
Option 2)
Near -Site Soil Borrow Area Needed
(Option 2 only)

Item
Table 2 — Quantity Summary
Ash Basin Closure Options Evaluation
Mayo Station
Duke Energy
Tons Volume (CY)
318,000 265,000
112,800 93,500
430,800 358,500
542,400 452,000
542,400 452,000
271,000
226,000
57,600
48,000
115,200
96,000
444,000
370,000
Area (Ac)
82
58
140
140
30
30

Table 3 - Option 1 Overview: Hybrid Closure Option
Ash Basin Closure Options Evaluation
Mayo Plant
Duke Energy
Description
1. Install stormwater controls
2. Install free water decanting and water treatment system
3. Decant free water
4. Perform interstitial dewatering of ash material as needed to provide
stable working surfaces
5. Install deep mixing method wall and/or stabilized soil wedge as needed
6. Excavate ash, and place excavated ash material within the Hybrid ash
closure area
7. Install new liner system over lateral expansion areas = 4.5 acres. The
4.5 acres of natural ridge would need to be incorporated as a lateral
expansion in order to facilitate consolidated mound geometry.
8. Install closure cap system
9. Removal of dam
10. Groundwater corrective action and long-term monitoring pursuant to
CAMA/CCR
1. Install stormwater run-on controls to divert stormwater from the ash
basin where possible.
2. Design and install temporary water treatment system to manage
decanting, interstitial dewatering, and (contact) stormwater.
3. Decanting & treatment of free water.
4. Construct the deep mixing method (DMM) wall and/or stabilized soil
wedge to stabilize the cut -slope at the close -in -place / closure -by -
removal interface; Approximately 1,500 LF long.
5. Removal & treatment of interstitial pore water in ash material as needed
to provide stable working surfaces during construction within the
closure -in -place and closure -by -removal areas.
6. Permit and construct new liner system over the lateral expansion areas;
approximately 4.5 acres. The 4.5 acres of natural ridge would need to
be incorporated as a lateral expansion in order to facilitate consolidated
mound geometry.
7. Excavate an estimated 1,980,000 tons (1,650,000 CY) of ash material
from within the closure -by -removal area, and place the excavated ash
material within the Hybrid ash closure area.
8. Excavate an estimated 93,500 CY of residual soil material (1 foot below
ash) from the closure -by -removal area (including the upstream dam
face), and place the excavated material within the Hybrid ash closure
area (Total excavation = 1,743,500 CY).
9. Remove dam down to natural grade; approximately 800,000 CY of
clean fill material generated.
10. Leave in place an estimated 4,620,000 tons (3,850,000 CY) of ash
material beneath the consolidated hybrid "mound" and within the ash

Subject
Table 3 - Option 1 Overview: Hybrid Closure Option
Ash Basin Closure Options Evaluation
Mayo Plant
Duke Energy
Description
basin "fingers," and install closure cap system (approximately 82 acres)
utilizing material generated by removal of the existing dam
(approximately 265,000 CY needed).
11. Regrade the closure -by -removal area to direct stormwater to new
permitted outfall, utilizing an estimated 93,500 CY of soils generated by
removal of the existing dam. Total clean fill volume required = 358,500
CY. (The remaining dam material will be utilized to reclaim the ash
basin footprint, as reflected in the cost spreadsheet.)
12. Restore areas disturbed during closure; approximately 145 acres
(disturbed area).
13. Decommission temporary water treatment facility.
14. Groundwater corrective action and long-term monitoring pursuant to
CAMA/CCR
1. Air emissions off -site (based on miles driven) = N/A (not driving off -
site).
2. Air emissions on -site (based on gallons of fuel consumed) from closure
implementation = Assumed that the highest volume of material (ash /
residual soil / clean fill) excavation/movement will result in the highest
fuel consumption. Material excavation/movement = 2,543,500 CY.
3. Greenfield disturbance = Approximately 4.5 acres
1. Capital costs = $109,290,046.
2. Long-term O&M and monitoring = $1,069,771 annual.
3. Avoided costs = Off -site ash hauling and costs managed through
minimizing material handling.
1. Initiation time (to begin ash removal) = 36 months (includes dewatering
and design/permitting and is a function of the stabilization construction).
2. Design and permitting = 12 months.
3. Construction = 60 months
4. Post -closure = 30 years.
1. Plan or potential for beneficial reuse of site = None.
2. Imported soil needs = None (everything is available from removal of
existing dam).
3. Transportation impact (based on miles driven) = N/A (not driving off -
site).
4. Noise impact due to on -site activity (based on proximity of neighbors) _
Slight impact during construction, but no change post construction
(construction noise level approximately equivalent for each option,
therefore scoring is based on construction duration).
5. Visual impact (based on final height of storage facility, land uses within
the viewshed) = Peak of hybrid mound anticipated at 554 feet,
compared to current dam crest at 488 feet.
2

Table 3 - Option 1 Overview: Hybrid Closure Option
Ash Basin Closure Options Evaluation
Mayo Plant
Duke Energy
Description
1. High internal slopes within the basin will require stabilization.
2. 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. Construction of the lateral expansion liner system and its leachate
collection system will be a challenge.
3

Subject
Table 3 - Option 2 Overview: Closure -in -Place
Ash Basin Closure Options Evaluation
Mayo Plant
Duke Energy
Description
1. Install stormwater controls
2. Install free water decanting and water treatment system
3. Decant free water
4. Perform interstitial dewatering of ash material as needed to provide
stable working surfaces
5. Regrade ash basin waste boundary and construct closure cap.
6. Partial dam material removed and restore disturbed areas.
7. Groundwater corrective action and long-term monitoring pursuant to
CAMA/CCR
1. Install stormwater run-on controls to divert stormwater from the ash
basin where possible.
2. Design and install temporary water treatment system to manage
decanting, interstitial dewatering, and (contact) stormwater.
3. Decanting & treatment of free water.
4. Removal & treatment of interstitial pore water in ash material as needed
to provide stable working surfaces during construction within the
closure -in -place area.
5. Regrade the close -in -place area to direct stormwater to the existing
permitted outfall.
6. Remove Dam down to elevation 474 feet approximately 50,000 CY of
clean fill material generated.
7. Install closure cap system over the close -in -place area, utilizing an
estimated 452,000 CY of soils from borrow source (50,000 CY comes
from dam, preferably remaining 402,000 CY comes from near -site
borrow source).
8. Relocate an estimated 1,200,000 tons (1,000,000 CY) of ash material
from within the closure -in -place area to achieve proposed grades.
9. Restore areas disturbed during closure; approximately 140 acres
(disturbed area).
10. Decommission temporary water treatment facility.
11. Groundwater corrective action and long term monitoring pursuant to
CAMA/CCR.
1. Air emissions off -site (based on miles driven) = N/A (not driving off -
site).
2. Air emissions on -site (based on gallons of fuel consumed) from closure
implementation = Assumed that the highest volume of material (ash /
residual soil / clean fill) excavation/movement will result in the highest
gallons of fuel consumed. Material excavation/movement = 1,050,000
CY.
3. Greenfield disturbance = Approximately 30 acres for borrow.

Subject
Table 3 - Option 2 Overview: Closure -in -Place
Ash Basin Closure Options Evaluation
Mayo Plant
Duke Energy
Description
1. Capital costs = $74,626,681.
2. Long-term O&M and monitoring = $1,346,967 annual.
3. Avoided costs = Off -site ash hauling, costs managed through
minimizing material handling.
1. Initiation time (to begin ash removal) = 18 months (includes
design/permitting and dewatering.
2. Design and permitting = 12 months.
3. Construction = 48 months
4. Post -closure = 30 years.
1. Plan or potential for beneficial reuse of site = none.
2. Imported soil needs = 402,000 CY (from unidentified borrow source,
preferably near -site).
3. Transportation impact (based on miles driven) = N/A (not driving off -
site).
4. Noise impact due to on -site activity (based on proximity of neighbors) _
Slight impact during construction, but no change post construction
(construction noise level approximately equivalent for each option,
therefore scoring is based on construction duration).
5. Visual impact (based on final height of storage facility, land uses within
the viewshed) = equivalent to current conditions.
1. 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.
2. No internal ash slopes to stabilize
2

Subject
Table 3 - Option 3 Overview:
Closure -by -Removal / Existing On -Site Landfill
Ash Basin Closure Options Evaluation
Mayo Plant
Duke Energy
Description
1. Install stormwater controls
2. Install free water decanting and water treatment system
3. Decant free water
4. Perform interstitial dewatering of ash material as needed to provide
stable working surfaces
5. Construct 30-acre phase of existing landfill.
6. Excavate the ash from the basin, place in the existing landfill. Trucks
would cross Boston Road/Highway 501 to the existing landfill location
numerous times per day on average for nearly 7 years.
7. Remove dam, regrade closure -by -removal area, and restore disturbed
areas.
8. Groundwater corrective action and long-term monitoring pursuant to
CAMA/CCR.
1. Install stormwater run-on controls to divert stormwater from the ash
basin and industrial landfill areas where possible.
2. Design and install temporary water treatment system to manage
decanting, interstitial dewatering, and (contact) stormwater.
3. Decanting & treatment of free water.
4. Removal & treatment of interstitial pore water in ash material as needed
to provide stable working surfaces during construction within the
closure -by -removal area.
5. Permit and construct a new landfill and a new 30-acre phase of liner for
the industrial landfill utilizing an estimated 48,000 CY of soils from the
removal of the existing dam.
6. Excavate the ash material from within the closure -by -removal area (ash
basin waste boundary area), an estimated 6,600,000 tons (5,500,000
CY), and place in the existing Landfill.
7. Excavate an estimated 225,900 CY of residual soil material (1 foot
below ash) from the ash basin, and place in the existing Landfill. (Total
excavation = 5,725,900 CY).
8. Install landfill cap system over new phase of existing industrial landfill
utilizing an estimated 96,000 CY of soil by removal of the dam.
9. Remove dam down to elevation 380 feet; approximately 800,000 CY of
clean fill material generated for use in cap and reclamation.
10. Regrade the closure -by -removal area to direct stormwater to the new
permitted outfall utilizing an estimated 226,000 CY of soils generated
by removal of the existing dam. The remaining dam material
(approximately 430,000 CY) will be left in place or utilized to reclaim the
ash basin footprint and the pond area will be graded to drain.

