NC0005088_CSS_Appendix M_20191231

Corrective Action Plan Update December 2019
Cliffside Steam Station
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REMEDIATION ALTERNATIVE SUMMARY
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Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
Q
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users to
the municipal water supply within a half -mile of the ash basin
compliance boundaries.
Environment
The CSS Source Area 1 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix E).
B. Compliance with Applicable Regulations
Federal
MNA complies with USEPA CCR Rule specified in 40 Code
of Federal Regulations (CFR) § 257.
State
MNA will comply with Coal Ash Management Act of 2014
and 15A NCAC 02L .0106(I). If approved and subject to
notification requirements including the NC Department of
Transportation and NCDEQ for Sediment and Erosion
Control associated with monitoring well installation for
effectiveness monitoring. For additional details on MNA
see Appendix I.
Local
MNA would be subject to notification requirements to any
affected parties and to Rutherford County officials per
15A NCAC 02L .0114(b).
C. Technical & Logistical Feasibility
Ability to construct and operate technology
There are 160 monitoring wells already installed related to the
AAB and ASA. Other than abandonment of selected wells for
basin closure and potential installation of additional monitoring
wells, no significant construction is required for implementation.
Reliability of technology
MNA has been used successfully to achieve remedial objectives
for a wide range of COIs and geologic settings either as a stand
alone remedy, or in combination with other remediation
approaches. The CSM supports the reliability of an MNA
approach.
Ease of undertaking additional RAs if necessary
Other remedial technologies have commonly been used in
conjunction with MNA. Use of MNA will not adversely impact the
implementation of other potential remedial actions.
Ability to monitor effectiveness of remedy
Effectiveness is monitored through evaluation of COI
concentrations over time in accordance with a groundwater
effectiveness monitoring program.
Ability to coordinate and obtain approvals from
other agencies
MNA does not require interaction with other agencies to
implement.
Availability of services and materials
An extensive groundwater monitoring well network already
exists. Additional monitoring wells may be required to complete
the MNA well network. All services and materials are readily
available to support effectiveness monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
There are no requirements for bench scale testing to implement
MNA.
Design
MNA is readily implementable. The existing monitoring well
network can be utilized to design the MNA network.
Permitting
Soil Erosion and Sediment Control permits are required for any
land disturbance, including well installation activities. These
permits are a straightforward to procure.
Page 1 of 9

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
.a
Q
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
E. Short-term Effectiveness
Protection of Community
The surrounding community would not be affected during
implementation of MNA activities performed on Duke Energy
property. Any increase in traffic on roads leading to CSS due to
the nature of the work would be de minimis.
Worker Protection
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers and
the environment. All personal will be require relavent training
and supporting documentation to verify compentency.
Environmental Impacts
There would be some migration of COI affected groundwater
would be expected as part of the attenuation process.
However, human health and ecological risk assessments do not
indicate significant risks.
Time Until Action is Complete
Predictive groundwater modeling indicates compliance to
regulatory standards at the compliance boundary in
approximately 400 years following basin closure.
F. Long-term Effectiveness
Adequacy and Reliability of Controls
Implementation and maintenance of an effectiveness monitoring
program will be in place to evaluate variations from expected
conditions. Alternative measures can be taken to address
variations. Potential risks to groundwater users is further
controlled by the installation of water filtration systems for water
supply well within a 0.5-mile radius of the ash basin compliance
boundaries. Implementation of institutional controls may include
a restricted designation to further protect potential groundwater
users.
Magnitude of Residual Risk
Implementation of MNA will not result in increased residual risk,
as the current state and predicted future state does not indicate
unacceptable risk to human health or environment. Potential
risks to groundwater is further controlled by connection of 70
water supply users to the municipal water supply within a 0.5-
mile radius of the ash basin compliance boundaries.
Implementation of institutional controls may include a restricted
designation to further protect potential groundwater users.
Mobility,G. Reduction of Toxicity,
Treatment Process Used and Materials Treated
None. Relies on natural attenuation processes and mechanisms
such as dispersion and dilution to reduce COI concentrations to
below 02L standards.
Volume of Materials Destroyed or Treated
None. COIs are inorganic and cannot be destroyed; however,
COIs will be removed from groundwater through geochemical
processes.
Degree of Expected Reductions
COI concentration reductions will occur over time and are
anticipated to meet regulatory standards in approximately 400
years.
Irreversible Treatment
None. Natural processes are not anticipated to be reversible
based on results of extensive geochemical modeling; however,
variations in pH and reduction -oxidation in the geochemical
environment can change effectiveness.
Type and Quantity of Residuals Remaining
None. The natural attenuation processes do not create additional
residuals for inorganic COIs.
02L Standards at the Compliance Boundary
The flow and transport model predicts that concentrations of
COIs would meet 02L standards at the compliance boundary in
approximately 400 years after ash basin closure.
Page 2 of 9

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
.a
Q
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Costs to Implement Remedial Alternative 1
The estimated costs to implement this Remediation
Alternative have not been developed.
Life cycle costs are determined using a Net Present Value
(NPV) of expenditures for initial Capital costs and annual O&M
expenses for the duration of the remedy. A Discount Rate of
5% assumed in developing the cost estimate.
Costs would also include the needed labor and materials to
implement the Alternative and, as necessary, routine labor for
annual and 5-year reporting.
J. Community Acceptance K. Adaptive Site Management
Stakeholder Sentiment Regarding
Ability to Augment the Remedy, if Needed
Implementation
It is expected that there will be positive and negative MNA is an adaptable process. Long-term groundwater
sentiment about implementation of an MNA program. No monitoring implemented as part of MNA and can be an
landowner is affected and groundwater COIs do not pose an effective tool in identifying the need for alternative
unacceptable risk to potential human or ecological receptors. approaches if unexpected changes in Site conditions occur
The remaining property is owned by Duke Energy, which is
An MNA program would not hinder or preempt the use of
anticipated to have institutional controls. Some community
other remedial approaches in the future if conditions
stakeholders might consider a 400-year time frame to
change. In fact, an effectiveness monitoring program is an
achieve remediation goals for boron to be unacceptable.
essential part of any future remedial strategy. An MNA
However, community stakeholders with concerns regarding
effectiveness monitoring program would provide
the capital and near -term O&M costs associated with active
information about changing Site conditions during and
remediation may favor a less costly alternative.
after source control measures.
Until the final corrective action is developed and comments
are received and reviewed, assessment of community
acceptance will not be fully informed.
Environmental Footprint of the Remedy
The MNA remedy will impact the environment through energy
consumption and associated emissions associated with
installation of additional monitoring wells and sampling and
analysis of groundwater.
Some clearing of wooded areas would be required to install
monitoring wells and maintain access for sampling activities.
Maintenance of access will also require energy consumption.
Alternative 1 utilizes significantly fewer resources during
construction and throughout the remedial timeframe when
compared to the other remedial alternatives. Therefore,
Alternative 1 is the least energy -intensive of the remedial
alternatives being considered, providing reduced,
comparative environmental footprint metrics in overall energy
use and across all air emission parameters.
Page 3 of 9

Remediation Alternatives
Remediation Alternative 2
Groundwater Extraction and
Infiltration Wells
Groundwater extraction would rely
on groundwater extraction to
remove groundwater COIs and to
reduce COI concentrations in
groundwater over time to meet
corrective action goals. Infiltration
wells would use clean water to
flush COIs from vadose zone soil
and dewatered soil. The
introduction of water to the
shallow and deep flow zones would
also enhance groundwater
extraction. This remedy would use
23 groundwater extraction wells,
46 clean water injection wells, and
1 horizontal injection well.
Extracted groundwater would be
pumped to the Basement Basin
WWTP where it would be treated
and discharged through the
existing NPDES system.
N
Q
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users to
the municipal water supply within a half -mile of the ash basin
compliance boundaries.
Predictive flow and transport modeling indicate that the 02L
standard for boron could be achieved outside the compliance
boundary in approximately 6 years using active groundwater
remedial measures. Remedial Alternative 2 will achieve a
higher degree of protection for human health and the
environment in a much shorter time -frame when compared to
Remedial Alternative 1 (MNA).
Environment
The CSS Source Area 2 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix Q.
B. Compliance with Applicable Regulations
Federal
The groundwater extraction and treatment specified in
Remediation Alternative 2 would comply with USEPA CCR
Rule specified in 40 Code of Federal Regulations (CFR) §
257.
State
Alternative 2 complies with the Coal Ash Management Act
of 2014,15A NCAC 02L regulations and NCAC 02B
regulations. NPDES permitted discharge is in place. The
NPDES Permit may need to be modified to accommodate
the discharge of treated groundwater. Procurement of
Sediment and Erosion Control permits associated with
extraction, infiltration, and monitoring well installation is
a straight -forward process.
Local
Groundwater extraction, infiltration, and treatment can be
implemented in compliance with local laws and
regulations.
C. Technical & Logistical Feasibility
Ability to construct and operate technology
Technologies to construct and operate a groundwater extraction
system, vertical and horizontal infiltration wells are available.
Technologies to treat extracted groundwater exist, but require
experience to successfully operate.
Reliability of technology
Groundwater extraction and infiltration are mature technologies
and have been used to implement cleanup strategies for similar
COIs, but are dependent on subsurface conditions and
effectiveness of treatment approaches. Issues such as well
fouling must be considered during the detailed design process.
Ease of undertaking additional RAs if necessary
The technology doesn't preclude implementation of other
remedial alternatives, if warranted. Groundwater extraction or
infiltration wells can be added to the proposed system or
removed from service, as warranted.
Ability to monitor effectiveness of remedy
Multiple methods can be used to monitor system effectiveness.
An effectiveness monitoring plan would be implemented to
track changes in COI concentrations over time. A system
Operations and Maintenance (O&M) plan would be implemented
to track the gallons of water extracted, infiltrated, and the COI
mass removed on a cumulative basis. Ongoing review of data
and periodic updates to the groundwater modeling would be
performed.
Ability to coordinate and obtain approvals from
other agencies
Soil erosion and sediment control permits are relatively
straightforward and can be obtained readily. The existing
NPDES permit would need to be modified to allow for the
discharge of treated groundwater from Outfall 005.
Availability of services and materials
All services and materials are readily available to support the
remediation alternative. An extensive groundwater monitoring
well network already exists to support effectiveness monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
Additional hydrogeologic testing, including pilot testing, may be
required to complete the design, to address heterogeneous
subsurface conditions, and confirm model predictions. Collection
of dynamic groundwater quality data from wells may be required
to confirm treatment options and design of any treatment
facilities if management of groundwater in the WWTP, or
discharge under the existing NPDES permit is not viable.
Design
Detailed design activities would commence upon approval of the
CAP Update by NCDEQ. Full scale design is dependent on
hydrogeologic testing and bench testing, as required, to develop
more accurate flow rates and estimates of extracted
groundwater quality. Final locations of extraction points,
conveyance piping, electrical service, tankage and potential
treatment units would be confirmed. Detailed design of
electrical, mechanical and controls components would then be
finalized for bidding and construction.
Permitting
Soil erosion and sediment control permits are required for
installation of wells and other infrastructure that include ground
disturbance (e.g., conveyance piping). The NPDES permit can be
modified if required for the discharge of treated groundwater.
Page 4 of 9

