Duke Energy letter to DEQ in response of DEQ letter 013120_20200304

fn DUKE
ENERGY.
March 4, 2020
Ms. Sheila C. Holman
Assistant Secretary for the Environment
North Carolina Dept. of Environmental Quality
1601 Mail Service Center
Raleigh, NC 27699-1601
Paul Draovitch
Senior Vice President
Environmental, Health & Safety
and Operations Support
526 S. Church Street
Mail Code: EC3XP
Charlotte, NC 28202
[phone]
RE: North Carolina Department of Environmental Quality Letter dated January 31, 2020,
Issues Related to Implementation of Closure Plans and Groundwater Corrective Action
Plans (OAPs)
Duke Energy is in receipt of your letter dated January 31, 2020 which identified several issues
"which require further consultation" related to implementation of Closure Plans and
Groundwater Corrective Action Plans (CAPS), some of which Duke Energy submitted to the
North Carolina Department of Environmental Quality (NCDEQ) on December 31, 2019. Duke
Energy understands that the NCDEQ would like to work with the company to reach a common
understanding on items identified in the letter and submits the information provided below to
clarify and further that understanding. Overall, the comments provided herein are intended to
move the focus towards implementing groundwater remediation in an efficient, expeditious
manner utilizing the extensive amount of environmental data collected at each site. Duke Energy
recognizes that proactive implementation of the CAPs is in the best interest of the environment.
Below, in bold/italic font, are the items listed in the above -referenced NCDEQ letter followed by
Duke Energy's response.
1. Implementation of CAPS: Proposals to streamline reviews and approvals necessary for
implementation of the CAPS to ensure that groundwater remediation is proceeding as safely
and expeditiously as practicable.
It is the objective of both the NCDEQ and Duke Energy to implement Corrective Action Plans
(where necessary) as expeditiously as possible. As outlined in the December 2019 settlement
agreement, Duke Energy has a 2029 deadline at three sites (Belews Creek, Marshall and
Roxboro), to bring groundwater within 2L standards at the geographic limitation. At the
remaining sites that do not have a 2029 deadline, prompt commencement of remedial activities is
also a key objective.
Duke Energy appreciates NCDEQ's prompt issuance of the approval to commence pilot tests at
five sites. As outlined in that approval letter dated February 10, 2020, Duke Energy will prepare
and submit pilot test work plans for review by the Department. In addition, Duke Energy will
also conduct quarterly update meetings or calls with the Department as needed. A similarly
prompt approval for future steps in the implementation process will be necessary to keep the
projects on schedule for timely implementation.

2. Post -closure monitoring and care: A process for determining which wells and parameters will
continue to be monitored, and the sampling frequency of such monitoring, as part of the post -
closure monitoring and care required by N.C. Gen. Stat. § 130A-309.214 or groundwater rules
set forth in ISA NCAC 02L.
Duke Energy's current and former coal-fired sites are likely the most extensively investigated
sites in the State, with assessment efforts exceeding those at most active and inactive hazardous
sites or Superfund sites. The amount of data collected through December 2019 is considerable
(Attachment 1). The data shows that a majority of constituent concentrations in groundwater are
stable or have decreasing trends.
Presently, all Duke Energy sites have an approved Interim Monitoring Plan (IMP) which
specifies the monitoring wells to be sampled (and frequency) along with which constituents are
to be analyzed. The recently submitted OAPs include an effectiveness monitoring program
(EMP) which is meant to bridge the gap until basin closure when the monitoring would revert to
post -closure monitoring. Separate from that, certain wells will be needed to determine how well
the groundwater extraction system (corrective action) is functioning. In many instances, these
separate monitoring systems overlap, are redundant (e.g. Sutton) and need to be optimized.
Duke Energy proposes to work with NCDEQ at the Corrective Action Plan approval stage to
optimize these separate sampling programs.
Optimization of the monitoring networks should be based on actual site data. Items to consider
include the following:
• Most existing site wells were installed for investigation purposes and, while they are appropriate
for assessment, they are not located for effective long-term monitoring purposes.
• Utilize monitoring wells appropriate for the scale of the site including all flow zone depths.
• Reduce "source area", side -gradient, and redundant background and down -gradient wells.
• Optimize the constituent list:
o Refine parameter list based on site data and COI management review process.
o Limit analysis of major ions for "charge balance" which tend not to change significantly
over time.
• Evaluate constituent and well lists periodically based on monitoring results:
o Discontinue monitoring for constituents and locations at wells that are non -detect (ND)
or consistently less than 50% COI criterion.
3. Completion of site assessment: Whether further site assessment is needed or whether
sufficient information is contained in the comprehensive site assessments to allow for the
preparation and implementation of the CAPS.
As stated above, the Duke Energy coal ash sites have a considerable amount of data for
groundwater and other media which has been collected since site assessment activities began in
2015. This data has been thoroughly evaluated that has resulted in a detailed understanding of
site conditions.
OA

