NC0001422_Appdx B - CSA Comments_20200814

Corrective Action Plan Update August 2020
L.V. Sutton Energy Complex
APPENDIX B
SynTerra
COMPREHENSIVE SITE ASSESSMENT UPDATE
REPORT REVIEW COMMENTS AND RESPONSES

'.0
Water Resources
Environmental Quality
June 11, 2018
Paul Draovitch
Senior Vice President
Environmental, Health & Safety
Duke Energy
526 South Church Street
Mail Code EC3XP
Charlotte, North Carolina 28202
Subject: 2018 Comprehensive Site Assessment Update Comments
L. V. Sutton Energy Complex
Dear Mr. Draovitch:
ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Interim Director
On January 31, 2018, the North Carolina Department of Environmental Quality's (DEQ's) Division of
Water Resources (DWR) received the Comprehensive Site Assessment (CSA) Update for the subject
facility. Based on the review conducted to date, the DWR has concluded that sufficient information
has been provided in the report to allow preparation of the Corrective Action Plan (CAP); however,
there are data gaps that must be addressed prior to, or in conjunction with, preparation of an approvable
CAP.
As described in the attached itemized list of CSA Update comments (Attachment 1), additional data
and/or data analysis will be needed to address data gaps, complete evaluation of exposure pathways,
predict time and direction of contaminant transport, and ultimately refine remedial design. The
assessment of all primary and secondary source areas (including, but not limited to, impoundments,
cinder storage areas, coal piles, and contaminated soils) must be included in the CAP, or in a CAP
amendment. The DWR expects that information collected regarding the source areas will be used to
formulate the CAP recommendations. For source areas where this may not be possible or areas where
pollutants may be hydraulically isolated, please contact me to discuss.
In an email dated April 18, 2018, Duke Energy proposed a CAP submittal date of January 31, 2019.
However, as you are aware, Duke Energy and the DEQ are currently discussing revisions to the CAP
deadlines and the frlal revised date for CAP submittal will be communicated to Duke Energy in a
separate correspondence.
An overview of CSA Update data gaps includes the following:
0 The distribution of constituents of interest related to the coal ash impoundments and other
primary sources (i.e. Former Ash Disposal Area) does not clearly delineate exceedances of
15A NCAC 2L standards above the site -specific background levels which could suggest
commingling of the contaminant plumes.
-5"P°"Nothing Campams: -_,
State of North Carolina I Environmental Quality I Division of Water Resources
Water Quality Regional Operations Section
1636 Mail Service Center I Raleigh, North Carolina 27699-1636
919-707-9129

The characterization of other primary and secondary sources other than impoundments that
contribute to the groundwater plumes is inadequate.
As detailed more fully in the attached document, additional data gaps remain concerning
characterization of impacts from coal ash at the facility.
The data gaps related to the site assessment at the facility, including those related to primary and
secondary sources other than impoundments, may limit the cleanup remedy and site management
strategies for a source area. The lack of a well -documented interpretation of the existing data, or
missing data that the DEQ believes will be necessary to support proposed corrective action, may limit
DEQ's ability to approve certain corrective action measures [e.g. 15A NCAC 02L .0106(1)]. For
example, monitored natural attenuation cannot be approved for source areas where surface water
samples have not been collected (but could be collected) and that demonstrate the groundwater
discharge does not result in exceedances of 15A NCAC 2B .0200 regulatory standards.
Please refer to the letter to Duke Energy dated May 14, 2018, for approved background threshold
values developed for the facility as part of the CSA Update.
Duke Energy should contact the Wilmington Regional Office to initiate the scheduling of a meeting
between DWR and Duke Energy's technical staff (including contractors) to discuss data gaps in greater
detail. Promoting regular dialogue in a small group format assists in addressing questions and
problems that may come up during the development of the CAP, and better ensures that Duke Energy
is meeting DWR's expectations.
If you have any questions, please feel free to contact me at [phone]. Please contact Geoff
Kegley (Wilmington Regional Office) at [phone] to discuss any additional questions regarding
the CSA Update data gaps in more detail.
Sincerely,
r
,ton Ri ard, Section Chief
Division of Water Resources
Attachment: L. V. Sutton Energy Complex CSA Update Comments
cc: WIRO WQROS Regional Office Supervisor
WQROS Central File Copy

