3620_DukeAllen_SSLF_Companion GW Doc_PTC Mod 1_FID1810615_20230711

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July 11, 2023
North Carolina Department of Environmental Quality (NCDEQ)
Division of Waste Management (DWM)
Solid Waste Section (the Section)
1646 Mail Service Center
Raleigh, North Carolina 28778
Attn: Ms. Sarah Moutos
526 S. Church Street
EC 12J
Charlotte, NC 28202
Re: Groundwater Information South Starter Landfill (SSLF) — Companion Submittal to Permit to
Construct Modification Request 1
Reference: Permit No. 3620-INDUS
Allen Steam Station
Gaston County
Dear Ms. Moutos,
The enclosed technical memorandum presents results from modeling to evaluate the effectiveness of a
proposed construction drain beneath the future South Starter Landfill (SSLF) and an active dewatering
system (existing pilot section and future full-scale phase), at the Allen Steam Station located in Gaston
County, near Belmont, North Carolina. The evaluation looked at how effective these two dewatering
methods were at lowering groundwater elevations beneath the future SSLF footprint to expedite the
time to reach the required vertical separation between the groundwater table and landfill liner system
per the applicable North Carolina General Statutes, Administrative Code, and U.S. Environmental
Protection Agency (USEPA) coal combustion residuals (CCR) Rule.
This technical memorandum has been prepared by SynTerra Corporation for Duke Energy Carolinas, LLC
(Duke Energy) and is being submitted as a companion document to support the Section's review of the
previously submitted SSLF Permit to Construct (PTC) Modification 1 (submitted to Mr. Jordan Russ under
separate cover on May S, 2023).
Design details for the construction drain system were included in the previously submitted SSLF PTC
Modification 1 companion document. Upon completion of the construction drain installation, the
previously approved Environmental Controls Monitoring Plan (ECMP) will be revised to include
semiannual sampling from the drain discharge.
A request for approval and details regarding the proposed full-scale SSLF area dewatering system were
provided to the Section over various email and telephone correspondences ranging from May 31, 2023
through June 20, 2023, with the Section granting approval for installation of the dewatering system
expansion on June 20, 2023.
Page 1 of 2

Please contact me at Courtney. [e-mail] [phone] if you have questions or
need additional information.
Respectfully submitted,
i
Courtney W. Murphy, P.G.
Environmental Services
Enclosure (1): Technical Memorandum — Groundwater Modeling to Support Vertical Separation — South
Starter Landfill 3620-INDUS (SynTerra, July 2023)
Cc: Jordan Russ — NCDEQ
Claire Osborn — NCDEQ
Ed Sullivan — Duke Energy
Tyler Hardin — Duke Energy
Kim Witt — Duke Energy
Kyle Baucom — Duke Energy
Henry Duperier — Duke Energy
Page 2 of 2