Furthermore, much has changed since 2015 as a few sites have completed excavation, permanent
water solutions have been implemented and approved by NCDEQ at all sites, assessment results
indicate that there are no significant impacts to receptors at any site, 2L/2B assessments show no
impacts to surface water at sites where studies have been completed, and constituent transport is
limited to areas in the immediate vicinity of the ash basins. Considering this information, it is
appropriate to shift focus from refining assessment information to corrective action planning and
execution. For future CSAs associated with additional source areas, Duke Energy proposes that
we leverage existing site data where possible, complete assessment activities in the CSA phase,
and focus CAPs on remedy identification and design. (This suggested approach is in contrast to
the process followed for previous basin CAPs where the CAPs repeated much of the information
from the CSA phase.) We believe this approach will enable a more expeditious corrective action
program.
4. Periodic updating of groundwater modeling: A timeline for periodic updating of groundwater
modeling during the closure and post -closure process, and procedures for determining when
monitoring results indicate that such updating may be necessary.
The fate & transport models and geochemical models were, and continue to be, developed by
PhD modeling experts using industry -standard methods. The models are very well calibrated to
site conditions based on the extensive groundwater and chemical data collected to date.
For the six sites (Allen, Belews Creek, Cliffside, Marshall, Mayo and Roxboro) that submitted
updated CAPs at the end of December 2019, robust groundwater models have been developed
and validated. Hundreds of modeling simulations were run to evaluate the relative effectiveness
of postulated remedial approaches. The models have served that purpose well, and those results
were included in the CAPs. Duke Energy believes the best approach at this point is to focus on
implementing the remedies proposed in the CAPs. Once remediation has been implemented and
has been operational for an appropriate time period, the models can then be refined based on
actual site conditions.
For the remaining sites, Duke Energy will be submitting updated fate & transport models within
future updated CAPs.
5. Permitting: Strategies for ensuring that DEQ can approve necessary permits in a timely
manner to ensure that closure and corrective action are proceeding as safely and expeditiously
as practicable. For example, DEQ is considering potential mechanisms for expediting the
approval process for landfills proposed to be sited within the footprint of former
impoundments by including the groundwater and elevation monitoring data already available
at these sites.
The recent settlement includes provisions for accelerated permitting by expeditious review
(Settlement Paragraph #38). Both Duke Energy and NCDEQ mutually share the objective of ash
3

