NC0001422_Appdx O - Remediation Alternatives Summary_20200814

Corrective Action Plan Update August 2020
L.V. Sutton Energy Complex
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY
SynTerra

Remedial Alternatives
Remedial Alternative 1
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
and Confirmation Monitoring
14
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Remedial Alternative 1 relies on source excavation, continued
a'
groundwater extraction and treatment, and confirmation monitoring to
reduce COI concentrations over time to meet corrective action goals.
Confirmation monitoring measures the effects of 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.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
A. Protection of Human Health and the 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 and FPA have been identified. The assessment conservatively
included potential recreational receptors in the Site's NPDES cooling pond (Lake Sutton) and the Cape Fear River. Human
receptors are not affected by groundwater from the Site as water supply wells are located upgradient or beyond the hydrological
divide. Furthermore, within approximately 0.5 mile of the ash basins compliance boundary, 4 businesses were fitted with water
treatment systems, 4 business were connected to county water supply, 1 additional business is planned to be connected to
county water supply, and two public water supply wells were abandoned.
The site is an operating gas fired, combined cycle electric power plant and will be in industrial use for the foreseeable future.
Environment
There were no detected concentrations of COIs in the Sutton Cooling Pond that exceeded 02B standards. The 1971 and 1984 ash
basins and FPA do not cause an increase in risks to ecological receptors evaluated for the exposure area, based on the results of
an ecological risk assessment performed for the Site using USEPA guidance (see Appendix E).
B. Compliance with Applicable Federal, State, and Local Regulations
Federal
Remedial Alternative 1 complies with USEPA CCR Rule specified in 40 Code of Federal Regulations (CFR) § 257.
State
Remedial Alternative 1 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.
Local
N/A
Prepared by: GTC Checked by: JEC & WJW
Page 1 of 10

Remedial Alternatives
Remedial Alternative 1
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
and Confirmation Monitoring
14
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la
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Q
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E
Remedial Alternative 1 relies on source excavation, continued
a'
groundwater extraction and treatment, and confirmation monitoring to
reduce COI concentrations over time to meet corrective action goals.
Confirmation monitoring measures the effects of 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.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
C. Technical & Logistical Feasibility
Ability to construct and operate technology
There are 244 monitoring wells already installed related to the ash basins and FPA. No significant construction would be required for
implementation. Other than potential installation of additional monitoring wells, no significant construction is required for
implementation.
Reliability of technology
The technologies used in Remedial Alternative 1 have 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 the excavation, continued extraction, and confirmation monitoring approach.
Ease of undertaking additional Remedial Alternatives, if necessary
Other remedial technologies have commonly been used in conjunction with continued monitoring. Use of continued monitoring
would not adversely impact the implementation of other potential remedial actions; in fact, RA 2 1 contain all elements of Remedial
Alternative 1.
Ability to monitor effectiveness of remedy
Effectiveness is monitored through evaluation of COI concentrations over time in accordance with a post -excavation groundwater
effectiveness monitoring program.
Ability to coordinate and obtain approvals from other agencies
An NPDES permit exists for the facility and currently includes provisions for ongoing groundwater extraction.
Availability of services and materials
An extensive groundwater monitoring well network already exists. Additional monitoring wells may be required to complete the
continued monitoring 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 Remedial Alternative 1.
Design
The alternative is readily implementable. The existing monitoring well network can be utilized to design the continued monitoring
network.
Permitting
The facility expects an NPDES permit to be issued that will allow them to manage and discharge the water from the interim
extraction system contained. The NPDES permit could be modified, if necessary.
Soil Erosion and Sediment Control permits are required for land disturbance activities, including well installation. These permits are
a straightforward to procure.
Prepared by: GTc Checked by: JEC & wJW
Page 2 of 10

Remedial Alternatives
Remedial Alternative 1
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
and Confirmation Monitoring
14
d
la
c
L
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r
Q
m
M
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E
Remedial Alternative 1 relies on source excavation, continued
a'
groundwater extraction and treatment, and confirmation monitoring to
reduce COI concentrations over time to meet corrective action goals.
Confirmation monitoring measures the effects of 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.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
E. Short-term Effectiveness
IL
Protection of Community
The community would not be impacted during monitoring activities as they would be performed on Duke Energy property. Any
anticipated increase in traffic on roads leading to Sutton due to nature of the work would be de Minimis. Implementation and
maintenance of an effectiveness monitoring program would be in place to evaluate variations from expected conditions.
Alternative measures could be taken to address variations.
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 would be require relevant training and supporting documentation to verify competency.
Environmental Impacts
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 indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500 years.
This is likely due to conservative assumptions in the models. At the time of CAP Update preparation, only three quarters of post -
excavation data were available (September & December 2019, March 2020). No post -excavation data related to the FPA is
available. There is insufficient post -excavation data available to accurately predict natural attenuation. After the five year
monitoring period, the models can be refined to accurately predict the time required.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow
zone, there is a notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III) and
potentially the precipitation of ferrihydrite, which would provide additional sorption sites for COI attenuation. It appears the
system is naturally approaching elevated EH values. Though not confirmed, the increased EH might be due to the large flux of
infiltrating rainwater after excavation. These observations can be confirmed with the proposed five-year post -excavation EMP.
F. Long-term Effectiveness
Adequacy and Reliability of Controls
Implementation and maintenance of an effectiveness monitoring program would be in place to evaluate variations from expected
conditions. Alternative measures could be taken to address variations. Potential risks to groundwater users is further mitigated by
the connection of 5 businesses to New Hanover County water supply, installation of water filtration systems for water supply wells for
4 businesses, and abandonment of two public water supply wells within a 0.5-mile radius of the ash basin compliance boundaries.
Magnitude of Residual Risk
Implementation of Remedial Alternative 1 would not result in increased residual risk, as the current state and predicted future state
does not indicate unacceptable risk to human health or the 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.
Prepared by: GTc Checked by: JEC & WJW
Page 3 of 10

