1812_2025 Q2 ILF Groundwater Conditions Report_w cvr ltr_8-1-2025

(� DUKE
ENERGY
August 1, 2025
North Carolina Department of Environmental Quality
Division of Waste Management
Solid Waste Section
2090 U.S. Highway 70
Swannanoa, NC 28778
Attn: Ms. Sarah Moutos (submitted electronically)
Re: Groundwater Condition Quarterly Report — April 2025 through June 2025
Industrial Landfill No.1
Permit No.: 1812-INDUS-2008
Marshall Steam Station
Terrell, North Carolina 28682
Dear Ms. Moutos:
525 S. Tryon St.
Charlotte NC, 28202
In accordance with the NCDEQ DWM September 17, 2021, Phase 2 Permit Modification Approval letter (FID
1609547), Duke Energy is providing the quarterly report describing groundwater conditions in the area of the
Marshall Steam Station Industrial Landfill No.1 (ILF, 1812-INDUS-2008) Phases 2, 3, 4, and 5 Expansion
(Future Phases). The report is for the quarterly period of January 2025 through March 2025 (Q1 2025).
The quarterly report includes an analysis of groundwater levels and underdrain pump flowrates within Phases
2, 3, 4 and 5 Expansion, with an updated water level map, hydrographs, pump flowrate plot, and well
construction and water level data tables. An evaluation of groundwater levels and pump flowrates compared
to model predictions is included. Groundwater transducer data, groundwater model trend data, and underdrain
pumping data are provided in an excel file format as the report Appendices.
Groundwater conditions in the vicinity of Marshall Steam Station's Industrial Landfill No.1 continue to be
monitored and evaluated. The next quarterly report (Q2 2025) will be submitted by November 1, 2025.
If you need additional information regarding this submittal do not hesitate to email or call me at
Anne.Davin(cDduke-energy.com or [phone].
Respectfully submitted,
9�v� A>,��
Anne Davin, E.I.
Environmental Services
Attachments: Industrial Landfill No.1 (1812-INDUS-2008) Groundwater Conditions Quarterly Report — April
2025 through June 2025 (SynTerra; July 2025)
Appendices in excel format:
1) Appendix A Water Level Monitoring Data Files
2) Appendix B Groundwater Model Predicted Trend File
3) Appendix C Underdrain Pumping Data File
4) Appendix D Mann -Kendall Results
cc (via e-mail): Deana Yitbarek, NCDEQ
www.duke-energy.com Page 1 of 2

Elizabeth Werner, NCDEQ
Sherri Stanley, NCDEQ
Scott Saunders, Duke Energy
Dan Zakary, Duke Energy
Jake Muessen, Duke Energy
Ashley Healy, Duke Energy
Tyler Hardin, Duke Energy
Ed Sullivan, Duke Energy
Thomas Colton, SynTerra
www.duke-energy.com Page 2 of 2

41P
synTerra
Science & Engineering Consultants
synterracorp.com
GROUNDWATER CONDITIONS QUARTERLY REPORT —
APRIL 2025 TO JUNE 2025
INDUSTRIAL LANDFILL NO. 1
PERMIT NO. 1812-INDUS-2008)
FOR
MARSHALL STEAM STATION
8320 EAST CAROLINA HIGHWAY 150
TERRELL, NC 28682
JULY 31, 2025
PREPARED FOR
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N`ca'RD,,,,, `� ENERGY.:
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056667
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G. Thomas Colton, NC P.E. No. 056667 Trevor Ludwick
Associate Engineer/Project Manager Project Scientist
Scott A. Spinner, NC L.G.
Senior Peer Reviewer

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
ILl 1RX919141910Ill I I►kM
PAGE
1.0 INTRODUCTION........................................................................................................ 1-1
1.1 Objectives and Purpose...............................................................................................1-1
1.2 Key Findings.................................................................................................................1-1
2.0 QUARTERLY MONITORING RESULTS......................................................................... 2-1
2.1 Current Groundwater Conditions................................................................................ 2-1
2.2 Groundwater Trends.................................................................................................... 2-1
2.2.1 Groundwater Level Hydrographs and Model Trends ............................................ 2-1
2.3 Underdrain Pump Performance...................................................................................2-3
3.0 QUARTERLY WATER -LEVEL REDUCTION ACTIVITIES ................................................... 3-1
4.0 REFERENCES.............................................................................................................4-1
July 2025 Page i
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
LIST OF FIGURES
Figure 1 Site Location Map
Figure 2 Monitoring Locations
Figure 3 Groundwater Elevations — Upper Flow Zone (July 2025)
Figure 4A Upgradient of Phase 2 Expansion (ILF-2S/D and MW-4/D)
Figure 413 Upgradient of Phase 2 Expansion (GWA-4S/D and CLF21-10)
Figure 4C Within Phase 2 Expansion (CLF-UD and CLF21-11)
Figure 4D Within Phase 2 Expansion (CLF21-12 and CLF21-13/13R)
Figure 4E Within Phase 2 Expansion (CLF21-14/14R and CLF21-15)
Figure 4F Downgradient of the Phase 2 Expansion (CLF-402 and CLF-408)
Figure 4G Downgradient of the Phase 2 Expansion (CLF22-306/306R and CLF22-307/307R)
Figure 4H Southwest of the Future Phase 5 Expansion (CLF24-501 and CLF24-502)
Figure 41 West of the Future Phase 5 Expansion (CLF24-503 and CLF24-504)
Figure 4J West of the Phase 2 Expansion (CLF24-505)
Figure 5 Cell 5 (Underdrain) Pumping Flow Rate vs. Simulated Flow Rate
LIST OF TABLES
Table 1 Groundwater Monitoring Network Well Information and Water Levels
LIST OF APPENDICES
Appendix A
Water -Level Monitoring Data Files
Appendix B
Groundwater Model Predicted Trend File
Appendix C
Underdrain Pumping Data Files
Appendix D
Mann -Kendall Data
July 2025
Page H
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
II&10]y_[4l:%]►1iLTI1.7_1►U7_13 3:1VAF-A00 L11.1
Duke Energy Duke Energy Carolinas, LLC
DWM Division of Waste Management
Future Phases ILF Phases 3, 4, and 5 expansion
gpm gallons per minute
ILF Industrial Landfill (Permit No. 1812-INDUS-2008)
NCDEQ North Carolina Department of Environmental Quality
reporting period second quarter 2025 (April 2025 to June 2025)
Site Marshall Steam Station
July 2025
Page Hi
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
1.0 INTRODUCTION
1.1 Objectives and Purpose
SynTerra prepared this Groundwater Conditions Quarterly Report (report) on behalf of Duke
Energy Carolinas, LLC (Duke Energy) to document the groundwater -level monitoring data and
underdrain pumping records in the vicinity of the Industrial Landfill No.1 (ILF) (Permit No. 1812-
INDUS-2008) at the Marshall Steam Station (Site; Figure 1). This report is prepared in response
to condition #3 in the North Carolina Department of Environmental Quality (NCDEQ) Division of
Waste Management (DWM) September 17, 2021, Phase 2 Permit Modification Approval letter
(FID 1609547).
