NC0024406_BCSS_Appendix N_20191231

Corrective Action Plan Update December 2019
Belews Creek Steam Station
APPENDIX N
SynTerra
REMEDIATION ALTERNATIVES SUMMARY

APPENDIX N
Privileged Confidential
Remediation Alternatives
Remediation Alternative 1
Monitored Natural Attenuation
Monitored Natural Attenuation (MNA) relies on natural attenuation
mechanisms to reduce constituent of interest (COI) concentrations over time
to meet corrective action goals.
For inorganic constituents, these processes include adsorption to soil and
bedrock surfaces, precipitation, ion exchange, dilution and dispersion.
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
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 basin have been identified.
The assessment conservatively included potential recreational receptors
in Dan River and Belews Reservoir. Human receptors are not affected
by groundwater from the Site as water supply wells are located
upgradient or outside the drainage basin.
Furthermore, 36 water supply wells within 0.5 miles of the ash basin
have been supplied with water filtration systems by Duke Energy.
Environment
An ecological risk assessment was performed for the Belews Creek
Steam Station (BCSS) using U.S. Environmental Protection Agency
(USEPA) guidance (see Appendix Q. The BCSS ash basin does not
cause an increase in risks to ecological receptors (mallard duck, great
blue heron, muskrat, river otter and killdeer bird) evaluated for the
Belews Reservoir and Dan River exposure area.
Federal
MINA complies with USEPA CCR Rule specified in 40 Code of
Federal Regulations (CFR) § 257.
State
MNA will comply with Coal Ash Management Act and 15A NCAC
02L .0106 (1), 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. See
Appendix I for additional details on MNA.
Local
MNA is subject to notification requirements to affected parties
(the owners of Parcel A) and Stokes County officials per
Subchapter 02L .0409.
Ability to construct and operate technology
There are over 170 monitoring wells already installed related to the 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 Conceptual Site Model (CSM) supports
the reliability of an MINA 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 an effectiveness
groundwater 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 in the central North Carolina area to
support effectiveness monitoring.
Page 1 of 12

APPENDIX N
Privileged Confidential
Remediation Alternatives
Remediation Alternative 1
Monitored Natural Attenuation
Monitored Natural Attenuation (MNA) relies on natural attenuation
mechanisms to reduce constituent of interest (COI) concentrations over time
to meet corrective action goals.
For inorganic constituents, these processes include adsorption to soil and
bedrock surfaces, precipitation, ion exchange, dilution and dispersion.
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
Requirements for bench scale testing
There are no requirements for bench scale testing.
Design
MNA is readily implementable. The existing monitoring well network can be utilized to design
an MNA network.
Permitting
Soil Erosion and Sediment Control permits are required for land disturbance activities, including
well installation. These permits are a straightforward to procure.
Protection of Community
Community will not be impacted during remediation as activities will be performed
on Duke Energy property and anticipated increase in traffic on roads leading to
BCSS due to nature of the work will be de minimis.
Worker Protection
Work would be performed under a Health & Safety Plan, which identifies risks and
mitigation measures for the protection of workers and the environment. All
personnel would be required to take relevant training and supply 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 RA objectives are achieved
Predictive groundwater modeling indicates compliance to regulatory standards at
the compliance boundary in approximately 700 years following basin closure.
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 can
be taken to address variations, if warranted. Potential risk to groundwater users
was further controlled by the installation of water filtration systems for water supply
wells within 0.5 miles of the BCSS ash basin. Implementation of institutional
controls (provided by the restricted designation) will further serve to 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 risk to groundwater use is further controlled by
water filtration systems to water supply users within 0.5 miles of the BCSS ash
basin and by institutional controls that may include a restricted designation.
Page 2 of 12