basin closure and groundwater remediation as safe and expeditiously as possible. As there are
multiple NCDEQ Divisions requiring reviews and approvals of the Closure Plans and CAPs, a
"typical" permitting process may not be effective in meeting our common goals. Duke Energy
suggests that NCDEQ establish a Coal Ash Permit Coordinator reporting to the appropriate level
within the Department. The role of this Coordinator would be to expedite permit approvals
throughout the various divisions and provide regular updates to Department management on
permit applications received as well as the review status and anticipated permit issuance dates.
6. Soil and groundwater background threshold values (BTVs --appropriate methodology for
determining BTVs)
Duke Energy is in the process of updating soil BTVs at Allen, Belews Creek, Cliffside, Marshall,
Mayo and Roxboro following the same methodology as completed in June 2019 for updating
groundwater BTVs. The methodology Duke Energy followed is consistent with EPA -approved
methodologies and the NCDEQ approved document Statistical Methods for Developing
Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities, dated
May 2017 and prepared by HDR, Inc. and SynTerra Corp. However, it appears Duke Energy
and DEQ differ with regards to evaluation of data set outliers, and, in the most recent review, the
NCDEQ removed certain data points without explanation.
As an example, NCDEQ removed the radium value of 11.14 pCi/L from the Marshall
background data set without explanation. This resulted in a decrease in background
concentration from 7pCi/L (Duke calculation) to 2.88 pCi/L (NCDEQ calculation) which results
in five additional deep bedrock wells exceeding the radium BTV.
The BTV approach submitted in 2019 by Duke Energy was carefully developed based on
multiple lines of technical evidence consistent with USEPA guidance. To resolve the matter,
Duke Energy proposes a meeting with DEQ technical staff in the near future to discuss and
address the details of outstanding BTV issues.
7. Remediation Strategy for Boron (...alternative remedial target for certain constituents at some
of these sites, including boron)
As mentioned previously, there is an abundance of data that has been collected for these sites.
The data clearly shows that the majority of the constituents of interest are limited to the area
directly downgradient of the basins. Evaluation of the data indicates that there are no identifiable
impacts to receptors (drinking water, surface water, etc.) and that the most common constituent
in groundwater above the 2L standard is Boron. Consequently, Boron becomes a driver for a
significant portion of the active groundwater corrective action. A review of the 2L standard for
Boron indicates that this value may be inappropriately low for driving corrective action
(particularly at a site with no receptors and anticipated deed restrictions on future groundwater
use). Therefore, Duke Energy proposes that the NCDEQ consider the application of a more -
El

suitable Boron remedial target (i.e. in line with EPA) when determining where active
remediation is required.
As described in detail in Attachment 2, when calculating the 2L standard for Boron, a relative
source contribution (RSC) factor of 0.1 was used. However, if a more scientifically supportable
RSC factor of 0.8 is used based on guidance from EPA (as described in Attachment 3), the 2L
standard for Boron would be 5,600 ug/1 compared to the present 2L standard of 700 ug/1.
The EPA has not established a Maximum Contaminant Level (MCL) for boron but has
established an adult drinking water lifetime health advisory of 5,000 ug/L for boron and a
regional screening level for residential tapwater at Superfund sites of 4,000 ug/l for Boron.
Apart from these two values, EPA has proposed a groundwater protection standard (GWPS) for
boron under the Federal CCR rule of 4,000 ug/11. EPA explains that this proposed standard is at
a concentration level "to which the human population could be exposed to on a daily basis
without an appreciable risk of deleterious effects over a lifetime".
Based on the EPA -generated values shown above for boron in drinking water, a remedial target
of 5,600 ug/L would be a realistic and appropriate remediation level for boron rather than 700
ug/l.
& Streamlined CAPS (...discuss whether streamlined site -specific CAPS)
Duke Energy understands that uncertainties associated with subsurface conditions in and around
the coal ash basins several years ago resulted in the CAP content guidance provided by the
NCDEQ. The six CAPS submitted to the NCDEQ on December 31, 2020 contained a combined
total of over 23,000 pages of technical information. Since the original versions of the CAP
content guidance were developed, Duke Energy has evaluated the extremely large amount of
multi -media data generated at each site and has developed a detailed understanding of site
conditions. We have confirmed that there is a consistent general Conceptual Site Model (CSM)
for sites in the Piedmont/Blue Ridge region that can be applied to all our stations in these
regions. Furthermore, Duke Energy believes the CSM combined with the extensive dataset
collected at each site now allows us to focus CSA reports and OAPs on what is important and
place emphasis on identifying the right corrective action strategy for each site and implementing
the approach in a more expeditious manner. We believe this approach is in the best interest of
the environment. Attachment 3 contains additional supporting information for adjusting the
CSA and CAP content at this time along with adjusted outlines for each. Duke Energy
recognizes that each site may have unique site -specific conditions that may cause a need to
adjust the CSA or CAP content.
For reference purposes, Duke Energy conducted a review of other non -Duke Energy NCDEQ-
approved CAPs in the state and found that on average that Duke Energy CAPs are 32 times
1 Federal Register -July 30, 2018
5