LIP
SynTerra
Date: July 11, 2023
Science & Engineering Consultants
148 River St., Suite 220, Greenville, SC 29601 1864.421.9999
To: Courtney Murphy (Duke Energy)
Cc: Scott Kalau (Duke Energy)
From: Johnathan Ebenhack, L.G., Senior Project S ient
Eric Hicks, Senior Project Scienti
IkA
Chris Suttell, Project Manager - /
Kathy Webb, Senior Peer Review
TECHNICAL MEMORANDUM
File: 0082.51.13.03
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Subject: Groundwater Modeling to Support Vertical Separation - South Starter Landfill 3620-INDUS
INTRODUCTION
This technical memorandum presents results from modeling to evaluate the effectiveness of a
proposed construction drain beneath the future South Starter Landfill (SSLF) and dewatering
wells west, north, and northeast of the future SSLF, at the Allen Steam Station (Allen or Site)
(Figure 1). At the request of Duke Energy Carolinas, LLC (Duke Energy), SynTerra Corporation
(SynTerra) conducted groundwater flow modeling to evaluate the effectiveness of these two
dewatering methods. The evaluation looked at how effective the dewatering methods were at
lowering groundwater elevations beneath the future SSLF to expedite the time to reach the
required vertical separation between the groundwater table and landfill liner system per the
applicable North Carolina General Statutes, Administrative Code, and U.S. Environmental
Protection Agency (USEPA) coal combustion residuals (CCR) Rule. Required vertical separation
per the applicable North Carolina General Statues is 4 feet of separation between groundwater
table and the one -foot -thick compacted soil liner (CSL). The composite landfill liner is placed
above the CSL, which is equivalent to the USEPA CCR Rule requirement of 5 feet of separation
from the landfill liner.
A dewatering well pilot study was conducted prior to installation of all planned dewatering
wells in and around the SSLF. This pilot study consisted of 11 dewatering wells installed to the
target depths of approximately 70 feet below ground surface at approximately 30-foot
intervals. Those 11 wells were installed in the northern portion of the SSLF footprint and have
been operating since January 18, 2023.
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Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
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SUMMARY
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Based on Duke Energy's input, the model assumes that the SSLF dewatering well system
becomes operational in stages and becomes fully operational by August 31, 2023, and the SSLF
construction drain becomes operational by Mach 15, 2024 at which time the dewatering wells
are shutdown. With these assumptions the model predicts that the necessary separation of 4
feet between the water table and the CSL would be reached by approximately December 2023.
Based on model simulations, flow to the construction drain starts approximately 3 months after
the dewatering wells cease operating as the water table slowly rebounds. The model predicts
that the construction drain maintains the required separation after the dewatering wells are
shut off and groundwater elevations rebound. The model predicts that the construction drain
continues to maintain the required separation until the drain goes dry. The maximum flow rate
to the construction drain is predicted to be approximately 8 gallons per minute (gpm) and
occurs approximately 16 months after the dewatering wells cease pumping. The model
indicates the flow rate is relatively steady until 2026 when it gradually decreases with flow
ceasing by 2029. Flow is anticipated to decrease as the effects of ash basin closure activities
such as excavation and dewatering in the Active Ash Basin (AAB) influences the SSLF area. The
operational life of the construction drain is predicted to be approximately 5.3 years.
The total flow rate to the 11 dewatering wells installed for the pilot study is predicted to range
from 21 to 85 gpm initially, which is consistent with measured flow rates from the dewatering
system being operated by Griffin Dewatering. The flow rate from the 11 initial dewatering wells
is predicted to decrease to approximately 16 gpm before an additional 15 planned wells outside
of the footprint of the SSLF become operational at the end of July 2023. The flow rate from the
system of 26 wells (11 dewatering wells and 15 additional wells outside the SSLF footprint) is
predicted to be approximately 78 gpm, 24 hours after the additional 15 planned wells become
operational. The flow rate from these 26 dewatering wells is predicted to decline to 54 gpm
before the remaining 26 planned dewatering wells become operational by the end of August
2023. After these last dewatering wells become operational, the flow rate from the entire
dewatering system is predicted to be approximately 248 gpm after 24 hours of operation. After
a month the flow rate is predicted to be 143 gpm. The flow rate steadily decreases with time
and is predicted to be approximately 86 gpm when the entire dewatering system is shutdown
on March 15, 2024.
Actual flow rates to the construction drain and dewatering wells may vary from model
predictions because of actual conditions encountered in the field, uncertainty in drain
installation methods, model assumptions and simplifications, and model uncertainty.
METHODS
To evaluate the performance of the construction drain and dewatering wells at the future SSLF
as well as the operational life of the construction drain, several flow models were developed.
These include a historical steady-state pre -decanting model, a calibration model, a predictive
comparison model with no dewatering measures, and a predictive model with dewatering
measures. The historical steady-state pre -decanting model was used to estimate the initial
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hydraulic heads for the calibration model. The calibration model was used to calibrate the
hydraulic parameters for the models by adjusting aquifer properties until simulated hydraulic
heads matched observations from 2019 to 2022. The calibration model also provides the initial
hydraulic heads for the two predictive models. The first predictive model serves as a baseline
comparison model and does not include the dewatering measures (dewatering wells or the
proposed construction drain). The predictive model without SSLF dewatering measures was
used to predict how future hydraulic heads would vary in and around the SSLF if no dewatering
measures were implemented. The results from the predictive model without SSLF dewatering
measures were compared to the results from the predictive model with SSLF dewatering
measures to determine how effective those dewatering measures were at reducing hydraulic
heads in and around the SSLF. The final model was the predictive model with SSLF dewatering
measures and included both the dewatering wells and the proposed construction drain. The
models are summarized below.
Model Name
Model
Simulation
Description and Purpose
Number
Date(s)
Historical pre -decanting
Steady-state model representing the relatively stable
model
1
2019
water levels in early 2019. Provides initial starting heads
for the calibration model.
Transient model incorporating site activities between
2019 and 2022 (Table 1) and calibrated to observed
Calibration model
2
2019-2022
2019 through 2022 water levels. Used to refine aquifer
properties and boundary conditions. Provides starting
heads to the models with and without landfill
dewatering measures.
Predictive, transient model based on anticipated Site
activities (Table 2) excluding the future SSLF dewatering
Model without SSLF
measures (dewatering wells and the construction drain).
dewatering measures
3
2022- 2032
Used as a baseline for comparison to the landfill
dewatering model (dewatering wells and a construction
drain).
Predictive, transient model based on anticipated Site
activities (Table 2) including the future SSLF dewatering
Model with SSLF
measures (dewatering wells and a construction drain).
dewatering measures
4
2022- 2032
Used to evaluate the time to reach vertical separation
with landfill dewatering, flow rates, and operational life
of the construction drain.
The first flow model (Model 1), referred to as the historical pre -decanting model, represents
relatively stable water -level conditions in early 2019, prior to the cessation of sluicing in the
Active Ash Basin (AAB) and the onset of active decanting of ponded water within the AAB. The
historical pre -decanting model was used to define the initial starting heads for the calibration
model. The second model (Model 2), referred to as the calibration model, represents the time
from 2019 until December 2022. The calibration model is a transient model that was calibrated
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to observed transient water -level trends of selected wells and piezometers within and around
the future SSLF as well as other important locations at the Site. The calibration model included
known changes to hydraulic features in and around the SSLF and active decanting of the AAB
polishing pond. The calibration model (Model 2) was primarily used to improve the estimated
hydraulic property distribution for the predictive models and to define the initial starting heads
for the predictive models. Finally, there are two predictive transient models (Models 3 and 4)
used to evaluate the performance of the dewatering activities for the SSLF and operational life
of the construction drain. They include Model 3, a baseline simulation without the construction
drain or dewatering wells for comparison, and Model 4, that includes the SSLF dewatering
measures to evaluate the effectiveness of dewatering and the operational life of the proposed
construction drain.
MODEL CONSTRUCTION AND CONDITIONS
The models used for this evaluation were based on the previous models developed to evaluate
the performance of the construction drain system for the North Starter Landfill (NSLF) currently
under construction north of the SSLF at the Site. That modeling effort is described in detail in
the Groundwater Modeling to Support Vertical Separation — North Starter Landfill 3619-INDUS
technical memorandum (SynTerra, 2022). The NSLF models were taken and modified as needed
to create the four models for this evaluation and included all previous calibrated hydraulic
parameter field modifications up to that point. The numerical model grid developed for the
NSLF modeling effort was modified by decreasing grid resolution near the NSLF and increasing
grid resolution in and around the SSLF. The grid resolution was decreased near the NSLF to
decrease model run times; this change did not affect predictions in and around the SSLF. The
grid spacing in the future SSLF area was refined from approximately 65 feet by 50 feet to
approximately 20 feet by 20 feet to increase resolution around the proposed construction drain
laterals and dewatering wells. The vertical grid refinements made during the NSLF modeling
effort were sufficient for this modeling effort and no additional modifications were made. The
vertical grid thickness is generally 3 to 6 feet in the upper layers of the model which correspond
with the depths at which the proposed construction drain and proposed dewatering wells
would be installed.
Certain features in the NSLF area were removed from the SSLF models to reduce model run
times and enhance numerical stability. Removal of these features did not influence
groundwater elevation predictions in and around the SSLF because of the distance between
those features and the area in and around the SSLF.
Historical Pre -Decanting Model (2019) (Model 1)
The historical pre -decanting model was developed to determine the initial heads for the
transient calibration model (Model 2). The historical pre -decanting model represents conditions
prior to cessation of sluicing in the AAB and the onset of active decanting operations. These
conditions are the same as the pre -decanting flow model presented in Appendix G of the 2019
Corrective Action Plan Update (SynTerra, 2019). The pre -decanting model in this report includes
the grid refinements detailed above and improvements to the hydraulic parameter fields that
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have been made during subsequent calibration efforts since the development of the 2019 pre -
decanting model.
Calibration Model (2019 to 2022) (Model 2)
The calibration model is based on the NSLF calibration model (SynTerra, 2022) and updated to
include additional details in and around the SSLF such as recent changes to Site conditions (e.g.,
drainage channel location and elevation, polishing pond elevations, etc.) and additional
groundwater monitoring locations and groundwater level measurements for calibration. The
calibration model uses the refined grid developed for the historical pre -decanting model and
incorporates conditions that occurred at the Site from approximately February 2019 to
September 2022.
Conditions incorporated into the calibration model were based on known Site history during
this time, input from Duke Energy personnel, and the review of aerial survey data from July
2021 to August 2022 provided by Duke Energy's Propeller website (Duke Energy, 2022a). Site
changes and the dates they occur are summarized in Table 1. Features local to the future SSLF
are shown on Figure 2. The primary hydraulic features modified or added between the NSLF
calibration model and SSLF calibration model include:
• The NSLF sumps and wetland were removed.
• The Groundwater Corrective Action Plan (CAP) remediation pilot pumping system
located east of the NSLF was removed.
• The ditch system within the AAB was modified to reflect the removal of the central ditch
on February 2022 and the addition of a ditch located along the southern edge of the
AAB.
• The footprint and the stage (water -level elevation) of the AAB polishing pond were
allowed to vary with time based on detailed survey data and field observations.
Drainage features in the model were simulated using the Drain package in MODFLOW.
Bottom elevations for drain features were based on previous values from the NSLF calibration
model or more up-to-date ground surface elevations based on data from Duke Energy's
Propeller website. During the modeled calibration period the conveyance ditch system within
the AAB was modified by removing the portion of the conveyance ditch that traversed the
central portion of the AAB and replacing it with a ditch that ran along the southern border of
the AAB (Figure 2). Ground surface elevations in the ditch system located along the southern
edge of the AAB were allowed to vary with time from February 2022 to September 2022 based
on elevations from the Propeller website.
Linear drain feature conductance terms are assumed to be 100 feet squared per day per foot
(feet2/day)/(foot) and areal drain feature conductance terms are assumed to be 100 feet
squared per day per feet squared (feet2/day)/(feet2). Ponded water features not simulated as
drains are simulated using the General Head Boundary package in MODFLOW with head -stages
set to elevations from survey data and data provided by Duke Energy. Specifically, the stage for
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the General Head Boundary representing the AAB polishing pond was modified to incorporate
measured water levels in the AAB polishing pond, which were provided to SynTerra by Duke
Energy in Excel spreadsheet format (Duke, 2022b) and Propeller data. The recharge distribution
is based on the land use and surface water body locations (Figure 3).
The calibration model includes improvements to the hydraulic parameter fields that have been
made during previous calibration efforts since the development of the models presented in the
2019 Corrective Action Plan Update (SynTerra, 2019). The initial heads used in the calibration
model are from the historical pre -decanting model.
Model Calibration
Calibration for this modeling effort was based on the previous model calibration conducted for
the NSLF construction drain modeling effort (SynTerra, 2022). Because full-scale calibration had
been recently completed, calibration for this modeling effort was constrained to a smaller
region around the SSLF. Transient water -level data, spanning from 2019 until September 2022,
for 60 monitoring wells and piezometers were used as calibration targets (Figure 4). The
calibration targets included monitoring wells and piezometers in and around the future SSLF
where changing Site conditions may influence groundwater levels. During calibration, particular
attention was paid to wells and piezometers in and around the future SSLF including
piezometers within the footprint of the future SSLF that were installed in May 2022. The new
piezometers include SSLF-PZ-1, SSLF-PZ-2, SSLF-PZ-3, and SSLF-PZ-4; the boring logs for those
piezometers are included in Appendix A. Transient model calibration was performed to match
simulated groundwater elevations and trends with observed groundwater elevations and
trends in selected monitoring wells and piezometers.
Calibration was performed by manually adjusting the hydraulic parameters, primarily hydraulic
conductivity, until the model was able to match the observed groundwater elevations and
trends to an acceptable level.
Predictive Models (2022 to 2032) (Model 3 and Model 4)
The purpose of the transient predictive models is to estimate the time to achieve a 4-foot
vertical separation from the future SSLF CSL subgrade to the groundwater table, the
operational life of the construction drain, and expected flow rates from the construction drain
and dewatering wells. The predictive models, both Model 3 and Model 4, use the same model
setup as the transient calibration model but incorporate the changes anticipated to occur at the
Site after December 2022. The predictive models extend approximately 9 years beyond
December 2022 to evaluate long-term effects of ash basin closure and landfill construction on
the construction drain operation and performance.
Construction activities at the Site expected to influence groundwater elevations after December
2022 are summarized in Table 2. The approach to dewatering in the AAB footprint was
provided in an email dated January 20, 2023 (Duke, 2023). The remaining activities are based
on the closure schedule dated May 8, 2023 provided by Charah Solutions Inc. (Charah, 2023).
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Hydraulic features in the predictive model in and around the future SSLF are shown on Figure 5.
Primary hydraulic features added or modified in the model are discussed below.
Drain boundaries and General Head Boundaries in MODFLOW are used to simulate engineered
hydraulic features such as ditches and ponds as well as natural hydraulic features such as
wetlands, streams, and the Catawba River/Lake Wylie. Conductance terms for these features
are assumed to be 100 (feet2/day)/(foot) for linear features and 100 feet squared per day per
feet squared (feet2/day)/(feet2) for areal features, unless otherwise noted. Model configuration
for the channels that convey water to the AAB polishing pond remains the same as the final
configuration in the calibration model with the central conveyance ditch removed and the
southern conveyance ditch installed (Figure 5). The head stage of the AAB polishing pond has
been set to the operating goal of 615 feet and remains at this level until the proposed
excavation and dewatering in the AAB footprint is expected to bring groundwater elevations in
the AAB to this level and the AAB polishing pond becomes inactive (Table 2). The model
assumes that the current layout of drainage ditches and other hydraulic features in the AAB do
not change throughout the model simulation period and the drainage features become inactive
as excavation and dewatering in the AAB progress.
The excavation and dewatering activities in the AAB are simulated as a drain boundary
(Figure 5) with bottom elevations set to the excavation grades specified in an email from Duke
(Duke, 2023). In the models, the AAB dewatering is assumed to occur as a step function as
tabulated in Table 2. To be conservative, the dewatering elevations are assumed to be the
same as the proposed excavation grades, even though water levels would be maintained with
rim ditches constructed 5 feet below the excavation grades. Another conservative assumption
is that the dewatering level for a specific excavation period would be achieved at the end of the
period, even though dewatering would result in decreasing water levels throughout the entire
period. Because of numerical instability in the model, the drain boundary representing
excavation and dewatering of the AAB does not cover the entire footprint of the proposed
activities, but only the predicted maximum horizontal extent of ash within the AAB at the end
of the modeled period. The predicted excavation elevation in the AAB at the end of the
modeled period is 600 feet, therefore the 600-foot bottom of the ash contour within the AAB
was used in the model to define the drain boundary. Since time -dependent hydraulic
conductivity fields are difficult to implement in the Groundwater Modeling System (GMS)
software, the simulation does not simulate the removal of ash from within the AAB and only
simulates the dewatering component. Assuming a smaller footprint to represent the area of
excavation and dewatering in the AAB and not removing material from within the AAB are both
conservative assumptions in the model.
The water supply wells and septic returns (Figure 5) continue to operate at the flow rates
specified in the calibration model.
Recharge is affected by construction activities at the Site, which could impede precipitation
from reaching the water table. Construction activities include the installation of liners in the
future SSLF. Some of those activities occur during the time frame of the models and are
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incorporated as transient recharge boundaries. Recharge zones and changes during the model
simulation in the SSLF area are shown on Figure 6.
The predictive models use the storage coefficients determined during model calibration. The
calibrated specific storage value for ash, saprolite, and transition zone material is 0.0002 per
foot, and the specific yield value is 0.1. The calibrated specific storage value for fractured
bedrock and bedrock is 0.000004 per foot, and the specific yield is 0.004. In general, the specific
yield in saprolite and ash will have the largest effect on the performance and operational life of
the construction drain compared to other storage coefficients (i.e., bedrock specific yield,
specific storage coefficients). The higher the specific yield, the longer it will take the system to
equilibrate to dewatering. To account for variation in the storage coefficients, a sensitivity
analysis was performed on specific yield and is presented in the Results section.
For starting heads, the predictive model uses the December 1, 2022, hydraulic heads from the
calibration model.
Model without SSLF Dewatering Measures (Model 3)
Model 3 simulates the construction of the future SSLF but excludes the SSLF dewatering
activities including the SSLF dewatering wells and proposed construction drain. This model
construction is identical to the model with SSLF dewatering measures (Model 4) with the
exception of these proposed dewatering activities are excluded. Model 3 serves as a baseline
for evaluating the performance of the construction drain with dewatering wells for controlling
groundwater elevations in the area of the future SSLF. Model 3 incorporates all the model
features and configurations discussed above.
Model with SSLF Dewatering Measures (Model 4)
Model 4 incorporates all the model features and configurations discussed above with the
addition of a construction drain and a series of dewatering wells located north of the future
SSLF. The construction drain is simulated with the MODFLOW Drain package based on AECOM's
proposed design (Figure 7) provided to SynTerra by Duke Energy. The bottom elevation of the
drain boundaries is set to the invert elevation of the 6-inch perforated HDPE drainpipe in the
stone bed. This is a conservative approach for simulating the drain because the underlying
stone bed, which is located below the drainpipe, may also serve as a conduit for groundwater
flow.
The bottom elevation of the proposed construction drain ranges from approximately 618.7 feet
on the southwestern edge to approximately 589.5 feet within the construction drain blanket
drain in the northeastern corner. To simulate the change in elevation along the drain feature,
the construction drain is simulated using a series of arc drain boundaries with bottom
elevations decreasing in a linear fashion from the inlet of the drain to the outlet (Figure 8). Each
lateral of the drain was placed in Model 4 across multiple model layers based on the bottom
elevation of the drain. The construction drain laterals in Model 4 assume a conductance of 1
(feet'/day)/(foot). The construction drain sump at the northeast corner of the construction
drain system is simulated with a polygon drain boundary with a conductance of 1 (feet'
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/day)/(feet2). The construction drain becomes active in Model 4 on March 15, 2024, and the
model does not account for any dewatering needed during the installation of the construction
drain.
To enhance dewatering in the SSLF area, a dewatering well system consisting of 52 wells along
the western, northern, and eastern edge of the SSLF was simulated in Model 4. The locations of
the wells in the model are shown on Figure 8. Existing dewatering wells installed for the
dewatering well pilot study are shown in red while proposed wells are shown in blue. The wells
are approximately 70 feet deep below ground surface with 40-foot screens. In Model 4, the
wells are simulated using the Multi -Node Well (MNW2) package that allows a water -level
elevation to be set; the model calculates the flow to maintain this water -level elevation in the
well. The pumping water -level elevations were set to 5 feet above the bottom of the well. In
Model 4, the dewatering study wells (11 already installed) became operational on January 18,
2023. At the time of the simulations 15 additional wells located outside the SSLF footprint are
expected to become operational on July 31, 2023. By August 31, 2023, the 26 additional wells
located inside the footprint of the SSLF are expected to become operational per Duke Energy
and Griffin's schedule. However, at the time of this report, the actual time they become
operational is uncertain and delays in operation of the dewatering wells may result in
predictions that underpredict the time to reach the NCDEQ-required 4 feet of separation
between the water table and the CSL. The dewatering wells cease pumping in Model 4 on
March 15, 2024, when the construction drain is assumed to become operational.
RESULTS
Historical Pre -Decanting Model (2019) (Model 1)
Results from Model 1 indicate that the current distribution of hydraulic parameters is still a
good fit to the observed pre -decanting long-term average of water levels in monitoring wells at
the Site. The root mean square error (RMSE) between the simulated and observed long-term
average water levels is 3.7 feet and the normalized RMSE (NRMSE), normalized to the range of
observed long-term average water levels, is 4.8 percent. The resulting head distribution is
similar to that originally predicted by the 2019 model. The predicted hydraulic heads in the
upper saprolite (model layer 12) for the historical pre -decanting model are shown on Figure 9.
Calibration Model (2019 to 2022) (Model 2)
Model calibration resulted in an RMSE of the entire transient calibration model of 4.6 feet and
an NRMSE of 6.2 percent, normalized to the range of all measured water levels used to
calculate the RMSE. In general, an NRMSE of 10 percent or less demonstrates a good fit to the
observed data. Figure 10 shows the residual between computed and observed heads in and
around the SSLF on September 1, 2022. The RMSE calculated using only the wells shown in
Figure 10 is 3.2 feet with an NRMSE of 4.7 percent, normalized to the range of groundwater
elevations measured in this subset of wells.
Hydrographs showing observed and modeled water levels with time in wells in and around the
SSLF (Figure 10) are shown on Figures 11A through 11F. Water levels in the SSLF area correlate
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somewhat with polishing pond elevations early on but not as strongly with precipitation data.
This is probably because the frequency of water level observations is too sparse to see the
response to rainfall or seasonal trends. Hydrographs for the remaining target wells and
piezometers used during the calibration are included in Appendix B.
The modeled groundwater elevations in the upper saprolite near the future SSLF on
December 1, 2022, are shown on Figure 12. These heads serve as the starting heads for the
predictive models.
Predictive Models (2022 to 2032) (Models 3 and 4)
Isopach plots showing the groundwater vertical separation between the future CSL subgrade
and the water table at selected times are shown on Figures 13A through 13N with the upper
panel showing results from the model without SSLF dewatering measures (Model 3) and the
lower panel showing results from the model with SSLF dewatering measures (Model 4). Cooler
colors indicate greater separation between the CSL and the modeled water table. Warmer
colors indicate less or no separation (i.e., the modeled groundwater elevation is at or above the
bottom of the CSL). Models 3 and 4 simulations predict that at the start of the modeled period,
January 1, 2023, only a portion of the southern and southeastern corner of the SSLF meets the
vertical separation criteria. Model 4 predicts that the head separation goal would be reached by
approximately December 1, 2023, as shown in the lower panel of Figure 13E. Delays in the
dewatering well operations from July 31 and August 31, 2023, to later in the year are expected
to delay the time to reach separation. If no dewatering methods are employed for the SSLF, as
simulated with Model 3, head separation is not achieved until approximately January 2029
(Figure 13L).
Model without SSLF Dewatering Measures (Model 3)
Results for Model 3 are shown in the upper panels of Figures 13A through 13N. This model
serves as a baseline for comparison to conditions with dewatering measures. Figures 13A
through 13N indicate that without dewatering measures the rate at which groundwater
elevations decrease in the footprint of the SSLF is generally slow and the vertical head
separation goal of 4 feet is not reached until approximately January 2029 (Figure 13L). The
reduction in groundwater elevations observed in Model 3 is the result of closure activities in the
AAB such as excavation and dewatering.
Model with SSLF Dewatering Measures (Model 4)
Results for Model 4 are shown in the lower panels of Figures 13A through 13N. These results
indicate that dewatering measures significantly increase the rate at which groundwater
elevations decrease in the SSLF. The model indicates that when the dewatering wells become
operational, first the dewatering study wells and then the proposed wells, they create a large
area of drawdown that results in separation in the SSLF footprint prior to operation of the
construction drain (Figures 13B through 13F). By December 1, 2023, separation is predicted to
have been met across the SSLF footprint (Figure 13E). The dewatering wells are assumed to
operate until March 15, 2024, when the construction drain becomes operational. The
depressed water table caused by the dewatering wells is predicted to result in the construction
synterracorp.com

