Attach 1 - DE CAP Content Guid 1-23-19

Duke Energy Interpretation of Corrective Action Plan Content Guidance Provided by the
North Carolina Department of Environmental Quality
January 23, 2019
Introduction
The purpose of this document is to provide the North Carolina Department of Environmental
Quality (NCDEQ) Division of Water Resources (DWR) with Duke Energy's proposed approach for
preparing the groundwater Corrective Action Plans (CAPS) within the structure of the NCDEQ's
guidance titled "Corrective Action Plan Content for Duke Energy Coal Ash Facilities" [CAP
Guidance] dated April 27, 2018. This guidance provides the technical content and format
requested by the NCDEQ for preparing the CAPs associated with Duke Energy coal ash facilities.
Duke Energy's overall goal is to submit high quality CAPs that meet the regulatory requirements
found in 15A NCAC 2L .0106 based on the large datasets generated at each site by working with
the NCDEQ to gain clarity early in the CAP preparation process regarding what is required.
On January 3, 2019, representatives from NCDEQ met with Duke Energy and SynTerra to discuss
the CAP guidance. During the meeting it was agreed that Duke Energy would prepare our
interpretation of working within the CAP guidance framework and provide this interpretation to
the NCDEQ for review. Therefore, the following four documents are attached:
1. Duke Energy's proposed adjustments to the April 2018 CAP Guidance.
2. A table that provides supporting rationale for the proposed adjustments.
3. A general list of appendices common to all CAPs to provide clarity regarding the full
scope of the CAP submittal.
4. An example figure that uses an exceedance ratio approach that Duke Energy believes is
an effective way to present site data while reducing the total number of figures
requested on the CAP guidance.
Overall, we have adjusted the guidance to:
• Reflect our improved understanding of site conditions due to the substantial amount of
data collection and progress made since April 2018.
• Place more emphasis on corrective action analysis while recognizing that
Comprehensive Site Assessment (CSA) comments will be addressed as an appendix to
the CAP.
• Enable a more efficient CAP preparation and review process.
In some cases, we have either added a section (Executive Summary), or made a section more
prominent due to its importance (Conceptual Site Model), which will provide the basis for the
corrective action approach proposed. In other cases, we have adjusted the guidance to address
conflicting or redundant sections, or to place more emphasis on corrective action analysis
rather than representing assessment information previously provided to the NCDEQ.
In closing, Duke Energy believes that the attached documents provided herein have been
prepared within the framework of the NCDEQ's CAP guidance while adjusting it to enhance the

technical quality, the manageability of the CAP preparation and review process, and to facilitate
technical decision -making regarding site -specific approaches for corrective action.
Duke Energy appreciates the opportunity to provide this submittal and would be glad to discuss
the CAP approach to address any comments you may have.

Attachment 1
CORRECTIVE ACTION PLAN CONTENT FOR
DUKE ENERGY COAL ASH FACILITIES
Proposed Duke Energy Content
January 18, 2019
Best professional judgement must be applied to generate the Corrective Action Plan (CAP) documents. In
general, all items described in this guidance are expected to be addressed in the CAPs with the interpreted
adjustments included herein. Duke Energy is to provide justification/rationale concerning information not
provided as stipulated in this guidance.
EXECUTIVE SUMMARY
1. INTRODUCTION
A. Background
B. Purpose and Scope
C. Regulatory basis for closure and corrective action (note that "closure" refers here to source
control and (or) source excavation in accordance with Coal Ash Management Act (CAMA) and
(or) 15A NCAC 02L (02L) .0106, while "corrective action", "remediation", or "remedy" refer
here to the treatment of groundwater contamination)
a. CAMA requirements
b. 02L requirements
c. Other requirements such as court order, Federal requirements, etc.
D. List of Considerations by the Secretary for Evaluation of Corrective Action Plans as referenced
in 02L .0106 (i). This section will be addressed with a general written description of how these
items are considered in the CAPs.
a. Extent of any violations
b. Extent of any threat to human health or safety
c. Extent of damage or potential adverse effects to the environment
d. Technology available to accomplish restoration
e. Potential for degradation of the contaminants in the environment
f. Time and costs estimated to achieve groundwater quality restoration
g. Public and economic benefits to be derived from groundwater quality restoration.
E. Facility Description (summary from Comprehensive Site Assessment [CSA])
a. Location and history of land use (to include period prior to Duke ownership)
b. Operations and waste streams coincident with the ash basin (coal and only those non -
coal waste streams that may affect subsurface conditions at, or proximate to, the coal
ash basins or coincident sources.)
c. Overview of existing permits and Special Orders by Consent (National Pollutant
Discharge Elimination System, storm water, sediment and erosion control, etc.)