Remediation Alternatives
Remediation Alternative 2
Groundwater Extraction and
Infiltration Wells
Groundwater extraction would rely
on groundwater extraction to
remove groundwater COIs and to
reduce COI concentrations in
groundwater over time to meet
corrective action goals. Infiltration
wells would use clean water to
flush COIs from vadose zone soil
and dewatered soil. The
introduction of water to the
shallow and deep flow zones would
also enhance groundwater
extraction. This remedy would use
23 groundwater extraction wells,
46 clean water injection wells, and
1 horizontal injection well.
Extracted groundwater would be
pumped to the Basement Basin
WWTP where it would be treated
and discharged through the
existing NPDES system.
Q
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
E. Short-term Effectiveness
Protection of Community during remediation
Community will not be impacted during active remediation and
monitoring activities as they would be performed on Duke
Energy property. Any anticipated increase in traffic on roads
leading to CSS due to nature of the work would be de minimis.
Protection of workers during remediation
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers and
the environment. All personal will be require relavent training
and supporting documentation to verify compentency.
Environmental impacts
Remedial Alternative 2 has increased energy consumption to
operate the extraction, infiltration, and treatment system and
will require additional energy for construction to manufacture
piping, well materials, and to excavate trenches for piping and
utilities. Environmental impacts associated with clearing to
install wells and supporting infrastructure would be minimal
and work would be performed with a soil erosion and sediment
control permit.
Time Until Action is Complete
Predictive modeling indicates compliance to regulatory
standards at the compliance boundary in 6 years after the
system is placed into operation.
F. Long-term Effectiveness
Adequacy and reliability of controls
Implementation and maintenance of an effectiveness monitoring
program would be in place to evaluate variations in water quality
from expected conditions. Alternative measures can be taken to
address variations, if warranted. Potential risks to groundwater
users is further controlled by the connection of water supply users
to municipal water service within 0.5 miles of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users. An Operations & Maintenance plan will be
developed and implemented to operate the remedial system
within design parameters and document long-term maintenance.
Magnitude of Residual Risk
Implementation of a groundwater extraction and treatment
system will not result in increased residual risk, as the current
state and predicted future state does not indicate unacceptable
risk to human health or environment. Potential risks to
groundwater is further controlled by water filtration systems to
water supply users within a 0.5-mile radius of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users.
G. Reduction of Toxicity, Mobility, &Volume
Treatment process used and materials treated
Treatment of the affected groundwater would be performed
using the plant WWTP.
Volume of materials destroyed or treated
COIs would be removed from the groundwater, treated and
discharged under an NPDES permit in accordance with applicable
regulatory requirements.
Degree of expected reductions
COI concentration reductions are anticipated to meet regulatory
standards in a 6-year timeframe.
Irreversible Treatment
Mass removal would not be reversible for COIs. In -situ
treatment of COIs would not be reversible under stable
geochemical conditions.
Type and quantity of residuals remaining
Residuals may be present below regulatory standards as the
system would be intended to meet standards over time.
Residuals removed through groundwater treatment for COIs
would be managed in accordance with applicable regulatory
requirements.
02L Standards at the Compliance Boundary
The flow and transport model predicts that concentrations of
COIs would meet 02L standards at the compliance boundary in
approximately 6 years after implementation and ash basin
closure.
Page S of 9

Remediation Alternatives
Remediation Alternative 2
Groundwater Extraction and
Infiltration Wells
Groundwater extraction would rely
on groundwater extraction to
remove groundwater COIs and to
reduce COI concentrations in
groundwater over time to meet
corrective action goals. Infiltration
wells would use clean water to
flush COIs from vadose zone soil
and dewatered soil. The
introduction of water to the
shallow and deep flow zones would
also enhance groundwater
extraction. This remedy would use
23 groundwater extraction wells,
46 clean water injection wells, and
1 horizontal injection well.
Extracted groundwater would be
pumped to the Basement Basin
W WTP where it would be treated
and discharged through the
existing NPDES system.
N
Q
tY
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Costs to Implement Remedial Alternative 2
Capital Costs
$538,400.00
Annual O&M Costs
$661,000.00
Total Life Cycle Costs
$8,696,000.00
Costs are based on the labor and materials required for the
installation of 3 monitoring wells, 23 groundwater extraction
wells and 46 vertical and 1 horizontal infiltration wells.
Extracted water will be treated and discharged through the
existing NPDES system. Life cycle represents NPV of
expenditures with an assumed discount Rate of 5%.
Stakeholder Sentiment Regarding
Implementation
It is expected that there will be positive and negative
sentiment about implementation of an active groundwater
remedy that includes extraction, infiltration, and treatment.
No landowner is anticipated to be affected and groundwater
COIs do not pose an unacceptable risk to potential human or
ecological receptors. The remaining affected property is
owned by Duke Energy, which is anticipated to implement
institutional controls.
It is anticipated that the treated groundwater would be
discharged through a NPDES permitted outfall that flows to
the Broad River and the discharge would be treated as
necessary to meet permit limits.
A groundwater extraction and infiltration system that
addresses the COI plume may improve public perception. It
is anticipated that groundwater extraction, infiltration, and
treatment would generally receive more positive community
acceptance than MNA since it involves more active measures
to extraction and reduce COI mass from groundwater. This
alternative would likely be percieved as more robust than
MNA in addressing groundwater impacts even if human
health and ecological risks are essentially the same between
MNA and groundwater extraction.
Until the final Site remedy is developed and comments are
received and reviewed, assessment of community acceptance
will not be fully known.
Ability to Augment the Remedy, if Needed
Groundwater extraction and infiltration using conventional
well technology is an adaptable process. It can be easily
modified to address changes to COI plume configuration
or COI concentrations based on actual field data.
Individual well pumping rates can be adjusted or
eliminated, or additional wells can be installed to address
COI plume changes.
While it is not expected, treatment of the groundwater
discharge can be modified to address changes in COI
concentrations or permit limits.
The horizontal infiltration well used as part of this
Alternative is not as adaptable as the conventional wells.
However, the flow rate to the well can be adjusted or the
well can be eliminated to prevent interferance with other
remediation systems, if necessary.
Environmental Footprint of the Remedy
Sustainability analysis was conducted to quantify the
environmental footprint of each remedial alternative based on
energy use and associated emissions, during the construction
phase, active remediation, and groundwater monitoring
activities.
The environmental footprint of Alternative 2 is the second -
most, energy -intensive remedial alternative being
considered. Alternative 1 (MNA) requires significantly less
materials and energy than Alternative 2 and is therefore
characterized by a dramatically smaller environmental
footprint. Alternative 2 presents lower, but generally
comparable, environmental footprint metrics when measured
against Alternative 3. Alternative 2 utilizes recharge -wells
rather than an infiltration gallery as used in Alternative 3,
generating a lower material -related environmental footprint
for the construction phase. The quantitative analysis of the
environmental footprints of the remedial alternatives under
consideration for this CAP indicates Alternative 2 to be the
more sustainable option, although not significantly less
impactful than Alternative 3. Opportunities for system
optimization and energy savings could be pursued throughout
the remediation timeframe, as conditions change and
component technologies possibly evolve.
The quantitative analysis of the environmental footprints of
the remedial alternatives under consideration for this CAP
indicates Alternative 2 to be the second most sustainable
option.
Page 6 of 9

Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction
with Clean Water
Infiltration and Treatment
Groundwater extraction would rely
on groundwater extraction to
remove groundwater COIs and to
reduce COI concentrations in
groundwater over time to meet
corrective action goals. Infiltration
wells would use clean water to
flush COIs from vadose zone soil
and dewatered soil. The
introduction of water to the
shallow and deep flow zones would
also enhance groundwater
extraction. This remedy would use
3 vertical groundwater extraction
wells, 1 horizontal groundwater
extraction well, 12 clean water
injection wells, and 6 acre
infiltration gallery. Extracted
groundwater would be pumped to
the Basement Basin WWTP where
it would be treated and discharged
through the existing NPDES
system.
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users to
the municipal water supply within a half -mile of the ash basin
compliance boundaries.
Predictive flow and transport modeling indicate that the 02L
standard for boron could be achieved outside the compliance
boundary in approximately 6 years using active groundwater
remedial measures. Remedial Alternative 3 will achieve a
higher degree of protection for human health and the
environment in a much shorter time -frame when compared to
Remedial Alternative 1 (MNA).
Environment
The CSS Source Area 3 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix Q.
B. Compliance with Applicable Regulations
Federal
The groundwater extraction, infiltration and in -situ
treatment specified in Remediation Alternative 3 would
comply with USEPA CCR Rule specified in 40 Code of
Federal Regulations (CFR) § 257.
State
Alternative 3 complies with the Coal Ash Management Act
of 2014,15A NCAC 02L regulations and NCAC 02B
regulations. NPDES permitted discharge is in place. The
NPDES Permit may need to be modified to accommodate
the discharge of treated groundwater. Procurement of
Sediment and Erosion Control permits associated with
extraction and monitoring well installation is a straight-
forward process.
Local
Groundwater extraction and infiltration can be
implemented in compliance with local laws and
regulations.
C. Technical & Logistical Feasibility
Ability to construct and operate technology
Technology to construct and operate Remediation Alternative 3
is straightforward and available. Technologies to treat
extracted groundwater exist but are less straight -forward to
operate.
Reliability of technology
Groundwater extraction with clean water infiltration is a mature
technology and has been used to implement cleanup on similar
COIs. It is strongly dependent on subsurface conditions and
effectiveness of treatment approaches.
Ease of undertaking additional RAs if necessary
The technology doesn't preclude implementation of other
remedial alternatives. Groundwater extraction or infiltration
wells can be added to the proposed system or removed from
service, as warranted.
Ability to monitor effectiveness of remedy
Multiple methods can be used to monitor system effectiveness.
An effectiveness monitoring plan would be implemented to
track changes in COI concentrations over time. A system
Operations and Maintenance (O&M) plan would be implemented
to track the gallons of water extracted and infiltrated, the COI
mass removed on a cumulative basis. Ongoing review of data
and periodic updates to the groundwater modeling would be
performed.
Ability to coordinate and obtain approvals from
other agencies
Soil erosion and sediment control permits are relatively
straightforward and can be obtained readily. The existing
NPDES permit would need to be modified to allow for the
discharge of treated groundwater from Outfall 005.
Availability of services and materials
All services and materials are readily available to support the
remediation alternative. An extensive groundwater monitoring
well network already exists to support effectiveness monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
Additional hydrogeologic testing, including pilot testing, may be
required to complete the design, to address heterogeneous
subsurface conditions, and confirm model predictions. Collection
of dynamic groundwater quality data from wells may be required
to confirm treatment options and design of any treatment
facilities if management of groundwater in the WWTP, or
discharge under the existing NPDES permit is not viable.
Design
Detailed design activities would commence upon approval of the
CAP Update by NCDEQ. Full scale design is dependent on
hydrogeologic testing and bench testing, as required, to develop
more accurate flow rates and estimates of extracted
groundwater quality. Final locations of extraction points,
conveyance piping, electrical service, tankage and potential
treatment units would be confirmed. Detailed design of
electrical, mechanical and controls components would then be
finalized for bidding and construction.
Permitting
Soil erosion and sediment control permits are required for
installation of wells and other infrastructure that include ground
disturbance (e.g., conveyance piping). The NPDES permit can be
modified if required for the discharge of treated groundwater.
Page 7 of 9

M
a
Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction
with Clean Water
Infiltration and Treatment
Groundwater extraction would rely
on groundwater extraction to
remove groundwater COIs and to
reduce COI concentrations in
groundwater over time to meet
corrective action goals. Infiltration
wells would use clean water to
flush COIs from vadose zone soil
and dewatered soil. The
introduction of water to the
shallow and deep flow zones would
also enhance groundwater
extraction. This remedy would use
3 vertical groundwater extraction
wells, 1 horizontal groundwater
extraction well, 12 clean water
injection wells, and 6 acre
infiltration gallery. Extracted
groundwater would be pumped to
the Basement Basin WWTP where
it would be treated and discharged
through the existing NPDES
system.
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
E. Short-term Effectiveness
Protection of Community during remediation
Community will not be impacted during active remediation and
monitoring activities as they would be performed on Duke
Energy property. Any anticipated increase in traffic on roads
leading to CSS due to nature of the work would be de minimis.
Protection of workers during remediation
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers and
the environment. All personal will be require relavent training
and supporting documentation to verify compentency.
Environmental impacts
Remedial Alternative 3 has increased energy consumption to
operate the extraction, infiltration, and treatment system and
will require additional energy for construction to manufacture
piping, well materials, and to excavate trenches for piping and
utilities. Environmental impacts associated with clearing to
install wells and supporting infrastructure would be significant
and work would be performed with a soil erosion and sediment
control permit.
Time until RA objectives are achieved
Predictive modeling indicates compliance to regulatory
standards at the compliance boundary in 6 years after the
system is placed into operation.
F. Long-term Effectiveness
Adequacy and reliability of controls
Implementation and maintenance of an effectiveness monitoring
program would be in place to evaluate variations in water quality
from expected conditions. Alternative measures can be taken to
address variations, if warranted. Potential risks to groundwater
users is further controlled by the connection of water supply users
to municipal water service within 0.5 miles of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users. An Operations & Maintenance plan will be
developed and implemented to operate the remedial system
within design parameters and document long-term maintenance.
Magnitude of Residual Risk
Implementation of a groundwater extraction and treatment
system will not result in increased residual risk, as the current
state and predicted future state does not indicate unacceptable
risk to human health or environment. Potential risks to
groundwater is further controlled by water filtration systems to
water supply users within a 0.5-mile radius of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users.
G. Reduction of Toxicity, Mobility, &Volume
Treatment process used and materials treated
Treatment of the affected groundwater would be performed
using the plant WWTP.
Volume of materials destroyed or treated
COIs would be removed from the groundwater, treated and
discharged under an NPDES permit in accordance with applicable
regulatory requirements.
Degree of expected reductions
COI concentration reductions are anticipated to meet regulatory
standards in a 6-year timeframe.
Irreversible Treatment
Mass removal would not be reversible for COIs. In -situ
treatment of COIs would not be reversible under stable
geochemical conditions.
Type and quantity of residuals remaining
Residuals may be present below regulatory standards as the
system would be intended to meet standards over time.
Residuals removed through groundwater treatment for COIs
would be managed in accordance with applicable regulatory
requirements.
02L Standards at the Compliance Boundary
The flow and transport model predicts that concentrations of
COIs would meet 02L standards at the compliance boundary in
approximately 6 years after implementation and ash basin
closure.
Page 8 of 9

M
a
Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction
with Clean Water
Infiltration and Treatment
Groundwater extraction would rely
on groundwater extraction to
remove groundwater COIs and to
reduce COI concentrations in
groundwater over time to meet
corrective action goals. Infiltration
wells would use clean water to
flush COIs from vadose zone soil
and dewatered soil. The
introduction of water to the
shallow and deep flow zones would
also enhance groundwater
extraction. This remedy would use
3 vertical groundwater extraction
wells, 1 horizontal groundwater
extraction well, 12 clean water
injection wells, and 6 acre
infiltration gallery. Extracted
groundwater would be pumped to
the Basement Basin WWTP where
it would be treated and discharged
through the existing NPDES
system.
APPENDIX M, TABLE 1
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 1
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Costs to Implement Remedial Alternative 3
The estimated costs to implement this Remediation
Alternative have not been developed.
Life cycle costs are determined using a Net Present Value
(NPV) of expenditures for initial Capital costs and annual O&M
expenses for the duration of the remedy. A Discount Rate of
5% assumed in developing the cost estimate.
Costs would also include the needed labor and materials to
implement the Alternative and, as necessary, routine labor
annual and 5-year reporting.
Stakeholder Sentiment Regarding
Implementation
It is expected that there will be positive and negative
sentiment about implementation of an active groundwater
remedy that includes extraction and treatment. No landowner
is anticipated to be affected and groundwater COIs do not
pose an unacceptable risk to potential human or ecological
receptors. The remaining affected property is owned by Duke
Energy, which is anticipated to implement institutional
controls.
It is anticipated that the treated groundwater would be
discharged through a NPDES permitted outfall that flows to
Hyco Reservoir and the discharge would be treated as
necessary to meet permit limits.
An expanded groundwater extraction system and clean water
infiltration system that addresses the COI plume north of the
GSA/DFA silo and operational areas may improve public
perception. It is anticipated that groundwater extraction and
treatment would generally receive more positive community
acceptance than MNA since it involves more active measures
to extraction and reduce COI mass from groundwater. This
alternative would likely be percieved as more robust than
MNA in addressing groundwater impacts even if human
health and ecological risks are essentially the same between
the alternatives.
Until the final Site remedy is developed and comments are
received and reviewed, assessment of community acceptance
will not be fully known.
Ability to Augment the Remedy, if Needed
Groundwater extraction and infiltration using conventional
well technology are adaptable processes. Use of a
infiltration gallery is less ammenable to modification. The
infiltration may preclude supplemental remediation efforts.
While it is not expected, treatment of the groundwater
discharge can be modified to address changes in COI
concentrations or permit limits.
Environmental Footprint of the Remedy
Sustainability analysis was conducted to quantify the
environmental footprint of each remedial alternative based on
energy use and associated emissions, during the construction
phase, active remediation, and groundwater monitoring
activities.
The environmental footprint of Alternative 3 is the most
energy -intensive of the remedial alternatives being
considered. Alternative 1 (MNA) requires significantly less
materials and energy than Alternative 2 and is therefore
characterized by a dramatically smaller environmental
footprint. Alternative 3 presents higher, but generally
comparable, environmental footprint metrics when measured
against Alternative 2. Alternative 3 utilizes an infiltration
gallery which produces more air emissions compared to
Alternative 2, generating a higher material -related
environmental footprint for the construction phase. The
analysis indicates operating the infiltration gallery to be more
energy -intensive in Alternative 3 than the recharge well
network Alternative 2.
The quantitative analysis of the environmental footprints of
the remedial alternatives under consideration for this CAP
indicates Alternative 3 to be the least sustainable option.
Page 9 of 9

