NC0001422_Appdx F - F_T Model_20200814

Corrective Action Plan Update August 2020
L.V. Sutton Energy Complex
APPENDIX F
SynTerra
UPDATED GROUNDWATER FLOW AND TRANSPORT
MODELING REPORT

UPDATED GROUNDWATER FLOW AND TRANSPORT
MODELING REPORT
FOR
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
AUGUST 2020
PREPARED FOR
DUKE
ENERGY
PROGRESS
DUKE ENERGY PROGRESS, LLC
INVESTIGATORS
RONALD W. FALTA, PH.D. - FALTA ENVIRONMENTAL, LLC
REGINA GRAZIANO, M.S. - SYNTERRA CORPORATION

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
EXECUTIVE SUMMARY
This groundwater flow and transport model report provides basic model development
information and simulations of the effects attributed to closure actions and
groundwater corrective actions for the Sutton Energy Complex (Sutton, Plant, or Site).
The Site is owned and operated by Duke Energy Progress, LLC (Duke Energy) and is
located near Wilmington, New Hanover County, North Carolina. Model simulations
were developed using flow and transport models MODFLOW and MT3DMS. A
numerical model was developed to evaluate transport of inorganic constituents of
interest (COIs) in the vicinity of the source areas at the Site. Source areas include the
1971 ash basin, the 1984 ash basin, the former process area (FPA), the former ash
disposal area (FADA), and the former coal pile area (FCPA). At the time of model
calibration, coal ash had been removed from the 1971 ash basin and 1984 ash basin.
Excavation of the ash basins was complete by July 2019. Excavation of the ash in the
FPA is complete as of April 2020. Excavation of the FADA began in 2019, and was
completed in June 2020. Coal has not been stored on -Site since 2015.
Numerical simulations of groundwater flow and transport have been calibrated to pre -
excavation conditions and post -excavation conditions. The calibrated model was used
to evaluate monitored natural attenuation (MNA), a nine extraction well system
followed by MNA, and pump and treat system. An additional model evaluated soil
excavation within the 1984 ash. The current flow and transport model and report is an
update of a previous model developed by SynTerra in conjunction with Falta
Environmental, LLC and Frx Partners (SynTerra, 2018b). These models simulate non -
reactive transport of COIs where adsorption of the COIs to solids is approximated using
a linear equilibrium Kd approach.
The Site is currently a natural gas -fired electricity -generating facility in operation since
2013. Facility structures associated with current power production are located primarily
in the south central portion of the Site. The northern and southern portions of the Site
are primarily undeveloped areas containing small sand hills, pine woods, and brush
(Figure 1-1).
The Site encompasses 3,300 acres along the Cape Fear River northwest the City of
Wilmington. The Plant became operational in 1954 and eventually included three coal-
fired boilers. Coal combustion residuals (CCRs) were originally stored in the former ash
disposal area (FADA) located just north of the FCPA. The FADA is located south of the
1971 ash basin, south of the cooling water effluent canal. It is believed that ash might
have been sluiced to this area from approximately 1954 to 1972.
Page ES-1

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
In 1971, an 1,100-acre cooling pond known as Lake Sutton was built along with an
unlined ash basin called the 1971 ash basin (old ash basin). The cooling pond, is located
west of the Site, between the Cape Fear River and source areas (1971 basin, 1984 basin,
FPA, FADA, and FCPA). The 1971 ash basin had an outfall to the cooling pond that
operated from 1971 to 1984 when the new 1984 basin was put into operation. Discharge
from the 1971 ash basin to the cooling pond ceased at that time however, an emergency
outfall remained for periods of heavy rain. The emergency outfall was rarely used. The
cooling pond is a National Pollutant Discharge Elimination System (NPDES)-permitted
wastewater treatment unit. As of early 2015, the cooling pond has also been classified as
waters of the state (WOS). The cooling pond has been regulated as both WOS and a
NPDES-permitted wastewater treatment unit since 2015. This updated report will refer
to this Site feature as the cooling pond. The 1971 ash basin was constructed by
excavation below the water table to create earthen dike surrounding the basin.
In 1984, the 1984 ash basin was built to the north of the 1971 basin with a 12 inch thick
clay liner above the water table. The 1984 basin is hydraulically connected to the 1971
ash basin and had an outfall 004 located on the west side of the basin that discharged to
the cooling pond (or via underground pipe to outfall 001) as managed by Site
personnel.
The FPA, adjacent to the southeast corner of the 1971 ash basin, was a small settling
basin that was used in the 1970's to sluice waters before discharging to the 1971 basin.
The FPA was subsequently filled with solids, including CCRs.
The FCPA is located south of the FADA, west of the power plant near the Cape Fear
River. Coal was stockpiled in the area prior to use on -Site.
The Site is located in the Coastal Plain Physiographic Province of North Carolina which
includes surficial sands that are underlain by the Peedee Formation. It has been
determined that the Peedee Formation is affected by saltwater intrusion with naturally
occurring boron concentrations greater than the North Carolina Administrative Code
(NCAC), Title 15A, Subchapter 02L, Groundwater Classification and Standards (02L)
standard (SynTerra, 2018). The water table has low hydraulic gradients at the Site and
has been affected by source and ash pore water removal, operation of the interim
remedial action groundwater extraction system, water supply wells (both on -Site and
off -Site), and changing conditions at the off -site sand mines east of the Site.
As an interim remedial action, Duke Energy installed a system of nine -groundwater
extraction wells along the eastern property boundary. The primary objective of the
groundwater extraction system was to prevent migration of constituents in
Page ES-2

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
groundwater from the 1971 ash basin off -Site beyond the eastern property boundary.
The extracted groundwater is treated in an on -site treatment facility for NPDES
parameters and discharged to the Cape Fear River at Outfall 001 under the NPDES
permit.
The predictive simulations presented herein related to closure action and groundwater
corrective action are not intended to represent final detailed excavated closure of source
areas or corrective action designs. These simulations use current closure designs
developed by Geosyntec and are subject to change as the closure plans are finalized
(Geosyntec 2017a,b,c, 2019, 2020). The simulations are intended to show the key
characteristics of groundwater flow and mobile constituent transport that are expected
to result from the closure actions and corrective actions. Completion dates for each of
the excavated source areas are:
• 1971 ash basin - excavation complete July2019
• 1984 ash basin - excavation complete July 2019
• Former process area (FPA) - excavation complete April 2020
• Former ash disposal area (FADA) - excavation complete June 2020
• Former coal pile area (FCPA) - coal was removed by 2015
The 1971 ash basin was excavated (dredged) below the water table approximately 40
feet below original grade. The 1984 basin was excavated approximately to the original
ground surface. Discharge from the basins to the Cape Fear River via Outfall 001 is
currently permitted by the North Carolina Department of Environmental Quality
(NCDEQ) Division of Water Resources (DWR) under National Pollutant Discharge
Elimination System (NPDES) Permit NC0001422.
Constituents of interest (COIs) have been detected at concentrations greater than North
Carolina Administrative Code (NCAC), Title 15A, Subchapter 02L, Groundwater
Classification and Standards (02L) / Interim Maximum Allowable Concentrations
(IMACs) or background threshold values (BTV), whichever is greater, along the western
compliance boundary, north of the 1984 ash basin, in limited areas just beyond the
northwest corner of the 1984 basin, southeast of the 1971 ash basin and FPA, and
southwest of the FADA and FCPA.
Boron, and selenium were the COIs selected to evaluate performance of the closure
actions and corrective actions. Transport of arsenic was also considered in the analysis
of transport from unsaturated soils in the 1984 basin area. These constituents are
Page ES-3

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
present beyond the compliance boundary and exhibit plume characteristics. Boron is
relatively unreactive with subsurface solids and is readily transported and therefore is a
reasonable indicator of the maximum extent of COIs transported in groundwater
derived from the ash basins, FADA, FPC, and/or the FCPA.
Transport of less mobile constituents (i.e., arsenic, selenium) is controlled by chemical
reactions affecting sorption. Because the transport model uses a constant sorption
partion coefficient (Kd) it is unable to directly simulate the effect of changing
geochemical conditions. However, the Ka values selected for selenium (and arsenic in
the 1984 basin unsaturated soils analysis) in the transport model fall near the bottom of
values predicted by the geochemical model (SynTerra, 2020, Appendix G). Since lower
Kd values correspond to higher mobility, these transport simulations can be considered
conservative for arsenic and selenium in the sense that these COIs are not likely to
become more mobile than is assumed in the transport models. Geochemical conditions
at the Site are expected to become more strongly oxidizing over time (SynTerra, 2020,
Appendix G). As this occurs, arsenic and selenium are expected to form the less mobile,
more strongly sorbing species Se(VI) and As(V).
The flow models were calibrated in stages starting with the pre -excavation model (1971-
2017) and then the post -excavation model (2017-2019). Major physical changes occurred
at the site between 2016 and 2019, including excavation of the ash basins, construction
of the lined landfill, and installation and operation of nine extraction wells along the
eastern Site boundary.
Three potential future corrective action model simulations were used to predict future
COI distributions. The model scenarios used the post -excavation calibrated model as an
initial condition and considered three corrective action options: MNA alone, a
combination a nine extraction well system and MNA, and a pump and treat system.
MNA is when the nine extraction well system is turned off after the FADA and FPA
have been excavated. The second corrective action includes continuing to operate the
nine extraction well system for five years after the FADA and FPA were excavated,
followed by MNA in the year 2025. At that time, termination of the groundwater
extraction system under these conditions is allowed under Subchapter 02L .0106(m).
The third correction action includes a pump and treat system of 51 extraction wells and
33 infiltration wells running for approximately 30 years after the FADA and FPA are
excavated. The first two corrective action simulations extend approximately 700 years
into the future Figures ES-1a and ES-1b show predicted boron and selenium
concentrations 10 years and 700 years (20 years for selenium in Figure ES-1b) in the
future for a case with MNA alone (top panels), and for a case with five years of
Page ES-4

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
operation of the nine extraction well system followed by MNA (bottom panels). A
comparison of all three corrective actions approximately 30 years after the FADA and
FPA have been excavated (2050) are shown in Figures ES-2a and ES-2b) showing
boron, and selenium concentrations.
The compliance boundary used to evaluate the performance of the excavation closure as
well as the corrective action simulation is established by 15A NCAC 02L .0107 as 500
feet from the waste boundary or at the property boundary, whichever is closer to the
source. An exception to this rule occurs at the Site. The Site's cooling pond, an NPDES
permitted waste unit, defines the western compliance boundary. While the cooling
pond is considered waters of the State, it is also a permitted waste unit. The simulations
are intended to show the key characteristics of groundwater flow and mobile
constituent transport that are expected to result from the closure actions and corrective
actions.
The current distribution of boron in the surficial flow zones adjacent to the ash basins
resulted from hydrologic and mass loading conditions during operation of the 1971 and
1984 ash basins. These conditions changed as the ash was regraded and removed
during closure construction, with the construction of the lined landfill, and with
operation of the nine extraction wells. The groundwater flow direction in the vicinity of
the basins shifted from east to the west toward the cooling pond.
The surficial flow zone is relatively thick at the Site and the maximum extent of COIs is
typically greater in the upper surficial and lower surficial flow zones than in the upper
and lower Peedee flow zones. As part of the CSA Update, evidence was presented to
prove that the COIs occurring in the Peedee flow zones is naturally occurring due to sea
water intrusion. NCDEQ concurred with this conclusion. The Peedee flow zones are not
evaluated for corrective action.
Model simulations predict that the COI distribution will be similar under MNA and the
nine extraction well system operation followed by MNA (Figures ES-1a and ES-1b).
After the excavation of the source areas, the model predicts boron at concentrations
greater than the 02L standard beyond the compliance boundary along parts of the
eastern boundary where the nine extraction wells have a hydraulic control; along the
western boundary of the Site where groundwater under the former 1984 basin
discharges to the cooling pond; and south under the former 1971 basin and the FADA.
A small area of boron, with a maximum concentration of approximately 1,400 µg/L,
persists on the southern edge of the former 1971 basin and under the FADA until
approximately year 2390. The 02L standard for boron is 700 micrograms per liter (µg/L).
Page ES-5

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
While some boron persists above the 02L standard in this location, the predicted
concentration is well below the 4,000 µg/L tap water regional screening level (RSL)
(USEPA, 2020). At the time of CAP Update preparation, NCDEQ is currently reviewing
a revised 02L standard of 4,000 µg/L for boron. Furthermore, this area of predicted
persistent boron occurs in hydraulic stagnation zone that is present in the steady-state
flow model that was used for this simulation. The steady-state flow assumption does
not consider the short and long-term transient flows that will occur in response to
weather and climate variations over the several hundred year simulation. These flow
transients would be expected to result in additional mixing in the stagnation zone,
resulting in dilution of the boron there.
Selenium concentrations in both the MNA and the nine extraction well system followed
by MNA simulations are predicted to be greater than the 02L standard beyond the
compliance boundary west of the northern corner of the former 1984 basin to the
cooling pond. The model predicts the time to reach 02L compliance for selenium is
around year 2040 for both. The 02L standard for selenium is 20 micrograms per liter
(µg/L). COI concentrations shown under the cooling pond do not represent surface
water concentrations in the cooling pond; they represent conditions in the surficial flow
zones beneath the current and future cooling pond.
The pump and treat simulation consists of 51 extraction wells and 33 clean -water
infiltration wells running for approximately 30 years within the 1984 ash basin
footprint, FADA footprint, and FCPA footprint. Each pumping well has a pumping rate
of approximately 50 gpm. The 51 extraction wells remove water at a total rate of 3.6
million gallons per day (gpd) and the 33 infiltration wells add water at a total of rate 2.4
million gpd. The pump and treat simulation predicts that after 30 years of remediation
boron concentrations will be greater than the 02L standard beyond the compliance
boundary in three areas: a small area east-northeast of the former 1984 ash basin, a
small area west of the 1984 ash basin, and to the south of the former 1971 ash basin,
within the FADA footprint. A comparison of the three potential corrective action COI
simulations approximately 30 years after the FADA and FPA have been excavated can
be found in Figures ES-2a and ES-2b.
The second model is used to evaluate the effects of leaving unsaturated soil in place in
the 1984 basin in accordance with the Excavation Soil Sampling Plan (Duke Energy,
2018) This model used Synthetic Precipitation Leaching Protocol (SPLP) concentration
data from soil samples collected after excavation within the 1984 basin to assign
concentration values to the unsaturated soils. A simulation was performed where the
initial COI concentrations were zero everywhere except in the unsaturated soils in the
Page ES-6

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
1984 basin. This modeling approach shows the future COI contribution from these soils
to groundwater in the area. The results indicate that the COI concentrations in the
unsaturated soils remaining in the 1984 basin do not affect groundwater concentrations
near the compliance boundary in the future (Figures ES-3a through ES-3c). By itself, the
mass of constituents released from this soil would not result in concentrations greater
than 02L standards at the compliance boundary. Therefore, excavation of this material
would be expected to have little practical benefit in reducing future constituent
concentrations in the groundwater at or beyond the compliance boundary.
Page ES-7

APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 700 YEARS AFTER EXCAVATION
MNA
MNA
♦ AI�
. �I
I
L p
■ fi*
■ i
rl
F�
' 3 `� ,��.. i � -
..
•�' _ar � gyp,. £?: ,�v4. ��* -
APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 700 YEARS AFTER EXCAVATION
CORRECTIVE ACTION FOLLOWED BY MNA
CORRECTIVE ACTION FOLLOWED BY MNA
Y
♦ ♦
♦
.5
'
a a
e 1 �•.
LEGEND
NOTES:
GRAPHIC SCALE
990 0 990 1,980
BORON 700-4,000 Ng/L
1. ALL BOUNDARIES ARE APPROXIMATE.
_ ASH BASIN COMPLIANCE
2. BORON IS NATURALLY OCCURRING IN
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE:05/31/2020
BOUNDARY
REPRESENT DNINITHEOMODEL.
DUKE
ASH BASIN WASTE BOUNDARY
3. AERIAL PHOTOGRAPHY OBTAINED
FROM TERRA SERVER 17,
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
FORMER ASH DISPOSAL AREA
2019. IMAGE COLLECTED APRIL PRIL 4,2019.
ENERGY
_
BOUNDARY
4. DRAWING HAS BEEN SET WITH
PROGRESS
PROJECT MANAGER: B. WYLIE
www.synterracorp.com
PROJECTION OF NORTH CAROLINA
PLANE COORDINATE SYSTEM
FIGURE ES -la
-- FORMER COAL PILE AREA
RIPS 3200 (NAD 198TE
3).
— FORMER PROCESS AREA
COMPARISON OF SIMULATED BORON CONCENTRATIONS
ONSITE LANDFILL BOUNDARY
FLOW AND TRANSPORT MODELING REPORT
ONSITE LANDFILL COMPLIANCE
L.V. SUTTON ENERGY COMPLEX
BOUNDARY
WILMINGTON, NORTH CAROLINA
-- SAND MINES

APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 20 YEARS AFTER EXCAVATION
MNA
MNA
.:; r
�NIN
Al
APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 20 YEARS AFTER EXCAVATION
CORRECTIVE ACTION FOLLOWED BY MNA
CORRECTIVE ACTION FOLLOWED BY MNA
• '"
•
.A -a
♦
•
• �.
`
r--
•� t
LEGEND
NOTES:
—J
GRAPHIC SCALE
990 0 990 1,980
SELENIUM 20 - 139 Ng/L
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
ASH BASIN COMPLIANCE
- •
2. AERIAL PHOTOGRAPHY OBTAINED
FROM TERRA SERVER ON JUNE 17,
2019. IMAGE COLLECTED APRIL 4, 2019.
s Terra
, •
DRAWN BY: R. KIEKHAEFER DATE: 05/31/2020
DUKE
BOUNDARY
3. DRAWING HAS BEEN SET WITH A
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
PROJECTION OF NORT H CAROLINA
STATE PLANE COORDINATE SYSTEM
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
FORMER ASH DISPOSAL AREA
PIPS 3200 (NAD 1983).
PROJECT MANAGER: B. WYLIE
_
BOUNDARY
PROGRESS
www.synterracorp.com
FIGURE ES -lb
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
COMPARISON OF SIMULATED
• ONSITE LANDFILL BOUNDARY
SELENIUM CONCENTRATIONS
FLOW AND TRANSPORT MODELING REPORT
_ ONSITE LANDFILL COMPLIANCE
L.V. SUTTON ENERGY COMPLEX
BOUNDARY
WILMINGTON, NORTH CAROLINA
-- SAND MINES

APPROXIMATELY 30 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
MNA
NINE EXTRACTION WELLS FOLLOWED BY MNA
•
•
19
► !
tea, i �.
�---•
APPROXIMATELY 30 YEARS AFTER EXCAVATION
LEGEND
PUMP AND TREAT
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
BORON 700 - 4,000 pg/L
`
ASH BASIN COMPLIANCE BOUNDARY
♦
ASH BASIN WASTE BOUNDARY
— FORMER ASH DISPOSAL AREA BOUNDARY
-- FORMER COAL PILE AREA
FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
�•.�
SAND MINES
Ism
NOTES:
GRAPHIC SCALE
990 0 990 1,980
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE MODEL.
synTerra
DRAWN BY: R. KIEKHAEFER DATE: 05/31/2020
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
DUKE
COLLECTED APRIL 4, 2019.
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
ENERGY
APPROVED BY. B. WYLIE DATE: 07/29/2020
PROGRESS
PROJECT MANAGER: B. WYLIE
www.synterracorp.com
FIGURE ES-2a
COMPARISON OF CORRECTIVE ACTION SIMULATED BORON CONCENTRATIONS APPROXIMATELY 30 YEARS AFTER
SOURCE EXCAVATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

APPROXIMATELY 30 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
MNA
NINE EXTRACTION WELLS FOLLOWED BY MNA
.000
r i
r i
APPROXIMATELY 30 YEARS AFTER EXCAVATION
LEGEND
PUMP AND TREAT
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
SELENIUM 20 - 139 pg/L
A
ASH BASIN COMPLIANCE BOUNDARY
A
A ♦
ASH BASIN WASTE BOUNDARY
—FORMER ASH DISPOSALAREA BOUNDARY
A •
-- FORMER COAL PILE AREA
�
- FORMER PROCESS AREA
,. A
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
i
r
NOTES:=J
GRAPHIC SCALE
990 0 990 1,980
1. ALL BOUNDARIES ARE APPROXIMATE.
2. SIMULATED SELENIUM CONCENTRATIONS DO NOT EXCEED 20 Ng/LAFTER 20 YEARS IN ANY OF
THE THREE SIMULATIONS.
synTerra
J,
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/31/2020
(� DUKE
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
4. DRAWING HAS BEEN SET WITH PROJECTION OF NORTH CAROLINA STATE PLANE
ENERGY
APPROVEDDATE: 07/29/2020
COORDINATE SYSTEM FIPS 3200 (NAD 1983).PROJECT
MANAGER: B. WYLIE
PROGRESS
www.synterracorp.com
FIGURE ES-2b
COMPARISON OF CORRECTIVE ACTION SIMULATED SELENIUM CONCENTRATIONS APPROXIMATELY 30 YEARS AFTER
SOURCE EXCAVATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

APPROXIMATELY 5 YEARS AFTER EXCAVATION
APPROXIMATELY 10 YEARS AFTER EXCAVATION
•• • •
•• •
•
e. _.. ... . _.. .. ,...__ •
APPROXIMATELY 20 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
Ilk
LEGEND
NOTES:
J
GRAPHIC SCALE
990 0 990 1,980
• SAMPLE LOCATION
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
BORON 700 - 4,000 Ng/L
2. SIMULATED BORON 20 AND 30 YEARS
S) T�1 ra
DRAWN BY: R. KIEKHAEFER DATE: 06/03/2020
AFTER EXCAVATION WAS NOT PRESENT
ABOVE 700 Ng/L
(� DUKE
_ ASH BASIN COMPLIANCE
BOUNDARY
3. AERIAL PHOTOGRAPHY OBTAINED
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
FROM TERRA SERVER ON JUNE 17,
2019. IMAGE COLLECTED APRIL 4, 2019.
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
ASH DISPOSAL AREA
4. DRAWING HAS BEEN SET WITH
PROGRESS
www.synterracorp.com
_FORMER
PROJECTION OF NORTH CAROLINA
BOUNDARY
STATE PLANE COORDINATE SYSTEM
FIGURE ES-3a
PIPS 3200 (NAD 1983).
-- FORMER COAL PILE AREA
COMPARISON OF SIMULATED BORON CONCENTRATIONS FROM
— FORMER PROCESS AREA
THE POTENTIAL BENEFIT OF SOIL EXCAVATION IN THE 1984 ASH
ONSITE LANDFILL BOUNDARY
BASIN MODEL
FLOW AND TRANSPORT MODELING REPORT
ONSITE LANDFILL COMPLIANCE
BOUNDARY
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
-- SAND MINES

APPROXIMATELY 5 YEARS AFTER EXCAVATION
APPROXIMATELY 10 YEARS AFTER EXCAVATION
• • • ,
• • • ,
APPROXIMATELY 20 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
••• •• �;
i•• •• AIIA
•
•
xft-
LEGEND
e
NOTES:=J
GRAPHIC SCALE
ARSENIC 14 - 100 Ng/L
975 o 978 7s50
1. ALL BOUNDARIES ARE APPROXIMATE.
ARSENIC > 100 Ng/L
Terra
(IN FEET)
2. AERIAL PHOTOGRAPHY OBTAINED
DRAWN BY: R. KIEKHAEFER DATE: 06/03/2020
• SAMPLE LOCATION
FROM TERRA SERVER ON JUNE 17,
2019. IMAGE COLLECTED APRIL 4, 2019.
DUKE
- ASH BASIN COMPLIANCE
BOUNDARY
3. DRAWING HAS BEEN SET WITH A
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
PROJECTION OF NORTHCAROLINA
STATE PLANE COORDINATE SYSTEM
COORDINATESYSTEEM
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
PIPS 3200(NAD 1983).
PROJECT MANAGER: B. WYLIE
_FORMERASH DISPOSALAREA
PROGRESS
www.synterracorp.com
BOUNDARY
FIGURE ES-3b
-- FORMER COAL PILE AREA
COMPARISON OF SIMULATED ARSENIC CONCENTRATIONS FROM
—FORMER PROCESS AREA
THE POTENTIAL BENEFIT OF SOIL EXCAVATION IN THE 1984 ASH
ONSITE LANDFILL BOUNDARY
BASIN MODEL
ONSITE LANDFILL COMPLIANCE
FLOW AND TRANSPORT MODELING REPORT
BOUNDARY
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
--SAND MINES

APPROXIMATELY 5 YEARS AFTER EXCAVATION
APPROXIMATELY 10 YEARS AFTER EXCAVATION
•=...�
, r
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••• •• � ♦yam �
••• •• 4
•• • ♦
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APPROXIMATELY 20 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
NOTES:
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GRAPHIC SCALE
LEGEND
990 0 990 1,980
• SAMPLE LOCATION
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
SELENIUM 20-139Ng/L
2. AERIAL PHOTOGRAPHY OBTAINED
FROM TERRASERVER ON JUNE 17,
s ynTerra
,•
2019. IMAGE COLLECTED APRIL 4, 2019.
DRAWN BY: R. KIEKHAEFER DATE:06/03/2020
(� DUKE
_ ASH BASIN COMPLIANCE
BOUNDARY
3. DRAWING HAS BEEN SET WITH
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
PROJECTION OF NORTH CAROLTE SYSTEM
SYSTEM
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
FPST3 00(NAD 11983)INATE
PROJECT MANAGER: B. WYLIE
_FORMER ASH DISPOSAL AREA
PROGRESS
www.synterracorp.com
BOUNDARY
FIGURE ES-3c
-- FORMER COAL PILE AREA
COMPARISON OF SIMULATED SELENIUM CONCENTRATIONS FROM
— FORMER PROCESS AREA
THE POTENTIAL BENEFIT OF SOIL EXCAVATION IN THE 1984 ASH
ONSITE LANDFILL BOUNDARY
BASIN MODEL
ONSITE LANDFILL COMPLIANCE
FLOW AND TRANSPORT MODELING REPORT
BOUNDARY
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
-- SAND MINES