Table 3 - Option 3 Overview:
Closure -by -Removal / Existing On -Site Landfill
Ash Basin Closure Options Evaluation
Mayo Plant
Duke Energy
Description
11. Restore areas disturbed during closure; approximately 140 acres
(disturbed area).
12. Decommission temporary water treatment facility.
13. Groundwater corrective action and long-term monitoring pursuant to
CAMA/CCR
1. Air emissions off -site (based on miles driven) = 2 miles (round trip).
2. Air emissions on -site (based on gallons of fuel consumed) from closure
implementation = Assume the highest volume of material (ash / residual
soil / clean fill) excavation/movement will result in the highest gallons of
fuel consumed. Material excavation/movement = 6,526,000 CY
3. Greenfield disturbance = Approximately 30 acres for additional phase
within permitted landfill.
1. Capital costs = $199,751,368.
2. Long-term O&M and monitoring = $821,252 annual.
1. Initiation time (to begin ash removal) = 36 months (includes dewatering
and design and permitting)
2. Design and permitting = 12 months.
3. Construction = 84 months
4. Post -closure = 30 years.
1. Plan or potential for beneficial reuse of site = None.
2. Imported soil needs = None (everything is available from removal of
existing dam).
3. CCR beneficial reuse = None.
4. Transportation impact (based on miles driven) = 2 mile (round trip
crossing highway).
5. Noise impact due to on -site activity (based on proximity of neighbors) _
Slight impact during construction, but no change post construction
(construction noise level approximately equivalent for each option,
therefore scoring is based on construction duration).
6. Visual impact (based on final height of storage facility, land uses within
the viewshed) = 672 feet (Final height of the existing landfill).
1. Relatively manageable construction option.
2. 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.
2

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G S T L
x r
FLUSH
x`�
/ OQ x C�' POND
x -
/ = x
-
_
� ppx�ti
1'
41
pax
'a j � m- I
_ 1 W • r
td
k r-lie
left VA;p
I - ;
r._ - __ • • - - - -
�1 4p
y� 1.
T �r J
L''
"L - ' �
r-'{
TITLE
IL
p� FOR
t ..
LEGEND
CCR UNIT BOUNDARY
CLOSURE BY REMOVAL AND CLOSURE IN PLACE
AREA BOUNDARY
DMM WALL LOCATION (APPROX)
LATERAL EXPANSION AREA (APPROX. 4.5 AC)
FGD SETTLING AND FLUSH POND TO BE
DECOMMISSIONED AND CAPPED AS REQUIRED.
HYBRID CLOSURE
PLAN VIEW
MAYO STEAM ELECTRIC PLANT
ASH BASIN CLOSURE OPTIONS EVALUATION
PERSON COUNTY, NORTH CAROLINA
MAYO PLANT
SCALE : -1 = 300' DES : CLD
w DUKE DWG TYPE: 09 DWG TYPE DFTR: CLD
' JOB NO: 60432013 CHKD' DS
FILENAME:
- - DWG SIZE
.
31
ANSI D
22.0"x 34.0"
E N E RG DATE : 10/18/2018 ENGR :
HYBRID REDESIGN16.6 PERCENT APPD:
DRAWING NO. REVISION
FIGURE A1A 1
m
I I I I I I I I I I I I I I I I I I I I I I I I I I I
TENTHS 10 20 30

REV. 1
575
575
CCR UNIT BOUNDARY
550
550
�//o
PROPOSED
FINAL
COVER GRADE
525
525
500
EXSTING
GRADE
500
T
+
475
475
DEEP
MIXING
METH
D WALL
+ +
+++
+ + +
++
450
450
+ +
+++
+M+RtM
+++
V/#L+++
+++
+++
++
425
_
425
HIS
ORICAL
RADE
400
400
375
375
350
350
0+00
5+00 10+00
15+00 20+00 25+00 30+00
35+00
40+00 44+50
LEGEND
SECTION A -A
-
EXISTING GROUND
HISTORICAL GROUND
PROPOSED FINAL COVER GRADE
+
+ + + DAM REMOVAL
CCR EXCAVATION (CLOSURE BY REMOVAL)
CCR PLACEMENT (CLOSURE IN PLACE)
575
575
C R UNIT BOUNDARY -LATERAL EXPANSION AREA
550
ROPOSE FINAL C VER GR DE
550
525
E STING GFrDE
525
500
500
475
475
450
450
425
`7
425
400
400
0+00
5+00 10+00 15+00 20+00 25+0Q5+50
SECTION B-B
TITLE
HYBRID CLOSURE PROFILE AND
SECTION VIEW
MAYO STEAM ELECTRIC PLANT
ASH BASIN CLOSURE OPTIONS EVALUATION
PERSON COUNTY, NORTH CAROLINA
FOR
MAYO PLANT
SCALE: DES: CLD
DUKEDWG TYPE: 09 DWG TYPE DFTR: CLD
ARS
ENERGY®
DATE: 10 18/2018 ENGR :
FILENAME:
HYBRID REDESIGN16.6 PERCENT APPD:
DWG SIZE
DRAWING NO. REVISION
ANSI D
22.0"x 34.0"
FIGURE Al B 1
x
m
1 1 1 1 1 1 1 1 1 1 1 1 I I
0 1 2 3 2 TENTHS 10 20 30