larger in page counts and 95 times larger in electronic file size compared to a similar sample size
(see Attachment 4). Even acknowledging that Duke Energy sites are generally larger sites, this
represents a significant disparity compared to other sites in the state. As stated in the paragraph
above, we respectfully request that the NCDEQ consider these adjustments of future CSA and
CAP content based on our increased understanding of site conditions and the opportunity to
accelerate corrective action implementation.
9. Geographic Limitation
Although not specifically noted in the NCDEQ letter dated January 31, 2020, the settlement
agreement dated December 31, 2019 includes paragraph #52 which specifies a `geographic
limitation' and states that active remediation will not be required in the area within 500 feet of
the waste boundary in addition to other conditions. Although this settlement is specific to the
Allen, Belews Creek, Cliffside, Marshall, Mayo and Roxboro sites, Duke Energy requests the
same conditions specified in paragraph #52 be applied to the remaining coal ash sites in North
Carolina. As the remaining eight sites are currently in the process of updating CSAs and/or
CAPs, it is imperative that Duke Energy receive timely guidance from the NCDEQ on the use of
the geographic limitation for all its coal ash facilities.
Duke Energy appreciates the opportunity to provide this information, and we welcome the
opportunity to further this discussion.
Sincer ly,
G•�
P 1 Draovitch
Senior Vice President
Environmental, Health & Safety and Operations Support
cc: Mr. Ed Sullivan — Duke Energy
Mr. Jim Wells — Duke Energy
Attachment list follows
2

Attachment 1— Summary of Coal Ash Management Assessment Activities for the Allen,
Asheville, Belews Creek, Buck, Cape Fear, Cliffside, Dan River, HF Lee, Marshall, Mayo,
Riverbend, Roxboro, Sutton, Weatherspoon Stations from 2015 through December 2019, Duke
Energy
Attachment 2 — Gradient Memorandum, "A Revised Drinking Water Standard for Boron Based
on a More Scientifically Supportable Relative Source Contribution Factor", January 23, 2020, by
A. Lewis
Attachment 3 — Updated Corrective Action Plan and Comprehensive Site Assessment Content
for Remaining Coal Ash Sites
Attachment 4 — Duke Energy CAP Documents Compared to Other NCDEQ Approved OAPs
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ATTACHMENT 2
Memorandum
to GRADIENT
To: Ed Sullivan, Duke Energy Date: January 23, 2020
From: Ari Lewis
Subject: A Revised Drinking Water Standard for Boron Based on a More Scientifically Supportable
Relative Source Contribution Factor
Overview
■ The North Carolina Department of Environmental Quality (NCDEQ) has established a 2L
groundwater quality standard for boron of 700 µgf L.
■ The current 2L standard for boron includes the application of a relative source contribution (RSC)
factor of 0.1 for inorganic compounds.
■ Based on available information on sources of boron other than drinking water, an RSC of 0.8 is
more supportable.
■ An RSC of 0.8 is consistent with the United States Environmental Protection Agency's (US EPA's)
assessment of lifetime health -based standards for boron in drinking water.
■ Using a more supportable RSC of 0.8, and keeping all other assumptions consistent with NCDEQ's
Standard Operating Procedures (SOPs) for deriving 2L standards, results in a revised 2L standard
for boron of 5,600 µg/L.
Derivation of the North Carolina 2L Standard for Boron
NCDEQ has established "groundwater quality standards for the protection of the groundwaters of the state"
(NCDEQ, 2013). Specifically, the standards are developed to be protective of humans consuming
groundwater as drinking water. The procedure for developing the 2L standard for non -carcinogens is
presented in "The Division of Water quality (DWQ) Standard Operating Procedure (SOP) for Reviewing
Groundwater Standards Established Pursuant to 15A NCAC 02L.0200" (NCDEQ, 2010). The equation
used to derive the 2L standard is presented below:
µg RfD ( mg ) x 1,000 (W-) x BW (kg) x RSC (unitless)
NC 2L standard �) = kg - day mg
L WC(d4
G:\Projects\218030_NAMAB\WorkingPiles\Boron 2L Memoi—dum_012319.docu
20 University Road, Cambridge, MA 02138 1617-395-5000 1 www.gradientcorp.com