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex - Duke Energy Progress, LLC
TABLE OF CONTENTS
SECTION
PAGE
EXECUTIVE SUMMARY.................................................................................................... ES-1
1.0 INTRODUCTION...........................................................................................................1-1
1.1
General Setting and Background..........................................................................1-1
1.2
Objectives.................................................................................................................1-3
2.0 CONCEPTUAL SITE MODEL.....................................................................................
2-1
2.1
Groundwater System Framework........................................................................2-1
2.2
Flow System.............................................................................................................2-2
2.3
Hydrologic Boundaries..........................................................................................
2-5
2.4
Hydraulic Boundaries............................................................................................
2-6
2.5
Sources and Sinks....................................................................................................2-6
2.6
Water Budget...........................................................................................................2-6
2.7
Modeled Constituents of Interest.........................................................................
2-6
2.8
Constituent Transport............................................................................................
2-7
3.0
COMPUTER MODEL.................................................................................................... 3-1
3.1
Model Selection.......................................................................................................
3-1
3.2
Model Description..................................................................................................
3-1
4.0
GROUNDWATER FLOW AND TRANSPORT MODEL CONSTRUCTION ....
4-1
4.1
Model Domain and Grid........................................................................................4-1
4.2
Hydraulic Parameters............................................................................................4-3
4.3
Flow Model Boundary Conditions.......................................................................4-4
4.4
Flow Model Sources and Sinks.............................................................................
4-4
4.5
Flow Model Calibration Targets...........................................................................
4-7
4.6
Transport Model Parameters.................................................................................4-8
4.7
Transport Model Boundary Conditions............................................................
4-10
4.8
Transport Model Sources and Sinks...................................................................
4-11
4.9
Transport Model Calibration Targets................................................................
4-11
5.0
MODEL
CALIBRATION TO CURRENT CONDITIONS......................................5-1
5.1
Flow Model Calibration.........................................................................................
5-1
5.2
Flow Model Sensitivity Analysis..........................................................................
5-3
5.3
Historical Transport Model Calibration..............................................................
5-4
5.4
Transport Model Sensitivity Analysis.................................................................
5-8
6.0
PREDICTIVE SIMULATIONS OF CLOSURE SCENARIOS................................6-1
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex - Duke Energy Progress, LLC
TABLE OF CONTENTS (CONTINUED)
SECTION PAGE
6.1 Simulation of Future Conditions with MNA and Corrective Actions ............ 6-1
6.1.1 MNA Model................................................................................................... 6-2
6.1.2 Nine Extraction Wells.................................................................................... 6-3
6.1.3 Pump and Treat.............................................................................................. 6-5
6.2 Model to Evaluate the Potential Benefit of Soil Excavation in the 1984 Ash
BasinArea................................................................................................................ 6-6
6.3 Conclusions Drawn From the Predictive Simulations .................................... 6-11
7.0 REFERENCES.................................................................................................................. 7-1
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
LIST OF FIGURES
Figure ES-1a
Comparison of simulated boron concentrations
Figure ES-1b
Comparison of simulated selenium concentrations
Figure ES-2a
Comparison of corrective action simulated boron concentrations
approximately 30 years after source excavation.
Figure ES-2b
Comparison of corrective action simulated selenium concentrations
approximately 30 years after source excavation.
Figure ES-3a
Comparison of simulated boron concentrations from the potential
benefit of soil excavation in the 1984 ash basin model
Figure ES-3b
Comparison of simulated arsenic concentrations from potential benefit
of soil excavation in the 1984 ash basin model
Figure ES-3c
Comparison of simulated selenium concentrations from the potential
benefit of soil excavation in the 1984 ash basin model
Figure 1-1
Site location map
Figure 2-1
Monitoring well locations
Figure 4-1
Numerical model domain
Figure 4-2
Fence diagram of the 3D hydrostratigraphic model used to construct the
model grid 5x vertical exaggeration
Figure 4-3a
Computational grid used in the model with 5x vertical exaggeration
Figure 4-3b
Model computational grid in plan view
Figure 4-4
Hydraulic conductivity estimated from slug tests performed in ash at 14
sites in North Carolina
Figure 4-5
Hydraulic conductivity estimated from slug tests performed in the
upper surficial flow zone at Sutton
Figure 4-6
Hydraulic conductivity estimated from slug tests performed in the lower
surficial flow zone at Sutton
Figure 4-7
Hydraulic conductivity estimated from slug tests performed in the
upper Peedee Aquifer at Sutton
Figure 4-8
Hydraulic conductivity estimated from slug tests performed in the lower
Peedee Aquifer at Sutton
Figure 4-9
Distribution of model recharge zones (2019)
Figure 4-10
Model surface water features (2019)
Figure 4-11
Location of water supply wells in model area
Figure 5-1
Pre -excavation model hydraulic conductivity zones in ash layers 1
through 2
Figure 5-2a
Pre -excavation Model hydraulic conductivity zones in upper surficial
layers 3 through 6
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
LIST OF FIGURES (CONTINUED)
Figure 5-2b Pre -excavation Model hydraulic conductivity zones in upper surficial
layers 7 through 8
Figure 5-2c
Pre -excavation Model hydraulic conductivity zones in upper surficial
layers 9 through 10
Figure 5-3a
Pre -excavation Model hydraulic conductivity zones in lower surficial
layer 11
Figure 5-3b
Pre -excavation Model hydraulic conductivity zones in lower surficial
layer 12
Figure 5-4
Pre -excavation Model hydraulic conductivity zones in upper Peedee
layers 13 through 15
Figure 5-5a
Pre -excavation Model hydraulic conductivity zones in lower Peedee
layers 16 through 17
Figure 5-5b
Pre -excavation Model hydraulic conductivity zones in lower Peedee
layer 18
Figure 5-6
Post -excavation Model hydraulic conductivity zones in ash layers 1
through 2
Figure 5-7a
Post -excavation Model hydraulic conductivity zones in upper surficial
layers 3 through 6
Figure 5-7b
Post -excavation Model hydraulic conductivity zones in upper surficial
layers 7 through 8
Figure 5-7c
Post -excavation Model hydraulic conductivity zones in upper surficial
layers 9 through 10
Figure 5-8a
Post -excavation Model hydraulic conductivity zones in lower surficial
layer 11
Figure 5-8b
Post -excavation Model hydraulic conductivity zones in lower surficial
layer 12
Figure 5-9
Simulated heads as a function of observed heads from the 2017 pre -
excavated calibrated steady state flow model
Figure 5-10
Simulated pre -excavated (2017) hydraulic head in the upper surficial
from the calibrated steady state flow model (model layer 8)
Figure 5-11
Simulated pre -excavated (2017) flow system in the upper surficial from
the calibrated steady state flow model (model layer 8)
Figure 5-12
Simulated heads as a function of observed heads from the 2019 post -
excavated calibrated steady state flow model
Figure 5-13
Simulated post -excavated (2019) hydraulic head in the upper surficial
from the calibrated steady state flow model (model layer 8)
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
LIST OF FIGURES (CONTINUED)
Figure 5-14 Simulated post -excavated (2019) flow system in the upper surficial from
the calibrated steady state flow model (model layer 8)
Figure 5-15a Boron, and selenium source zones for the historical transport model pre -
excavation (2017)
Figure 5-15b Deep excavated area below ash in the 1971 ash basin for the 2019 post -
excavation simulation
Figure 5-16a Simulated 2017 pre -excavation maximum boron concentrations in all
non -ash layers
Figure 5-16b Simulated 2017 pre -excavation maximum selenium concentrations in all
non -ash layers
Figure 5-17a Simulated 2019 post -excavation maximum boron concentrations in all
non -ash layers
Figure 5-17b Simulated 2019 post -excavation maximum selenium concentrations in all
non -ash layers
Figure 6-1
FADA excavation design used in the simulations (Geosyntec, 2017)
Figure 6-2
FPA excavation design used in the simulations (Geosyntec, 2020)
Figure 6-3
Simulated hydraulic heads in upper surficial after source excavation
with MNA (model layer 8)
Figure 6-4a
Simulated maximum boron concentrations approximately 10 years after
the source excavation is completed with MNA
Figure 6-4b
Simulated maximum boron concentrations approximately 200 years
after the source excavation is completed with MNA
Figure 6-4c
Simulated maximum boron concentrations approximetely 400 years
after the source excavation is completed with MNA
Figure 6-4d
Simulated maximum boron concentrations approximately 700 years
after the source excavation is completed with MNA
Figure 6-5a
Simulated maximum selenium concentrations approximately 10 years
after the source excavation is completed with MNA
Figure 6-5b
Simulated maximum selenium concentrations approximately 20 years
after the source excavation is completed with MNA
Figure 6-6
Simulated hydraulic heads in upper surficial after the source excavation
with nine extraction wells followed by MNA (model layer 8)
Figure 6-7a
Simulated maximum boron concentrations approximately 10 years after
the source excavation with nine extraction wells followed by MNA
Figure 6-7b
Simulated maximum boron concentrations approximately 200 years
after the source excavation with nine extraction wells followed by MNA
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex - Duke Energy Progress, LLC
LIST OF FIGURES (CONTINUED)
Figure 6-7c Simulated maximum boron concentrations approximetely 400 years
after the source excavation with nine extraction wells followed by MNA
Figure 6-7d Simulated maximum boron concentrations approximately 700 years
after the source excavation with nine extraction wells followed by MNA
Figure 6-8a Simulated maximum selenium concentrations approximately 10
years after the sourceexcavation with nine extraction wells followed
by MNA
Figure 6-8b Simulated maximum selenium concentrations approximately 20
years after the source excavation with nine extraction wells followed by MNA
Figure 6-9 Pump and treat simulations well layout
Figure 6-10
Pump and treat Simulations and hydraulic heads flow field (layer 8)
Figure 6-11
Simulated maximum boron concentrations after approximately 30 years
of pump and treat operation (year 2050)
Figure 6-12
Simulated maximum selenium concentrations after approximately 30
years of pump and treat operation (year 2050)
Figure 6-13
Location of soil samples within former 1984 ash basin and simulated
hydraulic heads
Figure 6-14
Vertically averaged boron SPLP concentrations.
Figure 6-15
Vertically averaged arsenic SPLP concentrations.
Figure 6-16
Vertically averaged selenium SPLP concentrations.
Figure 6-17
Converted pore water concentration of boron assigned to the top 3 feet
of soil in the 1984 Ash Basin footprint in 2019
Figure 6-18
Converted pore water concentration of arsenic assigned to the top 3 feet
of soil in the 1984 Ash Basin footprint in 2019
Figure 6-19
Converted pore water concentration of selenium assigned to the top 3
feet of soil in the 1984 Ash Basin footprint in 2019
Figure 6-20a Simulated maximum boron concentrations approximately 5 years after
the initial calibrated simulation
Figure 6-20b Simulated maximum boron concentrations approximately 10 years after
the initial calibrated simulation
Figure 6-20c Simulated maximum boron concentrations approximately 20 years after
the initial calibrated simulation
Figure 6-20d Simulated maximum boron concentrations approximtely 30 years after
the initial calibrated simulation
Figure 6-21a Simulated maximum arsenic concentrations approximtely 5 years after
the initial calibrated simulation
Figure 6-21b Simulated maximum arsenic concentrations approximtely 10 years after
the initial calibrated simulation
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
LIST OF FIGURES (CONTINUED)
Figure 6-21c Simulated maximum arsenic concentrations approximtely 20 years after
the initial calibrated simulation
Figure 6-21d Simulated maximum arsenic concentrations approximtely 30 years after
the initial calibrated simulation
Figure 6-22a Simulated maximum selenium concentrations approximtely 5 years after
the initial calibrated simulation
Figure 6-22b Simulated maximum selenium concentrations approximtely 10 years
after the initial calibrated simulation
Figure 6-22c Simulated maximum selenium concentrations approximtely 20 years
after the initial calibrated simulation
Figure 6-22d Simulated maximum selenium concentrations approximtely 30 years
after the initial calibrated simulation
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex - Duke Energy Progress, LLC
LIST OF TABLES
Table 5-1
Pre -excavation (2017) calibrated hydraulic conductivity parameters
Table 5-2
Post -excavation (2019) calibrated hydraulic conductivity parameters
Table 5-3
Observed, computed, and residual heads for the calibrated pre -
excavation (2017) flow model
Table 5-4
Observed, computed, and residual heads for the calibrated post -
excavation (2019) flow model
Table 5-5
Pre -Excavation Flow model sensitivity analysis
Table 5-6
Post -Excavation Flow model sensitivity analysis
Table 5-7a
Ash basin boron source concentrations used in the pre -excavation
historical transport model
Table 5-7b
Ash basin selenium concentrations used in the pre -excavation historical
transport model
Table 5-8a
Observed and computed boron (µg/L) concentrations for the pre -
excavation (2017) in monitoring wells
Table 5-8b
Observed and computed selenium (µg /L) concentrations for the pre -
excavation (2017) in monitoring wells
Table 5-9a
Observed and computed boron (µg/L) concentrations for the post -
excavation (2019) in monitoring wells
Table 5-9b
Observed and computed selenium (µg /L) concentrations for the post -
excavation (2019) in monitoring wells
Table 5-10
Transport model sensitivity to the boron Ka values for pre -excavation
model
Table 5-11
Transport model sensitivity to the boron Ka values for post -excavation
model
Table 6-1
Conversion of SPLP concentrations to equivalent pore water
concentrations as a function of the Ka value
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
1.0 INTRODUCTION
This groundwater flow and transport modeling report provides an update to a previous
model developed by SynTerra in conjunction with Falta Environmental, LLC and Frx
Partners (SynTerra, 2017). This updated report for the L.V. Sutton Energy Complex
(Sutton, Plant, Site), which is owned and operated by Duke Energy Progress, LLC
(Duke Energy) includes basic model development information and simulations of
source areas. Source areas include: the 1971 ash basin, 1984 ash basin, former process
area (FPA), former ash disposal area (FADA), and former coal pile area (FCPA). Closure
designs of the source areas as well as results of corrective action are included.
Model simulations were developed using flow and transport models MODFLOW and
MT3DMS. Numerical simulations of groundwater flow and transport have been
calibrated to pre -excavation conditions and post -excavation conditions of the 1971 and
1984 ash basins. The simulations were also used to assess potential hydraulic corrective
action alternatives at Sutton to reduce COI concentrations to less than applicable
comparison criteria at or beyond the compliance boundary, consistent with Subchapter
02L .0106(e)(4) and to address Subchapter 02L .0106(j). Applicable criteria in this case is
defined as the Groundwater Classification and Standards (02L) groundwater standard,
Interim Maximum Allowable Concentrations (IMAC), or Site background threshold
value (BTV), whichever is greatest, defined as the COI criteria. If a COI does not have
an 02L standard or IMAC, then the background value defines the COI criteria. Risk -
based cleanup values are calculated in the CAP Update (SynTerra, 2020) for the non-
CAMA source areas (the FADA and FCPA) using the North Carolina Risk Calculator. In
the case of those source areas, risk -based cleanup values are appropriate for
determining corrective action objectives. The simulations focus on closure designs and
the potential effects of hydraulic corrective actions, and the effects of post excavation
impacts within the 1984 ash basin.
1.1 General Setting and Background
The Site encompasses 3,300 acres along the east bank of the Cape Fear River, northwest
of the City of Wilmington in New Hanover County, North Carolina (Figure 1-1). The
Plant became operational in 1954 as a three -unit coal-fired electricity -generating facility
with a maximum capacity of 575 megawatts (MW). The three coal-fired units were
retired in November 2013. The Plant currently operates as a natural gas -fired electricity -
generating facility.
In 1971, a 1,100-acre pond was built for cooling water at the Plant. The Plant's cooling
pond, also referred to as Sutton Lake. In early 2015, the cooling pond was also classified
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
as waters of the state (WOS). In addition to WOS, the cooling pond is also a National
Pollutant Discharge Elimination System (NPDES)-permitted wastewater treatment unit.
The cooling pond has been regulated as both WOS and a NPDES-permitted wastewater
treatment unit since 2015. This updated report will refer to this Site feature as the
cooling pond. The cooling pond is located west of the Plant (Figure 1-1).
An area known as the FPA was adjacent to the southeast corner of the 1971 basin
(Figure 1-1). The FPA was a small settling basin when the Plant was co -firing fuel oil
and was used for a few years in the 1970s. At that time, sluice waters were directed to
the settling basin located in the FPA before discharge to the 1971 ash basin. The FPA
was approximately 250 feet by 150 feet with an approximate depth of 8 feet with
concrete -lined side walls. The FPA was subsequently filled with coal combustion
residuals (CCRs) and solids.
Coal was historically stored at the Site's former coal pile area (FCPA), an unlined area
located west of the Plant and east of the Cape Fear River. The former coal storage area
consists of approximately 14 acres bounded to the north by the former ash disposal
area, to the east by vacant land formerly containing plant buildings (now razed) and
parking areas, and to the south and west adjacent to the cooling pond and intake canal.
After coal -burning operations ended in 2013, coal was removed from the coal pile from
2014 to 2015 and the area has been graded.
Coal ash and other CCRs were sluiced to a low-lying area and two ash basins,
collectively referred to as the ash management area. Coal ash was originally sluiced to
the FADA located just north of the Plant coal pile and on the south side of the cooling
water effluent canal (Figure 1-1). In 1971, an unlined ash basin known as the 1971 basin
(old ash basin) was built along with the construction of the cooling pond and was
situated on the eastern side of the cooling pond (Figure 1-1). A portion of the 1971 basin
was constructed by excavation below the water table as a borrow pit for construction of
earthen dikes. Another ash basin was built in 1984 and is referred to as the 1984 basin
(new ash basin). The 1984 basin was constructed with a 12-inch-thick clay liner above
the water table. It was located toward the northern portion of the ash management area,
and was operated from 1984 to 2013 (Figure 1-1).
Closure of the 1971 and 1984 ash basins began in 2015 and was completed in June 2019.
Closure activities included dewatering the 1971 ash basin to the maximum extent
practicable, removing CCRs from the 1971 and 1984 ash basins, and transferring the
removed CCRs to a lined landfill or structural fill. Based on ash basin excavation
records, approximately 6,320,000 tons of ash were excavated from the ash basins. The
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
former 1971 ash basin is filled with water, separated from the cooling pond and the
effluent canal by sheet piling and an earthen dike. During 2015 and 2016, ash was
removed from the Site, initially by truck and then by train for use as structural fill at the
Brickhaven facility. An on -Site ash landfill was subsequently constructed east of the ash
management area in 2016 and 2017. Since July 2017, CCRs from the ash basins were
placed in the newly constructed on -Site landfill.
The Site lies within the Coastal Plain Physiographic Province. The topography at the
Site is relatively flat, with a maximum elevation of about 30 ft. The land surface
generally slopes toward the Cape Fear River to the west and south. The Site is bounded
to the west by the Cape Fear River, to the north by undeveloped land, and to the east by
a sand quarry and light industrial use properties. The Cape Fear River borders the Site
immediately to the west. The Cape Fear River flows south toward Wilmington and is
tidally influenced.
A groundwater flow and transport model for the Site was first developed in 2015 by
SynTerra, Falta Environmental, LLC, and Frx Partners as part of the Corrective Action
Plan (CAP) Part 1 (SynTerra, 2015b). The model was revised in the 2016 as part of the
Corrective Action Plan (CAP) Part 2 (SynTerra, 2016b). In 2017, SynTerra and Falta
Environmental, LLC updated the model to include the Geosyntec closure design for the
ash basins and was incorporated in the Geosyntec 2017 Interim Action Plan
Implementation Basis of Design Report (Attachment C, Geosyntec, 2017b).
1.2 Objectives
The purpose of the work presented is to update the 2017 groundwater flow and
transport model of the Sutton site. To sharpen resolution, the number of model layers
was increased from 13 to 18. Additional assessment activities, such as the installation of
additional groundwater monitoring wells and multiple groundwater sampling events,
have resulted in an increase of data describing hydraulic head and constituent of
interest (COI) distribution; those data are also included in the model. This report
describes the current understanding of the groundwater flow and transport processes of
mobile constituents at the Site. The second part of the report provides basic model
development information and simulations of the effects attributed to closure actions
and hydraulic corrective action simulations, and the effects of post excavation impacts
within the 1984 ash basin.
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
The following data sources were used during calibration of the revised groundwater
flow and transport model:
• Average Site -wide water levels measured in CAMA/CCR/Compliance
groundwater monitoring wells through second quarter of 2017 for pre -
excavation conditions and fourth quarter 2019 for post -excavation conditions
• Groundwater quality data obtained from CAMA/CCR/Compliance sampling
events conducted from second quarter of 2017 for pre -excavation conditions and
fourth quarter 2019 for post -excavation conditions
• Surface water elevations, as described in the Comprehensive Site Assessment
(CSA) Update (SynTerra, 2018), and from surface water surveys conducted in
2019
• Cooling pond water elevation during December 2019, provided by Duke Energy
• Estimated recharge, as described in SynTerra modeling report (SynTerra, 2017)
The model revision consisted of five activities:
Re -calibration of the pre -excavation steady-state groundwater flow model to
hydraulic heads averaged through 2017.
2. Calibration of the post -excavation steady-state groundwater flow model to
hydraulic heads from the fourth quarter of 2019.
3. Calibration of a transient model of the transport of boron and selenium using the
revised flow model and COI concentrations measured through the second
quarter of 2017.
4. Calibration of a transient model of the transport of boron and selenium using the
post -excavation flow model, and COI concentrations measured from the fourth
quarter of 2019.
5. Development of predictive simulations that include excavation of the 1971 basin,
1984 basin, FADA, and FPA with remedial measures at the Site.
The predictive model simulates the excavation of ash from the 1971 ash basin, 1984 ash
basin, FADA, and FPA and the placement of ash in an on -Site landfill (GeoSynTec
2017a,b,c, 2019, 2020), and the removal of coal from the FCPA.
The predictive simulations are intended to show the key characteristics of groundwater
flow and mobile constituent transport that are expected to result from excavation
closure, corrective action, and the effects of post excavation impacts within the 1984 ash
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
basin. The simulations are not intended to represent a final detailed closure design
within the FADA and FPA. These simulations use current designs that are subject to
change as the closure plans are finalized.
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
2.0 CONCEPTUAL SITE MODEL
The conceptual site model of the Sutton site is primarily based on the following
documents:
• Comprehensive Site Assessment (CSA) Report (SynTerra, 2015a)
• Corrective Action Plan (CAP) Part 1 (SynTerra, 2015b)
• Corrective Action Plan Part 2 (SynTerra, 2016a)
• Comprehensive Site Assessment Supplement 1 (SynTerra, 2016b)
• Comprehensive Site Assessment Update (SynTerra, 2018)
The CSA reports contain extensive detail and data related to most aspects of the
conceptual site model.
2.1 Groundwater System Framework
The Site, located in the Coastal Plain Physiographic Province of North Carolina,
conforms to the general hydrogeologic framework of the Tidewater region of the
Coastal Plain, which is characterized by aquifers comprised of permeable sands,
gravels, and limestone separated by confining units of less permeable material. The
streams and many of their tributaries are affected by ocean tides (Winner and Coble,
1989).
The groundwater system at the Site is an interconnected system of unconfined and
confined aquifers with five identified hydrostratigraphic units: the ash pore water
(confined to the area of the ash basin); the upper surficial zone (fine- to medium -
grained sand, first 25 feet of the surficial zone); a lower surficial zone (medium- to
course -grained sand, bottom 25 feet of the surficial zone); the upper Peedee formation
(fine sand with silt, typically 50-100 feet below ground surface); and the lower Peedee
formation (fine sand and silt with clay, greater than 120 feet below ground surface). The
Peedee formation extends to a depth of about 350 feet at the Site, where it overlies the
Black Creek confining unit (Bukowski McSwain, et al., 2014; Harden et al., 2003). The
first occurrence of groundwater at the Site is in the surficial aquifer at depths ranging
from 3 feet bgs to 17 feet bgs (SynTerra, 2018).
Regionally, the surficial aquifer is underlain by the Peedee confining unit. The Peedee
confining unit is present throughout most of New Hanover County (Bukowski
McSwain, et al., 2014), where it confines the underlying Peedee aquifer; however,
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Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
extensive deep (up to 150 feet) drilling performed during the CSA (SynTerra, 2015a)
study did not encounter the Peedee confining unit (clay) at the Sutton Site.
At the Site, hydraulic conductivity was measured in the field using slug tests in wells
screened within the various hydrostratigraphic units and one pumping test performed
by HDR (2016). The slug tests were analyzed by SynTerra using analytical methods in
AQTESOLV (SynTerra, 2018). Twelve (12) slug tests were performed in wells screened
in the ash pore water. Hydraulic conductivities from those tests ranged from
approximately 0.1 feet per day (ft/d) to 2.3 ft/d, with a geometric mean of 0.7 ft/d and a
median of 0.8 ft/d (SynTerra, 2018).
Eighty-eight (88) slug tests were performed in the wells screened in the upper surficial
flow zone. Hydraulic conductivities from those tests ranged from 0.9 ft/d to 198 ft/d,
with a geometric mean of 47 ft/d and a median of 53 ft/d. Ninety-seven (97) slug tests
were performed in the wells screened in the lower surficial flow zone; hydraulic
conductivities from those tests ranged from about 5 ft/d to 174 ft/d, with a geometric
mean of 74 ft/d and a median of 89 ft/d. The May 2016 HDR pump test (HDR, 2016)
indicated a higher hydraulic conductivity value (370 ft/d) in the lower surficial flow
zone.
Twenty-four (24) slug tests were performed in wells screened in the upper Peedee flow
zone (elevations ranging from -70 to -109 feet North American Vertical Datum of 1988
[NAVD 88]). Hydraulic conductivities in the upper Peedee ranged from 0.003 ft/d to
0.37 ft/d, with a geometric mean value of 0.03 ft/d, and a median value of 0.03 ft/d
(SynTerra, 2018). Five (5) slug tests were performed in wells screened in the lower
Peedee (elevations from -126 to -133 feet NAVD 88). These hydraulic conductivities
ranged from 0.0002 ft/d to 0.004 ft/d, with a geometric mean value of 0.0008 ft/day.
Although the Peedee confining unit was not encountered at Sutton, the low hydraulic
conductivity of the Peedee Formation at the Site serves to isolate the shallow surficial
aquifer from deeper units and limit vertical migration of COIs. The hydraulic
conductivity of the Peedee Formation at the Site is 3 to 4 orders of magnitude lower
than the hydraulic conductivity of the surficial aquifer. The contrasting permeability
between the surficial flow zone and Peedee Formation is a significant part of this
conceptual model.
2.2 Flow System
The shallow groundwater system is recharged by precipitation and historically from
water that infiltrated through the ash basins. The average value of recharge in the
vicinity of the Sutton Site was estimated from the recent United States Geological
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Survey (USGS) hydrogeology reports on New Hanover County (Bukowski McSwain, et
al., 2014), Brunswick County (Harden et al., 2003), and from the map of recharge in
North Carolina by Haven (2003). The North Carolina map of recharge by Haven (2003)
gives a range of 6 to 10 inches per year for the upland areas. It was assumed that
recharge was negligible in the vicinity of tidal marshes, rivers (Cape Fear River), cooling
pond, and canals that serve as discharge areas for the groundwater system. The USGS
report on New Hanover County reports an average infiltration rate range of 12 to 16
inches per year, and the report on adjacent Brunswick County reports an average
infiltration rate of 11 inches per year.
At Sutton, there are five COI source areas: the FADA, 1971 basin, FPA, 1984 basin, and
the FCPA. The ash basins have been excavated. Excavation of the FPA was completed
in April 2020. Excavation of the FADA was completed in June 2020.
The FADA operated until 1971, and appears to have been an unlined low-lying area
that was filled with ash. The thickness of the ash encountered there extended from the
ground surface to a depth of approximately 8 feet.
The 1971 ash basin was constructed by excavating portions (dredging) below the water
table to a depth of approximately 40 feet below grade. All but the lower two feet of the
surficial sands were removed in some areas during basin construction; as a result, much
of the ash in the 1971 basin was just above the contact between the surficial flow zone
and Peedee Formation. The 1971 ash basin is bounded by the 1984 ash basin to the north
and east (1983 extension), by the effluent canal to the south, and by the cooling pond to
the west. The effluent canal and the cooling pond affect the groundwater elevation in
the surficial aquifer west and south of the 1971 ash basin.
In its previous configuration, the 1971 ash basin had an outfall to the cooling pond that
operated from 1971 to 1984 when the new 1984 basin was put into operation. Discharge
from the 1971 ash basin to the cooling pond ceased at that time however, an emergency
outfall remained for periods of heavy rain. The emergency outfall was rarely used. In
addition to sluice water and rainfall, the basin received stormwater from the Sutton
Plant until June 2016. Vegetation on the ash basin was sparse to nonexistent, and the ash
had a moderate hydraulic conductivity (on the order of 1 ft/d) (SynTerra, 2018). The
recharge rate in the basin was estimated to be approximately 30 inches per year, based
model calibration and the average annual rainfall rate of 55 inches per year. This
combination of factors likely led to enhanced infiltration in the ash basin (when
compared to the surrounding area) and a mounding effect that occurred and resulted in
radial groundwater flow and eastward COI migration. Additionally, during active ash
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sluicing operations in the past, large amounts of water entered the ash basins. The
sluicing was performed by pumping an ash -water slurry though large (approximately
10-12 inch) pipes at flow rates of roughly 1,000 to 3,000 gallons per minute. The sluice
pipes typically discharged into diked subareas of the ash basins, where the solids were
allowed to settle. The excess water accumulated at the lower end of the ash basins
where it was discharged from an engineered control structure. The sluicing activities
would have likely added to already high rates of infiltration in the ash basins, but the
actual rate of infiltration during active sluicing operations is not known.
An area known as the FPA was adjacent to the southeast corner of the 1971 basin
(Figure 1-1). The FPA was a small settling basin when the Plant was co -firing fuel oil
and was used for a few years in the 1970s. At that time, sluice waters were directed to
the settling basin located in the FPA before discharge to the 1971 basin. The FPA was
approximately 250 feet by 150 feet with an approximate depth of 14 feet with concrete -
lined side walls. The FPA was subsequently filled with CCRs and suspected #6 fuel oil
waste in the 1970s.
The 1984 ash basin, constructed at approximately the original ground surface, contained
a clay liner. Ponded water was generally present in the northern portion of the basin,
prior to basin closure. The 1984 ash basin had an outfall to the cooling pond that was in
operation from 1984 to 2001. In 2001, an underground line was installed from the 1984
ash basin outfall to the outfall at the Cape Fear River. This line could not fully
accommodate all of the 1984 ash basin discharge. There was still a portion of discharge
from the 1984 ash basin to the cooling pond between 2001 and 2015 when the cooling
pond was reclassified as waters of the state. Groundwater flow from the 1984 ash basin
prior to closure was also radial, under the dam to the west, north, and east. Recharge to
the groundwater system from the 1984 ash basin was estimated by taking the hydraulic
head difference inside and outside the ash basin and using Darcy's law to estimate the
rate of leakage through the 12-inch clay liner. The estimated recharge value in the 1984
basin used in previous models was 30 inches per year after sluicing was discontinued.
This infiltration rate is equivalent to the leakage that would result from a head
difference of 15 feet across the clay liner with an average hydraulic conductivity of
0.00045 ft/d. This recharge rate is uncertain, but it should be less than the average
rainfall rate of 55 inches per year. The current steady-state model uses the regional
value for recharge (16 inches per year) to reflect recent site configuration following
removal of the ash.
Several changes that significantly affected the groundwater flow system have occurred
at the Site in recent years. First, decanting and removal of the ash from the 1971 and
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1984 basins began in 2015 and was completed in June 2019. This removed the elevated
hydraulic head which previously caused radial flow and a mounding effect from the
basins. Since basin closure and construction of the new on -Site landfill, data indicate
that groundwater flow is now consistently northeast to southwest across the Site. After
excavation and dredging, the 1971 ash basin footprint is currently submerged; water
within the former basin is separated by sheet piling from the effluent canal and the
cooling pond. Second, a new lined landfill has been constructed east of the 1971 and
1984 basins where a local groundwater divide and recharge zone previously existed; the
new landfill area includes stormwater retention ponds on the northeast and south sides.
This has altered the groundwater recharge pattern, and groundwater elevation data
indicate the local groundwater divide is now present east of the Site, adjacent to the
sand quarry. Third, the quarries east of the Site have expanded, thereby increasing the
recharge effect in that area. Lastly, a groundwater extraction system has been installed
along the eastern Site boundary, creating a localized groundwater sink.
According to the 2018 CSA report (SynTerra, 2018), receptor wells were identified
during receptor surveys conducted in 2014 and 2015, and twenty six (26) private supply
wells were identified within 0.5-mile radius of the compliance boundary. Screen
elevations and pumping rates from most of these wells are not known, but they almost
certainly are screened in the surficial aquifer. No residences were identified in the area,
and the wells mostly service light industrial or office/business properties. The nearby
industrial production wells along the northeastern property line pumps a large volume
of water from a series of supply wells in the area, however currently only one industrial
well was assumed to be in operation due to the lower hydraulic heads observed at
monitoring well cluster MW-8 north of the Site. While the location of some of the
industrial production wells are known, details of their well field and pumping rates
were generally not available.
According to public records, four Cape Fear Public Utility Authority (CFPUA) public
supply wells were formally located adjacent to or near the southeastern boundary of the
Site. However, those wells were abandoned in March 2016.
2.3 Hydrologic Boundaries
The major discharging locations for the shallow groundwater system (the cooling pond,
the marshes and swamps, and the Cape Fear and Northeast Cape Fear rivers) serve as
hydrologic boundaries. There are no hydrologic boundaries in the deeper confined
aquifers within the study area.
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2.4 Hydraulic Boundaries
The shallow groundwater system does not appear to contain impermeable barriers or
boundaries in the study area except possibly for the steel piling enclosure separating the
ponded water in the 1971 basin from the cooling pond and the effluent channel. The
low permeability silts and clays in the Peedee Formation beneath the surficial aquifer
restrict flow into the deeper confined aquifers. The Peedee Formation is bounded below
by the low permeability Black Creek confining unit; for practical purposes, this can be
considered a no -flow hydraulic barrier.
2.5 Sources and Sinks
A source is defined herein as a place where water enters the groundwater system, and a
sink is where water leaves the system. Recharge in general is the major source of water
to the surficial flow zone. Most of this water discharges to the hydrologic boundaries
described above, with a relatively small amount recharging the underlying Peedee
aquifer.
There are approximately 45 known water supply wells that act as sinks to groundwater
in the vicinity of the Site. North of the Site, industrial wells pumps a large volume of
water from a series of supply wells in the area. While the location of some of the
industrial wells are known, details of their well field and pumping rates were not
available. In the pre -excavation model, two CFPUA water supply wells were simulated
in the model area; however, those wells were abandoned in March 2016 and were not
included in the post -excavation model. The rest of the water supply wells remove only
a small amount of water from the overall hydrologic system.
2.6 Water Budget
The long-term average rate of water inflow is assumed to equal the long-term average
rate of water outflow from the study area. Water enters the groundwater system
through distributed recharge, or leakage of ash basin pore water, and underflow in the
deeper confined aquifers. Water leaves the system through discharge to the rivers,
marshes, swamps, pumping wells, and through underflow in the deeper confined
aquifers.
2.7 Modeled Constituents of Interest
Arsenic, alkalinity, boron, calcium, chloride, chromium (hexavalent), cobalt, fluoride,
iron, lithium, magnesium, manganese, molybdenum, potassium, selenium, sodium,
strontium, sulfate, TDS, and vanadium have been identified as constituents of interest
(COIs) at Sutton (SynTerra, 2018). Of these COIs, arsenic, alkalinity, boron, calcium,
cobalt, iron, lithium, magnesium, manganese, molybdenum, potassium, selenium,
sodium, strontium, sulfate, TDS, and vanadium concentrations were greater than the
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02L or applicable groundwater standards at or beyond the compliance boundary and
would be subject to corrective action per Subchapter 02L .0106(e)(4).
Two COIs are assumed to be present beyond the western and southern compliance
boundary within the cooling pond and that have characteristics of groundwater plumes
were selected for inclusion in the transport models of the Site. Those COIs are boron,
and selenium. Arsenic was also considered in an analysis of the unsaturated soils in the
1984 ash basin area.
The 2017 (pre -excavation) boron concentrations observed downgradient of the 1971 ash
basin greater than the 02L standard extended past compliance boundary wells east of
the ash basins. The 2019 post -excavation boron concentrations have decreased to less
than 02L beyond the compliance boundary east of the ash basins. Boron migration
appears to occur mainly in the lower surficial aquifer. Boron was detected at
concentrations greater than the 02L standard in most of the upper Peedee wells
(elevations of about -70 to -90 ft NAVD 88) and in all of the lower Peedee wells
(elevations of about -120 to -130 feet NAVD 88). Boron concentrations in the Peedee
Formation tend to increase with depth; hence, greater concentrations of boron were
often found in the deepest wells. The deep wells also exhibit greater concentrations of
chloride. The pattern of increasing boron concentration with depth, coupled with the
increased salinity and the very low hydraulic conductivity of the Peedee Formation
suggest that the boron found in the Peedee Formation is naturally occurring. Boron is
present in seawater at an average concentration of 4,600 micrograms per liter (µg/L),
and it is known to accumulate in marine clays. Boron has been found greater than the
02L standard in the Peedee Formation at North Myrtle Beach, SC at a depth of 100 feet,
and it is commonly encountered in deeper wells (Lee, 1984).
In the 2017 pre -excavation monitoring well data, selenium has been detected at
concentrations greater than the 02L standard in four monitoring wells (CCR-114C, MW-
27C, MW-36C, and MW-40C), located immediately north of the 1984 ash basin and is at
or within the compliance boundary. Selenium is generally not detected at the Site
outside of this relatively small area north of the 1984 ash basin, however is at or within
the compliance boundary. The post excavation model simulates a similar selenium
concentration extent and no wells beyond the compliance boundary detect selenium
above the 2L standard.
2.8 Constituent Transport
COIs present in coal ash can dissolve into the ash pore water. As water infiltrates
through the basins, water containing COIs can enter the groundwater system through
the bottom of the ash basins. Once in the groundwater system, COIs are transported by
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advection and dispersion, subject to retardation due to adsorption to solids. Similarly,
water that infiltrates through the FCPA can transport COIs into the groundwater
system below the FCPA. If COIs reach a hydrologic boundary or water sink, they are
removed from the groundwater system and enter the surface water system, where in
general, they are greatly diluted.
At Sutton, boron is the primary constituent that is migrating from the ash basins,
FADA, and FPA. Boron is appears to be non -reactive with subsurface solids and
therefore is a conservative estimate and indicator of constituent transport in
groundwater. Dissolved plumes of selenium are also present at the Site, and this COI is
included in the transport model. Unlike boron, selenium is reactive, and its mobility is a
function of geochemical conditions. The transport model described here does not
account for variable geochemical conditions, and simulates selenium adsorption using a
linear equilibrium Kd approach. Separate geochemical model simulations show that the
expected Kd values for selenium range over several orders of magnitude. The Kd value
used in the transport model falls at or near the bottom of this range, and represent a
condition where selenium is relatively mobile. Over time, geochemical conditions at the
Site are expected to become more strongly oxidizing. This is expected to cause selenium
to form the less mobile, more strongly sorbing species Se(VI). Arsenic is considered in
the analysis of the 1984 ash basin unsaturated soils using a similar Ka approach with a
relatively low Kd value. Similar to selenium, arsenic is expected to form the less mobile,
more strongly sorbing species As(V) as geochemical conditions become more strongly
oxidizing.
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3.0 COMPUTER MODEL
3.1 Model Selection
The numerical groundwater flow model was developed using MODFLOW (McDonald
and Harbaugh, 1988), a three-dimensional (3D) finite difference groundwater model
created by the USGS. The chemical transport model is the Modular 3-D Transport Multi -
Species (MT3DMS) model (Zheng and Wang, 1999). MODFLOW and MT3DMS are
widely used in industry and government and are considered to be industry standards.
The models were assembled using the Aquaveo GMS 10.4 graphical user interface
(http://www.aquaveo.com/).
3.2 Model Description
MODFLOW uses Darcy's law and the conservation of mass to derive water balance
equations for each finite difference cell. MODFLOW considers 3D transient groundwater
flow in confined and unconfined heterogeneous systems, and it can include dynamic
interaction with pumping wells, recharge, evapotranspiration, rivers, streams, springs,
lakes, and swamps.
Several versions of MODFLOW have been developed since its inception. This study uses
the MODFLOW-NWT version (Niswonger, et al., 2011). The NWT version of MODFLOW
provides improved numerical stability and accuracy for modeling problems with
variable water tables. That improved capability is helpful in the present work where the
position of the water table in the ash basin can fluctuate depending on the conditions
under which the basin is operated and on the closure action activities.
MT3DMS uses the groundwater flow field from MODFLOW to simulate 3D advection
and dispersion of the dissolved COIs, including the effects of retardation due to COI
adsorption to the soil.
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4.0 GROUNDWATER FLOW AND TRANSPORT MODEL
CONSTRUCTION
The flow and transport model of the Site was built through a series of steps:
• Step 1: Build a 3D model of the Site hydrostratigraphy based on field data.
• Step 2: Determine the model domain and construction of the numerical grid.
• Step 3: Populate the numerical grid with flow parameters.
• Step 4: Calibrate the steady-state flow model to pre -excavation hydraulic heads
with adjustments of the flow parameters.
• Step 5: Calibrate the steady-state flow model to post -excavation hydraulic heads.
• Step 5: Develop a transient model of historical flow and transport (pre -
excavation) to provide time -dependent constituent transport development.
• Step 6: Calibrate to post -excavation boron and selenium concentration analytical
data to reproduce the observed COI plumes within the model.
4.1 Model Domain and Grid
The initial steps in the model grid generation process were the determination of model
domain and construction of a 3D hydrostratigraphic model (Figure 4-1). The model has
dimensions of 4.5 miles (-23,500 feet) by 5.1 miles (~27,000 feet). The model is aligned
approximately with the peninsula that is formed by the confluence of the Cape Fear
River and Northeast Cape Fear River. This alignment was chosen so that most of the
outer boundaries to the shallow groundwater system would be the rivers and tidal
swamps and marshes. The model extent was made large enough so that boundary
conditions would not artificially affect results near the area of interest.
The ground surface of the model was interpolated from North Carolina Dept. of
Transportation (NCDOT) light detection and ranging (LIDAR) data from 2007
(httl2s://connect.ncdot.gov/resources/gis/pages/cont-elev v2.aspx). The elevations for
the top of the ash basins were modified using more recent surveying data that was
collected prior to the excavation of ash from the 1971 and 1984 ash basins. The
hydrostratigraphic model (called a solids model in GMS) consists of six units: the 1971
and 1984 ash basins, the upper surficial flow zone (including the FADA, FPA and
FCPA), the Peedee clay confining unit (only present to the east and south of the Site),
the lower surficial flow zone (or the uppermost part of the Peedee formation where the
Peedee confining unit is present), the upper fourth of the Peedee Formation, and the
deeper part of the Peedee Formation (Figure 4-2).
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Five solids were created and then subdivided as the computational mesh was
developed. The lower contact between the ash basin and underlying surficial flow zone
was assumed to be the original ground surface prior to construction of the ash basins.
The area in the 1971 ash basin that was excavated during its construction extends down
almost to the Peedee formation. This was accounted for in the historical models by
assigning a hydraulic conductivity representative of coal ash in this volume.
Contacts between the upper surficial, Peedee clay confining unit, lower surficial, upper
Peedee, and lower Peedee were determined from boring logs from previous studies and
from the CSA report (SynTerra, 2015a; 2016). Contacts between the six units were
estimated for locations where well logs were not available by extrapolation of the
borehole data and by using knowledge of the regional strike and dip of the aquifers
from Bukowski McSwain, et al. (2014) and Harden et al. (2003). The top of the Black
Creek confining unit elevations from Bukowski McSwain, et al. (2014) form the base of
the model. The bottom layer is located at an elevation of about -250 to -350 feet NAVD
88.
The numerical model grid consists of 18 layers representing the hydrostratigraphic
units (Figures 4-3a and 4-3b). The model grid was set up to conform to the
hydrostratigraphic contacts from the solids model. The model grid layers correspond to
the hydrostratigraphic units as follows:
Hydrostratigraphic unit
Grid layer
Ash Basins
1-2
upper surficial
3-10
Peedee Clay Confining Unit (present east of Site)
11
lower surficial
11-12
upper Peedee
13-15
lower Peedee
16-18
Grid layers 1-2 were set as inactive outside of the region of the ash basin as determined
from aerial photos. The bottom layer (18) is a high permeability confined flow zone in
the Peedee formation that rests on top of the Black Creek confining unit.
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The numerical grid consists of rectangular blocks arranged in columns, rows and layers.
There are 166 columns, 154 rows, and 18 layers (Figures 4-3a and 4-3b). The grid
contains a total of 410,434 active cells. The maximum width is 443 feet for the rows and
477 feet for the columns. The size of the grid blocks is refined in the vicinity of both ash
basins to approximately 50 feet in width.
4.2 Hydraulic Parameters
The horizontal hydraulic conductivity and the horizontal to vertical hydraulic
conductivity anisotropy ratio are the main hydraulic parameters in the model. The
distribution of these parameters is based primarily on the model hydrostratigraphy,
with some additional horizontal and vertical heterogeneity. Most of the hydraulic
parameter distributions in the model were uniform throughout a model layer except for
the very high hydraulic conductivity zone identified in the lower surficial flow zone
during the HDR pumping test (HDR, 2016). The geometries and parameter values of the
heterogeneous distributions were determined largely during the flow model calibration
process, and to a lesser extend during the transport model calibration. Initial estimates
of parameters were based on literature values; results of slug tests, the HDR pumping
test and simulations performed using the previous flow models. The hydraulic
parameter values were adjusted during the flow model calibration process (described in
Section 5.0) to provide the best fit to observed water levels in observation wells.
The hydraulic conductivity of coal ash measured at 14 sites in North Carolina ranges
over 5 orders of magnitude, with a geometric mean value of approximately 1.7 ft/d. At
Sutton, ash hydraulic conductivity values are estimated by interpreting 12 slug tests
performed in two wells screened within the ash pore water (ABMW-1 and ABMW-2).
Hydraulic conductivities from these tests ranged from about 0.1 ft/d to 2.3 ft/d, with a
geometric mean of 0.7 ft/day (Figure 4-4).
The hydraulic conductivity was measured in the field using numerous slug tests and
one pumping test performed by HDR (2016). Eighty-eight (88) slug tests were
performed in the wells screened in the upper surficial flow zone. Hydraulic
conductivities from those tests ranged from about 0.9 ft/d to 198 ft/d, with a geometric
mean of 47 ft/d and a median of 53 ft/d. (Figure 4-5). Ninety-seven (97) slug tests were
performed in the wells screened in the lower surficial flow zone; hydraulic
conductivities from those tests ranged from about 5 ft/d to 174 ft/d, with a geometric
mean of 74 ft/d and a median of 89 ft/d. The May 2016 HDR pump test (HDR, 2016)
indicated a very high hydraulic conductivity value in the lower surficial flow zone of
370 ft/d, but the extent of the very high permeability zone is not known. (Figure 4-6).
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Twenty-four (24) slug tests were performed in wells screened in the upper Peedee flow
zone (elevations ranging from -70 to -109 feet NAVD 88). Hydraulic conductivities in
the upper Peedee flow zone ranged from 0.003 to 0.37 ft/d, with a geometric mean and
median value of 0.03 ft/d. (SynTerra, 2018) (Figure 4-7). Five slug tests were performed
in wells screened in the lower Peedee flow zone (elevations from -126 to -133 feet
NAVD 88). These hydraulic conductivities ranged from 0.0002 to 0.004 ft/d, with a
geometric mean value of 0.0008 ft/day. (Figure 4-8).
4.3 Flow Model Boundary Conditions
The flow model outer boundary conditions are different for the different flow zones.
The outer lateral boundary conditions for the upper surficial flow zone are almost
entirely constant head (in the Cape Fear River and Northeast Cape Fear River) or drains
(in the swamps), with small areas of no -flow at the north and south ends of the model.
The outer boundary of the model was purposely selected to minimize the no -flow
boundaries, with the nearest model boundary more than a mile from the ash basins. The
deep Peedee confined flow zone (layer 18) was assigned a constant head on the north
and south ends of the model in order approximate the regional gradient. The north
edge of the model was assigned a head of 13 feet NAVD 88, and the south edge of the
model was assigned a head of 10 feet NAVD 88. All other lateral boundaries are no -
flow. The base of the Black Creek aquifer in the model was considered a no -flow
boundary.
4.4 Flow Model Sources and Sinks
Flow model sources and sinks on the interior of the model consist of: recharge, the
cooling pond, marshes, swamps, the Cape Fear River, Northeast Cape Fear River, intake
and discharge canals, ponded water in the 1971 basin, and groundwater pumping.
Recharge is a key hydrologic parameter in the model (Figure 4-9). The calibrated
recharge rate in the upland areas of the model is 16 inches per year. This value falls in
the upper part of the range reported by the USGS for New Hanover County (Bukowski
McSwain et al., 2014). The recharge rate was set to zero in the low swampy areas that
serve as groundwater discharge zones. The recharge rate at the municipal lined landfill
to the north of the industrial plant was set to zero. The recharge rates in both the Sutton
Plant and the offside industrial plant (north to the site) were set to 1 inch per year due
to the large areas of roof and pavement. Recharge in the FADA was set to 1 inch per
year during the calibration process to avoid flooding the top model cells. The recharge
rate during operation of the 1971 and 1984 ash basins was estimated to be 50 inches per
year, dropping to a value of 30 inches per year after sluicing in each basin ended. These
historical recharge rates, however, are uncertain, and the actual value could have been
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higher or lower. The current recharge rate in the 1971 basin, now flooded, was set to
zero, and in the area of the previous 1984 basin, the regional rate of 16 inches per year
was used. The recharge rate in the new ash landfill was set to zero. The recharge rate in
the infiltration pond (stormwater basin) on the northern side of the landfill was set to 54
inches per year, and the recharge rate in the infiltration pond on the southern side was
set to 108 inches per year.
The relatively large sand mines (north sand mine and south sand mine) have been
excavated during the last decade, and these mines are now largely filled with water.
These excavated sand mines were modeled as very high hydraulic conductivity zones
(10,000 ft/d) in model layers 3 through 8, with an enhanced infiltration rate of 36 inches
per year in the north sand mine and adjacent sand pit, and 20 inches per year in the
south sand mine. Because these sand mines are fairly recent, they were not considered
in the historical transport simulations, but they are included in the predictive
simulations and the steady-state flow calibrations. An additional area located just south
of the north sand mines was included as an area of higher recharge with a rate of 20
inches per year to improve the model calibration. Figure 4-9 shows the distribution of
recharge zones in the model. The main area of recharge is the north -south peninsula
between the two rivers.
In the previous calibration efforts, recharge was not adjusted much during the model
calibration process except in the sand mines. The reason for not including recharge as a
main calibration parameter is that for steady-state unconfined flow, the hydraulic heads
are determined primarily by the ratio of recharge to hydraulic conductivity, so the two
parameters are not independent. In situations where the groundwater discharges to a
flow measuring point (for example a gauged stream in a watershed), the flow
measurement can be used to calibrate the recharge value allowing both the recharge
rate and the hydraulic conductivity to be simultaneously calibrated; however, at the
Sutton Site, groundwater discharge is diffuse, and occurs to many different locations in
swamps, marshes, the cooling pond, and the rivers.
The cooling pond, Cape Fear River, Northeast Cape Fear River, an excavated pond east
of Hwy 421, ponded water in the 1971 ash basin, and a sump in the FCPA were treated
as constant head zones in the model using the MODFLOW CHD specified head
package (Figure 4-10). The cooling pond had a pool elevation of 8.32 feet NAVD 88
when it was measured in December 2019. The Cape Fear River and Northeast Cape Fear
River were broken into segments to approximate the average river gradients across the
model domain. Both rivers are tidal, but only the average river stage was used. The
Cape Fear is a major river that is about 30 feet deep in the model area. The constant
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head cells associated with this river were applied to layers 3 through 8 to reflect this
depth. The Northeast Cape Fear River is dredged at the southern end, so constant head
cells were applied to layers 3 through 8 in this area. The remainder of the Northeast
Cape Fear River is shallow, so constant head conditions were only applied to layers 3
through 6 in these areas. The excavated pond east of Hwy 421 was set to a constant
head of 3.5 feet. The ponded water in the flooded 1971 ash basin was set to a constant
head of 8.32 feet.
The swamps and marshes were treated as head -dependent flow sinks called "drains" in
MODFLOW. A "drain" condition uses a specified drain elevation. When groundwater
is present above this specified elevation, it is removed at a rate that is proportional to
the head difference and a specified conductance value. The drains are modeled using
the MODFLOW DRAIN package, in which the drain elevations in the swamps was set
equal to the ground surface elevation from the LIDAR data (Figure 4-10).
As in the previous SynTerra (2015, 2017) models, Plant intake and discharge canals were
simulated using the MODFLOW RIVER package (Figure 4-10). These were previously
simulated as constant head boundaries, with heads equal to the cooling pond, but heads
in several nearby monitoring wells are lower than the cooling pond elevation
suggesting limited hydraulic influence from the canals. The riverbed conductance per
unit area in the Plant intake was set to 0.05 feet squared per day, per foot squared
(ft2/d)/ft2, and Plant discharge canal value was set to 0.1 (ft2/d)/ft2 near the cooling pond,
and 0.01 (ft2/d)/ft2 near the Plant. These conductance values would be consistent with
the presence of a low permeability layer of silt or clay in the canals.
Relatively little information was available about the public and private wells in the
model area. Figure 4-11 shows the location of water supply wells in the model area