Remedial Alternatives
Remedial Alternative 1
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
and Confirmation Monitoring
14
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m
c
L
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r
Q
m
M
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E
Remedial Alternative 1 relies on source excavation, continued
a'
groundwater extraction and treatment, and confirmation monitoring to
reduce COI concentrations over time to meet corrective action goals.
Confirmation monitoring measures the effects of 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.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
G. Reduction of Toxicity, Mobility, &Volume
Treatment Process Used and Materials Treated
Treatment technologies used in Remedial Alternative 1 are source control and ongoing groundwater extraction on the eastern property
boundary. Natural attenuation relies on the mechanisms that naturally attenuate the concentrations of CCR inorganic constituents are
dilution, dispersion, advection, sorption (including ion exchange and precipitation) and phyto-attenuation
Volume of Materials Destroyed or Treated
The source of COIs to the groundwater has been removed through excavation. The extraction of groundwater at the eastern boundary
has removed COIs from groundwater. Extracted groundwater will be discharged under an NPDES permit in accordance with applicable
regulatory requirements.
Degree of Expected Reductions
There is insufficient post -excavation data following source removal to assess the time for the groundwater to achieve standards by
natural attenuation. After the five year effectiveness monitoring period, the model may be refined to accurately predict the time
required.
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
Residuals might be present below regulatory standards when standards are met over time, as intended. Residuals removed through
groundwater extraction and source removal have been and will be managed in accordance with applicable regulatory requirements.
02L Standards at the Compliance Boundary
Predictive modeling indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500
years. This is likely due to conservative assumptions in the models. A robust pump -and -treat system was simulated in the Flow
and Transport model (Appendix F). Results of those simulations indicate groundwater extraction and infiltration would not
decrease COI concentrations at the compliance boundary faster than what the MNA simulations predict. In fact, the pump -and -
treat simulation for selenium indicated concentrations would decrease to less than the 02L standard quicker under natural
attenuation. These results are due to the limited post -excavation dataset and the lack of monitoring wells downgradient of the
compliance boundary. Insufficient land surface is available to install wells beyond the compliance boundary. The models used
conservative assumptions to predict COI concentrations in groundwater beneath the cooling pond. At the time of the CAP Update
preparation, only three quarters of post excavation data were available (September & December 2019, March 2020). No post -
excavation data related to the FPA is available. There is insufficient post -excavation data available to accurately predict future
COI concentrations in groundwater beyond the compliance boundary. After the five year monitoring period, the models can be
refined to accurately predict the time required to reach compliance with regulatory standards. The groundwater system is
beginning to reach equilibrium. The geochemical and MNA evaluations identified multiple areas where natural attenuation has
already occurred. Recent groundwater sampling results indicate source removal is already providing the chemical environment
necessary for attenuation.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow
zone, there is a notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III)
and potentially the precipitation of ferrihydrite, which would provide additional sorption sites for COI attenuation. It appears the
system is naturally approaching the elevated EH values. Though not confirmed, the increased EH might be due to the large flux
of infiltrating rainwater after excavation. These observations can be confirmed with the proposed five-year post -excavation EMP.
Natural attenuation is occurring in the areas northwest of the 1984 ash basin, southeast of the 1971 ash basin and FPA, off -Site
near SMW-01C, and downgradient of the FADA within the FCPA. Boron and arsenic concentrations in wells on the west side of
the ash basins are also showing decreasing trends in some areas. COI concentrations are anticipated to naturally attenuate with
time as the groundwater system reaches equilibrium after excavation.
Prepared by: GTC Checked by: JEC & WJW
Page 4 of 10

Remedial Alternatives
Remedial Alternative 1
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
and Confirmation Monitoring
14
d
C
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L
d
r
Q
m
M
d
E
d
Remedial Alternative 1 relies on source excavation, continued
a'
groundwater extraction and treatment, and confirmation monitoring to
reduce COI concentrations over time to meet corrective action goals.
Confirmation monitoring measures the effects of 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.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Costs to Implement Remedial Alternative 1
Capital Costs
Not developed
Annual Costs
Not developed
Total Life Cycle Costs
Not developed
The cost estimate was not developed to reflect the cost of implementing Remedial Alternative 1 for Source Areas 1 and 2. Costs to
implement Remedial Alternative 1 include the labor and materials to monitor and maintain appropriate wells and continue operation of
the extraction system. This alternative does not include the costs of confirmation monitoring and would be less than the cost estimate
of RA2.
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.
Stakeholder Sentiment Regarding Implementation
It is expected that there would be positive and negative sentiment about implementation of an alternative that enlists an MNA
program. No landowner would be affected and groundwater COIs do not pose an unacceptable risk to potential human or
ecological receptors.
The property is owned and controlled by Duke Energy. The site is an operating gas fired, combined cycle electric power plant and
will be in industrial use for the foreseeable future. Some community stakeholders might consider the time frame to achieve
remediation goals to be unacceptable.
Until the final corrective action is developed and comments are received and reviewed, assessment of community acceptance
will not be fully informed.
Prepared by: GTC Checked by: JEC & WJW
Page 5 of 10