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station Page 11 of 15
drain initially not receiving flow. However, as groundwater levels rebound after turning off the
dewatering wells the construction drain begins receiving flow around June 2024 (Figure 14).
Evidence of the construction drain affecting water levels visually is seen along some of the drain
laterals in Figure 13H. Flow rates from the construction drain decline with time, especially after
January 2028 when the effects of closure activities such as excavation and dewatering become
evident. Model 4 predicts the construction drain would be able to maintain the desired
separation between the groundwater elevations and the CSL subgrade (Figures 13G through
13N).
Model 4 was also used to estimate the operational life of the construction drain, the flow rate
to the construction drain, and the dewatering well flow rates. The time at which the
construction drain receives water is shown on Figure 14. The predicted flow rate overtime for
the construction drain (Base Model; Model 4) is shown on Figure 14 as a solid black line. Model
4 predicts that the drain would slowly start to receive water as water levels rebound and water
levels would remain relatively steady for several years before starting a more rapid decline in
2028 as the excavation levels deepen in the AAB and have greater influence on groundwater
levels. The total expected operational life of the construction drain is approximately 5.5 years.
Discharge from the construction drain is expected to stop around September 2029. Actual flow
rates to the construction drain may vary from model predictions because of uncertainty in drain
installation methods, model assumptions and simplifications, and model uncertainty.
The combined flow rate from the dewatering wells is shown on Figure 15 as the solid black line
(Base Model). The dewatering well system initially consists of 11 wells which started pumping
on January 18, 2023. An additional 15 wells located northeast of the SSLF, outside of the SSLF
footprint, are assumed to become operational by July 31, 2023. An additional 26 wells located
within the SSLF footprint in the western and northern areas of the SSLF are assumed to become
operational by August 31, 2023. The estimated initial combined flow rate from the initial 11
dewatering study wells was approximately 28 gpm which is predicted to decrease to
approximately 16 gpm before the second set of 15 wells become operational. The initial
estimated combined flow of these two sets of dewatering wells 24 hours after the proposed
wells start operating is 78 gpm (Figure 15). This flow rate is predicted to decrease to 54 gpm
before the last set of 26 dewatering wells become operational at the end of August 2023. The
initial combined flow after 24 hours of full system operation, when all wells are operating, is
estimated to be 248 gpm. These estimates of initial flow rates from when each portion of the
dewatering well system becomes operational are based on predictions after 24 hours of
operation. In reality the initial flow rates could be greater than those presented here but are
expected to decrease rapidly as shown in Figure 15. Flow rates to the dewatering wells may
vary from simulated flow rates because of conditions encountered in the field and model
assumptions and uncertainty.
Sensitivity Analyses
Sensitivity analyses were performed to evaluate uncertainty in the model predictions by varying
the parameters that are likely to influence the time to reach vertical separation, the operational
life of the construction drain, and construction drain and dewatering well flow rates. These
synterracorp.com

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station Page 12 of 15
parameters include background recharge, the conductance of the construction drain, the
specific yield of the shallow materials (ash, saprolite, and transition zone), and the depths of
the dewatering wells. The sensitivity analyses were conducted by comparing the model with
SSLF dewatering measures (Base Model) to models where the parameters discussed above
were varied around the base values. The base model and parameters varied are summarized in
Table 3.
Recharge was increased by 25% to evaluate the effect of increased recharge. This percent
increase in recharge is based on the estimated long term seasonal high recharge rate from the
Long -Term Seasonal High Groundwater Elevation Estimation Technical Memorandum
(SynTerra, 2020).
The conductance of the construction drain was chosen for the sensitivity analysis because it is
not easily estimated but affects how efficiently the construction drain removes groundwater
from the formation and reduces groundwater levels within the future SSLF. A lower drain
conductance of 0.1 (feet2/day)/(foot) for the drain laterals and 0.1 (feet2/day)/(feet2) for the
drain sump was used in one sensitivity analysis and a higher value of 10 (feet2/day)/(foot) for
the drain laterals and 10 (feet2/day)/(feet2) for the drain sump was used in another.
Specific yield was selected because it can also be highly variable and is one of the primary
factors controlling how much water must be removed from storage to decrease the water table
in and around the future SSLF and therefore how quickly dewatering activities would lower the
water table. The sensitivity analysis evaluated two additional specific yield values, a lower value
of 0.01 and an upper value of 0.2. Those values were chosen because they represent
reasonable estimates of the lower and upper limits for specific yields in the type of materials at
the Site.
The depth of the dewatering wells was selected because well depth affects the amount of
water that can be extracted. The depth was decreased by 10 feet or increased by 10 feet while
the pumping level in the well was kept at 5 feet above the bottom of the well.
Results from the sensitivity analyses, including the predicted times to achieve the vertical
separation goal, duration of the construction drain operational life, and flow rates from the
construction drain and dewatering wells are presented in Table 3. The flow rate over time for
each simulation assuming different sensitivity analysis parameters is shown on Figure 14 for the
construction drain, and the combined flow rates for the dewatering wells are shown on
Figure 15.
Increasing the background recharge to the long term seasonal high resulted in a slightly longer
time to reach separation and increased the operational life of the construction drain. This
greater recharge value also slightly increases the flow rates from the dewatering wells and
increases the flow to the construction drain. These effects are due to more water being
available to the flow system overall.
synterracorp.com

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station
Page 13 of 15
Reducing the conductance from 1 to 0.1 (feet2/day)/(foot) did not change the time to reach
separation because the water levels are controlled by the dewatering wells. A lower
conductance reduced the flow from the drain once it became operational because the drain is
less efficient in removing water because of increased resistance to flow. An increase in drain
conductance increased the drain efficiency resulting in more flow from the drain. Reducing or
increasing the construction drain conductance did not have a meaningful effect on the
operational life of the drain.
Decreasing specific yield to 0.01 results in a shorter time to achieve separation, a shorter
operational life of the drain and lower flow rates from the dewatering wells. At the beginning of
the operational life of the drain a greater flow rate is predicted with the decreased specific yield
but the predicted flowrate quickly falls below the Base Case prediction (Model 4). Currently the
cause of the initially high flowrate to the construction drain has not been fully evaluated.
Increasing the specific yield resulted in a longer time to achieve separation, a longer
operational life of the construction drain, greater flow rates to the construction drain after the
first few months, and greater flow rates to the dewatering wells.
Deepening the dewatering wells increased the flow rate from the dewatering wells but had
little effect on the time to reach head separation or the time the construction drain received
discharge. Deeper wells reduced the flow to the construction drain initially because the deeper
wells are more effective in dewatering the area. Shallower dewatering wells had smaller flow
rates, increased the time to reach separation slightly, but did not change operational life of the
drain. Shallower wells would likely result in an increased flow rate into the construction drain as
the shallow wells are not as efficient in lowering water levels in the SSLF area.
The Base Case and sensitivity models, excluding the long-term seasonal high recharge model,
assume a long-term average recharge rate that was estimated during development of the 2019
CAP models. However, temporal variations in recharge both at small scales (individual rainfall
events) and at larger scales (seasonal variation) are likely to result in increases and decreases in
water levels. However, available long-term data for the Site indicate that water elevations
around the ash basins at the Site are generally decreasing even though some short-term
increases are observed because of varying recharge rates. Currently, this overall decrease in
water levels is attributed to Site activities including the cessation of sluicing, active decanting,
and excavation and dewatering activities. These decreasing trends are expected to continue as
Site closure activities progress and the Site reverts to conditions more similar to those prior to
construction of the ash basins.
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Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station
ATTACHMENTS:
LIST OF FIGURES
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11A-F
Figure 12
Figure 13A-N
Figure 14
Figure 15
LIST OF TABLES
Page 14 of 15
USGS Location Map
Calibration Model Hydraulic Features Near the Future SSLF
Calibration Model Recharge Distribution
Calibration Model Monitoring Wells and Piezometers
Predictive Model Hydraulic Features Near the Future SSLF
Predictive Model Recharge Distribution
Future SSLF Construction Drain Design (AECOM, 2023)
Modeled Scenarios for the Future SSLF in the Predictive Model
Estimated Initial Groundwater Elevations for the Calibration Model
Calibration Model Residuals Near the Future SSLF
Computed vs Observed Hydraulic Heads in Calibration Monitoring Wells and
Piezometers Near the Future SSLF
Estimated Initial Groundwater Elevations for the Predictive Model
Simulated Vertical Separation Between the Groundwater Table and the SSLF
CSL Subgrade
Predicted Construction Drain Flow Rate
Predicted Total Flow Rate from the Dewatering Wells
Table 1 Site Activities (2019 to 2022) Incorporated into the Calibration Model
Table 2 Anticipated Site Activities (2022 to 2032) Incorporated into the Predictive
Models
Table 3 Summary of Modeled Time to Reach Head Separation Goal and Drain
Operational Times
LIST OF APPENDICES
Appendix A SSLF Piezometer Boring Logs
Appendix B Calibration Hydrographs
synterracorp.com

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station
REFERENCES
Page 15 of 15
AECOM. (2023). Permit to Construct Modification Request 1 Allen Steam Station, South Starter
Landfill (3620-INDUS), Gaston County, North Carolina, Rev 0, May 2023.
Charah. (2023). Allen Steam Station, Major Site Closure, All Activities Schedule, data date of
May 8, 2023, provided by Duke Energy Carolinas to SynTerra via email 5/10/2023.
Duke Energy. (2022a). Propeller Aerials and Topo. September 2022.
Duke Energy. (2022b). Allen Steam Station, Summary of Pond Levels provided by Duke Energy
Carolinas to SynTerra via email 9/9/2022.
Duke Energy. (2023). AAB Stage -Storage and AAB Excavation of Time provided to SynTerra via
email 1/2/2023.
SynTerra. (2019). Updated Groundwater Flow and Transport Modeling Report, Allen Steam
Station, Belmont, NC. December 2019 [CAP Model, 2019 Appendix G].
SynTerra. (2020). Long -Term Seasonal High Groundwater Elevation Estimation, Allen Steam
Station, Belmont, North Carolina. June 2020.
SynTerra. (2022). Groundwater Modeling to Support Vertical Separation — North Starter Landfill
3619-INDUS. February 2022.
synterracorp.com

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station
FIGURES
synterracorp.com

I= •
DUKE ENERGY CAROLINAS
PROPERTY LINEN c+t F
• 0;c • et
..`�..
J I n'p
40 NORTH J STEAM STATION
00000
I' DISCHARGE STARTER
CANAL LANDFILL
(NSLF) •
.0
• y . 'COAL PILE AREA
RETIRED ASH BASIN
+" •/ I WASTE BOUNDARY
No me RETIRED ASH BASIN
ASH LANDFILL
.� BOUNDARY
r I
PROPOSED
LEACHATE —'—�
BASIN , PROPOSED
ASH BASIN
LANDFILL
• ACTIVE ASH BASIN ACTIVE ASH BASIN
WASTE BOUNDARY
FUTURE
SOUTH
• /--' STARTER
�+ • LANDFILL
(SSLF)
ASH BASIN
GEOGRAPHIC
LIMITATION `O
r: r irn A0.2m
'4r
�S
�•erdam C'
NOTES:
1. WATER FEATURES DEPICTED WITHIN WASTE BOUNDARIES OF THE ASH
BASINS ON THE 2019 USGS TOPOGRAPHIC MAP DO NOT REPRESENT
CURRENT CONDITIONS. THE CONDITIONS DEPICTED ARE SIMILAR TO
THOSE SHOWN ON THE 1968AND 1973 USGS TOPOGRAPHIC MAPS OF
THE AREA [(1968 WEST CHARLOTTE (1:24000) AND 1973 BELMONT (1:24000)].
-
2. ALL BOUNDARIES ARE APPROXIMATE. -
SOURCE: -..
2019 USGS TOPOGRAPHIC MAP, BELMONT & CHARLOTTE WEST -_
QUADRANGLE, OBTAINED FROM THE USGS STORE AT --
HTTPS://NGM DB. USGS.GOV/.
(� DUKE
FIGURE 1
USGS LOCATION MAP
ENERGY®
W/NSTONSALEM
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION
CAROLINAS
SOUTH STARTER LANDFILL 3620-INDUS
ASHEVILLE •
•
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA
��
CHARLOTTE
DRAWN BY: C. WYATT
REVISED BY: R. YU
DATE: 04/25/2020
DATE: 07/06/2023
GRAPHIC SCALE
000 o L,000 000
GASTON
COUNTY
CHECKED BY: E. HICKS
DATE: 07/06/2023
(IN FEET)
synTerra
APPROVED BY:C.SUTTELL
PROJECT MANAGER: C. SUTTELL
DATE: 07/06/2023
www.svnterracorD.COM