(from SynTerra, 2015a). Given the Site hydrogeology, it is almost certain that these wells
are screened in the surficial aquifer. In the model, well screen lengths were assumed to
be 40 feet, with screens extending upward from the approximate base of the surficial
flow zone. Some information was available about recent pumping rates in the CFPUA
wells, the Duke Energy wells, and to a lesser extent, some of the industrial wells
(formally Invista wells). SynTerra (2014) reported average pumping rates of 27 gallons
per minute (gpm) for the two CFPUA wells (wells NHC-SW3 and NHC-SW4).
However, those wells were abandoned in early 2016. Flow rates for the Duke Energy
wells were estimated from data reported to the State through the Water Withdrawal &
Transfer Registration Annual Water Use Reports. (http://www.ncwater.org/
Permits_and_Registration/Water_Withdrawal_and_Transfer_Registration/report). The
most recent pumping rates were only a few gallons per minute, per well.
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According to the 2014 and 2015 Water Withdrawal reports, the Invista plant pumps an
average of about 600,000 to 1 million gallons per day (-400-700 gpm) from wells.
Several possible Invista wells were located, and are reported in the CSA report
(SynTerra, 2015a); however, the names of these wells for the most part do not match the
names given in the Water Withdrawal reports. The two wells that do match the reports
had reported average pumping rates of 56 gpm (Invista G) and 93 gpm (Invista H2)
during 2014. Invista well G is not listed in the 2015 report. There is a high degree of
uncertainty about the actual current and historical pumping rates of these and other
Invista wells in the area. Monitoring wells are now located near most of the former
Invista wells. With the exception of the northern most well (Invista 1), there were not
any indications of localized drawdowns caused by the Invista well pumping in the July
2017 (pre -excavation) and December 2019 (post -excavation) water levels.
A monitoring well cluster, consisting of wells MW-5A, MW-5B, MW-5C, MW-5CD, and
MW-5E, was installed about 4,000 feet north of the 1984 ash basin. Model calibration to
heads in these wells was improved by including pumping from the Invista 1 well at a
rate of 104 gpm in the steady-state flow models for 2017 and 2019. The transient flow
fields used for the pre -excavation and post -excavation transport model include
pumping from Invista well(s).
No pumping rate or historical information was available for the other water supply
wells identified in the model area. These wells were assumed to have constant pumping
rates of 1,000 gallons per day unless they are known to be inactive. Septic return to the
groundwater system was assumed to be 94 percent of the pumping rate, based on
Treece et al. (1990), Daniels et al. (1997) and Radcliffe et al. (2006). Because these wells
are believed to be shallow, the septic return was subtracted from the well pumping
rates in the model.
The Interim Action groundwater extraction system, situated between the new ash
landfill and the sand mines, consists of nine recovery wells that pump at average rates
of 39 gpm to 58 gpm. This system began operation in August, 2017, and is included in
the 2019 flow and transport models.
4.5 Flow Model Calibration Targets
Two steady-state flow models were calibrated, one to represent the period prior to
excavation of the 1971 and 1984 ash basins (pre -excavation) and one to represent 2019
data, when the 1971 and 1984 ash basins have been excavated with the nine extraction
wells are operating (post -excavation). The pre -excavation steady-state flow model
calibration targets were historically averaged water level measurements from 155
observation wells taken from June 2015 through July 2017. The post -excavation flow
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model steady-state calibration targets were determined by using the 2019 fourth quarter
water levels, which consisted of 113 water level measurements from observation wells.
In general, wells with a B designation at the end of the name are screened in the upper
surficial flow zone, those with a C designation are screened in the lower surficial flow
zone, those with a D designation are screened in the upper Peedee flow zone, and those
with an E designation are screened deeper in the Peedee flow zone. Fewer wells were
used in the calibration in the post -excavation model than the in the pre -excavation
simulation due to monitoring wells being abandoned within the footprint of the 1971
and 1984 basin excavations and due to construction of the lined landfill.
Water levels used for the pre -excavation calibration were determined by taking the
time -average value for head data. Water levels are expected to vary on an annual period
due to seasonal changes in recharge. These fluctuations in water level are not simulated
because the flow model is a steady state model. The average water level values are the
best available estimates of the steady state hydraulic heads, so they were used for the
pre -excavation calibration.
The historical water levels measured from June 2015 through July 2017 were on average
0.94 feet higher than those measured in December 2019. These decreased water levels
are likely due to excavation of the 1971 and 1984 ash basin area where water table
mounding no longer occurs, and due to operation of the nine groundwater extraction
wells. These effects are captured in the 2019 flow model.
4.6 Transport Model Parameters
The transport model uses a transient MODFLOW simulation to provide the time -
dependent groundwater velocity field. One transient MODFLOW simulation started
January 1971 and continued through July 2017 to represent the period prior to
excavation, and a second model started in July 2017 and runs through December 2019 to
represent post -excavation conditions. The Sutton Plant began operations in 1954, and it
used cooling water directly from the Cape Fear River. Coal ash from this time period up
through 1971 was sent to the FADA. In about 1971, major changes were made to the
Sutton Site. The 1,100-acre cooling pond (Sutton Lake) was built with intake and
discharge canals that run adjacent to the FADA, and the 1971 ash basin was built. Since
these 1971 features have dominated the groundwater flow and transport at the Site for
more than 40 years, it was decided to start the transient model in 1971.
The actual history and development of the 1971 and 1984 ash basins are complex as they
evolved over the course of more than 40 years; however, the basic footprints of the
basins appear to have been established during initial construction. The transient flow
model simulates the basins as having a constant footprint over time. As was discussed
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earlier, the basin infiltration rate during sluicing is not known, but it was estimated by
taking the results of the calibrated steady-state flow model (discussed in Section 5.1)
and adjusting the infiltration rate to better reproduce the boron and selenium transport.
The final basin recharge rates used during sluicing in the transient flow model are 50
inches per year. Although the 1971 basin continued to receive ash after 1984, the
infiltration rate was reduced to 30 inches per year after 1984 because much of the ash
was sluiced to the 1984 basin (through 2013). These basin infiltration rates are much
smaller than the rate of water inflow to the basins with the sluiced ash.
The pre -excavation transient flow field was modeled as three successive steady-state
flow fields: one corresponding to the high infiltration rate in the 1971 basin during ash
sluicing from 1971 to 1984 when that was the only basin in operation, one
corresponding to the higher infiltration rate in the 1984 basin during ash sluicing from
1984 to 2013, and one corresponding to the basin infiltration rates from 2013 to 2017.
The post -excavation transient flow field was modeled as one steady-state flow field
from 2017 through 2019, and it includes the nine extraction well system.
The key transport model parameters are the constituent source concentrations in the
FADA, FCPA, FPA, and ash basins and the constituent soil -water distribution
coefficients (Kd). Secondary parameters are the longitudinal, transverse, and vertical
dispersivities and the effective porosity. The constituent source concentration in the
FADA and 1971 ash basin were estimated from measured ash pore water concentrations
in monitoring wells (SynTerra, 2015a) and were adjusted during the transport model
calibration. The COI source concentrations in the 1984 ash basin were assumed to be
similar to those in the 1971 basin, but the 1984 basin was split into three zones during
the transport model calibration. The COI source concentrations in the FPA and FCPA
areas were calibrated based on concentrations in the nearby observation wells.
Historical changes in concentration are poorly constrained (no historical concentration
data), so it was assumed that source concentrations change in simple steps that
correspond to the times of ash basin construction and sluicing, post sluicing operation,
and post excavation.
Linear adsorption Ka values for COIs at Sutton were measured in the laboratory using
core materials from the coal ash, the surficial flow zone sediments, and the Peedee
Formation (Langley et al., 2015). In general, the measured Ka values for the constituents
were highly variable, and the variability within a given material type (for example the
surficial flow zone sediments) was larger than the variability between different
materials. The measured Kd value for boron ranged from -0 to 1,100 mL/g. The
measured Ka value for selenium ranged from 2 mL/g to 107 mL/g. Geochemical
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modeling (SynTerra 2020, Appendix G) under a range of current and future Site
conditions predict a high selenium Kd value, with all simulations resulting in Kd greater
than 10 mL/g.
. The predicted Kd values for boron were all low, with Kd less than 0.1 mL/g in all
simulations. Selenium was predicted to have
In light of the variability of the measured Kd values, it was decided that a conservative
approach would be used for the Kd values in the model. A uniform Kd value is used
throughout the model for each COI. The initial value used in calibration was the
minimum measured value from Langley et al. (2015). The boron and selenium Kd values
were adjusted during the previous transport model calibration (Attachment C,
Geosyntec, 2017b). The final Kd value used for boron was 0.01 mL/g which is similar to
values predicted by the geochemical modeling (SynTerra, 2020, Appendix G). Selenium
is mainly found in the northern part of the 1984 basin. A very low Kd value of 0.5 was
needed to reproduce observed selenium transport in this area. This Kd value is much
lower than what is predicted by the geochemical model.
A sensitivity analysis to further evaluate the effect of Kd values on COI transport is
given in Section 5.5. The longitudinal dispersivity was assigned a value of 50 feet, the
transverse dispersivity was set to 5 feet, and the vertical dispersivity was set to 0.05 feet.
The radial flow from the ash basins and the high rate of infiltration result in a large
degree of mixing in the boron plume. The additional effects of mechanical dispersion
were small. The effective porosity was assumed to be uniform, but the value was
adjusted during the transport model calibration process in the SynTerra (2016a) model
to a final value of 0.3 in order to better reproduce the observed boron distribution. The
soil dry bulk density was set to 1.6 grams per milliliter (g/mL).
4.7 Transport Model Boundary Conditions
The transport model boundary has no -flow conditions on the exterior edges of the
model except where constant head boundaries exist [specified as a concentration of 0
µg/L]. All of the constant head surface water bodies have a fixed concentration of 0
µg/L. As water containing dissolved constituents enters these zones, the dissolved mass
is removed from the model. Infiltrating rainwater is assumed to lack COIs, and it enters
from the upper active layer of the model.
The initial condition for the pre -excavated conditions transport model is zero
concentration of COIs in groundwater. No background concentrations are considered.
The COI concentrations in the 1971 ash basin, FADA, and FPA are assumed to be at the
observed concentrations at the start of the simulation (year 1971). The COI
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concentrations in the 1984 ash basin are zero at the start of the simulation and they
increase to the source concentrations in 1984 when the ash basin was constructed.
4.8 Transport Model Sources and Sinks
The ash basins, FADA, FPA, or the FCPA are the sources of boron and selenium in the
model. Sources from the ash basins are simulated by holding the COI concentration
constant in cells located immediately under the ash basins (layers 3-6). This allows
infiltrating water to carry dissolved constituents from the ash into the groundwater
system in the model. Sources within the FADA and FCPA, are simulated by holding
boron and selenium concentrations constant in the upper surficial layer
(layers 3-6) in the historical transport models. The FPA is simulated by holding boron
and selenium concentrations constant in the upper surficial layer (layers 3-4) in the
historical transport models to represent ash excavated in the first 8 feet below ground
surface. The model COI sources were placed immediately below the coal ash because
the ash was located above the water table for most of the area. The concentration was
also specified in model layers 7-12 in a zone beneath the 1971 ash basin to represent the
deep ash below the water table in the area that was excavated prior to construction of
that ash basin.
The transport model sinks are the lakes, marshes, swamps, and rivers represented in the
flow model using a general head boundary condition. As groundwater enters these
features, it is removed from the groundwater system along with dissolved COI mass.
Similarly, COI mass is removed when COIs are transported to extraction wells.
4.9 Transport Model Calibration Targets
Two transport models were calibrated: one to represent the period from 1971 through
2017, prior to excavation of the ash basins and operation of the nine groundwater
extraction wells (pre -excavation), and one to represent transport between 2017 and 2019
with ash basins excavated and the operation of nine extraction wells (post -excavation).
The 1971-2017 transport model calibration targets are COI concentrations measured in
150 monitoring wells in the second quarter of 2017. The post -excavation transport
model calibration targets are COI concentrations measured in 148 monitoring wells in
the fourth quarter of 2019. All sampled wells are included in the calibrations.
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5.0 MODEL CALIBRATION TO CURRENT CONDITIONS
5.1 Flow Model Calibration
The flow models were calibrated in stages starting with the pre -excavation model
(2017). This effort started with the previous 2017 model (Attachment C, Geosyntec,
2017b), with refinements to better reproduce field data collected since then. Major
physical changes occurred at the site between about 2016 and 2019, including
excavation of the ash basins, construction of the lined landfill, and installation and
operation of nine extraction wells along the eastern Site boundary. These changes are
incorporated in the 2019 flow model, which uses the same hydraulic conductivity
structure and background recharge rate as the 2017 flow model. The two models were
calibrated in an iterative fashion, by making sure that any model adjustments allowed
both models to reproduce the observed water levels in observation wells.
The flow models were further refined during calibration of the 1971-2017 (pre -
excavation) and 2017-2019 (post excavation) transport models. As these transport
models were calibrated to reproduce boron and selenium concentrations in observation
wells, some additional changes were made to the hydraulic conductivity fields. As this
was done, the 2017 and 2019 steady state flow models were updated to make sure that
the flow calibrations remained accurate.
The final hydraulic conductivity zones used in the 2017 flow model are shown in
Figures 5-1 through 5-5, and the calibrated hydraulic conductivity values assigned to
each zone in each layer are listed in Table 5-1. The hydraulic conductivity assigned to
areas that were excavated between 2017 and 2019 (ash basins and sand mines) was
increased to very large values (10,000 ft/d or more) in the 2019 flow model, but the
hydraulic conductivity field was otherwise identical to the 2017 flow model.
Zones where hydraulic conductivity differs from regional values occur primarily in the
lower surficial model layers, where the 2016 HDR pumping test was conducted (HDR,
2016), and where the nine well extraction system was installed, and the discontinuous
Peedee confining layer to the south (Figures 5-3a and 5-3b).
In model layers 11-12 which represent the lower surficial zone, one zone of increased
hydraulic conductivity, zone 5, has hydraulic conductivity approximately six times
greater than baseline values of surrounding material (125 ft/d) (Figures 5-3a and 5-3b
and Table 5-1). This zone reflects the area of high hydraulic conductivity identified
during the HDR pumping test (HDR, 2016). It was found necessary to extend this zone
of high hydraulic conductivity to the northeast in order to reproduce the limited
observed water level drawdown that has occurred in response to the groundwater
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extraction from the nine extraction wells. These wells remove water at an average long-
term combined rate of 460 gpm, but produce only a limited cone of water level
depression. These observations are only possible with very high hydraulic conductivity
in the area.
A small zone of somewhat lower hydraulic conductivity was applied to the southern
end of the extraction wells and east of the FPA (Figures 5-3a and 5-3b). This zone was
added to reflect the lower pumping rate of extraction well EW-1 and the larger
drawdown seen in this part of the well field. It also improved the COI transport model
calibrations.
In the 2019 post -excavation flow model, the new lined landfill had an applied recharge
rate of zero to reflect the landfill lining. The stormwater retention ponds on the
northeast and south sides of the landfill were assigned high infiltration rates (54 and 108
inches per year). These stormwater retention ponds collect water that runs off from the
landfill cap. The infiltration rates assigned to these ponds approximately corresponds to
one half of the rainfall that falls on the landfill cap.
The ash layers in the 1971 and 1984 basin were set to 1,000 ft/d to simulate excavation.
The deep coal ash beneath the 1971 basin was simulated using a high conductivity zone
(10,000 ft/d) in the upper surficial flow zone (layers 3 through 8) to reflect the effects of
excavation and dredging. The north and south sand mines were simulated using very
high conductivity zones (10,000 ft/d to 30,000 ft/d) in the upper surficial flow zone
(layers 3 through 8). Use of these extremely high conductivity values in excavated areas
improved the model calibration. The hydraulic conductivity zones are shown in
Figures 5-6 through 5-8 and Table 5-2. The Peedee flow zones in the post -excavation
model are the same as the pre -excavated model and can be found in Figures 5-4 and
5-5.
The resulting distribution of hydraulic conductivity reproduces to both observed heads
and concentrations. The calibrated pre -excavation flow model has a mean head residual
of -0.29 feet and a root mean squared head residual of 0.54 feet. The total span of
historical average head ranges 8.3 feet, from approximately 4.4 feet NAVD 88 to 12.7
feet NAVD 88. Using this range to normalize the residual gives a normalized root mean
square error of 0.065 (6.5 percent). A comparison of the observed and simulated
hydraulic heads for the pre -excavated model is listed in Table 5-3, and the observed
and simulated heads are cross -plotted in Figure 5-9. Most of the residuals between
predicted and observed heads are less than 1 foot, one residual is between 1 and 2 feet,
and two residuals (well AW-07R-D and MW-31R-C) are greater than 2 feet
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(Figure 5-10). The flow field in the calibrated pre -excavated model can be found in
Figure 5-11.
The calibrated post -excavation flow model has a mean head residual of 0.07 feet and a
root mean squared head residual of 0.66 feet. The total span of post -excavation average
head ranges 7.3 feet from approximately 2.9 feet NAVD 88 to 10.2 feet NAVD 88. Using
this range to normalize the residual gives a normalized root mean square error of 0.091
(9.1 percent). A comparison of the observed and simulated hydraulic heads for the post -
excavated model is listed in Table 5-4, and the observed and simulated heads for the
post -excavation simulation are cross -plotted in Figure 5-12. Most of the residuals
between predicted and observed heads are less than 1 foot, fifteen residuals are from 1
to 2 feet, and none are greater than 2 feet (Figure 5-13). The flow balance errors in the
models are less than 0.01 cubic foot per day (ft3/d), which is a volume balance error of
less than 10-4. The flow field in the calibrated post -excavated model can be found in
Figure 5-14.
Prior to excavation of the basins (pre -excavation) and operation of the nine extraction
wells, a local groundwater divide occurred within the 1971 basin heading north east to
the sand mines, according to simulations (Figure 5-11). The local divide extended
roughly northeast -southwest along the topographic high between the Cape Fear River
and Northeast Cape Fear River. The 1971 basin discharged to the plant discharge canal
and to the cooling pond. This local divide was primarily due to elevated heads within
the ash basins caused by historical sluicing which created a radial mounding effect. The
north and south sand mines were also at a higher elevation prior to mining activities
which cause a higher hydraulic head within those areas.
Following excavation of the basins and the startup of the nine extraction well system, a
local groundwater divide occurs within the sand mines, according to simulations
(Figure 5-14). The local divide shifts to the east of the 1971 ash basin and runs northeast -
southwest along the topographic high and is parallel between the Cape Fear River and
Northeast Cape Fear River. Groundwater within the sand mines flows primarily to the
east and west, discharging to the cooling pond or toward the Northeast Cape Fear
River. This local divide is primarily due to the lowered topography of the 1971 and 1984
basins after excavation and strong hydraulic control from the extraction well system
along the western Site boundary.
5.2 Flow Model Sensitivity Analysis
A parameter sensitivity analysis was performed on the pre -excavation and post -
excavation calibrated flow models by systematically increasing the parameters by a
factor of 2, decreasing them by a factor of 2, and then recalculating the heads and the
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NRMSE values (Tables 5-5 and 5-6). The baseline hydraulic conductivity values and
recharge rate, which are the primary hydraulic parameters, were varied in this study.
The NRMSE of the pre -excavation and post -excavation flow models showed the highest
degree of sensitivity to regional recharge and surficial flow zone hydraulic
conductivity. There was a moderate sensitivity to the hydraulic conductivity of the
Peedee flow zone. For the pre -excavation simulation, the NRMSE was weakly sensitive
to the hydraulic conductivities of the ash. The ash was not evaluated in the post -
excavation model because the 1971 and 1984 ash basins are excavated.
5.3 Historical Transport Model Calibration
The historical 1971-2017 (pre -excavation) transient flow model used for transport
simulations includes three steady-state flow fields: one that represents the period when
the 1971 ash basin was in operation (1971-1984), one that represent the period when the
1971 and 1984 ash basins were in operation (1984-2013), and one after the end of ash
sluicing but prior to the 1971 and 1984 basin excavation (2013-2017). The post -
excavation transport simulation (2017-2019) includes one steady-state head field that
represents the ash excavation in the 1971 and 1984 ash basins, construction of the lined
landfill, and the operation of the nine extraction well system.
The pre -excavation model was set up so that the three steady-state head simulations
were used in a single transient transport simulation. The model allows the boundary
conditions in the head simulations to change with time. The flow model specified the
recharge on the FADA,1971 basin, the 1984 basin, an area south of the north sand mines
in order to simulate pre -excavation Site conditions. A recharge value of 60 in/yr (0.0137
ft/d) was used in the 1971 basin during the initial period (1971-1984) and the 1984 basin
during the second period (1984-2013); this value is greater than the ambient recharge of
16 in/yr (0.00365 ft/d). The larger value was used to simulate the increased recharge that
would occur during sluicing in the basins. The recharge at the basins were decreased to
30 in/yr (0.00685 ft/d) when sluicing stopped, and it was decreased further when the
landfill was created in 2017.
The post -excavation transport model runs from 2017 to 2019 and was set up so that one
steady-state head simulation was used in a single transient transport simulation. The
flow model specified the recharge on the lined landfill, 1971 basin, 1984 basin, FADA,
north and south stormwater basins, north and south sand mines, and the area south of
the northern sand mine. A recharge rate was set to zero on the lined landfill to represent
the lack of water infiltrating the landfill. A recharge rate of zero and a head of 8.32 feet
NAVD 88 was applied to the 1971 ash basin to represent ponded water after excavating
(dredging) below the water table to a depth of approximately 40 feet. Within the north
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and south stormwater basins, the north and south sand mines, and the area south of the
northern mine, a recharge rate greater than the ambient region of 20 in/yr to 55 in/yr
(0.00457 ft/d to 0.0124 ft/d). A high hydraulic conductivity (10,000 ft/d) was used in the
sand mines to simulated ponded water.
An alternative approach to modeling the sand mine water bodies would be to treat
them as constant head boundary conditions. These sand mines are located close to the
nine extraction well system, and much of the water reaching the wells originates in the
sand mine ponds. Treating these as constant head sources would result in an infinite
supply of water to the wells with no effect on the water levels in and around the ponds.
Treating the sand mine ponds as high conductivity zones allows water to readily flow
into and out of the ponds, but the water balance with the groundwater system and the
extraction wells is maintained in a more realistic way. The recharge at the 1984 basin
was decreased to ambient values in the post -excavation simulation to represent the
basin being excavated.
The hydraulic head in the cooling pond was maintained at an elevation of 8.32 feet
NAVD 88 throughout the pre -excavation and post -excavation simulations. The cooling
pond water elevation was measured in December 2019 by Duke Energy.
The COI source concentrations in the ash basins, FADA, FPA, and FCPA are the
primary calibration variables in the 1971-2017 pre -excavation transport simulation. The
constituent source concentration in the FADA and 1971 ash basin were estimated from
measured ash pore water concentrations in monitoring wells (SynTerra, 2015a, 2016b)
and were adjusted during the transport model calibration. The COI source
concentrations in the 1984 ash basin were assumed to be similar to those in the 1971
basin, but the 1984 basin was split into three zones during the transport model
calibration. The COI source concentrations in the FPA and FCPA areas were calibrated
based on concentrations in the nearby observation wells. Historical changes in
concentration are poorly constrained (no historical concentration data), so it was
assumed that source concentrations change in simple steps that correspond to the times
of ash basin construction and sluicing, post sluicing operation, and post excavation.
The COI source zone calibration process resulted in source zones with concentrations as
shown in Figure 5-15a and Tables 5-7a and 5-7b.
In the 1971-2017 pre -excavation transport simulation, COI concentrations in the 1971
basin were assumed to be constant until 1984 and equal to the values determined
through calibration. The FADA and FPA have constant COI source concentrations from
1971 to 2017 determined through calibration. COI concentrations in ash were assumed
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to be zero in the 1984 basin from 1971-1984 because the basin was not in operation at
this time. COI concentrations were assumed to increase to the values used for
calibration in 1984. These values are maintained from 1984 to 2013 and decreased after
2013, when sluicing was terminated.
In the 2017-2019 post -excavation simulation, all of the specified COI concentration
zones are removed, and a COI concentration of zero was applied to ash layers 1 through
2 in the 1971 and 1984 basins to represent the ash that was excavated. A zero
concentration within the model layers 9-12 of the 1971 ash basin was applied to
represent deep dredging (Figure 5-15b). The COI starting concentrations in the
remainder of the model domain are from the 1971-2017 historical transport simulation.
As the transport models were calibrated, it was necessary to adjust some aspects of the
flow model in order to reproduce the observed COI distribution. These changes were
done in an iterative way so that the flow model calibration accuracy was maintained.
Hydraulic conductivity values were adjusted to help calibrate the simulated boron and
selenium concentrations to site data. The model COI calibration focused on reproducing
the observed extent of concentrations that are above the 02L standards.
The Ka value is also considered as a calibration variable in the transport simulations. Ka
values were adjusted to help improve the simulated boron and selenium concentrations
to site data. Adjusting Ka values had an effect on COI distributions; however, adjusting
source concentrations and hydraulic conductivity was a more effective calibration tool
for improving transport model fit to data.
Results of the calibrated pre -excavation transport simulation COI extent reproduce
most of the observed COI concentrations obtained through the second quarter of 2017.
As previously mentioned in Section 2.7, the Peedee Formation (or flow zone) is affected
by saltwater intrusion with natural occurring boron concentrations higher than the 02L
standard (SynTerra, 2018). Monitoring wells screened at elevations approximately -70
feet NAVD 88 and below are within the Peedee flow zone and were not calibrated for
boron in the model. Monitoring wells that are screened within the Peedee flow zone,
typically monitoring wells with designations "D" and "E", were not calibrated for
boron.
Pre -excavation model concentrations of boron and selenium in non -ash layers are
shown in Figures 5-16a and 5-16b and Tables 5-8a and 5-8b. Some of the observation
wells where COIs were detected are in areas where the predicted concentration
gradients are steep (beneath or adjacent to the ash basins, for example), so small
changes in location similar to the dimension of a grid block result in significant changes
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in concentration. This is one factor that explains the differences between predicted and
observed concentrations.
Simulated boron concentrations in the surficial zone reasonably reproduce the observed
concentrations in most areas. The model predicts limited boron migration in the upper
surficial flow zone, with more extensive migration to the east in the lower surficial flow
zone. Along the eastern property line of the Site, monitoring wells (MW-31C and MW-
31RC) detected boron concentrations greater than the 02L standard. For boron to
migrate towards these wells, a high hydraulic conductivity of 800 ft/d was used within
the lower surficial model zone. This high hydraulic conductivity is consistent with the
HDR pumping test conducted in 2016, and with the modest hydraulic head drawdown
that occurs in response to operation of the nine well extraction system. Monitoring well,
SMW-01C, detected boron concentrations slightly greater than the 02L standards,
however the model calibration did not predict concentrations to migrate that far to the
east even with a high hydraulic conductivity of 800 ft/d in the lower surficial flow zone.
The calibrated model predicted boron concentrations above the O2L standard in
monitoring wells along the southern berm and western berm of the 1971 and 1984 ash
basins where observed boron concentrations are greater than the 02L standard.
However, other monitoring wells (CCR-102B, CCR-106B, CCR-107B, CCR-107C, CCR-
108B, CCR-108C, and CCR-109B) along this area detected concentrations below the 02L
standard. Within the FADA, monitoring well ABMW-02B detected boron
concentrations less than the 02L standard, however the model predicted boron
concentrations slightly greater than the 02L standard. The NRMSE for the boron
calibration is 0.0183 (18.3 percent). The pre -excavated calibrated maximum
concentrations of boron in non -ash layers are shown in Figure 5-16a.
The 2017 transport model predicts limited selenium transport to the north and east of
the northern portion of the 1984 ash basin. The vertical extent of selenium
concentrations in excess of the 02L is limited to the surficial flow zone. The NRMSE for
the selenium calibration is 0.106 (10.6 percent). Selenium was detected at greater than
the 02L standard in four monitoring wells (CCR-114C, MW-27C, MW-36C, and
MW40C), which is reflected in the 2017 pre -excavation model. The pre -excavated
calibrated maximum concentrations of selenium in non -ash layers are shown in Figure
5-16b.
The post -excavated calibrated maximum concentrations of boron in non -ash layers are
shown in Figure 5-17a and Table 5-9a. Results of the calibrated post -excavation
transport simulation COI reproduces most of the observed COI concentrations obtained
from the fourth quarter of 2019 (Figure 5-17a). Figure 5-17a displays monitoring wells
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that detected boron concentrations greater than the 02L standard compared to the
simulated boron concentrations. The model predicts limited boron migration in the
surficial flow zone, with boron receding to the west towards the nine extraction well
system. The model simulates boron concentrations greater than the 02L standard to the
east of the eastern compliance boundary, however boron concentrations from 18 of 21
monitoring wells on or within the eastern compliance boundary were less than the 02L
standard. The two monitoring wells within the compliance boundary where boron was
detected at concentrations greater than the 02L standard were CCR-120C and CCR-
122C (1000 µg/L and 1070 µg/L). Sixteen (16) monitoring wells east of the compliance
boundary along the eastern property line also detected boron concentrations less than
the 02L standard. Thus, the simulated boron concentrations to the east of the
compliance boundary is a conservative maximum extent. Similar to the pre -excavation
model, east of the compliance boundary monitoring well (SMW-01C) detected boron
concentrations slightly greater than the 02L standard; this was not predicted in the
model. Boron concentrations were simulated to migrate towards two monitoring wells
(MW-45C and MW-46C) to the south and west of the FADA. The two monitoring wells
detected boron concentrations greater than the 02L standard and boron is predicted to
migrate towards the Cape Fear River. Eight out of the twelve monitoring wells along
the western berm of the 1984 ash basin detected boron concentrations greater than the
02L standard. The four monitoring wells (CCR-113B, CCR-113C, CCR-114B, and CCR-
114C) detected boron concentrations below the 02L standard, however simulated boron
concentrations predicted concentrations greater than the 02L standard. The NRMSE for
the boron concentration is 0.092 (9.2 percent).
The post -excavation model predicts limited selenium transport to the north and east of
the northern portion of the 1984 ash basin (Figure 5-17b and Table 5-9b). The vertical
extent of selenium concentrations greater than the 02L is limited to the surficial flow
zone. The NRMSE for selenium is 0.171 (17.1 percent). Four monitoring wells CCR-114C
IMP, CCR-115C IMP, and MW40C all detected selenium greater than the 02L standard,
which is reflected in the post -excavation model. The model predicts selenium
concentrations greater than 2L approximately 450 feet beyond the compliance boundary
to the west of the 1984 northern corner under the cooling pond.
5.4 Transport Model Sensitivity Analysis
A parameter sensitivity analysis was conducted to evaluate the effects of Kd on the
NRMSE. Kd is assumed to be uniform across the model. The sensitivity analysis was
performed on the 2017 pre -excavation and 2019 post -excavation calibrated transport
models by systematically increasing and decreasing COI Kd values by a factor of five
from their calibrated values. The model was then run using the revised Kd values, and
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the NRMSE was calculated for the sensitivity analysis and compared to the NRMSE for
the calibrated model. It should be recognized that the NRMSE is an imprecise measure
of model accuracy when applied to predicted concentrations. The NRMSE is weighted
towards matching the greatest concentrations, so that the error between an observed
value of 1000 µg/L and a predicted value of 2000 µg/L is the same as the error between
an observed value of 0 µg/L and a predicted value of 1000 µg/L. In the latter case, the
simulation would be greatly over -predicting the concentration, but the NRMSE would
be the same as that of the case in which the prediction was off by a factor of 2. For this
reason, it is important to look beyond the NRMSE, and compare the predicted and
observed extents of contamination.
The pre -excavation calibrated transport model simulated COI concentrations with
NRMSE values of 18.3 percent for boron (Table 5-10) and 10.6 percent for selenium.
Decreasing the boron Kd by multiplying by a factor of one -fifth and increasing the boron
Ka by five times maintains the same NRMSE at 18.3 percent (Table 5-10), due to its very
low value. Increasing or decreasing the boron Kd by a factor of 5 still results in a small
Ka value, and a retardation factor close to 1.
Decreasing the selenium Kd a factor of five increases the NRMSE to 11 percent.
Increasing the selenium Ka by five times decreases the NRMSE to 8.7 percent, however
the model did not predict migration horizontally to monitoring well MW-36C with a
field concentration of 37.3 µg/L. The sensitivity analysis results indicate that the Kd
values used for boron and selenium are near optimal values. It also suggests that the
average difference between simulated and observed COI concentrations is only
moderately affected by changes in the Kd values although they affect the extent of
predicted COI concentrations.
The post -excavation calibrated transport model simulated COI concentrations with
NRMSE values of 12.9 percent for boron and 17.1 percent for selenium (). Decreasing
the boron Kd by multiplying by a factor of one -fifth decreases the NRMSE to 12.5
percent, and increasing the boron Kd by five times maintains the NRMSE at 12.9 percent
(Table 5-11).
Decreasing the selenium Kd by a factor of five decreases the NRMSE to 16.6 percent,
however the simulation predicts concentrations greater than the 02L standard in CCR-
113B, CCR-113C, and CCR-113D which all have measured concentrations below the
detection limit. Increasing the selenium Kd by five times decreases the NRMSE to 15.9
percent, however the simulation predicts selenium with double the concentration than
observed at one monitoring well (CCR-114C IMP). The sensitivity analysis results
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indicate that the Kd values used for boron and selenium are near optimal values. It
also suggests that the average difference between simulated and observed COI
concentrations is only moderately affected by changes in the Kd values.
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6.0 PREDICTIVE SIMULATIONS OF CLOSURE SCENARIOS
Two types of model simulations were used to predict COI distributions after the source
areas were removed. The first type of model used the 2019 post -excavation calibrated
model, as described in Section 5, as an initial condition and ran future conditions to
evaluate various potential corrective actions. The calibrated model was used to evaluate
monitored natural attenuation (MNA), a nine extraction well system and MNA, and a
pump and treat system.
The second type of model was a predictive simulation in which there was initially no
COI distribution within the groundwater; it used synthetic precipitation leaching
protocol (SPLP) concentration data from unsaturated soil samples within the 1984 ash
basin to predict the effect of leaving the existing unsaturated soil in place in accordance
with the basin closure excavation soil sampling plan (Duke Energy, 2018).
The various types of model simulations are intended to show the key characteristics of
groundwater flow and constituent transport that are expected from the closure actions
and/or potential corrective actions.
6.1 Simulation of Future Conditions with MNA and Corrective
Actions
This first type of model begins with the 2019 post -excavation COI distributions
produced by the transport model calibrations. Three scenarios are simulated: one with
MNA alone; one with corrective action consisting of continued operation of the nine
extraction wells for a period of five years followed by MNA; and one with pump and
treat for thirty years. The modeling process includes simulating the FADA and FPA
excavation which involves excavating and placing ash in an on -Site lined landfill. The
COI concentrations in the excavated parts of the FADA and FPA are set to zero, and the
hydraulic conductivity is assigned a value of 10,000 ft/d.
Excavation of the FADA began in July 2019 and was completed by June 2020. The FPA
began excavation in February 2020 and was completed by April 2020. The geometry of
the excavated zones in the model was based on the most recent Geosyntec lay of the
land area (LOLA) closure designs for the FADA and the closure designs for the FPA
(Figures 6-1 and 6-2; Geosyntec 2017c, 2020).
The flow model uses a specified head (8.32 feet NAVD 88) in the FADA to simulate the
post -excavation Site conditions. The hydraulic head distribution was recalculated with
these changes, and used in the predictive transport simulations. This interaction altered
the groundwater flow and the transport of dissolved compounds.
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Three scenarios are simulated: one with MNA alone; one with corrective action
consisting of continued operation of the nine extraction wells for a period of five years
followed by MNA; and one with pump and treat for thirty years. The MNA model was
conducted without corrective action to predict the change in COI concentrations and
distribution due to natural attenuation after the 2020.
The second simulation includes the corrective action consisting of continued operation
of the nine extraction wells system running for five years. This is when the basis of
design (BOD) decommissioning requirements are anticipated to be met. The corrective
action simulation begins in 2020 and runs for five years, ending in 2025. After 2025, the
Site is subject to MNA.
The third model incorporates a pump and treat simulation that consists of 51 extraction
wells and 33 clean -water infiltration wells running for approximately 30 years within
the 1984 ash basin footprint, FADA footprint, and FCPA footprint.
6.1.1 MNA Model
Figure 6-3 shows the simulated hydraulic head distribution after the nine well
extraction system ceases operation. The hydraulic head rises approximately 2 feet
at the location of the nine well extraction system along the eastern property line.
The horizontal head gradient creates a groundwater divide from the north sand
mine to the south sand mine, parallel to the Cape Fear River and Northeast Cape
Fear River. Groundwater flow directions at the Site flow primarily to the west
within the 1984 ash basin and southwest of the FADA (Figure 6-3). The pattern of
the groundwater flow changes in response to Site geometry changes. Site
geometry changes include the excavation of the 1971 and 1984 ash basins, the
lined landfill installation, the off -Site sand mine excavation, and the termination
of the nine well extraction system.
Boron concentrations greater than the 02L standard (700 µg/L) beyond the
compliance boundary are predicted to occur along the eastern, west, and
southwest side of the Site in 2030. (Figure 6-4a). Boron concentrations greater
than the 02L standard in the upper and lower surficial flow zones occur along
the western side of the ash basins and south of the former 1971 ash basin. Boron
concentrations greater than the 02L standard in the lower surficial flow zone
occur to the west of the Site, south of the former 1971 ash basin, and east of the
compliance boundary within the Site property boundary.
Ten years after the FADA and FPA excavation (2030), boron concentrations
greater than the 02L standard are within the eastern compliance boundary and
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occur west and south of the compliance boundary (Figure 6-4a). Boron
concentrations greater than the 02L standard remain in these two areas, slightly
greater than the 02L standard, until approximately 2730, under the current or
future cooling pond (Figures 6-4b through 6-4d). In 2730, boron concentrations
are predicted to be greater than the 02L standard south of the former 1971 ash
basin and north of the former FADA. The simulation was conducted until 2730,
at which time there is still a zone of boron with a maximum concentration of
approximately 1,000 µg/L beyond the compliance boundary, slightly south of the
former 1971 ash basin and south of the effluent discharge canal. While some
boron persists above the 02L standard in this location, the predicted
concentration is well below the 4,000 µg/L tap water regional screening level
(RSL) (USEPA, 2020). At the time of CAP Update preparation, NCDEQ is
reviewing a revised 02L standard of 4,000 µg/L for boron. Furthermore, this area
of predicted persistent boron occurs in hydraulic stagnation zone that is present
in the steady-state flow model that was used for this simulation. The steady-state
flow assumption does not consider the short and long-term transient flows that
will occur in response to weather and climate variations over the several
hundred year simulation. These flow transients would be expected to result in
additional mixing in the stagnation zone, resulting in dilution of the boron there.
Selenium concentrations greater than the 02L standard beyond the compliance
boundary occur west of the former 1984 ash basin within the future cooling pond
after 10 years (Figure 6-5a). The selenium concentrations west of the former 1984
ash basin extends approximately 300 feet west of the compliance boundary. The
maximum concentrations of selenium occur below and downgradient of the
northern section of the former 1984 ash basin source area. Selenium is predicted
to be within the compliance boundary in approximately 20 years (year 2040)
Figure 6-5b.
The 02L standard is 700 µg/L for boron, and 20 µg/L for selenium. The tap water
RSL for boron is 4,000 µg/L (USEPA, 2020). At the time of CAP Update
preparation, NCDEQ is reviewing a revised 02L standard of 4,000 µg/L for
boron. The BTV for selenium is 139 µg/L.
6.1.2 Nine Extraction Wells
This corrective action model considers continued operation of the nine well
extraction system for five years (until the year 2025), followed by MNA. This
operation reflects the anticipated BOD decommissioning requirements being met
within five years of the CAP Update submittal. The reasoning is that the most
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recent interim action plan (IAP) sampling event did not detect off -Site
concentrations greater than 02L/IMACs. In this simulation, the pumping rates of
the nine extraction wells were the same as the 2019 model calibration simulation,
reflecting the long term average pumping rates observed to date. Figure 6-6
shows the hydraulic heads with continued operation of the extraction well
system. The head distribution is similar to the 2019 calibrated model hydraulic
heads, with the exception of the FADA area, which has a flattened head
representing the expansion of the cooling pond after the FADA excavation.
Hydraulic control is still maintained from the nine extraction wells during the
five-year corrective action time period.
Once the extraction wells cease operation, the hydraulic head rises
approximately 2 feet in the upper surficial, lower surficial, and upper Peedee
flow zones where the nine extraction wells were previously located. The
hydraulic heads are identical to the MNA model (Figure 6-3).
Boron concentrations greater than the 02L standard (700 µg/L) beyond the
compliance boundary are predicted to occur along the eastern, west, and
southwest side of the Site in 2030. (Figure 6-7a). Boron concentrations greater
than the 02L standard in the upper and lower surficial flow zones occur along
the western side of the ash basins and south of the former 1971 ash basin. Boron
concentrations greater than the 02L standard in the lower surficial flow zones
occur to the east of the compliance boundary within the Site property boundary.
Ten years after the FADA and FPA excavation (2030), boron concentrations
greater than the 02L standard are within the eastern compliance boundary and
occur southwest of the compliance boundary (Figure 6-7a). Boron concentrations
greater than the 02L standard remain in this area, slightly greater than the 02L
standard, until approximately 2730, under the current or future cooling pond
(Figures 6-7b through 6-7d). In 2730, boron concentrations are predicted to be
greater than the 02L standard south of the former 1971 ash basin and north of the
FADA within the cooling pond. The simulation was conducted until 2730, at
which time there is still a zone of boron with a maximum concentration of
approximately 1,000 µg/L beyond the compliance boundary, slightly south of the
former 1971 ash basin and south of the effluent discharge canal. As discussed
previously, this long term persistence of boron occurs in a stagnation zone in the
steady state flow model. Flow transients that are likely to occur over this long
time period would be expected to dilute the boron in this location.
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Selenium concentrations greater than the 02L standard beyond the compliance
boundary occur west of the former 1984 ash basin, under the current or future
cooling pond (Figure 6-8a). The selenium concentrations west of the former 1984
ash basin extends approximately 300 feet west of the compliance boundary. The
maximum concentrations of selenium occur below and downgradient of the
northern section of the former 1984 ash basin source area. Selenium is predicted
to be within the compliance boundary, under the current or future cooling pond
for approximately 20 years (year 2040) Figure 6-8b.
Results of the transport simulation show that the distribution of COIs at
concentrations greater than 02L standards for the case with MNA alone (Figures
6-4a through 6-4d and Figures 6-5a and 6-5b) are only slightly different from the
case that considers five year corrective action with the nine extraction wells
followed by MNA (Figures 6-7a through 6-7d and Figures 6-8a and 6-8b).
6.1.3 Pump and Treat
A pump and treat system was simulated to analyze a potential corrective action
system that attempted to achieve 02L and BTV standards within thirty years.
This simulation considers 51 extraction wells and 33 clean -water infiltration wells
operating for thirty years and target the former 1984 ash basin, 1971 ash basin,
FADA, and FPA. In this simulation, each infiltration and extraction well has a
flow rate of approximately 50 gpm (Figure 6-9). Figure 6-10 shows the hydraulic
heads with pump and treat system. The simulated head distribution
demonstrates a hydraulic control within the former 1984 ash basin where clean -
water infiltration wells are adding water and extraction wells are capturing the
clean -water infiltration. The 51 extraction wells remove approximately 3.6
million gpd and the 33 infiltration wells add approximately 2.4 million gpd.
The pump and treat simulation predicts that after 30 years of remediation
simulated boron concentrations remain within the lower surficial greater than
the 02L standard beyond the compliance boundary in three areas: a small area
east-northeast of the former 1984 ash basin; a small area west of the 1984; and to
the south of the former 1971 ash basin and within the former FADA footprint,
within the future cooling pond area (Figure 6-11).
Thirty years after the operation of the pump and treat system (2050), simulated
boron concentrations greater than the 02L standard are beyond the compliance
boundary east-northeast of the former 1984 ash basin, to the west of the former
1984 ash basin, and within the future cooling pond area south of the former 1971
ash basin, and within the former FADA footprint (Figure 6-11).
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The pump and treat simulations predict selenium below the 2L standards
northwest corner of the former 1984 ash basin after approximately 30 years of
operation (Figure 6-12).
6.2 Model to Evaluate the Potential Benefit of Soil Excavation in the
1984 Ash Basin Area
The purpose of this evaluation is to provide a groundwater modeling analysis of the
residual unsaturated soil COI concentration in the 1984 basin on groundwater quality in
accordance with the basin closure excavation soil sampling plan (Duke Energy, 2018).
The current land surface elevation in the excavation footprint is now a three to four feet
above the water table. Unsaturated soils were sampled in 2019, and the sampling
program involved taking samples from depths of 0-0.5 feet and 2-2.5 feet, on a grid
pattern, at 86 locations within the former 1984 ash basin. The location of these soil
samples is shown in Figure 6-13.
The soil samples were analyzed for constituent solid mass fractions, in milligrams per
kilogram (mg/kg) on a dry weight basis, using an acid digestion method. The data
determined the total amount of each constituent in the sample; however, the results
cannot distinguish leachable (adsorbed) from non -leachable (mineralized) fractions in
the sample.
The soil samples were also subjected to synthetic precipitation leaching protocol (SPLP)
testing. The SPLP test consists of equilibrating a mass of soil sample, typically 100
grams (g) of solid, with a mass of water at a 20:1 ratio( 2 liters (L) of water). The
resulting SPLP concentration in the water is used to assess the potential leaching
behavior of the constituent from the sample.
Some of these measured SPLP concentrations of constituents are greater than the 02L
standard leading to the possibility of leaching of those constituents into groundwater in
the future. It has been suggested that additional excavation of the unsaturated soils in
the former 1984 ash basin footprint may reduce future effects to groundwater at the
Site.
Methodology
The calibrated 2019 groundwater flow model for the Site forms the basis for this
analysis. Conceptually, there are two ways in which this simulation could be
performed. With the first method, the calibrated model is run into the future using the
2019 concentrations as an initial condition. That model is then compared to a similar
model where the concentrations in the upper 3 feet of soil in the 1984 ash basin footprint
are set to zero. Based on our analysis, the two simulations produce similar results.
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The second method for performing this analysis is to run a predictive simulation in
which there is initially no COIs in groundwater outside of the volume being considered
for excavation. With this method, the mass and distribution of the constituents (boron,
arsenic, and selenium) in the excavation volume is interpolated using the SPLP
concentration data from the soil samples. As this flow and transport model runs
forward in time, it shows the effect constituents in the potential excavation volume
might have, in the future, on constituent concentrations in groundwater and whether
those constituent concentrations might be greater than 02L standards. Therefore, it
provides a clearer picture of the effect of leaving the unsaturated soil in place within the
1984 basin footprint. This second method of model analysis is used in this report.
SPLP concentrations of boron, arsenic, and selenium from the shallow (0-0.5 ft) and
deeper (2-2.5 ft) intervals were averaged at each boring location, and are shown in
Figures 6-14 through 6-16. To initialize the groundwater transport model, SPLP
concentrations were converted to an equivalent pore water concentration. One method
of performing this conversion is to use the measured solid mass fraction of the
constituent along with the SPLP concentration to calculate an apparent soil water
distribution coefficient, Kd. This calculation is appropriate for synthetic organic
compounds which are weakly adsorbed. However, with inorganic compounds such as
boron, arsenic, and selenium, only some of the constituent measured in the solid mass
fraction is leachable. The constituent might be incorporated in the mineral structure of
the soil, or it might be present as an insoluble precipitate.
A preliminary analysis of the SPLP data was performed using solid mass fractions to
compute the apparent Kd value. The resulting Ka values were unrealistically large,
featuring boron values of tens of milliliters per gram (mL/g) and arsenic values of many
hundreds of mL/g. These are in contrast with the model calibrated Kd values that came
closest to reproduce the observed concentration data (arsenic Kd=9 mL/g from previous
models of the Site; boron Kd=0.01 mL/g from the current model; selenium Kd=0.5 mL/g
from the current model). The low model values for Kd are required to reproduce the
observed field mobility of these constituents.
An alternative method for converting SPLP concentrations to pore water concentrations
involves assuming a value for Kd. Using that assumed value, it is possible to derive a
conversion equation based on a mass balance. For the SPLP test, the total mass
concentration, CT, is the total mass of constituent per volume of the soil sample. The
volume of the soil sample is the mass of the soil sample, Ms, divided by the dry bulk
density, Qb. In the SPLP test, the total mass of constituent includes the dissolved and
adsorbed parts:
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mass = CsPLPVL + CsPLPKDM,
Then the total concentration in the SPLP test is:
__ CsPLPVL + CsPLPKDMs
CT %Pb
Where VL is the volume of water in the SPLP test (2 L), and the solid mass, Ms is 0.1 kg.
Under ambient conditions, the total concentration is:
CT =OCw+PbKdC,,
Where y is the porosity and Cw is the pore water concentration. Equating these
expressions and solving for CW:
CsPLP VLM + CsPLPKd
C _ s
C. Kd+ �
Pb
For a porosity of 0.3 and a bulk density of 1.6 mL/g:
C = CsPLP (20 + Kd )
w Kd + 0.1875
The limiting cases occur when Ka= zero and infinity. For Kd=O, CW=106.7 CsPLP. For very
large Ka, CW=CSPLP. Table 6-1 shows the conversion factor to convert from CsPLP to CW as a
function of Ka.
In this analysis the United State Environmental Protection Agency (USEPA) regional
screening levels (https://www.epa.gov/risk/regional-screening-levels-rsls-users-guide;
https:Hsemspub.epa.gov/work/HQ/199658.pdf) were used for the Kd values for boron
(Ka=3.0 mL/g), arsenic (Ka=29.0 mL/g) and selenium (Ka=5.0 mL/g). Those regional
screening levels offer SPLP conversion factors of 7.22 for boron, 1.68 for arsenic, and
4.82 for selenium. Those conversion factors produce values for concentrations of boron,
arsenic, and selenium in groundwater that are similar to observed groundwater
concentrations near the ash basins.
Converted SPLP concentrations at each soil sampling point are shown for boron
(Figure 6-17), arsenic (Figure 6-18), and selenium (Figure 6-19). Those concentrations
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were interpolated using linear interpolation to compute concentration values at each
numerical gridblock in the model layer that corresponds to the top 3 feet of soil that is
present in the 1984 ash basin footprint. The assumed Ka values (3 mL/g for boron, 29
mL/g for arsenic, and 5 mL/g selenium) were also assigned to this model layer. The use
of these larger Ka values in this layer has the effect of increasing the amount of time
before a constituent source mass leaches out of the layer.
Lower calibrated Kd values were used in the other model layers. The Kd value for
arsenic was set to 9 mL/g based on previous calibrated models (SynTerra, 2016b;
Geosyntec, 2017b). These lower values increase the mobility of the constituents in
groundwater compared to the higher values that were used in the potential excavation
volume.
The interpolated source (excavation volume) concentrations were truncated at the edges
of the 1984 basin, and a concentration of zero was assigned everywhere else in the
model as an initial condition. The only boron, arsenic, and selenium present in this
model at the start of the simulation is the mass in the unsaturated soil remaining in the
1984 ash basin. This predictive simulation runs for 30 years into the future. The
groundwater flow field does not include the interim action groundwater extraction
wells.
The mechanisms for attenuation of the constituents within and near the 1984 ash basin
are dilution and dispersion. Dilution occurs as clean rainwater infiltrates the soil. The
calibrated background recharge rate in the Sutton model is 16 inches per year; this value
was assigned to the 1984 ash basin footprint. This rate of recharge results in the flushing
and dilution of mobile compounds such as boron.
The mechanism of dispersion causes spreading due to scale -dependent velocity
variations. This is modeled as a concentration -dependent diffusive process with
dispersion coefficients that are equal to a dispersivity multiplied by the groundwater
pore velocity. The calibrated transport model used typical field -scale values of
dispersivity (longitudinal dispersivity = 50 ft.; transverse dispersivity = 5 ft.; vertical
dispersivity = 0.05 ft.).
The dispersivity values were reduced to near -zero values in the present simulation
(longitudinal dispersivity = 0.1 ft.; transverse dispersivity = 0.01 ft.; vertical dispersivity
= 0.0001 ft.). This is a conservative approach that minimizes the effect of dispersion as
an attenuation mechanism in the predictive simulation.
Page 6-9