Data collected during the second quarter of 2025 [April 2025 to June 2025 (reporting period)]
were used to evaluate groundwater conditions for the ILF Phase 2 expansion (includes Cell 5
and Cell 6) and ILF Future Phases 3, 4, and 5 expansion (Future Phases). Groundwater levels are
monitored at 21 piezometers and monitoring wells and the ILF underdrain. Specifically, this
report evaluates the groundwater levels, underdrain pumping flow rates, and efforts to
expedite reducing and maintaining groundwater levels near the ILF during the reporting period.
1.2 Key Findings
Key findings of the evaluation conducted during this reporting period include:
• Groundwater levels in the vicinity of the ILF are stable or have decreased since
monitoring began in July 2021.
• During the reporting period, groundwater levels were stable or decreased at 19 of the
21 monitoring locations. Groundwater levels increased at CLF23-408 and CLF24-501;
those locations are in the southern extent of ILF Future Phases 4 and 5.
• Monitoring locations where groundwater levels are greater than model predictions may
be attributed to increased precipitation in the area or to a slower basin excavation rate
than assumed in the model. Additionally, neither the original model calibration nor the
2024 update include the new ILF Phase 5 piezometers.
• The Cell 5 underdrain pump has been operational for 46 months. During the reporting
period, the average pumping rate was approximately 7.8 gallons per minute (gpm), an
increase compared to that of the previous reporting period (7.1 gpm). While the flow
rates vary, the overall trends generally match the model predictions. The model
predicted the underdrain to become dry after approximately 19 months of operation;
however, the slower basin excavation rate has extended the period needed to operate
the underdrain.
July 2025
Page 1-1
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
2.0 QUARTERLY MONITORING RESULTS
2.1 Current Groundwater Conditions
The established network of temporary and long-term piezometers and groundwater wells for
monitoring groundwater elevations in the ILF Phase 2 expansion area is shown on Figure 2.
Piezometer and groundwater well construction information pertaining to the monitoring
network (including water levels and groundwater elevations) is provided in Table 1.
Depth to groundwater measurements were collected on July 1, 2025, for the upper (shallow)
flow zone and were used to generate a groundwater elevation map (Figure 3). Groundwater
elevations indicate:
0 Groundwater at the ILF area has an overall flow direction from north to south
(Figure 3).
Groundwater levels in wells and piezometers at the ILF are similar or have decreased
compared to groundwater levels during the first quarter of 2025.
• Underdrain operations in Cell 5 have maintained a cone of groundwater depression
around the Cell 5 blanket underdrain sump (CLF-UD; Figure 3).
2.2 Groundwater Trends
Transducers installed in groundwater monitoring wells, piezometers, and the Cell 5 underdrain (CLF-
UD) pump have been used to monitor water -level trends from as early as July 2021 through June 2025
(Figure 4A through Figure 4J). Key observations of those data include:
Groundwater level data collected from July 2021 (when monitoring started) through June
2025 were evaluated using Mann -Kendall analysis to determine water -level trends
(Appendix D). Statistically significant decreasing groundwater elevation trends were
observed in 16 of 21 monitored locations. Stable groundwater levels were observed at five
of 21 locations (CLF21-12, CLF24-502, CLF24-503, CLF24-504, and CLF24-505).
Decreasing or stable water level trends were observed in locations downgradient of the
Future Phases area during the reporting period, except for CLF23-408 and CLF24-501,
which are located in the southern extent of ILF Future Phases 4 and 5.
2.2.1 Groundwater Level Hydrographs and Model Trends
Pressure transducers are used to record high -resolution groundwater elevation data for
evaluation of groundwater conditions resulting from dewatering and excavation.
Transducer data are included in Appendix A. Manual water -level measurements and
transducer records were used to generate groundwater level hydrographs. Predicted
groundwater level trends from the transient groundwater models are included in those
hydrographs (Figure 4A through Figure 4J). The predicted transient groundwater level
trends exported from the models are provided in Appendix B.
July 2025 Page 2-1
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
Upgradient of the Phase 2 Expansion
Water levels upgradient of the Phase 2 expansion are generally stable. Water -level trends
at upgradient locations show overall decreasing trends from the start of monitoring (July
2021) through this reporting period. Information regarding the water -level trends during
the reporting period and overall monitoring period is provided below.
Location
ID
Flow
Zone
Reporting
Period Trend
Overall
Trend
Location
Plot
MW-4
Shallow
Stable
Decreasing
East of the ILF Phase 2 expansion
Figure 4A
MW-4D
Deep
Stable
Decreasing
East of the ILF Phase 2 expansion
Figure 4A
ILF-2S
Shallow
Stable
Decreasing
North of the ILF
Figure 4A
ILF-21)
Deep
Stable
Decreasing
North of the ILF
Figure 4A
GWA-4S
Shallow
Stable
Decreasing
West of the ILF Phase 2 expansion
Figure 4B
GWA-41)
Deep
Decreasing
Decreasing
West of the ILF Phase 2 expansion
Figure 4B
CLF21-10
Shallow
Stable
Decreasing
West of the ILF Phase 2 expansion
Figure 4B
Within the Phase 2 Expansion
A transducer, identified as CLF-UD (Figure 2), was installed to monitor the Cell 5
underdrain sump water level with the temporary pump operations while the landfill cell
was under construction. In October 2022, a permanent pump was installed; since then,
the water level has been recorded manually every week. The water levels within the
sump demonstrate that the underdrain continues to operate as intended, maintaining a
steady water level controlled by the pump settings (Figure 4C).
Perimeter of the Phase 2 Expansion, Outside of Cell 5 and Cell 6
Water levels at the perimeter of the Phase 2 expansion are decreasing or stable.
Information regarding the water -level trends during the reporting period and overall
monitoring period is provided below.