O O O - •
O O 3 gjp
O O O O O O O O ,■i •
O O ) . u%' Active Ash Basin •
• O )�� Polishing Pond
Central Conveyance Ditch Lake Wylie
• err w Removed on February 10, 2022 '
�c�at>
40
Tww
Southern Conveyance Ditch
• Placed on February 10, 2022
O • •
O
NOTES:
•
LEGEND 1. ALL BOUNDARIES ARE APPROXIMATE. •
2 DRAIN BOUNDARY FEATURES INCLUDE WETLANDS SUMPS CHANNELS PONDED
•
WATER SUPPLY WELL WITH SEPTIC RETURN
WATER, DEWATERING DITCHES, AND POTENTIAL NATURAL DRAINAGE FEATURES.
f'DUKE
4
330 ORAPHICSC330 660
ENERGY
o
SEPTIC RETURN
3. GENERAL HEAD BOUNDARY FEATURES INCLUDE PONDED WATER AND LAKE WYLIE.
CAROLINAS
(IN FEET)
POND
REPRESENTING THEEWAT
LINEAR DRAIN BOUNDARY FEATURE
DECREASES IN SIZE W THOTIME TO REPRESENT DECLI NGRY RASHASIN LE LEVELS IN THPOLISHIEG
DRAWN BY: J. EBENHACK DATE: 03/07/2023
POLISHING POND.
REVISED BY: DATE: 07/07/2023
PROPOSED SSLF LIMIT OF WASTE
5. AERIAL PHOTOGRAPHY OBTAINED FROM ESRI ON APRIL 21, 2020. AERIAL WAS
7
CHECKED BY.' R. YU DATE: 07/07/2023
COLLECTED ON FEBRUARY 1, 2019.
APPROVED BY: C. SUTTELL DATE: 07/07/2023
AERIAL DRAIN BOUNDARY FEATURE
6. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
Terra
PROJECT MANAGER: C. SUTTELL
�j
GENERAL HEAD BOUNDARY FEATURE
COORDINATE SYSTEM RIPS 3200 )NAD63).
�
www.s nterracor .com
FIGURE 2
ACTIVE ASH BASIN WASTE BOUNDARY
CALIBRATION MODEL HYDRAULIC
FEATURES NEAR THE
FUTURE SSLF
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Dam
Recharge = 0.00001 feet/day
Active Ash Basin Polishing Pond
`v ! Recharge = 0 feet/day
Background
Recharge = 0.0019 feet/day
r.
tomF
f fi Fy,,ggp .
1 rr=chin
Q RECHARGE ZONES
Q PROPOSED SSLF LIMIT OF WASTE
ACTIVE ASH BASIN WASTE BOUNDARY
r
;t
x �
Lake Wylie
Recharge = 0 feet/day
NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
DUKE
ENERGY
2. AERIAL PHOTOGRAPHY OBTAINED FROM ESRI ON APRIL 21, 2020. AERIAL WAS
CAROLINAS
COLLECTED ON FEBRUARY 1, 2019.
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD83).
1100111,
svnTerra
GRAPHIC SCALE
330 0 330 660
(IN FEET)
DRAWN BY: J. EBENHACK DATE: 03/07/2023
REVISED BY: DATE: 06/21/2023
CHECKED BY: R. YU DATE: 06/21/2023
APPROVED BY: C. SUTTELL DATE: 06/21/2023
PROJECT MANAGER:
FIGURE 3
CALIBRATION MODEL RECHARGE DISTRIBUTION
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

AB-25S
LB-PZ-2 AB-24S i. AB-25SS AB-26D 1
AB-24SL GWA-3S
AB-25SL GWA-3D
AB-24D AB-25BRU GWA-3BRA
AB-24BR AB-25BR f:
'i4 1. LB PZ 3 ABLF PZ 1 . t E'
-n ,.,a�+l
AB-23S CCR-16S F.
CCR-17S
b T CCR-17D
AB-22St', AB-10BRL
AB- 22D - AB-10BR
L X AB-21S s AB-22BR AB
;. AB-21SS AB-22BRL AB-10S
AB-21SL AB-6A
AB-21 D AB-6R
aW1� AB-21BRL CCR-18S
CCR-21 S CCR 18D
• L = <. ; CCR-21 D
CCR 211 0S
CCR 20
AB-5D
CCR-22S SSLF-PZ-1 �.
ry SSLF PZ-2
}? CCR-22DA
GWA-1 S ..
1 CCR-23S GWA-1 BR GWA-2S
' CCR-23D GWA-1 D GWA-2D
1,
AB-11 D
LEGEND NOTES: GRAPHIC SCALE
1. ALL BOUNDARIES ARE APPROXIMATE. (DUKE 330 0 330 660
ENERGY
MONITORING WELL OR PIEZOMETER
2. ONLY THE MONITORING WELLS AND PIEZOMETERS USED IN HEAD CALIBRATION ARE SHOWN. CAROLINA$ (IN FEET)
3. AERIAL PHOTOGRAPHY OBTAINED FROM ESRI ON APRIL 21, 2020. AERIAL WAS COLLECTED ON DRAWN BY: J. EBENHACK DATE: 03/07/2023
ACTIVE ASH BASIN WASTE BOUNDARY FEBRUARY 1, 2019. REVISED BY: DATE: 03/15/2023
PROPOSED SSLF LIMIT OF WASTE 4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE COORDINATE CHECKED BY: R.YU DATE: 03/15/2023
SYSTEM FIP53200 (NAD83 AND NAVD88). , APPROVED BY: C.SUTTELL DATE: 03/15/2023
PROJECT MANAGER;
svnTerra c`
FIGURE 4
CALIBRATION MODEL MONITORING WELLS AND PIEZOMETERS
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

0
o °
o O
0
o o 0
0 0 ° 0 0 0
• O °
z:
o
rl�lllx
O
Lake Wylie
1 •I
•
LEGENDNOTES.
1. ALL BOUNDARIES ARE APPROXIMATE.
PROPOSED DEWATERING WELL
2. DRAIN BOUNDARY FEATURES INCLUDE THE CONSTRUCTION DRAIN, WETLANDS, SUMPS,
• •
CHANNELS, PONDED WATER, DEWATERING DITCHES, AND POTENTIAL NATURAL DRAINAGE
FEATURES.
INSTALLED DEWATERING WELL
3. GENERAL HEAD BOUNDARY FEATURES INCLUDE PONDED WATER AND LAKE WYLIE.
GRAPHIC SCALE
f' DUKE 330 0 330 660
• WATER SUPPLY WELL WITH SEPTIC RETURN
4 EXCAVATION AND DEWATERING IN THE ACTIVE ASH BASIN WAS SIMULATED USING A DRAIN
BOUNDARY FEATURE WITH DRAIN ELEVATIONS THAT DECREASED WITH TIME TO MATCH THE
ENERGY
PROPOSED ACTIVE ASH BASIN EXCAVATION SCHEDULE AS PROVIDED BY DUKE ENERGY
CAROLINAS (IN FEET)
c SEPTIC RETURN
CAROLINAS.
DRAWN BY: J. EBENHACK DATE: 03/07/2023
LINEAR DRAIN BOUNDARY FEATURE
5. AERIAL IMAGERY IS A COMBINATION OF DUKE ENERGY PROPELLER PHOTOGRAPHY COLLECTED
ON JUNE 13, 2023 AND AERIAL PHOTOGRAPHY OBTAINED FROM ESRI, COLLECTED ON MAY 16,
2022.
REVISED BY: E. ORDEMANN DATE: 07/07/2023
CHECKED BY: E. HICKS DATE: 07/07/2023
PROPOSED SSLF LIMIT OF WASTE
COORDINATE SYSTEM FIPS 200(NAD83NG HAS BEEN SET WITH A �ECTIONOFNORTHCAROLINASTATEPANE
APPROVED BY: C. SUTTELL DATE: 07/07/2023
PROJECT MANAGER: C. SUTTELL
® SIMULATED EXCAVATION AND DEWATERING AREA
errd
synT
www.synterracori).com
FIGURE 5
AERIAL DRAIN BOUNDARY FEATURE
PREDICTIVE MODEL HYDRAULIC FEATURES NEAR THE FUTURE SSLF
GENERAL HEAD BOUNDARY FEATURE
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ACTIVE ASH BASIN WASTE BOUNDARY
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

f
Background
Recharge = 0.0019 feet/day
s•
t..
Dam
Recharge = 0.00001 feet/day ;w
6
SSLF Recharge
12/1/22 - 6/21/24: 0.0019 feet/day
6/21/24 - model end: 0 feet/dav
LEGEND
Q PROPOSED SSLF LIMIT OF WASTE
Q RECHARGE ZONES
L ACTIVE ASH BASIN WASTE BOUNDARY
Lake Wylie
Recharge = 0 feet/day
NOTES:
1.ALL BOUNDARIES ARE APPROXIMATE.
2. THE RECHARGE RATE IS REDUCED TO ZERO IN THE PROPOSED SSLF FOOTPRINTTO ACCOUNT
FOR PLACEMENT OF THE SECONDARY 60-MIL HDPE TEXTURED GEOM EMBRANE LINER. DATE OF
DUKE
4 ENERGY
CAROLINAS
GRAPHIC SCALE
330 0 330 660
(IN FEET)
LINER PLACEMENT WAS PROVIDED BY DUKE ENERGY CAROLINAS AND IS ASSUMED TO BE THE
PROPOSED DATE OF THE LINER SURVEY.
DRAWN BY: J. EBENHACK DATE: 03/07/2023
3. AERIAL IMAGERY IS A COMBINATION OF DUKE ENERGY PROPELLER PHOTOGRAPHY
COLLECTED ON JUNE 13, 2023 AND AERIAL PHOTOGRAPHY OBTAINED FROM ESRI, COLLECTED
REVISED BY: E. ORDEMANN DATE: 06/21/2023
CHECKED BY: E. HICKS DATE: 06/21/2023
ON MAY 16, 2022.
APPROVED BY: C. SUTTELL DATE: 06/21/2023
4. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
PROJECT MANAGER;
COORDINATE SYSTEM RIPS 3200 (NAD83).
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.nrn..
FIGURE 6
PREDICTIVE MODEL RECHARGE DISTRIBUTION
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

ALIN C901.027.016A — A
_
LEGEND
t . -
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f r
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z /
., 'y A n����
/ /
/ �i ExS�uu.�Euu »aEoaoukio»E
•
obi .�
F ary
ii -.
�i -
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iNF
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>, �y l I
� I�1I
o
t��IA
_r
D
r
fti
_ �. — .�>. .. Rom..
LANDFILL LINER SYSTEM
NOT TO SCALE
n . r.nnn r, ansmvn
_�_-.( M f •f- 3 I / +`"0 /`-- �\- res GRn nt, sCnit yr t;
TL
EOROUNUOATER MANAGEMENT PLAN $$LF
..... A=C�M RALLfNRSTEB.I'1'— N o.Rr
LF(3s [uou nrvo ssLF laszo .ry
o, o NTV, ,oR.R ARo NA
- - _ I FILL- v... -nr. - -rer �: '9P LF PEI.IIT TO QUNSTRMT I.w FIc ION REQUEST
LL
DUKEj ENERGY
ON El
ear _
oPP,6 e„ ERTRP�a�sR��,oti
T_E _
or n P K o, nr�da n sn« "' m ALN 90 1"'O"'27.016AI A
ao
DUKE DRAWN BY: J. EBENHACK DATE: 03/07/2023
ENERGY REVISED BY: DATE: 03/07/2023
c, vas CHECKED BY: R. YU DATE: 03/08/2023
APPROVED BY: C. SUTTELL DATE: 03/15/2023
�+ PROJECT MANAGER: C. SUTTELL
WnTerm www.synterracorp.com
FIGURE 7
FUTURE SSLF CONSTRUCTION DRAIN DESIGN (AECOM, 2023)
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION — SOUTH STARTER
LANDFILL 3620—INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model 3 - Model Without Dewatering Wells
Model 4 - Model With Dewatering Wells
or the Construction Drain
and the Construction Drain
LEGEND
NOTES:
DUKpE
GRAPHIC SCALE
160 0 160 320
1. ALL BOUNDARIES ARE APPROXIMATE.
y
ENOLRG I-
INSTALLED DEWATERING WELL
2.CONSTRUCTION DRAIN COMPONENTS SIMULATED AS MODFLOW DRAIN BOUNDARY
CONDITIONS. DEWATERING WELLS SIMULATED USING THE MNW2 MODFLOW PACKAGE
INAS
(IN FEET)
DRAWN BY:1 EBENHACK DATE: 03/07/2023
REVISED BY: E. ORDEMANN DATE: 06/19/2023
1 PROPOSED DEWATERING WELL
3. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
SSLF SU BG RADE CONTOUR
COORDINATE SYSTEM RIPS 3200 (NAD83(.
7
CHECKED BY: E. HICKS DATE: 06/19/2023
APPROVED BY: C. SUTTELL DATE: 06/19/2023
CONSTRUCTION DRAIN LATERAL
s)mPIOIECTMANAGER:
Terra
C.SUTTELL
www.synterracorp.com
CONSTRUCTION DRAIN SUMP
FIGURE 8
MODELED SCENARIOS FOR THE FUTURE SSLF IN THE PREDICTIVE MODEL
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

R
NOTESLEGEND GRAPHIC SCALE
1. ALL BOUNDARIES ARE APPROXIMATE. `DUKE 290 0 290 580
4 ENERGY
2. WATER ELEVATION CONTOURS ARE SHOWN FOR 2/1/2019 FROM THE HISTORICAL PRE- ESTIMATED WATER ELEVATION (FEET) CAROLINAS (IN FEET)
DECANTING MODEL WITH THE REFINED MODEL GRID.
3. WATER ELEVATION CONTOURS ARE SHOWN FOR TOP SAPROLITE LAYER 12. ACTIVE ASH BASIN WASTE BOUNDARY DRB. EBENHACK DATE: 03/O9/2023
REVVISEDISEDBY: DATE: 03/09/2023
4. WATER ELEVATION CONTOUR INTERVAL IS 5 FEET PROPOSED SSLF LIMIT OF WASTE APPROVED BY: C.SUTTELL DATE: 03/09/2023 CHECKED BY: R.YU DATE: 03/09/2023
5. AERIAL PHOTOGRAPHY OBTAINED FROM ESRI ON APRIL 21, 2020. AERIAL WAS COLLECTED ON PROJECT MANAGER:
FEBRUARY 1, 2019. rra Te
6. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE 1 �� CCAA11 www.s7nterracorp.com
COORDINATE SYSTEM RIPS 3200(NAD83 AND NAVD88). FIGURE 9
ESTIMATED INITIAL GROUNDWATER ELEVATIONS FOR THE CALIBRATION MODEL
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