Remedial Alternatives
Remedial Alternative 2
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
Confirmation Monitoring with a Restricted Groundwater
Use Designation over a small portion of the Site's cooling
pond, and 5 year EMP review
N
d
M
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L
Y
Q
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E
d
Remedial Alternative 2 relies on, source excavation, continued
groundwater extraction and treatment, and confirmation monitoring. In
addition to these methods for reducing COI concentrations in
groundwater, institutional controls would also be used to prevent
receptor exposure. The institutional control of a Restricted Groundwater
Use Designation over a small portion of the Site's cooling pond would
further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
A. Protection of Human Health and the 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 and FPA have been identified. The assessment conservatively
included potential recreational receptors in the Site's NPDES cooling pond (Lake Sutton) and the Cape Fear River. Human
receptors are not affected by groundwater from the Site as water supply wells are located upgradient or beyond the hydrological
divide. Furthermore, within approximately 0.5 mile of the ash basins compliance boundary, 4 businesses were fitted with water
treatment systems, 4 business were connected to county water supply, 1 additional business is planned to be connected to
county water supply, and two public water supply wells were abandoned.
A restricted groundwater use designation is an institutional control that would further protect human health. The site is an
operating gas fired, combined cycle electric power plant and will be in industrial use for the foreseeable future.
If implemented after the five year review period, the contingency plan proposed in Section 5.13 would further protect human
health.
Environment
There were no detected concentrations of COIs in the Sutton Cooling Pond that exceeded 02B standards. The 1971 and 1984 ash
basins and FPA do not cause an increase in risks to ecological receptors evaluated for the exposure area, based on the results of
an ecological risk assessment performed for the Site using USEPA guidance (see Appendix E).
B. Compliance with Applicable Federal, State, and Local Regulations
Federal
Remedial Alternative 3 complies with USEPA CCR Rule specified in 40 Code of Federal Regulations (CFR) § 257.
State
Remedial Alternative 2 complies 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.
Local
A Restricted Groundwater Use Designation can be implemented in compliance with local laws and regulations.
Prepared by: GTC Checked by: JEC & WJW
Page 6 of 10

Remedial Alternatives
Remedial Alternative 2
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
Confirmation Monitoring with a Restricted Groundwater
Use Designation over a small portion of the Site's cooling
pond, and 5 year EMP review
N
d
m
M
c
L
Y
Q
m
M
d
E
d
Remedial Alternative 2 relies on, source excavation, continued
groundwater extraction and treatment, and confirmation monitoring. In
addition to these methods for reducing COI concentrations in
groundwater, institutional controls would also be used to prevent
receptor exposure. The institutional control of a Restricted Groundwater
Use Designation over a small portion of the Site's cooling pond would
further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
C. Technical & Logistical Feasibility
Ability to construct and operate technology
There are 244 monitoring wells already installed related to the ash basins and FPA. No significant construction would be required for
implementation. Additional monitoring wells may be required for post -excavation monitoring.
Reliability of technology
The technologies used in Remedial Alternative 2 have 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 the excavation, continued extraction, and confirmation monitoring approach. Additional assurances to the reliability
of the alternative are made through an effectiveness monitoring plan and a restricted groundwater use designation.
Ease of undertaking additional RAs if necessary
Remedial Alternative 2 relies on mature technology and have been used to implement cleanup strategies for similar COIs. These
technologies are dependent on subsurface conditions and effectiveness of treatment approaches. If a contingency option is deemed
necessary, applicable remedial technologies would be screened to determine the most effective technology is available.
Ability to monitor effectiveness of remedy
Effectiveness is monitored through evaluation of COI concentrations over time in accordance with a post -excavation groundwater
effectiveness monitoring program.
Ability to coordinate and obtain approvals from other agencies
Soil erosion and sediment control permits are relatively straightforward and could be readily obtained from NCDEQ. An NPDES
permit exists for the facility and currently includes provisions for ongoing groundwater extraction at the eastern property boundary.
A Restricted Groundwater Use Designation could be implemented in compliance with local laws and regulations.
Availability of services and materials
All services and materials are readily available to support the Remedial 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
There are no requirements for bench scale testing to implement Remedial Alternative 1.
Design
The alternative is readily implementable. The existing monitoring well network can be utilized to design the continued monitoring
network.
Permitting
The facility expects an NPDES permit to be issued that will allow them to manage and discharge the water from the interim
extraction system contained. The NPDES permit could be modified, if necessary.
Soil Erosion and Sediment Control permits are required for land disturbance activities, including well installation. These permits are
a straightforward to procure.
Prepared by: GTc Checked by: JEC & wJW
Page 7 of 10

Remedial Alternatives
Remedial Alternative 2
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
Confirmation Monitoring with a Restricted Groundwater
Use Designation over a small portion of the Site's cooling
pond, and 5 year EMP review
N
d
M
m
c
L
Q
m
M
d
E
d
Remedial Alternative 2 relies on, source excavation, continued
groundwater extraction and treatment, and confirmation monitoring. In
addition to these methods for reducing COI concentrations in
groundwater, institutional controls would also be used to prevent
receptor exposure. The institutional control of a Restricted Groundwater
Use Designation over a small portion of the Site's cooling pond would
further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
E. Short-term Effectiveness
in
Protection of Community during remediation
The community would not be impacted during monitoring activities as they would be performed on Duke Energy property. Any
anticipated increase in traffic on roads leading to Sutton due to nature of the work would be de Minimis. Implementation and
maintenance of an effectiveness monitoring program would be in place to evaluate variations from expected conditions.
Alternative measures could be taken to address variations. Potential risks to groundwater users could be further controlled by a
Restricted Groundwater Use Designation over a small portion of the Site's cooling pond.
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 would be require relevant training and supporting documentation to verify competency.
Environmental impacts
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.
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 Remedial Alternative objectives are achieved
Predictive modeling indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500 years.
This is likely due to conservative assumptions in the models. At the time of CAP Update preparation, only three quarters of post -
excavation data were available (September & December 2019, March 2020). No post -excavation data related to the FPA is
available. There is insufficient post -excavation data available to accurately predict natural attenuation. After the five year
monitoring period, the models can be refined to accurately predict the time required.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow
zone, there is a notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III) and
potentially the precipitation of ferrihydrite, which would provide additional sorption sites for COI attenuation. It appears the
system is naturally approaching the elevated EH values. Though not confirmed, the increased EH might be due to the large flux of
infiltrating rainwater after excavation. These observations can be confirmed with the proposed five-year post -excavation EMP.
F. Long-term Effectiveness
Adequacy and reliability of controls
Implementation and maintenance of an effectiveness monitoring program would be in place to evaluate variations from expected
conditions. Alternative measures could be taken to address variations. Potential risks to groundwater users is further mitigated by
the connection of 5 businesses to New Hanover County water supply, installation of water filtration systems for water supply wells for
4 businesses, and abandonment of two public water supply wells within a 0.5-mile radius of the ash basin compliance boundaries.
Implementation of institutional controls may include a restricted groundwater use designation to further protect potential groundwater
users.
Magnitude of Residual Risk
Implementation of Remedial Alternative 2 would 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 an
institutional control of a Restricted Groundwater Use Designation would further protect potential groundwater users.
Prepared by: GTC Checked by: JEC & WJW
Page 8 of 10