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
Results
Figures 6-20a through 6-20d show the simulated maximum boron concentration at any
depth after 5, 10, 20, and 30 years of migration. The maximum boron concentration at
each horizontal location is computed internally by the model by selecting the maximum
concentration value from each vertical column of gridblocks and assigning that value to
a 21) horizontal grid.
Maximum boron concentrations are substantially reduced after 5 years (Figure 6-20a)
and 10 years (Figure 6-20b), with only limited horizontal migration toward the cooling
pond and the excavated 1971 ash basin. Boron concentrations greater than the 02L
standard (700 µg /L) are not seen at the compliance boundary. In both the 20-year
(Figure 6-20c) and 30-year (Figure 6-20d) models, boron concentrations greater than 700
µg/L are not found anywhere.
Arsenic concentrations are much more persistent than boron due to the higher Ka value.
However, the predicted migration of arsenic in groundwater is limited. Figures 6-21a
through 6-21d show the simulated maximum arsenic concentration at any depth over
time. The maximum concentrations gradually decline over time due to dilution by
recharge, but remain significant after 30 years (Figure 6-21d). However, concentrations
of arsenic were not predicted to be greater than the BTV (14 µg/L) at the compliance
boundary at any time in the simulation. Over the 30 year simulation period, the arsenic
footprint slowly shrinks, and arsenic is not expected to reach the compliance boundary
above the BTV level at any time in the future.
Selenium pore water concentrations in the unsaturated soils in the 1984 ash basin area
are generally low except for a few isolated locations with elevated levels (Figure 6-19).
As a result, the predictive model shows selenium in the unsaturated soil having little
effect on groundwater over the 30-year simulation period (Figures 6-22a through 6-
22d). In the simulation, concentrations of selenium are not greater than the 02L
standard (20 µg/L) at the compliance boundary.
Conclusions
This analysis shows that the future effects of unsaturated soils left in the 1984 ash basin
area on groundwater will be limited. By itself, the mass of constituents released from
this soil would not result in concentrations greater than 02L standards at the compliance
boundary. Therefore, excavation or other corrective measure for this material would be
expected to have little practical benefit in reducing future constituent concentrations in
the groundwater at or beyond the compliance boundary.
Page 6-10