3 3 4 5 6 7 8 REV. 0
"475•�'�/' —� I /I j I �` /� \ \ ; \\ \\ \ISO
\ \
I500
475
475
ik
LAKE �O p \ \ / CRUTCHFIELD BRANCH
\\Z7
oftb 00
%44
�'N \ v v "A
o
425-
/ \ \ \ � � 6 •�:��\ ` / I —^J /•450--__r--450--
I474
400',� r, LEGEND
472
470 CCR UNIT BOUNDARY
CD 45� DUKE ENERGY PROPERTY BOUNDARY
00 468 CCR UNIT
� \ �4 BOUNDARY(APPROXIMATE) 7 ' // -----' , EXISTING MINOR CONTOURS (5 FT)
70° / 466 / ' t \11 15 EXISTING MAJOR CONTOURS 25 FT
Ox00 0 464 / / t\ \� t I I \I I i / / // / FINAL COVER MINOR CONTOURS (2 FT)
/ FINAL COVER MAJOR CONTOURS 10 FT
\ —
21 /
0`S"00 / / ;,l' �\ \� /�',' I i / / �'o /' DITCH CENTERLINE AND FLOW DIRECTION
FINAL COVER SLOPE
I — 0 1 +{�F / r O� v / '' • / /
—500 — — / ` 1 \ oo ` IN FIELD CCR LIMITS VERIFICATION AREA (SEE
/ ,��\\\\\\� 'Ox 00 ) ,� NOTE 1)
00 � 40
7'
475 — _� \ \ — r SS00cv-Oo
o \ 3 >
-- ---- - -- - - -
`
g 500 I r 1 I Q\° 4�� 2� o �N� ° 1 / / ������. }/ -1 I REFERENCE
_ ,�• � 1 ` 1. TOPOGRAPHIC DATA PRESENTED IN THIS DRAWING IS TAKEN
`O V / / / / � � � FROM "AERIAL TOPOGRAPHIC SURVEY - MAYO PLANT" DATED
\'500 ` � °° � N � /--f \ //
/ OCTOBER 31, 2015 PREPARED BY WSP FOR DUKE ENERGY.
3. ASH BASIN WASTE BOUNDARY PRESENTED IN THIS DRAWING IS
PROP. DISCHARGE CHANNEL `� \ -.— \ PREPARED BY SYNTERRA FOR DUKE ENERGY. UPDATED
525 5o _ \ \ SEPTEMBER 2018
l I 4. NO UNDERGROUND UTILITIES HAVE BEEN LOCATED OR MAPPED
o xo`L\ `\ / / '�� \ / FOR THIS PROJECT. THE LOCATION OF ANY AND ALL UTILITIES
1 Soo `'oo / / \ / / \ \ = SHOWN HEREON WHETHER PUBLIC/PRIVATE ARE BASED ON
2 1 PHOTOGRAMMATIC MAPPING AND ARE APPROXIMATE ONLY.
00
.00 ` 7"� \ I 11 \ \ 5. BASIS OF BEARINGS: NC GRID NAD83/2011,ELEVATIONS ARE
J I \ / \ BASED ON NAVD88.
6. SEEP LOCATIONS DEPICTED ARE APPROXIMATE AND BASED ON
` l / Soo / o\ /~ I / ��o ( I I \ — \ / / \ / / "COMPREHENSIVE SITE ASSESSMENT REPORT - MAYO STEAM
ELECTRIC PLANT " PREPARED BY SYNTERRA FOR DUKE ENERGY
/ - �► 1 / o '�'& AND SUBMITTED TO NCDEQ (NPDES PERMIT NO. NC0038377) ON
— 525
-�.^ SEPTEMBER 2, 2015.
\ \ 1 / / — / s \ \ \ /.
7. DEPICTED WETLANDS AND PROPERTY BOUNDARY ARE BASED ON
\ /�;' �5°° / JURISDICTIONAL WATERS FIGURES PREPARED FOR DUKE
oa' •- r-� Ci/ ��\��\ ENERGY BY WOOD PLC, JULY 18,2018.
MAYO LAKE
EXISTING RAIL LINE
NOTE
\ 1. FINAL COVER CAP SYSTEM IS ONLY REQUIRED WITHIN THE ASH
\ i r\ BASIN BOUNDARY. LIMITS OF ASH BASIN BOUNDARY WILL NEED
�soo ` TO BE REFINED THROUGH GEOTECHNICAL INVESTIGATION TO BE
PERFORMED AT LATER DATE.
1 .61 0
0 300 600 900
/ T \ / � . \ ` r cam_, / r / ._` �l � ✓r �` � 0 \ `
< -
5 GRAPHIC SCALE (IN FEET)
Q �
TITLE
MAYO PLANTSTEAM ELECTRIC CLOSURE IN PLACE GRADING PLAN
CIO
1 f ! / /I / / 1� COAL PILE / .. ,
MAYO STEAM ELECTRIC PLANT
I / /�-- / ASH BASIN CLOSURE OPTIONS EVALUATION
\ / / PERSON COUNTY, NORTH CAROLINA
FOR
MAYO PLANT
1 / ////, // ` // i ( `�'•"/ �� ,: �. {_ ,�+�' SCALE: 1=300' DES: RD
' DUKE
DWG
NO: 605D76646 CHKD: CP
I d — ENERGY®
DATE: 11-20-18 ENGR : CP
FILENAME: CIP_GRADING_PLAN.DWG
APPD: DC
DWG SIZE DRAWING NO. REVISION
1 / //� /�\ \ \\ // O 1 • • • •• • O 1 • ANSI D
FIGURE A2A 0
0 1 2 3 2 TENTHS 10 20 30 3 4 5 6 7 8
1 1 1 1 1 1 1
m
0

2 3 4 5 6 7 8 FIGURE A213
REV. O
q
550
525
500
475
450
425
400
375
0+00
CCR UNIT
BOUNDARY
550
525
500
475
450
425
LEGEND
400 EXISTING GROUND
HISTORICAL GROUND
375 PROPOSED FINAL CAP GRADES
PROPOSED GRADES
EXISTING
GRADES
HISTORICAL
GRADES
37+59
-
5+00
10+00
SECTION
15+00
A
20+00
25+00
30+00
35+00
550
B 525
500
475
450
425
400
375
HISTORICAL GRADES
CCR UNI BOUN
PROPOSED GRADES
EXISTING GRADES
C
0+00 5+00 10+00 15+00 20+00 25+00 30+00
SECTION B
550
525
500
� 475
450
425
400
CC UNIT B UNDARY
PROPOSED GRADES
HISTORICAL GRADES
EXISTING GRADES � I/
0+00 5+00 10+00 15+00 20+00 25+00 30+00
SECTION C
0 1 2 3 2 TENTHS 10 20 30
550
525
500
475
450
425
400
375
34+42
550
525
500
475
450
425
400
34+42
TITLE
CLOSURE IN PLACE CROSS SECTIONS
MAYO STEAM ELECTRIC PLANT
ASH BASIN CLOSURE OPTIONS EVALUATION
PERSON COUNTY, NORTH CAROLINA
FOR
MAYO PLANT
alh,
DUKE
41 ENERGY
SCALE: 1" = 150'
DES:
RD
DWG TYPE :.DWG
DFTR :
RD
JOB
DATEN0:60518/2018
ENGR:
CP
FILENAME:
CIP GRADING PLAN.DWG
APPD:
DC
DWG SIZE
DRAWING NO.
REVISION
ANSI D
22.0"x 34.0"
FIGURE A2B
O
8
m
G
Q

■
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2 3 4 5 6 7 8 REV. 2
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pf
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��• .tea. ��■ �41 _ ,ter _ .•,• + i� _ L� , •�'�� s •Nr _ii!�• -r'•F ,�5'v�•�'r
CLOSURE
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Ii
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MAYO STEAM ELECTRIC PLANT
ASH BASIN CLOSURE OPTIONS EVALUATION
17A
r 4 ; ��'� ' h L ° t ?■ spec" 7>�
PERSON COUNTY, NORTH CAROLINA
M1 �_ t 6''ti - �r� +�' _ rV •L
� . r� , L _ F� zff4 # sFOR
L=}"`•�.. •� v Y L" s" .�.ti•'17. y �, ■ I PLANTMAYO
r
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SCALE: V=300'
G TYPE: 09 DWG TYPE
a DUKE
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1��}� _ : �_ ' : f" k_ ' ��''r�r it .+,i �.�LFpy T{;• IF Y DATE: 10/18/2018
-� '�{r J y r r
r �! +*i t•'+ENE
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pp
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;;0
m
N

Attachment B

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
AAZCO
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Cost Summary
4
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
Preliminary Promect Costs Sheets
Ash Basin
Hybrid
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Cost Summary: Hybrid Cost Estimate for CCR Impoundment
1
1 Claudia Prado
11/8/2018
1 KK
MAYO PLANT - OPTION 1 HYBRID CLOSURE
Closure & Post Closure Cost Summary
Closure Tasks
Cost
(2018 Dollars)
Mobilization / Site Prep / Demobilization
$5,638,640
Dewatering / Excavation for Closure by Removal / Convey Material
$51,351,289
Dewatering / Earthwork for Close -in -Place
$13,365,422
Lateral Expansion Areas
$3,614 603
Closure System Construction
$7,447,321
Stormwater Management / E&S Controls / Site Restoration
$2,414,762
Contingency (25%)
$20,958,009
Engineering Support (Design & CQA)
$4,500,000
Total Closure Cost of CCR Impoundment =
$109,290,046
Post -Closure Tasks
Cost
(2018 Dollars)
Groundwater Monitoring
$14,790,000
Operations & Maintenance (O&M)
$8,550,468
Contingency (25%)
$5,835,117
Engineering Costs (10%)
$2,917,559
Total Post -Closure of CCR Impoundment =
$32,093,144
Total Closure & Post -Closure of CCR Impoundment Cost = $141,383,190
Preliminary Based on Information Available as of 11/08/2018 1 of 5