Remedial Alternatives
Remedial Alternative 2
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
Confirmation Monitoring with a Restricted Groundwater
Use Designation over a small portion of the Site's cooling
pond, and 5 year EMP review
N
d
M
m
c
d
Q
m
M
d
E
d
Remedial Alternative 2 relies on, source excavation, continued
groundwater extraction and treatment, and confirmation monitoring. In
addition to these methods for reducing COI concentrations in
groundwater, institutional controls would also be used to prevent
receptor exposure. The institutional control of a Restricted Groundwater
Use Designation over a small portion of the Site's cooling pond would
further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
G. Reduction of Toxicity, Mobility, &Volume
Treatment process used and materials treated
Treatment technologies used in Remedial Alternative 2 are source control and ongoing groundwater extraction and treatment. The
mechanisms that naturally attenuate the concentrations of CCR inorganic constituents are dilution, dispersion, advection, sorption
(including ion exchange and precipitation) and phyto-attenuation.
Volume of materials destroyed or treated
The source of COIs to the groundwater has been removed through excavation. The extraction of groundwater at the eastern boundary
has removed COIs from groundwater. Extracted groundwater would be discharged under an NPDES permit in accordance with applicable
regulatory requirements.
Degree of expected reductions
There is insufficient post -excavation data following source removal to assess the time for the groundwater to achieve standards by
natural attenuation. After the five year effectiveness monitoring period, the model may be refined to accurately predict the time
required.
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
Residuals might be present below regulatory standards when standards are met over time, as intended. Residuals removed through
groundwater extraction and source removal have been and will be managed in accordance with applicable regulatory requirements.
02L Standards at the Compliance Boundary
Predictive modeling indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500
years. This is likely due to conservative assumptions in the models. A robust pump -and -treat system was simulated in the Flow
and Transport model (Appendix F). Results of those simulations indicate groundwater extraction and infiltration would not
decrease COI concentrations at the compliance boundary faster than what the MNA simulations predict. In fact, the pump -and -
treat simulation for selenium indiated concentrations would decrease to less than the 02L standard quicker under natural
attenuation. These results are due to the limited post -excavation dataset and the lack of monitoring wells downgradient of the
compliance boundary. Insufficient land surface is available to install wells beyond the compliance boundary. The models used
conservative assumptions to predict COI concentrations in groundwater beneath the cooling pond. At the time of the CAP Update
preparation, only three quarters of post excavation data were available (September & December 2019, March 2020). No post -
excavation data related to the FPA is available. There is insufficient post -excavation data available to accurately predict future
COI concentrations in grouindwater beyond the compliance boundary. After the five year monitoring period, the models can be
refined to accurately predict the time required to reach compliance with regulatory standards. The groundwater system is
beginning to reach equlibrium. The geochemical and MNA evaluations identified multiple areas where natural attenuation has
already occured. Recent groundwater sampling results indicate source removal is already providing the chemical environment
necessary for attenuation.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow
zone, there is a notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III)
and potentially the precipitation of ferrihydrite, which would provide additional sorption sites for COI attenuation. It appears the
system is naturally approaching the elevated EH values. Though not confirmed, the increased EH might be due to the large flux
of infiltrating rainwater after excavation. These observations can be confirmed with the proposed five-year post -excavation EMP.
Natural attenuation is occurring in the areas northwest of the 1984 ash basin, southeast of the 1971 ash basin and FPA, off -Site
near SMW-01C, and downgradient of the FADA within the FCPA. Boron and arsenic concentrations in wells on the west side of
the ash basins are also showing decreasing trends in some areas. COI concentrations are anticipated to naturally attenuate with
time as the groundwater system reaches equilibrium after excavation.
Prepared by: GTC Checked by: JEC & WJW
Page 9 of 10

Remedial Alternatives
Remedial Alternative 2
Source Control by Excavation, Continued Groundwater
Extraction and Treatment at the Eastern Property Line,
Confirmation Monitoring with a Restricted Groundwater
Use Designation over a small portion of the Site's cooling
pond, and 5 year EMP review
N
d
M
m
c
L
Q
m
d
E
d
Remedial Alternative 2 relies on, source excavation, continued
groundwater extraction and treatment, and confirmation monitoring. In
addition to these methods for reducing COI concentrations in
groundwater, institutional controls would also be used to prevent
receptor exposure. The institutional control of a Restricted Groundwater
Use Designation over a small portion of the Site's cooling pond would
further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 1
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Costs to Implement Remedial Alternative 2
Capital Costs
$259,000
Operations, Maintenance, and Monitoring Costs
$198,000
Total Life Cycle Costs
$415,000
The cost estimate was developed to reflect the cost of implementing Remedial Alternative 2 for Source Areas 1 and 2. Costs to
implement RA 2 would be based on include the labor and materials to monitor and maintain appropriate wells and continue operation of
the extraction system.
Life cycle costs are determined using a Net Present Value (NPV) of expenditures for initial Capital costs and annual 0&M expenses for
the duration of the remedy. A Discount Rate of 5% assumed in developing the cost estimate.
Stakeholder Sentiment Regarding Implementation
It is expected that there would be positive and negative sentiment about implementation of an alternative that enlists an MNA
program. No landowner would be affected and groundwater Co
do not pose an unacceptable risk to potential human or
It
receptors.
The property is owned and controlled by Duke Energy, but a Restricted Groundwater Use Designation over a small portion of the
Site's cooling pond would further protect potential groundwater users. The site is an operating gas fired, combined cycle electric
power plant and will be in industrial use for the foreseeable future. Some community stakeholders might consider the time frame
to achieve remediation goals to be unacceptable.
Until the final corrective action is developed and comments are received and reviewed, assessment of community acceptance
will not be fully informed.
Prepared by: GTC Checked by: JEC & WJW
Page 10 of 10