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
6.3 Conclusions Drawn From the Predictive Simulations
The following conclusions are based on the results of the groundwater flow and
transport simulations:
• The time needed for boron and selenium to reach 02L compliance with and
without active remediation is approximately the same for the MNA and the nine
well extraction corrective action followed by MNA.
• Pump and treat corrective action simulation would take 51 extraction wells to
pump a total of 3.6 million gpd and 33 clean -water infiltration wells to pump 2.4
million gpd, with boron, and selenium not able to reach compliance after 30
years of operation.
• The model to evaluate the potential benefit of soil excavation analysis shows that
the future effects of unsaturated soils left in the 1984 ash basin area will be
limited. Excavation of these soils would have little practical benefit in reducing
future constituent concentrations in the groundwater at or beyond the
compliance boundary.
Page 6-11

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
7.0 REFERENCES
Bukowski McSwain, K., L.N. Gurley, and D.J. Antolino, 2014, Hydrogeology, Hydraulic
Characteristics, and Water -Quality Conditions in the Surficial, Castle Hayne, and
Pee Dee Aquifers of the Greater New Hanover County Area, North Carolina,
2012-2013, U.S. Geological Survey, Scientific Investigations Report 2014-5169, 52
P.
Duke Energy, 2018. Excavation Soil Sampling Plan, L.V. Sutton Energy Complex 1984
Ash Basin for Ash Basin Excavation, North Carolina Ash Basin Closure. Revision
2, December 2018.
Geosyntec 2017a. 1971 Basin Closure Investigation Report. L.V. Sutton Energy Complex.
October 2017.
Geosyntec, 2017b. Interim Action Plan Implementation Basis of Design Report. L.V.
Sutton Energy Complex, January 2017, Attachment C.
Geosyntec 2017c. LOLA Closure Investigation Report. L.V. Sutton Energy Complex.
December 2017.
Geosyntec 2019. 1984 Basin PLM Sampling Results. L.V. Sutton Energy Complex.
August 2019.
Geosyntec 2020. Former Process Area Sampling Results. L.V. Sutton Energy Complex.
April 2020.
Harden, S.L., J.M. Fine, and T.B. Spruill, 2003, Hydrogeology and Ground -Water
Quality of Brunswick County, North Carolina, U.S. Geological Survey, Water -
Resources Investigations Report 03-4051, 95 p.
Haven, W. T. 2003. Introduction to the North Carolina Groundwater Recharge Map.
Groundwater Circular Number 19. North Carolina Department of Environment
and Natural Resources. Division of Water Quality, 8 p.
HDR. (2016). L.V. Sutton Energy Complex Aquifer Pumping Test Report. May 18, 2016.
SynTerra. (2015a). Comprehensive Site Assessment, L. V. Sutton Energy Complex.
SynTerra. (2015b). Corrective Action Plan Part 1, L. V. Sutton Energy Complex.
SynTerra. (2016a). Corrective Action Plan Part 2, L. V. Sutton Energy Complex.
Page 7-1

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex — Duke Energy Progress, LLC
SynTerra. (2016b). Comprehensive Site Assessment Supplement 1, L. V. Sutton Energy
Complex.
SynTerra. (2018). Comprehensive Site Assessment Update, L. V. Sutton Energy Complex.
United States Environmental Protection Agency (USEPA). (2019). USEPA Regional
Screening Levels. May 2020 Update. Available at:
https://www.epa.gov/risk/regional-screening-levels-rsls
Page 7-2

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex - Duke Energy Progress, LLC
FIGURES

APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 700 YEARS AFTER EXCAVATION
MNA
MNA
♦ AI�
. �I
I
L p
■ fi*
■ i
rl
F�
' 3 `� ,��.. i � -
..
•�' _ar � gyp,. £?: ,�v4. ��* -
APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 700 YEARS AFTER EXCAVATION
CORRECTIVE ACTION FOLLOWED BY MNA
CORRECTIVE ACTION FOLLOWED BY MNA
Y
♦ ♦
♦
.5
'
a a
e 1 �•.
LEGEND
NOTES:
GRAPHIC SCALE
990 0 990 1,980
BORON 700-4,000 Ng/L
1. ALL BOUNDARIES ARE APPROXIMATE.
_ ASH BASIN COMPLIANCE
2. BORON IS NATURALLY OCCURRING IN
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE:05/31/2020
BOUNDARY
REPRESENT DNINITHEOMODEL.
DUKE
ASH BASIN WASTE BOUNDARY
3. AERIAL PHOTOGRAPHY OBTAINED
FROM TERRA SERVER 17,
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
FORMER ASH DISPOSAL AREA
2019. IMAGE COLLECTED APRIL PRIL 4,2019.
ENERGY
_
BOUNDARY
4. DRAWING HAS BEEN SET WITH
PROGRESS
PROJECT MANAGER: B. WYLIE
www.synterracorp.com
PROJECTION OF NORTH CAROLINA
PLANE COORDINATE SYSTEM
FIGURE ES -la
-- FORMER COAL PILE AREA
RIPS 3200 (NAD 198TE
3).
— FORMER PROCESS AREA
COMPARISON OF SIMULATED BORON CONCENTRATIONS
ONSITE LANDFILL BOUNDARY
FLOW AND TRANSPORT MODELING REPORT
ONSITE LANDFILL COMPLIANCE
L.V. SUTTON ENERGY COMPLEX
BOUNDARY
WILMINGTON, NORTH CAROLINA
-- SAND MINES

APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 20 YEARS AFTER EXCAVATION
MNA
MNA
.:; r
�NIN
Al
APPROXIMATELY 10 YEARS AFTER EXCAVATION
APPROXIMATELY 20 YEARS AFTER EXCAVATION
CORRECTIVE ACTION FOLLOWED BY MNA
CORRECTIVE ACTION FOLLOWED BY MNA
• '"
•
.A -a
♦
•
• �.
`
r--
•� t
LEGEND
NOTES:
—J
GRAPHIC SCALE
990 0 990 1,980
SELENIUM 20 - 139 Ng/L
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
ASH BASIN COMPLIANCE
- •
2. AERIAL PHOTOGRAPHY OBTAINED
FROM TERRA SERVER ON JUNE 17,
2019. IMAGE COLLECTED APRIL 4, 2019.
s Terra
, •
DRAWN BY: R. KIEKHAEFER DATE: 05/31/2020
DUKE
BOUNDARY
3. DRAWING HAS BEEN SET WITH A
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
PROJECTION OF NORT H CAROLINA
STATE PLANE COORDINATE SYSTEM
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
FORMER ASH DISPOSAL AREA
PIPS 3200 (NAD 1983).
PROJECT MANAGER: B. WYLIE
_
BOUNDARY
PROGRESS
www.synterracorp.com
FIGURE ES -lb
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
COMPARISON OF SIMULATED
• ONSITE LANDFILL BOUNDARY
SELENIUM CONCENTRATIONS
FLOW AND TRANSPORT MODELING REPORT
_ ONSITE LANDFILL COMPLIANCE
L.V. SUTTON ENERGY COMPLEX
BOUNDARY
WILMINGTON, NORTH CAROLINA
-- SAND MINES

APPROXIMATELY 30 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
MNA
NINE EXTRACTION WELLS FOLLOWED BY MNA
•
•
19
► !
tea, i �.
�---•
APPROXIMATELY 30 YEARS AFTER EXCAVATION
LEGEND
PUMP AND TREAT
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
BORON 700 - 4,000 pg/L
`
ASH BASIN COMPLIANCE BOUNDARY
♦
ASH BASIN WASTE BOUNDARY
— FORMER ASH DISPOSAL AREA BOUNDARY
-- FORMER COAL PILE AREA
FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
�•.�
SAND MINES
Ism
NOTES:
GRAPHIC SCALE
990 0 990 1,980
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE MODEL.
synTerra
DRAWN BY: R. KIEKHAEFER DATE: 05/31/2020
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
DUKE
COLLECTED APRIL 4, 2019.
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
ENERGY
APPROVED BY. B. WYLIE DATE: 07/29/2020
PROGRESS
PROJECT MANAGER: B. WYLIE
www.synterracorp.com
FIGURE ES-2a
COMPARISON OF CORRECTIVE ACTION SIMULATED BORON CONCENTRATIONS APPROXIMATELY 30 YEARS AFTER
SOURCE EXCAVATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

APPROXIMATELY 30 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
MNA
NINE EXTRACTION WELLS FOLLOWED BY MNA
.000
r i
r i
APPROXIMATELY 30 YEARS AFTER EXCAVATION
LEGEND
PUMP AND TREAT
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
SELENIUM 20 - 139 pg/L
A
ASH BASIN COMPLIANCE BOUNDARY
A
A ♦
ASH BASIN WASTE BOUNDARY
—FORMER ASH DISPOSALAREA BOUNDARY
A •
-- FORMER COAL PILE AREA
�
- FORMER PROCESS AREA
,. A
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
i
r
NOTES:=J
GRAPHIC SCALE
990 0 990 1,980
1. ALL BOUNDARIES ARE APPROXIMATE.
2. SIMULATED SELENIUM CONCENTRATIONS DO NOT EXCEED 20 Ng/LAFTER 20 YEARS IN ANY OF
THE THREE SIMULATIONS.
synTerra
J,
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/31/2020
(� DUKE
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
4. DRAWING HAS BEEN SET WITH PROJECTION OF NORTH CAROLINA STATE PLANE
ENERGY
APPROVEDDATE: 07/29/2020
COORDINATE SYSTEM FIPS 3200 (NAD 1983).PROJECT
MANAGER: B. WYLIE
PROGRESS
www.synterracorp.com
FIGURE ES-2b
COMPARISON OF CORRECTIVE ACTION SIMULATED SELENIUM CONCENTRATIONS APPROXIMATELY 30 YEARS AFTER
SOURCE EXCAVATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

APPROXIMATELY 5 YEARS AFTER EXCAVATION
APPROXIMATELY 10 YEARS AFTER EXCAVATION
•• • •
•• •
•
e. _.. ... . _.. .. ,...__ •
APPROXIMATELY 20 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
Ilk
LEGEND
NOTES:
J
GRAPHIC SCALE
990 0 990 1,980
• SAMPLE LOCATION
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
BORON 700 - 4,000 Ng/L
2. SIMULATED BORON 20 AND 30 YEARS
S) T�1 ra
DRAWN BY: R. KIEKHAEFER DATE: 06/03/2020
AFTER EXCAVATION WAS NOT PRESENT
ABOVE 700 Ng/L
(� DUKE
_ ASH BASIN COMPLIANCE
BOUNDARY
3. AERIAL PHOTOGRAPHY OBTAINED
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
FROM TERRA SERVER ON JUNE 17,
2019. IMAGE COLLECTED APRIL 4, 2019.
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
ASH DISPOSAL AREA
4. DRAWING HAS BEEN SET WITH
PROGRESS
www.synterracorp.com
_FORMER
PROJECTION OF NORTH CAROLINA
BOUNDARY
STATE PLANE COORDINATE SYSTEM
FIGURE ES-3a
PIPS 3200 (NAD 1983).
-- FORMER COAL PILE AREA
COMPARISON OF SIMULATED BORON CONCENTRATIONS FROM
— FORMER PROCESS AREA
THE POTENTIAL BENEFIT OF SOIL EXCAVATION IN THE 1984 ASH
ONSITE LANDFILL BOUNDARY
BASIN MODEL
FLOW AND TRANSPORT MODELING REPORT
ONSITE LANDFILL COMPLIANCE
BOUNDARY
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
-- SAND MINES

APPROXIMATELY 5 YEARS AFTER EXCAVATION
APPROXIMATELY 10 YEARS AFTER EXCAVATION
• • • ,
• • • ,
APPROXIMATELY 20 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
••• •• �;
i•• •• AIIA
•
•
xft-
LEGEND
e
NOTES:=J
GRAPHIC SCALE
ARSENIC 14 - 100 Ng/L
975 o 978 7s50
1. ALL BOUNDARIES ARE APPROXIMATE.
ARSENIC > 100 Ng/L
Terra
(IN FEET)
2. AERIAL PHOTOGRAPHY OBTAINED
DRAWN BY: R. KIEKHAEFER DATE: 06/03/2020
• SAMPLE LOCATION
FROM TERRA SERVER ON JUNE 17,
2019. IMAGE COLLECTED APRIL 4, 2019.
DUKE
- ASH BASIN COMPLIANCE
BOUNDARY
3. DRAWING HAS BEEN SET WITH A
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
PROJECTION OF NORTHCAROLINA
STATE PLANE COORDINATE SYSTEM
COORDINATESYSTEEM
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
PIPS 3200(NAD 1983).
PROJECT MANAGER: B. WYLIE
_FORMERASH DISPOSALAREA
PROGRESS
www.synterracorp.com
BOUNDARY
FIGURE ES-3b
-- FORMER COAL PILE AREA
COMPARISON OF SIMULATED ARSENIC CONCENTRATIONS FROM
—FORMER PROCESS AREA
THE POTENTIAL BENEFIT OF SOIL EXCAVATION IN THE 1984 ASH
ONSITE LANDFILL BOUNDARY
BASIN MODEL
ONSITE LANDFILL COMPLIANCE
FLOW AND TRANSPORT MODELING REPORT
BOUNDARY
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
--SAND MINES

APPROXIMATELY 5 YEARS AFTER EXCAVATION
APPROXIMATELY 10 YEARS AFTER EXCAVATION
•=...�
, r
xx�;^
••• •• � ♦yam �
••• •• 4
•• • ♦
•• •
APPROXIMATELY 20 YEARS AFTER EXCAVATION
APPROXIMATELY 30 YEARS AFTER EXCAVATION
NOTES:
�.:J
GRAPHIC SCALE
LEGEND
990 0 990 1,980
• SAMPLE LOCATION
1. ALL BOUNDARIES ARE APPROXIMATE.
(IN FEET)
SELENIUM 20-139Ng/L
2. AERIAL PHOTOGRAPHY OBTAINED
FROM TERRASERVER ON JUNE 17,
s ynTerra
,•
2019. IMAGE COLLECTED APRIL 4, 2019.
DRAWN BY: R. KIEKHAEFER DATE:06/03/2020
(� DUKE
_ ASH BASIN COMPLIANCE
BOUNDARY
3. DRAWING HAS BEEN SET WITH
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
PROJECTION OF NORTH CAROLTE SYSTEM
SYSTEM
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
ASH BASIN WASTE BOUNDARY
FPST3 00(NAD 11983)INATE
PROJECT MANAGER: B. WYLIE
_FORMER ASH DISPOSAL AREA
PROGRESS
www.synterracorp.com
BOUNDARY
FIGURE ES-3c
-- FORMER COAL PILE AREA
COMPARISON OF SIMULATED SELENIUM CONCENTRATIONS FROM
— FORMER PROCESS AREA
THE POTENTIAL BENEFIT OF SOIL EXCAVATION IN THE 1984 ASH
ONSITE LANDFILL BOUNDARY
BASIN MODEL
ONSITE LANDFILL COMPLIANCE
FLOW AND TRANSPORT MODELING REPORT
BOUNDARY
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
-- SAND MINES

SUTTON PLANT /••
PARCEL LINE ♦ /
••/ ♦ O
I ' O
•
♦ LANDFILL COMPLIANCE
II BOUNDARY
I '
` SAND MINES
ICOMPLIANCE BOUNDARY,,
FORMER ASH BASIN •� `� `` ``n
WASTE BOUNDARY+ •� ,; ♦` `'
o�
• .. ' `�
FORMER 1984 ♦ ,
ASH BASIN ♦
LANDFILL WASTE
/ , ♦ BOUNDARY
�. EXCAVATED1971 a
♦♦ • ` ASH BASIN i FORMER PROCESS AREA
aA
♦ • FORMER ASH DISPOSAL
• • • • • �' AREA WASTE BOUNDARY
I — --� FORMER COAL PILE AREA
WASTE BOUNDARY
EFFLUENT DISCHARGE CANAL
• /•
[ •• POWER PLANT
` `� i� �.
INTAKE CANAL SOUTH SAND MINE`
s `
SOURCE: • ' `
2019 USGS TOPOGRAPHIC MAP, CASTLE HAYNE AND
LELAND QUADRANGLES, OBTAINED FROM THE USGS STORE AT ` ♦ ` `
https://store.usgs.gov/map-locator. ♦ `
DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH ` ``
CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200 (NAD83/2011).
(' DUKE WINSTONFNEW
FIGURE 1-1
SITE LOCATION MAP
4 ENERGY FLOW AND TRANSPORT MODELING REPORT
PROGRESS CHARLOTTE L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
DRAWN BY: J.NIRTzDATE: a/la/2ols cRAPHIc scALE
REVISED BY: C. CURRIER DATE: 07/30/2020 000 01,000 000
synTerra AP CKED ROVED B R. B.
WYLIANO DATE: 07/30/2020
APPROVED BY: B. WYLIE DATE: 07/30/2020 (IN FEET)
www.svnterracorD.com PROJECT MANAGER: B. WYLIE

11
LEGEND
ABANDONED MONITORING WELL
WELL IN ASH PORE WATER FLOW
WELL IN UPPER SURFICIAL FLOW ZONE
WELL IN LOWER SURFICIAL FLOW ZONE
WELL IN UPPER PEE DEE FLOW ZONE
WELL IN LOWER PEE DEE FLOW ZONE
WATER SUPPLY WELL
• ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
—FORMERASH DISPOSALAREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
—SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
SCR-,2<B,C 6
SMW-28
MW-22C '
AW-58 SMW-2C _
AW-5C '
BIC/D AW-5D
M W-19 SMW-38
I\ AW 5E •
SMW-3C
` MW-21C
MW 32C
CCR-102B/C MW 288 T •
MW-16 MW ]A _ MW 28C MW-16D MW-]B MW28T Y
5/D ryr . MW-TC '
AW-98
AW-9C ....I
AW-9D I
nnw 3]3]0q_l
'a
MW 3]E
" -
GRAPHIC SCALE
1,100 0 1,100 2,200
��.�
s//
Term
(IN FEET)
.
DRAWN BY: J. KIRTZ DATE: 05/21/2019
DUKE
It
REVISED BY: R. KIEKHAEFER DATE: 06/18/2020
CHECKED
ENERGY
OVEDBY: YLIE DATE: 06/18/2020
PROJECT B. E
EMANAGER:
PROGRESS
FIGURE 2-1
MONITORING WELL LOCATIONS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

lu
I
s ;
LEGEND
MODELBOUNDARY
- - ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
DUKE ENERGY PROGRESS PROPERTY LINE
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY PROGRESS.
3. THE MODEL BOUNDARY WAS SETATA DISTANCE FROM THE ASH BASIN SUCH THAT THE
BOUNDARY CONDITIONS DID NOTARTIFICIALLY AFFECT THE RESULTS NEAR THE ASH BASIN.
4. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
4DUKE
' EEN RGY
PROGRESS
1984 ASH
BASIN
(LINED)
1983
WI(TENSION
SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/20/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 4-1
NUMERICAL MODEL DOMAIN
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

�'�
01
LEGEND
ASH
SURFICIAL AQUIFER
_ PEE DEE CONFINING UNIT
LOWER SURFICIAL OR UPPER PEEDEE
SILTY PEEDEE Feet (U.S. Survey) N
PEq LOWER PEEDEE d m25Y0
DUKE
ENERGY
PROGRES:
167
synTena
DRAWN BY: R. KIEKHAEFER
REVISED BY: R. KIEKHAEFER
CHECKED BY: R. GRAZIANO
APPROVED BY: B. WYLIE
PROJECT MANAGER: B. WYLIE
DATE: 04/14/2020 FIGURE 4-2
DATE: 05/09/2020 FENCE DIAGRAM OF THE 3D HYDROSTRATIGRAPHIC MODEL
DATE: 05/09/2020 USED TO CONSTRUCT THE MODEL GRID
DATE: 05/09/2020 5X VERTICAL EXAGGERATION
GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
www.synterracorp.com
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

DUKE DRAWN BY: R. KIEKHAEFER DATE: 04/14/2020 FIGURE 4-3a
ENERGY REVISED BY: R. KIEKHAEFER DATE: 05/09/2020 COMPUTATIONAL GRID USED IN THE MODEL WITH
PROGRES. CHECKED BY: R. GRAZIANO DATE: 05/09/2020 5X VERTICAL EXAGGERATION
APPROVED BY: B. WYLIE DATE: 05/09/2020
�� PROJECT MANAGER: B. WYLIE GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WnTerra www.synterracorp.com I WILMINGTON, NORTH CAROLINA

1.0
0.8
0.6
S-
CL
0.4
E
U 0.2
f� DUKE
ENERGY
VRCGRt55
116'
synTerra
o All Piedmont Sites
♦ Sutton
♦ Model Number
. a-
89000
0.01 0.1 1 10 100
K (ft/d )
DRAWN BY: R. KIEKHAEFER DATE: 04/22/2020 FIGURE 4-4
REVISED BY: W. PRATER DATE: 05/26/2020 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN ASH
CHECKED BY: R. GRAZIANO DATE: 05/26/2020 AT 14 SITES IN NORTH CAROLINA
APPROVED BY: B. WYLIE DATE: 05/26/2020 PROJECT MANAGER: B. WYLIE DATE: 05/26/2020 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
www.synterracorp.com

1.0
>, 0.8
5 0.6
i
N
0.4
U 0.2
0.1
f� DUKE
ENERGY
VRCGRt55
116'
synTerra
° Slug Tests
♦ Model Number
o
0
o °
�
1 10
K (ft/d )
100
DRAWN BY: R. KIEKHAEFER DATE: 04/22/2020 FIGURE 4-5
REVISED BY: W.PRATER DATE: 05/26/2020 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN THE
CHECKED BY: R. GRAZIANO DATE: 05/26/2020 UPPER SURFICIAL ZONE AT SUTTON
APPROVED BY: B. WYLIE DATE: 05/26/2020 PROJECT MANAGER: B. WYLIE DATE: 05/26/2020 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
www.synterracorp.com

1.0
aJ
0.4
E
D
U 0.2
11
DUKE
t ENERGY
116'
synTerra
° Slug Tests
AHDR Pump Test
♦ Model Number
CP
g8
o °
o
10
K (ft/d )
100
DRAWN BY: R. KIEKHAEFER DATE: 04/22/2020 FIGURE 4-6
REVISED BY: W.PRATER DATE: 05/26/2020 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN THE
CHECKED BY: R. GRAZIANO DATE: 05/26/2020 LOWER SURFICIAL ZONE AT SUTTON
APPROVED BY: B. WYLIE DATE: 05/26/2020 PROJECT MANAGER: B. WYLIE DATE: 05/26/2020 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
www.synterracorp.com

1.0
0. s
r)
CIO
c) 0.6
L
0.4
U 0.2
11
0
o Slug Tests o
0
♦ Model Number
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.001 0.01 0.1 1
K (ft/d )
DUKE
DRAWN BY: R. KIEKHAEFER DATE: 04/22/2020
FIGURE 4-7
t, ENERGY-
REVISED BY: W.PRATER DATE:05/26/2020
HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN THE
CHECKED BY: R. GRAZIANO DATE:05/26/2020
UPPER PEEDEE AQUIFER AT SUTTON
APPROVED BY: B. WYLIE DATE:05/26/2020
PROJECT MANAGER: B. WYLIE DATE: 05/26/2020
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
1
L.V. BUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
synTerra
www.synterracorp.com
F

WE
0.8
ro
0 0.6
t2
N
E
Z3
U
0.2
Fi
0.0001
f� DUKE
ENERGY
VRCGRt55
116'
synTerra
o Slug Tests
♦ Model Number
Eel
Eel
0.001
K (ft/d )
0.01
DRAWN BY: R. KIEKHAEFER DATE: 04/22/2020 FIGURE 4-8
REVISED BY: W.PRATER DATE:05/26/2020 HYDRAULIC CONDUCTIVITY ESTIMATED FROM SLUG TESTS PERFORMED IN THE
CHECKED BY: R. GRAZIANO DATE:05/26/2020 LOWER PEEDEE AQUIFER AT SUTTON
APPROVED BY: B. WYLIE DATE:05/26/2020 PROJECT MANAGER: B. WYLIE DATE: 05/26/2020 UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
www.synterracorp.com

Wool
Tt ph
LEGEND
RECHARGE:
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
GRAPHIC SCALE
��.�2,200 0 2,200 4,400
s//� Terra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/20/2020
t DUKE REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE
ENERGY PROJECT MANAGER: B. WYLIE DATE: 06/17/2020
PROGRESS
www.synterracorp.com
FIGURE 4-9
DISTRIBUTION OF MODEL RECHARGE ZONES (2019)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
PLANT INTAKE AND DISCHARGE CANALS
SURFACE WATER FEATURES
SWAMP
-MODEL BOUNDARY
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. SWAMPS ARE INCLUDED IN THE MODEL AS DRAINS. LAKES, PONDS, CHANNELS, AND
PONDED WATER IN THE ASH BASIN ARE INCLUDED IN THE MODEL AS GENERAL HEAD ZONES.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD 1983).
1 " = 3000'
Imo:. A
��
GRAPHIC SCALE
3,900 0 3,900 7,800
�m Terra
s
(IN FEET)
■
DRAWN BY: R. KIEKHAEFER
DATE: 04/20/2020
DUKE
4nENERGY
REVISED BY: R. KIEKHAEFER
CHECKED BY: R.
OLIE
DATE: 06/24/2020
DATE: 06/24/2020
APPROED BY: B. YLIE
DATE: 06/24/2020
PROJECT
PROGRESS
FIGURE 4-10
MODEL SURFACE WATER FEATURES (2019)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
0 WATER SUPPLY WELL
MODEL BOUNDARY
■ ■ ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA BOUNDARY
FORMER COAL PILE AREA
FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
- • ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
DUKE ENERGY PROGRESS PROPERTY LINE
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY PROGRESS.
3. THE MODEL BOUNDARY WAS SETATA DISTANCE FROM THE ASH BASIN SUCH THAT THE
BOUNDARY CONDITIONS DID NOT ARTIFICIALLY AFFECT THE RESULTS NEAR THE ASH BASIN.
4. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
�♦ 1
' I
. 'le
,V(# � 13500bi
`__�
141P
nTerra
ItDUKE
ENERGY
PROGRESS
_ . . ,
• 5
� r
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/20/2020
REVISED BY: C. CURRIER DATE: 07/30/2020
CHECKED BY: R. GRAZIANO DATE: 07/30/2020
APPROVED BY: B. WYLIE DATE: 07/30/2020
PROJECT MANAGER: B. WYLIE
FIGURE 4-11
LOCATION OF WATER SUPPLY WELLS IN MODEL AREA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-1.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
l0'
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
2,100 0 2,100 4,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-1
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN ASH LAYERS 1 THROUGH 2
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