Comments for L.V. Sutton Enemy Complex Comprehensive Site Assessment Update
Submitted January 31, 2018
Delineation of Groundwater Contamination
Questions remain concerning the accuracy of the delineation of horizontal extent of groundwater
contamination, which is a requirement of Coal Ash Management Act (CAMA) and 15A NCAC
02L .0106. The Corrective Action Plan (CAP) shall include updated maps and data summary that
address the following:
There is an effluent discharge canal located between the 1971 Ash basin and the Former
Ash Disposal Area (FADA) and adjacent former coal stockpile area. This discharge canal
may act as a hydraulic divide for shallow groundwater.to some extent, but there is likely
some potential that the plume from the 1971 ash basin is impacting this downgradient area
in the lower surficial aquifer (and therefore commingling of the contaminant plumes.) This
interpretation is not depicted on the submitted isoconcentration maps and cross -sections
submitted in the updated Comprehensive Site Assessment (CSA). Furthermore, the
contaminant plume has not been fully delineated south of the FADA. Further assessment
is needed in the FADA and in the former coal stockpile area.
All of the Coal Combustion Residual (CCR) data should be incorporated as part of the site
assessment and CAP.
Provide an interpretation as to how the geochemical conditions affect or control the
distribution of Constituents of Interest (COIs) with site specific data (COI concentrations
vs. geochemical parameter levels, identified with well IDs.)
Groundwater Flow, Contaminant Flow and Transport, Geochemical Modeling
• Continue evaluation of the groundwater flow system with respect to the large and dynamic
changes currently impacting - the flow system and how it may affect any proposed CAP.
(i.e. groundwater extraction system impacts, supply well pumping, ash excavation
removing the hydraulic head that was previously present in the ash basins, reduction in the
recharge area from the construction of the lined CCR landfill and from the increased
recharge from expanding neighboring sand quarry.)
• Groundwater flow, contaminant flow and transport modeling, geochemical modeling (and
the additional hydrous ferric hydroxide (HFO) and hydrous aluminum oxide (HAO)
sampling, as proposed), need to be performed/updated and submitted with the CAP.
• All COIs should be modeled unless a rationale for not doing so is provided.
Other Potential Primgg and SecoAdary Sources
As discussedpreviously, other primary and secondary sources must be assessed regarding impacts
to groundwater. Sources contributing to groundwater contamination associated with the
impoundments (commingled) must be assessed and the results incorporated into the CAP. Sources
that have impacted, or have the potential to impact groundwater (contaminated soils, stockpiles,
etc.,) that are not known or believed to have commingled with the areas impacted by the
impoundment may be assessed separately in accordance with a schedule approved by the
Department. Additional information needed includes the following:
• Soil contamination should be delineated to either site -specific background threshold values
(BTVs) or Protection of Groundwater (POG) Preliminary Soil Remediation Goals (PSRGs)
Page 1 of 2

levels, whichever are higher. If appropriate, use the equation provided in the PSRG table
to establish a POG PSRG for a constituent with 02L standard that does not have one.
• Provide plan view maps and cross -sections (where applicable) to demonstrate that soil
contamination (POG PSRGs or BTVs, whichever are higher) has been vertically and
horizontally delineated
Maps. Figures and Tables
• Because of the large changes at the facility and surrounding area impacting the
groundwater flow system (mentioned above), all isoconcentration maps should be updated
with latest complete groundwater sampling events (including CCR wells) and be presented
in the CAP.
• All BTVs that were approved (May 14, 2018 letter, and any subsequent updates) should be
incorporated throughout the site assessment, isoconcentration maps and forthcoming CAP.
02L/02B Surface Water Sam lin
Collection of surface water samples to evaluate impacts from contaminated groundwater is
necessary to understand the impacts associated with the migration of contaminates from the
groundwater system. Failure to adequately characterize known and potential impacts to surface
waters from the groundwater will affect the corrective actions strategies that can be proposed and
ultimately considered for approval by the department. Comments include the following:
• Additional surface water sampling is needed to complete the site assessment and to
evaluate Monitored Natural Attenuation as a possibility for corrective action (assess
potential near bank impacts from groundwater discharge to the west and south of the basins,
and the FADA/former coal stockpile area.) A surface water evaluation plan was submitted
by Duke Energy on April 25, 2018 and approved on May 10, 2018 with one minor change.
The agreed upon evaluation must be completed in accordance with the guidelines, dated
October 31, 2017, and included in the CAP.
Receptors
• Provide an updated status of the surrounding private water supply wells within the 0.5-mile
radius. Include any additional sampling that has been performed and the current status of
providing an alternative water supply, to include any additional efforts to contact non-
responsive properties.
Page 2 of 2