Remediation Alternatives
Remediation Alternative 1
Source Control by Excavation and Monitored Natural
Attenuation
Remediation Alternative 1 relies on, source excavation and natural
attenuation mechanisms to reduce COI concentrations over time to
meet corrective action goals.
1.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
A. Protection of Human Health and the 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 FADA and FCPA have been identified. The assessment conservatively included potential recreational
receptors in the Site's NPDES cooling pond (Lake Sutton) and the Cape Fear River. Human receptors are not affected by groundwater from the
Site as water supply wells are located upgradient or beyond the hydrological divide. Furthermore, within approximately 0.5 mile of the ash
basins compliance boundary, 4 businesses were fitted with water treatment systems, 4 business were connected to county water supply, 1
additional business is planned to be connected to county water supply, and two public water supply wells were abandoned.
A restricted groundwater use designation is an institutional control that would further protect human health. The site is an operating gas fired,
combined cycle electric power plant and will be in industrial use for the foreseeable future.
Environment
There were no detected concentrations of COIs in the Sutton Cooling Pond intake canal that exceeded 02B standards. The FADA and FCPA do
not cause an increase in risks to ecological receptors evaluated for the exposure area, based on the results of an ecological risk assessment
performed for the Site using USEPA guidance (see Appendix E).
B. Compliance with Applicable Federal, State, and Local Regulations
Federal
Remedial Alternative 1 complies with USEPA CCR Rule specified in 40 Code of Federal Regulations (CFR) § 257.
State
Remedial Alternative 1 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 County officials per 15A NCAC 02L .0114(b). A Restricted
Groundwater Use Designation can be implemented in compliance with local laws and regulations.
F'repareo Dy: U I U unecked by: JJEU & wJw
Page 1of10

Remediation Alternatives
Remediation Alternative 1
Source Control by Excavation and Monitored Natural
Attenuation
Remediation Alternative 1 relies on, source excavation and natural
attenuation mechanisms to reduce COI concentrations over time to
meet corrective action goals.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
C. Technical & Logistical Feasibility
Ability to construct and operate technology
There are 18 monitoring wells already installed related to the FADA and FCPA. No significant construction would be required for implementation.
Other than potential installation of additional monitoring wells, no significant construction is required for implementation.
Reliability of technology
MNA and the other technologies used in Remedial Alternative 1 have 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 would not adversely impact the implementation of
other potential remedial actions; in fact, Remedial Alternative 2 contains all elements of Remedial Alternative 1.
Ability to monitor effectiveness of remedy
Effectiveness is monitored through evaluation of COI concentrations over time in accordance with a post -excavation groundwater effectiveness
monitoring program.
Ability to coordinate and obtain approvals from other agencies
An NPDES permit exists for the facility and currently includes provisions for ongoing groundwater extraction at the site. Restricted Groundwater
Use Designations can be readily obtained.
Availability of services and materials
An extensive groundwater monitoring well network already exists. 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 Remedial Alternative 1.
Design
MNA is readily implementable. The existing monitoring well network can be utilized to design the MNA network.
Permitting
The facility expects an NPDES permit to be issued that will allow them to manage and discharge the water contained in the FADA. The NPDES
permit could be modified, if necessary.
Soil Erosion and Sediment Control permits are required for land disturbance activities, including well installation. These permits are a
straightforward to procure.
rreparea Dy: uu I tt; c;neCKea oy: itu a wjw
Page 2 of 10

Remediation Alternatives
Remediation Alternative 1
Source Control by Excavation and Monitored Natural
Attenuation
Remediation Alternative 1 relies on, source excavation and natural
attenuation mechanisms to reduce COI concentrations over time to
meet corrective action goals.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
E. Short-term Effectiveness
Protection of Community during remediation
The community would 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 Sutton due to nature of the work would be de Minimis. Implementation and maintenance of
an effectiveness monitoring program would be in place to evaluate variations from expected conditions. Alternative measures could be taken to
address variations. Potential risks to groundwater users could be further controlled by a Restricted Groundwater Use Designation over a small
portion of the Site's cooling pond.
Work 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 relevant training and supporting documentation to verify competency.
Environmental impacts
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 indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500 years. This is likely
due to conservative assumptions in the models. At the time of CAP Update preparation, only three quarters of post -excavation data were
available (September & December 2019, March 2020). No post -excavation data related to the FPA is available. There is insufficient post -
excavation data available to accurately predict MNA. After the five year monitoring period, the models can be refined to accurately predict the
time required.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow zone, there is a
notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III) and potentially the precipitation of
ferrihydrite, which would provide additional sorption sites for COI attenuation. The proposed contingency option of installing air-sparging wells is
expected to have a similar increase in EH. It appears the system is naturally approaching elevated EH values. Though not confirmed, the
increased EH might be due to the large flux of infiltrating rainwater after excavation. These observations can be confirmed with the proposed five-
year post -excavation EMP.
F. Long-term Effectiveness
Adequacy and reliability of controls
Implementation and maintenance of an effectiveness monitoring program would be in place to evaluate variations from expected conditions.
Alternative measures could be taken to address variations. Potential risks to groundwater users is further mitigated by the connection of 5
businesses to New Hanover County water supply, installation of water filtration systems for water supply wells for 4 businesses, and
abandonment of two public water supply wells within a 0.5-mile radius of the ash basin compliance boundaries. Implementation of institutional
controls may include a restricted groundwater use designation to further protect potential groundwater users.
Magnitude of Residual Risk
Implementation of Remedial Alternative 1 would 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 an institutional control of a Restricted
Groundwater Use Designation would further protect potential groundwater users.
rrepareo Dy: u I tt; c:neCKed Dy: etc: a wow
Page 3of10