Location ID
Flow
Zone
Reporting
Period Trend
Overall
Trend
Location
Plot
CLF21-11
Shallow
Stable
Decreasing
West of Cell 5
Figure 4C
CLF21-12
Shallow
Stable
Stable
Southwest of Cell 5
Figure 4D
CLF21-13R
Shallow
Stable
Decreasing
South of Cell 5
Figure 4D
CLF21-14R
Shallow
Decreasing
Decreasing
East of Cell 6
Figure 4E
CLF21-15
Shallow
Decreasing
Decreasing
East of Cell 6
Figure 4E
CLF24-505
Shallow
Stable
Stable
West of Cell 5
Figure 4.1
Downgradient of the Phase 2 Expansion (Future Phases Area)
Water levels downgradient of the Phase 2 expansion are decreasing or stable, except for
CLF24-501 and CLF23-408. Water levels in three other locations also temporarily
July 2025 Page 2-2
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
increased during the reporting period (CLF24-502, CLF24-503, and CLF24-504). Those
locations are proximate to the dewatering rim ditch/sump in the Future Phases area. It
is possible that precipitation and water management in the dewatering ditches have
contributed to these increases. Information regarding the water -level trends for the
reporting period and the overall monitoring period is provided below.
Flow
Reporting
Overall
Location ID
Location
Plot
Zone
Period Trend
Trend
Within Future Phases 4 & 5
CLF-402
Shallow
Decreasing
Decreasing
Figure 4F
Expansion
Downgradient of the Future
CLF22-306
Shallow
Stable
Decreasing
Figure 4G
Phase 3 Expansion
Downgradient of the Future
CLF22-307
Shallow
Stable
Decreasing
Figure 4G
Phase 3 Expansion
CLF23-408
Shallow
Increasing
Decreasing
In the Future Phase 3 and 4
Figure 4F
CLF24-501
Shallow
Increasing
Decreasing
Southwest of Future Phase 5
Figure 4H
CLF24-502
Shallow
Stable
Stable
Southwest of Future Phase 5
Figure 4H
CLF24-503
Shallow
Stable
Stable
West of Future Phase 5
Figure 41
CLF24-504
Shallow
Stable
Stable
West of Future Phase 5
Figure 41
2.3 Underdrain Pump Performance
An underdrain pump is installed within the Phase 2 Cell 5 underdrain (CLF-UD) (Figure 2). The
underdrain pump removes groundwater from below the ILF Phase 2, Cell 5. The Phase 2 Cell 5
underdrain pump does not receive precipitation runoff; the underdrain is enclosed. Water
removed by the pump is discharged to the lower portion of the ash basin where it is ultimately
pumped through a water treatment system and discharged through a National Pollutant
Discharge Elimination System outfall. The Phase 2 Cell 5 underdrain pumping and model -
predicted pumping rates are shown on Figure 5.
The Phase 2 Cell 5 underdrain pump has been operational for 46 months. The average pumping
rate during the reporting period was 7.8 gpm. ILF Cell 5 pumping data, including the calculated
monthly total volume pumped and monthly average flow rate, are included in Appendix C.
Pumping operations for the Phase 2 Cell 5 underdrain have removed approximately 1 million
gallons of water during the reporting period. The Phase 2 Cell 5 underdrain pump had an
average flow rate of 7.8 gpm overall during the reporting period. Monthly average flow rates
during the reporting period were as follows:
• April 2025 — 7.2 gpm
• May 2025 — 7.3 gpm
• June 2025 — 8.9 gpm
July 2025
Page 2-3
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
3.0 QUARTERLY WATER -LEVEL REDUCTION ACTIVITIES
During the reporting period, Duke Energy conducted the following activities to expedite the
reduction of groundwater levels within the ILF Phase 2 expansion and the Future Phases:
• Phase 2, Cell 5:
o Continued underdrain operations, with an average flow rate of approximately
7.8 gpm.
o Continued Phase 2 Cell 5 operations.
• Phase 2, Cell 6:
o Continued Phase 2 Cell 6 operations, which began on October 9, 2023.
• Phase 3, Cell 7:
o Received the ILF Phase 3 Permit to Construct on December 29, 2023. The ILF
Phase 3 construction is anticipated to start by summer 2025 with preparation of
the landfill footprint with excavation and removal of ash underway.
o Submitted a permit modification to lower the base grades of ILF Phase 3 on July
3, 2024, that was approved by the NCDEQ DWM on July 12, 2024. Lowering the
base grades was made possible because of the decreasing water levels from
closure of the ash basin.
• Phase 4, Cell 8:
o Received a Permit to Construct on November 12, 2024. Construction of Phase 4
is expected to start in late 2025.
o Submitted a permit modification to lower base grades, increase the size of the
access road culvert, and revise the leachate force main alignment of the ILF
Phase 4 on January 28, 2025; NCDEQ DWM approved that modification on
March 4, 2025. Lowering the base grades was made possible because of the
decreasing water levels from closure of the ash basin.
• Future Phases:
o Continued passive dewatering and excavation of coal combustion residuals.
July 2025
Page 3-1
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
4.0 REFERENCES
SynTerra. (2021). Technical Memorandum: Modeling Support for the ILF Phase 2 Permit to
Construct Modification, Marshall Steam Station. October 5, 2021.
July 2025
Page 4-1
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
FIGURES
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FIGURE I
DUKE SITE LOCATION MAP
CATAWBA
t'® ENERGY COUNTY GROUNDWATER CONDITIONS QUARTERLY REPORT
wwsroH-sALEM APRIL 2025 THROUGH JUNE 2025
INAS INDUSTRIAL LANDFILL NO. 1 (PERMIT NO. 1812-INDUS-2008)
ASHEVILLEMARSHALL STEAM STATION
le CHARLOTTE TERRELL, NORTH CAROLINA
DRAWN BY. T KING DATE: 05/15/2019
REVISED BY L FOREMAN DATE 07/18/2025 1,000 0 1.000 2,000
CHECKED BY: T. COLTON DATE 07/18/2025
synTerra APPROVED BY T. COLTON DATE 07/18/2025 GRAPHIC SCALE (IN FEET)
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PROJECT MANAGER: T. COLTON
www-s nterracor .com
LEGEND
MW-6S WELL ID
765.80 GROUNDWATER ELEVATION (FEET, NAVD 88)
LONG-TERM PIEZOMETERAND/OR GROUNDWATER
MONITORING WELL
�e TEMPORARY PIEZOMETER
ie UNDERDRAIN PUMP
INFERRED GROUNDWATER ELEVATION CONTOUR (5'
INTERVAL)
GROUNDWATER FLOW DIRECTION
ASH BASIN WASTE BOUNDARY
- - - GEOGRAPHIC LIMITATION
STRUCTURAL FILL BOUNDARY
LANDFILL BOUNDARY
INDUSTRIAL LANDFILL #1 WASTE BOUNDARY
BOUNDARY BETWEEN LANDFILL PHASE 2, CELLS 5
AND 6
FUTURE LANDFILL PHASES
- - LANDFILL COMPLIANCE BOUNDARY
LEACHATE BASIN
DUKE ENERGY CAROLINAS PROPERTY LINE
TOPOGRAPHIC CONTOUR (10' INTERVAL)
NQi -�: STREAM (AMEC NRTR)
1. WATER LEVELS WERE COLLECTED ON 7/1/25.
2. ELEVATIONS ARE REFERENCED TO THE NORTH AMERICAN VERTICAL DATUM OF
1988 (NAVD 88).