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2. RESPONSE TO COMPREHENSIVE SITE ASSESSMENT UPDATE COMMENTS IN SUPPORT OF CAP
DEVELOPMENT
For ease of review, NCDEQ's comment letters and Duke Energy's responses will be addressed in
an appendix to the CAPS. A summary table that identifies where these items are addressed will
also be included in the appendix to facilitate NCDEQ's review.
A. Include the Facility -Specific Comprehensive Site Assessment (CSA) Comment Letter from DEQ
to Duke Energy.
B. Duke Energy's response to the DEQ's letter. (NOTE: All deficiencies noted during the
Departments' review of the CSA Update report shall be addressed in an appendix to the
CAP.)
a. For each comment in the letter, note the specific section(s) of the CAP report that
addresses that comment in a table to be included in the appendix.
3. OVERVIEW OF SOURCE AREAS BEING PROPOSED FOR CORRECTIVE ACTION
Each source area has a unique waste footprint, waste volume and configuration, contaminant
configuration and transport characteristics, and potential receptors, if any. Consequently, each
source area will potentially need to be remediated in a unique way. For purposes of remediation
design and approval, each source area should be addressed separately as described in this
document. Arranging the report in this way will support an organized, orderly, and efficient
review of the proposed remedy. For facilities in which only one source area is defined (or
multiple source areas that can be combined into a single larger source area), the CAP sections
which pertain to additional source areas would not be needed. It is not the intent to require a
separate CAP Report submittal for each source area, rather a single facility CAP (Cliffside, e.g.)
submittal may contain the contents of multiple source areas. Please note that source control for
ash basins will in large part be performed through decanting of free water in the ash basin
followed by implementation of the approved closure plans. These source control actions are key
components of the overall groundwater corrective action program for each site. An overview of
source control and the approved closure plans for the source area(s) will be provided in the CAP.
Additional source areas may require additional corrective action and will be addressed in the CAP
as needed.
A. Small scale map showing the waste boundary of each source area proposed for corrective
action. The sources areas for each site were provided in a letter from the NCDEQ letter titled
"Final Comprehensive Site Assessment and Corrective Action Plans Approvals for Duke Energy
Coal Ash Facilities", dated [Insert date of final letter].
For cases in which more than one smaller source area is being combined as one larger
source area, show each "sub area" on the waste boundary map (i.e. show the waste
boundaries of the individual smaller source areas that are within the larger source
area)
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B. For source areas that are not hydrologically connected to the impoundments that will be
addressed in subsequent CSAs, provide a brief description of the source and schedule
(reference letter titled "Final Comprehensive Site Assessment and Corrective Action Plans
Approvals for Duke Energy Coal Ash Facilities", [Insert date]).
4. SUMMARY OF BACKGROUND DETERMINATIONS
A. Map showing all background sample locations for all media (groundwater, surface water, soil,
and sediments)
B. Table of background concentrations for soil. Include the corresponding Protection of
Groundwater (POG) Preliminary Soil Remediation Goal (PSRG). Approved Background
Threshold Values (BTVs) for soil and groundwater will be sent to Duke in a letter separate
from the CSA Comments. Please list the approved BTVs. A discussion of regional background
concentrations for similar geologic settings may be provided as context for BTVs.
C. Table of background concentration for groundwater. Include the appropriate 2L/IMAC
Standards. Approved Background Threshold Values (BTVs) for soil and groundwater will be
sent to Duke in a letter separate from the CSA Comments. Please list the approved BTVs. A
discussion of regional background concentrations for similar geologic settings may be
provided as context for BTVs.
D. Table of background concentrations for surface water. Include the appropriate 2B standards
and EPA recommended criteria. Present results of all surface water samples and sample
events from upstream locations.
E. Table of background concentrations for sediments. Present results of all sediment samples
and sample events from upstream or otherwise unimpacted sample locations.
5. CONCEPTUAL SITE MODEL
A. The conceptual site model (CSM) will present Duke Energy's interpretation of relevant site
conditions based on multiple lines of technical evidence developed through the collection of
a large multi -media dataset for each site. The CSM will in turn be used to form the basis of
the site -specific corrective action approach planned at each site. The following includes the
items from previous Section 6.A.b.i along with additional items to make the overall CSM more
robust.
a. Description of key site factors concerning the site geologic and hydrogeologic setting.
i. Local groundwater flow directions and gradients (current and following
closure).
ii. Particle tracking results, if available.
iii. Subsurface heterogeneities and other potential factors affecting flow and
transport including geochemical conditions.
iv. The role of matrix diffusion in/out of bedrock (bedrock porosity) on
constituent transport where appropriate.
v. Discuss onsite and offsite pumping influences affecting flow and transport.
vi. Other factors affecting flow and transport under current and future site
conditions.
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vii. The effects of naturally occurring constituents in site groundwater.