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
There is an effluent discharge canal
Duke Energy submitted a work plan to assess COIs in
Appendix M
located between the 1971 Ash basin
groundwater and soil in the FADA and former coal pile area
CAP Section 5.6
and the Former Ash Disposal Area
(FCPA) on August 31, 2018. The North Carolina Department of
(FADA) and adjacent former coal
Environmental Quality (NCDEQ) approved the work plan in a
stockpile area. This discharge canal
letter dated October 11, 2018.
may act as a hydraulic divide for
Assessment of the FADA and FCPA took place in February
shallow groundwater to some extent,
and July of 2019. Eight monitoring wells were installed in the
but there is likely some potential that
FADA in February 2019 and ten wells were installed in the
the plume from the 1971 ash basin
FCPA in July 2019.
impacting this downgradient area in
the lower surficial aquifer (and
Results of the FADA and FCPA assessment are included in
therefore commingling of the
CAP Update Appendix M and CAP Update Section 5.6. The
contaminant plumes.) This
contaminant plume has now been fully delineated south of the
interpretation is not depicted on the
FADA and FCPA. Both areas are identified as additional
submitted isoconcentration maps and
sources of COIs to groundwater. Constituents of interest
cross -sections submitted in the
(COIs) pertaining to the FADA and FCPA are arsenic, boron,
updated Comprehensive Site
molybdenum, strontium, and vanadium. Those five COIs are
Assessment (CSA). Furthermore, the
evaluated for corrective action in Section 5.7 and 5.8 in the
contaminant plume has not been fully
CAP Update.
delineated south of the FADA.
Further assessment is needed in the
FADA and in the former coal
stockpile area.
Page 1

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
All of the Coal Combustion Residual
All CCR data available at the time of CAP Update (August
CCR wells at the Site pertain
(CCR) data should be incorporated as
2020) preparation has been incorporated to the CAP dataset.
to the ash basins (Source Area
part of the site assessment and CAP.
The lower confidence limit (LCL95) and central tendency value
1).
(CTV) analysis included all CCR results.
Data is summarized in Tables
The CCR wells located on the western side of the ash basins
5-1, 5-4, and 5-8.
are the only wells available downgradient of the ash basins.
Data is presented on Figures
All of the CCR wells downgradient of the ash basins are
5-7a through 5-14b.
recommended to be sampled as part of the post -excavation
effectiveness monitoring program (EMP).
CCR wells recommended to
be sample under the EMP are
listed on Table 5-14 and
depicted on Figure 5-32.
Provide an interpretation as to how
The updated geochemical modeling report (CAP Update
Site geochemical conditions
the geochemical conditions affect or
Appendix G) includes a robust interpretation of Site
are evaluated in CAP Update
control the distribution of
geochemical conditions and how they may affect or control the
Appendix G
Constituents of Interest (COIs) with
distribution of COIs in groundwater downgradient of the
Geochemical conditions are
site -specific data (COI concentrations
Site's source areas.
summarized in CAP Update
vs. geochemical parameter levels,
Sections 5.1.4.2 and 5.6.4.2.
identified with well IDs.)
Page 2