ATTACHMENT 2
Where:
RfD = The reference dose is the chronic oral toxicity criterion established by US EPA's Integrated
Risk Information System (IRIS)
BW = An adult body weight of 70 kg
RSC = A relative source contribution factor of 0.1 for inorganics and 0.2 for organics
WC = An average water consumption rate of 2 liters/day
Using this equation, NCDEQ has developed a 2L standard for boron of 700 µg/L. This was derived using
the boron reference dose (RfD) from IRIS of 0.2 mg/kg-day, as well as other exposure -related inputs,
including an adult body weight of 70 kg, an average water consumption rate of 2 liters/day, and an RSC
factor of 0.1 (because boron is an inorganic constituent). The derivation of the boron -specific 2L standard
is presented below:
0.2 ( mg )x1,000 (") x 70 (kg) x 0.1
NC 2L boron standard = kg —day mg = 700 µg/L
2 (day)
Chemical -specific RSC for Boron
The RSC is an adjustment factor that accounts for the relative amount of a constituent that is allowed for
oral intake of drinking water, considering that the same chemical may be ingested from other sources (e.g.,
via the diet). US EPA explains that the RSC "is applied to the RfD to determine the maximum amount of
the RfD'apportioned' to drinking water" (US EPA, 2000). The RSC is important because some constituents
are largely ingested through consuming food, as opposed to drinking water, and therefore the general
population is already exposed to some level of the constituent before the addition of any exposure from
drinking water.
To account for the situation where a chemical might be present from non -drinking water, NCDEQ uses an
RSC of 0.1 to derive 2L standards for inorganic compounds. What this basically means is that the health -
protective 2L standards are developed assuming that 10% of a person's exposure to the constituent will
come from drinking water and 90% will come from other sources.
The application of an RSC is not unique to the 2L standard. US EPA has developed a procedure for RSC
application in their report, "Methodology for Deriving Ambient Water Quality Criteria for the Protection
of Human Health" (US EPA, 2000). Overall, US EPA's approach applies a default RSC of 0.2 if
information on possible other exposures to the constituent is inadequate. However, there is an explicit
provision to allow for the use of a higher RSC when it can be demonstrated that drinking water would be
the primary source of exposure and non -drinking water sources would comprise only a small fraction of the
RfD (e.g., US EPA, 2008). US EPA specifically states that an RSC of 80% as a ceiling and 20% as a floor
should be used (US EPA, 2000).
According to dietary intake data from the third National Health and Nutrition Examination Survey, mean
intake of boron in US individuals 6 years and older is 1.15 mg/day (Trumbo, 2001). This is less than 10%
of the RfD (14 mg/day for a 70 kg adult), which means that an adult could get 90% of their boron from
water and still be exposed to a safe level of boron (i.e., a level of boron below the RfD). Using the more
scientifically supportable RSC of 0.9 (90%) instead of the 0.1 (10%) default value for inorganics results in
a revised 2L standard for boron of 6,300 µg/L.
GRADIENT