Remediation Alternatives
Remediation Alternative 1
Source Control by Excavation and Monitored Natural
Attenuation
Remediation Alternative 1 relies on, source excavation and natural
attenuation mechanisms to reduce COI concentrations over time to
meet corrective action goals.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
G. Reduction of Toxicity, Mobility, & Volume
Treatment process used and materials treated
Treatment technology used in Remedial Alternative 1 are source control. MNA relies on the mechanisms that naturally attenuate the
concentrations of CCR inorganic constituents are dilution, dispersion, advection, sorption (including ion exchange and precipitation) and phyto-
attenuation
Volume of materials destroyed or treated
The source of COIs to the groundwater has been removed through excavation.
Degree of expected reductions
There is insufficient post -excavation data following source removal to assess the time for the groundwater to achieve standards by MNA. After the
five year effectiveness monitoring period, the model may be refined to accurately predict the time required.
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
Residuals may be present below regulatory standards as the system would be intended to meet standards over time. Residuals removed through
source removal have been and will be managed in accordance with applicable regulatory requirements.
02L Standards
Predictive modeling indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500 years. This is likely
due to conservative assumptions in the models. A robust pump -and -treat system was simulated in the Flow and Transport model (Appendix F).
Results of those simulations indicate groundwater extraction and infiltration would not decrease COI concentrations at the compliance boundary
faster than what the MNA simulations predict. In fact, the pump -and -treat simulation for selenium indicated concentrations would decrease to
less than the 02L standard quicker under natural attenuation. These results are due to the limited post -excavation dataset and the lack of
monitoring wells downgradient of the compliance boundary. Insufficient land surface is available to install wells beyond the compliance
boundary. The models used conservative assumptions to predict COI concentrations in groundwater beneath the cooling pond. At the time of
the CAP Update preparation, only three quarters of post excavation data were available (September & December 2019, March 2020). No post -
excavation data related to the FPA is available. There is insufficient post -excavation data available to accurately predict future COI
concentrations in groundwater beyond the compliance boundary. After the five year monitoring period, the models can be refined to accurately
predict the time required to reach compliance with regulatory standards. The groundwater system is beginning to reach equilibrium. The
geochemical and MNA evaluations identified multiple areas where natural attenuation has already occurred. Recent groundwater sampling
results indicate source removal is already providing the chemical environment necessary for attenuation.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow zone, there is a
notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III) and potentially the precipitation
of ferrihydrite, which would provide additional sorption sites for COI attenuation. It appears the system is naturally approaching
elevated EH values. Though not confirmed, the increased EH might be due to the large flux of infiltrating rainwater after excavation. These
observations can be confirmed with the proposed five-year post -excavation EMP.
Natural attenuation is occurring in the areas northwest of the 1984 ash basin, southeast of the 1971 ash basin and FPA, off -Site near SMW-
01C, and downgradient of the FADA within the FCPA. Boron and arsenic concentrations in wells on the west side of the ash basins are also
showing decreasing trends in some areas. COI concentrations are anticipated to naturally attenuate with time as the groundwater system
reaches equilibrium after excavation.
Prepared by: GTC Checked by: JEC & WJW
Page 4 of 10

Remediation Alternatives
Remediation Alternative 1
Source Control by Excavation and Monitored Natural
Attenuation
Remediation Alternative 1 relies on, source excavation and natural
attenuation mechanisms to reduce COI concentrations over time to
meet corrective action goals.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MNA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Costs to Implement Remedial Alternative 1
Capital Costs
Not developed
Annual Costs
Not developed
Total Life Cycle Costs
Not developed
The cost estimate was not developed to reflect the cost of implementing Remedial Alternative 1 for Source Areas 1 and 2. Costs to
implement Remedial Alternative 1 include the labor and materials to monitor and maintain appropriate wells and continue operation of the
extraction system. This alternative does not include the costs of confirmation monitoring and would be less than the cost estimate of RA2.
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.
Prepared by: GTC Checked by: JEC & WJW
Page 5of10