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
Continue evaluation of the
The groundwater flow system has changed significantly due to
The updated flow and
groundwater flow system with
source removal and other dynamic Site changes. An updated
transport models are included
respect to the large and dynamic
March 2020 water level map is included as Figure 4-1.
in CAP Update Appendix F.
changes currently impacting the flow
The updated Flow and Transport modeling report (CAP
Flow and transport model
system and how it may affect any
Update Appendix F) includes a post -excavation calibrated
predictions are used
proposed CAP. (i.e., groundwater
model. This 2020 update to the Flow and Transport model
throughout the CAP Update
extraction system impacts, supply
evaluates the dynamic changes at the Site. Noteworthy
to evaluate potential remedial
well pumping, ash excavation
conclusions of that evaluation include:
alternatives.
removing the hydraulic head that was
previously present in the ash basins,
• Since closure, the groundwater flow direction has
A Site -wide water level map
reduction in the recharge area from
returned to natural conditions with flow predominantly
is included as Figure 4-1 and
the construction of the lined CCR
to the southwest, toward the cooling pond and the Cape
Flow and Transport
landfill and from the increased
Fear River.
calibrated flow direction
recharge from expanding neighboring
. Groundwater discharge to the cooling pond limits the
figures are included as
sand quarry.)
q rY•)
extent of COI migration to the west from the ash basins.
Figures 4-3a and 4-3b.
Groundwater discharge to the Cape Fear River limits the
extent of COI migration to the southwest of the FADA
and coal pile.
. Due to flow reversal, nearby public and private drinking
water wells and wellhead protection areas are no longer
located downgradient of the ash basins.
Page 3

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
Groundwater flow, contaminant flow
The Flow and Transport and geochemical models have been
The updated flow and
and transport modeling, geochemical
updated to reflect post -excavation conditions. Conservative
transport models are included
modeling (and the additional hydrous
assumptions of post -excavation conditions were used for areas
in CAP Update Appendix F.
ferric hydroxide (HFO) and hydrous
where a limited post -excavation dataset is available.
The updated geochemical
aluminum oxide (HAO) sampling, as
The geochemical evaluation includes the HFO/HAO samples
model is included in CAP
proposed), need to be
that have been collected at the Site. That evaluation concluded
Update Appendix G.
performed/updated and submitted
with the CAP.
that sufficient HFO/HAO samples are available to update the
Predictions from both models
geochemical model.
are used throughout the CAP
Update to evaluate potential
remedial alternatives.
Page 4

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
All COIs should be modeled unless a
The Flow and Transport predictive model evaluated the
The updated flow and
rationale for not doing so is provided.
current and future distribution of arsenic, boron, and
transport models are included
selenium. The Flow and Transport model typically models
in CAP Update Appendix F.
conservative, mobile constituents such as boron and sulfate to
The updated geochemical
predict the maximum extent of COIs pertaining to the Site
model is included in CAP
source areas. Arsenic and selenium (non -conservative or
Update Appendix G.
variably reactive COIs) were modeled to predict the extent of
these less mobile constituents in groundwater downgradient
Predictions from both models
of the source areas.
are used throughout the CAP
Update to evaluate potential
The COI Management Approach presented in Section 5.0 of
remedial alternatives.
the CAP Update was used to determine which COIs are in
need of corrective action at the Site.
The geochemical model addressed the COIs identified in the
outcome of the COI Management Approach (CAP Update
Section 5.1 and 5.6). Additional COIs were also selected to
support the geochemical evaluation.
Page 5

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
Soil contamination should be
The CAP Update evaluated soil samples as recommended by
Soil samples pertaining to
delineated to either Site -specific
the department. Where applicable standards were not
Source Area 1 are evaluated
background threshold values (BTVs)
available, POG PSRGs were calculated for COIs which have a
in CAP Update Section
or Protection of Groundwater (POG)
02L standard but do not have a POG PSRG.
5.1.2.1.
Preliminary Soil Remediation Goals
Soil samples pertaining to
(PSRGs) levels, whichever are higher.
Source Area 2 are evaluated
If appropriate, use the equation
in CAP Update Section
provided in the PSRG table to
5.6.2.1 and Appendix M.
establish a POG PSRG fora
constituent with 02L standard that
does not have one.
Page 6