ATTACHMENT 2
The revised RSC of 0.9 is based on the assumption that dietary boron is the only non -drinking water source
of boron. While the diet is expected to be the most significant source of boron exposure, the RSC could be
conservatively set to 0.8, which is consistent with US EPA guidance (see below for more details). Setting
the RSC to 0.8 would result in a 2L standard for boron of 5,600 µg/L:
0.2 ( mg ) x 1,000 (11g) x 70 (kg) x 0.8
NC 2L boron standard = kg — day L mg = 5,600 µg/L
2 (day)
US EPA's Lifetime Drinking Water Advisory Level for Boron
US EPA has specifically considered an appropriate RSC application when developing a drinking water
criterion for boron. In the absence of a Maximum Contaminant Level, in 2008, US EPA developed a
lifetime health advisory level for boron using an RSC of 0.8 (US EPA, 2008). Aside from the RSC, the
only difference between the lifetime health advisory level US EPA developed and the 2L standard is that
US EPA considered a pregnant woman with a weight of 67 kg instead of the generic adult body weight of
70 kg. As shown below, the lifetime health advisory developed by US EPA using the RSC of 0.8 was
5,400 µg/L (rounded).
US EPA Lifetime HelathAdvisory =
0.2 ( mg ) x 1,000 (U'g) x 67 (kg) x 0.8
kg —day mg = 5,400 µg/L
2 (day)
In applying the RSC of 0.8 to the derivation of the lifetime health advisory level, US EPA (2008, p. 34)
provided the following justification:
The relative source contribution is determined using the Exposure Decision Tree approach
described in the Methodology for Deriving Ambient Water Quality Criteria for the
Protection of Human Health (USEPA, 2000). The target population is pregnant women
because the in utero developmental endpoint is the most sensitive. Available data are
considered adequate to describe anticipated exposures. The RSC subtraction calculation
method is considered appropriate since there are no other existing health -based numeric
criteria for boron. Dietary sources represent the main background intake for boron (IOM,
2001). IOM (2001) reported a mean boron intake value of 1.0 mg/day from food sources
for women of childbearing age and pregnant women. The background dietary intake value,
when adjusted to the recommended 67 kg body weight for women of childbearing age,
corresponds to a daily intake value of 0.015 mg/kg/day. When subtracted from the
Reference Dose (RfD) of 0.2 mg/kg/day, 0.185 mg/kg/day remains. This latter value
represents approximately 93 percent of the RfD. Therefore, the RSC ceiling value of 80
percent is applied, consistent with both the 2000 Human Health Methodology and past
drinking water program regulatory practice.
GRADIENT

ATTACHMENT 2
Conclusion
An RSC is used to account for constituent exposure from non -drinking water sources when setting a
drinking water standard protective of human health. The application of a default RSC of 0.1 for the
derivation of the 2L standard for boron is not supported by information on boron exposure from non -
drinking water sources. The main source of boron is the diet; for an average adult, the mean daily intake
of boron is 1.15 mg/day. This intake is less than 10% of the safe level of boron exposure, as reflected in
the Rf) of 14 mg/day (based on an Rf) of 0.2 mg/kg-day for a 70 kg adult). If non -drinking water sources
of exposure account for only 10% of the safe dose, this means that 90% of exposure could come from
drinking water and the RSC could be as high as 0.9. However, an RSC of 0.8 would be more conservative
by accounting for dietary boron as well as other miscellaneous exposures, and would be consistent with US
EPA's derivation of a health -based drinking water level for boron. Using the more scientifically supportable
RSC of 0.8, in conjunction with the other factors specified in NCDEQ's SOP, would result in a revised 2L
standard for boron of 5,600 µg/L.
GRADIENT