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
APPENDIX M, TABLE 2
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 2
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users
to the municipal water supply within a half -mile of the ash
basin compliance boundaries.
Environment
The CSS Source Area 1 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix E).
B. Compliance with Applicable Regulations
Federal
MNA complies with USEPA CCR Rule specified in 40 Code
of Federal Regulations (CFR) § 257.
State
MNA will comply with Coal Ash Management Act of 2014
and 15A NCAC 02L .0106(I). If approved and subject to
notification requirements including the NC Department of
Transportation and NCDEQ for Sediment and Erosion
Control associated with monitoring well installation for
effectiveness monitoring. For additional details on MNA
see Appendix I.
Local
MNA would be subject to notification requirements to any
affected parties and to Rutherford County officials per
15A NCAC 02L .0114(b).
C. Technical & Logistical Feasibility
Ability to construct and operate technology
There are 18 monitoring wells already installed related to the
Unit 1-4 Ash Basin. Other than abandonment of selected wells
for basin closure and potential installation of additional
monitoring wells, no significant construction is required for
implementation.
Reliability of technology
MNA has been used successfully to achieve remedial objectives
for a wide range of COI and geologic settings. The CSM and
predictive modeling support reliability of the approach.
Ease of undertaking additional RAs if necessary
Other remedial technologies have commonly been used in
conjunction with MNA. Use of MNA will not adversely impact
the implementation of other potential remedial actions.
Ability to monitor effectiveness of remedy
Effectiveness is monitored through evaluation of COI
concentrations over time in accordance with a groundwater
effectiveness monitoring program.
Ability to coordinate and obtain approvals from
other agencies
MNA does not require interaction with other agencies to
implement.
Availability of services and materials
An extensive groundwater monitoring well network already
exists. Additional monitoring wells may be required to
complete the MNA well network. All services and materials are
readily available to support effectiveness monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
There are no requirements for bench scale testing to implement
MNA.
Design
MNA is readily implementable. The existing monitoring well
network can be utilized to design the MNA network.
Permitting
Soil Erosion and Sediment Control permits are required for any
land disturbance, including well installation activities. These
permits are a straightforward to procure.
Page 1 of 6

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
.a
APPENDIX M, TABLE 2
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 2
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
E. Short-term Effectiveness
Protection of Community
The surrounding community would not be affected during
implementation of MNA activities performed on Duke Energy
property. Any increase in traffic on roads leading to CSS due
to the nature of the work would be de minimis.
Worker Protection
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers
and the environment. All personal will be require relavent
training and supporting documentation to verify compentency.
Environmental Impacts
There would be some migration of COI affected groundwater
would be expected as part of the attenuation process.
However, human health and ecological risk assessments do
not indicate significant risks.
Time Until Action is Complete
Groundwater data indicates compliance to regulatory
standards at the compliance boundary is currently achieved.
F. Long-term Effectiveness
Adequacy and Reliability of Controls
Implementation and maintenance of an effectiveness monitoring
program will be in place to evaluate variations from expected
conditions. Alternative measures can be taken to address
variations. Potential risks to groundwater users is further
controlled by the installation of water filtration systems for water
supply well within a 0.5-mile radius of the ash basin compliance
boundaries. Implementation of institutional controls may
include a restricted designation to further protect potential
groundwater users.
Magnitude of Residual Risk
Implementation of MNA will not result in increased residual risk,
as the current state and predicted future state does not indicate
unacceptable risk to human health or environment. Potential
risks to groundwater is further controlled by connection of 70
water supply users to the municipal water supply within a 0.5-
mile radius of the ash basin compliance boundaries.
Implementation of institutional controls may include a restricted
designation to further protect potential groundwater users.
G. Reduction of Toxicity, Mobility, & Volume
Treatment Process Used and Materials Treated
None. Relies on natural attenuation processes and mechanisms
such as dispersion and dilution to reduce COI concentrations to
below 02L standards.
Volume of Materials Destroyed or Treated
None. COIs are inorganic and cannot be destroyed; however,
COIs will be removed from groundwater through geochemical
processes.
Degree of Expected Reductions
COI concentration currently meet regulatory standards.
Irreversible Treatment
None. Natural processes are not anticipated to be reversible
based on results of extensive geochemical modeling; however,
variations in pH and reduction -oxidation in the geochemical
environment can change effectiveness.
Type and Quantity of Residuals Remaining
None. The natural attenuation processes do not create
additional residuals for inorganic COIs.
H. Time Required to Achieve Remedial Goals
02L Standards at the Compliance Boundary
Concentrations of COIs currently meets 02L standards at the
compliance boundary.
Page 2 of 6

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
.a
APPENDIX M, TABLE 2
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 2
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
lCosts to Implement Remedial Alternative 1
The estimated costs to implement this Remediation
Alternative have not been developed.
Life cycle costs are determined using a Net Present Value
(NPV) of expenditures for initial Capital costs and annual
O&M expenses for the duration of the remedy. A Discount
Rate of 5% assumed in developing the cost estimate.
Costs would also include the needed labor and materials to
implement the Alternative and, as necessary, routine labor
for annual and 5-year reporting.
J. Community Acceptance
Stakeholder Sentiment Regarding
Implementation
It is expected that there will be positive and negative
sentiment about implementation of an MNA program. No
landowner is affected and groundwater COIs do not pose an
unacceptable risk to potential human or ecological receptors.
The remaining property is owned by Duke Energy, which is
anticipated to have institutional controls. However,
community stakeholders with concerns regarding the capital
and near -term 0&M costs associated with active remediation
may favor a less costly alternative.
Until the final corrective action is developed and comments
are received and reviewed, assessment of community
acceptance will not be fully informed
K. Adaptive Site Management
Ability to Augment the Remedy, if Needed
MNA is an adaptable process. Long-term groundwater
monitoring implemented as part of MNA and can be an
effective tool in identifying the need for alternative
approaches if unexpected changes in Site conditions
occur.
An MNA program would not hinder or preempt the use of
other remedial approaches in the future if conditions
change. In fact, an effectiveness monitoring program is
an essential part of any future remedial strategy. An MNA
effectiveness monitoring program would provide
information about changing Site conditions during and
after source control measures.
Environmental Footprint of the Remedy
The MNA remedy will impact the environment through
energy consumption and associated emissions associated
with installation of additional monitoring wells and sampling
and analysis of groundwater.
Some clearing of wooded areas would be required to install
monitoring wells and maintain access for sampling activities.
Maintenance of access will also require energy consumption.
Alternative 1 utilizes significantly fewer resources during
construction and throughout the remedial timeframe when
compared to the other remedial alternatives. Therefore,
Alternative 1 is the least energy -intensive of the remedial
alternatives being considered, providing reduced,
comparative environmental footprint metrics in overall
energy use.
Alternative 1 does not provide carbon capture through
photosynthetic activites of TreeWellsTm as Alternative 2 does.
Therefore, Alternative 1 is the least sustainabile option.
Page 3 of 6

Remediation Alternatives
Remediation Alternative 2
Phytoremediation and TreeWellrM
Technology
Phytoremedion and TreeWellTM
technology would reduce COI
concentrations to meet corrective
action goals by way of
groundwater extraction and COI
uptake by phytoremediation trees.
This remedy would use
approximately 285
phytoremediation trees and tree
wells north and northeast of the
former Units 1-4 ash basin.
Extracted water would either be
retained by the phytoremediation
tree or released into the
atmosphere via
evapotranspiration. COIs
metabolized by the
phytoremediation trees would be
retained within the tree.
N
Q
APPENDIX M, TABLE 2
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 2
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users
to the municipal water supply within a half -mile of the ash
basin compliance boundaries.
Remedial Alternative 2 will achieve a higher degree of
protection for human health and the environment when
compared to Remedial Alternative 1 (MNA).
Environment
The CSS Source Area 2 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix Q.
B. Compliance with Applicable Regulations
Federal
The groundwater extraction and treatment specified in
Remediation Alternative 2 would comply with USEPA CCR
Rule specified in 40 Code of Federal Regulations (CFR) §
257.
State
Alternative 2 complies with the Coal Ash Management
Act of 2014,15A NCAC 02L regulations and NCAC 02B
regulations. NPDES permitted discharge is in place. The
NPDES Permit may need to be modified to accommodate
the discharge of treated groundwater. Procurement of
Sediment and Erosion Control permits associated with
extraction, infiltration, and monitoring well installation is
a straight -forward process.
Local
Groundwater extraction, infiltration, and treatment can
be implemented in compliance with local laws and
regulations.
C. Technical & Logistical Feasibility
Ability to construct and operate technology
Technology to construct remedy is straightforward and
available. This would require specialized expertise. Duke
Energy has consulted with experts in the field about specific
application at the U1-4 AB.
Reliability of technology
This technology has been successfully implemented at similar
sites within the NC and SC piedmont.
Ease of undertaking additional RAs if necessary
The technology doesn't preclude implementation of other
remedial alternatives, if warranted.
Ability to monitor effectiveness of remedy
Effectiveness is monitored through tree growth and vitality as
well as periodic review of groundwater data. Revised predictive
modeling can be used to evaluate optimization opportunities.
Ability to coordinate and obtain approvals from
other agencies
Soil erosion and sediment control permits are straightforward
and readily obtained. Must verify that implementation would
not adversly imact endangered dwarf -flowered heartleaf. US
Army Corp of Engineers input may be required for portions of
remedy within the 100-year floodplain.
Availability of services and materials
All services and materials are readily available to support the
remediation alternative. An extensive groundwater monitoring
well network already exists to support effectiveness
monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
TreeWelITM technologies can be implemented following
development of a design for phytoremediation and TreeWellTM
technology. There are intervals of approximately 2 to 2.5
months in the spring and fall when planting of phytoremediation
trees is optimal.
Design
Detailed design activities would commence upon approval of the
CAP Update by NCDEQ.
Permitting
Soil erosion and sediment control permits are required for
installation of wells and other infrastructure that include ground
disturbance (e.g., conveyance piping).
Page 4 of 6