Location of source areas within the hydrogeologic setting (current and following
closure).
c. Describe potential on -site and off -site receptors and whether or not they are affected
by site related constituents above applicable criteria.
d. A description of the human health and ecological risk assessment results.
SOURCE AREA 1
Contents listed in Section 6 should be prepared separately for each additional source area (i.e.
Source Area 2, Source Area 3, etc., as applicable) in need of remediation.
Maps prepared for Source Area 1 should be large scale, typically 1" = 150 to 200 ft. and include
topographic contour intervals as agreed upon. However, scale adjustments may be made to
accommodate for reaching receptors; please discuss with Regional Office if this is necessary.
All plan view maps used in the CAP report should be oriented to extend to relevant identified
receptors (hydraulically downgradient supply wells and surface water features), to the extent
possible, based on the map scale and size of source area being depicted. Duke will provide
justification for selection of water supply wells and downgradient surface water features.
Constituents of interest (COls) considered for corrective action are those constituents with
concentrations consistently greater than the applicable standard at or beyond the compliance
boundary (whatever is the point of compliance depending on whether the source area(s) are
covered by a permit). 1 The following references to COls in this guidance and the CAP are
considered to be COls considered for corrective action.
A. Extent of Constituent Distribution
a. Source material within waste boundary. The Information requested below is to be
provided only to the extent the requested information was not provided in previous
submittals. A reference to the submittal where the requested information is provided
will be included in the CAP.
i. Description of waste material and history of placement
ii. Specific waste characteristics of source material
iii. Volume and physical horizontal and vertical extent of source material
mapped in plan -view and multiple cross -sections
iv. Volume and physical horizontal and vertical extent of anticipated saturated
source material mapped in plan -view and multiple cross -sections following
implementation of the approved closure option
v. Description of how the saturated ash is anticipated to affect the groundwater
concentrations overtime based upon modeling information
vi. Chemistry within waste boundary
1 The applicable standard or concentration for groundwater COIs would be the 2L standard, the IMAC
concentration or the BTV, whichever is greater. For unsaturated soil COIs the applicable standard is
the PSRG POG or BTV, whichever is greater.
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1. Table of analytical results, subdivided as follows:
1. Ash solid phase
2. Ash SPLP
3. Ash Leaching Environmental Assessment Framework (LEAF)
4. Soil (beneath ash)
5. Soil (beneath ash) SPLP
6. Ash pore water
2. Piper diagram(s) for ash pore water if additional pore water data
have become available since the piper diagrams were developed in
the CSA Updates. Otherwise, reference the location of the piper
diagrams that were presented in the CSA Update.
3. Ash pore water isoconcentration maps for each COI in plan -view or
use of alternative figures such as exceedance ratio maps showing the
combined ash porewater and surrounding areas and 2 or more cross
sections
vii. Other source material identified through the additional source area
assessments.
viii. Interim response actions conducted to date to remove or control source
material, if applicable
1. Source control conducted to date or planned to include but not
limited to excavation, dewatering, boundary control measures (e.g.
extraction wells), etc.
2. Source area stabilization conducted to date or planned (e.g. describe
dam safety, flood plain inundation issues, etc.)
b. Extent of constituent migration beyond the compliance boundary or waste boundary
(whatever is the point of compliance depending on whether the source area(s) are
covered by a permit) based upon groundwater data collected through June 2019:
i. Plan view map showing COI results (bubble inset at each seep location) for
groundwater, seeps and SWs. COI results presented are to be based on
consideration of geometric mean concentrations and/or time vs.
concentrations relationships or similar approach based on historical data
collected through June 2019.
ii. Table of analytical sampling results associated specifically with Source Area
1:
1. Soil, as applicable
2. Groundwater (per individual flow regime [e.g. shallow, deep,
bedrock)
3. Seeps (up-, side-, and down -gradient)
4. SW data (up-, side-, and down -gradient)
5. Sediment (up-, side-, and down -gradient)
iii. Piper diagram(s) for each groundwater flow regime, seeps, and other SWs
where the applicable water quality data is available.
C. COIs
List of COls and their maximum concentrations beyond the point of
compliance that require corrective action based on 2L/IMAC/background
exceedances:
1. Soil (unsaturated)
2. Groundwater
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3. other media if applicable
d. Isoconcentration maps, or use of alternative figures types such as exceedance ratio
maps, in plan -view and two or more cross sections for:
i. COls in unsaturated soil (defined as any COI in the sample being above POG
PSRG or approved background concentration in unsaturated soil)
ii. Horizontal and vertical extent of groundwater in need of restoration for each
COI identified for remediation in each groundwater flow regime (shallow,
deep, bedrock).
e. COI Distribution in Groundwater
i. Movement of conservative COls (e.g. boron, sulfate, chloride) from source to
receptor.