3. THE STREAMS AND WETLANDS JURISDICTIONAL DETERMINATION WAS APPROVED
BY THE U.S. ARMY CORPS OF ENGINEERS ON OCTOBER 25, 2017 (SAW-2015-01412).
WETLANDS AND STREAMS BOUNDARIES WERE OBTAINED FROM AMEC FOSTER
WHEELER ENVIRONMENTAL AND INFRASTRUCTURE, INC. NATURAL RESOURCES
TECHNICAL REPORT (NRTR) DATED JUNE 2015.
4. THE TOPOGRAPHY IS SHOWN FOR REFERENCE PURPOSES ONLYAND SHOULD
NOT BE USED FOR DESIGN OR ENGINEERING PURPOSES. TOPOGRAPHY PROVIDED
BY TRANSASH.
5. PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY CAROLINAS.
6. BOUNDARIES ARE APPROXIMATE.
7. AERIAL IMAGERY IS A COMBINATION OF DUKE ENERGY PROPELLER AERIAL
PHOTOGRAPHY COLLECTED ON MARCH 26, 2025, AND MAXAR SATELLITE IMAGERY
OBTAINED FROM ESRI ONLINE, COLLECTED ON AUGUST 23, 2021.
8. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD 83).
9. NA- NOT AVAILABLE
FIGURE 3
GROUNDWATER ELEVATIONS - UPPER FLOW ZONE (JULY
2025)
GROUNDWATER CONDITIONS QUARTERLY REPORT
APRIL 2025 THROUGH JUNE 2025
INDUSTRIAL LANDFILL NO. 1 (PERMIT NO. 1812-INDUS-2008)
MARSHALL STEAM STATION
TERRELL, NORTH CAROLINA

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6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
ILF-2S - Total water level change from transducer installation on 07/30/2021 to 07/01/2025 is -1.2 feet.
MW-4 - Total water level change from transducer installation on 07/30/2021 to 07/01/2025 is -3.9 feet.
ILF-21) - Total water level change from transducer installation on 07/30/2021 to 07/01/2025 is -2.0 feet.
MW-4D - Total water level change from transducer installation on 07/30/2021 to 07/01/2025 is -4.4 feet.
ILF-2S/D
MW-4/D
837
848
�
00
I
00
845
O
834
'
a
lrftb J
Z
0
O
0
M
0
I
'•.
842
<0>
°� 1
> 831
•°
O-! a _ s e.ti._ _.
LY
°. may,
°o* <%> ° °°p° °° °O
3
�
aoo oe ° �o °��•°
o
839
3
c 828
O Op0 ��•
O.
0
L
I
cD
836
825
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
LEGEND Notes:
Cell 5 construction start (5/31/2021) NAVD 88—North American Vertical Datum 1988
DUKE
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE 4A
of
Future Phases 3 through 5 CCR excavation start (6/18/2021) Ft - feet
ENERGY-
REVISED BY: D. AVARD DATE:07/18/2025
GROUNDWATER ELEVATION HYDROGRAPHS
Cell 5 Blanket Underdrain construction start (9/20/2021) in - inches
GARCILINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
UPGRADIENT OF PHASE 2 EXPANSION (ILF-2S/D AND MW-4/D)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone Data) Manual Water Level Measurement
APPROVED BY: T. COLTON DATE:07/21/2025
GROUNDWATER CONDITIONS QUARTERLY REPORT
(Transducer
APRIL 2025 THROUGH DUNE 2025
Deep Groundwater Flow Zone (Transducer Data) Daily Total Rainfall (inches)
��
PROJECT MANAGER: T. COLTON
Bedrock Groundwater Flow Zone (Transducer Data) — — - Transient Groundwater Model Water Level Predicted Trend (Shallow)
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
— — - Transient Groundwater Model Water Level Predicted Trend (Deep)
synTerra
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA
www.synterracorp.com

GWA-4S/D
CLF21-10
842
6
852
6
O
00
O�
�O
850
00 841
p
O
O
p
'v0
O
Z
O O 4
Z
O
O_ O I p .�.LJr
4
O p0 O 4 O 4 p O
O
00
Op
c 848
O O �• O Op00 DOOb m
840
•
-
O O D*p 011-> p
LU
O •O<0OHO 2
U
2 fY
O
ate+
3 846
3 839
c
c
0
0
c7
ahilC7
838
0
844Llii0
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
GWA-4S - Total water level change from transducer installation on 07/30/2021 to 07/01/2025 is -4.0 feet.
CLF21-10 -Total water level change from transducer installation on 08/10/2021 to 07/01/2025 is -0.7 feet.
GWA-41D - Total water level change from transducer installation on 07/30/2021 to 07/01/2025 is -4.3 feet.
GWA-4S/D
CLF21-10
844
855
00
00 ao
p
a 852
p
Z 842
a
z----
v
'•
c
c
849
O OD
> 840
O p
m
W
L
OO O' OOQO4�>os� <9
OO O
846
838
0
,
3
o
0
836
843
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
LEGEND Notes:
Cell 5 construction start (5/31/2021) NAVD 88— North American Vertical Datum 1988
DUKE
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE46
of
Future Phases 3 through 5 CCR excavation start (6/18/2021) Ft - feet
ENERGY-
REVISED BY: D. AVARD DATE:07/18/2025
GROUNDWATER ELEVATION HYDROGRAPHS
UPGRADIENT OF PHASE 2 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021) In - Inches
CAROLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
(GWA-4S�D AND CLF21-10)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
APPROVED BY: T. COLTON DATE: 07/21/2025
Shallow Groundwater Flow Zone (Transducer Data) Manual Water Level Measurement
GROUNDWATER CONDITIONS QUARTERLY REPORT
Deep Groundwater Flow Zone (Transducer Data) Daily Total Rainfall (inches)
��
PROJECT MANAGER: T. COLTON
APRIL 2025 THROUGH JUNE 2025
Transient Groundwater Model Water Level Predicted Trend (Shallow)
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
Transient Groundwater Model Water Level Predicted Trend (Deep)
synTerra
www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF-UD
CLF21-11
817
6
830
6
O
O
00 815
00
828
—
Q
4
Q
4
Z
Z
LL
^
+;
LL
c 813
�—
c
826
—_
41
m
2 =
W
O OOP
2 oc
a,
811 6JOp 00 O O
aJ
f6
824
O O 00
3
3
c
c
0
0
C9
Q
11
0
822
809
0
6/1 /2021 2/1 /2022 10/1 /2022
6/1 /2023 2/1 /2024 10/1 /2024
6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
CLF-UD — Water level is stable during underdrain operations. Water levels spikes represent when pump was temporarily
out of service.