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Hybrid Costs
4
JOUCOM
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Hybrid
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Hybrid Closure Costs
1
Claudia Prado
11/08/18
JDP
BASIS OF THE ESTIMATE
YEAR COST BASIS
2018
TOTAL IMPOUNDMENT AREA (AC)
140
TOTAL AREA TO BE RESTORED (AC)
145
VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)
Not Used
IMPOUNDMENT AREA TO BE CLOSED -IN -PLACE (AC)
82
IMPOUNDMENT AREA TO BE CLOSURE BY REMOVAL (AC)
58
EXISTING ASH VOLUME IN AREA TO BE CLOSED -IN -PLACE (CY)
3,850,000
TOTAL ASH VOLUME FROM CLOSURE BY REMOVAL (CY)
1,650,000
TOTAL (FINAL) ASH VOLUME TO BE CLOSED -IN -PLACE (CY)
4,877,950
;'PTH OF CUT -SLOPE AT CLOSE -IN -PLACE / CLOSURE BY REMOVAL INTERFACE
1,100
HYBRID ESTIMATED COSTS
INSTALLED
IMPOUNDMENT
TASK
ITEM
UNIT
QUANTITY
UNIT COST
CLOSURE COST
NOTES
MOBILIZATION / SITE PREP / DEMOBILIZATION
Mob/Demob & insurance: (1 % of Total Bid Price) includes
1
MOBILIZATION / DEMOBILIZATION
LS
1
$903,462
$903,462
administration (mtgs, health & safety, trailer,
MOBILIZATION/
phone/fax/electricity, temporary facilities, utilities, roll off boxes,
SITE PREP/
waste disposal, and cleanup).
DEMOBILIZATION
2
REMOVAL OF OUTLET STRUCTURES / PIPING
LS
1
$994,112
$994,112
Assume outlet structures and piping will be excavated and
removed.
3
REMOVAL & FILTRATION OF FREE WATER
MONTHS
36.0
$103,919
$3,741,066
Based on Initiation time
DEWATERING / EXCAVATION FOR CLOSURE BY REMOVAL / CONVEY MATERIAL
4
REMOVAL & TREATMENT OF PORE WATER WITHIN ASH
MONTHS
60.0
$225,832
$13,549,937
Based on Construction time
IN CLOSURE BY REMOVAL AREA
Assume CCR material must be stockpiled within impoundment
5
EXCAVATE ASH FOR CLOSURE BY REMOVAL /
CY
1,650,000
$8.00
$13,200,000
area to decant prior to loading. Done in conjunction with Step
STOCKPILE ASH
1. Decant water collected and treated along with pore water
DEWATERING /
from Step 1.
EXCAVATION FOR
Once material has decanted, CCRs must be excavated out of
CLOSURE BY
6
EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH TO
CY
1,027,950
$8.43
$8,665,619
stockpile, loaded on trucks and hauled to close -in -place area.
REMOVAL /
CLOSE -IN -PLACE AREA
Quantity takes into consideration reduction of volume due to
CONVEY
dewatering of ash down to 30% moisture content.
MATERIAL
OVER EXCAVATE SOIL FROM CLOSURE BY REMOVAL
Assume 1 foot of additional material to be removed over total
7
AREA / LOAD / HAUL CCR-IMPACTED SOIL TO CLOSE -IN-
CY
93,573
$10
$935,733
closure by removal impoundment area.
PLACE AREA
DEEP MIXING METHOD (DMM) WALL TO STABILIZE CUT-
Assume DMM wall for large ponds that require excavating a
8
SLOPE AT CLOSE -IN -PLACE / CLOSURE BY REMOVAL
L.F.
1,500
$10,000
$15,000,000
portion of the pond and stacking excavated material on
INTERFACE
remaining portion.
9
EXCAVATE / LOAD / HAUL CCR MATERIAL (OFF -SITE)
CY
0
$60
$0
include if applicable
10
EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFF-
CY
0
$57
$0
include if applicable
SITE)
Preliminary Based on Information Available as of 11/08/2018 2 of 5

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Hybrid Costs
4
JOUCOM
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Hybrid
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Hybrid Closure Costs
1
Claudia Prado
11/08/18
JDP
BASIS OF THE ESTIMATE
YEAR COST BASIS
2018
TOTAL IMPOUNDMENT AREA (AC)
140
TOTAL AREA TO BE RESTORED (AC)
145
VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)
Not Used
IMPOUNDMENT AREA TO BE CLOSED -IN -PLACE (AC)
82
IMPOUNDMENT AREA TO BE CLOSURE BY REMOVAL (AC)
58
EXISTING ASH VOLUME IN AREA TO BE CLOSED -IN -PLACE (CY)
3,850,000
TOTAL ASH VOLUME FROM CLOSURE BY REMOVAL (CY)
1,650,000
TOTAL (FINAL) ASH VOLUME TO BE CLOSED -IN -PLACE (CY)
4,877,950
;'PTH OF CUT -SLOPE AT CLOSE -IN -PLACE / CLOSURE BY REMOVAL INTERFACE
1,100
HYBRID ESTIMATED COSTS
INSTALLED
IMPOUNDMENT
TASK
ITEM
UNIT
QUANTITY
UNIT COST
CLOSURE COST
NOTES
DEWATERING / EARTHWORK FOR CLOSE -IN -PLACE
11
REMOVAL & TREATMENT OF PORE WATER WITHIN ASH
MONTHS
0.0
$225,832
$0
Accounted for in closure by removal time frame.
Spread dewatered ash excavated from CLOSURE BY
12
SPREAD AND COMPACT MATERIAL FROM CLOSURE BY
CY
1,027,950
$7.56
$7,771,302
REMOVAL area in thin lifts over close -in -place area. Quantity
DEWATERING /
REMOVAL AREA
takes into consideration reduction of volume due to dewatering
EARTHWORK FOR
of ash down to 30% moisture content.
CLOSE -IN -PLACE
ASH REGRADING TO ESTABLISH CROWN AND
Quantity of earthwork (cut -to -fill) using existing ash to achieve
13
CY
500,000
$9.24
$4,620,000
min. 3% slope prior to installation of closure system. Quantity
SURROUNDING POSITIVE DRAINAGE
calculated using AutoCAD.
14
RING DRAIN INSTALLATION
L.F.
14,000
$58
$806,120
Linear feet around the close -in -place area
15
PERIMETER DITCH / TEMP. DIVERSION BERM GRADING
L.F.
14,000
$12
$168,000
Linear feet around the perimeter of impoundment.
LATERAL EXPANSION AREAS
LATERAL
In areas where ash will be placed outside of the existing ash
EXPANSION
basin waste boundary, this will be considered a Lateral
AREAS
16
LATERAL EXPANSION AREAS
AC
4.5
$803,245
$3,614,603
Expansion per the CCR regulations and will require a
composite liner system with Ieachate collection.
CLOSURE SYSTEM CONSTRUCTION
17
FLEXIBLE MEMBRANE LINER (FML)
SQ. FT.
3,929,112
$0.42
$1,650,227
Flexible membrane liner placed over close -in -place area.
Assume quantity needed is 10% more than close -in -place area.
18
GEOCOMPOSITE DRAINAGE LAYER
SQ. FT.
3,929,112
$0.60
$2,357,467
Geocomposite drainage layer placed over close -in -place area.
Assume quantity needed is 10% more than close -in -place area.
CLOSURE SYSTEM
CONSTRUCTION
19
GEOSYNTHETIC CLAY LINER (GCL)
SQ. FT.
0
$0.72
$0
not used
20
18" PROTECTIVE COVER SOIL
CY
198,440
$13
$2,579,720
18 inches of common soil placed over closure by in place area
21
6" TOPSOIL
CY
66,147
$13
$859,907
6 inches of topsoil placed over closure in place area.
22
COMPACTED LOW PERM. SOILS (Kv<1x10^-5 cm/sec)
CY
0
$12
$0
not used:
Preliminary Based on Information Available as of 11/08/2018 3 of 5

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Hybrid Costs
4
JOUCOM
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Hybrid
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Hybrid Closure Costs
1
Claudia Prado
11/08/18
JDP
BASIS OF THE ESTIMATE
YEAR COST BASIS
2018
TOTAL IMPOUNDMENT AREA (AC)
140
TOTAL AREA TO BE RESTORED (AC)
145
VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)
Not Used
IMPOUNDMENT AREA TO BE CLOSED -IN -PLACE (AC)
82
IMPOUNDMENT AREA TO BE CLOSURE BY REMOVAL (AC)
58
EXISTING ASH VOLUME IN AREA TO BE CLOSED -IN -PLACE (CY)
3,850,000
TOTAL ASH VOLUME FROM CLOSURE BY REMOVAL (CY)
1,650,000
TOTAL (FINAL) ASH VOLUME TO BE CLOSED -IN -PLACE (CY)
4,877,950
;'PTH OF CUT -SLOPE AT CLOSE -IN -PLACE / CLOSURE BY REMOVAL INTERFACE
1,100
HYBRID ESTIMATED COSTS
INSTALLED
IMPOUNDMENT
TASK
ITEM
UNIT
QUANTITY
UNIT COST
CLOSURE COST
NOTES
STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION
23
PERMANENT RIPRAP STORMWATER CHANNELS
TON
7,250
$50
$362,500
Assume 10,000 If x 10 ft. wide x 1 ft. thick, 145 pcf riprap lined
stormwater channels.
STORMWATER
24
SITE EROSION AND SEDIMENT CONTROL
ACRE
145
$2,000
$289,000
Assume total area to be restored will require site erosion and
MANAGEMENT /
sediment control.
E&S CONTROLS /
Assume 12-inches of additional soil material graded over total
SITE
25
BACKFILL AND REGRADING OF CLOSURE BY REMOVAL
CY
93,767
$13
$1,218,967
closure by removal area, to account for material removed by 1
RESTORATION
AREA
foot overexcavation of CCR impacted soils.
26
TOPSOIL
CY
0
$13
$0
Assume 6-inches of top soil needed to establish vegetative
stabilization over total closure by removal area.
27
SEED / FERTILIZE / MULCH
ACRE
145
$3,767
$544,295
Assume total area of disturbance will be mulched, fertilized, and
seeded.
CONTINGENCY / ENGINEERING SUPPORT
CONTINGENCY /
ENGINEERING
28
CONTINGENCY (25%)
LS
1
$20,958,009
$20,958,009
SUPPORT
29
ENGINEERING SUPPORT (DESIGN & CQA)
LS
1
$4,500,000
$4,500,000
POST -CLOSURE
POST -CLOSURE
30
GROUNDWATER MONITORING
ANNUAL
30
$493,000
$14,790,000
Annual groundwater monitoring costs for each CCR impoundment
are based on current groundwater monitoring system
31
OPERATIONS & MAINTENANCE (O&M)
ANNUAL
30
$285,016
$8,550,468
Annual O&M costs are 3475.80/ac/yr. Based on Q3 2018 Post
Closure Maintenance data
CONTINGENCY / ENGINEERING COST
CONTINGENCY /
ENGINEERING
CONTINGENCY (25%)
LS
1
$5,835,117
$5,835,117
COST
ENGINEERING COST (10%)
LS
1
$2,917,559
$2,917,559
TOTAL
$141,383,190
Preliminary Based on Information Available as of 11/08/2018 4 of 5