ATTACHMENT 2
References
North Carolina Dept. of Environmental Quality (NCDEQ). 2010. "The Division of Water Quality (DWQ)
Standard Operating Procedure (SOP) for Reviewing Groundwater Standards Established Pursuant to 15A
NCAC 02L .0200." Division of Water Quality (DWQ). 5p., September.
North Carolina Dept. of Environmental Quality (NCDEQ). 2013. "Groundwater Quality Standards." 15A
NCAC 02L .0202. 5p.
Trumbo, P; Yates, AA; Schlicker, S; Poos, M. 2001. "Dietary reference intakes: Vitamin A, vitamin K,
arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and
zinc." J. Am. Diet. Assoc. 101(3):294-301.
US EPA. 2000. "Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human
Health (2000) (Final)." Office of Water, Office of Science and Technology, EPA-822-B-00-004, 185p.,
October.
US EPA. 2008. "Drinking Water Health Advisory for Boron." Office of Water, EPA 822-R-08-013, 65p.,
May.
GRADIENT

ATTACHMENT 3
UPDATED CORRECTIVE ACTION PLAN AND COMPREHENSIVE SITE ASSESSMENT CONTENT
FOR REMAINING COAL ASH SITES
Introduction
The purpose of this document is to provide the North Carolina Department of Environmental Quality
(NCDEQ) with Duke Energy's rationale and proposed approach for adjusting future groundwater Corrective
Action Plans (CAPs) submitted for Duke Energy ash basins and additional source areas. Duke Energy
believes there are multiple reasons for adjusting the CAP and Comprehensive Site Assessment (CSA)
content at this time including:
Advancement in the Project Lifecycle — The original extensive CAP and CSA requirements were
understandable at the time because site conditions were not well known and constituent of interest
(COI) distribution was not well understood. Today, extensive amounts of data have been collected
and analyzed at each site and subsurface conditions are well understood. A summary of the data
collected at each site is presented in Table 1. Data collected to date indicate that the Conceptual
Site Models for valley fill ash basins in the Piedmont are consistent in their hydraulic behavior. As a
result, COI distribution is generally consistent across all sites.
2. Potential risks have been significantly mitigated —The extensive site assessment data
collected along with substantial risk mitigation activities completed at each site combine to
reduce or eliminate potential or perceived risks at each site. These risk mitigation items include:
■ Resolution regarding the excavation of coal ash at each site has been achieved
■ Groundwater protection programs for each site have been or soon will be completed
• No significant impacts to potential human or ecological receptors have been identified based
on risk assessments completed to date
■ There have been no surface water impacts above state 2B standards in the 2U2B studies
completed to date
■ COI transport is generally limited to areas directly around ash basins
■ Assessment data for the remaining sites in need of CAPs and CSAs indicate that they are
generally less impacted than six sites for which CAPs were submitted on December 31,
2019 (e.g., see groundwater data for the Riverbend and Dan River stations)
3. Updated CAP and CSA formats allow for reduced time to corrective action implementation —
By focusing the CAPs on areas requiring attention, appropriate remedies can be developed and
implemented more rapidly which is beneficial to the environment and concerned stakeholders.
Two attachments are presented herein. Attachment 1 presents an updated version of the CAP content
outline. Attachment 2 presents an updated version of the CSA outline.
Duke Energy looks forward to working with the NCDEQ on completing the remaining CSA and CAPs.

ATTACHMENT 3A
Updated Corrective Action Plan Content for
Duke Energy Coal Ash Facilities and Additional Source Areas
Best professional judgement must be applied to generate the Corrective Action Plan (CAP) documents.
EXECUTIVE SUMMARY
1. INTRODUCTION
A. Background
B. Purpose and Scope
C. Regulatory Basis for Closure and Corrective Action
D. Facility Description (summary from Comprehensive Site Assessment [CSA])
a. Location and history of land use.
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.).
2. OVERVIEW OF SOURCE AREAS BEING PROPOSED FOR CORRECTIVE ACTION
A. Map showing the boundary of each source area proposed for corrective action.
3. 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). A discussion of regional
background concentrations for similar geologic settings may be provided as context for
Background Threshold Values (BTVs).
C. Table of background concentrations for groundwater. Include the appropriate 2UIMAC
Standards. 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 sediment sample locations.