Remediation Alternatives
Remediation Alternative 2
Phytoremediation and TreeWeIITM
Technology
Phytoremedion and TreeWeIITM
technology would reduce COI
concentrations to meet corrective
action goals by way of
groundwater extraction and COI
uptake by phytoremediation trees.
This remedy would use
approximately 285
phytoremediation trees and tree
wells north and northeast of the
former Units 1-4 ash basin.
Extracted water would either be
retained by the phytoremediation
tree or released into the
atmosphere via
evapotranspiration. COIs
metabolized by the
phytoremediation trees would be
retained within the tree.
N
Q
APPENDIX M, TABLE 2
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 2
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
E. Short-term Effectiveness
Protection of Community during remediation
Community will not be impacted during active remediation
and monitoring activities as they would be performed on Duke
Energy property. Any anticipated increase in traffic on roads
leading to CSS due to nature of the work would be de
minimis .
Protection of workers during remediation
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers
and the environment. All personal will be require relavent
training and supporting documentation to verify compentency.
Environmental impacts
Remedial Alternative 2 has increased energy consumption to
construct the phytoremediation system. The TreeWeIITM
system actively removes carbon dioxide from the air, creating
a positive environmental impact. Additional environmental
impacts associated with TreeWells-rm are clearing to install
wells and supporting infrastructure would be minimal and
work would be performed with a soil erosion and sediment
control permit.
Time Until Action is Complete
Groundwater data indicates compliance to regulatory
standards at the compliance boundary is currently achieved.
The phytoremediation extraction will provide surface water
protection shortly following installation.
F. Long-term Effectiveness
Adequacy and reliability of controls
Implementation and maintenance of an effectiveness monitoring
program would be in place to evaluate variations in water quality
from expected conditions. Alternative measures can be taken to
address variations, if warranted. Potential risks to groundwater
users is further controlled by the connection of water supply
users to municipal water service within 0.5 miles of the ash
basin compliance boundaries. Implementation of institutional
controls may include a restricted designation to further protect
potential groundwater users. An Operations & Maintenance plan
will be developed and implemented to operate the remedial
system within design parameters and document long-term
maintenance.
Magnitude of Residual Risk
Implementation of phytoremediation technology and TreeWeIITM
technology will not result in increased residual risk. Current
state and predicted future state does not indicate unnacceptable
risk to human health or environment. Potential risk of human
exposure to groundwater controlled instituitional controls.
G. Reduction of Toxicity, Mobility, & Volume
Treatment process used and materials treated
Treatment will be through removal of COI mass by
phytoremediation tree uptake.
Volume of materials destroyed or treated
COI will neither be destroyed nor treated but transferred to
another waste stream and disposed in accordance with
applicable regulatory requirements.
Degree of expected reductions
COI concentration reductions are anticipated to meet regulatory
standards.
Irreversible Treatment
Mass removal would not be reversible for COIs. In -situ
treatment of COIs would not be reversible under stable
geochemical conditions.
Type and quantity of residuals remaining
COI residuals that are not removed through treatment will be
managed within the compliance boundary.
02L Standards at the Compliance Boundary
Concentrations of COIs currently meets 02L standards at the
compliance boundary. The phytoremedation system should
provide additional protections for the surface water beyond the
compliance boundary.
Page 5 of 6

Remediation Alternatives
Remediation Alternative 2
Phytoremediation and TreeWellTM
Technology
Phytoremedion and TreeWellTM
technology would reduce COI
concentrations to meet corrective
action goals by way of
groundwater extraction and COI
uptake by phytoremediation trees.
This remedy would use
approximately 285
phytoremediation trees and tree
wells north and northeast of the
former Units 1-4 ash basin.
Extracted water would either be
retained by the phytoremediation
tree or released into the
atmosphere via
evapotranspiration. COIs
metabolized by the
phytoremediation trees would be
retained within the tree.
N
Q
APPENDIX M, TABLE 2
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 2
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Costs to Implement Remedial Alternative 2
Capital Costs
$1,804,000.00
Annual O&M Costs
$127,000.00
Total Life Cycle Costs
$2,435,000.00
Costs are based on the labor and materials required for the
installation of 8 monitoring wells and 2.54 acres of
TreeWel IsTm.
Extracted water will be treated and discharged through the
existing NPDES system. Life cycle represents NPV of
expenditures with an assumed discount Rate of 5%.
Stakeholder Sentiment Regarding
Implementation
It is likely that community stakeholders are sufficiently
familiar with the concept of trees extracting water from the
ground. It is expected that the community stakeholders
would not have significant concerns pertaining to the
installation or operation of the phytoremediation system.
Similarly, mitigating transport of untreated groundwater to
the Broad River should be well received by some community
stakeholders.
A groundwater extraction system that addresses the COI
plume may improve public perception. This alternative would
likely be percieved as more robust than MNA in addressing
groundwater impacts even if human health and ecological
risks are essentially the same between MNA and
phytoremediation.
Until the final Site remedy is developed and comments are
received and reviewed, assessment of community
acceptance will not be fully known.
Ability to Augment the Remedy, if Needed
Phytoremediation and TreeWell'" technology is an
adaptable process. Alternative remedial alternatives can
be implemented if Phytoremediation and TreeWellTM
technology proves ineffective.
Environmental Footprint of the Remedy
Sustainability analysis was conducted to quantify the
environmental footprint of each remedial alternative based
on energy use and associated emissions, during the
construction phase, active remediation, and groundwater
monitoring activities.
The environmental footprint of Alternative 2 is the more
energy -intensive remedial alternative being considered.
Alternative 1 (MNA) requires less materials and energy than
Alternative 2 and is therefore characterized by a smaller
energy footprint. Alternative 2 presents lower air emissions
footprint metrics when measured against Alternative 1 as a
result of carbon capture by TreeWellsTM. The quantitative
analysis of the environmental footprints of the remedial
alternatives under consideration for this CAP indicates
Alternative 2 to be the more sustainable option.
Opportunities for system optimization and energy savings
could be pursued throughout the remediation timeframe, as
conditions change and component technologies possibly
evolve.
The quantitative analysis of the environmental footprints of
the remedial alternatives under consideration for this CAP
indicates Alternative 2 to be the most sustainable option.
Page 6 of 6

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users
to the municipal water supply within a half -mile of the ash
basin compliance boundaries.
Environment
The CSS Source Area 3 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix E).
B. Compliance with Applicable Regulations
Federal
MNA complies with USEPA CCR Rule specified in 40 Code
of Federal Regulations (CFR) § 257.
State
MNA will comply with Coal Ash Management Act of 2014
and 15A NCAC 02L .0106(I). If approved and subject to
notification requirements including the NC Department of
Transportation and NCDEQ for Sediment and Erosion
Control associated with monitoring well installation for
effectiveness monitoring. For additional details on MNA
see Appendix I.
Local
MNA would be subject to notification requirements to any
affected parties and to Rutherford County officials per
15A NCAC 02L .0114(b).
C. Technical & Logistical Feasibility
Ability to construct and operate technology
There are 32 monitoring wells already installed related to the
Unit 5 Ash Basin. Other than abandonment of selected wells for
basin closure and potential installation of additional monitoring
wells, no significant construction is required for
implementation.
Reliability of technology
MNA has been used successfully to achieve remedial objectives
for a wide range of COIs and geologic settings either as a stand
alone remedy, or in combination with other remediation
approaches. The CSM supports the reliability of an MNA
approach.
Ease of undertaking additional RAs if necessary
Other remedial technologies have commonly been used in
conjunction with MNA. Use of MNA will not adversely impact the
implementation of other potential remedial actions.
Ability to monitor effectiveness of remedy
Effectiveness is monitored through evaluation of COI
concentrations over time in accordance with a groundwater
effectiveness monitoring program.
Ability to coordinate and obtain approvals from
other agencies
MNA does not require interaction with other agencies to
implement.
Availability of services and materials
An extensive groundwater monitoring well network already
exists. Additional monitoring wells may be required to complete
the MNA well network. All services and materials are readily
available to support effectiveness monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
There are no requirements for bench scale testing to implement
MNA.
Design
MNA is readily implementable. The existing monitoring well
network can be utilized to design the MNA network.
Permitting
Soil Erosion and Sediment Control permits are required for any
land disturbance, including well installation activities. These
permits are a straightforward to procure.
Page 1 of 9