�N
LEGENDNOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
• CALIBRATION TARGETS
2. RESIDUALS ARE CALCULATED AS COMPUTED HEADS MINUS OBSERVED HEADS. RESULTS ARE
SHOWN FOR SEPTEMBER 1, 2022.
ESTIMATED WATER ELEVATION (FEET)
3. AERIAL PHOTOGRAPHY OBTAINED FROM ESRI ON APRIL 21, 2020. AERIAL WAS COLLECTED ON
FEBRUARY 1, 2019.
ACTIVE ASH BASIN WASTE BOUNDARY
q DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
QPROPOSED SSLF LIMIT OF WASTE
COORDINATE SYSTEM HIPS 1210(NAD83 AND NAVD88).
(' DUKE
4 ENERGY.
100 GRAPHIC SCALE100 200
CAROLINAS
(IN FEET)
DRAWN BY: J. EBENHACK
REVISED BY:
DATE: 03/07/2023
DATE: 06/22/2023
CHECKED BY: R.YU
DATE: 06/22/2023
APPROVED BY: C.SUTTELL
DATE: 06/22/2023
svnTerra
PROJECT MANAGER
c
'^^✓„ ^^�
ERROR BARS (RESIDUALS) FIGURE 10
< 3.5 FEET CALIBRATION MODEL RESIDUALS NEAR THE FUTURE SSLF
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

619
m 617
m
-�- 615
c
613
m
y 611
W
L 609
m
607
3
605
0 603
0
601
1�
581
579
-�- 577
c
575
m
y 573
W
L 571
m
m 569
3
567
0 565
0
563
01� 01c� O3O OHO Ocl�
IN N, �11
Date
A13-611: Modeled CAB-611: Observed
n DUKE DRAWN BY: J. EBENHACK DATE: 03/07/2023
ENERGY REVISED BY: DATE: 03/07/2023
cl° CHECKED BY: R. YU DATE: 03/08/2023
APPROVED BY: C. SUTTELL DATE: 03/15/2023
PROJECT MANAGER: C. SUTTELL
AB-11D
1c� OLO OLO pL� OLD O'-V O'L� O'L3 O1L115
Date
--m AB-11D: Modeled CAB-11D: Observed
"IF'
synTerra
www.synterracorp.com
O"05 O1.115
580
m 578
m
�— 576
c
574
m
y 572
W
L 570
m
568
3
566
564
L7
562
'y�ti��010)
a
oyo oyo oyti oyti oyti otiti o�3 oy3
Date
A13-6A: Modeled fAB-6A: Observed
FIGURE 11A
COMPUTED VS OBSERVED HYDRAULIC HEADS IN CALIBRATION MONITORING WELLS AND
PIEZOMETERS NEAR THE SSLF
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

582
17
m 580
m
-�- 578
c
576
m
y 574
W
572
m
570
3
568
0 566
0
564
1�
CCR-18D
Q1� QUO QtiO Qti1 O�y O'-V O�'L Otis 0.1"5
Date
CCR-18D: Modeled +CCR-18D: Observed
CCR-20D
579
m 577
m
�- 575
c
573
m
y 571
W
569
m
567
3
565
0 563
C7
561
10)
0
CCR-18S
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
f CCR-18S: Modeled fCCR-18S: Observed
CCR-20S
612
611
m 610
17
m
609
m
m
-�- 608
- -
=
607
606
— -
- -
605
-
y 604
y
603
- -
W
602
W
601
m
m
m 600
- -
-
m
599
— -
3
3
598
- - - - -
597
-
0 596
-
0
595
—
L7
C7
594
593
01� Q1�
'1'�L
QUO QUO O�� O�� O�� O�� O�� O��
01�
01� QUO QUO Q�� O�y O�� O�� O�� Oy
'1',�L
yy�L
y'�L 1',y�L �'ti�ti 11'L y,��ti �,3�ti �,L�l
1,��ti
yy�L
y'�L
Date
Date
�
CCR-20D: Modeled CCR-20D: Observed
- CCR-20S: Modeled CCR-20S: Observed
DUKE
DRAWN BY:: EBENHACK DATE: 03/07/2023
FIGURE 11B
ENERGY
REVISED BY: DATE: 03/07/2023
COMPUTED VS
OBSERVED HYDRAULIC HEADS IN CALIBRATION MONITORING WELLS AND
c.°
CHECKED BY: R. YU DATE: 03/08/2023
PIEZOMETERS NEAR THE SSLF
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
synTerraF
www.synterracorp.com
GASTON COUNTY, NORTH CAROLINA

632
m 630
m
-�- 628
c
626
m
y 624
W
L 622
m
620
3
618
0 616
0
614
1�
CCR-21 D
Q1� QLO Qti0 Qti1 O�ti O"V O'L� O'L� O'L�
Date
CCR-21D: Modeled +CCR-21D: Observed
CCR-22DA
634
m 632
—
m
630
c
628
m
y 626
W
L 624
m
m 622
3
620
0 618
L9
616
1�
0
CCR-21S
Qya Qyo Qyo Qyti o�yti o�yti Qtiti O'y3 Qti3
Date
f CCR-21S: Modeled fCCR-21S: Observed
CCR-22S
634
637
m 632
m
635
m
m
-�- 630
=
633
628
- - -
—
631
m
y 626
�
- - -
m
y
629
W
L 624
- -
W
L
627
m
m
m 622
m
625
3
3
620
-
623
0 618
—
— 0
621
—
L7
C7
616
619
01� Q1�
QUO QUO O�� O�� O�� O�� O�� Oy
'L1,4T
01
01� QUO QUO
Date
Date
f CCR-22DA: Modeled CCR-22DA: Observed
- CCR-22S: Modeled +CCR-22S: Observed
%' DUKE
DRAWN BY:: EBENHACK DATE: 03/07/2023
FIGURE 11C
ENERGY
REVISED BY: DATE: 03/07/2023
COMPUTED VS
OBSERVED HYDRAULIC HEADS IN CALIBRATION MONITORING WELLS AND
c.°
CHECKED BY: R. YU DATE: 03/08/2023
PIEZOMETERS NEAR THE SSLF
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
synTerraF
www.synterracorp.com
GASTON COUNTY, NORTH CAROLINA

636
17
m 636
m
-�- 634
c
632
m
y 630
W
L 628
m
626
3
624
0 622
0
620
1�
CCR-23 D
Q1c� QUO QtiO Qti1 O�y O'-V O�'L Otis 0.111
5
Date
CCR-23D: Modeled +CCR-23D: Observed
GWA-1BR
CCR-23S
637
m 635
m
= 633
c
631
m
y 629
W
L 627
m
m 625
3
623
0 621
(9
619
N,��
Date
f CCR-23S: Modeled fCCR-235:Observed
GWA-1D
621
622
m 619
m
620
m
m
L.
617
618
-
615
i I I
0
616
y 613
y
614
W
L 611
W
L
612
m
m
3 609
- - ■--■ -
3
610
—
-
607
- -
608
- —
0 605
- -
0
606
—
L7
C7
603
604
01� Q1�
QUO QUO O�� O�� O�� O�� O�� O��
01�
01� QUO QUO Q�� O�y O�� O�� O�� Oy
'1',�L
y'�L 1',y�L �'ti�ti 11'L y,��ti �,3�ti �,L�l
1,��ti
yy�L
y'�L
Date
Date
{ GWA-113R: Modeled tGWA-1l3R: Observed
- GWA-11D: Modeled GWA-1D: Observed
%' DUKE
DRAWN BY:: EBENHACK DATE: 03/07/2023
FIGURE 11D
ENERGY
REVISED BY: DATE: 03/07/2023
COMPUTED VS
OBSERVED HYDRAULIC HEADS IN CALIBRATION MONITORING WELLS AND
c.°
CHECKED BY: R. YU DATE: 03/08/2023
PIEZOMETERS NEAR THE SSLF
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
synTerra
www.synterracorp.com
GASTON COUNTY, NORTH CAROLINA

622
m 620
m
-�- 618
c
616
m
y 614
W
612
m
610
3
608
0 606
0
604
1�
580
m 578
m
-�- 576
c
574
m
y 572
W
570
m
m 568
3
566
0 564
0
562
01� 01c� O3O OHO Ocl�
IN N, �11
Date
--0 GWA-2S: Modeled tGWA-2S: Observed
n DUKE DRAWN BY: J. EBENHACK DATE: 03/07/2023
ENERGY REVISED BY: DATE: 03/07/2023
cl° CHECKED BY: R. YU DATE: 03/08/2023
APPROVED BY: C. SUTTELL DATE: 03/15/2023
PROJECT MANAGER: C. SUTTELL
GWA-1S
01c� OHO OtiO Oti1 O�y O'-V O�'L Otis 0.111
5
Date
GWA-1S: Modeled +GWA-1S: Observed
GWA-2S
"IF'
synTerra
www.synterracorp.com
O"05 O1.115
GWA-2D
583
m 581
m
�- 579
- - -
c
577
- - - -
m
y 575
— -
W
573
—
m
I
571
—
3
569
— - —
—
0 567
— —
(9
565 '
010) O�c� OHO OHO
Date
fGWA-2D: Modeled fGWA-2D: Observed
FIGURE 11E
COMPUTED VS OBSERVED HYDRAULIC HEADS IN CALIBRATION MONITORING WELLS AND
PIEZOMETERS NEAR THE SSLF
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

630
17
m 628
m
-�- 626
c
624
m
y 622
W
620
m
618
3
616
0 614
L7
612
1�
,yQ
SSLF-PZ-1
Q1c� QUO QtiO Qti1 O�y O'-V O�'L Otis 0.111
5
Date
SSLF-P2-1: Modeled SSLF-P2-1: Observed
SSLF-PZ-3
SSLF-PZ-2
611
m 609
m
607
c
605
m
y 603
W
601
m
m 599
3
597
0 595
C7
593
Q'�a Qti° Qti° Qtiti otiti o'��' oti�" oti�' Qti�'
Date
SSLF-P2-2: Modeled +SSLF-P2-2: Observed
SSLF-PZ-4
604
628
a4i 602
......••
m
626
d
m
600
=
624
c
598
c
622
- -
y 596
y
620
- - -
W
594
W
618
m
m
m 592
m
616
— —
3
3
c 590
614
588
612
—
C7
C7
586
610
.
O?g Q1c�
Qti0 Q1O Qn1 0n1 O'}0 O'L� OL3 O`!�
(3
13 QLO Q3 Q�1 O1, O'L� q'v q Oy
'L 'L 'L 'L
Date
Date
-
SSLF-P2-3: Modeled (SSLF-P2-3: Observed
SSLF-P2-4: Modeled SSLF-P2-4: Observed
%' DUKE
DRAWN BY:: EBENHACK DATE: 03/07/2023
FIGURE 11F
ENERGY
REVISED BY: DATE: 03/07/2023
COMPUTED VS
OBSERVED HYDRAULIC HEADS IN CALIBRATION MONITORING WELLS AND
c.°
CHECKED BY: R. YU DATE: 03/08/2023
PIEZOMETERS NEAR THE SSLF
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
synTerra
www.synterracorp.com
F
GASTON COUNTY, NORTH CAROLINA