CLF21-11- Total water level change from transducer installation on 08/09/2021 to 07/01/2025 is -4.9 feet.
CLF-UD
CLF21-11
830
817
�O
_
00
00
0
828
815
>
Q
z
_
Z
*'
\
v
c
826
0
�OOOOOO�.O
813
m
>
v
O O�
O
>
W
O O Q�
uU
y`
824
O p40 000 O O. 00
,
NAAjAi
M
811
3
822
0
c�
809
820
6/1 /2021 2/1 /2022 10/1 /2022
6/1 /2023 2/1 /2024 10/1 /2024
6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
LEGEND
Cell 5 construction start (5/31/2021)
Notes:
NAVD 88—North American Vertical Datum 1988
DUKE
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE 4C
Future phases 3 through 5 CCR excavation start (6/18/2021)
of
Ft - feet
ENERGY-.
REVISED BY: D. AVARD DATE:07/18/2025
GROUNDWATER ELEVATION HYDROGRAPHS
Cell 5 Blanket Underdrain construction start (9/20/2021)
in - inches
GARQLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
WITHIN PHASE 2 EXPANSION (CLF-UD AND CLF21-11)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone (Transducer Data)
Manual Water Level Measurement
APPROVED BY: T. COLTON DATE:07/21/2025
GROUNDWATER CONDITIONS QUARTERLY REPORT
APRIL 2025 THROUGH DUNE 2025
Transient Groundwater Model water level predicted trend (Shallow)
Daily Total Rainfall (inches)
��
PROJECT MANAGER: T. COLTON
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
synTema
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA
I www.synterracorp.com

CLF21-12
CLF21-13/13R
821
6
824
6
00
b
I I
O
O O O
00 822
00 818
<8>O O
Q
4
Q
O�
4
Z
Z
lie
o
Q
o 820
p
O Op O O O O'0
' O O
0c 815
CLF21-13 was abandoned and replaced with
O O ODO Op M
O
>
CLF21-13R on November 4, 2021.
_
a�
v
2
Opp
2 CC
M818
I
I I
M 812
0
0
0
0
do
0
809
816
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
CLF21-13R - Total water level change from transducer installation on 11/08/2021 to 07/01/2025 is -8.8 feet.
CLF21 12 Total water level change from transducer installation on 08/09/2021 to 07/01/2025 is 3.6 feet.
CLF21-13 - Total water level change from transducer installation on 08/09/2021 to 10/01/2021 is -0.2 feet.
CLF21-12
CLF21-13/13R
827
823
00 822
4�
�6'
00
0 818
O.
0L!
O O O D O
00 �O O
a
I o 0 0
a'
Q
Op O
O
a
. o o° o0 00 0 0 0 ° 00o �o o coon oo
•
z
°O °o
z
V
poo
v 817
c 813
0
o
>
m
a)
-
`
W
L-
W 812
� 808
L
41
`
M
3
M
3
�
c
807
0803
o
L
(D
802
798
6/1/2021
2/1/2022 10/1/2022 6/1/2023 2/1/2024 10/1/2024 6/1/2025
6/1/2021
2/1/2022 10/1/2022 6/1/2023 2/1/2024 10/1/2024 6/1/2025
Date
Date
LEGEND Notes:
Cell 5 construction start (5/31/2021) NAVD 88—North American Vertical Datum 1988
DUKE
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE 4D
of
Future phases 3 through 5 CCR excavation start (6/18/2021) Ft - feet
ENERGY-.
REVISED BY: D. AVARD DATE:07/18/2025
GROUNDWATER ELEVATION HYDROGRAPHS
Cell 5 Blanket Underdrain construction start (9/20/2021) in - inches
GARQLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
WITHIN PHASE 2 EXPANSION (CLF21-12 AND CLF21-13/13R)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone (Transducer Data) Manual Water Level Measurement
APPROVED BY: T. COLTON DATE:07/21/2025
GROUNDWATER CONDITIONS QUARTERLY REPORT
APRIL 2025 THROUGH DUNE 2025
Transient Groundwater Model water level predicted trend (Shallow) Daily Total Rainfall (inches)
�� PROJECT
MANAGER: T. COLTON
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
synTema
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA
I
www.synterracorp.com

CLF21-14/14R
CLF21-15
6
827
6
822
In April of the Q2 2022 reporting period,
Q
piezometer CLF21-14 was extended and
re -named CLF21-14R.
821
00
00 825
Q4
Q
The CLF21-15transducer
4
Z
Z
was removed in April 2023
LL 820
LL
and replaced in July 2023
0�00
C
� ODO�jJ�
C
c
-
2 823
�Op0O
> 819
♦ ♦ p p
c
OO
c
W
0' O
0'
2 ♦Y
W
2
*T
3
j j 1
i
3 821
818
•
O
o
o
c7
C7
0
819
0
817
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
CLF21-14R - Total water level change from transducer installation on 04/08/2022 to 07/01/2025 is +0.2
feet.
CLF21-15 - Total water level change from transducer installation on 08/13/2021 to 07/01/2025 is -3.6
feet.
• • • • • • • CLF21-14 - Total water level change from transducer installation on 08/13/2021 to 03/22/2022 is -3.3 feet.
Total water level change from transducer installation on 07/31/2023 to 12/31/2023 is -0.9 feet.
CLF21-14/14R
CLF21-15
828
828
00
00
>
O�
> 824
825
a
z
'o
z
v
o
�'
o
o
4.
C 820
O O
822
LL
�O O
.0
O�0 0� O 0 �� �O�'� �OO.
d
\
O O
M
ate+
1°
3
816
819
c
o
o
(D
816
812
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
LEGEND Notes:
Cell 5 construction start (5/31/2021) NAVD 88—North American Vertical Datum 1988
DUKE
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE 4E
of
Future phases 3 through 5 CCR excavation start (6/18/2021) Ft - feet
ENERGY-.