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
14
dispersion.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
E. Short-term Effectiveness
Protection of Community
The surrounding community would not be affected during
implementation of MNA activities performed on Duke Energy
property. Any increase in traffic on roads leading to CSS due
to the nature of the work would be de minimis.
Worker Protection
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers and
the environment. All personal will be require relavent training
and supporting documentation to verify compentency.
Environmental Impacts
There would be some migration of COI affected groundwater
would be expected as part of the attenuation process.
However, human health and ecological risk assessments do
not indicate significant risks.
Time Until Action is Complete
Predictive modeling has not been conducted in the area
northeast of the U5 AB because boron concentrations in this
area are less than the 02L standard. Similar simulations
conducted on conservative constituents other than boron
predict that they would naturally attenuate to less than the
groundwater comparison criteria.
F. Long-term Effectiveness
Adequacy and Reliability of Controls
Implementation and maintenance of an effectiveness monitoring
program will be in place to evaluate variations from expected
conditions. Alternative measures can be taken to address
variations. Potential risks to groundwater users is further
controlled by the installation of water filtration systems for water
supply well within a 0.5-mile radius of the ash basin compliance
boundaries. Implementation of institutional controls may include
a restricted designation to further protect potential groundwater
users.
Magnitude of Residual Risk
Implementation of MNA will not result in increased residual risk,
as the current state and predicted future state does not indicate
unacceptable risk to human health or environment. Potential
risks to groundwater is further controlled by connection of 70
water supply users to the municipal water supply within a 0.5-
mile radius of the ash basin compliance boundaries.
Implementation of institutional controls may include a restricted
designation to further protect potential groundwater users.
G. Reduction of Toxicity, Mobility, & Volume
Treatment Process Used and Materials Treated
None. Relies on natural attenuation processes and mechanisms
such as dispersion and dilution to reduce COI concentrations to
below 02L standards.
Volume of Materials Destroyed or Treated
None. COIs are inorganic and cannot be destroyed; however,
COIs will be removed from groundwater through geochemical
processes.
Degree of Expected Reductions
Simulations conducted on conservative constituents other than
boron predict that they would naturally attenuate to less than
the groundwater comparison criteria.
Irreversible Treatment
None. Natural processes are not anticipated to be reversible
based on results of extensive geochemical modeling; however,
variations in pH and reduction -oxidation in the geochemical
environment can change effectiveness.
Type and Quantity of Residuals Remaining
None. The natural attenuation processes do not create
additional residuals for inorganic COIs.
02L Standards at the Compliance Boundary
For the US AB, non -conservative constituents are the primary
issue at and beyond the 500-foot compliance boundary.
However, predictive modeling has not been conducted in the
area northeast of the U5 AB because boron concentrations in
this area are less than the 02L standard. Future predictive flow
and transport modeling would be calibrated on a different
conservative constituent (e.g., sulfate) and applied to this area.
Similar simulations conducted on conservative constituents
other than boron predict that they would naturally attenuate to
less than the groundwater comparison criteria.
Page 2 of 9

Remediation Alternatives
Remediation Alternative 1
Monitored Natural
Attenuation
Monitored Natural Attenuation
(MNA) relies on natural
attenuation mechanisms to
reduce COI concentrations over
time to meet corrective action
goals. For inorganics, these
processes include adsorption to
soil and bedrock surfaces,
precipitation, ion exchange,
phyto-attenuation, dilution and
dispersion.
Q
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Costs to Implement Remedial Alternative 1
The estimated costs to implement this Remediation
Alternative have not been developed.
Life cycle costs are determined using a Net Present Value
(NPV) of expenditures for initial Capital costs and annual
O&M expenses for the duration of the remedy. A Discount
Rate of 5% assumed in developing the cost estimate.
Costs would also include the needed labor and materials to
implement the Alternative and, as necessary, routine labor
for annual and 5-year reporting.
J. Community Acceptance
-
K. Adaptive Site Management
F_
Stakeholder Sentiment Regarding
Implementation
Ability to Augment the Remedy, if Needed
It is expected that there will be positive and negative
MNA is an adaptable process. Long-term groundwater
sentiment about implementation of an MNA program. No
monitoring implemented as part of MNA and can be an
landowner is affected and groundwater COIs do not pose an
effective tool in identifying the need for alternative
unacceptable risk to potential human or ecological receptors.
approaches if unexpected changes in Site conditions
occur.
The remaining property is owned by Duke Energy, which is
anticipated to have institutional controls. Some community
An MNA program would not hinder or preempt the use of
stakeholders might consider a long time frame to achieve
other remedial approaches in the future if conditions
remediation goals for boron to be unacceptable. However,
change. In fact, an effectiveness monitoring program is an
community stakeholders with concerns regarding the capital
essential part of any future remedial strategy. An MNA
and near -term O&M costs associated with active remediation
effectiveness monitoring program would provide
may favor a less costly alternative.
information about changing Site conditions during and
after source control measures.
Until the final corrective action is developed and comments
are received and reviewed, assessment of community
acceptance will not be fully informed.
Environmental Footprint of the Remedy
he MNA remedy will impact the environment through
nergy consumption and associated emissions associated
pith installation of additional monitoring wells and sampling
nd analysis of groundwater.
Some clearing of wooded areas would be required to install
monitoring wells and maintain access for sampling activities.
Maintenance of access will also require energy consumption.
Iternative 1 utilizes significantly fewer resources during
Dnstruction and throughout the remedial timeframe when
Dmpared to the other remedial alternatives. Therefore,
Iternative 1 is the least energy -intensive of the remedial
Iternatives being considered, providing reduced,
Dmparative environmental footprint metrics in overall
nergy use and across all air emission parameters.
Page 3 of 9

Remediation Alternatives
Remediation Alternative 2
pH Adjustment Gallery
A pH adjustment gallery would be
constructed using a conventional
back hoe. The dimensions and
design would be based on bench -
scale testing but would range from
6 to 10 ft. deep and 5 ft. wide.
The length of the pH adjustment
gallery trench would be
determined by the residence time
needed to neutralize water flowing
through the trench.
The bottom of the trench would be
native soil lined with
approximately 6 inches of
limestone. Subsequent materials
placed in the pH adjustment
gallery trench would not inhibit
infiltration of treated surface water
below the limestone bedding to
underlying groundwater.
^�
Treated effluent from the pH
0�
adjustment gallery trench would
gravity drain to a storm water
sewer line that directs storm water
to the Basement Basin, which
ultimately discharges through
NPDES Outfall 005 to the Broad
River.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users
to the municipal water supply within a half -mile of the ash
basin compliance boundaries.
Predictive flow and transport modeling indicate that the 02L
standard for boron could be achieved outside the compliance
boundary in approximately 6 years using active groundwater
remedial measures. Remedial Alternative 2 will achieve a
higher degree of protection for human health and the
environment in a much shorter time -frame when compared
to Remedial Alternative 1 (MNA).
Environment
The CSS Source Area 3 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix E).
B. Compliance with Applicable Regulations
Federal
The pH adjustment gallery specified in Remediation
Alternative 2 would comply with USEPA CCR Rule
specified in 40 Code of Federal Regulations (CFR) § 257.
State
Alternative 3 complies with the Coal Ash Management Act
of 2014,15A NCAC 02L regulations and NCAC 02B
regulations. NPDES permitted discharge is in place. The
NPDES Permit may need to be modified to accommodate
the discharge of treated groundwater. Procurement of
Sediment and Erosion Control permits associated with
installation is a straight -forward process.
Local
Groundwater treatment through pH adjustment gallery
can be implemented in compliance with local laws and
regulations.
C. Technical & Logistical Feasibility
Ability to construct and operate technology
Construction of pH adjustment trenches similar to proposed
Alternative 3 is common for the treatment of acid mine
drainage.
Reliability of technology
Performance of pH adjustment trenches similar to proposed
Alternative 3 has been demonstrated effective for treatment of
acid mine drainage.
Ease of undertaking additional RAs if necessary
The technology doesn't preclude implementation of other
remedial alternatives, if warranted. The reactive media can be
replaced with different, possibly more effective media.
Ability to monitor effectiveness of remedy
Multiple methods can be used to monitor system effectiveness.
An effectiveness monitoring plan would be implemented to
track changes in COI concentrations over time. Ongoing review
of data and periodic updates to the groundwater modeling
would be performed.
Ability to coordinate and obtain approvals from
other agencies
Soil erosion and sediment control permits are relatively
straightforward and can be obtained readily. The existing
NPDES permit would need to be modified to allow for the
discharge of treated groundwater from Outfall 005.
Availability of services and materials
All services and materials are readily available to support the
remediation alternative. An extensive groundwater monitoring
well network already exists to support effectiveness monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
Bench scale testing of reactive media using site surface water
and groundwater would be conducted to select and optimize
design of the reactive media.
Design
Detailed design activities would commence upon approval of the
CAP Update by NCDEQ. Full scale design is dependent on bench
testing, as required, to develop more accurate understanding of
groundwater treatment capabilities under the proposed design.
Permitting
Soil erosion and sediment control permits are required for
installation of wells and other infrastructure that include ground
disturbance (e.g., conveyance piping). The NPDES permit can be
modified if required for the discharge of treated groundwater.
Page 4 of 9