PROJECT
PLANT NAME:
CLOSURE TYPE:
SHEET
REV. NO.
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Hybrid Assumptions
4
JAZCOM
SUBJECT
IMPOUNDMENT NAME:
CLOSURE METHOD:
CLOSURE YEAR:
AECOM JOB NO.
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Hybrid
0
60432144
ACTIVITY
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Hybid Closure Assumptions
1
Claudia Prado
11/08/18
JDP
KEY ASSUMPTIONS
The following key assumptions and limitations are associated with the project design, implementation and performance:
1
The cost estimates were prepared using 2018 dollars and do not include any escalation.
2
A 25% contingency has been included for this cost estimate.
3
The cost for Engineering Support (Design & CQA) for the Hybrid option assumes $3M for design and $1.5M for CQA (assuming CQA cost is $25K/month for 5 years)
4
The unit rate costs are based on AECOM & Duke experience.
5
Pore water to be partially removed from ash in closure by removal area using combination of open pit dewatering and rim-ditch/wet stack methods until material can be excavated and stockpiled. Assume
saturated ash must be dewatered down to 30% moisture content to haul and place in close -in -place area. Assume treatment for TSS, pH, Arsenic & Selenium. Costs based on AECOM's estimates from
Duke's dewatering projects.
6
Assume pore water removal and treatment is accounted for within close -in -place area time frame. Surface area to be regraded and limited surficial dewatering will be necessary prior to receipt of ash from
closure -by -removal area.
7
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.
8
Assumed all CCR material excavated must be stockpiled in close proximity to the impoundment to be decanted. After decanting, the material will be excavated, loaded, and hauled to an on -site
impoundment to be closed -in -place.
9
Assume all material excavated from areas to be closed by removal will be used for crown construction/soil regrading for closed -in -place areas.
10
Assume an over -excavation of 1 foot is necessary to achieve closure by removal conditions.
11
Cap cross section for the CCR impoundment will consist of (from bottom to top): ash / geomembrane / geocomposite drainage layer / 24" protective cover soil. The top 6-inches will be topsoil, or soil
ammended to enable vegetative growth.
12
Common soil for embankment and protective cover soil construction are available near -site and topsoil would come from offsite
13
Groundwater monitoring costs for CCR impoundment is based on current groundwater monitoring system, as provided by Duke.
14
O&M costs provided by Duke.
15
Statements of Probable Construction Cost prepared by AECOM represent AECOM's judgment as a design professional familiar with the construction industry. It is recognized, however, that neither
AECOM nor the Owner has control over the cost of labor, materials or equipment nor over the contractor's methods of determining the bid price or other competitive bidding, market, or negotiating
conditions. Accordingly, AECOM cannot and does not warrant or represent that proposals, bids or actual construction costs will not vary from any statement of Probable Construction Cost or other
estimates or evaluations prepared by AECOM.
Preliminary Based on Information Available as of 11/08/2018 5 of 5

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
d �COM
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Cost Summary
4
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
►�
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Close -in -Place
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Cost Summary: Close -in -Place Cost Estimate for CCR Surface Impoundment
2
1 Claudia Prado
1 11/8/2018
1 KK
MAYO PLANT - OPTION 2 CLOSURE -IN -PLACE
Closure & Post Closure Cost Summary
Close -in -Place Tasks
Cost
(2018 Dollars)
Mobilization / Site Prep
$3,497,862
Dewatering / Earthwork / Subgrade Prep.
$21,819,450
Closure System Construction
$12,714,938
Stormwater Management / E&S Controls / Site Restoration
$19,349,095
Contingency (25%)
$14,345,336
Engineering Support (Design and CQA)
$2,900,000
Total Closure Cost of CCR Impoundment =
$74,626,681
Post -Closure Tasks
Cost
(2018 Dollars)
Groundwater Monitoring
$14,790,000
Operations & Maintenance (O&M)
$14,598,360
Contingency (25%)
$7,347,090
Engineering Costs (10%)
$3,673,545
Total Post -Closure of CCR Impoundment =
$40,408,995
Total Closure & Post -Closure of CCR Impoundment Cost = $115,035,676
Preliminary Based on Information Available as of 11/08/2018 1 of 4

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
AECOM
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Cost Summary
4
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Close -in -Place
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Close -in -Place Costs
1 2
1 Claudia Prado
11/08/18
JDP
BASIS OF THE ESTIMATE
YEAR COST BASIS
2018
AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)
Not Used
TOTAL AREA TO BE RESTORED (AC)
140
AVG. DEPTH OF FREE WATER (FT)
Not Used
TOTAL IMPOUNDMENT AREA (AC)
140
VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)
Not Used
VOLUME OF ASH IN IMPOUNDMENT (CY)
5,500,000
CLOSE -IN -PLACE ESTIMATED COSTS
INSTALLED
IMPOUNDMENT
TASK
ITEM
UNIT
QUANTITY
UNIT COST
CLOSURE COST
NOTES
MOBILIZATION / SITE PREP
Mob/Demob & insurance: (1% of closure tasks)
1
MOBILIZATION
LS
1
$633,217
$633,217
includes administration (mtgs, health & safety, trailer,
MOBILIZATION/
phone/fax/electricity, temporary facilities, utilities, roll off
SITE PREP
boxes, waste disposal, and cleanup).
2
ABANDON OUTLET STRUCTURES / PIPING
LS
1
$994,112
$994,112
Abandon existing outlet structures and piping.
3
REMOVAL & FILTRATION OF FREE WATER
MONTHS
18.0
$103,919
$1,870,533
Initiation time
DEWATERING / EARTHWORK / SUBGRADE PREP
4
REMOVAL & TREATMENT OF PORE WATER WITHIN ASH
MONTHS
48.0
$225,832
$10,839,950
Construction Time
DEWATERING /
EARTHWORK /
5
RING DRAIN INSTALLATION
L.F.
25,000
$58
$1,439,500
Linear feet around the proposed cap.
SUBGRADE PREP
Quantity of earthwory (cut -to -fill) using existing ash to
6
ASH REGRADING TO ESTABLISH CROWN
CY
1,000,000
$9.24
$9,240,000
achieve min. 1.5% valley profile prior to installation of
closure system. Quantity calculated using AutoCAD.
7
PERIMETER DITCH / TEMP. DIVERSION BERM GRADING
L.F.
25,000
$12
$300,000
Linear feet around the perimeter of impoundment.
CLOSURE SYSTEM CONSTRUCTION
Flexible membrane liner placed over close -in -place area.
8
FLEXIBLE MEMBRANE LINER (FML)
SQ. FT.
6,708,240
$0.42
$2,817,461
Assume quantity needed is 10% more than close -in -place
area.
Geocomposite drainage layer placed over close -in -place
9
GEOCOMPOSITE DRAINAGE LAYER
SQ. FT.
6,708,240
$0.60
$4,024,944
area. Assume quantity needed is 10% more than close -in -
place area.
CLOSURE SYSTEM
CONSTRUCTION
10
GEOSYNTHETIC CLAY LINER (GCL)
SQ. FT.
0
$0.72
$0
not used
11
18" PROTECTIVE COVER SOIL
CY
338,800
$13
$4,404,400
18 inches of common soil placed over closure by removal
area
12
6" TOPSOIL
CY
112,933
$13
$1,468,133
6 inches of topsoil placed over total impoundment area.
13
COMPACTED LOW PERM. SOILS (Kv<1x10^-5 cm/sec)
CY
0
$12
$0
not used:
Preliminary Based on Information Available as of 11/08/2018 2 of 4