1. Describe whether plume is stable or expanding
1. Flow path wells and transect wells used to assess plume
behavior
2. Method(s) used to analyze plume behavior (should be
discussed and agreed upon with Regional Office prior to CAP
submittal)
ii. Distribution of non -conservative COls (e.g. Fe, Mn, Co, As, TI, etc.)
1. Discussion of site geochemical conditions that may affect COls
behavior in the groundwater system with details included in the
geochemical modeling report.
B. Receptors associated with Source Area 1
a. Map of surface waters (to include wetlands, pond, unnamed tributaries, seeps, etc.)
within %-mile of the waste boundary and hydraulically downgradient of Source Area 1
or known extent of contamination (whichever is greater).
i. Indicate on map all surface waters that are currently permitted as National
Pollution Discharge Elimination System (NPDES) outfalls, along with the
permitted outfall name and NPDES sample location
ii. Indicate on map all surface waters that are currently covered under a Special
Order by Consent
iii. For all surface waters shown, indicate stream classification and nearest
downstream supply intake, if applicable
iv. Indicate on map (footnote) and in report text whether SW samples have been
collected using Division approved protocols ("2L-2B" sampling protocols) to
evaluate whether contaminated groundwater is resulting in 2B violations;
include date(s) of 2L-2B sampling and antecedent rainfall
1. If 2L-2B sampling has been conducted, indicate location of all 2L-2B
sample collection points
2. If 2L-2B sampling has been conducted, indicate results of 2B
exceedances on map; also indicate which of those exceedances is a COI
for groundwater for Source Area 1
3. If 2L-2B sampling has not been conducted, explain why and indicate
whether it is being proposed and the proposed sample collection points
b. Map of all supply wells associated with Source Area 1 identified by receptor surveys and
per 130A-309.211(cl) (up-, side-, and down -gradient)
i. Indicate on map the results of the permanent water solution program
completed under House Bill 630 and show which well owners did and did not
accept alternative water
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ii. Provide analytical results table for the supply wells; indicate in table whether
each well was determined to be impacted or unimpacted by coal ash
iii. For each supply well determined to be unimpacted by coal ash, provide or
reference evidence that substantiates that position, including water level
measurement -based potentiometric mapping, piper diagrams, assessment of
well -specific geochemical conditions that are affecting certain COls, modeling,
etc. The evidence provided or referenced here will be used to review and
accept or deny Duke's determination that a given well is unimpacted by coal
ash.
c. Map of future groundwater use areas associated with Source Area 1
i. Indicate on map whether each parcel has or does not have access to alternative
water by referring to the figure provided in Section 6.B.b.i above.
ii. Indicate on map whether each parcel was modeled to be impacted or
unimpacted by coal ash now or in the future, or provide a written explanation
that off -site parcels will not be affected based on groundwater modeling
C. Human and Ecological Risks
D. Evaluation of Remedial Alternatives
All contents requested below for Section a. should be repeated for each remedial alternative
that is considered (i.e. Remedial Alternative 2, Remedial Alternative 3, etc.) as directed and
appropriate.
a. Remedial Alternative 1
i. Problem statement and remedial goals.
1. List of COls within each groundwater flow unit (shallow, deep,
bedrock) that will be corrected by this alternative
2. Concentration clean up goals for each of the COls identified in D. a. i.
1. above
ii. Conceptual model (i.e. simple description explaining how the proposed
source control/removal and corrective action will reduce COI concentrations
and protect human health and environment)
1. COls addressed
2. COls not addressed
3. For each COI not addressed by the proposed corrective action
describe how the constituent will be addressed.
iii. Predictive modeling
Robust predictive groundwater models have been developed for each coal
ash site subject to corrective action. These models will be used to evaluate
potential remedial options as needed. Preliminary detailed groundwater
modeling reports have been prepared consistent with NCDEQ's groundwater
modeling policy document and submitted to the Department. Final modeling
reports are to be prepared consistent with this format, adjusted to include
use of the models for corrective action planning and submitted as an
appendix to the CAPS.
iv. For remedial alternative 1, evaluate it using the following criteria:
1. Protection of human health and the environment
2. Compliance with applicable federal, state, and local regulations
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3. Long-term effectiveness and permanence
4. Reduction of toxicity, mobility, and volume
5. Short term effectiveness at minimizing impact on the environment
and local community
6. Technical and logistical feasibility
7. Time required to initiate
8. Predicted time required to meet remediation goals described in D. a.
i. 3. above
9. Cost
10. Community acceptance
E. Proposed remedial alternative(s) selected for the source area 1 and/or sub -areas of source
area 1.
Note that multiple corrective actions may be necessary to address different locations within
source area 1 or any of its sub -areas. This could involve "compartmentalizing" the source area
and describing the specific selected corrective actions for each "compartment."
a. Description of proposed remedial alternative and rationale for selection
i. Specific section of 02L .0106 being addressed by the proposed remedy [e.g.