I Remediation Alternatives I
Remediation Alternative 2
Source Control by Excavation, Monitored Natural
Attenuation with a Restricted Groundwater Use
Designation of the Former Coal Pile Area, and a 5 year
EMP review
A
ru
E Remediation Alternative 2 relies on, source excavation, natural
d attenuation mechanisms to reduce COI concentrations over time to
IY
meet corrective action goals, and a 5 year EMP period. In addition to
these methods for reducing COI concentrations in groundwater,
institutional controls will also be used to prevent receptor exposure
The institutional control of a Restricted Groundwater Use Designation
of the Source Area 2 areas not covered by the ash basins compliance
boundary would further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MINA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
A. Protection of Human Health and the 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 FADA and FCPA have been identified. The assessment conservatively included potential recreational
receptors in the Site's NPDES cooling pond (Lake Sutton) and the Cape Fear River. Human receptors are not affected by groundwater from the
Site as water supply wells are located upgradient or beyond the hydrological divide. Furthermore, within approximately 0.5 mile of the ash
basins compliance boundary, 4 businesses were fitted with water treatment systems, 4 business were connected to county water supply, 1
additional business is planned to be connected to county water supply, and two public water supply wells were abandoned.
A restricted groundwater use designation is an institutional control that would further protect human health. The site is an operating gas fired,
combined cycle electric power plant and will be in industrial use for the foreseeable future.
If implemented after the five year review period, the contingency plan proposed in Section 5.13 would further protect human health.
Environment
There were no detected concentrations of COIs in the Sutton Cooling Pond intake canal that exceeded 02B standards. The FADA and FCPA do
not cause an increase in risks to ecological receptors evaluated for the exposure area, based on the results of an ecological risk assessment
performed for the Site using USEPA guidance (see Appendix E).
B. Compliance with Applicable Federal, State, and Local Regulations
Federal
Remedial Alternative 2 complies with USEPA CCR Rule specified in 40 Code of Federal Regulations (CFR) § 257.
State
Remedial 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.
Local
MNA would be subject to notification requirements to any affected parties and to County officials per 15A NCAC 02L .0114(b). A Restricted
Groundwater Use Designation can be implemented in compliance with local laws and regulations.
Prepared by: GTC Checked by: JEC & WJW
Page 6of10

I Remediation Alternatives I
Remediation Alternative 2
Source Control by Excavation, Monitored Natural
Attenuation with a Restricted Groundwater Use
Designation of the Former Coal Pile Area, and a 5 year
EMP review
to
ru
E Remediation Alternative 2 relies on, source excavation, natural
d attenuation mechanisms to reduce COI concentrations over time to
iY
meet corrective action goals, and a 5 year EMP period. In addition to
these methods for reducing COI concentrations in groundwater,
institutional controls will also be used to prevent receptor exposure
The institutional control of a Restricted Groundwater Use Designation
of the Source Area 2 areas not covered by the ash basins compliance
boundary would further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MINA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
C. Technical & Logistical Feasibility
Ability to construct and operate technology
There are 18 monitoring wells already installed related to the FADA and FCPA. No significant construction would be required for implementation.
Other than potential installation of additional monitoring wells, no significant construction is required for implementation.
Reliability of technology
MNA and the other technologies used in Remedial Alternative 2 have 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
Remedial Alternative 2 relies on mature technology and have been used to implement cleanup strategies for similar COIs. These technologies are
dependent on subsurface conditions and effectiveness of treatment approaches.
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
Soil erosion and sediment control permits are relatively straightforward and could be readily obtained from NCDEQ. An NPDES permit exists for
the facility and currently includes provisions for ongoing groundwater extraction at the eastern property boundary. A Restricted Groundwater Use
Designation could be implemented in compliance with local laws and regulations.
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
There are no requirements for bench scale testing to implement Remedial Alternative 2.
Design
MNA is readily implementable. The existing monitoring well network can be utilized to design the MNA network.
Permitting
The facility expects an NPDES permit to be issued that will allow them to manage and discharge the water in the FADA. The NPDES permit
could be modified, if necessary.
Soil Erosion and Sediment Control permits are required for land disturbance activities, including well installation. These permits are a
straightforward to procure.
Prepared by: GTC Checked by: JEC & WJW
Page 7of10

I Remediation Alternatives I
Remediation Alternative 2
Source Control by Excavation, Monitored Natural
Attenuation with a Restricted Groundwater Use
Designation of the Former Coal Pile Area, and a 5 year
EMP review
A
rV
E Remediation Alternative 2 relies on, source excavation, natural
d attenuation mechanisms to reduce COI concentrations over time to
iY
meet corrective action goals, and a 5 year EMP period. In addition to
these methods for reducing COI concentrations in groundwater,
institutional controls will also be used to prevent receptor exposure
The institutional control of a Restricted Groundwater Use Designation
of the Source Area 2 areas not covered by the ash basins compliance
boundary would further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MINA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
E. Short-term Effectiveness
Protection of Community during remediation
The community would 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 Sutton due to nature of the work would be de Minimis. Implementation and maintenance of
an effectiveness monitoring program would be in place to evaluate variations from expected conditions. Alternative measures could be taken to
address variations. Potential risks to groundwater users could be further controlled by a Restricted Groundwater Use Designation over a small
portion of the Site's cooling pond.
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 relevant training and supporting documentation to verify competency.
Environmental impacts
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.
In addition to the energy consumption required to operate the existing extraction and treatment system at the eastern property boundary,
remedial Alternative 2 has increased energy consumption to pump water from the discharge canal to the excavated FADA.
Time until RA objectives are achieved
Predictive modeling indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500 years. This is likely
due to conservative assumptions in the models. At the time of CAP Update preparation, only three quarters of post -excavation data were
available (September & December 2019, March 2020). No post -excavation data related to the FPA is available. There is insufficient post -
excavation data available to accurately predict MNA. After the five year monitoring period, the models can be refined to accurately predict the
time required.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow zone, there is a
notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III) and potentially the precipitation of
ferrihydrite, which would provide additional sorption sites for COI attenuation. It appears the system is naturally approaching elevated EH values.
Though not confirmed, the increased EH might be due to the large flux of infiltrating rainwater after excavation. These observations can be
confirmed with the proposed five-year post -excavation EMP.
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 will include a deed restriction and Restricted Designation to further protect potential groundwater users.
Magnitude of Residual Risk
Implementation of Remedial Alternative 2 would 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 an institutional control of a Restricted
Groundwater Use Designation would further protect potential groundwater users.
vreparec Dy: u I L, l;neCKea Dy: dtl: & wjw
Page 8of10