,40
#3 ,1.5 ft/d
#1 ,1.5 ft/d
LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-1.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
�i
GRAPHIC SCALE
2,300 0 2,300 4,600
��.�
s//Terra
(IN FEET)
�
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
DUKE
t�ENERGY
REVISED BY: R. KIEKHAEFER DATE:06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
PROGRESS
www.svnterracorD.com
FIGURE 5-2a
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN UPPER SURFICIAL LAYERS 3 THROUGH 6
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

#3 ,1.5 ft/d'
LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-1.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
#4 ,60 ft/d
141
synTerra
%� DUKE
ENERGY
PROGRESS
tiz
- .., �•�.
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-2b
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN UPPER SURFICIAL LAYERS 7 THROUGH 8
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
- .., �•�.
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-2b
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN UPPER SURFICIAL LAYERS 7 THROUGH 8
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

#4, 125 ft/d
� #5, 800 ft/d
1.5 ft/d
t,, #3, 30 ft/d
LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-1.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
141
synTerra
%� DUKE
ENERGY
PROGRESS
�.
1 f .
�'i1rL�l
Mir
A
#1, 0.01 ft/d
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B WYLIE
FIGURE 5-3a
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN LOWER SURFICIAL LAYER 11
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

#4, 000 ft/d
#1, 1.5 ft/d
#2, 30 ft/d
LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-1.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
#3, 125 ft/d
synTerra
t
DUKE
IENERGY
PROGRESS
4
GRAPHIC SCALE
2,300 0
2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER
DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER
DATE: 06/17/2020
CHECKED BY: R. GRAZIANO
DATE: 06/17/2020
APPROVED BY: B. WYLIE
DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-3b
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN LOWER SURFICIAL LAYER 12
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

y .
LEGEND
HYDRAULIC CONDUCTIVITY
IL
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-1.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
A e94
'w r_ -
synTerra
It
ENERGY
PROGRESS
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-4
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN UPPER PEEDEE LAYERS 13 THROUGH 15
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-1.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
, 0.01 ft/d
synTerra
It
ENERGY
PROGRESS
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-5a
PRE -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN LOWER PEEDEE LAYERS 16 THROUGH 17
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

j,.
A
LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-2.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
l0'
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-6
POST -EXCAVATION MODEL HYDRAULIC
CONDUCTIVITY ZONES IN ASH LAYERS 1 THROUGH 2
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

#3 ,10000 ft/d
#2 ,40 ft/d
LEGEND
HYDRAULIC CONDUCTIVITY
#3 ,10000 ft/d
r
#3 ,10000 ft/d
#3 ,10000 ft/d
#1 ,1.5 ft/d
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-2.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
#3 ,10000 ft/d
synTerra
%DUKE
ENERGY
PROGRESS
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-7a
POST -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN UPPER SURFICIAL LAYERS 3 THROUGH 6
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

10000 ft/d
LEGEND
HYDRAULIC
,10000
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-2.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOGGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
10000 ft/d
10000
ft/d
synTerra
It
ENERGY
PROGRESS
r-
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-7b
POST -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN UPPER SURFICIAL LAYERS 7 THROUGH 8
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

125
#5, 800 ft/d
#4, 10000 ft/d
#2, 30 ft/d
LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-2.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
0.01 ft/d
F
0
GRAPHIC SCALE
2,300 0 2,300 4,600
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
DUKE
t�ENERGY
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY! R. DATE: 06/17/2020
DATE:06/17/2020
APOREOVEDBYAGEWY?W
LE
PROGRESS
www.svnterracoro.com
FIGURE 5-8a
POST -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN LOWER SURFICIAL LAYER 11
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

125
� #4, 800 ft/d
#3, 10000 ft/d
LEGEND
HYDRAULIC CONDUCTIVITY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. ZONES SHOWN WERE USED TO DEFINE HORIZONTAL HYDRAULIC CONDUCTIVITYAND
HORIZONTAL TO VERTICAL ANISOTROPY IN THE MODEL. HYDRAULIC CONDUCTIVITY VALUES
AND RATIOS OF HORIZONTAL TO VERTICAL ANISOTROPY FOR NUMBERED POLYGONS ARE
LISTED IN TABLE 5-2.
3. AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JUNE 17, 2020. IMAGE
COLLECTED FEBRUARY 5, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
1#1, 30 ft/d
161
synTerra
%� DUKE
ENERGY
PROGRESS
GRAPHIC SCALE
2,300 0 2,300 4,600
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-8b
POST -EXCAVATION MODEL HYDRAULIC CONDUCTIVITY
ZONES IN LOWER SURFICIAL LAYER 12
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

14
13
12
11
10
+J
v
v
� 9
v
v 8
a
E
0
u 7
6
5
4
3
3 4 5 7 8 9 10 11 12
Observed Head (feet)
Reference line shown is 1:1.
DUKE DRAWN BY: R. KIEKHAEFER DATE: 05/03/2020 FIGURE 5-9
ENERGY REVISED BY: R. KIEKHAEFER DATE: 05/16/2020 SIMULATED HEADS AS A FUNCTION OF OBSERVED HEADS FROM THE
PROGRES. CHECKED BY: R. GRAZIANO DATE: 05/16/2020 2017 PRE -EXCAVATED CALIBRATED STEADY STATE FLOW MODEL
APPROVED BY: B. WYLIE DATE: 05/16/2020
�� PROJECT MANAGER: B. WYLIE GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
sy1T2rTa www.synterracorp.com
WILMINGTON, NORTH CAROLINA

W
o
nj Q e
a O ♦ � o
0
• n
♦ r iu
a
o p • �0
6 p
\, a o
r
00 r
0 ¢ _
LEGEND
RESIDUALS
< 1 ft
1-2 ft
> 2 ft
• OBSERVATION WELLS z
HYDRAULIC HEAD (FEET)
ASH BASIN COMPLIANCE BOUNDARY 5
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA GRAPHIC SCALE
1,100 0 1,100 2,200
-- FORMER COAL PILE AREA synTerra (IN FEET)
— FORMER PROCESS AREA DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
DUKE REVISED BY: R. KIEKHAEFER DATE:06/14/2020
ONSITE LANDFILL BOUNDARY �� CHECKED BY: R. GRAZIANO DATE: 06/14/2020
ENERGY APPROVED BY: B.WYLIE DATE:06/14/2020
PROJECT MANAGER: B. WYLIE
ONSITE LANDFILL COMPLIANCE BOUNDARY PROGRESS
www.synterracorp.com
-- SAND MINES
NOTES: FIGURE 5-10
1. ALL BOUNDARIES ARE APPROXIMATE. SIMULATED PRE -EXCAVATED (2017) HYDRAULIC HEAD IN
2. CONTOUR INTERVAL ISi FOOT. HEADS ARE SHOWN PRE -EXCAVATION FOR MODEL LAYER B. THE UPPER SURFICIAL FROM THE CALIBRATED STEADY
STATE FLOW MODEL (MODEL LAYER 8)
3. RESIDUALS ARE SHOWN AT EACH OBSERVATION POINT AND ARE EQUAL TO PREDICTED
HEAD -OBSERVED HEAD. FLOW AND TRANSPORT MODELING REPORT
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE L.V. SUTTON ENERGY COMPLEX
COLLECTED APRIL 4, 2019. WILMINGTON, NORTH CAROLINA
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983 AND NAVD 1988).

a,
LEGEND
GROUNDWATER FLOW DIRECTION
HYDRAULIC HEAD (FEET)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. CONTOUR INTERVAL IS 1 FOOT. HEADS ARE SHOWN PRE -EXCAVATION FOR MODEL LAYER 8.
3. ARROWS INDICATE APPROXIMATE FLOW DIRECTION, NOT MAGNITUDE.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983 AND NAVD 1988).
synTerra
%� DUKE
ENERGY
PROGRESS
m
0
GRAPHIC SCALE
1,100 0 1,100 2,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 06/15/2020
CHECKED BY: R. GRAZIANO DATE: 06/15/2020
APPROVED BY: B. WYLIE DATE: 06/15/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-11
SIMULATED PRE -EXCAVATED FLOW SYSTEM IN THE
UPPER SURFICIAL FROM THE CALIBRATED STEADY
STATE FLOW MODEL (MODEL LAYER 8)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

14
13
12
11
10
a�
� 8
a
E
0
u 7
6
a
3
7 8 9 10
Observed Head (feet)
Reference line shown is 1:1.
DUKE DRAWN BY: R. KIEKHAEFER DATE: 05/03/2020 FIGURE 5-12
ENERGY REVISED BY: R. KIEKHAEFER DATE: 05/16/2020 SIMULATED HEADS AS A FUNCTION OF OBSERVED HEADS FROM THE
PROGRES. CHECKED BY: R. GRAZIANO DATE: 05/16/2020 2019 POST -EXCAVATED CALIBRATED STEADY STATE FLOW MODEL
APPROVED BY: B. WYLIE DATE: 05/16/2020 GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
10 PROJECT MANAGER: B. WYLIE L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA
WnTerra www.synterracorp.com

00
LEGEND
RESIDUALS
< 1 ft
1-2 ft
> 2 ft
• OBSERVATION WELLS
HYDRAULIC HEAD (FEET)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. CONTOUR INTERVAL IS 1 FOOT. HEADS ARE SHOWN POST -EXCAVATION FOR MODEL LAYER 8.
3. RESIDUALS ARE SHOWN AT EACH OBSERVATION POINT ANDARE EQUAL TO PREDICTED HEAD
- OBSERVED HEAD.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983 AND NAVD 1988).
kimimmkIml
I MAXI
CID
GRAPHIC SCALE
1,100 0 1,100 2,200
��.�
s//Terra
(IN FEET)
.
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
%� DUKE
REVISED BY: R. KIEKHAEFER DATE: 06/15/2020
CHECKED BY: R. GRAZIANO DATE: 06/15/2020
ENERGY
APPROVED BY: B. WYLIE DATE: 06/15/2020
PROJJEECT MANAGER: B. WYLIE
PROGRESS
FIGURE 5-13
SIMULATED POST -EXCAVATED (2019) HYDRAULIC HEAD
IN THE UPPER SURFICIAL FROM THE CALIBRATED
STEADY STATE FLOW MODEL (MODEL LAYER 8)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

0
0
0
r
LEGEND
• GROUNDWATER FLOW DIRECTION
HYDRAULIC HEAD (FEET)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. CONTOUR INTERVAL IS 1 FOOT. HEADS ARE SHOWN POST -EXCAVATION FOR MODEL LAYER 8
3. ARROWS INDICATE APPROXIMATE FLOW DIRECTION, NOT MAGNITUDE.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983 AND NAVD 1988).
I I
CO
GRAPHIC SCALE
1,100 0 1,100 2,200
/�1�
s Terra
(IN FEET)
�
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
%� DUKE
REVISED BY: R. KIEKHAEFER DATE: 06/14/2020
CHECKED BY: R. GRAZIANO DATE: 06/14/2020
ENERGY
APPROVED BY: B. WYLIE DATE: 06/14/2020
PROJJEECT MANAGER: B. WYLIE
PROGRESS
FIGURE 5-14
SIMULATED POST -EXCAVATED (2019) FLOW SYSTEM IN
THE UPPER SURFICIAL FROM THE CALIBRATED STEADY
STATE FLOW MODEL (MODEL LAYER 8)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
0 PRESENT IN LAYERS 3 AND 4
® PRESENT IN LAYERS 3 THROUGH 6
PRESENT IN LAYERS 7 THROUGH 12
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA BOUNDARY
-- FORMER COAL PILE AREA
FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. SOURCE ZONE DATA IS PRESENTED IN TABLES 5-7a AND b. MODELED COIs ARE BORON AND
SELENIUM.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD 1963).
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
810 0 810 1,620
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
APPROVED BY: B. WYLIE DATE: 07/26/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-15a
BORON AND SELENIUM SOURCE ZONES FOR THE
HISTORICAL TRANSPORT MODEL
PRE -EXCAVATION (2017)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

r y'
-1 EXCAVATED FROM LAYERS 11 THROUGH 12 I `*%._

Ll
m
L
LEGEND
• MONITORING WELL, OBSERVED BORON < 700 pg/L
MONITORING WELL, OBSERVED BORON > 700 pg/L
BORON 700 - 4,000 Ng/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSALAREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1963).
GRAPHIC SCALE
7.,7.00 0 7.,7.00 2,200
/rye ��
sy
(IN FEET)
■Terra
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
ItDENUKE
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. ODATE: 07/26/2020
RGY
APPROVEDB. WYLIEDATE:07/26/2020
CMAN: WYLIE
PROGRESS
www.svnterracorD.com
FIGURE 5-16a
SIMULATED 2017 PRE -EXCAVATION MAXIMUM BORON
CONCENTRATIONS IN ALL NON -ASH LAYERS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

L
ri
ii
LEGEND
• MONITORING WELL, OBSERVED SELENIUM < 20 pg/L
MONITORING WELL, OBSERVED SELENIUM > 20 pg/L
SELENIUM 20 -139 pg/L
SELENIUM >139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
--SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1963).
•
GRAPHIC SCALE
`�
1,100 0 1,100 2,200
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANODATE: 07/26/2020
DUKE
It
EEN RGY
B. WYLIEDATE: 07/26/2020
APPRECT
MAN: WYLIE
PROGRESS
FIGURE 5-16b
SIMULATED 2017 PRE -EXCAVATION MAXIMUM
SELENIUM CONCENTRATIONS IN ALL NON -ASH LAYERS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

r=
LEGEND
• MONITORING WELL, OBSERVED BORON < 700 pg/L
MONITORING WELL, OBSERVED BORON > 700 pg/L
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD 1963).
*7
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
1,100 0 1,100 2,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
APPROVED BY: B. WYLIE DATE: 07/26/2020
PROJECT MANAGER: B. WYLIE
FIGURE 5-17a
SIMULATED 2019 POST -EXCAVATION MAXIMUM
BORON CONCENTRATIONS IN ALL NON -ASH LAYERS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

•
m
L
LEGEND
• MONITORING WELL, OBSERVED SELENIUM < 20 pg/L
MONITORING WELL, OBSERVED SELENIUM > 20 pg/L
SELENIUM 20 -139 pg/L
SELENIUM >139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1963).
GRAPHIC SCALE
7
1,100 0 1,100 2,200
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 04/30/2020
ItDENUKE
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. ODATE: 07/26/2020
RGY
APPROVEDDATE:07/26/2020
B. WYL.
CMAN: WYLIE
PROGRESS
www.svnterracorD.com
FIGURE 5-17b
SIMULATED 2019 POST -EXCAVATION MAXIMUM
SELENIUM CONCENTRATIONS IN ALL NON -ASH LAYERS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

DISCHARGE CANAL
NORTH DIKE, �. SCALE IN FEET
O/y1CHI �...\
GFQ4
�t
`COOLING POND \ \ GB-073�A7g4/1p1� �\B-0 � 2" L L B\ G�027,2�8� %��4'p—�-
WWW GGGgggGlBpppppp0ppp26LG
WEST DIKE
NOTES:
1. COORDINATES ARE BASED ON NORTH CAROLINA STATE
3. TARGET BASE OF EXCAVATION SHOWN ABOVE WAS
4. TARGET BASE OF EXCAVATION GRADES SHOWN ABOVE
PLANE GRID SYSTEM, NORTH AMERICAN DATUM OF
ESTABLISHED BASED ON THE CLOSURE INVESTIGATION
ARE INTENDED TO MEET NCDEQ CLOSURE
1983 (FEET, NADB3L ELEVATIONS ARE BASED ON NORTH
AMERICAN VERTICAL DATUM OF 1988 (FEET, NAVD88).
PERFORMED WITHIN THE LOLA IN JULY AND AUGUST
2017 AND THE SUBSURFACE INVESTIGATIONS
REQUIREMENTS AND REPRESENT MINIMUM
EXCAVATION ELEVATIONS.
PERFORMED ALONG THE DIKE IN 2004, 2005, 2015, AND
2. THE PLANIMETRIC LOCATION ON THIS MAP IS BASED ON
PHOTOGRAMMETRIC MAPPING OF IMAGERY
2016. SUBSEQUENTLY, THE TARGET BASE OF
EXCAVATION SURFACE WAS ADJUSTED ADJACENT TO
5. CCR EXCAVATION ALONG THE DIKE NORTH, SOUTH,
AND EAST SLOPES WILL TIE TO THE EXISTING GRADES.
COLLECTED ON 17 APRIL 2014 AND INTERPRETED BY
WSP OF CARY, NC, DATED MARCH 2O15.
THE WESTAND NORTH DIKES TO PROMOTE EQUIPMENT
SAFETY AND FACILITATE CONSTRUCTION OPERATIONS.
LEGEND
EDGE OF WATER (NOTE 2)
�o TARGET BASE OF
EXCAVATION CONTOUR
(NOTES 3AND 4)
Arlo
FIGURE 6-1
��T�erra
FADA EXCAVATION DESIGN USED IN THE
sy/
SIMULATIONS (GEOSYNTEC, 2020)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DRAWN BY. R. KIEKHAEFER DATE: 07/28/2020
ISED BY. R. KIEKHAEFER DATE: 07/28/2020
CHECKEDBY:R.GRAZIANO DATE: 07/28/2020
APPROVED BY: B. WYLIE DATE: 07/28/2020
DUKEREV
ENERGY
PROGRESS
PROJECT MANAGER: B. WYLIE
WILMINGTON, NORTH CAROLINA
www.svnterracorD.com

Proposed FPA Sampling Locations
Boring ID
Latitude
Longitude
FPA-01
34.289903
-77.985255
FPA-02
34.289749
-77.984985
FPA-03
34.289672
-77.985403
FPA-04
34.289512
-77.985140
FPA-05
34.289425
-77.985576
FPA-06
34.289270
-77.985304
a
Legend
• Proposed Soil Sampling Locations
Former 1971 Basin Boundary
- - - Former Process Area (FPA)
0 Open Pit
Notes
1. Horizontal coordinate system US State Plane 1983 North
Carolina, US survey feet.
2. 2016 World Imagery - Source: Esri, DigitalGlobe, GeoEye, i-
cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP,
swisstopo, and the GIS User Community.
Alp
synTerra
DRAWN BY: R. KIEKHAEFER
REVISED BY.' R.
RSE
DATE: 07/28/2020
DATE: 07/28/2020
UKE
tl`�ENERGY
APPROVED BY. B. E
DATE:07/28/2020
PROGRESS
www.svnterracorD.com
,F,Pr 02
(
- T
o too
Feet
Proposed FPA Confirmation Sampling Locations
L V. sunon Plant
eosyntec
Figure
1
FIGURE 6-2
FPA EXCAVATION AREA USED IN THE SIMULATIONS
(GEOSYNTEC, 2020)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
,o
HYDRAULIC HEAD (FEET)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
- FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. CONTOUR INTERVAL IS 1 FOOT. HEADS ARE SHOWN POST -EXCAVATION FOR MODEL LAYER 8.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983 AND NAVD 1988).
111�77
synTerra
%� DUKE
ENERGY
PROGRESS
00
0
I
GRAPHIC SCALE
1,100 0 1,100 2,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/25/2020
REVISED BY: R. KIEKHAEFER DATE: 06/17/2020
CHECKED BY: R. GRAZIANO DATE: 06/17/2020
APPROVED BY: B. WYLIE DATE: 06/17/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-3
SIMULATED HYDRAULIC HEADS IN UPPER SURFICIAL
AFTER SOURCE EXCAVATION WITH MNA
(MODEL LAYER 8)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

A
f
LEGEND
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
GRAPHIC SCALE
116�
1,100 0 1,100 2,200
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/25/2020
UKE
REVISED BY.' R. KIEKHAEFER DATE: 07/29/2020
E BY. R. GRAZIANO DATE: 07/29/2020
ESN RGY
APPROVED BY. B. DATE: 07/29/2020
MANAGER:
T
PROGRESS
www. svnte rra co r D. co m
FIGURE 6-4a
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 10 YEARS AFTER THE SOURCE
EXCAVATION WITH MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

A
LEGEND
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
GRAPHIC SCALE
1,100 0 1,100 2,200
synTerra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY.' R. KIEKHAEFER DATE: 07/29/2020
UKE
tD�EN RGY APPROVED BY. R. GRAZIANO DATE: 07/29/2020
TE BY. B. MANAGER: DATE: 07/29/2020
PROGRESS
www.synterracorp.com
FIGURE 6-4b
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 200 YEARS AFTER THE SOURCE
EXCAVATION WITH MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

A
Fes'
LEGEND
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
GRAPHIC SCALE
1,100 0 1,100 2,200
sym erra FEET
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY.' R. KIEKHAEFER DATE: 07/29/2020
UKE
tD�EN RGY APPROVED BY. R. GRAZIANO DATE: 07/29/2020
TE BY. B. MANAGER: DATE: 07/29/2020
PROGRESS
www.synterracorp.com
FIGURE 6-4c
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 400 YEARS AFTER THE SOURCE
EXCAVATION WITH MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

�'s
A
LEGEND
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
>k.
GRAPHIC SCALE
1,100 0 1,100 2,200
sym erra FEET
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY.' R. KIEKHAEFER DATE: 07/29/2020
UKE
tD�EN RGY APPROVED BY. R. GRAZIANO DATE: 07/29/2020
TE BY. B. MANAGER: DATE: 07/29/2020
PROGRESS
www.synterracorp.com
FIGURE 6-4d
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 700 YEARS AFTER THE SOURCE
EXCAVATION WITH MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

L
■
9
-o"
1
LEGEND
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1983).
47
synTerra
t
DUKE
IENERGY
PROGRESS
y
GRAPHIC SCALE
1,100 O 1,100 2,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-5a
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 10 YEARS AFTER THE SOURCE
EXCAVATION WITH MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

L
■
9
-o"
1
LEGEND
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
47
synTerra
t
DUKE
IENERGY
PROGRESS
y
GRAPHIC SCALE
1,100 O 1,100 2,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-5b
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 20 YEARS AFTER THE SOURCE
EXCAVATION WITH MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

� � o
1 0
S O
co CD
�La
.1I7 O
1
w
o 0
1 1
10
0
LEGEND
EXTRACTION WELLS
HYDRAULIC HEAD (FEET) -
, 5
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY �� GRAPHIC SCALE
1,100 0 1,100 2,200
FORMER ASH DISPOSAL AREA
synTerra (IN FEET)
FORMER COAL PILE AREA DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISE— FORMER PROCESS AREA %� DUKE CHECKDBY:R.. GRAZIEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
ENERGYAPPROVED BY: B. WYLIE DATE: 07/26/2020
PROGRESS
ONSITE LANDFILL BOUNDARY PROJECT MANAGER: B. WYLIE
ONSITE LANDFILL COMPLIANCE BOUNDARY www.synterracorp.com
SAND MINES FIGURE 6-6
SIMULATED HYDRAULIC HEADS IN UPPER SURFICIAL
NOTES: AFTER THE SOURCE EXCAVATION WITH NINE
1. ALL BOUNDARIES ARE APPROXIMATE. EXTRACTION WELLS AND MNA (MODEL LAYER 8)
2. CONTOUR INTERVAL IS 1 FOOT. HEADS ARE SHOWN POST -EXCAVATION FOR MODEL LAYER 8. FLOW AND TRANSPORT MODELING REPORT
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17,2019. IMAGE L.V. SUTTON ENERGY COMPLEX
COLLECTED APRIL 4, 2019. WILMINGTON, NORTH CAROLINA
4. DRAWING HAS BEEN SET WITH PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1983 AND NAVD 1988).

L
I■
LEGEND
EXTRACTION WELLS
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. EXTRACTION WELLS WERE TURNED OFF 5 YEARS AFTER EXCAVATION.
3. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
5. AWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COODRRDINATE SYSTEM RIPS 3200 (NAD 1983).
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
1,100 0 1,100 2,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-7a
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 10 YEARS AFTER THE SOURCE
EXCAVATION WITH NINE EXTRACTION WELLS FOLLOWED
BY MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

I m
L
17
N ♦
�
♦ 1
1
40
LEGEND
EXTRACTION WELLS
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. EXTRACTION WELLS WERE TURNED OFF 5 YEARS AFTER EXCAVATION.
3. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD 1983).
GRAPHIC SCALE
1,100 0 1,100 2,200
synTerra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
DATE: 07/29/2020
ItDENUKE CHECKED BY: R. RGY PROJECTAPPROVED BY: BE YLIE OLIE DATE:07/29/2020
PROGRESS
www.synterracorp.com
FIGURE 6-7b
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 200 YEARS AFTER THE SOURCE
EXCAVATION WITH NINE EXTRACTION WELLS FOLLOWED
BY MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

L
LEGEND
EXTRACTION WELLS
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
-- SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. EXTRACTION WELLS WERE TURNED OFF 5 YEARS AFTER EXCAVATION.
3. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
5. AWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COODRRDINATE SYSTEM RIPS 3200 (NAD 1983).
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
1,100 0 1,100 2,200
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-7c
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 400 YEARS AFTER THE SOURCE
EXCAVATION WITH NINE EXTRACTION WELLS FOLLOWED
BY MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

L
I m
LEGEND
EXTRACTION WELLS
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. EXTRACTION WELLS WERE TURNED OFF 5 YEARS AFTER EXCAVATION.
3. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTEDAPRIL 4, 2019.
5. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
G
GRAPHIC SCALE
7,700 0 7,100 2,200
synTerra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
DUKE CHECKED BY: R. GRAZIANO DATE: 07/29/2020
It APPROVD BY: B. WYLIE EEN RGY PRO ECE MANAGER: B. WYLIE DATE: 07/29/2020
PROGRESS
www.synterracorp.com
FIGURE 6-7d
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 700 YEARS AFTER THE SOURCE
EXCAVATION WITH NINE EXTRACTION WELLS FOLLOWED
BY MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

It
10
LEGEND
EXTRACTION WELLS
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. EXTRACTION WELLS WERE TURNED OFF 5 YEARS AFTER EXCAVATION.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
GRAPHIC SCALE
1,100 0 1,100 2,200
synTerra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
DATE: 07/29/2020
UKE
BY: R. GRAZIANO DATE: 07/29/2020
t�ENERGY AAPRPOROVDMANAGERYLIE RSE DATE:07/29/2020
PROGRESS
www.synterracorp.com
FIGURE 6-8a
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 10 YEARS AFTER THE SOURCE
EXCAVATION WITH NINE EXTRACTION WELLS FOLLOWED
BY MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

L
LEGEND
EXTRACTION WELLS
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE
BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. EXTRACTION WELLS WERE TURNED OFF 5 YEARS AFTER EXCAVATION.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1983).
GRAPHIC SCALE
1,100 0 1,100 2,200
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANODATE: 07/29/2020
DUKE
It
EEN RGY
B. WYLIEDATE: 07/29/2020
APPRECT
MAN: WYLIE
PROGRESS
FIGURE 6-8b
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 20 YEARS AFTER THE SOURCE
EXCAVATION WITH NINE EXTRACTION WELLS FOLLOWED
BY MNA
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

.♦
LEGEND
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
- • • ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMER ASH DISPOSAL AREA BOUNDARY
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD 1963).
TR:
wib_�
->
n� o-
40
GRAPHIC SCALE
/rye �� 610 0 610 1,220
sy ■Terra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 06/10/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
DUKE CHECKED BY: R. DATE: 07/26/2020
ENERGY PROJECT BY: B.
B. WO
It LIE DATE: 07/26/2020
PROGRESS
www.synterracorp.com
FIGURE 6-9
PUMP AND TREAT SIMULATIONS WELL LAYOUT
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
N `°
GROUNDWATER FLOW DIRECTION
HYDRAULIC HEAD (FEET)
4
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
GRAPHIC SCALE
610 0 610 1,220
— FORMER ASH DISPOSAL AREA
synTerra
(IN FEET)
FORMER COAL PILE AREA
DRAWN BY: R. KIEKHAEFER DATE: 06/10/2020
— FORMER PROCESS AREA
DUKE
4ENERGY
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
APPROVED BY: B. WYLIE DATE: 07/26/2020
ONSITE LANDFILL BOUNDARY
PROJECT MANAGER: B. wvuE
PROGRESS
www.synterracorp.com
ONSITE LANDFILL COMPLIANCE BOUNDARY
-- SAND MINES
FIGURE 6-10
NOTES:
PUMP AND TREAT SIMULATIONS HYDRAULIC
1. ALL BOUNDARIES ARE APPROXIMATE.
HEADS AND FLOW FIELD (LAYER 8)
2. CONTOUR INTERVAL IS ONE FOOT. ARROWS INDICATE APPROXIMATE FLOW DIRECTION,
FLOW AND TRANSPORT MODELING REPORT
NOT MAGNITUDE.
L.V. SUTTON ENERGY COMPLEX
AERIAL3. PHOTOGRAPHYIL 42H90BTAINED FROM TERRA SERVER ON JUNE 17, 2019.IMAGE
COLLECTEDAPRI,0
WILMINGTON, NORTH CAROLINA
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 1200 NAD 1M AND NAVD 196E .