02L .0106 (1) or (k)]
ii. Will a hybrid remedy consisting of more than one corrective action be used?
If so, describe.
iii. Will proposed remedy or hybrid remedy meet concentration cleanup goals
defined in D. a. i. 3. above?
iv. Treatability studies
1. Results of post-CSA Update treatability studies, if applicable
v. Additional site characterization needed to support the proposed remedy
1. Locations and specific testing, sampling, modeling, and (or) data
analysis
2. Schedule for data collection and reporting
b. Design details — Provide the following information at the conceptual design level
i. Process flow diagrams for all major components of proposed remedy
ii. Engineering designs with assumptions, calculations, specifications, etc.
iii. Permits needed for proposed remedy and approximate schedule for
obtaining them
iv. Schedule and approximate cost of implementation
v. Measures to ensure the health and safety of all persons on and off site
vi. Description of all other activities and notifications being conducted to ensure
compliance with 02L, CAMA, and other relevant laws and regulations
c. For 02L .0106 (1) CAP, provide requirements outlined in DWR's Monitored Natural
Attenuation for Inorganic Contaminants in Groundwater: Guidance for Developing
Corrective Action Plans Pursuant to NCAC 15A [02L] .0106(I).
d. For 02L .0106 (k) CAP, provide requirements outlined in 02L .0106 rule
e. Sampling and reporting
i. Proposed progress (i.e. "effectiveness") reports and schedule
ii. Proposed sampling and reporting plan during active remediation
iii. Proposed sampling and reporting plan after termination of active
remediation (if proposed)
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1. Decision metrics for termination of active remediation and start of
,'monitoring only' phase
A. Proposed wells for COI trend analysis
B. Proposed statistical method for trend analysis
f. Proposed interim activities prior to implementation
g. Contingency plan in case of insufficient remediation performance
i. Description of contingency plan
ii. Decision metrics (triggering events) for implementing contingency plan
7. PROFESSIONAL CERTIFICATIONS
Sealed and notarized professional statements of "true, accurate, and complete".
8. REFERENCES
9. TABLES
10. MAPS AND FIGURES — Note: Duke Energy proposes to adjust the figure requirements to allow for
greater focus on figures needed to provide the basis for the site -specific corrective action approaches and
alternate figures types such as exceedance ratio maps that can present multiple constituents on one
figure.
11. APPENDICES —See attached Summary
APPENDICES — Flow and Transport Modeling
For Flow model report content, refer to report titled 'Updated groundwater Flow and Transport
Modeling Report for Asheville Steam Electric Plant, Arden, NC (Ronald Falta and others, March
17, 2017). Also include the following:
• List of all model assumptions
• List all model limitations that affect output (including, for example, unconfirmed
boundary positions, unmodeled heterogeneities, scale of cell volume versus scale of well
observations, limited input data, limited data for calibration and calibration assessment,
etc.)
• List of variables for which sensitivity analyses were quantitatively presented
• Describe how model is being used in closure/corrective action design and review
For transport model report content, refer to report titled 'Updated groundwater Flow and
Transport Modeling Report for Asheville Steam Electric Plant, Arden, NC (Ronald Falta and others,
March 17, 2017). Also include the following:
• List of all model assumptions
• List all model limitations (including, for example, limitations of Kd, unconfirmed boundary
positions, unmodeled heterogeneities, scale of cell volume versus scale of well
observations, limited input data, limited data for calibration and calibration assessment,
etc.) that affect output
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• List of variables for which sensitivity analyses were quantitatively presented
• Describe how model is being used in closure/corrective action design and review
APPENDICES - Geochemical Modeling
For geochemical report content, refer to memorandum titled, 'Geochemical modeling of
constituent behavior at CAMA disposal sites' (Brian Powell, January 29, 2018) and memo titled
'Summary and Comments on Geochemical Modeling Outline with MNA Considerations (Bill
Deutsch, February 7, 2018). Also include the following:
• List of all model assumptions
• List all model limitations (including, for example, lack of pertinent data for points along
an individual flow path, if applicable, heterogeneities, limited input data, etc.) that affect
output
• List of variables for which sensitivity analyses were quantitatively presented
• How model is being used in closure/corrective action design
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Attachment 2
Supporting Rationale for Proposed Interpretation and Adjustments to the Corrective
Action Plan Content Guidance (NCDEQ April 2018)
January 2019
CAP Guidance Section*
Rationale for Proposed Adjustments
Executive Summary
. Added Executive Summary to provide a high-level
summary of the Corrective Action Plan's (CAP) conceptual
site model (CSM) and the site -specific corrective action
approach proposed based on the CSM.