NOTES:
1. ALL BOUNDARIES ARE APPROXIMATE.
2. WATER ELEVATION CONTOURS ARE SHOWN FOR DECEMBER 1, 2022 FROM THE TRANSIENT
CALIBRATION MODEL.
3. WATER ELEVATION CONTOURS ARE SHOWN FOR TOP SAPROLITE LAYER 12.
4. WATER ELEVATION CONTOUR INTERVAL IS 5 FEET.
5. AERIAL PHOTOGRAPHY OBTAINED FROM ESRI ON APRIL 21, 2020. AERIAL WAS COLLECTED ON
FEBRUARY 1, 2019.
6. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM RIPS 3200 (NAD83 AND NAVD88).
I FrFNn
ESTIMATED WATER ELEVATION (FEET)
ACTIVE ASH BASIN WASTE BOUNDARY
r PROPOSED SSLF LIMIT OF WASTE
GRAPHIC SCALE
�> DUKE 290 0 290 580
4 ENERGY
CAROLINAS (IN FEET)
DRAWN BY: J. EBENHACK DATE: 03/07/2023
REVISED BY: DATE: 03/09/2023
CHECKED BY: R.YU DATE: 03/09/2023
APPROVED BY: C.SUTTELL DATE: 03/09/2023
. Terra PROJECT MANAGER; c`
,�re..�.....h
FIGURE 12
ESTIMATED INITIAL GROUNDWATER ELEVATIONS FOR THE PREDICTIVE MODEL
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/1/2023
Model —4: Model With SSLF Dewatering Measures
1/1/2023
Simulated Vertical
Separation (feet)
Separation
Achieved
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
synTerm
FIGURE 13A
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/1/2023)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/18/2023
Model —4: Model With SSLF Dewatering Measures
1/18/2023
Simulated Vertical
Separation (feet)
Separation
Achieved
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
s)mTerm
FIGURE 13B
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/18/2023)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
7/31/2023
Model —4: Model With SSLF Dewatering Measures
7/31/2023
Simulated Vertical
Separation (feet)
Separation
Achieved
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
www.synterracorp.com
s)mTerm
FIGURE 13C
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(7/31/2023)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
8/31/2023
Model —4: Model With SSLF Dewatering Measures
8/31/2023
Simulated Vertical
Separation (feet)
Separation
Achieved
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
synTerm
FIGURE 13D
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(8/31/2023)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
12/1/2023
Model —4: Model With SSLF Dewatering Measures
12/1/2023
Simulated Vertical
Separation (feet)
Separation
Achieved
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
synTerm
FIGURE 13E
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(12/1/2023)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
3/15/2024
Model —4: Model With SSLF Dewatering Measures
3/15/2024
Simulated Vertical
Separation (feet)
Separation
Achieved
SLF Construction
rain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
I---. DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
r. ' ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
s)mTerm
FIGURE 13F
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(3/1S/2024)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
6/25/2024
Model —4: Model With SSLF Dewatering Measures
6/25/2024
ii�✓ice'
Simulated Vertical
Separation (feet)
Separation
Achieved
SSLF Construction
Drain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C.SUTTELL
PROJECT MANAGER: C. SUTTELL
DATE:03/15/2023
1
www.synterracorp.com
synTerm
FIGURE 13G
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(6/2S/2024)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/1/2025
Model —4: Model With SSLF Dewatering Measures
1/1/2025
f/ii✓ice' ` -
Simulated Vertical
Separation (feet)
Separation
Achieved
SSLF Construction
Drain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
s)mTerm
FIGURE 13H
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/1/2025)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/1/2026
Model —4: Model With SSLF Dewatering Measures
1/1/2026
'�g
3 r
Simulated Vertical
Separation (feet)
Separation
Achieved
SSLF Construction
Drain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
s)mTerm
FIGURE 131
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/1/2026)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/1/2027
Model —4: Model With SSLF Dewatering Measures
1/1/2027
'�g
Simulated Vertical
Separation (feet)
Separation
Achieved
SSLF Construction
Drain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
0
www.synterracorp.com
s)mTerm
FIGURE 13J
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/1/2027)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/1/2028
Model —4: Model With SSLF Dewatering Measures
1/1/2028
Simulated Vertical
Separation (feet)
Separation
Achieved
SSLF Construction
Drain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
synTerm
FIGURE 13K
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/1/2028)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/1/2029
Model —4: Model With SSLF Dewatering Measures
1/1/2029
Simulated Vertical
Separation (feet)
Separation
Achieved
SLF Construction
rain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
s)mTerm
FIGURE 13L
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/1/2029)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
9/9/2029
Model —4: Model With SSLF Dewatering Measures
9/9/2029
Simulated Vertical
Separation (feet)
32.0
-
24.0
20.0
16.0
12.0
Separation
8.0
Achieved
4.0
0.0
-4.0
-8.0
\
-12.0
SSLF Construction
Drain Sump
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
synTerm
FIGURE 13M
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(9/9/2029)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Model — 3: Model Without SSLF Dewatering Measures
1/1/2032
Model —4: Model With SSLF Dewatering Measures
1/1/2032
Simulated Vertical
Separation (feet)
Separation
Achieved
SLF Construction
rain Sump
32.0
24.0
20.0
16.0
12.0
8.0
4.0
0.0
-4.0
-8.0
-12.0
NOTES:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF
become operational on July 31, 2023, and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023.
Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain becomes operational on March 15, 2024.
3. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero
in the footprint of the SSLF.
4. Vertical separation is calculated as the CSL (compacted soil liner) subgrades minus simulated groundwater table elevations.
(� DUKE
DRAWN BY: J. EBENHACK
DATE: 03/07/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/20/2023
CAROLINA
CHECKED BY: E. HICKS
DATE: 03/08/2023
APPROVED BY: C. SLITTELL
PROJECT MANAGER: C. SLITTELL
DATE:03/15/2023
1
www.synterracorp.com
synTerm
FIGURE 13N
SIMULATED VERTICAL SEPARATION BETWEEN THE
GROUNDWATER TABLE AND THE SSLF CSL SUBGRADE
(1/1/2032)
GROUNDWATER MODELING TO SUPPORTVERTICAL
SEPARATION —SOUTH STARTER LANDFILL3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

10
8
T
0
LL 4
2
0
ti
ii
�s
Base Model
— — — Dewatering Wells 10 ft Deeper
— — — Dewatering Wells 10ft Shallower
----- 5pecif icYield = 0.2
5pecif icYield = 0.01
— — Drain Conductance = 10 ft2/day/ft
— — Drain Conductance = 0.1 ft2/day/ft
Long Term Seasonal High Recharge Rate
,�oy3 y,�o �o,�oti� �,�'� '�o'�oyti �,y,�o�o �,�,�oy� o,�,�oy� �,y,�o�� o,�'�oy� �'y,�oyw �,9,�qy� �,oti� �,�o �,�0 0�3,�o�ti
titi h NY ti ti 1 1 ti ti
Date
Notes:
1. Model assumes construction drain operation starts on March 15, 2024.
2. Base model assumptions: Dewatering well depth is approximately 70 feet below ground surface; specific yield in ash, saprolite, and transition zone = 0.1; lateral drain conductance = 1
feetz/day/foot; sump drain conductance = 1 feet2/day/ feetz; recharge rate = 8.3 in/year.
3. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF become operational on July 31, 2023, and
proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023. Dewatering wells stop operating on March 15, 2024.
4. Model assumes the secondary 60-MIL HDPE textured geomembrane liner is placed on June 21, 2024, which is simulated by reducing recharge to zero in the footprint of the SSLF.
5. Actual construction drain flow rates may vary from simulated flow rates because of uncertainty in drain installation methods, model assumptions and simplifications, and model uncertainty.
6. Predicted construction drain operation duration for each modeled scenario (i.e., period when simulated flow rate is greater than zero) is listed in Table 3.
7. gpm = gallons per minute
S■' DUKE
DRAWN BY: J. EBENHACK
DATE: 03/08/2023
ENERGY
REVISED BY: J. EBENHACK
DATE: 06/21/2023
CAROLINAS
CHECKED BY: R. YU
DATE: 03/08/2023
APPROVED BY: C. SUTTELL
PROJECT MANAGER: C. SUTTELL
DATE: 03/15/2023
101
synTerra
www.synterracorp.com
FIGURE 14
PREDICTED CONSTRUCTION DRAIN FLOW RATE
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

350.00
250.00
9
ptg200.00
V1
W
4+
M
CC
3 150.00
G
LL
50.00
0.00
o�y� �oti3 �'0,�3 �,oti3 �,o�� �'0�3 �,0�3 �,0�3 �o'o�y� ���0�3 ��,�oti3 y,�oti� �,o�a �'30�� �,�,�o�� y,�'�o�a
Date
Notes:
1. Model assumes pilot dewatering wells become operational on January 18, 2023, proposed dewatering wells outside of the footprint of the SSLF become operational on July 31, 2023,
and proposed dewatering wells within the footprint of the SSLF become operational on August 31, 2023. Dewatering wells stop operating on March 15, 2024.
2. Model assumes construction drain operation starts on March 15, 2024.
3. Base model assumptions: Dewatering well depth is approximately 70 feet below ground surface; specific yield in ash, saprolite, and transition zone = 0.1; lateral drain conductance = 1
feetz/day/foot; sump drain conductance = 1 feetz/day/ feetz; recharge rate = 8.3 in/year.
4. gpm = gallons per minute
5. Actual flow rates to the dewatering wells may vary from simulated flow rates because of actual conditions encountered in the field and model assumptions and uncertainty.
(' DUKE
V ENERGY
DRAWN BY: J. EBENHACK
REVISED BY: J. EBENHACK
DATE: 03/08/2023
DATE: 06/21/2023
c+
CHECKED BY: R. YU
DATE: 03/08/2023
APPROVED BY: C. SUTTELL
PROJECT MANAGER: C. SUTTELL
DATE: 03/15/2023
/ 1
sc)mTerra
www.synterracorp.com
FIGURE 15
PREDICTED TOTAL FLOW RATE FROM THE DEWATERING WELLS
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION —
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
GASTON COUNTY, NORTH CAROLINA

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station
TABLES
synterracorp.com

TABLE 1
SITE ACTIVITIES (2019 TO 2022) INCORPORATED INTO THE CALIBRATION MODEL
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
DUKE ENERGY CAROLINAS, LLC, GASTON COUNTY, NC
Site Event
Approximate Dates
Calibration simulation begins
2/1/2019
Cessation of sluicing activities in primary ponds 1, 2, and 3
2/1/2019
AAB Polishing Pond elevations vary based on decanting levels
2/1/2019 through 9/1/2022
AAB South Ditch constructed (stage varies with time)
2/10/2022
AAB1 central ditch to Polishing Pond removed
2/10/2022
Calibration model simulation ends
9/1/2022
Notes:
AAB - Active Ash Basin
Prepared by: EMH checked by: JFE
Page 1 of 1

TABLE 2
ANTICIPATED SITE ACTIVITIES (2022 TO 2032) INCORPORATED INTO THE PREDICTIVE MODELS
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
DUKE ENERGY CAROLINAS, LLC, GASTON COUNTY, NC
Site Event
Approximate Dates
Predictive Model simulation begins
12/1/2022
AAB1 Polishing Pond active
12/1/2022
SSLF2 initial dewatering wells operational
1/18/2023
Proposed dewatering wells outside of the SSLF footprint operational
7/31/2023
Proposed dewatering wells inside of the SSLF footprint operational
8/31/2023
SSLF construction drain operational
3/15/2024
SSLF dewatering wells stop operating
3/15/2024
Survey of secondary geomembrane after installation, recharge reduced to zero in the SSLF footprint
6/21/2024
Excavation dewatering in AAB begins, elevation 624.0 ft
1/1/2025
Excavation dewatering in AAB continues, elevation 622.5 ft
1/1/2026
Excavation dewatering in AAB continues, elevation 620 ft
1/1/2027
Excavation dewatering in AAB continues, elevation 615 ft
1/1/2028
AAB Polishing Pond becomes inactive
1/1/2028
Excavation dewatering in AAB continues, elevation 610 ft
1/1/2029
Excavation dewatering in AAB continues, elevation 605 ft
1/1/2030
Excavation dewatering in AAB continues, elevation 600 ft
1/1/2031
Predictive Model simulation ends
1/1/2032
Notes:
AAB - Active Ash Basin
SSLF - South Starter Landfill
Prepared by: EMH Checked by:1FE
Page 1 of 1

TABLE 3
SUMMARY OF MODELED TIME TO REACH HEAD SEPARATION GOAL AND DRAIN OPERATIONAL TIMES
GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION - SOUTH STARTER LANDFILL 3620 - INDUS
ALLEN STEAM STATION
DUKE ENERGY CAROLINAS, LLC, GASTON COUNTY, NC
T
Sensitivitaration
Date
Date
Total Dewatering Well
Total Dewatering
ModelDate
.•
Analsis Value Units
Achieved at
..
Drain•.
•
:A�
SSLF Monitoring
Wells
FootprintParameter
SSLF
.
•
Baseline - Model without
SSLF Dewatering Measures
Not Applicable
12/1/2028
1/1/2029
Not Applicable
Not Applicable
Not Applicable
(Model 3)
Base Model - Model with
SSLF Dewatering Measures
See notes
10/1/2023
12/1/2023
9/13/2029
248.6
86.2
(Model 4)
Higher recharge resulted in a slightly longer time to reach separation
Background Recharge
0.002375
ft/day
11/1/2023
1/1/2024
1/1/2030
255.4
89.9
and increased the operational life of the construction drain. It slightly
Increased 25%
increased the flow rates from the dewatering wells.
Construction Drain
ft2/d/ft (lateral)
0.1
10/1/2023
12/1/2023
9/13/2029
248.6
86.2
Not sensitive: Does not significantly affect results.
ftz/d/ftZ (sump)
Conductance
Construction Drain
ftZ/d/ft (lateral)
10
10/1/2023
12/1/2023
9/13/2029
248.6
86.2
Not sensitive: Does not significantly affect results.
Conductance
ftz/d/ft' (sump)
Ash/Saprolite/Transition
Lower Sy results in a shorter time to achieve separation, a slightly
0.01
3
(ft3 /ft)
8/31/2023
9/1/2023
8/1/2028
181.4
67.4
shorter operational life of the construction drain, and lower flowrates
Zone Specific yield (Sy)
from the dewatering wells.
Sensitivity Analysis
Ash/Saprolite/Transition
Higher Sy results in a longer time to achieve separation, a longer
0.2
3 3
(ft /ft)
12/1/2023
4/1/2024
7/2/2030
273.2
101.7
operational life of the construction drain, and higher flowrates from
Zone Specific yield (Sy)
the dewatering wells.
Deeper wells did not change the time to reach separation at the
Dewatering Well
Configuration: Hlimit and
Decreased 10 ft
ft
10/1/2023
11/1/2023
9/13/2029
337.6
109.6
monitoring wells or the operational life of the construction drain but
decreased the time to reach separation in the footprint of the landfill.
screen bottom
It does result in higher flow rates from the dewatering wells.
Dewatering Well
Shallower wells increased the time to reach separation but did not
Configuration: Hlimit and
Increased 10 ft
ft
11/1/2023
1/1/2024
9/13/2029
169.5
63.5
affect the operational life of the construction drain. It does result in
screen bottom
lower flow rates from the dewatering wells.
Prepared by: EMH Checked by: JFE
Notes:
1. Sensitivity Analyses were run using the Base Case which is Option 4 with the Dewatering Wells Operating until head separation achieved in the SSLF footprint.
2. The Base Case model parameters are construction drain laterals with conductance values of 1 ftZ/d/ft and a sump conductance value of 1 ftZ/d/ft' ; a specific yield value in ash, saprolite, and transition zone of 0.1 (ft3/ft3); dewatering well screen bottom of 70 ft below ground surface and a dewatering well level (Hlimit) of 5 feet above the
bottom of the well; and a recharge rate of 8.3 in/year 65 ft below ground surface.
3. ft`/d/ft = feet squared per day per foot
4. ft`/d/ft` = feet squared per day per feet squared
5. inch/year = inches per year
6. ft`/d = feet squared per day
7.d=day
8. Sy = specific yield
9. ft = feet
10. Hlimit defines the pumping water level maintained in the dewatering well and is assumed to be held 5 feet above the bottom of the well screen
11. For the "Dewatering Well Depth" the depth to the bottom of the well screen was decreased or increased by ten feet but no change was made to the depth to the top of the well screen
Page 1 of 1

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station
APPENDIX A
BORING LOGS
synterracorp.com