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
/ECOM
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Cost Summary
4
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Close -in -Place
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Close -in -Place Costs
1 2
1 Claudia Prado
11/08/18
JDP
BASIS OF THE ESTIMATE
YEAR COST BASIS
2018
AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)
Not Used
TOTAL AREA TO BE RESTORED (AC)
140
AVG. DEPTH OF FREE WATER (FT)
Not Used
TOTAL IMPOUNDMENT AREA (AC)
140
VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)
Not Used
VOLUME OF ASH IN IMPOUNDMENT (CY)
5,500,000
CLOSE -IN -PLACE ESTIMATED COSTS
INSTALLED
IMPOUNDMENT
TASK
ITEM
UNIT
QUANTITY
UNIT COST
CLOSURE COST
NOTES
STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION
STORMWATER
14
EROSION AND SEDIMENT CONTROL
ACRE
140
$2,000
$280,000
Assume total area to be restored will require site erosion
MANAGEMENT /
and sediment control.
E&S CONTROLS /
Assume rip -rap lined stormwater conveyance channels
SITE
15
STORMWATER MANAGEMENT / CHANNELS / LET -DOWNS
L.F.
25,000
$742
$18,541,750
and rip -rap lined let -downs off of cap. Quantity assumed at
RESTORATION
3 times perimeter
16
SEED / FERTILIZE / MULCH
ACRE
140
$3,767
$527,345
Assume total area to be restored will be mulched, fertilized,
and seeded.
CONTINGENCY / ENGINEERING SUPPORT
CONTINGENCY /
ENGINEERING
CONTINGENCY (25%)
LS
1
$14,345,336
$14,345,336
SUPPORT
ENGINEERING SUPPORT (DESIGN & CQA)
LS
1
$2,900,000
$2,900,000
POST -CLOSURE
Annual groundwater monitoring costs for each CCR
POST -CLOSURE
17
GROUNDWATER MONITORING
ANNUAL
30
$493,000
$14,790,000
impoundment are based on current groundwater
monitoring system
18
OPERATIONS & MAINTENANCE (O&M)
ANNUAL
30
$486,612
$14,598,360
Annual O&M costs are 3475.80/ac/yr. Based on Q3
2018 Post Closure Maintenance data
CONTINGENCY / ENGINEERING COST
CONTINGENCY /
ENGINEERING
CONTINGENCY (25%)
LS
1
$7,347,090
$7,347,090
COST
ENGINEERING COST (10%)
LS
1
$3,673,545
$3,673,545
TOTAL
$115,035,676
Preliminary Based on Information Available as of 11/08/2018 3 of 4

PROJECT
PLANT NAME:
CLOSURE TYPE:
SHEET
REV. NO.
A=1 COM
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Close -in -Place Assumptions
4
SUBJECT
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Close -in -Place
60432144
ACTIVITY
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Close -in -Place Assumptions
1 2
1 Claudia Prado
1 11/08/18
1 JDP
KEY ASSUMPTIONS
The following key assumptions and limitations are associated with the project design, implementation and performance:
1
The cost estimates were prepared using 2018 dollars and do not include any escalation.
2
A 25% contingency has been included for this cost estimate.
3
The cost for Engineering Support (Design & CQA) for the Close -in -Place option assumes $2M for design and $900K for CQA (assuming CQA cost is $25K/month for 3 years)
4
The unit rate costs are based on AECOM & Duke experience.
5
Surface area to be regraded and limited surficial dewatering will be necessary.
6
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.
7
To establish the minimum top slopes of 2% (post settlement), assume existing ash will be utilized to establish crown.
8
Cap cross section for the CCR impoundment will consist of (from bottom to top): ash / geomembrane / geocomposite drainage layer / 24" protective cover soil. The top 6-inches will be topsoil, or soil
9
Common soil for embankment and protective cover soil construction are available onsite and topsoil would come from offsite
10
Groundwater monitoring costs are based on values provided by Duke.
11
O&M costs are based on values provided by Duke.
12
Statements of Probable Construction Cost prepared by AECOM represent AECOM's judgment as a design professional familiar with the construction industry. It is recognized, however, that neither
AECOM nor the Owner has control over the cost of labor, materials or equipment nor over the contractor's methods of determining the bid price or other competitive bidding, market, or negotiating
conditions. Accordingly, AECOM cannot and does not warrant or represent that proposals, bids or actual construction costs will not vary from any statement of Probable Construction Cost or other
estimates or evaluations prepared by AECOM.
Preliminary Based on Information Available as of 11/08/2018 4 of 4

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
'CO
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Cost Summary
4
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Closure by Removal
60432144
ACTIVITY:
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Cost Summary: Closure by Removal Cost Estimate for CCR Impoundment
1 3
1 Claudia Prado
1 11/8/2018
1 KK
MAYO PLANT - OPTION 3 CLOSURE BY REMOVAL:
EXISTING ON -SITE LANDFILL
Closure & Post Closure Cost mary
Closure by Removal Tasks
Cost
(2018 Dollars)
Mobilization / Site Prep / Demobilization
$6,349,444
Dewatering / Excavation / Convey Material
$93,563,111
Onsite Landfill Construction, Disposal and Closure
$51,709,494
Stormwater Management / E&S Controls / Site Restoration
$4,179,045
Contingency (25%)
$38,950,274
Engineering Support (Design & CQA)
$5,000,000
Total Closure Cost of CCR Impoundment =
$199,751,368
Post -Closure Tasks
Cost
(2018 Dollars)
Groundwater Monitoring
$14,790,000
Operations & Maintenance (O&M)
$3,128,220
Contingency (25%)
$4,479,555
Engineering Costs (10%)
$2,239,778
Total Post -Closure of CCR Impoundment =
$24,637,553
Total Closure & Post -Closure of CCR Impoundment Cost = $224,388,921
Preliminary Based on Information Available as of 11/08/2018 1 of 4

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
44"7co
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Closure by Removal Costs
4
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Closure by Removal
60432144
ACTIVITY
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Closure By Removal Costs
1 1/3/1900
1 Claudia Prado
1 11/08/18
1 KK
BASIS OF THE ESTIMATE
YEAR COST BASIS
2018
AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)
Not Used
TOTAL AREA TO BE RESTORED (AC)
140
AVG. DEPTH OF FREE WATER (FT)
Not Used
TOTAL IMPOUNDMENT AREA (AC)
140
VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)
Not Used
VOLUME OF ASH IN IMPOUNDMENT (CY)
5,500,000
MOBILIZATION/
SITE PREP/
DEMOBILIZATION
ACHIEVE
CLOSURE BY
REMOVAL/
CONVEY
MATERIAL
ONSITE LANDFILL
CONSTRUCTION,
DISPOSAL AND
CLOSURE
CLOSURE BY REMOVAL ESTIMATED COSTS
INSTALLED
IMPOUNDMENT
TASK
ITEM
UNIT
QUANTITY
UNIT COST
CLOSURE COST
NOTES
MOBILIZATION / SITE PREP / DEMOBILIZATION
Mob/Demob & insurance: (1 % of Total EPC Bid Price) includes
1
MOBILIZATION / DEMOBILIZATION
LS
1
$1,614,266
$1,614,266
administration (mtgs, health & safety, trailer, phone/fax/electricity,
temporary facilities, utilities, roll off boxes, waste disposal, and
cleanup).
2
REMOVAL OF OUTLET STRUCTURES / PIPING
LS
1
$994,112
$994,112
Assume outlet structures and piping will be excavated and
removed.
3
REMOVAL & FILTRATION OF FREE WATER
MONTHS
36.0
$103,919
$3,741,066
Based on Initiation Time
DEWATERING / EXCAVATION / CONVEY MATERIAL
4
REMOVAL & TREATMENT OF PORE WATER WITHIN ASH
MONTHS
84.0
$225,832
$18,969,912
Based on Construction Time
Assume CCR material must be stockpiled within impoundment
EXCAVATE ASH FOR CLOSURE BY REMOVAL / STOCKPILE
area to decant prior to loading. Done in conjunction with Step 1.
5
ASH
CY
5,500,000
$8
$44,000,000
Decant water collected and treated along with pore water from
Step 1.
Once material has decanted, CCRs must be excavated out of
6
EXCAVATE ASH FROM STOCKPILE / LOAD / HAUL ASH
CY
3,426,500
$8
$28,885,395
stockpile, loaded on trucks and hauled to onsite disposal site.
(DISPOSE ON -SITE)
Quantity takes into consideration reduction of volume due to
dewatering of ash down to 30% moisture content.
7
EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (ON -SITE)
CY
225,900
$8
$1,707,804
Assume 1 foot of additional material to be removed over total
impoundment area (including upstream dam face).
8
EXCAVATE / LOAD / HAUL CCR MATERIAL (OFF -SITE LF)
TON
0
$60
$0
Only include if disposing CCRS at an off -site landfill (assume
density of 1.2 tons/cy)
9
EXCAVATE / LOAD / HAUL CCR-IMPACTED SOIL (OFF -SITE LF)
TON
0
$57
$0
Only include if disposing CCRS at an off -site landfill (assume
density of 1.2 tons/cy)
ONSITE LANDFILL CONSTRUCTION, DISPOSAL AND CLOSURE
Assume existing landfill designed and constructed in accordance
with CAMA and CCR Rules. Additional acreage of liner needed to
10
CONSTRUCT ON -SITE LANDFILL AND ASSOCIATED
AC
30
$803,245
$24,097,350
store an additional 5.5 million CY of CCR. Cost includes landfill
COMPONENTS
construction and all associated components, including: liner
system, leachate management, stormwater management, access
roads, closure system and all associated components,etc.
DISPOSE/SPREAD/COMPACT ASH AND CCR-IMPACTED
Place, spread and compact in thin lifts dewatered ash and CCR-
11
MATERIALS FROM CLOSURE BY REMOVAL AREA IN ON -SITE
CY
3,652,400
$8
$27,612,144
impacted materials excavated from closure by removal area into
LANDFILL
landfill.
Preliminary Based on Information Available as of 11/08/2018 2 of 4