1. INTRODUCTION
1.C.b.
• Deleted text referring to the Notice of Regulatory
Requirements (NORR). These NORR requirements are
focused on the Comprehensive Site Assessments (CSAs)
and are not directly relevant to the CAP.
LD
• Added text to clarify that the CAP will provide a general
written description of how these items were considered
during the CAP preparation process per 02L .0106(i). This
is also intended to clarify that the criteria provided in
Section 7.D.a.iv.1-10 will be used for evaluation and
selection of remedial alternatives in the CAPs.
1.E.b.
• Added text to clarify that only non -coal waste streams that
may affect the subsurface conditions at or proximate to coal
ash basins or coincident source areas will be included to
maintain focus on the Coal Ash Management Act
requirements.
2. RESPONSE TO COMPREHENSIVE SITE ASSESSMENT UPDATE COMMENTS
IN SUPPORT OF CAP DEVELOPMENT
2. and 2.B.
• The note at the top of the section clarifies how responses to
the NCDEQ CSA comment letters will be addressed in the
CAP to facilitate the NCDEQ's review. Modification to the
text in Section 2.B.a.&b. has been revised to reflect this
approach.
3. OVERVIEW OF SOURCE AREAS BEING PROPOSED FOR CORRECTIVE
ACTION
. Added a note that describes the role of ash basin decanting
and ash basin closure plans as source removal/control
methods that are linked to the groundwater corrective action
plan for each site. Duke Energy will add a discussion of the
source control measures (the approved Closure Plan) and
the benefits to groundwater restoration and integration into
the corrective action program.
3.A.
. Added reference to the NCDEQ letter providing the list of
sources for each site to be addressed in CAP.

Attachment 2
Supporting Rationale for Proposed Interpretation and Adjustments to the Corrective
Action Plan Content Guidance (NCDEQ April 2018)
January 2019
CAP Guidance Section*
Rationale for Proposed Adjustments
3.13.
• Revised text to reference NCDEQ letter providing list of
sources for each site that will be addressed in subsequent
and separate CSAs.
• Previously numbered items a, b, c are no longer needed due
to the clarification provided by the NCDEQ's letter and
were deleted.
4. SUMMARY OF BACKGROUND DETERMINATIONS
4.13.
• Added text to provide discussion of regional background
concentrations for similar geologic settings as context for
soil background Threshold Values (BTVs).
4.C.
• Added text to provide discussion of regional background
concentrations for similar geologic settings as context for
groundwater BTVs.
4.1).
• Revised text to indicate that referenced EPA values are
recommended "criteria". EPA Nationally Recommended
Water Quality Criteria for Aquatic Life & Human Health
(EPA NRWQC) have not been universally adopted under
15A NCAC 02B. Sample results will be compared to those
criteria found in 15A NCAC 02B .0211(11) with values for
EPA NRW C provided for reference.
SUMMARY OF POTENTIAL
RECEPTORS
• Removed this section and consolidated potential receptor
information into Section 6.B. This will avoid presenting
redundant information.
5. CONCEPTUAL SITE
MODEL (CSM) — New Section
• Placed CSM into a more prominent position in the guidance
document to emphasize the importance of the CSM to
support corrective action decision -making. All elements
from Section 6.A.b.i. were included along with additional
items to make the CSM more robust.
6. SOURCE AREA 1

Attachment 2
Supporting Rationale for Proposed Interpretation and Adjustments to the Corrective
Action Plan Content Guidance (NCDEQ April 2018)
January 2019
CAP Guidance Section*
Rationale for Proposed Adjustments
6. Opening Section
• Paragraph 1 - Deleted text referring to discussions with
Paragraphs
regional DWR office to identify source areas. This item
was resolved by NCDEQ letter identifying source areas.
These sources will be considered for corrective action based
on the results of the site assessments currently in progress.
• Paragraph 3- Edited text to identify water supply wells and
surface water features hydraulically downgradient relevant
to Source Area 1 to focus only on those areas that could
potentially be affected to facilitate the corrective action
preparation process. The CAP will provide justification for
selection of water supply wells and downgradient surface
water features relevant to each source area.
• Paragraph 4 - Added text to define constituents of Interest
(COIs) for corrective action. This is consistent with 15
NCAC 02L. 0106(e)(4) corrective action requirements to
address constituents with concentrations greater than 2L
applicable values at or beyond the compliance boundary.
This approach will focus the information presented and the
corrective action to the constituents exceeding the
applicable standard (2L/IMAC/BTV) at the relevant point
of compliance.
6.A.a
• Added text to reduce representing data previously provided
to NCDEQ with the intent of leaving more time to focus on
corrective action analysis.
6.A.a.v.