PROJECT: Allen Steam Station
WELL / BORING NO: SSLF-PZ-01
PROJECT NO: 1026.17
STARTED: 5/19/22 COMPLETED: 5/19/22
DRILLING COMPANY: Geologic Exploration
NORTHING: 524031.27 EASTING: 1399444.01
DRILLING METHOD: Hollow Stem Augers
G.S. ELEV: 642.70 ft M.P. ELEV: 645.56 ft
BOREHOLE DIAMETER: 8 IN
DEPTH TO WATER: 19 ft TOC TOTAL DEPTH: 52.0 ft BGS
NOTES: bgs: below ground surface
LOGGED BY: G. Khang CHECKED BY: M. Crai
2
w
U
=
U)
LLI
�
OUo
2
d
a
<O
?
DESCRIPTION
Q
w
2
WELL
o
U)
of
ii
CONSTRUCTION
Silty CLAY w/ minimal sand; orange, fine, dry, loose,
nonplastic, slightly micaceous
Light brown w/ depth
5
Clayey SILT w/ minor sand; brown, fine, dry, loose,
10
nonplastic, slightly micaceous
-AquaGuard Grout (0-20 ft
bgs)
15
-2-in PVC Riser
Q
Silty CLAY; fine, slightly moist to moist w/ depth,
20
slightly cohesive, weak to nonplastic
-Bentonite Holeplug Seal
(20-25 ft bgs)
Light brown w/ minor sand
25
Increased sand
30
35
-Sand Filter Pack (25-52 ft
Continued moist, cohesive, weak to nonplastic cuttings
bgs)
40
Well Screen (27-52 ft bgs
Saturated cuttings; mud slurry returned to surface
Increased sand
45
CLIENT: Duke Energy Carolinas
SynTerra
148 River Street, Suite 220 PROJECT LOCATION: Gaston County, North Carolina
Ter Greenville, South Carolina 29601
Phone:[phone] PAGE 1 OF 2

PROJECT: Allen Steam Station
WELL / BORING NO: SSLF-PZ-01
PROJECT NO: 1026.17
STARTED: 5/19/22 COMPLETED: 5/19/22
DRILLING COMPANY: Geologic Exploration
NORTHING: 524031.27 EASTING: 1399444.01
DRILLING METHOD: Hollow Stem Augers
G.S. ELEV: 642.70 ft M.P. ELEV: 645.56 ft
BOREHOLE DIAMETER: 8 IN
DEPTH TO WATER: 19 ft TOC TOTAL DEPTH: 52.0 ft BGS
NOTES: bgs: below ground surface
LOGGED BY: G. Khang CHECKED BY: M. Crai
2
U
=
U)
LLI
-i
OUo
2
d
w
<O
?
DESCRIPTION
Q
w
a
2
WELL
o
U)
of
ii
CONSTRUCTION
SAA - silty CLAY w/ sand
Boring terminated at 52 ft bgs
55
60
65
70
75
80
85
90
95
CLIENT: Duke Energy Carolinas
SynTerra
148 River Street, Suite 220 PROJECT LOCATION: Gaston County, North Carolina
Terra Greenville, South Carolina 29601
s)mPhone:864-421-9999 PAGE 2 OF 2

PROJECT: Allen Steam Station
WELL / BORING NO: SSLF-PZ-02
PROJECT NO: 1026.17
STARTED: 5/18/22 COMPLETED: 5/18/22
DRILLING COMPANY: Geologic Exploration
NORTHING: 523991.93 EASTING: 1400031.62
DRILLING METHOD: Hollow Stem Augers
G.S. ELEV: 616.87 ft M.P. ELEV: 619.74 ft
BOREHOLE DIAMETER: 8 IN
DEPTH TO WATER: 10 ft TOC TOTAL DEPTH: 28.0 ft BGS
NOTES: bgs: below ground surface
LOGGED BY: G. Khang CHECKED BY: M. Crai
2
w
U
=
U)
LLI
_
OUo
2
d
a
<O
?
DESCRIPTION
Q
w
2
WELL
o
U)
of
ii
CONSTRUCTION
CLAY; red, dry, fine
e°-AquaGuard Grout (0-5 ft
bgs)
CLAY w/ minor silt and sand; dry to slightly moist, weak
5
plasticity, slightly cohesive
Brown and red at 5 ft bgs, brown w/ depth and clumpy
cuttings
-2-in PVC Riser
-Bentonite Holeplug Seal
Slightly micaceous
(5-10 ft bgs)
to -
Driller noted water during drilling at —10 ft bgs
Light brown and slightly orange cuttings; decreased
cohesiveness and plasticity
15
`= f -Sand Filter Pack (10-28 ft
20
Light orange brown to light orange
bgs)
Minor rock pieces and gravel in cuttings
-Well Screen (13-28 ft bgs
Increased moisture
25
Boring terminated at 28 ft bgs
30
35
40
45
CLIENT: Duke Energy Carolinas
SynTerra
148 River Street, Suite 220 PROJECT LOCATION: Gaston County, North Carolina
Terra Greenville, South Carolina 29601
s)mPhone:864-421-9999 PAGE 1 OF 1

PROJECT: Allen Steam Station
WELL / BORING NO: SSLF-PZ-03
PROJECT NO: 1026.17
STARTED: 5/19/22 COMPLETED: 5/19/22
DRILLING COMPANY: Geologic Exploration
NORTHING: 523550.59 EASTING: 1399901.63
DRILLING METHOD: Hollow Stem Augers
G.S. ELEV: 606.93 ft M.P. ELEV: 609.76 ft
BOREHOLE DIAMETER: 8 IN
DEPTH TO WATER: 19 ft TOC TOTAL DEPTH: 29.0 ft BGS
NOTES: bgs: below ground surface
LOGGED BY: G. Khang CHECKED BY: M. Crai
2
w
U
=
U)
LLI
�
OUo
2
d
a
<O
?
DESCRIPTION
Q
w
2
WELL
o
U)
of
ii
CONSTRUCTION
Silt clay LOAM; brown, dry, fine, loose, soft
CLAY w/ minor silt; dry to slightly moist, slightly
5
cohesive, weak plasticity
Red w/ depth
e°-AquaGuard Grout (0 12 ft
bgs)
Dark red, loose, nonplastic, dry
Red to orange red w/ depth
10
-2-in PVC Riser
Brown orange w/ depth
f-Bentonite Holeplug Seal
15
(12-17 ft bgs)
Q
Clayey SILT w/ minor sand; fine, loose, dry to slightly
20
moist, light orange brown
`•� -Sand Filter Pack (17-29 ft
Increased sand at -24 ft bgs; light brown and moist
\ bgs)
Well Screen (19 29 ft bgs
25
Fine, cohesive, clumpy, weak plasticity, moist to
saturated
Boring terminated at 29 ft bgs
30
35
40
45
CLIENT: Duke Energy Carolinas
SynTerra
148 River Street, Suite 220 PROJECT LOCATION: Gaston County, North Carolina
Terra Greenville, South Carolina 29601
s)mPhone:864-421-9999 PAGE 1 OF 1

PROJECT: Allen Steam Station
WELL / BORING NO: SSLF-PZ-04
PROJECT NO: 1026.17
STARTED: 5/19/22 COMPLETED: 5/19/22
DRILLING COMPANY: Geologic Exploration
NORTHING: 523561.42 EASTING: 1398990.72
DRILLING METHOD: Hollow Stem Augers
G.S. ELEV: 642.54 ft M.P. ELEV: 645.35 ft
BOREHOLE DIAMETER: 8 IN
DEPTH TO WATER: 14 ft TOC TOTAL DEPTH: 43.0 ft BGS
NOTES: bgs: below ground surface
LOGGED BY: G. Khang CHECKED BY: M. Crai
2
w
U
=
U)
LLI
_
OUo
2
d
a
<O
?
DESCRIPTION
Q
w
2
WELL
o
U)
o
ii
CONSTRUCTION
Brown at surface w/ organics
Silty CLAY; red, fine, loose, dry, nonplastic
5
e°-AquaGuard Grout (0-15 ft
Pale pink red, soft, dry to slightly moist, slightly
bgs)
micaceous
10
Minor sand
-2-in PVC Riser
Light orange to orange brown, increased moisture,
SZ
weak to nonplastic, slightly cohesive
15
f-Bentonite Holeplug Seal
(15-20 ft bgs)
Brown, moist, clumpy cuttings
20
Light brown
25
30
•'• -Sand Filter Pack (20-43 ft
bgs)
-Well Screen (23-43 ft bgs
35
40
Boring terminated at 43 ft bgs
45
CLIENT: Duke Energy Carolinas
SynTerra
148 River Street, Suite 220 PROJECT LOCATION: Gaston County, North Carolina
Ter Greenville, South Carolina 29601
Phone:[phone] PAGE 1 OF 1

Groundwater Modeling to Support Vertical Separation — South Starter Landfill 3620-INDUS July 11, 2023
Duke Energy Carolinas, LLC, Allen Steam Station
APPENDIX B
CALIBRATION HYDROGRAPHS
synterracorp.com

578
y 576
m
574
0 572
+1
570
m W 568
am 566
3 564
c 562
0 560
L7
558
1�
■
Q1c� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
--w AB-10BR: Modeled +AB-10BR: Observed
579
y 577
m
575
0 573
+1
571
W 569
m 567
565
M
c 563
0 561
C7
559
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
AB-10BRL: Modeled +AB-10BRL: Observed
AB-105
577
577
y
575
y
575
573
573
-
0
571
2
571
- -
569
569
- -
W
567
w
567
m
565
m
565
— —
3
563
3
563
— -
c
561
—
c
561
0
559
0
559
L7
557
557
O O �� �� �� 1.115C7
O O �� �� �� 1.11)
01� Q1�
y�L '1'�L
QUQUO�O�> OOOOy
01� 01� QUQUQ�� O�y OOOOy
y�L '1',�L
'1',y�L
y
y'�L 1',y�L �'ti�ti 11��'L y,��ti �,3�ti �,L�l 1,4T
y'�L �'ti�ti 1'ti�L y,��ti 1,�'(L �,L�L 114T
y
Date
Date
--m AB-10D: Modeled CAB-10D: Observed
- A13-10S: Modeled CAB-10S: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-1
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

620
y 618
m
616
0 614
+1
612
m W 610
d 608
3 606
c 604
0 602
L7
600
1�
AB-11D
1c� QLO Qti0 Q�1 0�1 O''-V Owi, O'L� O1L115
Date
--m AB-11D: Modeled +AB-11D: Observed
A B-21 D
AB-21BRL
644
y 642
m
r 640
0 638
+1
636
m
W 634
m 632
3 630
M
c 628
0 626
C7
624
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
AB-21BRL: Modeled +AB-21BRL: Observed
AB-21S
644
645
y
642
y
643
640
641
-
0
638
- - -
0
639
- - - - -
71
636
- - -
637
- - - - —
W
634
- -
w
635
—
am
632
am
633
+�
3
630
- - - -
m
631
— — — — —
c
628
- - - -
M
c
629
—
0
626
F625
0
627
L7
C7
624
(3 Q1�
y�L
QUO QUO O�� O�� O�� O�� O�� O��
01� 01� QUO QUO Q�� O�y O�V O�� O�� Oy
y�L '1',�L
y IN
y'�L 1',y�L �'ti�ti 11'L y,��ti �,3�ti �,L�l 1,��ti
y'�L
y
Date
Date
--m AB-21D: Modeled CAB-21D: Observed
- A13-21S: Modeled CAB-21S: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-2
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I—
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

645
y 643
m
641
0 639
+1
637
m W 635
am 633
3 631
c 629
0 627
L7
625
1�
AB-21SL
Q1c� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
--w AB-21SL: Modeled CAB-21SL: Observed
AB-21SS
644
y 642
m
r 640
0 638
+1
636
m W 634
m 632
3 630
M
c 628
0 626
C7
624
Qua Qti° Qti° Qtiti otiti Q'�� oti� Otis' i ti-
��
Date
CAB-21SS: Modeled fAB-21SS: Observed
AB-22BRL
600
i
604
y
598
-
602
596
- _ _
Y
600
-
0
594
_ —
598
-
596
— —
592
i — -
>
594
—
W
590
- -
W
592
— — — —
am
588
- -
y
590
— — —
3
586
I
3
588
— -
-a
584
M
586
- -
584
582
0
582
L7
C7
580
580
1.115
01� Q1c�
QUO QUO O�� O�� O�� Owi, O�� O��
01� 01c� QUO QUO Q�� O�y O�V O�� O�� Oy
'1',�L
y'�L 1',y�L �'ti�ti 11��'L y,��ti �,3�ti �,L�l 1,��ti
yy�L y'�L
Date
Date
AB-22BR: Modeled CAB-22BR: Observed
AB-22BRL: Modeled CAB-22BRL: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-3
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

boa
y 598
m
�. 596
0 594
592
m W 590
am 588
3 586
c 584
0 582
V
58a
1�
AB-22D
1� QL° Qti0 Q�1 0�1 O''-V Owi, O'L� O1L115
Date
--m AB-22D: Modeled +AB-22D: Observed
AB-22S
AB-23BRU
640
1
635
c
630
m
7
m
W 625
m
m 620
3
M
615
0
'L^
V
610
Qti° Qti° Qtiti otiti o'�� oti� oti�' oti�'
Date
AB-23BRU: Modeled +AB-23BRU: Observed
AB-23S
598
642
y
596
y
640
594
I
638
0
592
-
0
636
- - - -
590
634
- -
iy
588
iy
632
am
586
-
am
630
— —
+�
3
584
3
628
— —
3
582
- —
M
r-
626
—
0
580
-��
-
0
624
L7
C7
578
622
1.115
�
01� Q1�
'L
Q�° Q�° O�� O�� O�� O�� O�� Oy
'L 'L'L`l
0101� Q�° Q�° Q�� O�y O�� O��
Date
Date
--1111 A13-22S: Modeled fAB-22S: Observed
- A13-23S: Modeled CAB-23S: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-4
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