Remediation Alternatives
J!e-ediation
Alternative 2
pH Adjustment Gallery
A pH adjustment gallery would be
constructed using a conventional
back hoe. The dimensions and
design would be based on bench -
scale testing but would range from
6 to 10 ft. deep and 5 ft. wide.
The length of the pH adjustment
gallery trench would be
determined by the residence time
needed to neutralize water flowing
through the trench.
The bottom of the trench would be
native soil lined with
approximately 6 inches of
limestone. Subsequent materials
placed in the pH adjustment
gallery trench would not inhibit
infiltration of treated surface water
below the limestone bedding to
underlying groundwater.
N
Treated effluent from the pH
adjustment gallery trench would
gravity drain to a storm water
sewer line that directs storm water
to the Basement Basin, which
ultimately discharges through
NPDES Outfall 005 to the Broad
River.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
F_ E. Short-term Effectiveness
Protection of Community during remediation
Community will not be impacted during active remediation and
monitoring activities as they would be performed on Duke
Energy property. Any anticipated increase in traffic on roads
leading to CSS due to nature of the work would be de minimis.
Protection of workers during remediation
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers and
the environment. All personal will be require relavent training
and supporting documentation to verify compentency.
Environmental impacts M"
Once installed, a pH adjustment trench would result in low
energy consumption. A soil erosion and sediment control
permit would be prepared prior to construction of the pH
adjustment trench.
Time Until Action is Complete
An estimate of the time until remedial action is complete is not
known at this time. Predictive modeling has not been
conducted on U5 AB COIs beyond the compliance boundary.
F. Long-term Effectiveness
Adequacy and reliability of controls
Implementation and maintenance of an effectiveness monitoring
program would be in place to evaluate variations in water quality
from expected conditions. Alternative measures can be taken to
address variations, if warranted. Potential risks to groundwater
users is further controlled by the connection of water supply
users to municipal water service within 0.5 miles of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users. An Operations & Maintenance plan will be
developed and implemented to operate the remedial system
within design parameters and document long-term maintenance.
Magnitude of Residual Risk
Implementation of a groundwater extraction and treatment
system will not result in increased residual risk, as the current
state and predicted future state does not indicate unacceptable
risk to human health or environment. Potential risks to
groundwater is further controlled by water filtration systems to
water supply users within a 0.5-mile radius of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users.
G. Reduction of Toxicity, Mobility, & Volume
Treatment process used and materials treated
Neutralization of acidic surface water. Some neutralized surface
water would infiltrate into underlying groundwater resulting in
an overall reduction of some COI concs in groundwater.
Volume of materials destroyed or treated
COI will neither be destroyed nor treated but transferred to
another waste stream and disposed in accordance with
applicable regulatory requirements.
Degree of expected reductions
COI concentration reductions are anticipated to meet regulatory
standards.
Irreversible Treatment
Mass removal would not be reversible for COIs. In -situ
treatment of COIs would not be reversible under stable
geochemical conditions.
Type and quantity of residuals remaining
Residuals may be present below regulatory standards as the
system would be intended to meet standards over time.
Residuals removed through groundwater treatment for COIs
would be managed in accordance with applicable regulatory
requirements.
02L Standards at the Compliance Boundary
The flow and transport model predicts that concentrations of
COIs would meet 02L standards at the compliance boundary.
Page 5 of 9

Remediation Alternatives
Remediation Alternative 2
pH Adjustment Gallery '
A pH adjustment gallery would be
constructed using a conventional
back hoe. The dimensions and
design would be based on bench -
scale testing but would range from
6 to 10 ft. deep and 5 ft. wide.
The length of the pH adjustment
gallery trench would be
determined by the residence time
needed to neutralize water flowing
through the trench.
The bottom of the trench would be
native soil lined with
approximately 6 inches of
limestone. Subsequent materials
placed in the pH adjustment
gallery trench would not inhibit
infiltration of treated surface water
below the limestone bedding to
underlying groundwater.
N
Treated effluent from the pH
Wadjustment
gallery trench would
gravity drain to a storm water
sewer line that directs storm water
to the Basement Basin, which
ultimately discharges through
NPDES Outfall 005 to the Broad
River.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Costs to Implement Remedial Alternative 2
The estimated costs to implement this Re
Alternative have not been developed.
Life cycle costs are determined using a Net Present Value
(NPV) of expenditures for initial Capital costs and annual
O&M expenses for the duration of the remedy. A Discount
Rate of 5% assumed in developing the cost estimate.
Costs would also include the needed labor and materials to
implement the Alternative and, as necessary, routine labor
for annual and 5-year reporting.
Stakeholder Sentiment Regarding
Implementation
It is likely that some community stakeholders are sufficiently
familiar with the concept of neutralizing acidic water such
that they might not have significant concerns pertaining to
operation of the pH adjustment trench. Similarly, mitigating
transport of untreated groundwater to the Broad River should
be well received. Stakeholders might not be as familiar with
the indirect treatment of groundwater by way of infiltration.
Potential concerns of stakeholders would likely be alleviated
when they know that acidic groundwater would be
neutralized, there would be an overall improvement in
groundwater quality, and that the pH adjustment process
would not pose an unacceptable risks to human health or the
environment.
It is possible that some community stakeholders would have
concerns with potential exposure to surface water treated by
the pH adjustment gallery via NPDES permit. Assurances
that any means of wastewater disposal would be permitted
and monitored by NCDEQ should alleviate the concerns of
many stakeholders. Stakeholder concerns should be further
alleviated when they know that pH adjustment trench
effluent would undergo pretreatment and that constituent
concentrations in the discharged groundwater would be well
below permitted limits.
Until the final Site remedy is developed and comments are
received and reviewed, assessment of community acceptar
will not be fully known.
Ability to Augment the Remedy, if Needed
Groundwater Remedial Alternative 2 is readily amenable
to modifications if it is later determined that operational
changes could result is greater efficiencies or shorter
remediation timeframes. For example, if a more effective
reactive media is identified, it could replace a less
effective reactive neutralization media.
Groundwater Remedial Alternative 3 is readily amenable
to contingencies. For example, the pH adjustment trench
could be removed and Alternative 3 implemented in short
order if Alternative 2 is determined to be ineffective.
Environmental Footprint of the Remedy
Sustainability analysis was conducted to quantify the
environmental footprint of each remedial alternative based
on energy use and associated emissions, during the
construction phase, active remediation, and groundwater
monitoring activities.
The environmental footprint of Alternative 2 is the most
energy -intensive of the remedial alternatives being
considered. Alternative 1 (MNA) requires significantly less
materials and energy than Alternative 2 and is therefore
characterized by a dramatically smaller environmental
footprint. Alternative 2 presents higher, but generally
comparable, environmental footprint metrics when measured
against Alternative 3. Alternative 2 utilizes reactive media in
a pH adjustment gallery compared to Alternative 3, which
utilizes source control trench, this generates a higher
material -related environmental footprint. The analysis
indicates operating the pH adjustment gallery in Alternative
2 to be slightly more energy intensive, but generally similar,
to Alternative 3.
The quantitative analysis of the environmental footprints of
the remedial alternatives under consideration for this CAP
indicates Alternative 2 to be the least sustainable option.
Page 6 of 9

Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction and
Source Control
Alternative 3 involves groundwater
extraction within the low pH area
south of Unit 5 Cooling Tower A
and west of Cooling Tower B and
north of Cooling Tower A. A
groundwater extraction trench
would be constructed along a ditch
that carries acidic surface water
from the southern end of Cooling
Tower B to the west and then
north, parallel to and beyond
Cooling Tower B. Seven vertical
groundwater extraction wells
would be installed to the south of
Cooling Tower A and 5 vertical
groundwater extraction wells
would be installed to the north of
Cooling Tower A. The wells would
be installed to a depth
corresponding to the top of
bedrock. The primary purposes of
these vertical groundwater
extraction wells are to
hydraulically capture groundwater
beyond the 500 ft. compliance
boundary. Groundwater extracted
by the 12 vertical groundwater
extraction wells would be
discharged to the Basement Basin
by way of a storm water drain
located between Cooling Towers A
and B. Storm water and other
waste streams accumulate in the
Basement Basin before undergoing
treatment and being discharged to
the Broad River via NPDES Outfall
005.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
A. Human Health & Environment
Human Health
There is no measurable difference between evaluated Site
risk and risk indicated by background concentrations;
therefore, no material increase in risks to human health
related to the ash basins have been identified. The
assessment conservatively included potential recreational
receptors in the Broad River. Human receptors are not
affected by groundwater from the Site as water supply wells
are located upgradient or outside the drainage basin.
Additionally, Duke Energy connected 70 water supply users
to the municipal water supply within a half -mile of the ash
basin compliance boundaries.
Predictive flow and transport modeling indicate that the 02L
standard for boron could be achieved outside the compliance
boundary using active groundwater remedial measures.
Remedial Alternative 3 will achieve a higher degree of
protection for human health and the environment in a much
shorter time -frame when compared to Remedial Alternative 1
(MNA).
Environment
The CSS Source Area 3 does not cause an increase in risks to
ecological receptors (mallard duck, great blue heron,
muskrat, river otter, bald eagle, American robin, meadow
vole, red-tailed hawk, red fox and killdeer bird) evaluated for
the Broad River exposure area, based on the results of an
ecological risk assessment performed for the Site using
USEPA guideance (see Appendix Q.
B. Compliance with Applicable Regulations
Federal
The groundwater extraction, infiltration and in -situ
treatment specified in Remediation Alternative 3 would
comply with USEPA CCR Rule specified in 40 Code of
Federal Regulations (CFR) § 257.
State
Alternative 3 complies with the Coal Ash Management Act
of 2014,15A NCAC 02L regulations and NCAC 02B
regulations. NPDES permitted discharge is in place. The
NPDES Permit may need to be modified to accommodate
the discharge of treated groundwater. Procurement of
Sediment and Erosion Control permits associated with
extraction and monitoring well installation is a straight-
forward process.
Local
Groundwater extraction and infiltration can be
implemented in compliance with local laws and
regulations.
C. Technical & Logistical Feasibility
Ability to construct and operate technology
Technology to construct and operate Remediation Alternative 3
is straightforward and available. Technologies to treat
extracted groundwater exist but are less straight -forward to
operate.
Reliability of technology
Groundwater extraction is a mature technology and has been
used to implement cleanup on similar COIs. It is strongly
dependent on subsurface conditions and effectiveness of
treatment approaches.
Ease of undertaking additional RAs if necessary
The technology doesn't preclude implementation of other
remedial alternatives. Groundwater extraction wells can be
added to the proposed system or removed from service, as
warranted.
Ability to monitor effectiveness of remedy
Multiple methods can be used to monitor system effectiveness.
An effectiveness monitoring plan would be implemented to
track changes in COI concentrations over time. A system
Operations and Maintenance (O&M) plan would be implemented
to track the gallons of water extracted and infiltrated, the COI
mass removed on a cumulative basis. Ongoing review of data
and periodic updates to the groundwater modeling would be
performed.
Ability to coordinate and obtain approvals from
other agencies
Soil erosion and sediment control permits are relatively
straightforward and can be obtained readily. The existing
NPDES permit would need to be modified to allow for the
discharge of treated groundwater from Outfall 005.
Availability of services and materials
All services and materials are readily available to support the
remediation alternative. An extensive groundwater monitoring
well network already exists to support effectiveness monitoring.
D. Time Required to Initiate and Implement
Requirements for bench scale testing
Additional hydrogeologic testing, including pilot testing, may be
required to complete the design, to address heterogeneous
subsurface conditions, and confirm model predictions.
Collection of dynamic groundwater quality data from wells may
be required to confirm treatment options and design of any
treatment facilities if management of groundwater in the WWTP,
or discharge under the existing NPDES permit is not viable.
Design
Detailed design activities would commence upon approval of the
CAP Update by NCDEQ. Full scale design is dependent on
hydrogeologic testing and bench testing, as required, to develop
more accurate flow rates and estimates of extracted
groundwater quality. Final locations of extraction points,
conveyance piping, electrical service, tankage and potential
treatment units would be confirmed. Detailed design of
electrical, mechanical and controls components would then be
finalized for bidding and construction.
Permitting
Soil erosion and sediment control permits are required for
installation of wells and other infrastructure that include ground
disturbance (e.g., conveyance piping). The NPDES permit can be
modified if required for the discharge of treated groundwater.
Page 7 of 9