• Revised text to remove the reference to the calculation of
specific storage. Specific storage is a general aquifer
parameter that represents the amount of groundwater per
unit volume of a saturated formation that is lost or gained
from storage due to the compressibility of the mineral
framework that comprises the formation and the pore water
per unit change in head rather than being used to evaluate
COIs in groundwater. The groundwater flow and transport
model will estimate the COI concentrations over time for
the evaluation of remedial alternatives. This approach
provides a more meaningful representation of the
performance of the remedial alternatives over time
compared to a calculation of specific storage.
6.A.a.vi.1.
• Added Ash Leachate Environmental Assessment
Framework LEAF sample data.

Attachment 2
Supporting Rationale for Proposed Interpretation and Adjustments to the Corrective
Action Plan Content Guidance (NCDEQ April 2018)
January 2019
CAP Guidance Section*
Rationale for Proposed Adjustments
6.A.a.vi.3
• Added text to allow for figure preparation flexibility such as
the use of exceedance ratio maps and including the
surrounding area.
6.A.a.vii
• Revised text to indicate "other source material", if any, will
be addressed based on the results of the additional source
area assessments currently underway.
6.A.b.
• Added text to clarify that the discussion regarding the extent
of COIs will include data collected through June 2019. This
will provide Duke Energy with the needed time to reduce
site data and include it in the interpretation of site
conditions.
6.A.b.i.1-6.
• Removed text to the newly created Section 5 above to place
eater emphasis on the CSM.
6.A.b.11.
. Added text that COI results presented are to be based on
consideration of geometric mean concentrations and/or time
vs. concentrations relationships based on historical data
collected through June 2019. This approach will provide
more appropriate concentration results for corrective action
planning by eliminating anomalous or inconsistent data
likely associated with transient geochemical variations.
6.A.b.111.1.6.
• Eliminated table of analytical results for supply wells in this
section since the same information is requested in Section
B.b.ii. to eliminate redundant information.
6.A.c.1-11.
• Removed this section since very similar information is
requested in Section 6.D.a.i-ii which is more focused on
corrective action analysis.
6.A.d.ii.
• Added to text to clarify that isoconcentration maps will be
included for COIs identified for remediation.
6.A.e.
• Changed section title from Plume Characteristics to COI
Distribution in Groundwater to reflect the fact that not all
inorganic COIs behave as a "plume" and are often isolated
and/or transient due to geochemical conditions.
6.a.e.i.1.
• Revised text to say `stable' to `expanding' rather than
`moving' and (or) expanding since `moving' is very similar
to expanding. This wording is also consistent with NCDEQ
and USEPA MNA guidance concerning the description of
plume behavior.

Attachment 2
Supporting Rationale for Proposed Interpretation and Adjustments to the Corrective
Action Plan Content Guidance (NCDEQ April 2018)
January 2019
CAP Guidance Section*
Rationale for Proposed Adjustments
6.a.e.ii.1.
• Revised text to provide a general discussion of site
geochemical conditions in the body of the CAP recognizing
that the detailed geochemical items listed will be included
in the geochemical modeling report which will be presented
in the appendices.
6.B.a
• Revised text to clarify that only those surface waters that
are hydraulically downgradient that could be affected by
site -related COIs will be identified on the map to maintain
focus on those areas that may need to be addressed under
the CAP.
6.B.b.
• Revised to provide clarity regarding identification of water
supply wells.
6.D.a.i.1.
• Removed text regarding a 3-dimensional (3-D) map. A 3-D
block diagram figure will be included as part of the CSM.
6.D.a.iii.
• Removed this section on predictive modeling. Duke Energy
proposes to consolidate this section into the groundwater
modeling report that will be presented as an appendix to the
CAP. The groundwater modeling will be used to inform
corrective action decision -making.
6.E.b.
• Added text to indicate information requested will be
provided at conceptual design level.
6.E.b.iv.
Added "approximate" to costs since information will be at
conceptual level.
10. MAPS and FIGURES
• Added note that describes Duke Energy's approach for
figures to be included in the CAP with an emphasis on
making the CAP more manageable on a practical basis and
focusing on those figures necessary to support our
corrective action approach.
11. APPENDICES
• Added a general planned list of CAP appendices to clarify
what will be included in the CAP deliverables. The
appendices may be adjusted on a site -specific basis as
needed.
Notes
*If a section is not included in this table no changes were made to it.