LEGEND
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
I
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
`
ASH BASIN WASTE BOUNDARY
-FORMERASH DISPOSALAREA
610 ORAPHICSCALE
610 1,220
-- FORMER COAL PILE AREA
synTerra
(IN FEET)
- FORMER PROCESS AREA
DRAWN BY: R. KIEKHAEFER DATE: 06/10/2020
ONSITE LANDFILL BOUNDARY
%� DUKE
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
ENERGY
APPROVED BY: B. WYLIE DATE: 07/29/2020
ONSITE LANDFILL COMPLIANCE BOUNDARY
PROJECT MANAGER: B. WYLIE
PROGRESS
SAND MINES
www.synterracorp.com
FIGURE 6-11
NOTES:
SIMULATED MAXIMUM BORON CONCENTRATIONS
1. ALL BOUNDARIES ARE APPROXIMATE.
AFTER APPROXIMATELY 30 YEARS OF PUMP AND
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
TREAT OPERATION 2050)
MODEL.
(YEAR
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17,2019. IMAGE
FLOW AND TRANSPORT MODELING REPORT
COLLECTED APRIL a, 2019.
L.V. SUTTON ENERGY COMPLEX
4. DRAWING HAS BEEN SET WITH APROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 21983)
WILMINGTON, NORTH CAROLINA

♦ ♦r
♦ - e
♦: �.
♦ ♦ �.
♦ ♦ .n
LEGEND
CLEAN WATER INFILTRATION WELLS
EXTRACTION WELLS
SELENIUM 20 — 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
—FORMER ASH DISPOSAL AREA
-- FORMER COAL PILE AREA
— FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. NO SELENIUM IS PRESENT ABOVE 20 Ng/L AFTER 30 YEARS.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD 1963).
IL
GRAPHIC SCALE
600 0 600 1,200
/rye ��
sy
(IN FEET)
DRAWN BY: R. KIEKHAEFER
REVISED BY: R. KIEKHAEFER
CHECKED BY: R. GRAZIANO
DATE: 06/10/2020
DATE: 07/29/2020
DATE: 07/29/2020
■Terra
DUKE
It
EEN RGY
B. WYLIE
APPRET
DATE: 07/29/2020
CMAN: WYLIE
PROGRESS
FIGURE 6-12
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
AFTER APPROXIMATELY 30 YEARS OF PUMP AND
TREAT OPERATION (YEAR 2050)
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
• SAMPLE LOCATION
HYDRAULIC HEAD (FEET)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
FORMERASH DISPOSALAREA
-- FORMER COAL PILE AREA
- FORMER PROCESS AREA
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
SAND MINES
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. CONTOUR INTERVAL IS 1 FOOT. HEADS ARE SHOWN POST -EXCAVATION FOR MODEL LAYER 8.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD 1983 AND NAVD 1988).
l�
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
330 0
330
660
(IN FEET)
DRAWN BY: R. KIEKHAEFER
DATE:
05/27/2020
REVISED BY: R. KIEKHAEFER
DATE:
07/26/2020
CHECKED BY: R. GRAZIANO
DATE:
07/26/2020
APPROVED BY: B. WYLIE
DATE:
07/26/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-13
LOCATION OF SOIL SAMPLES WITHIN FORMER 1984 ASH
BASIN AND SIMULATED HYDRAULIC HEADS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

"
26
°'Y`
31
24
16
45
15
-
•
22
15
35
64
83
•_
161
P
40
P
38
P
39
P
58
P
45
..,
I
40
20
116
117
32
.,.4 �
LL� ♦ ' A
52
53
48
125
135
60
'!'� '. •
85
140
178
81
58 120'
28
67
143
138
89
144
116
103
37 •
1. ♦
460
p
185
PPP
159
150
385
182
P
57 '
28 •
-�
134
lk p
98
P
92
P
365
P
205
P
163
P
165
P
99 40
P •
_z
151
114
112
198126 25
•
72 97
88 °'
56
250 41
*}
'
102 65 135 •
•
a
67 62
•
50 27 61 �
Jr
77 �� ♦
1r
• SAMPLE LOCATION (BORON pg/L)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
synTerra
%� DUKE
ENERGY
PROGRESS
GRAPHIC SCALE
240 0 240 480
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
APPROVED BY: B. WYLIE DATE: 07/26/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-14
VERTICALLY AVERAGED BORON SPLP CONCENTRATIONS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

l
P
P
P P P
P P
P P P
P P -
5 8 22
P P P
0 0 14 ��
P P
LEGEND
• SAMPLE LOCATION (ARSENIC pg/L)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
48
90
48
48 79
86 30
synTerra
%� DUKE
ENERGY
PROGRESS
1
GRAPHIC SCALE
240 0 240 480
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
APPROVED BY: B. WYLIE DATE: 07/26/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-15
VERTICALLY AVERAGED ARSENIC
SPLP CONCENTRATIONS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
• SAMPLE LOCATION (SELENIUM pg/L)
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
®
GRAPHIC SCALE
"
240 0 240 480
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER
REVISED BY: R. KIEKHAEFER
CHECKED BY: R,
DATE: 05/27/2020
DATE: 07/26/2020
DATE: 07/26/2020
DUKE
4�ENERGY
BY:GER:B.WYOLIE
DATE:07/26/2020
PROJECT MANAAPPRVD
PROGRESS
FIGURE 6-16
VERTICALLY AVERAGED SELENIUM
SPLP CONCENTRATIONS
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

191
•
253 y
220 170 112 325 105
155 105 253 459 599
1162 289 271 278 419
480 1033 993 643
3321 1336 1148 1083
ggg 704 661 2635
�a
1090 820 805
632
u
LEGEND
• SAMPLE LOCATION (BORON pg/L)
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
325
903
975
433
� ,
1040 838
744
267 {'�i • _ .
2780
1310 412 199
1477
1191
715- 289 �, �
1173
•
1430
906
177
516 700 �
RAwl
404
1805 296 �
9
736 469 971 ♦,
53 682 321 t
480 448
357 195 440
4 552
GRAPHIC SCALE
240 0 240 480
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER
REVISED BY: R. KIEKHAEFER
CHECKED BY: R. GRAZIANO
DATE: 05/27/2020
DATE: 07/26/2020
DATE: 07/26/2020
DUKE
It
ENERGY
APPROVEDBY: B.
DATE: 07/26/2020
PROJECT R: BEWYLIE
PROGRESS
FIGURE 6-17
CONVERTED PORE WATER CONCENTRATION OF BORON
ASSIGNED TO THE TOP 3 FEET OF SOIL IN THE 1984 ASH
BASIN FOOTPRINT IN 2019
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

V
..4
a
13
I
14
Y
P
-
l
P
P
P
P
P
•
n
13
37
p
p
24
281
p
p
41
32
71
♦ � Tc
pp
p126
p
p
10
166
: 6
;
101
n
52
380
188
92
34
♦
152
n
82
554
40
80
18
80
p34
25
260
454
2
„n
151
67
-
43
24
80
100
81 132 ;
16
144 51 �
c
, ..
♦
J 1C
21s
• SAMPLE LOCATION (ARSENIC pg/L)
ARSENIC 14 - 100 pg/L
ARSENIC > 100 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
240 0 240 480
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
APPROVED BY: B. WYLIE DATE: 07/26/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-18
CONVERTED PORE WATER CONCENTRATION OF
ARSENIC ASSIGNED TO THE TOP 3 FEET OF SOIL IN THE
1984 ASH BASIN FOOTPRINT IN 2019
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

P
P
P
P
k P
P
P
P
p
P
P
P
P18
23
P p
15
p
p P
P
P
P19
n
21
p94
n
_�
LEGEND
• SAMPLE LOCATION (SELENIUM pg/L)
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
10
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
240 0 240 480
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/27/2020
REVISED BY: R. KIEKHAEFER DATE: 07/26/2020
CHECKED BY: R. GRAZIANO DATE: 07/26/2020
APPROVED BY: B. WYLIE DATE: 07/26/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-19
CONVERTED PORE WATER CONCENTRATION OF
SELENIUM ASSIGNED TO THE TOP 3 FEET OF SOIL IN THE
1984 ASH BASIN FOOTPRINT IN 2019
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
0
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
240 0 240 480
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/28/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-20a
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 5 YEARS AFTER THE INITIAL
CALIBRATION SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
3. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1983).
A'
synTena
�
'DUKE ' ENERGY
PROGRESS
GRAPHIC SCALE
240 0 240 480
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/28/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-20b
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 10 YEARS AFTER THE INITIAL
CALIBRATION SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. SIMULATED BORON CONCENTRATIONS AFTER 20 YEARS DO NOT EXCEED 700 Pg/L.
3. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTEDAPRIL 4, 2019.
5. DRAWING S BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SA
FIPS 3200 (NAD 1983).
Ic'
synTena
�
'DUKE ' ENERGY
PROGRESS
GRAPHIC SCALE
240 0
240
480
(IN FEET)
DRAWN BY: R. KIEKHAEFER
DATE:
05/28/2020
REVISED BY: R. KIEKHAEFER
DATE:
07/29/2020
CHECKED BY: R. GRAZIANO
DATE:
07/29/2020
APPROVED BY: B. WYLIE
DATE:
07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-20c
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 20 YEARS AFTER THE INITIAL
CALIBRATION SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
BORON 700 - 4,000 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
7►69111110:1111111W_1►In]aI11111115610]►viI,II_V[@l@ii111►1o7_1:y7
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. SIMULATED BORON CONCENTRATIONS AFTER 20 YEARS DO NOT EXCEED 700 Ng/L.
3. BORON IS NATURALLY OCCURRING IN THE PEEDEE AND IS NOT REPRESENTED IN THE
MODEL.
4. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
5. DRAWING HAS BEEN SET WITH PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1983).
Ic'
synTena
�
'DUKE ' ENERGY
PROGRESS
GRAPHIC SCALE
240 0
240
480
(IN FEET)
DRAWN BY: R. KIEKHAEFER
DATE:
05/28/2020
REVISED BY: R. KIEKHAEFER
DATE:
07/29/2020
CHECKED BY: R. GRAZIANO
DATE:
07/29/2020
APPROVED BY: B. WYLIE
DATE:
07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-20d
SIMULATED MAXIMUM BORON CONCENTRATIONS
APPROXIMATELY 30 YEARS AFTER THE INITIAL
CALIBRATION SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

I r= ,r=mn
ARSENIC 14 - 100 pg/L
ARSENIC > 100 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
10 GRAPHIC SCALE
`J� 240 0 240 480
synTerra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/28/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
DUKE CHECKED BY: R.
GRAZIAN
DATE: 07/29/2020
OLIE
It EENERGY APPRECTMAN: B. WYLIE
WYDATE: 07/29/2020
PROGRESS
FIGURE 6-21a
SIMULATED MAXIMUM ARSENIC CONCENTRATIONS
APPROXIMATELY 5 YEARS AFTER THE INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
ARSENIC 14 - 100 pg/L
ARSENIC > 100 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
®
GRAPHIC SCALE
" `J�
240 0 240 480
synTerra
(IN FEET)
DRAWN BY: R. KIEKHAEFER
REVISED BY: R. KIEKHAEFER
CHECKED BY: R. GRAZIANO
DATE: 05/28/2020
DATE: 07/29/2020
DATE: 07/29/2020
DUKE
It
EENERGY
APPRECTMAN: B. WYLIE
DATE: 07/29/2020
WYLIE
PROGRESS
FIGURE 6-21b
SIMULATED MAXIMUM ARSENIC CONCENTRATIONS
APPROXIMATELY 10 YEARS AFTER INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

FA
LEGEND
ARSENIC 14 - 100 pg/L
ARSENIC > 100 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIRS 3200 (NAD 1983).
•
v, -
GRAPHIC SCALE
240 0 240 480
//���� �y����y�
(IN FEET)
DRAWN BY: R. KIEKHAEFER
REVISED BY: R. KIEKHAEFER
CHECKED BY: R. GRAZIANO
DATE: 05/28/2020
DATE: 07/29/2020
DATE: 07/29/2020
✓y ■ ■Ted � M
DUKE
*'EN
RGY
B. WYLIE
APPRECT
DATE: 07/29/2020
MAN: WYLIE
PROGRESS
FIGURE 6-21c
SIMULATED MAXIMUM ARSENIC CONCENTRATIONS
APPROXIMATELY 20 YEARS AFTER THE INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

Oil-
•
♦
•
•
d
F ,
a
•
•
i Pr_l=tin
ARSENIC 14 - 100 pg/L
ARSENIC > 100 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
�® GRAPHIC SCALE
240 0 240 480
synTerra (IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/28/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
DUKE CHECKED BY: R.
GRAZIAN
DATE: 07/29/2020
OLIE
It EENERGY APPRECTMAN: B. WYLIE
WYDATE: 07/29/2020
PROGRESS
FIGURE 6-21d
SIMULATED MAXIMUM ARSENIC CONCENTRATIONS
APPROXIMATELY 30 YEARS AFTER THE INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

ors
E
LEGEND
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
40
synTerra
t
DUKE
IENERGY
PROGRESS
•
GRAPHIC SCALE
240 0 240 480
(IN FEET)
DRAWN BY: R. KIEKHAEFER DATE: 05/28/2020
REVISED BY: R. KIEKHAEFER DATE: 07/29/2020
CHECKED BY: R. GRAZIANO DATE: 07/29/2020
APPROVED BY: B. WYLIE DATE: 07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-22a
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 5 YEARS AFTER THE INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 1983).
L�
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
240 0
240
480
(IN FEET)
DRAWN BY: R. KIEKHAEFER
DATE:
05/28/2020
REVISED BY: R. KIEKHAEFER
DATE:
07/29/2020
CHECKED BY: R. GRAZIANO
DATE:
07/29/2020
APPROVED BY: B. WYLIE
DATE:
07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-22b
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 10 YEARS AFTER THE INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1983).
l�
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
240 0
240
480
(IN FEET)
DRAWN BY: R. KIEKHAEFER
DATE:
05/28/2020
REVISED BY: R. KIEKHAEFER
DATE:
07/29/2020
CHECKED BY: R. GRAZIANO
DATE:
07/29/2020
APPROVED BY: B. WYLIE
DATE:
07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-22c
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 20 YEARS AFTER THE INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

LEGEND
SELENIUM 20 - 139 pg/L
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN WASTE BOUNDARY
ONSITE LANDFILL BOUNDARY
ONSITE LANDFILL COMPLIANCE BOUNDARY
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. AERIAL PHOTOGRAPHY OBTAINED FROM TERRA SERVER ON JUNE 17, 2019. IMAGE
COLLECTED APRIL 4, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM PIPS 3200 (NAD 1983).
0
synTerra
t
DUKE
IENERGY
PROGRESS
GRAPHIC SCALE
240 0
240
480
(IN FEET)
DRAWN BY: R. KIEKHAEFER
DATE:
05/28/2020
REVISED BY: R. KIEKHAEFER
DATE:
07/29/2020
CHECKED BY: R. GRAZIANO
DATE:
07/29/2020
APPROVED BY: B. WYLIE
DATE:
07/29/2020
PROJECT MANAGER: B. WYLIE
FIGURE 6-22d
SIMULATED MAXIMUM SELENIUM CONCENTRATIONS
APPROXIMATELY 30 YEARS AFTER THE INITIAL
CALIBRATED SIMULATION
FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
WILMINGTON, NORTH CAROLINA

Updated Groundwater Flow And Transport Modeling Report August 2020
L.V. Sutton Energy Complex - Duke Energy Progress, LLC
TABLES

TABLE 5-1
CALIBRATED PRE -EXCAVATION HYDRAULIC CONDUCTIVITY PARAMETERS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Hydrostratigraphic Unit
Model
Layers
Spatial Zones
(number corresponds to
Figures 5-1 through 5-5)
Horizontal
Hydraulic
Conductivity
(ft/d)
Anisotropy
Ratio,
K":Kv
Ash Basins
1-2
#1
1.5
2
Upper Surficial
3-6
#1 FADA Ash
1.5
2
3-6
#2
40
10
3-10
#3
1.5
2
7-8
#4
60
10
9-10
#5
70
10
Pee Dee Confining Unit (where present)
11
#1
0.01
5
Or Lower Surficial
11
#2
1.5
2
11
#3
30
10
11
#4
125
10
11
#5
800
10
Upper Pee Dee
12
#1
1.5
2
12
#2
30
10
12
#3
125
10
12
#4
800
10
13-15
#5
0.10
10
Lower Pee Dee
16-17
#1
0.01
10
18
#2
30
10
Notes:
ft/d - feet per day
Kh - horizontal hydraulic conductivity
Kh/K, - horizontal hydraulic conductivity divided by vertical hydraulic conductivity
Prepared by: RLK Checked by: RAG
Page 1 of 1

TABLE 5-2
CALIBRATED POST -EXCAVATION HYDRAULIC CONDUCTIVITY PARAMETERS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Hydrostratigraphic Unit
Model
Layers
Spatial Zones
(number corresponds to
Figures 5-6 through 5-10)
Horizontal
Hydraulic
Conductivity
(ft/d)
Anisotropy
Ratio,
K":K"
Ash Basins
1-2
#1
1000
2
Upper Surficial
3-6
#1 FADA Ash
1.50
2
3-6
#2
40
10
3-8
#3
10000
3
7-8
#4
60
10
7-8
#5
30000
3
9-10
#6
70
10
9-10
#7
10000
2
Pee Dee Confining Unit (where present)
11
#1
0.01
5
Or Lower Surficial
11
#2
30
10
11
#3
125
10
11
#4
10000
3
11
#5
800
10
Upper Pee Dee
12
#1
30
10
12
#2
125
10
12
#3
10000
3
12
#4
800
10
13-15
#5
0.10
10
Lower Pee Dee
16-17
#1
0.01
10
18
#2
30
10
Notes:
ft/d - feet per day
Kh - horizontal hydraulic conductivity
Kh/K­ horizontal hydraulic conductivity divided by vertical hydraulic conductivity
Prepared by: WTP Checked by: RLK
Page 1 of 1

TABLE 5-3
OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE
CALIBRATED FLOW MODEL FOR PRE -EXCAVATION CONDITIONS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Head
(ft)
Computed Head
(ft)
Residual Head
(ft)
ABMW-02D
7.50
7.46
0.04
ABMW-02S
7.57
7.47
0.10
AW-01 B
12.25
11.17
1.08
AW-01C
12.21
11.16
1.05
AW-02B
12.65
11.16
1.49
AW-02D
10.79
11.13
-0.34
AW-03B
11.91
11.21
0.70
AW-03C
11.92
11.20
0.72
AW-04B
10.59
10.69
-0.10
AW-04C
10.56
10.68
-0.12
AW-05B
9.99
10.41
-0.42
AW-05C
9.99
10.41
-0.42
AW-05D
10.03
10.39
-0.36
AW-05E
9.97
10.34
-0.37
AW-06B
10.92
10.98
-0.06
AW-06R-D
9.68
10.95
-1.27
AW-06R-E
9.67
10.83
-1.16
AW-07R-D
9.22
11.22
-2.00
AW-08B
9.62
9.38
0.24
AW-08C
9.69
9.37
0.32
AW-09B
8.20
8.46
-0.26
AW-09C
8.08
8.45
-0.37
AW-09D
8.05
8.46
-0.41
CCR-102B
8.85
9.43
-0.58
CCR-102C
8.94
9.43
-0.49
CCR-103B
8.64
9.01
-0.37
CCR-103C
8.66
9.01
-0.35
CCR-103D
8.35
9.05
-0.70
CCR-104B
8.51
8.79
-0.28
CCR-104C
8.57
8.79
-0.22
CCR-104D
8.51
8.85
-0.34
CCR-105B
8.50
8.75
-0.25
CCR-105C
8.52
8.74
-0.22
CCR-105D
8.41
8.80
-0.39
CCR-106B
8.52
8.74
-0.22
CCR-106C
8.50
8.73
-0.23
CCR-106D
8.50
8.78
-0.28
CCR-107B
8.44
8.59
-0.15
CCR-107C
8.43
8.58
-0.15
CCR-107D
8.29
8.62
-0.33
CCR-108B
8.48
8.56
-0.08
CCR-108C
8.54
8.59
-0.05
CCR-108D
1 8.42
1 8.68
1-0.26
Page 1 of 4

TABLE 5-3
OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE
CALIBRATED FLOW MODEL FOR PRE -EXCAVATION CONDITIONS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Head
(ft)
Computed Head
(ft)
Residual Head
(ft)
CCR-109B
8.57
8.99
-0.42
CCR-109C
8.60
8.99
-0.39
CCR-109D
8.49
9.05
-0.56
CCR-110B
8.51
8.65
-0.14
CCR-110C
8.53
8.66
-0.13
CCR-110D
8.51
8.75
-0.24
CCR-111B
8.54
8.67
-0.13
CCR-111C
8.56
8.69
-0.13
CCR-111D
8.54
8.78
-0.24
CCR-112B
8.48
8.88
-0.40
CCR-112C
8.48
8.91
-0.43
CCR-112D
8.48
9.03
-0.55
CCR-113B
8.53
9.05
-0.52
CCR-113C
8.54
9.15
-0.61
CCR-113D
8.50
9.11
-0.61
CCR-114B
9.13
9.26
-0.13
CCR-114C
9.09
9.26
-0.17
CCR-114D
9.05
9.30
-0.25
CCR-115B
9.75
9.91
-0.16
CCR-115C
9.79
9.90
-0.11
CCR-115D
9.74
9.91
-0.17
CCR-116B
10.32
10.29
0.03
CCR-116C
10.36
10.28
0.08
CCR-117B
10.08
10.50
-0.42
CCR-117C
10.16
10.50
-0.34
CCR-118B
10.08
10.71
-0.63
CCR-118C
10.12
10.71
-0.59
CCR-119B
10.08
10.91
-0.83
CCR-119C
10.06
10.89
-0.83
CCR-120B
10.26
11.04
-0.78
CCR-120C
10.37
11.02
-0.65
CCR-121 B
10.40
11.11
-0.71
CCR-121C
10.46
11.10
-0.64
CCR-122B
10.38
11.07
-0.69
CCR-122C
10.35
11.05
-0.70
CCR-123B
10.11
10.88
-0.77
CCR-123C
10.00
10.87
-0.87
CCR-124B
9.77
10.69
-0.92
CCR-124C
9.77
10.70
-0.93
GWPZ-0IAPZ-1A
9.83
10.04
-0.21
GWPZ-0IBPZ-1B
9.77
10.03
-0.26
M W-04
8.15
8.57
-0.42
M W-04A
1 8.03
1 8.57
1 -0.54 ___j
Page 2 of 4

TABLE 5-3
OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE
CALIBRATED FLOW MODEL FOR PRE -EXCAVATION CONDITIONS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Head
(ft)
Computed Head
(ft)
Residual Head
(ft)
M W-04B
8.05
8.56
-0.51
MW-05A
9.08
8.82
0.26
MW-05B
9.08
8.82
0.26
MW-05C
9.00
8.82
0.18
MW-05CD
8.91
8.79
0.12
M W-05 D
8.54
8.79
-0.25
MW-05R-E
8.80
9.49
-0.69
M W-07A
8.70
8.77
-0.07
M W-07B
8.75
8.76
-0.01
MW-07C
8.52
8.75
-0.23
M W-08
8.83
9.11
-0.28
M W-08E
8.47
9.79
-1.32
M W-09
10.84
10.47
0.37
M W-11
11.03
11.17
-0.14
M W-12
10.93
10.97
-0.04
M W-19
9.40
10.03
-0.63
MW-20
4.46
3.95
0.51
M W-20D
4.37
3.92
0.45
MW-21C
9.39
9.81
-0.42
M W-22B
10.00
10.66
-0.66
MW-22C
9.98
10.66
-0.68
MW-23B
10.51
10.91
-0.40
MW-23C
10.54
10.91
-0.37
MW-23D
10.10
10.89
-0.79
M W-23E
10.69
10.78
-0.09
MW-24RB
10.54
11.00
-0.46
MW-24RC
10.70
10.99
-0.29
MW-27B
10.03
9.75
0.28
MW-27C
9.43
9.74
-0.31
M W-28B
9.29
9.48
-0.19
MW-28C
9.30
9.46
-0.16
M W-28T
9.28
9.47
-0.19
MW-31B
11.20
11.23
-0.03
MW-31R-C
9.23
11.24
-2.01
MW-32C
9.68
10.19
-0.51
MW-33C
9.46
10.12
-0.66
M W-36B
9.50
9.78
-0.28
MW-36C
9.48
9.77
-0.29
M W-37B
7.49
8.35
-0.86
MW-37C
7.64
8.35
-0.71
MW-37CD
7.57
8.40
-0.83
M W-37D
7.79
8.41
-0.62
M W-37E
1 7.73
1 8.80
1 -1.07 _j
Page 3 of 4

TABLE 5-3
OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE
CALIBRATED FLOW MODEL FOR PRE -EXCAVATION CONDITIONS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Head
(ft)
Computed Head
(ft)
Residual Head
(ft)
M W-38B
9.48
9.54
-0.06
MW-38C
9.39
9.54
-0.15
M W-38D
9.40
9.95
-0.55
M W-39B
8.71
8.64
0.07
MW-39C
8.67
8.65
0.02
M W-39D
8.53
8.72
-0.19
M W-40B
9.38
9.38
0.00
MW-40C
9.42
9.38
0.04
MW-40D
9.33
9.42
-0.09
PZ-06D
9.92
10.91
-0.99
PZ-06S
10.90
10.93
-0.03
PZ-10D
10.12
10.24
-0.12
PZ-10S
10.99
10.25
0.74
SMW-01B
10.13
10.32
-0.19
SMW-01C
9.68
10.31
-0.63
SMW-02B
10.16
10.08
0.08
SMW-02C
10.14
10.08
0.06
SMW-03B
9.88
9.69
0.19
SMW-03C
9.88
9.69
0.19
SMW-04B
11.07
11.32
-0.25
SMW-04C
11.06
11.32
-0.26
SMW-05B
10.30
10.77
-0.47
SMW-05C
10.44
10.76
-0.32
SMW-06B
10.19
10.15
0.04
SMW-06C
10.11
10.14
-0.03
SMW-06D
1 10.39
1 10.22
1 0.17
Notes:
Ft - feet
Ft. NAVD 88 - North American Vertical Datum of 1988
Prepared by: WTP Checked by: RAG
Page 4 of 4

TABLE 5-4
OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE
CALIBRATED FLOW MODEL FOR POST -EXCAVATION CONDITIONS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Head
(ft)
Computed Head
(ft)
Residual Head
(ft)
AW-01C
9.29
9.19
0.10
AW-02C
7.00
8.84
-1.84
AW-02D
9.59
8.90
0.69
AW-03C
8.01
8.62
-0.61
AW-04B
8.31
7.60
0.71
AW-04C
8.15
7.44
0.71
AW-05C
8.12
7.25
0.87
AW-05D
8.17
7.41
0.76
AW-06R-B
8.84
7.99
0.85
AW-06RD
8.78
8.06
0.72
AW-06R-E
8.72
8.71
0.01
AW-07RD
7.88
8.63
-0.75
AW-08B
8.88
8.92
-0.04
AW-08C
9.12
8.91
0.21
AW-09B
7.51
7.86
-0.35
AW-09C
7.56
7.85
-0.29
AW-09D
7.48
7.88
-0.40
CCR-109B
8.11
8.38
-0.27
CCR-109C
8.10
8.37
-0.27
CCR-109D
8.05
8.42
-0.37
CCR-114B IMP
8.66
8.64
0.02
CCR-114C IMP
8.35
8.64
-0.29
CCR-114D
8.64
8.69
-0.05
CCR-115B IMP
8.81
8.85
-0.04
CCR-115C IMP
8.68
8.84
-0.16
CCR-115D
8.82
8.88
-0.06
FPA-02B
8.40
8.29
0.11
FPA-02C
8.58
8.29
0.29
FPA-03B
8.39
8.21
0.18
FPA-03C
8.09
8.19
-0.10
FPA-04B
8.27
8.25
0.02
FPA-04C
8.44
8.25
0.19
FPA-09B
8.28
8.29
-0.02
FPA-09C
8.29
8.28
0.00
MW-05B
8.23
8.70
-0.47
MW-05C
8.52
8.69
-0.17
M W-05CD
8.95
8.68
0.27
MW-05D
8.30
8.71
-0.41
MW-05RE
8.79
9.40
-0.61
MW-07A
7.91
8.04
-0.13
MW-07B
8.00
8.03
Page 1 of 3

TABLE 5-4
OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE
CALIBRATED FLOW MODEL FOR POST -EXCAVATION CONDITIONS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Head
(ft)
Computed Head
(ft)
Residual Head
(ft)
MW-07C
7.97
8.02
-0.05
MW-08
8.98
8.89
0.09
MW-08B
8.91
8.91
0.00
MW-08D
8.98
8.96
0.02
MW-08E
9.46
9.62
-0.16
MW-11
7.94
8.96
-1.02
MW-12R
8.77
7.95
0.82
MW-15RB
6.44
6.35
0.09
MW-15RC
6.41
6.33
0.08
MW-16
9.31
7.80
1.51
MW-16D
9.22
7.78
1.44
MW-19
8.33
8.21
0.12
M W-20
5.14
3.93
1.21
MW-20D
5.11
3.95
1.16
MW-21C
8.36
8.23
0.13
MW-22B
8.50
8.16
0.34
M W-22C
8.48
8.15
0.33
MW-23B
8.53
8.26
0.27
M W-23C
8.48
8.25
0.23
MW-23D
8.47
8.29
0.18
MW-23E
8.60
8.82
-0.22
MW-24RB
8.63
8.66
-0.03
MW-24RC
8.63
8.65
-0.02
MW-27B
8.94
8.90
0.04
M W-27C
8.90
8.89
0.01
MW-28B
8.34
8.22
0.12
MW-28C
8.36
8.21
0.15
MW-31RC
7.87
8.44
-0.57
MW-32C
8.61
7.88
0.73
MW-33C
8.25
7.87
0.38
M W-36B
8.87
8.84
0.03
MW-36C
8.88
8.83
0.05
M W-37B
7.10
8.07
-0.97
MW-37C
7.16
8.07
-0.91
MW-37CD
7.33
8.12
-0.79
MW-37D
7.40
8.13
-0.73
MW-37E
7.28
8.58
-1.30
MW-38B
9.01
8.91
0.10
M W-38C
8.93
8.90
0.03
MW-38D
8.98
9.47
-0.49
MW-39B
8.64
8.49
0.15 11
Page 2 of 3

TABLE 5-4
OBSERVED, COMPUTED, AND RESIDUAL HEADS FOR THE
CALIBRATED FLOW MODEL FOR POST -EXCAVATION CONDITIONS
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Head
(ft)
Computed Head
(ft)
Residual Head
(ft)
MW-39C
8.20
8.49
-0.29
MW-39D
8.25
8.55
-0.30
MW-40B
8.84
8.72
0.12
MW-40C
8.08
8.71
-0.63
MW-40D
8.87
8.76
0.11
MW-41B
8.59
8.57
0.02
MW-41C
8.72
8.57
0.15
M W-41 D
8.72
8.64
0.08
MW-41E
8.96
9.39
-0.43
MW-42B CCR
8.27
7.67
0.60
MW-42C CCR
8.29
7.66
0.63
MW-42D CCR
8.20
7.74
0.46
MW-43B
3.43
4.92
-1.49
M W-43C
3.52
4.88
-1.36
MW-44B
3.10
3.58
-0.47
MW-44C
2.92
3.41
-0.50
M W-45B
3.73
2.26
1.47
MW-45C
3.59
2.46
1.13
M W-46B
5.16
5.31
-0.15
M W-46C
5.17
5.28
-0.11
MW-50B
4.89
5.56
-0.67
MW-50C
4.94
5.56
-0.61
SMW-01B
8.87
8.09
0.78
SMW-01C
8.99
8.08
0.91
SMW-02C
8.68
8.00
0.68
SMW-03C
8.68
8.11
0.57
SMW-04C
8.23
8.99
-0.76
SMW-05C
10.18
8.56
1.62
SMW-06B
9.98
8.33
1.65
SMW-06C
9.86
8.29
1.57
SMW-06D
10.17
8.82
1.35
Notes:
Ft - feet
Ft. NAVD 88 - North American Vertical Datum of 1988
Prepared by: WTP Checked by: RAG
Page 3 of 3

TABLE 5-5
FLOW MODEL SENSITIVITY ANALYSIS (2017)
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Parameter
Decreased by 1/2
Calibrated
Increased by 2
Recharge
6.54%
Upper Surficial Kh (40-70 ft/d)
7.47%
6.54%
10.38%
Lower Surficial Kh (125 ft/d)
7.61%
6.54%
8.94%
Upper Pee Dee Kh (0.1 ft/d)
6.61%
6.54%
6.48%
Low Pee Dee Kh (0.01 ft/d)
6.56%
6.54%
6.46%
Lower Pee Dee Kh (30 ft/d)
6.40%
6.54%
6.63%
Prepared by: WTP Checked by: RAG
Notes•
Parameters are multiplied by 0.5 or 2 and the NRMSE is calculated.
Results are expressed as normalized root mean square error (NRMSE) of the simulated and observed heads.
Kh — horizontal hydraulic conductivity
ft/d — feet per day
Page 1 of 1

TABLE 5-6
FLOW MODEL SENSITIVITY ANALYSIS (2019)
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Parameter
Decreased by 1/2
Calibrated
Increased by 2
Recharge
9.03%
Upper Surficial Kh (40-70 ft/d)
12.02%
9.03%
12.54%
Lower Surficial Kh (125 ft/d)
11.14%
9.03%
12.00%
Upper Pee Dee Kh (0.1 ft/d)
9.00%
9.03%
9.03%
Low Pee Dee Kh (0.01 ft/d)
9.06%
9.03%
9.01%
Lower Pee Dee Kh (30 ft/d)
1 9.02%
1 9.03%
1 9.06%
Prepared by: WTP Checked by: RAG
Notes•
Parameters are multiplied by 0.5 or 2 and the NRMSE is calculated.
Results are expressed as normalized root mean square error (NRMSE) of the simulated and observed heads.
Kh - horizontal hydraulic conductivity
ft/d - feet per day
Page 1 of 1

TABLE 5-7A
ASH BASIN BORON SOURCE CONCENTRATIONS (Ng/L) USED IN PRE -EXCAVATION
HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Boron
Polygon
FCPA
FADA
FPA
1971-1984
1984 Ash
Basin
1984-2013
1984 Ash
Basin
2013-2017
1984 Ash
Basin
1971-1984
1971 Ash
Basin
1984-2013
1971 Ash
Basin
2013-2017
1971 Ash
Basin
1971 Ash
Basin
(Deep)
1
200
-
-
-
-
-
2
--
200
-
--
--
--
--
--
--
3
--
--
200
--
--
--
--
--
--
4
--
--
--
0
1200
800
--
--
--
--
5
--
--
-
0
1200
800
--
--
--
--
6
--
--
-
0
2000
1500
--
--
--
--
7
--
--
-
--
--
--
2500
2000
1500
--
8
--
--
-
--
-
-
-
-
-
2000
Notes:
Location of each source zone is identified in Figure 5-15a
Prepared by: WTP Checked by: RAG
Page 1 of 1

TABLE 5-7B
ASH BASIN SELENIUM SOURCE CONCENTRATIONS (Ng/L) USED IN PRE -EXCAVATION
HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Selenium
Polygon
FCPA
FADA
FPA
1971-1984
1984 Ash Basin
1984-2013
1984 Ash Basin
2013-2017
1984 Ash Basin
1971 Ash Basin
1971 Ash Basin
(Deep)
1
0
--
--
--
--
--
--
--
2
--
0
--
--
--
--
--
--
3
--
--
0
--
--
--
--
--
4
--
--
--
0
160
160
--
--
5
--
--
--
0
0
0
--
--
6
--
--
--
0
0
0
--
--
7
--
--
--
--
--
--
0
--
8
--
--
--
--
--
--
--1
0
Notes:
Location of each source zone is identified in Figure 5-15a
Prepared by: WTP Checked by: RAG
Page 1 of 1