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
Because of the large changes at the
As directed by the Department, a statistically representative
The LCL95/CTV datasets are
facility and surrounding area
dataset (LCL95/CTV) was calculated to evaluate COI
included as Tables 5-4
impacting the groundwater flow
distribution in groundwater at the Site for corrective action
(Source Area 1) and 5-12
system (mentioned above), all
purposes.
(Source Area 2). Methods for
isoconcentration maps should be
The COI Management Approach developed by Duke Energy
calculating the dataset are
updated with latest complete
and the NCDEQ was used to identify COIs for mapping in the
included as Appendix H.
groundwater sampling events
CAP Update.
Isoconcentration maps for
(including CCR wells) and be
presented in the CAP.
The LCL95/CTV dataset results are presented on
Source Area 1 are included as
isoconcentration maps and cross sections for CON in need of
CAP Update Figures 5-7a
corrective action as determined by the COI Management
through 5-11b.
Approach.
Isoconcentration maps for
Source Area 2 are included as
CAP Update Figures 5-24a
through 5-25b. Additional
isoconcentration maps for
SA2 are presented and
discussed in Appendix M.
Page 7

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
All BTVs that were approved (May 14,
2020 updated BTVs were submitted to the department in the
Updated BTVs are included
2018 letter, and any subsequent
report Updated Background Threshold Values for Constituent
on CAP Update Tables 3-1
updates) should be incorporated
Concentrations in Groundwater (SynTerra, 2020a). The updated
and 3-2.
throughout the site assessment,
groundwater BTVs were calculated using data collected
The updated BTVs are
isoconcentration maps and
through September 2019. Updated BTVs were calculated in
referenced in text, tables, and
forthcoming CAP.
accordance with the guidance and statistical evaluation
figures within the CAP
methodologies agreed upon by Duke Energy and NCDEQ.
Update.
Approval of the updated BTVs is pending.
Page 8

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
Additional surface water sampling is
The Surface Water Evaluation Report for current conditions
The approved current
needed to complete the site
was submitted to the department on January 17, 2020. The
conditions surface water
assessment and to evaluate Monitored
department approved the report in a letter dated June 18, 2020
evaluation report is included
Natural Attenuation as a possibility
with minor comments.
in Appendix K.
for corrective action (assess potential
A future conditions surface water evaluation was completed as
The future conditions surface
near bank impacts from groundwater
part of the CAP Update and is included as Appendix K.
water evaluation report is
discharge to the west and south of the
included in Appendix K.
basins, and the FADA/former coal
stockpile area.) A surface water
evaluation plan was submitted by
Duke Energy on April 25, 2018 and
approved on May 10, 2018 with one
minor change. The agreed upon
evaluation must be completed in
accordance with the guidelines, dated
October 31, 2017, and included in the
CAP.
Page 9

Appendix B: Comprehensive Site Assessment Update Report Review Comments and Responses
Corrective Action Plan Update
Duke Energy Progress, LLC - L.V. Sutton Energy Complex
gust 2020
SynTerra
Sutton CSA Update Comments
CAP Update Section(s)
WRO Comment
Duke Energy Response
where Comments are
Addressed
Provide an updated status of the
Documentation describing completion of the permanent
Compliance with HB 630 and
surrounding private water supply
alternate water provision under CAMA was submitted to the
the relevant NCDEQ
wells within the 0.5-mile radius.
Department on August 10, 2018.
correspondence is included as
Include any additional sampling that
In a letter dated October 12 2018, the department confirmed
CAP Update Appendix D.
has been performed and the current
that Duke Energy had satisfied all requirements under House
status of providing and alternative
Bill 630.
water supply, to include any
additional efforts to contact non-
responsive properties.
Note:
1) This document lists all WRO comments for the Sutton CSA Update Report. The letter dated June 11, 2018 and the attached comments to the letter
are a condensed version of this comprehensive document.
Page 10