M
9
Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction and
Source Control
Alternative 3 involves groundwater
extraction within the low pH area
south of Unit 5 Cooling Tower A
and west of Cooling Tower B and
north of Cooling Tower A. A
groundwater extraction trench
would be constructed along a ditch
that carries acidic surface water
from the southern end of Cooling
Tower B to the west and then
north, parallel to and beyond
Cooling Tower B. Seven vertical
groundwater extraction wells
would be installed to the south of
Cooling Tower A and 5 vertical
groundwater extraction wells
would be installed to the north of
Cooling Tower A. The wells would
be installed to a depth
corresponding to the top of
bedrock. The primary purposes of
these vertical groundwater
extraction wells are to
hydraulically capture groundwater
beyond the 500 ft. compliance
boundary. Groundwater extracted
by the 12 vertical groundwater
extraction wells would be
discharged to the Basement Basin
by way of a storm water drain
located between Cooling Towers A
and B. Storm water and other
waste streams accumulate in the
Basement Basin before undergoing
treatment and being discharged to
the Broad River via NPDES Outfall
005.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
E. Short-term Effectiveness
Protection of Community during remediation
Community will not be impacted during active remediation and
monitoring activities as they would be performed on Duke
Energy property. Any anticipated increase in traffic on roads
leading to CSS due to nature of the work would be de minimis.
Protection of workers during remediation
Work would be performed under a Health & Safety Plan, which
identifies risks and mitigation measures to protect workers and
the environment. All personal will be require relavent training
and supporting documentation to verify compentency.
Environmental impacts
Remedial Alternative 3 has increased energy consumption to
operate the extraction, infiltration, and treatment system and
will require additional energy for construction to manufacture
piping, well materials, and to excavate trenches for piping and
utilities. Environmental impacts associated with clearing to
install wells and supporting infrastructure would be significant
and work would be performed with a soil erosion and sediment
control permit.
Time until RA objectives are achieved
An estimate of the time until remedial action is complete is not
known at this time. Predictive modeling has not been
conducted on U5 AB COIs beyond the compliance boundary.
F. Long-term Effectiveness
Adequacy and reliability of controls
Implementation and maintenance of an effectiveness monitoring
program would be in place to evaluate variations in water quality
from expected conditions. Alternative measures can be taken to
address variations, if warranted. Potential risks to groundwater
users is further controlled by the connection of water supply
users to municipal water service within 0.5 miles of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users. An Operations & Maintenance plan will be
developed and implemented to operate the remedial system
within design parameters and document long-term maintenance.
Magnitude of Residual Risk
Implementation of a groundwater extraction and treatment
system will not result in increased residual risk, as the current
state and predicted future state does not indicate unacceptable
risk to human health or environment. Potential risks to
groundwater is further controlled by water filtration systems to
water supply users within a 0.5-mile radius of the ash basin
compliance boundaries. Implementation of institutional controls
may include a restricted designation to further protect potential
groundwater users.
G. Reduction of Toxicity, Mobility, & Volume
Treatment process used and materials treated
Treatment of the affected groundwater would be performed
using the plant WWTP.
Volume of materials destroyed or treated
COIs would be removed from the groundwater, treated and
discharged under an NPDES permit in accordance with
applicable regulatory requirements.
Degree of expected reductions
COI concentration reductions are anticipated to meet regulatory
standards in a 6-year timeframe.
Irreversible Treatment
Mass removal would not be reversible for COIs. In -situ
treatment of COIs would not be reversible under stable
geochemical conditions.
Type and quantity of residuals remaining
Residuals may be present below regulatory standards as the
system would be intended to meet standards over time.
Residuals removed through groundwater treatment for COIs
would be managed in accordance with applicable regulatory
requirements.
02L Standards at the Compliance Boundary
The flow and transport model predicts that concentrations of
COIs would meet 02L standards at the compliance boundary.
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Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction and
Source Control
Alternative 3 involves groundwater
extraction within the low pH area
south of Unit 5 Cooling Tower A
and west of Cooling Tower B and
north of Cooling Tower A. A
groundwater extraction trench
would be constructed along a ditch
that carries acidic surface water
from the southern end of Cooling
Tower B to the west and then
north, parallel to and beyond
Cooling Tower B. Seven vertical
groundwater extraction wells
would be installed to the south of
Cooling Tower A and 5 vertical
groundwater extraction wells
would be installed to the north of
Cooling Tower A. The wells would
be installed to a depth
corresponding to the top of
bedrock. The primary purposes of
these vertical groundwater
extraction wells are to
hydraulically capture groundwater
beyond the 500 ft. compliance
boundary. Groundwater extracted
by the 12 vertical groundwater
extraction wells would be
discharged to the Basement Basin
by way of a storm water drain
located between Cooling Towers A
and B. Storm water and other
waste streams accumulate in the
Basement Basin before undergoing
treatment and being discharged to
the Broad River via NPDES Outfall
005.
APPENDIX M, TABLE 3
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
CLIFFSIDE STEAM STATION - SOURCE AREA 3
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Costs to Implement Remedial Alternative 3
Capital Costs
$1,712,000.00
Annual O&M Costs
$243,000.00
Total Life Cycle Costs
$2,864,000.00
Costs are based on the labor and materials required for the
installation of 8 monitoring wells, 12 groundwater extraction
wells and a source control trench.
Extracted water will be treated and discharged through the
existing NPDES system. Life cycle represents NPV of
expenditures with an assumed discount Rate of 5%.
Stakeholder Sentiment Regarding
Implementation
It is likely that community stakeholders are sufficiently
familiar with the concept of groundwater extraction that they
would not have significant concerns pertaining to the
installation or operation of the groundwater extraction
system. Similarly, mitigating transport of untreated
groundwater to the Broad River should be well received by
some community stakeholders.
It is possible that some community stakeholders would have
concerns with potential exposure to discharged groundwater
via NPDES permit. Assurances that any means of
groundwater disposal would be permitted and monitored by
NCDEQ should alleviate stakeholder concerns. Stakeholder
concerns should be further alleviated when they know that
extracted groundwater might undergo treatment and that
constituent concentrations in the discharged groundwater
would be within permitted limits.
Until the final Site remedy is developed and comments are
received and reviewed, assessment of community acceptar
will not be fully known.
Ability to Augment the Remedy, if Needed
Groundwater extraction using conventional well
technology and interception trench is an adaptable
process. It can be easily modified to address changes to
COI plume configuration or COI concentrations based on
actual field data. Individual well pumping rates can be
adjusted or eliminated, or additional wells can be installed
to address COI plume changes.
While it is not expected, treatment of the groundwater
discharge can be modified to address changes in COI
concentrations or permit limits.
Environmental Footprint of the Remedy
Sustainability analysis was conducted to quantify the
environmental footprint of each remedial alternative based
on energy use and associated emissions, during the
construction phase, active remediation, and groundwater
monitoring activities.
The environmental footprint of Alternative 3 is the second -
most, energy -intensive remedial alternative being
considered. Alternative 1 (MNA) requires significantly less
materials and energy than Alternative 3 and is therefore
characterized by a dramatically smaller environmental
footprint. Alternative 3 presents lower, but generally
comparable, environmental footprint metrics when measured
against Alternative 2. Alternative 3 utilizes a source control
trench compared to a pH adjustment gallery as used in
Alternative 3. This generates a lower material -related
environmental footprint for the due to the lack of reactive
media required for pH adjustment. Instead, the water is
collected and conveyed for treatment. The quantitative
analysis of the environmental footprints of the remedial
alternatives under consideration for this CAP indicates
Alternative 3 to be the second -most sustainable option,
although not significantly less impactful than Alternative 2.
Opportunities for system optimization and energy savings
could be pursued throughout the remediation timeframe, as
conditions change and component technologies possibly
The quantitative analysis of the environmental footprints of
the remedial alternatives under consideration for this CAP
indicates Alternative 3 to be the second most sustainable
Page 9 of 9