Remediation Alternatives
Remediation Alternative 1
Monitored Natural Attenuation
Monitored Natural Attenuation (MNA) relies on natural attenuation
mechanisms to reduce constituent of interest (COI) concentrations over time
to meet corrective action goals.
For inorganic constituents, these processes include adsorption to soil and
bedrock surfaces, precipitation, ion exchange, dilution and dispersion.
APPENDIX N
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
Treatment Process Used and Materials Treated
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/IMAC or Site -specific background values, whichever is
greater.
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 about 700 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 of natural processes.
Type and Quantity of Residuals Remaining
None. The natural attenuation processes do not create additional residuals for inorganic COIs.
102L Standards at the Compliance Boundary
me to achieve the remediation goal of reducing the concentration of boron
!yond the compliance boundary to levels less than the 02L standard was
,timated by predictive flow and transport modeling. The flow and
ansport model predicts that boron concentrations in groundwater would
eet the 02L boron standard of 700 pg/L at the compliance boundary in
)proximately 700 years.
Privileged Confidential
Costs to Implement Remedial Alternative 1
Captial Costs
$622,000
Annual Costs
$2,675,000
Total Life Cycle
$3,297,000
Costs
Costs to implement MINA would be based on the assumption of 10 additional monitoring
well. Costs would also include the needed labor and materials to monitor approximately 80
wells on a semi-annual basis, and redevelopment/replacement of wells, as necessary, and
routine labor for annual and 5-year reporting.
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.
Page 3 of 12

Remediation Alternatives
Remediation Alternative 1
Monitored Natural Attenuation
Monitored Natural Attenuation (MNA) relies on natural attenuation
mechanisms to reduce constituent of interest (COI) concentrations over time
to meet corrective action goals.
For inorganic constituents, these processes include adsorption to soil and
bedrock surfaces, precipitation, ion exchange, dilution and dispersion.
APPENDIX N
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
Stakeholder Sentiment Regarding Implementation
is expected that there will be positive and negative sentiment about implementation of
MNA program. Groundwater COIs do not pose an unacceptable risk to potential human
ecological receptors.
With the exception of Parcel A, the remaining property is owned by Duke Energy, which is
anticipated to have institutional controls. Some community stakeholders might consider a
700-year time frame to achieve remediation goals for boron to be unacceptable. However,
community stakeholders with concerns regarding the capital and near -term O&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 comma
(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
MNA remedy will impact the environment through energy consumption and associated
ssions associated with installation of additional monitoring wells, periodic sampling and
lysis of groundwater.
Some clearing of wooded areas would be required to 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.
Privileged Confidential
Page 4 of 12

APPENDIX N
Privileged Confidential
Remediation Alternatives
Remediation Alternative 2
Groundwater Extraction and Treatment
Groundwater extraction which relies on pumping and removal of groundwater
to reduce concentrations of COI over time to meet corrective action goals.
This remedy uses 10 existing extraction wells (part of the current interim
extraction system) and 103 new extraction wells to the north and northwest of
the ash basin. Extracted water will be treated and discharged through the
existing NPDES system.
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
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 basin have been identified.
The assessment conservatively included potential recreational receptors
in Dan River and Belews Reservoir. Human receptors are not affected
by groundwater from the Site as water supply wells are located
upgradient or outside the drainage basin.
Furthermore, 36 water supply wells within 0.5 miles of the ash basin
have been supplied with water filtration systems by Duke Energy.
Environment
An ecological risk assessment was performed for the Belews Creek
Steam Station (BCSS) using U.S. Environmental Protection Agency
(USEPA) guidance (see Appendix Q. The BCSS ash basin does not
cause an increase in risks to ecological receptors (mallard duck, great
blue heron, muskrat, river otter and killdeer bird) evaluated for the
Belews Reservoir and Dan River exposure area.
Federal
The groundwater extraction and treatment, as specified in
remediation Alternative 2, would comply with USEPA CCR Rule
specified in 40 CFR § 257.
State
Alternative 2 would comply with CAMA, 15A NCAC 02L
(regulation and groundwater standards) and NCAC 02B (surface
water standards). NPDES permitted discharge is in place. The
NPDES Permit might 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 will be required per NCDEQ and
Stokes County regulations.
Local
Groundwater extraction and treatment can be implemented in
compliance with local laws and regulations.
Ability to construct and operate technology
Technology to construct and operate a groundwater extraction and treatment system proposed in remedial Alternative 2
is straightforward and readily available. Technologies to treat extracted groundwater exist, but require experience to
successfully operate.
Reliability of technology
Groundwater extraction is a mature technology and has been used to implement cleanup strategies for similar COIs. It is
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 from being implemented, if warranted.
Groundwater extraction wells can be added to the proposed system or removed from service, as conditions dictate.
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 O&M Plan would be implemented to track the gallons of
water extracted and the COI mass removed on a cumulative basis. Ongoing review of data and periodic updates to the
groundwater model could 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 from Stokes County.
An NPDES permit exists for the facility but may need to be modified for the discharge of treated groundwater, which is a
straight -forward process.
Availability of services and materials
All services and materials are readily available. The existing interim action plan accelerated remediation groundwater
extraction system has been in place and operating since March 2018.
Page 5 of 12