REVISED BY: D. AVARD DATE:07/18/2025
GROUNDWATER ELEVATION HYDROGRAPHS
Cell 5 Blanket Underdrain construction start (9/20/2021) in - inches
cAaoLlnl,as
REVIEWED BY: S. SPINNER DATE:07/18/2025
WITHIN PHASE 2 EXPANSION (CLF21-14/14R AND CLF21-15)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone (Transducer Data) Manual Water Level Measurement
APPROVED BY: T. COLTON DATE:07/21/2025
GROUNDWATER CONDITIONS QUARTERLY REPORT
Transient Groundwater Model water level predicted trend (Shallow) Daily Total Rainfall (inches)
��
PROJECT MANAGER: T. COLTON
APRIL 2025 THROUGH DUNE 2025
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
synTerra I
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA
www.synterracorp.com

CLF-402
CLF23-408
6
806
6
815
O
�
• O ��
800
O
0 808
000 p�
O
00
Q
O
4
QO
,
4
z
O
z
794
16
c 801
--
241
788
W
i
OIO
2
i
'
2
.0
Gl
3 794
3
782
I
a
787
0
776
0
6/1 /2021 2/1 /2022 10/1 /2022
6/1 /2023 2/1 /2024 10/1 /2024
6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023
2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
CLF-402 - Total water level change from transducer installation on 07/27/2021 to 07/01/2025 is -24.1 feet.
CLF23-408 - Total water level change from transducer installation on 03/21/2023 to 07/01/2025 is -20.27
feet.
CLF-402
CLF23-408
815
810
0 809
o� �o
00
�
803
Op
o
\
Q
z
\
z
�O
Opp
v 803
c
796
�p�O
o
O
p
`
ft
>
('
p
W
\
O
797
W�
0
L �
789
N
O1
+•
�
3
3
c
3 791
782
Cog
OD
O
Op,
O
785
775
6/1/2021
2/1/2022 10/1/2022
6/1/2023 2/1/2024 10/1/2024
6/1/2025
6/1/2021
2/1/2022 10/1/2022 6/1/2023
2/1/2024 10/1/2024 6/1/2025
Date
Date
LEGEND
Cell 5 construction start (5/31/2021)
Notes:
NAVD 88— North American Vertical Datum
The modeled water levels are
DUKE
DRAWN BY: D. AVARD DATE:07/21/2021
FIGURE 4F
GROUNDWATER ELEVATION HYDROGRAPHS
Future 3 through 5 CCR excavation start (6/18/2021)
1988
truncated based upon the
pp
ENEI.GY=,
REVISED BY: D. AVARD DATE:07/18/2025
phases
of
expected shutdown of the Cell 5
DOWNGRADIENT OF THE PHASE 2 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021)
Ft - feet
underdrain pumping operation.
CAROLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
(CLF-402 AND 408)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
in - inches
The slower basin excavation rate
APPROVED BY: T. COLTON DATE:07/21/2025
Shallow Groundwater Flow Zone (Transducer Data) ♦ has extended the period needed to
Manual Water Level Measurement p
GROUNDWATER CONDITIONS QUARTERLY REPORT
Transient Groundwater Model water level predicted trend (Shallow) Daily Total Rainfall (inches)
operate the underdrain and will
PROJECT MANAGER: T. COLTON
APRIL 2025 THROUGH DUNE 2025
delay the shutdown of the Cell 5
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
underdrain.
WnTerra
www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF22-306/306R
CLF22-307/307R
6
806
6
804
00 - -� �►
oa
0
800
0
00
00
797
�p
Q
4
Q
I 0
4
Z
796
Z
aJ
♦
�
0
c
�
0
788
c
�=
>
792
>
W
2
i
2
f6
M
+M+
�
779
I �I ..I .
3
I
o III
00
3
�
788
�
• o.' �
�
��
0
0
I ,�
c7
C7
0
770
0
784
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1/2024 6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
CLF22-306 - Total water level change from transducer installation on 08/13/2021 to 06/26/2024
is -12.2 feet.
CLF22-307 - Total water level change from transducer installation on 04/08/2022 to 06/26/2024 is -14.9 feet.
CLF22-306R - Total water level change from transducer installation on 07/11/2024 to 07/01/2025
is +0.2 feet.
CLF22-307R - Total water level change from transducer installation on 07/11/2024 to 07/01/2025 is -4.5 feet.
CLF22-306/306R
CLF22-307/307R
810
815
CLF22-306 became
dry prior to
abandonment.
-
The piezometer
00
00
804
O
and transducer
j
806
CLF22-307 became
j�p
O O
were reinstalled in
Q
Z
dry prior to
Z
�O� O
July 2024.
abandonment.
I
O
The piezometer
798
c
797
and transducer
c
0
I
CLF22 306 was not
were reinstalled in
M
used in the
M
>
cu
`
July 2024.
>
p
Transient
LU
\ ♦ 1
W
792
\
Groundwater
ai
788
( U
O
Model calibration,
M
M
♦ ♦
,
water level
<%>
predictions were
786
�.
prepared following
t
P
779
OHO
O
installation of
Op��
C7
CLF22-306 (after
.
Op
OO
.
Transient
780
Groundwater
770
Model calibration)
6/1/2021
2/1/2022 10/1/2022 6/1/2023 2/1/2024 10/1/2024
6/1/2025
6/1/2021
2/1/2022 10/1/2022 6/1/2023 2/1/2024 10/1/2024 6/1/2025
Date
Date
LEGEND Notes:
Cell 5 construction start (5/31/2021) NAVD 88— North American Vertical Datum
The modeled water levels are
DUKE
DRAWN BY: D. AVARD DATE:07/21/2021
FIGURE 4G
GROUNDWATER ELEVATION HYDROGRAPHS
Future 3 through 5 CCR excavation start (6/18/2021) 1988
truncated based upon the
pp
ENEI.GY=.
REVISED BY: D. AVARD DATE:07/18/2025
phases of
expected shutdown of the Cell 5
DOWNGRADIENT OF THE PHASE 2 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021) Ft - feet
underdrain pumping operation.
CAROLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
(CLF22-306/306R and CLF22-307/307R)
Cell 5 Blanket Underdrain construction completion (10/22/2021) in - inches
The slower basin excavation rate
APPROVED BY: T. COLTON DATE:07/21/2025
Shallow Groundwater Flow Zone (Transducer Data) ♦ has extended the period needed to
Manual Water Level Measurement p
GROUNDWATER CONDITIONS QUARTERLY REPORT
Transient Groundwater Model water level predicted trend (Shallow) Daily Total Rainfall (inches)
operate the underdrain and will
PROTECT MANAGER: T. COLTON
APRIL 2025 THROUGH JUNE 2025
delay the shutdown of the Cell 5
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
underdrain.
synTerra
www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF24-501
CLF24-502
6
794
798
6
O
ti•
I
00 791
�
00 796
0
�
Q
I
4
Z
I
4
z
v
o,-71
c 788
�—
c 794
—_
41
I
O
>
IJJ
I
c
2 ♦Y
>
i�
c
2
GJ
W
M 785
M 792
�
O
o
C9
C7
782
0
790tLoV
0
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
6/1 /2021 2/1 /2022 10/1 /2022 6/1 /2023 2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
CLF24-501- Total water level change from transducer installation on 09/03/2023 to 07/01/2025 is -7.3 feet.