I Remediation Alternatives I
Remediation Alternative 2
Source Control by Excavation, Monitored Natural
Attenuation with a Restricted Groundwater Use
Designation of the Former Coal Pile Area, and a 5 year
EMP review
A
rV
E Remediation Alternative 2 relies on, source excavation, natural
d attenuation mechanisms to reduce COI concentrations over time to
19
meet corrective action goals, and a 5 year EMP period. In addition to
these methods for reducing COI concentrations in groundwater,
institutional controls will also be used to prevent receptor exposure
The institutional control of a Restricted Groundwater Use Designation
of the Source Area 2 areas not covered by the ash basins compliance
boundary would further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MINA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
G. Reduction of Toxicity, Mobility, & Volume
Treatment process used and materials treated
Treatment technology used in Remedial Alternative 2 is source control. The mechanisms that naturally attenuate the concentrations of CCR
inorganic constituents are dilution, dispersion, advection, sorption (including ion exchange and precipitation) and phyto-attenuation.
Volume of materials destroyed or treated
The source of COIs to the groundwater has been removed through excavation. Extracted groundwater would be discharged under an NPDES
permit in accordance with applicable regulatory requirements.
Degree of expected reductions
There is insufficient post -excavation data following source removal to assess the time for the groundwater to achieve standards by MNA. After the
five year effectiveness monitoring period, the model may be refined to accurately predict the time required.
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
Residuals may be present below regulatory standards as the system would be intended to meet standards over time. Residuals removed through
source removal have been and will be managed in accordance with applicable regulatory requirements.
02L Standards
Predictive modeling indicates compliance to regulatory standards at the compliance boundary would not be achieved in 500 years. This is likely
due to conservative assumptions in the models. A robust pump -and -treat system was simulated in the Flow and Transport model (Appendix F).
Results of those simulations indicate groundwater extraction and infiltration would not decrease COI concentrations at the compliance boundary
faster than what the MNA simulations predict. In fact, the pump -and -treat simulation for selenium indiated concentrations would decrease to
less than the 02L standard quicker under natural attenuation. These results are due to the limited post -excavation dataset and the lack of
monitoring wells downgradient of the compliance boundary. Insufficient land surface is available to install wells beyond the compliance
boundary. The models used conservative assumptions to predict COI concentrations in groundwater beneath the cooling pond. At the time of
the CAP Update preparation, only three quarters of post excavation data were available (September & December 2019, March 2020). No post -
excavation data related to the FPA is available. There is insufficient post -excavation data available to accurately predict future COI
concentrations in grouindwater beyond the compliance boundary. After the five year monitoring period, the models can be refined to accurately
predict the time required to reach compliance with regulatory standards. The groundwater system is beginning to reach equlibrium. The
geochemical and MNA evaluations identified multiple areas where natural attenuation has already occured. Recent groundwater sampling results
indicate source removal is already providing the chemical environment necessary for attenuation.
Groundwater sampling results over the past year demonstrate that while the pH is remaining relatively stable within each flow zone, there is a
notable increase in the EH of groundwater. This increase in EH might lead to the oxidation of Fe(II) to Fe(III) and potentially the precipitation
of ferrihydrite, which would provide additional sorption sites for COI attenuation. It appears the system is naturally approaching elevated EH
values. Though not confirmed, the increased EH might be due to the large flux of infiltrating rainwater after excavation. These observations can
be confirmed with the proposed five-year post -excavation EMP.
Natural attenuation is occurring in the areas northwest of the 1984 ash basin, southeast of the 1971 ash basin and FPA, off -Site near SMW-
01C, and downgradient of the FADA within the FCPA. Boron and arsenic concentrations in wells on the west side of the ash basins are also
showing decreasing trends in some areas. COI concentrations are anticipated to naturally attenuate with time as the groundwater system
reaches equilibrium after excavation.
Prepared by: GTC Checked by:
Page 9 of 10

I Remediation Alternatives I
Remediation Alternative 2
Source Control by Excavation, Monitored Natural
Attenuation with a Restricted Groundwater Use
Designation of the Former Coal Pile Area, and a 5 year
EMP review
to
ru
E Remediation Alternative 2 relies on, source excavation, natural
d attenuation mechanisms to reduce COI concentrations over time to
meet corrective action goals, and a 5 year EMP period. In addition to
these methods for reducing COI concentrations in groundwater,
institutional controls will also be used to prevent receptor exposure
The institutional control of a Restricted Groundwater Use Designation
of the Source Area 2 areas not covered by the ash basins compliance
boundary would further protect potential groundwater users.
Notes:
CCR - coal combustion residuals
CFR - Code of Federal Regulations
COI - constituent of interest
CSM - conceptual site model
LRB - Lined Retention Basin
MINA - monitored natural attenuation
NCAC - North Carolina Administrative Code
NCDEQ - North Carolina Department of Environmental Quality
NPDES - National Pollution Discharge Elimination System
NPV - net present value
O&M - operation and maintenance
UIC - Underground Injection Control
USEPA - U.S. Environmental Protection Agency
APPENDIX O
REMEDIATION ALTERNATIVES SUMMARY - SOURCE AREA 2
CORRECTIVE ACTION PLAN UPDATE
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Costs to Implement Remedial Alternative 2
Capital Costs
$259,000
Operations, Maintenance, and Monitoring
$198,000
Costs
Total Life Cycle Costs
$415,000
The cost estimate was developed to reflect the cost of implementing Remedial Alternative 2 for Source Areas 1 and 2. Costs to implement RA
2 would be based on include the labor and materials to monitor and maintain appropriate wells and continue operation of the extraction
system.
Life cycle costs are determined using a Net Present Value (NPV) of expenditures for initial Capital costs and annual 0&M expenses for the
duration of the remedy. A Discount Rate of 5% assumed in developing the cost estimate.
Page 10 of 10