TABLE 5-8A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
ABMW-02D
823
1830
ABMW-02S
159
200
AW-05B
0
4
AW-05C
0
173
AW-05D
355
0
AW-05E
2010
0
AW-06RB
0
15
AW-06RD
806
0
AW-06RE
2010
0
AW-07D
809
0
AW-07RD
779
0
AW-09C
328
0
AW-09D
668
0
BMW-01
0
7
BMW-02
0
38
BMW-03
0
31
BMW-04
0
134
CCR-102B
206
936
CCR-102C
2620
1374
CCR-103B
1240
1475
CCR-103C
2950
1645
CCR-103D
775
0
CCR-104B
1490
1496
CCR-104C
815
1752
CCR-104D
853
0
CCR-105C
1390
1756
CCR-105D
1050
0
CCR-106B
625
1444
CCR-106C
361
1764
CCR-106D
944
0
CCR-107B
354
1491
CCR-107C
573
1786
CCR-107D
1180
0
CCR-108B
371
998
CCR-108C
245
1660
CCR-108D
836
0
CCR-109B
528
1389
CCR-109C
1190
1650
CCR-109D
1260
0
CCR-110B
3260
1261
CCR-110C
1760
1782
Page 1 of 4

TABLE 5-8A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
CCR-110D
834
0
CCR-111B
3210
1038
CCR-111C
2100
1780
CCR-111 D
709
0
CCR-112B
2550
622
CCR-112C
1160
1323
CCR-112D
640
0
CCR-113B
337
712
CCR-113C
427
986
CCR-113D
1030
0
CCR-114B
150
256
CCR-114C
180
528
CCR-114D
1020
0
CCR-115B
0
224
CCR-115C
474
268
CCR-115D
671
0
CCR-116B
0
60
CCR-116C
352
158
CCR-117B
0
49
CCR-117C
252
247
CCR-118B
0
65
CCR-118C
293
328
CCR-119B
83
113
CCR-119C
871
423
CCR-120B
0
159
CCR-120C
810
625
CCR-121B
0
186
CCR-121C
142
579
CCR-122B
0
101
CCR-122C
2010
814
CCR-123B
0
208
CCR-123C
767
378
CCR-124B
0
305
CCR-124C
860
1276
CCR-201C
0
43
CCR-201D
418
0
CCR-202C
225
95
CCR-202D
566
0
CCR-203C
1310
186
CCR-203D
534
0
Page 2 of 4

TABLE 5-8A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
CCR-204C
180
96
CCR-204D
446
0
CCR-205C
1240
1051
CCR-205D
810
0
CCR-206C
231
580
CCR-206D
687
0
CCR-207C
214
253
CCR-207D
467
0
CCR-208C
0
88
CCR-208D
767
0
DMW-01
0
5
DMW-03
0
16
GWPZ-01A
0
43
GWPZ-01B
0
67
MW-04A
0
0
MW-05A
0
0
MW-05B
0
0
MW-05C
0
0
MW-05CD
1190
0
MW-05D
2640
0
MW-05RE
780
0
MW-07C
536
1
MW-08
0
0
MW-08E
4480
0
MW-11
0
35
MW-19
888
705
MW-21C
1110
649
MW-22B
0
116
MW-22C
1970
922
MW-23B
0
125
MW-23C
365
544
MW-23D
902
0
MW-23E
2550
0
MW-24RB
0
77
MW-24RC
330
360
MW-27B
0
71
MW-27C
329
175
MW-28B
0
8
MW-28C
0
75
MW-31C
1500
180
Page 3 of 4

TABLE 5-8A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
MW-31RC
1340
138
MW-32C
54
22
MW-33C
0
14
MW-36B
0
105
MW-36C
393
259
MW-37B
0
0
MW-37C
0
0
MW-37CD
60
0
MW-37D
140
0
MW-37E
1460
0
MW-38B
0
22
MW-38C
290
120
MW-38D
1560
0
MW-39B
0
7
MW-39C
0
105
MW-39D
1080
0
MW-40B
0
78
MW-40C
479
357
MW-40D
1220
0
MW-41E
4320
0
PZ-06D
769
0
PZ-10D
483
0
SMW-01B
318
31
SMW-01C
780
276
SMW-03C
306
69
SMW-04C
0
0
SMW-06B
70
26
SMW-06C
298
186
SMW-06D
1120
0
Prepared by: WTP Checked by: RAG
Notes•
Observation data from July 2017
C= monitoring wells within the Peedee with naturally occuring boron; not included in the calibration
Page 4 of 4

TABLE 5-8B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
ABMW-02D
0
0
ABMW-02S
0
0
AW-05B
0
0
AW-05C
0
0
AW-05D
0
0
AW-05E
0
0
AW-06RB
0
0
AW-06RD
0
0
AW-06RE
0
0
AW-07D
0
0
AW-07RD
0
0
AW-09C
0
0
AW-09D
0
0
BMW-01
1
0
BMW-02
0
0
BMW-03
0
0
BMW-04
0
0
CCR-102B
0
0
CCR-102C
0
0
CCR-103B
0
0
CCR-103C
0
0
CCR-103D
0
0
CCR-104B
0
0
CCR-104C
0
0
CCR-104D
0
0
CCR-105C
0
0
CCR-105D
0
0
CCR-106B
0
0
CCR-106C
0
0
CCR-106D
0
0
CCR-107B
0
0
CCR-107C
0
0
CCR-107D
0
0
CCR-108B
0
0
CCR-108C
0
0
CCR-108D
0
0
CCR-109B
0
0
CCR-109C
0
0
CCR-109D
0
0
CCR-110B
0
0
Page 1 of 4

TABLE 5-8B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
CCR-110C
0
0
CCR-110D
0
0
CCR-111B
0
0
CCR-111C
0
0
CCR-111D
0
0
CCR-112B
0
0
CCR-112C
0
0
CCR-112D
0
0
CCR-113B
0
3
CCR-113C
0
5
CCR-113D
0
0
CCR-114B
0
39
CCR-114C
63
55
CCR-114D
0
0
CCR-115B
2
36
CCR-115C
15
23
CCR-115D
0
0
CCR-116B
0
4
CCR-116C
17
1
CCR-117B
2
1
CCR-117C
3
0
CCR-118B
2
0
CCR-118C
0
0
CCR-119B
2
0
CCR-119C
0
0
CCR-120B
0
0
CCR-120C
0
0
CCR-121B
1
0
CCR-121C
3
0
CCR-122B
0
0
CCR-122C
0
0
CCR-123B
0
0
CCR-123C
0
0
CCR-124B
13
0
CCR-124C
0
0
CCR-201C
0
0
CCR-201D
0
0
CCR-202C
0
0
CCR-202D
0
0
CCR-203C
2
0
Page 2 of 4

TABLE 5-8B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
CCR-203D
0
0
CCR-204C
0
0
CCR-204D
0
0
CCR-205C
0
0
CCR-205D
0
0
CCR-206C
0
0
CCR-206D
0
0
CCR-207C
0
0
CCR-207D
0
0
CCR-208C
1
0
CCR-208D
0
0
DMW-01
0
0
DMW-03
0
0
GWPZ-01A
0
6
GWPZ-01B
4
10
M W-04A
0
0
MW-05A
0
0
MW-05B
0
0
MW-05C
0
0
MW-05CD
0
0
MW-05D
0
0
MW-05RE
0
0
MW-07C
0
0
MW-08
0
0
MW-08E
0
0
MW-11
0
0
MW-19
0
0
MW-21C
0
0
MW-22B
0
0
MW-22C
0
0
MW-23B
1
0
MW-23C
8
0
MW-23D
0
0
MW-23E
0
0
MW-24RB
0
0
MW-24RC
0
0
MW-27B
6
2
MW-27C
36
1
MW-28B
0
0
MW-28C
0
0
Page 3 of 4

TABLE 5-8B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (lag/L) IN MONITORING WELLS
FOR PRE -EXCAVATION HISTORICAL TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
MW-31C
0
0
MW-31RC
0
0
MW-32C
0
0
MW-33C
0
0
MW-36B
0
13
MW-36C
37
6
MW-37B
0
0
MW-37C
0
0
MW-37CD
0
0
MW-37D
0
0
MW-37E
0
0
MW-38B
0
0
MW-38C
19
0
MW-38D
0
0
MW-39B
0
0
MW-39C
0
3
MW-39D
0
0
MW-40B
0
9
M W-40C
40
20
MW-40D
0
0
MW-41E
0
0
PZ-06D
0
0
PZ-10D
0
0
SMW-01B
0
0
SMW-01C
0
0
SMW-03C
0
0
SMW-04C
0
0
SMW-06B
0
0
SMW-06C
0
0
SMW-06D
0
0
Notes:
Observation data from July 2017
Prepared by: WTP Checked by: RAG
Page 4 of 4

TABLE 5-9A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
ABMW-02D
739
1697
ABM W-02S
123
193
AW-03C
121
14
AW-04C
581
285
AW-05C
0
133
AW-06RD
821
0
AW-07RD
763
0
AW-08C
0
26
AW-09C
222
0
BMW-01
0
7
BMW-02
103
32
BMW-03
0
17
BMW-04
243
88
CCR-109B
818
948
CCR-109C
1940
1552
CCR-109D
1360
0
CCR-110B IMP
3120
1081
CCR-110C IMP
1950
1729
CCR-110D
898
0
CCR-111B
3110
861
CCR-111C
1850
1731
CCR-111D
762
0
CCR-112B IMP
1050
742
CCR-112C IMP
821
1221
CCR-112D
725
0
CCR-113B
364
632
CCR-113C
264
755
CCR-113D
1040
0
CCR-114B IMP
84
141
CCR-114C IMP
77
261
CCR-114D
1180
0
CCR-115B IMP
0
119
CCR-115C IMP
280
122
CCR-115D
821
0
CCR-116B
70
46
CCR-116C
252
75
CCR-117B
0
48
CCR-117C
161
122
CCR-118B
0
60
CCR-118C
55
177
CCR-119B
66
96
CCR-119C
248
339
Page 1 of 4

TABLE 5-9A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
CCR-120B
0
119
CCR-120C
1000
668
CCR-121B
0
146
CCR-121 C
191
574
CCR-122B
0
87
CCR-122C
1070
700
CCR-123B
0
153
CCR-123C
56
336
CCR-124B
0
340
CCR-124C
202
907
CCR-201 C
0
24
CCR-201D
369
0
CCR-202C
108
15
CCR-202D
668
0
CCR-203C
391
18
CCR-203D
606
0
CCR-204C
224
70
CCR-204D
490
1
CCR-205C
688
778
CCR-205D
828
0
CCR-206C
327
395
CCR-206D
740
0
CCR-207C
112
160
CCR-207D
602
0
CCR-208C
0
48
CCR-208D
883
0
DMW-01
0
7
DMW-02
0
17
DMW-03
0
9
DMW-04
0
14
FPA-02B
0
385
FPA-02C
1080
926
FPA-03B
69
318
FPA-03C
864
1103
FPA-04B
0
278
FPA-04C
219
871
FPA-09B
87
500
FPA-09C
1370
1331
MW-05B
0
0
MW-05C
0
0
MW-05CD
1130
0
MW-05D
2520
0
Page 2 of 4

TABLE 5-9A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
r
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
MW-05RE
2410
0
MW-07C
132
1
MW-08
0
0
MW-08B
0
0
MW-08D
3090
0
MW-08E
4480
0
MW-12R
260
93
MW-15RB
129
229
MW-15RC
825
642
MW-16
59
63
MW-16D
679
115
M W-20
68
373
MW-20D
96
1143
MW-21C
396
446
MW-22C
674
955
MW-23B
0
114
MW-23C
66
898
MW-23D
832
0
M W-23E
2460
0
MW-24RB
0
61
M W-24RC
92
277
MW-27B
0
31
MW-27C
142
84
M W-28C
0
46
M W-31 RC
54
20
MW-33C
0
9
MW-36B
0
55
MW-36C
170
127
MW-37B
0
0
MW-37C
0
0
MW-37CD
0
0
MW-37D
116
0
MW-37E
1470
0
MW-38C
167
53
MW-39C
0
58
M W-40C
261
172
MW-41B
0
0
MW-41C
0
0
MW-41D
2470
0
MW-41E
4410
0
MW-42B CCR
0
27
MW-42C CCR
269
207
Page 3 of 4

TABLE 5-9A
COMPARISON OF OBSERVED AND SIMULATED BORON
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
r
Well
Observed Boron
(Ng/L)
Computed Boron
(Ng/L)
MW-42D CCR
517
0
M W-43B
66
45
MW-43C
282
52
MW-44B
154
150
M W-44C
1380
364
MW-45B
69
39
MW-45C
1380
321
M W-46B
0
378
MW-46C
1040
833
MW-50B
63
55
MW-50C
213
117
MW-IAP-01D
517
0
SMW-01B
109
26
SMW-01C
708
141
SMW-02C
132
51
SMW-03C
140
16
SMW-04C
0
0
SMW-05B
0
4
SMW-05C
117
18
SMW-06B
0
8
SMW-06C
85
28
SMW-06D
1100
0
Prepared by: WTP Checked by: RAG
Notes:
Data collected December 2019
0 = monitoring wells within the Peedee with naturally occuring boron; not included in the calibration
Page 4 of 4

TABLE 5-9B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
ABM W-02D
0
0
ABMW-02S
0
0
AW-03C
0
0
AW-04C
0
0
AW-05C
0
0
AW-06RD
0
0
AW-07RD
0
0
AW-08C
0
0
AW-09C
0
0
BMW-01
0
0
BMW-02
25
0
BMW-03
0
0
BMW-04
18
0
CCR-109B
0
0
CCR-109C
0
0
CCR-109D
0
0
CCR-110B IMP
0
0
CCR-110C IMP
0
0
CCR-110D
0
0
CCR-111B
0
0
CCR-111C
0
0
CCR-111 D
0
0
CCR-112B IMP
0
0
CCR-112C IMP
0
0
CCR-112D
0
0
CCR-113 B
0
3
CCR-113C
0
8
CCR-113 D
0
0
CCR-114B IMP
0
31
CCR-114C IMP
23
46
CCR-114D
0
0
CCR-115B IMP
0
28
CCR-115C IMP
35
17
CCR-115 D
0
0
CCR-116B
5
3
CCR-116C
8
1
CCR-117B
5
1
CCR-117C
3
0
CCR-118B
38
0
CCR-118C
0
0
Page 1 of 4

TABLE 5-9B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
CCR-119B
4
0
CCR-119C
0
0
CCR-120B
2
0
CCR-120C
0
0
CCR-121B
1
0
CCR-121C
6
0
CCR-122B
0
0
CCR-122C
0
0
CCR-123B
0
0
CCR-123C
8
0
CCR-124B
7
0
CCR-124C
0
0
CCR-201C
0
0
CCR-201D
2
0
CCR-202C
0
0
CCR-202D
0
0
CCR-203C
0
0
CCR-203D
0
0
CCR-204C
0
0
CCR-204D
0
0
CCR-205C
0
0
CCR-205D
0
0
CCR-206C
0
0
CCR-206D
0
0
CCR-207C
4
0
CCR-207D
0
0
CCR-208C
0
0
CCR-208D
0
0
DMW-01
0
0
DMW-02
2
0
DMW-03
3
0
DMW-04
0
0
FPA-02B
1
0
FPA-02C
0
0
FPA-03B
0
0
FPA-03C
0
0
FPA-04B
1
0
FPA-04C
0
0
FPA-09B
0
0
FPA-09C
0
0
Page 2 of 4

TABLE 5-9B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
MW-05B
0
0
MW-05C
0
0
MW-05CD
0
0
MW-05D
0
0
MW-05RE
0
0
MW-07C
0
0
MW-08
0
0
MW-08B
0
0
MW-08D
0
0
MW-08E
0
0
MW-12R
0
0
MW-15RB
0
0
MW-15RC
0
0
MW-16
0
0
MW-16D
0
0
MW-20
3
0
MW-20D
0
0
MW-21C
0
0
MW-22C
4
0
MW-23B
0
0
MW-23C
2
0
M W-23D
0
0
MW-23E
0
0
MW-24RB
0
0
MW-24RC
0
0
MW-27B
3
1
MW-27C
7
1
MW-28C
0
0
MW-31RC
0
0
MW-33C
0
0
MW-36B
0
10
MW-36C
11
4
MW-37B
0
0
MW-37C
0
0
MW-37CD
0
0
M W-37D
0
0
MW-37E
0
0
MW-38C
11
0
MW-39C
0
2
MW-40C
38
12
Page 3 of 4

TABLE 5-9B
COMPARISON OF OBSERVED AND SIMULATED SELENIUM
CONCENTRATIONS (Ng/L) IN MONITORING WELLS
FOR POST -EXCAVATION TRANSPORT MODEL
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Selenium
(Ng/L)
Computed Selenium
(Ng/L)
MW-41B
0
0
MW-41C
0
0
MW-41D
0
0
MW-41E
0
0
MW-42B CCR
0
0
MW-42C CCR
2
0
MW-42D CCR
0
0
MW-43B
2
0
MW-43C
0
0
MW-44B
0
0
MW-44C
0
0
MW-45B
0
0
MW-45C
0
0
MW-46B
0
0
MW-46C
0
0
MW-50B
0
0
MW-50C
0
0
MW-IAP-01D
0
0
SMW-01B
0
0
SMW-01C
0
0
SMW-02C
0
0
SMW-03C
0
0
SMW-04C
0
0
SMW-05B
0
0
SMW-05C
0
0
SMW-06B
0
0
SMW-06C
0
0
SMW-06D
0
0
Notes:
Data collected through December 2019
Prepared by: WTP Checked by: RAG
Page 4 of 4

TABLE 5-10
PRE -EXCAVATION TRANSPORT MODEL SENSITIVITY
TO THE BORON Kd VALUES
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(pg/L)
Boron Model
(pg/L)
Boron, Low Kd
(pg/L)
Boron, High Kd
(pg/L)
NRMSE
18.29%
18.27%
18.34%
ABM W-02D
823
1830
1831
1820
ABMW-02S
159
200
200
200
AW-05B
0
4
4
3
AW-05C
0
173
181
156
AW-05D
355
0
0
0
AW-05E
2010
0
0
0
AW-06RB
0
15
15
14
AW-06RD
806
0
0
0
AW-06RE
2010
0
0
0
AW-07D
809
0
0
0
AW-07RD
779
0
0
0
AW-09C
328
0
0
0
AW-09D
668
0
0
0
BMW-01
0
7
7
6
BMW-02
0
38
38
38
BMW-03
0
31
31
29
BMW-04
0
134
135
134
CCR-102B
206
936
932
965
CCR-102C
2620
1374
1375
1376
CCR-103B
1240
1475
1472
1493
CCR-103C
2950
1645
1641
1665
CCR-103D
775
0
0
0
CCR-104B
1490
1496
1493
1513
CCR-104C
815
1752
1741
1799
CCR-104D
853
0
0
0
CCR-105C
1390
1756
1744
1809
CCR-105D
1050
0
0
0
CCR-106B
625
1444
1442
1459
CCR-106C
361
1764
1753
1810
CCR-106D
944
0
0
0
CCR-107B
354
1491
1490
1495
CCR-107C
573
1786
1776
1826
CCR-107D
1180
0
0
0
CCR-108B
371
998
997
1002
CCR-108C
245
1660
1651
1693
CCR-108D
836
0
0
0
CCR-109B
528
1389
1387
1404
CCR-109C
1190
1650
1640
1690
CCR-109D
1260
0
0
0
CCR-110B
3260
1261
1255
1288
CCR-110C
1760
1782
1779
1788
CCR-110D
834
0
0
0
CCR-111B
3210
1038
1036
1052
CCR-111C
2100
1780
1777
1784
CCR-111D
709
0
0
0
CCR-112B
2550
622
618
639
CCR-112C
1160
1323
1309
1380
CCR-112D
640
0
0
0
CCR-113B
337
712
705
745
CCR-113C
427
986
972
1045
CCR-113D
1030
0
0
0
CCR-114B
150
256
254
266
CCR-114C
180
528
519
564
CCR-114D
1020
0
0
0
Page 1 of 3

TABLE 5-10
PRE -EXCAVATION TRANSPORT MODEL SENSITIVITY
TO THE BORON Kd VALUES
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(pg/L)
Boron Model
(pg/L)
Boron, Low Kd
(pg/L)
Boron, High Kd
(pg/L)
NRMSE
18.29%
18.27%
18.34%
CCR-115B
0
224
221
234
CCR-115C
474
268
262
289
CCR-115D
671
0
0
0
CCR-116B
0
60
59
64
CCR-116C
352
158
153
173
CCR-117B
0
49
48
50
CCR-117C
252
247
241
272
CCR-118B
0
65
64
68
CCR-118C
293
328
319
364
CCR-119B
83
113
111
119
CCR-119C
871
423
412
473
CCR-120B
0
159
158
165
CCR-120C
810
625
612
684
CCR-121B
0
186
185
187
CCR-121C
142
579
572
622
CCR-122B
0
101
101
101
CCR-122C
2010
814
807
858
CCR-123B
0
208
208
209
CCR-123C
767
378
376
390
CCR-124B
0
305
303
310
CCR-124C
860
1276
1270
1304
CCR-201C
0
43
41
50
CCR-201D
418
0
0
0
CCR-202C
225
95
92
110
CCR-202D
566
0
0
0
CCR-203C
1310
186
182
205
CCR-203D
534
0
0
0
CCR-204C
180
96
96
98
CCR-204D
446
0
0
0
CCR-205C
1240
1051
1036
1121
CCR-205D
810
0
0
0
CCR-206C
231
580
567
633
CCR-206D
687
0
0
0
CCR-207C
214
253
247
277
CCR-207D
467
0
0
0
CCR-208C
0
88
85
96
CCR-208D
767
0
0
0
DMW-01
0
5
5
4
DMW-03
0
16
17
15
GWPZ-01A
0
43
42
45
GWPZ-01B
0
67
66
71
M W-04A
0
0
0
0
M W-05A
0
0
0
0
MW-05B
0
0
0
0
MW-05C
0
0
0
0
MW-05CD
1190
0
0
0
MW-05D
2640
0
0
0
M W-05RE
780
0
0
0
M W-07C
536
1
1
0
MW-08
0
0
0
0
M W-08E
4480
0
0
0
M W-11
1 0
1 35
33
40
M W-19
888
705
708
706
M W-21C
1 1110
1 649
650
659
Page 2 of 3

TABLE 5-10
PRE -EXCAVATION TRANSPORT MODEL SENSITIVITY
TO THE BORON Kd VALUES
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(pg/L)
Boron Model
(pg/L)
Boron, Low Kd
(pg/L)
Boron, High Kd
(pg/L)
NRMSE
18.29%
18.27%
18.34%
MW-22B
0
116
116
118
M W-22C
1970
922
922
939
MW-23B
0
125
125
129
M W-23C
365
544
540
574
MW-23D
902
0
0
0
MW-23E
2550
0
0
0
M W-24RB
0
77
77
79
M W-24RC
330
360
350
405
M W-27B
0
71
69
75
M W-27C
329
175
172
181
MW-28B
0
8
8
7
M W-28C
0
75
78
69
M W-31C
1500
180
176
190
M W-31 RC
1340
138
134
152
M W-32C
54
22
23
17
MW-33C
0
14
16
8
MW-36B
0
105
103
113
M W-36C
393
259
255
272
MW-37B
0
0
0
0
MW-37C
0
0
0
0
MW-37CD
60
0
0
0
MW-37D
140
0
0
0
M W-37E
1460
0
0
0
MW-38B
0
22
22
22
MW-38C
290
120
119
121
MW-38D
1560
0
0
0
MW-39B
0
7
7
7
M W-39C
0
105
104
108
MW-39D
1080
0
0
0
MW-40B
0
78
77
83
MW-40C
479
357
352
377
MW-40D
1220
0
0
0
M W-41 E
4320
0
0
0
PZ-06D
769
0
0
0
PZ-10D
483
0
0
0
SMW-01B
318
31
32
30
SMW-01C
780
276
278
269
SMW-03C
306
69
72
64
SMW-04C
0
0
0
0
SMW-06B
70
26
26
25
SMW-06C
298
186
187
180
SMW-06D
1120
0
0
0
Notes:
Boron concentrations are shown for the calibrated model, and for models where the Kd is increased by
a factor of 5 and decreased by a factor of 1/5.
Kd - soil -water distribution coefficients
O = monitoring wells within the Peedee with naturally occuring boron; not included in the calibration
Prepared by: WTP Checked by: RAG
Page 3 of 3

TABLE 5-11
POST -EXCAVATION TRANSPORT MODEL SENSITIVITY
TO THE BORON Kd VALUES
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Boron Model
(Ng/L)
Boron, Low Kd
(Ng/L)
Boron, High Kd
(Ng/L)
NRMSE
12.85%
12.53%
12.89%
ABMW-02D
739
1697
1666
1757
ABMW-02S
123
193
192
194
AW-03C
121
14
13
16
AW-04C
581
285
283
293
AW-05C
0
133
131
137
AW-06RD
821
0
0
0
AW-07RD
763
0
0
0
AW-08C
0
26
26
26
AW-09C
222
0
0
0
BMW-01
0
7
7
7
BMW-02
103
32
32
34
BMW-03
0
17
16
18
BMW-04
243
88
86
94
CCR-109B
818
948
1014
1027
CCR-109C
1940
1552
1542
1608
CCR-109D
1360
0
0
0
CCR-110BIMP
3120
1081
1164
1139
CCR-110CIMP
1950
1729
1724
1751
CCR-110D
898
0
0
0
CCR-111B
3110
861
971
914
CCR-111C
1850
1731
1724
1752
CCR-111D
762
0
0
0
CCR-112BIMP
1050
742
785
770
CCR-112CIMP
821
1221
1206
1295
CCR-112D
725
0
0
0
CCR-113B
364
632
677
675
CCR-113C
264
755
746
819
CCR-113D
1040
0
0
0
CCR-114BIMP
84
141
139
160
CCR-114CIMP
77
261
252
307
CCR-114D
1180
0
0
0
CCR-115BIMP
0
119
117
136
CCR-115CIMP
280
122
117
146
CCR-115D
821
0
0
0
CCR-116B
70
46
45
52
CCR-116C
252
75
72
88
CCR-117B
0
48
48
52
CCR-117C
161
122
117
144
CCR-118B
0
60
60
66
CCR-118C
55
177
172
209
CCR-119B
66
96
97
104
CCR-119C
248
339
337
373
CCR-120B
0
119
126
129
CCR-120C
1000
668
678
698
CCR-121B
0
146
144
153
CCR-121C
191
574
569
611
CCR-122B
0
87
86
91
CCR-122C
1070
700
693
739
CCR-123B
0
153
151
164
CCR-123C
56
336
332
352
CCR-124B
0
340
352
356
Page 1 of 3

TABLE 5-11
POST -EXCAVATION TRANSPORT MODEL SENSITIVITY
TO THE BORON Kd VALUES
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Boron Model
(Ng/L)
Boron, Low Kd
(Ng/L)
Boron, High Kd
(Ng/L)
NRMSE
12.85%
12.53%
12.89%
CCR-124C
202
907
916
950
CCR-201C
0
24
23
29
CCR-201D
369
0
0
0
CCR-202C
108
15
14
16
CCR-202D
668
0
0
0
CCR-203C
391
18
17
20
CCR-203D
606
0
0
0
CCR-204C
224
70
68
75
CCR-204D
490
1
1
1
CCR-205C
688
778
768
832
CCR-205D
828
0
0
0
CCR-206C
327
395
383
446
CCR-206D
740
0
0
0
CCR-207C
112
160
155
180
CCR-207D
602
0
0
0
CCR-208C
0
48
47
55
CCR-208D
883
0
0
0
DMW-01
0
7
7
6
DMW-02
0
17
17
18
DMW-03
0
9
9
10
DMW-04
0
14
14
14
FPA-02B
0
385
381
404
FPA-02C
1080
926
951
807
FPA-03B
69
318
283
366
FPA-03C
864
1103
1085
1146
FPA-04B
0
278
275
288
FPA-04C
219
871
867
881
FPA-09B
87
500
465
538
FPA-09C
1370
1331
1325
1366
MW-05B
0
0
0
0
MW-05C
0
0
0
0
M W-05CD
1130
0
0
0
M W-05D
2520
0
0
0
M W-05RE
2410
0
0
0
MW-07C
132
1
1
0
MW-08
0
0
0
0
MW-08B
0
0
0
0
M W-08D
3090
0
0
0
M W-08E
4480
0
0
0
M W-12R
260
93
91
103
M W-15RB
129
229
229
225
M W-15RC
825
642
639
638
M W-16
59
63
63
63
MW-16D
679
115
112
124
M W-20
68
373
374
369
MW-20D
96
1143
1143
1138
M W-21C
396
446
439
474
M W-22C
674
955
947
990
M W-23B
0
114
113
118
M W-23C
66
898
891
928
MW-23D
832
0
0
0
Page 2 of 3

TABLE 5-11
POST -EXCAVATION TRANSPORT MODEL SENSITIVITY
TO THE BORON Kd VALUES
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Well
Observed Boron
(Ng/L)
Boron Model
(Ng/L)
Boron, Low Kd
(Ng/L)
Boron, High Kd
(Ng/L)
NRMSE
12.85%
12.53%
12.89%
MW-23E
2460
0
0
0
MW-24RB
0
61
59
65
M W-24RC
92
277
270
314
MW-27B
0
31
30
36
MW-27C
142
84
82
92
MW-28C
0
46
46
43
MW-31RC
54
20
19
22
MW-33C
0
9
10
6
MW-36B
0
55
53
65
M W-36C
170
127
124
143
MW-37B
0
0
0
0
MW-37C
0
0
0
0
MW-37CD
0
0
0
0
MW-37D
116
0
0
0
MW-37E
1470
0
0
0
MW-38C
167
53
52
55
MW-39C
0
58
56
65
MW-40C
261
172
167
195
MW-41B
0
0
0
0
MW-41C
0
0
0
0
MW-41D
2470
0
0
0
MW-41E
4410
0
0
0
MW-42B CCR
0
27
27
27
MW-42C CCR
269
207
205
213
MW-42D CCR
517
0
0
0
MW-43B
66
45
42
56
M W-43C
282
52
51
58
M W-44B
154
150
149
156
M W-44C
1380
364
367
353
MW-45B
69
39
39
40
MW-45C
1380
321
319
325
MW-46B
0
378
380
371
M W-46C
1040
833
836
811
MW-50B
63
55
55
53
MW-50C
213
117
118
107
MW-IAP-01D
517
0
0
0
SMW-01B
109
26
25
26
SMW-01C
708
141
137
151
SMW-02C
132
51
50
55
SMW-03C
140
16
16
18
SMW-04C
0
0
0
0
SMW-05B
0
4
4
4
SMW-05C
117
18
17
20
SMW-06B
0
8
8
9
SMW-06C
85
28
28
30
SMW-06D
1100
0
0
0
Prepared by: WTP Checked by: RAG
Notes:
Boron concentrations are shown for the calibrated model, and for models where the Kd is increased by a factor of 5 and decreased by a
factor of 1/5.
Kd - soil -water distribution coefficients
O = monitoring wells within the Peedee with naturally occuring boron; not included in the calibration
Page 3 of 3

TABLE 6-1
CONVERSION OF SPLP CONCENTRATIONS TO EQUIVALENT PORE
WATER CONCENTRATIONS AS A FUNCTION OF THE Kd VALUE
UPDATED GROUNDWATER FLOW AND TRANSPORT MODELING REPORT
L.V. SUTTON ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, WILMINGTON, NC
Kd
(mKd
CSPLP Conversion Factor to CW
0
106.7
0.1
69.6
0.2
52.1
0.5
29.8
1
17.7
2
10.1
5
4.82
10
2.94
20
1.98
50
1.39
100
1.20
500
1.04
Notes:
mL/g - milliliters per gram
Kd - soil -water distribution coefficients
Prepared by: RF Checked by: RAG
Page 1 of 1