637
y 635
m
�. 633
0 631
629
m W 627
am 625
+�
3 623
c 621
0 619
L7
617
1�
Q1c� Q�° Qti° Qti1 O�y O'-V Owi, Otis 0.1"5
Date
AB-24BR: Modeled +AB-24BR: Observed
638
y 636
m
r 634
0 632
630
m W 628
m 626
3 624
M
c 622
0 620
C7
618
010) '1��•L13
AB-24S
C3 ci Qtiti otiti atiti °titi oti'' i ti3
ti��� ��
Date
A13-24S: Modeled fAB-24S: Observed
AB-24SL
637
638
1-1635
y
636
633
634
0
631
0
632
- -
629
630
- - -
iy
627
iy
628
-
m
a)
625
am
626
~
623
I
+�
:
624
c
621
—
Ir
622
-
0
619
—
0
620
L7
C7
617
618
ri
01� Q1c�
Q�° Q�° O�� O�� O�� Owi, O�� O��
01� 01c�
C3 Q�° Q�� O�y O�V O�� O�� Oy
'1',�L
y'�L 1',y�L �'ti�ti 11��'L y,��ti �,3�ti �,L�l 1,��ti
yy�L y'�L
Date
Date
--m AB-24D: Modeled CAB-24D: Observed
- AB-24SL: Modeled CAB-24SL: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-5
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

640
17
635
—
c
630
m
m
W
625
L
3
620
615
0
L7
610
010 Q1� QUO QUO OS� O�� qz � Oy Oy Oy
ti���
Date
--w AB-25BR: Modeled +AB-25BR: Observed
AB-25S
AB-25BRU
640
I
635
-
—
c
630
m
7
m
W 625
L
3 620
M
615
o
C7
{
610
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
AB-25BRU: Modeled +AB-25BRU: Observed
AB-25SL
640
640
635
635
-
c
630
c
630
- -
X�411�
7
W
625
w
625
- -
m
m
m
620
m
620
-
3
3
M
615
—
615
0
0
V
V
610
610
01� Q1c�
QUO QUO O�� O�� O'-V Owi, O"05 O�115
01 01c� QUO QUO Q�� O�y O"V Owi,
Date
Date
--1111 A13-25S: Modeled CAB-25S: Observed
- AB-25SL: Modeled CAB-25SL: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-6
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I—
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

640
635
c
636
m
m W 625
L
620
3
615
0
rL^
V
61d
1�
AB-25SS
Q1c� Q�° Qti° ati1 O�y O'-V Owi, Otis a.1"5
Date
--a'- AB-25SS: Modeled +AB-25SS: Observed
605
600
-
c
595
-
m
7
W 590
L
585
3
580
0
'L^
V
575
Qti° Qti° atiti otiti atiti atiti oti'' i ti3
��
Date
AB-26D: Modeled fAB-26D: Observed
AB-25S
AB-5
605
647
y
y
645
600
643
595
0
641
7
7
639
W
590
- - -
W
637
m
m
635
3
585
- - -
3
633
580
M
631
0
0
629
L7
C7
575
627
01� Q1c�
Q�° Q�° O�� O�� O�� Owi, O�� O��
01� 01c� Q�° Q�° Q�� O�y O�V O�� O�� ay
'1',�L
y'�L 1',y�L �'ti�ti 11��'L y,��ti �,3�ti �,L�l 1,��ti
yy�L y'�L
Date
Date
--1111 A13-26S: Modeled CAB-26S: Observed
A13-5: Modeled CAB-5: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-7
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

581
y 579
m
�. 577
0 575
573
m W 571
am 569
3 567
c 565
0 563
L7
561
01� Q1
a Qyo Qyo Qy� oy� o'ti oti, oti3 o1.3
Date
CAB-6A: Modeled fAB-6A:Observed
ABLF-PZ-1
640
m
m
!t, 635
c
0
630
m
W
`m
625
r
m
3
620
�
0
C7
615
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
ABLF-P2-1: Modeled tABLF-P2-1: Observed
CCR-16D
582
i i
582
y
580
— —
y
580
578
-
- -
578
0
576
-
- -
0
576
-
+1
574
-
+�
574
- - - -
W
572
mom
W
572
-
am
570
-
-
m
570
568
-
-
568
—
c
566
- - -
c
566
—
0
564
0
564
L7
C7
562
562
1.115
01� Q1c�
QUO QUO O�� O�� O�� Owi, O�� O��
01� 01c� QUO QUO Q�� O�y O�V O�� O�� Oy
'1',�L
y'�L 1',y�L �'ti�ti 11��'L y,��ti �,3�ti �,L�l 1,��ti
yy�L y'�L
Date
Date
A13-6R: Modeled CAB-6R: Observed
— CCR-16D: Modeled CCR-16D: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-8
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I—
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

581
y 579
m
577
0 575
+1
573
m W 571
am 569
3 567
c 565
0 563
L7
561
1�
CCR-16S
Q1c� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
CCR-16S: Modeled +CCR-16S: Observed
CCR-17S
590
y 588
m
�. 586
0 584
+1
582
W 580
m 578
576
M
c 574
0 572
C7
570
1�
0
CCR-17 D
Q
'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
f CCR-17D: Modeled fCCR-17D: Observed
CCR-18D
586 583
y 584 y 581
582 — 579
0 580 — - 2 577
578 - - 575
W 576 w 573
am 574 m 571
3 572 - �* 3 569
c 570 - — c 567
0 568 0 565
L7 C7
566 563
01� Q1c� QUO QUO O�� O�� O�� Obi, O�� O�� 01� 01c� QUO QUO Q�� O�y O"V Owi, Orb O1.115
Date Date
--a'-CCR-17S: Modeled CCR-17S: Observed — CCR-18D: Modeled CCR-18D: Observed
(' DUKE DRAWN BY: J. EBENHACK DATE: 03/09/2023 FIGURE B-9
ENERGY- REVISED BY: DATE: 03/09/2023 HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS CHECKED BY: R. YU DATE: 03/10/2023 IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023 GROUNDWATER MODELING TO SUPPORT VERTICAL SEPARATION -
�� PROJECT MANAGER: C. SUTTELL SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
synTerra www.synterracorp.com GASTON COUNTY, NORTH CAROLINA
I- I

580
y 578
m
576
0 574
+1
572
m W 570
am 568
3 566
c 564
0 562
L7
560
1�
CCR-18S
Q1c� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
CCR-18S: Modeled +CCR-18S: Observed
CCR-20S
CCR-20D
613
y 611
-
m
r 609
0 607
+1
605
m
W 603
m 601
599
M
c 597
0 595
C7
593
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
f CCR-20D: Modeled fCCR-20D: Observed
CCR-21 D
612
633
-
y
610
y
631
608
629
0
606
-
0
627
T-
-
604
-
625
- -
iy
602
iy
623
a)
600
d
621
598
619
- —
c
596
—
c
617
—
0
594
0
615
L7
C7
592
613
1.115
01� Q1c�
QUO QUO O�� O�� O"V Owi, O�� O��
01� 01c� QUO QUO Q�� O�y O�V O�� O�� Oy
'1',�L
y'�L 1',y�L �'ti�ti 11��'L y,��ti �,3�ti �,L�l 1,��ti
yy�L y'�L
Date
Date
--a'- CCR-20S: Modeled CCR-20S: Observed
— CCR-21D: Modeled CCR-21D: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-10
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I—
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

635
y 633
m
631
0 629
+1
627
m W 625
am 623
3 621
c 619
0 617
L7
615
1�
CCR-21S
Q1c� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
CCR-21S: Modeled +CCR-21S: Observed
CCR-22S
CCR-22 DA
635
y 633
m
r 631
0 629
+1
627
- -
m
W 625
m 623
3 621
—
M
c 619
0 617
C7
615
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
CCR-22DA: Modeled CCR-22DA: Observed
CCR-23D
638
639
y
636
y
637
m
634
m
r
635
0
632
—
2
633
�
636
631
iy
628
iy
629
am
626
m
627
3
624
�
3
625
c
622
—
c
623
0
620
0
621
L7
C7
618
619
01� Q1c�
QUO QUO O�� O�� O�� Obi, O�� O��
01� 01c� QUO QUO Q�� O�y O"V Owi, Orb O1.115
Date
Date
CCR-22S: Modeled CCR-22S: Observed
— CCR-23D: Modeled CCR-23D: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-11
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

636
y 636
m
634
0 632
+1
630
m W 628
am 626
3 624
622
0 620
L7
618
1�
CCR-23S
Q1c� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
CCR-23S: Modeled +CCR-23S: Observed
GWA-1D
GWA-1BR
622
y 620
m
r 618
0 616
614
m W 612
m 610
3 608
—
M
c 606
—
0 604
C7
602
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
Date
GWA-113R: Modeled GWA-1BR: Observed
GWA-1S
623
623
y
621
y
621
619
619
-
0
617
-
0
617
- -
41
615
- -
+�
615
-
W
613
- -
W
613
—
am
611
-
m
611
—
3
609
3
609
- ■=■
c
607
— - — —
M
c
607
0
605
0
605
L7
C7
603
603
01� Q1c�
QUO QUO O�� O�� O�� Obi, O�� O��
01� 01c� QUO QUO Q�� O�y O"V Owi, Orb O1.115
Date
Date
--'I-
GWA-10: Modeled tGWA-10: Observed
— —GWA-1S: Modeled GWA-1S: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-12
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

584
y 582
m
580
0 578
+1
576
m W 574
am 572
3 570
c 568
0 566
L7
564
1�
GWA-2D
Q1� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
GWA-2D: Modeled tGWA-2D: Observed
GWA-3BRA
581
y 579
m
577
0 575
41
m 573
W 571
m 569
567
M
c 565
0 563
C7
561
10)
0
GWA-2S
Q'�a Qti° Qti° Qtiti otiti Q'��' oti�" Otis' Qti�'
N,��
Date
f GWA-2S: Modeled fGWA-2S: Observed
GWA-3D
583 —
581
y
581
y
579
579
577
0
577
-
2
575
-
+1
575
-
+j
573
W
573
w
571
m
571
m
569
3
569
3
567
- -
c
567
—
M
c
565
0
565
0
563
L7
C7
563
561
�
O O ��
� O O �
01� Q1
QUQUO�� O�� O�� OO�� O��
01� 01QUQUQ�� O�y O� O�� O�� Oy
'1',�L
y'�L 1',y�L �'ti�ti 11��'L y,��ti �,3�ti �,L�l 1,��ti
yy�L y'�L
Date
Date
�
GWA-3BRA: Modeled GWA-3BRA: Observed
— GWA-3D: Modeled GWA-3D: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-13
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

GWA-3S
582
y
580
-
m
578
-
0
576
— -
+1
574
a
-
m
W
572
-
am
570
— —
3
568
— - -
c
566
- -
0 564
L7
562
01� Q1c� Q�° Q�° O�� O�� O�� Owi,
Date
GWA-3S: Modeled +GWA-3S: Observed
LB-PZ-2
640
y 638
m
r. 636
Osman
0 634
+1
632
m
m
W 630
m 628
3 626
M
c 624
0 622
C7
620
010) '1��•L13
LB-PZ-1
Qti° Qti° Qtiti otiti atiti °titi oti'' i ti3
ti�����
Date
--E-- LB-PZ-1: Modeled f LB-PZ-1: Observed
LB-PZ-3
640
645
y
638
y
643
636
641
0
634
0
639
- - -
41
632
+�
637
- —
W
630
-
W
635
am
628
- -
am
633
-
—
3
626
- -
3
631
-
c
624
-
M
c
629
—
0
622
0
627
L7
C7
620
625
)
01� Q1c�
Q�° Q�° O�� O�� O�� Obi, O�� O��
01� 01c� Q�° Q�° Q�� O�y O"V Owi, O11 O1.115
Date
Date
--m LB-PZ-2: Modeled --0-- LB-PZ-2: Observed
- LB-PZ-3: Modeled LB-PZ-3: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-14
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I—
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA

631
y 629
m
627
0 625
+1
623
m W 621
am 619
3 617
c 615
613
L7
611
1�
,yQ
SSLF-PZ-1
Q1c� QUO QtiO Qti1 O�y O'-V Owi, Otis 0.1"5
Date
SSLF-P2-1: Modeled SSLF-P2-1: Observed
SSLF-PZ-3
SSLF-PZ-2
612
y 610
m
r 608
0 606
+1
604
m
W 602
m 600
598
M
c 596
594
C7
592
Q'�a Qti° Qti° Qtiti otiti o'��' oti�" oti�' Qti�'
Date
SSLF-P2-2: Modeled +SSLF-P2-2: Observed
SSLF-PZ-4
605
629
y
603
y
627
601
625
0
599
0
623
+1
m
597
+�
621
W
595
anw
619
�■y.
am
593
m
617
3
591
3
615
c
589
c
613
587
.......
------
611
C7
C7
585
609
`!
O?g Q1�
Qti0 Q1O Qn1 0�1 O'}0 O'L� O13 q
01 01� Qyo Qti0 Q�1 O1, o'ti O1� O'L� OLD
y'�L
Date
Date
-
SSLF-P2-3: Modeled (SSLF-P2-3: Observed
SSLF-P2-4: Modeled SSLF-P2-4: Observed
(' DUKE
DRAWN BY: J. EBENHACK DATE: 03/09/2023
FIGURE B-15
ENERGY-
REVISED BY: DATE: 03/09/2023
HYDROGRAPH OF COMPUTED VS OBSERVED HYDRAULIC HEADS
CAROLINAS
CHECKED BY: R. YU DATE: 03/10/2023
IN CALIBRATION MONITORING WELLS AND PIEZOMETERS
APPROVED BY: C. SUTTELL DATE: 03/15/2023
GROUNDWATER
MODELING TO SUPPORT VERTICAL SEPARATION -
��
PROJECT MANAGER: C. SUTTELL
SOUTH STARTER LANDFILL 3620-INDUS
ALLEN STEAM STATION
I-
synTerra
www.synterracorp.com
I
GASTON COUNTY, NORTH CAROLINA