4. 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. CSM elements will include:
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. Subsurface heterogeneities and other potential factors affecting flow and
transport including geochemical conditions.
iii. The role of matrix diffusion in/out of bedrock (bedrock porosity) on constituent
transport where appropriate.
vii. The effects of naturally occurring constituents in site groundwater.
b. 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 summary of the human health and ecological risk assessment results.
5. SOURCE AREA(s)
Contents listed in Section 5 should be tailored to areas requiring corrective action based on the
CSA results.
Maps prepared for Source Area should be large scale. typically 1" = 150 to 200 ft. and include
topographic contour intervals at 5 to 10 feet to reduce electronic file size and allow for electronic
file manageability.
The following references to COIs for corrective action are based on the CO! management
approach developed in coordination with the NCDEQ in 2019.
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. 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.
b. Extent of constituent migration beyond the geographic limitation 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 agreed upon
timeframes with the NCDEQ:
i. Plan view map showing COI results (bubble inset at each seep location) for
groundwater, seeps, and surface water using the COI management approach
developed with the DEQ in 2019.
ii. Table of analytical sampling results associated with Source Area(s):
1. Soil, as applicable
2. Groundwater (per individual flow regime (e.g. shallow, deep, bedrock)
3. Seeps (up-, side-, and down -gradient)
4. Surface water (up-, side-, and down -gradient)
5. Sediment (up-, side-, and down -gradient)
c. Isoconcentration maps, or cross sections for:
i. Horizontal and vertical extent of groundwater in need of restoration for COls
identified for remediation in each groundwater flow regime (e.g., shallow,
deep, bedrock).
d. COI Distribution in Groundwater
i. Distribution of COls in groundwater based on the COI management program
developed with the NCDEQ in 2019.
1. Describe whether plume is stable or expanding based on plume
stability analysis.
2. Discussion of site geochemical conditions that may affect Cols
behavior in the groundwater system with details included in the
geochemical modeling report.
B. Summary of Human and Ecological Risks
C. Evaluation of Remedial Alternatives
a. Remedial Alternative
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
ii. Simple description explaining how the proposed source control/removal and
corrective action will reduce COI concentrations and protect human health and
environment. Include how models were used to inform decision -making.

iii. For remedial alternative, evaluate aiternative(s) using the following criteria:
1. Protection of human health and the environment
2. Compliance with applicable federal, state, and local regulations
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
9. Cost
10. Community acceptance
D. Proposed remedial alternative(s) selected for the source area(s)
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)]
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.
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]. 0 1 06(l).
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).

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.
6. PROFESSIONAL CERTIFICATIONS
Sealed and notarized professional statements of "true, accurate, and complete"
7. REFERENCES
8. TABLES
9. MAPS AND FIGURES
10. APPENDICES

ATTACHMENT 3B
Comprehensive Site Assessment Outline for Remaining Duke Energy Ash Basins and
Additional Source Areas
The updated CSA outline proposed below for the remaining Duke Energy ash basins and additional
sources areas is presented below. This outline is taken from the NCDEQ Division of Water Resources
guidance document titled "Guidelines for the Investigation and Remediation of Soil and Groundwater
Contamination", 2017. Duke Energy believes this format provides the appropriate level of detail needed
to complete representative CSAs and is consistent with NCDEQ guidance. The details of each CSA
submitted can be adjusted based on site -specific conditions.
■ TITLE PAGE
■ EXECUTIVE SUMMARY
■ TABLE OF CONTENTS
o Site History and Source Characterization
o Receptor Information
o Regional Geology and Hydrogeology
o Site Geology and Hydrogeology
o Soil and Sediment Sampling Results
o Groundwater and Surface Water Sampling Results
o Hydrogeological Investigation
o Groundwater Modeling Results
o Discussion
o Conclusions and Recommendations
o Maps and Figures
o Tables
o Appendices

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