APPENDIX N
Privileged Confidential
Remediation Alternatives
Remediation Alternative 2
Groundwater Extraction and Treatment
Groundwater extraction which relies on pumping and removal of groundwater
to reduce concentrations of COI over time to meet corrective action goals.
This remedy uses 10 existing extraction wells (part of the current interim
extraction system) and 103 new extraction wells to the north and northwest of
the ash basin. Extracted water will be treated and discharged through the
existing NPDES system.
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
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 by
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.
Protection of Community during remediation
Community will not be impacted during remediation as activities will be performed
on Duke Energy property and anticipated increase in traffic on roads leading to
BCSS due to nature of the work will be de minimis.
Protection of workers during remediation
Work would be performed under a Health & Safety Plan, which identifies risks and
mitigation measures for the protection of workers and the environment. All
personnel would be required to take relevant training and supply supporting
documentation to verify competency.
Environmental impacts
Remedial Alternative 2 has increased energy consumption to operate the
groundwater extraction 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 RA objectives are achieved
Predictive modeling indicates compliance to regulatory standards at the
compliance boundary in approximately 300 years after the system is placed into
operation.
Adequacy and reliability of controls
An extraction system installed using predictive modeling should be effective in
reducing COI concentrations in groundwater over time.
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 needed. Risk is
mitigated to potential groundwater users by water filtration systems and
institutional controls (provided by the restricted designation). An Operations &
Maintenance plan would be developed and implemented to operate the remedial
system and document long-term effectiveness.
Magnitude of Residual Risk
The magnitude of residual risk will decrease as the remedial program progresses
over its approximate 300-year timeframe. Implementation of the groundwater
extraction system will result in a reduction of COIs in groundwater at BCSS. Current
state and predicted future state groundwater conditions do not indicate
unacceptable risk to human health or environment. Potential risk is further
mitigated to groundwater users within 0.5 miles of the BCSS ash basin by the
addition of water filtration systems and institutional controls that may include a
restricted designation.
Page 6 of 12

APPENDIX N
Privileged Confidential
Remediation Alternatives
Remediation Alternative 2
Groundwater Extraction and Treatment
Groundwater extraction which relies on pumping and removal of groundwater
to reduce concentrations of COI over time to meet corrective action goals.
This remedy uses 10 existing extraction wells (part of the current interim
extraction system) and 103 new extraction wells to the north and northwest of
the ash basin. Extracted water will be treated and discharged through the
existing NPDES system.
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
Treatment process used and materials treated
Treatment of affected groundwater would be performed using the same water treatment system
for the decanting/dewatering the ash basin.
Volume of materials destroyed or treated
COIs would be removed from groundwater by pumping, 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 over time. The Flow
and Transport Model predicts concentrations of boron would be below the 02L standard at or
beyond the compliance boundary in a 300-year timeframe.
Irreversible Treatment
Mass removal will not be reversible for COI
Type and quantity of residuals remaining
Residuals may be present below regulatory standards as the system would be intended to meet
standards over time.
102L Standards at the Compliance Boundary
me to achieve the remediation goal of reducing the concentration of boron
or beyond the compliance boundary to levels less than the 02L standard
as estimated by predictive flow and transport modeling. The flow and
ansport model predicts that boron concentrations in groundwater would
eat the 02L boron standard of 700 pg/L at the compliance boundary in
300 years after system operation.
Costs to Implement Remedial Alternative 2
Captial Costs
$8,184,000
Annual Costs
$7,902,000
Total Life Cycle
$16,086,000
Costs
Costs to implement Remedial Alternative 2 would be based on the assumption of installing
1 additional monitoring well, a network of 103 extraction wells, and associated piping and
control system.
Costs would also include the needed labor and materials to monitor approximately 57
wells on a semi-annual basis, and redevelopment/replacement of wells, as necessary, and
routine labor for annual and 5-year reporting.
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.
Page 7 of 12