Attachment 3
General List of Appendices for the Groundwater Corrective Action Plans for Duke Energy
Facilities*
January 2019
Appendix A Key Regulatory Correspondence
1) Approval of Provisional Background Threshold Values (September 1,
2017 and [Date] 2019)
2) Special Order by Consent
Appendix B
Comprehensive Site Assessment Update Report North Carolina
Department of Environmental Quality (NCDEQ) Review Comments
and Responses
1) Comprehensive Site Assessment Update NCDEQ Comment Letters
2) Duke Energy Response to Comments and Summary Table
3) NCDEQ Meeting Minutes
4) Additional Assessment Report(s) [including delineation of constituents
in soil, background evaluation, additional source areas, deep bedrock
assessment and pumping test report(s)]
Appendix C
Updated Comprehensive Analytical Data Table
Appendix D
HB 630 — Provision of Water Supply Completion Reports
Appendix E
Updated Human Health and Ecological Risk Assessments
Appendix F
Final Flow and Transport Model Reports
Appendix G
Final Geochemical Model Reports
Appendix H Monitored Natural Attenuation Report
Appendix I Interim Corrective Action Construction Drawings (as applicable)
Appendix J Surface Water Evaluation Report for Compliance with 2L (k) or (1)
*The above represents common items to be included in the Groundwater Corrective Action
Plans. The actual list will be tailored to each site's specific requirements as needed.

LEGEND
MONITORING WELLS_
y
•� T �
�
� - .
-
GWA-24S '•
GENERALIZED EXCEEDANCE 1.0 CONTOUR
AREAL EXTENT OF CONSTITUENTS OF INTEREST
' •
_
REPRESENTED BY NCAC 02L EXCEEDANCES
SELECTED SURFACE WATER SAMPLE LOCATIONS
ASH BASIN WASTE BOUNDARY
- - - ASH BASIN COMPLIANCE BOUNDARY
- - STATION BOUNDARY
DESIGNATED EFFLUENT CHANNEL
'�"
-
y,Constituent
=
Arsenic /L
Symbol
As
15A NCAC1
Standard
10
Barium /I_
Ba
700
Boron /I_
B
700
Chloride /L
Cl
250
Chromium /L
Cr
10
Man anese /L
Mn
50
Selenium /L
Se
20
•
Total Dissolved Solids m /L
TDS
500
STREAM (AMEC NRTR 2015)
MW-200S
WETLANDS (AMEC NRTR REPORT, 2015)
:, Cr: 1.1
K yi. GWAAS -' Mn: 1.3 t
00
B:1.4 ..:- �,`�•.�.�_._.�- [GWA-32S
WA-30S _ Mn: 3.2 s: 2.3lie
,.. \�(f n : 210
GWA-11 S, P.,r
-B: 1.9
a Cr:4.6 °" -
._.A]Mn:.1 ate CCR-08S
4. - MW-103S B:14.7
u ` Y GWA-21 S ;_ - -
n i As: 7.5
<, Mn: 4.5 : ,. CCR-05S B: 1.9 Cl: 1.6
, Cr: 1.5
CCR-04S
'� B: 11.5 B: 16.1 Cl: 1.0 � TDS: 1.8
CI: 1.6
Mn: 169
CI:1.3 TDS:2.0 TDS:1.1 AB-3S
/ TDS: 1.3 QJ B: 13.3
GWA-31S "
x GWA-19SA
a
y As: 1.0
_ �,.
Ba:1.0
Mn: 40.6
.. �, Se: 1.3
r
- GWA-10S ,
CI:1.6 CI:1.4 n: 16.61TDS:1.8
■ Mn:101 Mn:33.2
IA- 7S1.2�' � TDS:2.0 TDS: 1.8
CCR-02S
■ .'As:
1.4
i
B: 10.8
CI: 1.3
�Cr:
1.4
ASH BASIN
TDS: 1.5
GWA-18SA
Mn: 30
-r.
synTerra
CCR-01 S
(� DUKE
' ENERGY:
NOTES
1) Exceedance ratio is defined as the constituent concentration divided by the
selected comparative criteria (for example: [COI]/2L Standard).
2) Ratio numbers >1 indicate an exceedance of comparative criteria (2L, IMAC, BTV);
ratio numbers <1 indicate constituent concentrations within acceptable limits relative to
comparative criteria.
3) Posted data is from April 2018 (the most recent comprehensive validated
data set available).
4) Manganese (Mn) not contoured due to inconsistent distribution.
125 0 125 250 EXAMPLE MAP
GRAPHIC SCALE IN FEET EXCEEDANCE RATIOS -
148 RIVER STREET, SUITE 220 2L STAN DARD
GREENPHONE 64-421-9999LLE, SOUTH ROLINA29601 BELEWS CREEK STEAM STATION
PHONE [phone]
tttDUKE ENERGY CAROLINAS, LLC
DRAWNBY: IDATE:D1�15�2G19 B
PROJECT MANAGER: C. EADV ELEWS CREEK, NORTH CAROLINA
CHECKED BY: T. PLATING
PADuke Energy Prooress.1026\00 GIS BASE DATA\Belews Creek Steam Station\MapDocs\Misc\ExcRatioFigs\BC 2L Ex edanceRatio ExMap.mxd