PROJECT:
PLANT NAME:
CLOSURE TYPE:
SHEET:
REV. NO.:
44"7co
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Closure by Removal Costs
4
SUBJECT:
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.:
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Closure by Removal
60432144
ACTIVITY
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Closure By Removal Costs
1 1/3/1900
1 Claudia Prado
1 11/08/18
1 KK
BASIS OF THE ESTIMATE
YEAR COST BASIS
2018
AREA OF OPEN FREE WATER IN IMPOUNDMENT (AC)
Not Used
TOTAL AREA TO BE RESTORED (AC)
140
AVG. DEPTH OF FREE WATER (FT)
Not Used
TOTAL IMPOUNDMENT AREA (AC)
140
VOLUME OF FREE WATER IN IMPOUNDMENT (GAL)
Not Used
VOLUME OF ASH IN IMPOUNDMENT (CY)
5,500,000
CLOSURE BY REMOVAL ESTIMATED COSTS
INSTALLED
IMPOUNDMENT
TASK
ITEM
UNIT
QUANTITY
UNIT COST
CLOSURE COST
NOTES
STORMWATER MANAGEMENT / E&S CONTROLS / SITE RESTORATION
10
PERMANENT RIPRAP STORMWATER CHANNELS
TON
8,700
$50
$435,000
Assume 12,000 If x 10 ft. wide x 1 ft. thick, 145 pcf riprap lined
stormwater channels.
STORMWATER
11
SITE EROSION AND SEDIMENT CONTROL
ACRE
140
$2,000
$280,000
Assume total area to be restored will require site erosion and
sediment control.
MANAGEMENT/
E&S CONTROLS /
12
BACKFILL AND REGRADING
CY
225,900
$13
$2,936,700
Assumes entire restoration area with 1 foot of backfill material
SITE
RESTORATION
Assume 6-inches of top soil needed to establish vegetative
13
TOPSOIL
CY
0
$13
$0
stabilization over total closure by removal area.
14
SEED / FERTILIZE / MULCH
ACRE
140
$3,767
$527,345
Assume total area of disturbance will be mulched, fertilized, and
seeded.
CONTINGENCY /
CONTINGENCY / ENGINEERING SUPPORT
ENGINEERING
SUPPORT
CONTINGENCY (25%)
LS
1
$38,950,274
$38,950,274
ENGINEERING SUPPORT (DESIGN & CQA)
LS
1
$5,000,000
$5,000,000
POST -CLOSURE
15
GROUNDWATER MONITORING
ANNUAL
30
$493,000
$14,790,000
Annual groundwater monitoring costs for each CCR unit are based on
POST -CLOSURE
current groundwater monitoring system
16
OPERATIONS & MAINTENANCE (O&M)
ANNUAL
30
$104,274
$3,128,220
Annual O&M costs are 3475.80/ac/yr. Based on Q3 2018 Post
Closure Maintenance data
CONTINGENCY / ENGINEERING COST
CONTINGENCY /
ENGINEERING
CONTINGENCY (25%)
LS
1
$4,479,555
$4,479,555
COST
ENGINEERING COST (10%)
LS
1
$2,239,778
$2,239,778
TOTAL
$224,388,922
Preliminary Based on Information Available as of 11/08/2018 3 of 4

PROJECT
PLANT NAME:
CLOSURE TYPE:
SHEET
REV. NO.
AUXO
CCR IMPOUNDMENT CLOSURE ESTIMATES FOR DUKE ENERGY
Mayo
CCR Rule & CAMA Compliant
Closure by Removal Assumptions
4
SUBJECT
IMPOUNDMENT NAME:
CLOSURE METHOD:
AECOM JOB NO.
^
CALCULATION SHEET
PreliminarV Promect Costs Sheets
Ash Basin
Closure by Removal
60432144
ACTIVITY
CLOSURE OPTION:
LAST UPDATED BY:
DATE LAST MODIFIED:
REVIEWED BY:
Closure by Removal Assumptions
3
Claudia Prado
11/08/18
KK
KEY ASSUMPTIONS
The following key assumptions and limitations are associated with the project design, implementation and performance:
1
The cost estimates were prepared using 2018 dollars and do not include any escalation.
2
A 25% contingency has been included for this cost estimate.
3
The cost for Engineering Support (Design & CQA) for the Closure by Removal w/ Onsite Landfill option assumes $3.5M for design and $1.5M for CQA (assuming CQA cost is $25K/month for 5 years)
4
The unit rate costs are based on AECOM & Duke experience.
5
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.
6
Pore water to be partially removed using combination of open pit dewatering and rim-ditch/wet stack methods until material can be excavated and stockpiled. Assume saturated ash must be dewatered down
to 30% moisture content to haul and dispose on site. Assume treatment for TSS, pH, Arsenic & Selenium. Costs based on AECOM' estimates from Duke's dewatering projects.
7
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.
8
Costs for onsite landfill construction based on current construction and closure cost, as provided by Duke.
9
AECOM has assumed an over -excavation of 1 foot is necessary to achieve closure by removal conditions.
10
Groundwater monitoring costs for CCR unit is based on current groundwater monitoring system, as provided by Duke.
11
O&M costs provided by Duke.
12
Statements of Probable Construction Cost prepared by AECOM represent AECOM's judgment as a design professional familiar with the construction industry. It is recognized, however, that neither AECOM
nor the Owner has control over the cost of labor, materials or equipment nor over the contractor's methods of determining the bid price or other competitive bidding, market, or negotiating conditions.
Accordingly, AECOM cannot and does not warrant or represent that proposals, bids or actual construction costs will not vary from any statement of Probable Construction Cost or other estimates or
evaluations prepared by AECOM.
Preliminary Based on Information Available as of 11/08/2018 4 of 4

Attachment C

Preliminary Scoring for Evaluation
Closure Options Evaluation
Ash Basin Closure - Master
Site Name: Mayo Plant
11/13/2018
Threshold Criteria: All closure options must comply with the following threshold criteria based on Duke Energy Guiding Principles
for Ash Basin Closure
1. Provide continued geotechnical stability meeting appropriate safety factors under applicable loading conditions
2. Provide flow capacity and erosion resistance during design storm and flooding conditions
3. Effectively mitigate groundwater impacts (in conjunction with GW remediation where present)
4. Comply with applicable state and federal regulations (e.g. North Carolina Coal Ash Management Act)
Duke Energy
= Option -Specific User Input
1 = Calculated Value
Option
Hybrid Closure
Closure In Place
Zero (0) values have been entered in "Calculated or User Selected Score" under
Beneficial Reuse to prevent division by zero error text in calculated score cells.
Revision O
1 3 1Cosure By Removal: Existing On -site Landfill I
Environmental Protection and Impacts
Weight: 30%
I _
I _
•
. • • .
Refer to
Modeled plume intersecting surface water
Please refer to the Groundwater Sub -Scoring Document for details
GW Sub -Scoring Sheet
•
•
23.8%
7.1%
Modeled groundwater impact beyond the current
Refer to
Please refer to the Groundwater Sub -Scoring Document for details
compliance boundary
GW Sub -Scoring Sheet
•
•
23.8%
7.1%
Refer to
Modeled off -site groundwater impact
Please refer to the Groundwater Sub -Scoring Document for details
GW Sub -Scoring Sheet
•
•
23.8%
7.1%
Relative rank based on visual interpretation of
Refer to
Please refer to the Groundwater Sub -Scoring Document for details
modeled boron plume
GW Sub -Scoring Sheet
•
•
13.6%
4.1%
Air emissions off -site (based on miles driven round-
Interpolation. Min value
trip)
scores 10. Max value scores 0.
Truck miles driven
Miles • • 0
2
10
10
0
5.0%
1.5%
Air emissions on -site cubic yards of
Interpolation. Min value
excavation/movemen
excavation/movement
scores 10. Max value scores 0.
t
Cu.Yds • off • • off off 1,050,000
6,526,000
7
10
0
5.0%
1.5%
Avoidance of greenfield disturbance
Interpolation. Min value Disturbed acres of
scores 10. Max value scores 0. greenfield
Acres • • 4.5
30
10
0
0
5.0%
1.5%
- •
2.75
2.44
2.55
Cost
Weight: 35%
_
_
•
Closure Cost
Interpolation. Min value Closure Cost
USD •• of •$ 74,626,681
$ 199,751,368
7.2
10.0
0.0
80.0%
28.0%
Operation Maintenance and Monitoring Cost
scores 10. Max value scores 0.
OM&M Cost
USD • • • •: • • $ 24,6371553
$ 40,408,995
5.3
0.0
10.0
20.0%
7.0%
.
2.39
2.80
0.70

Site Name: Mayo Plant
11/13/2018
Preliminary Scoring for Evaluation
Closure Options Evaluation
Ash Basin Closure - Master
Duke Energy
= Option -Specific User Input
1 = Calculated Value
Zero (0) values have been entered in "Calculated or User Selected Score" under
Beneficial Reuse to prevent division by zero error text in calculated score cells.
Revision O