CLF24-502 - Total water level change from transducer installation on 09/03/2023 to 07/01/2025 is +1.3 feet.
CLF24-501
CLF24-502
794
798
O
00
0
O
> 791
>
< 796
—
a
�o
z
C
788
v 794
N
W
L
W
ai
-W
L
0
M
3
785
3 792
3p
Q
782
790 4
-
6/1/2021 2/1/2022 10/1/2022 6/1/2023 2/1/2024 10/1/2024 6/1/2025
6/1/2021 2/1/2022 10/1/2022 6/1/2023 2/1/2024 10/1/2024 6/1/2025
Date
Date
LEGEND Notes: The modeled water levels are
Cell 5 construction start (5/31/2021) NAVD 88— North American Vertical Datum
DUKE
DRAWN BY: D. AVARD DATE:07/21/2021
FIGURE 4H
GROUNDWATER ELEVATION HYDROGRAPHS
truncated based upon the
Future 3 through 5 CCR excavation start (6/18/2021) 1988
pp
ENERGY=,
REVISED BY: D. AVARD DATE:07/18/2025
phases of expected shutdown of the Cell 5
SOUTHWEST OF THE FUTURE PHASE 5 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021) Ft - feet underdrain pumping operation.
CAROLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
(CLF24-501 AND CLF24-502)
Cell 5 Blanket Underdrain construction completion (10/22/2021) in - inches
p The slower basin excavation rate
APPROVED BY: T. COLTON DATE: 07/21/2025
Shallow Groundwater Flow Zone (Transducer Data) ♦ has extended the period needed to
Manual Water Level Measurement p
GROUNDWATER CONDITIONS QUARTERLY REPORT
Transient Groundwater Model water level predicted trend (Shallow) Daily Total Rainfall (inches) operate the underdrain and will
PROJECT
MANAGER: T. COLTON
APRIL 2025 THROUGH DUNE 2025
delay the shutdown of the Cell 5
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
underdrain.
WnTerra
www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF24-503
CLF24-504
799
6
814
6
00 798
I
00
812
0
0
Q
I
4
Z
I
4
z
4
o .
v
0
c 797
c
810
—_
+�
41
W
I
O
ai
Uj
2 ♦Y
U
2
GJ
Gl
3 796
3
808
c
c
0
0
c7
C7
795
0
41 0
806
6/1 /2021 2/1 /2022 10/1 /2022
6/1 /2023 2/1 /2024 10/1 /2024
6/1 /2025
6/1 /2021
2/1 /2022 10/1 /2022 6/1 /2023
2/1 /2024 10/1 /2024 6/1 /2025
Date
Date
CLF24-503 - Total water level change from transducer installation on 09/03/2023 to 07/01/2025 is -0.5 feet.
CLF24-504 - Total water level change from transducer installation on 09/03/2023 to 07/01/2025 is -1.6 feet.
CLF24-503
CLF24-504
799
81300
-
00
> 798
z
812
a
z
4-;
0
j
0
I
797
v
811
N
W
L
W
ai
4+
L
M
3
M
796
810
c
0
0
/L^
V
795
809
6/1/2021 2/1/2022 10/1/2022
6/1/2023 2/1/2024 10/1/2024
6/1/2025
6/1/2021
2/1/2022 10/1/2022 6/1/2023
2/1/2024 10/1/2024 6/1/2025
Date
Date
LEGEND
Cell 5 construction start (5/31/2021)
Notes:
NAVD 88— North American Vertical Datum
The modeled water levels are
DUKE
DRAWN BY: D. AVARD DATE:07/21/2021
FIGURE 41
GROUNDWATER ELEVATION HYDROGRAPHS
Future 3 through 5 CCR excavation start (6/18/2021)
1988
truncated based upon the
pp
ENERGY=,
REVISED BY: D. AVARD DATE:07/18/2025
phases
of
expected shutdown of the Cell 5
WEST OF THE FUTURE PHASE 5 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021)
Ft - feet
underdrain pumping operation.
CAROLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
(CLF24-503 AND CLF24-504)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
p
in - inches
The slower basin excavation rate
APPROVED BY: T. COLTON DATE: 07/21/2025
Shallow Groundwater Flow Zone (Transducer Data) ♦ has extended the period needed to
Manual Water Level Measurement p
GROUNDWATER CONDITIONS QUARTERLY REPORT
Transient Groundwater Model water level predicted trend (Shallow)
Daily Total Rainfall (inches)
operate the underdrain and will
PROTECT MANAGER: T. COLTON
APRIL 2025 THROUGH JUNE 2025
delay the shutdown of the Cell 5
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
underdrain.
synTerra
www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF24-505
830
6
00 829
0
Q
4
z
I
O
}'
O
c 828
I
o =
Space Not Used
hill r
W
2
N
M 827
c
0
c�
0
826
6/1 /2021 2/1 /2022 10/1 /2022
6/1 /2023 2/1 /2024
10/1 /2024 6/1 /2025
Date
CLF24-505 - Total water level change from transducer installation on 09/03/2023 to 07/01/2025 is -1.3 feet.
CLF24-505
830
00
0 829
—
a
z
o 0
lit0
c
828
Loo'
y
Space Not Used
W
G!
827
C
3
O
Q
826
6/1/2021 2/1/2022 10/1/2022
6/1/2023 2/1/2024
10/1/2024 6/1/2025
Date
LEGEND
Cell 5 construction start (5/31/2021)
Notes: The modeled water levels are
NAVD 88— North American Vertical Datum
DUKE
DRAWN BY: D. AVARD DATE:07/21/2021
FIGURE 4J
Future phases 3 through 5 CCR excavation start (6/18/2021)
of 1988
truncated based upon the
the Cell 5
ENERGY-.
REVISED BY: D. AVARD DATE:07/18/2025
GROUNDWATER ELEVATION HYDROGRAPHS
Cell 5 Blanket Underdrain construction start (9/20/2021)
Ft - feet
expected shutdown of
underdrain pumping operation.