Remediation Alternatives
Remediation Alternative 2
Groundwater Extraction and Treatment
Groundwater extraction which relies on pumping and removal of groundwater
to reduce concentrations of COI over time to meet corrective action goals.
This remedy uses 10 existing extraction wells (part of the current interim
extraction system) and 103 new extraction wells to the north and northwest of
the ash basin. Extracted water will be treated and discharged through the
existing NPDES system.
APPENDIX N
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
Stakeholder Sentiment Regarding Implementation
It is expected that there will be positive and negative sentiment about implementation of
an active groundwater remedy that includes groundwater extraction and treatment.
Groundwater COIs do not pose an unacceptable risk to potential human or ecological
receptors. With the exception of Parcel A, the remaining affected property is owned by DI
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 Dan River and the discharge would be treated as
necessary to meet permit limits.
An expanded groundwater extraction system that addresses the COI plume across the
entire north and northwest perimeter of the basin may improve public perception. This
alternative would likely be perceived as more robust than MNA in addressing groundwater
impacts even though human health and ecological risks are essentially the same between
MNA and groundwater extraction.
Some community stakeholders might consider a 300-year time frame to achieve
remediation goals for boron preferable to the predicted time under an MNA scenario.
Until the final Site remedy is developed and comments are received and reviewed,
assessment of community acceptance will not be fully known.
lAbility to Augment the Remedy, if Needed
Groundwater extraction using conventional well technology is an
adaptable process. It can be 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.
An effectiveness monitoring program would provide information about
changing Site conditions during and after source control measures.
While it is not expected, treatment of the groundwater discharge can be
modified to address changes in COI concentrations or permit limits.
Privileged Confidential
Environmental Footprint of the Remedy
The environmental footprint of Alternative 2 is the most emission -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 dramatically higher energy -consumption
metrics when measured against Alternative 3. Alternative 2 utilizes the same number of
extraction wells as Alternative 3 with no clean -water infiltration -wells or, which will generate a
lower material -related environmental footprint for the construction phase. However, the
extended timeframe of remediation system operation for Alternative 2 (300 years) when
compared to Alternative 3 (36 years) requires energy usage and produces air emissions far
exceeding the levels of 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 8 of 12

Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction with Clean Water Infiltration and
Treatment
Groundwater extraction with clean water infiltration and treatment which
relies on pumping groundwater and introduction of clean water to reduce
concentrations of COI over time to meet corrective action goals. This remedy
uses 10 existing extraction wells (part of the current interim extraction
system), 103 new extraction wells, 47 clean water infiltration wells and one
horizontal infiltration well to the north and northwest of the ash basin.
Extracted water will be treated and discharged through the existing NPDES
t
system.
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 N
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
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 basin have been identified.
The assessment conservatively included potential recreational receptors
in Dan River and Belews Reservoir. Human receptors are not affected
by groundwater from the Site as water supply wells are located
upgradient or outside the drainage basin.
Furthermore, 36 water supply wells within 0.5 miles of the ash basin
have been supplied with water filtration systems by Duke Energy.
Environment
An ecological risk assessment was performed for the Belews Creek
Steam Station (BCSS) using U.S. Environmental Protection Agency
(USEPA) guidance (see Appendix E). The BCSS ash basin does not
cause an increase in risks to ecological receptors (mallard duck, great
blue heron, muskrat, river otter and killdeer bird) evaluated for the
Belews Reservoir and Dan River exposure area.
Federal
The groundwater extraction specified in remediation Alternative
3 would comply with USEPA CCR Rule specified in 40 CFR § 257.
State
Alternative 3 would comply with CAMA, 15A NCAC 02L
(regulation and groundwater standards) and NCAC 02B (surface
water standards). NPDES permitted discharge is in place. The
NPDES Permit might need to be modified to accommodate the
discharge of treated groundwater. Procurement of Sediment and
Erosion Control permits associated with extraction, clean water
infiltration, and monitoring well installation will be required per
NCDEQ and Stokes County regulations.
Local
Groundwater extraction, clean water infiltration, and treatment
can be implemented in compliance with local laws and
regulations.
Ability to construct and operate technology
Technology to construct and operate a groundwater extraction, infiltration, and treatment system proposed in remedial
Alternative 3 is straightforward and readily available. Technologies to treat extracted groundwater exist, but require
experience to successfully operate.
Reliability of technology
Groundwater extraction and clean water infiltration is a mature technology and has been used to implement cleanup
strategies for similar COIs. It is 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 from being implemented, if warranted.
Groundwater extraction or infiltration wells can be added to the proposed system or removed from service, as conditions
dictate.
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 O&M Plan would be implemented to track the gallons of
water extracted and the COI mass removed on a cumulative basis. Ongoing review of data and periodic updates to the
groundwater model could 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 from Stokes County.
An NPDES permit exists for the facility but may need to be modified for the discharge of treated groundwater, which is a
straight -forward process.
Availability of services and materials
All services and materials are readily available. The existing interim action plan accelerated remediation groundwater
extraction system has been in place and operating since March 2018.
Privileged Confidential
Page 9 of 12

Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction with Clean Water Infiltration and
Treatment
Groundwater extraction with clean water infiltration and treatment which
relies on pumping groundwater and introduction of clean water to reduce
concentrations of COI over time to meet corrective action goals. This remedy
uses 10 existing extraction wells (part of the current interim extraction
system), 103 new extraction wells, 47 clean water infiltration wells and one
horizontal infiltration well to the north and northwest of the ash basin.
Extracted water will be treated and discharged through the existing NPDES
system.
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 N
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
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 by
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
Dan River water intake, extraction points, infiltration 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.
An Underground Injection Control (UIC) permit for infiltration of clean water into the
subsurface would be required in accordance with 15A NCAC 02C .0217.
Protection of Community during remediation
Community will not be impacted during remediation as activities will be performed
on Duke Energy property and anticipated increase in traffic on roads leading to
BCSS due to nature of the work will be de minimis.
Protection of workers during remediation
Work would be performed under a Health & Safety Plan, which identifies risks and
mitigation measures for the protection of workers and the environment. All
personnel would be required to take relevant training and supply supporting
documentation to verify competency.
Environmental impacts
Remedial Alternative 3 has increased energy consumption to operate the
groundwater 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 RA objectives are achieved
Predictive modeling indicates compliance to regulatory standards at the
compliance boundary in approximately 36 years after the system is placed into
operation.
Privileged Confidential
Adequacy and reliability of controls
An extraction and infiltration system installed using predictive modeling should be
effective in reducing COI concentrations in groundwater over time. Use of
infiltration wells will accelerate pore volume turnover and reduce time to regulatory
compliance.
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 needed. Risk is
mitigated to potential groundwater users by water filtration systems and
institutional controls (provided by the restricted designation). An Operations &
Maintenance plan would be developed and implemented to operate the remedial
system and document long-term effectiveness.
Magnitude of Residual Risk
The magnitude of residual risk will decrease as the remedial program progresses
over its expected 36-year timeframe. Implementation of the groundwater
extraction and clean water infiltration system will result in a reduction of COIs in
groundwater at BCSS. Current state and predicted future state groundwater
conditions do not indicate unacceptable risk to human health or environment.
Potential risk is further mitigated to groundwater users within 0.5 miles of the
BCSS ash basin by the addition of water filtration systems and institutional controls
that may include a restricted designation.
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Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction with Clean Water Infiltration and
Treatment
Groundwater extraction with clean water infiltration and treatment which
relies on pumping groundwater and introduction of clean water to reduce
concentrations of COI over time to meet corrective action goals. This remedy
uses 10 existing extraction wells (part of the current interim extraction
system), 103 new extraction wells, 47 clean water infiltration wells and one
horizontal infiltration well to the north and northwest of the ash basin.
Extracted water will be treated and discharged through the existing NPDES
system.
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 N
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
Treatment process used and materials treated
Treatment of affected groundwater would be performed using the same water treatment system
for the decanting/dewatering the ash basin. Water used for infiltration will be treated as
necessary to ensure it meets the requirements specified in 15A NCAC 02C .0217 (UIC).
Volume of materials destroyed or treated
COIs would be removed from groundwater by pumping, 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 over time. The Flow
and Transport Model predicts concentrations of boron would be below the 02L standard at or
beyond the compliance boundary in a 36-year timeframe.
Irreversible Treatment
Mass removal will not be reversible for C0I
Type and quantity of residuals remaining
Residuals may be present below regulatory standards as the system would be intended to meet
standards over time.
102L Standards at the Compliance Boundary
me to achieve the remediation goal of reducing the concentration of boron
or beyond the compliance boundary to levels less than the 02L standard
as estimated by predictive flow and transport modeling. The flow and
ansport model predicts that boron concentrations in groundwater would
eet the 02L boron standard of 700 pg/L at a majority of the compliance
Iundary in approximately 13 years after system operation.
r the northwest perimeter of the ash basin waste boundary, the 500 foot
pliance boundary is reduced by approximately 250 feet. The reduced
pliance boundary results in a longer timeframe to achieve compliance in
small area. The predicted timeframe to achieve compliance for the
ill area is approximately 36 years after system startup and operation.
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]ml&;
Costs to Implement Remedial Alternative 3
Captial Costs
$12,238,000
Annual Costs
$10,146,000
Total Life Cycle
$22,384,000
Costs
Costs to implement Remedial Alternative 3 would be based on the assumption installing 1
additional monitoring well, a network of 113 groundwater vertical extraction wells, 47
vertical clean water infiltration wells, and one horizontal clean water infiltration well, and
associated piping and control system.
Costs would also include the needed labor and materials to monitor approximately 57
wells on a semi-annual basis, and redevelopment/replacement of wells, as necessary, and
routine labor for annual and 5-year reporting.
Life cycle costs are determined using a Net Present Value (NPV) of expenditures for initial
Capital costs and annual C&M expenses for the duration of the remedy. A Discount Rate of
5% assumed in developing the cost estimate.
Page 11 of 12