Revision O
Criteria for Evaluation of Closure Options
Closure Options Evaluation Worksheet
Ash Basin Closure - Master Programmatic Document
Duke Energy
Threshold Criteria: All closure options must comply with the following threshold criteria based on Duke Energy Guiding
Principles for Ash Basin Closure
1. Provide continued geotechnical stability under applicable loading conditions and safety factors
2. Provide flow capacity and erosion resistance during design storm and flooding conditions
3. Effectively mitigate groundwater impacts
4. Comply with applicable state and federal regulations (e.g. North Carolina Coal Ash Management Act)
Category
Criterion
Guidance
Modeled plume intersecting surface water
Please refer to the Groundwater Sub -Scoring Document for details
Modeled groundwater impact beyond the current compliance boundary
Please refer to the Groundwater Sub -Scoring Document for details
Modeled off -site groundwater impact
Please refer to the Groundwater Sub -Scoring Document for details
Relative rank based on visual interpretation of modeled boron plume
Please refer to the Groundwater Sub -Scoring Document for details
Air emissions off -site (based on miles driven round-trip)
Based on truck miles driven for hauling CCR and soil.
Air emissions on -site cubic yards of excavation/movement
Based on total cubic yards of cut and fill on site as a surrogate for gallons of fuel
consumed.
Avoidance of greenfield disturbance
Refer to Scoring System and Required Input columns on scoring sheet.
•
Capital Cost
From rough order -of -magnitude cost estimate or detailed cost estimate.
Operation, Maintenance and Monitoring Cost
Initiation Time
From preliminary schedule for designing, permitting, bidding and constructing the
option.
Construction Duration
Plan or potential for beneficial reuse of site
Refer to Scoring System and Required Input columns on scoring sheet.
Imported soil needs
Refer to Scoring System and Required Input columns on scoring sheet.
Beneficial reuse of CCR
Refer to Scoring System and Required Input columns on scoring sheet.
Transportation impact
Based on truck miles driven for hauling CCR and CCR-contaminated soil.
Noise impact due to on -site activity
Based on proximity of neighbors to specific on -site work areas.
View impact
I Based on final height of storage facility and land uses within viewshed.
Consider stormwater management, geotechnical, and dewatering
ISubjective and relative comparison to other options

Environmental Groundwater Sub -scoring Worksheet
Closure Options Evaluation
Duke Energy
Station/Plant Name: Mayo Steam Electric Plant
Scored .11/9/18
Evaluation Criteria:
Criteria 1. Modeled Plume Intersecting Surface Water
Modeled plume' does not intersect surface waters after 10 years
10
Modeled plume' does not intersect surface waters after 100 years
5
Modeled plume' does not intersect surface waters after 200 years
0
(Option 1)
(Option 2)
(Option 3)
Closure By Removal: Existing
Hybrid
Closure
Closure In Place
Onsite Landfill
Criteria 1 Score
10
10
10
Criteria 2. Groundwater Impact Beyond the current z Compliance Boundary
SI - (--
Modeled plume' is within current compliance boundary after 10 years
10
Modeled plume' is within current compliance boundary after 100 years
5
Modeled plume' is within current compliance boundary after 200 years
0
(Option 1)
(Option 2)
(Option 3)
Closure By Removal: Existing
Hybrid
Closure
Closure In Place
Onsite Landfill
Criteria 2 Score
10
10
10
Criteria 3. Modeled Off-stte Impact
'--
Modeled plume' does not go off -site
10
Modeled plume' is predicted to remain off -site after 100 years
5
Modeled plume' is predicted to remain off -site after 200 years
0
(Option 1)
(Option 2)
(Option 3)
Closure By Removal: Existing
Hybrid
Closure
Closure In Place
Onsite Landfill
Criteria 3 Score
10
10
10
Criteria 4. Relative rank based on visual interpretation of modeled boron plume
Score
Ranked #1 among the three Closure Options based on visual interpretation of modeled boron plume
10
Ranked #2 among the three Closure Options based on visual interpretation of modeled boron plume
5
Ranked #3 among the three Closure Options based on visual interpretation of modeled boron plume
0
(Option 1)
(Option 2)
(Option 3)
Closure By Removal: Existing
Hybrid
Closure
Closure In Place
Onsite Landfill
Criteria 4 Score
5
0
10
Note 1: Based on avaliable data at the time of scoring, the modeled plume considered boron at
a concentration of 4,000 ug/I or greater;
4,000 Vg/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.
Note 2: The current compliance boundary is the compliance boundary found in the figure "Waste
and Compliance Boundaries" provided
to
NCDEQ on 2/15/18

Environmental Groundwater Sub -scoring Worksheet
Closure Options Evaluation
Duke Energy
Mayo Ash Basin Groundwater Sub -Scoring Document Justification
(Option 1) (Option 2) (Option 3)
Justification Notes
Hybrid Closure Closure In Place Closure By Removal: Existing Onsite Landfill
1
Criteria 1. Modeled Plume Intersectinq Surface
10
is
10
Based on the predictive model for the year 2027, found in the November
Based on the predictive model for the year 2027, found in the
Based on the predictive model for the year 2027, found in the November
Water
2018 Preliminary Updated Groundwater Flow and Transport Modeling
November 2018 Preliminary Updated Groundwater Flow and
2018 Preliminary Updated Groundwater Flow and Transport Modeling
Report for Mayo Steam Electric Plant, simulated boron concentrations for
Transport Modeling Report for Mayo Steam Electric Plant, simulated
Report for Mayo Steam Electric Plant, simulated boron concentrations for
the Hybrid Closure scenario with natural attenuation did not show boron
boron concentrations for the Closure -In -Place scenario with natural
the Closure By Removal scenario with natural attenuation did not show
of 4,000 ppb or greater intercepting surface water bodies.
attenuation did not show boron of 4,000 ppb or greater intercepting
boron of 4,000 ppb or greater intercepting surface water bodies.
surface water bodies.
Criteria 2. Groundwater Impact Beyond the Current
10
10
Compliance Boundary
Based on the predictive model summary of concentrations over time,
Based on the predictive model summary of concentrations over time,
Based on the predictive model summary of concentrations over time,
lboron
model found in the November 2018 Preliminary Updated Groundwater
found in the November 2018 Preliminary Updated Groundwater Flow
found in the November 2018 Preliminary Updated Groundwater Flow and
Flow and Transport Modeling Report for Mayo Steam Electric Plant,
and Transport Modeling Report for Mayo Steam Electric Plant,
Transport Modeling Report for Mayo Steam Electric Plant, simulated
simulated boron concentrations for theHybrid Closure scenario with
simulated boron concentrations for the Closure -In -Place scenario with
concentrations for the Closure By Removalscenario with natural
natural attenuation did not show boron of 4,000 ppb or greater beyond
natural attenuation did not show boron of 4,000 ppb or greater
attenuation did not show boron of 4,000 ppb or greater beyond the
the current (2018) compliance boundary (Point 1).
beyond the current (2018) compliance boundary (Point 1).
current (2018) compliance boundary (Point 1).
Criteria 3. Modeled Off -site Impact
Based on the predictive model for the year 2017 and beyond, found in the
Based on the predictive model for the year 2017 and beyond, found in
Based on the predictive model for the year 2017 and beyond, found in the
November 2018 Preliminary Updated Groundwater Flow and Transport
the November 2018 Preliminary Updated Groundwater Flow and
November 2018 Preliminary Updated Groundwater Flow and Transport
Modeling Report for Mayo Steam Electric Plant, simulated boron
Transport Modeling Report for Mayo Steam Electric Plant, simulated
Modeling Report for Mayo Steam Electric Plant, simulated boron
concentrations for the Hybrid Closure scenario with natural attenuation
boron concentrations for the Closure -In -Place scenario with natural
concentrations for the Closure By Removal scenario with natural
did not show boron of 4,000 ppb or greater off of Duke Energy property.
attenuation did not show boron of 4,000 ppb or greater off of Duke
attenuation did not show boron of 4,000 ppb or greater off of Duke
Energy property.
Energy property.
Criteria 4. Relative rank based on visual
s
o
1
interpretation of modeled boron plume
Based on a review of boron concentrations found in the November 2018
a review of boron concentrations found in the November
r8e
Based on a review of boron concentrations found in the November 2018
Preliminary Updated Groundwater Flow and Transport Modeling Report
minary Updated Groundwater Flow and Transport Modeling
Preliminary Updated Groundwater Flow and Transport Modeling Report
for Mayo Steam Electric Plant, this scenario is marginally better than
Mayo Steam Electric Plant, this scenario is not marginally
for Mayo Steam Electric Plant, this scenario is marginally better than
Option 2 Closure -in -Place.
n Option 1 Hybrid Closure or Options 3 Closure By Removal.
Option 1 Hybrid Closure and Option 2 Close -In -Place.
Notes:
1. Based on avaliable data at the time of scoring, the modeled plume considered boron at a concentration of 4,000 ug/I or greater; 4,000 µg/L does not represent a remediation goal, however this concentration does represent the
EPA Tap Water Regional Screening Level (RSL) in resident tapwater for boron.
2. The current compliance boundary, as of 10/9/18, was used for all scenarios for criteria 2.