Remediation Alternatives
Remediation Alternative 3
Groundwater Extraction with Clean Water Infiltration and
Treatment
Groundwater extraction with clean water infiltration and treatment which
relies on pumping groundwater and introduction of clean water to reduce
concentrations of COI over time to meet corrective action goals. This remedy
uses 10 existing extraction wells (part of the current interim extraction
system), 103 new extraction wells, 47 clean water infiltration wells and one
horizontal infiltration well to the north and northwest of the ash basin.
Extracted water will be treated and discharged through the existing NPDES
system.
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 N
REMEDIATION ALTERNATIVES SUMMARY
CORRECTIVE ACTION PLAN UPDATE
BELEWS CREEK STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELEWS CREEK, NC
Stakeholder Sentiment Regarding Implementation
It is expected that there will be positive and negative sentiment about implementation of
an active groundwater remedy that includes groundwater extraction, clean water
infiltration and treatment. Groundwater COIs do not pose an unacceptable risk to potential
human or ecological receptors. With the exception of Parcel A, 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 Dan River and the discharge would be treated as
necessary to meet permit limits.
An expanded groundwater extraction and infiltration system that addresses the COI plume
across the entire north and northwest perimeter of the basin may improve public
perception. This alternative would likely be perceived as more robust than MNA in
addressing groundwater impacts even though human health and ecological risks are
essentially the same between MNA and groundwater extraction and infiltration.
Some community stakeholders might consider a 36-year time frame to achieve remediation
goals for boron preferable to the predicted time under an MNA scenario or 300-years
Dredicted for remedial Alternative 2.
Until the final Site remedy is developed and comments are received and reviewed,
assessment of community acceptance will not be fully known.
lAbility to Augment the Remedy, if Needed
Groundwater extraction and clean water infiltration using conventional
well technology is an adaptable process. It can be modified to address
changes to COI plume configuration or COI concentrations based on
actual field data. Individual well pressure heads and pumping rates can
be adjusted or eliminated, or additional wells can be installed to address
COI plume changes.
An effectiveness monitoring program would provide information about
changing Site conditions during and after source control measures.
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
The environmental footprint of Alternative 3 is the second -most, emission -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 utilizes approximately the same number of extraction
wells as Alternative 2, but also utilizes 1 horizontal and 47 vertical clean -water infiltration -
wells, which Alternative 2 does not employ. The additional remediation system components
required by Alternative 3 will generate higher material -related environmental footprint
emissions for the construction phase than Alternative 2. The analysis indicates operating the
infiltration -well network to be more energy -intensive in Alternative 3 than Alternative 2, as
well. However, the reduced timeframe of remediation system operation for Alternative 3 (36
years) when compared to Alternative 2 (300 years) produces air emissions less than half of
the levels of Alternative 3. Opportunities for system optimization and energy savings could be
pursued throughout the remediation timeframe, as conditions change and component
technologies possibly evolve.
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Page 12 of 12