CAROLINAS
REVIEWED BY: S. SPINNER DATE:07/18/2025
WEST OF THE PHASE 2 EXPANSION (CLF24-505)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
in - inches
The slower basin excavation rate
APPROVED BY: T. COLTON DATE:07/21/2025
GROUNDWATER CONDITIONS QUARTERLY REPORT
Shallow Groundwater Flow Zone (Transducer Data)
Manual Water Level Measurement has extended the period needed to♦
APRIL 2025 THROUGH JUNE 2025
Transient Groundwater Model water level predicted trend (Shallow)
operate the underdrain and will
Daily Total Rainfall (inches) p
PROJECT MANAGER: T. COLTON
INDUSTRIAL
LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
delay the shutdown of the Cell 5
underdrain.
synTerra
MARSHALL
STEAM STATION, TERRELL, NORTH CAROLINA
www.synterracorp.com

E
Q
C1A
N
O
LL
140
120
FOR
F."M
10-K
0
9/1/2021
6/1/2022 3/1/2023 12/1/2023 9/1/2024
Notes: Date
gpm - gallons per minute
In. - inches
Flow data from the first day following a period of no flow were not plotted.
n
i❑
2
0
6/1/2025
f DUKE
DRAWN BY: T. COLTON
DATE: 10/13/2021
FIGURE 5
US ENERGY
REVISED BY: D. AVARD
DATE:07/18/2025
CELL 5 (UNDERDRAIN) ACTUAL PUMPING FLOW RATE VS. SIMULATED FLOW RATE
CAROLINA$
CHECKED BY: S. SPINNER
DATE:07/18/2025
GROUNDWATER CONDITIONS QUARTERLY REPORT
APPROVED BY: T. COLTON
DATE:07/21/2025
APRIL 2025 THROUGH JUNE 2025
�a
7
PROJECT MANAGER: T. COLTON
INDUSTRIAL LANDFILL NO. 1 (PERMIT NO. 1812-INDUS-2008)
smTerra
www.synterracorp.com
MARSHALL STEAM STATION
7'
TERRELL, NORTH CAROLINA

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
TABLE
1610
synTerra
Science & Engineering Consultants

TABLE 1
GROUNDWATER MONITORING NETWORK WELL INFORMATION AND WATER LEVELS
GROUNDWATER CONDITIONS QUARTERLY REPORT
APRIL 2025 THROUGH JUNE 2025
INDUSTRIAL LANDFILL NO. 1 (PERMIT NO. 1812-INDUS-2008)
MARSHALL STEAM STATION
DUKE ENERGY CAROLINAS, LLC, TERRELL, NC
Well/
Piezometer
ID
Date Well/
Piezometer
Installed
Date
Transducer
Installed
Measuring
Point
TOC Elevation
(Ft-NAVD 88)
Ground
Surface
Elevation
(Ft-NAVD 88)
Measured
Well Depth
(Ft-TOC)
Screened
Interval
(Ft-TOC)
Top of
Screen
Elevation
(Ft-NAVD 88)
Bottom
of Screen
Elevation
(Ft-NAVD 88)
Water Level
Measurement
(Ft-TOC)
03/28/2025
Groundwater
Elevation
(Ft-NAVD 88)
03/28/2025
Water Level
Measurement
(Ft-TOC)
05/06/2025
Groundwater
Elevation
(Ft-NAVD 88)
05/06/2025
Water Level
Measurement
(Ft-TOC)
06/03/2025
Groundwater
Elevation
(Ft-NAVD 88)
06/03/2025
Water Level
Measurement
(Ft-TOC)
07/01/2025
Groundwater
Elevation
(Ft-NAVD 88)
07/01/2025
CLF-402R4
5/21/2021
1/3/2025
826.31
823.45
57.9
47.9
57.9
778.41
768.41
37.71
788.60
38.31
788.00
38.60
787.71
38.75
787.56
CLF21-10
8/6/2021
8/6/2021
857.75
857.75
32.0
22.0
32.0
835.75
825.75
17.45
840.30
17.50
840.25
17.52
840.23
17.40
840.35
CLF21-11
8/5/2021
8/5/2021
850.17
850.08
41.6
31.6
41.6
818.53
808.53
24.58
825.59
24.48
825.69
24.50
825.67
24.36
825.81
CLF21-12
8/5/2021
8/5/2021
839.06
838.96
41.2
31.2
41.2
807.84
797.84
19.50
819.56
19.57
819.49
19.60
819.46
19.40
819.66
CLF21-13R
11/4/2021
11/8/2021
836.21
836.18
35.5
25.5
35.5
810.75
800.75
24.49
811.72
24.76
811.45
24.95
811.26
24.85
811.36
CLF21-14R
4/18/2022
4/18/2022
847.54
843.97
38.2
28.2
38.2
816.04
806.04
28.84
818.70
28.90
818.64
29.00
818.54
29.07
818.47
CLF21-15
8/10/2021
8/10/2021
864.37
864.37
55.0
45.0
55.0
819.37
809.37
41.61
822.76
41.68
822.69
41.76
822.61
41.83
822.54
CLF22-306#
10/31/2024
12/5/2024
823.40
820.40
43.0
33.0
43.0
790.40
780.40
36.60
786.80
37.25
786.15
37.55
785.85
37.32
786.08
CLF22-307#
6/25/2024
7/11/2024
807.50
804.30
32.1
22.1
32.1
785.40
775.40
29.24
778.26
30.30
777.20
30.09
777.41
30.50
777.00
CLF23-408R#
2/15/2023
1/3/2025
813.13
810.05
37.2
27.2
37.2
785.98
775.98
34.74
778.39
31.63
781.50
30.98
782.15
30.23
782.90
CLF24-501
8/16/2024
9/3/2024
807.30
804.10
30.0
20.0
30.0
787.30
777.30
23.42
783.88
23.26
784.04
22.94
784.36
22.20
785.10
CLF24-502
8/16/2024
9/3/2024
806.50
803.10
25.0
15.0
25.0
791.50
781.50
13.34
793.16
12.80
793.70
12.03
794.47
12.05
794.45
CLF24-503
8/15/2024
9/3/2024
815.00
812.30
55.0
45.0
55.0
770.00
760.00
18.61
796.39
18.63
796.37
18.22
796.78
18.25
796.75
CLF24-504
8/13/2024
9/3/2024
834.40
831.40
54.0
44.0
54.0
790.40
780.40
23.40
811.00
24.00
810.40
23.68
810.72
23.73
810.67
CLF24-505
8/14/2024
9/3/2024
856.20
853.60
55.0
45.0
55.0
811.20
801.20
27.90
828.30
28.05
828.15
28.00
828.20
27.92
828.28
GWA-4D
6/12/2015
7/30/2021
902.45
899.38
89.1
84.1
89.1
818.38
813.38
54.19
848.26
54.38
848.07
54.48
847.97
54.60
847.85
GWA-4S
5/19/2015
7/30/2021
901.97
898.98
67.2
52.2
67.2
849.78
834.78
54.48
847.49
54.60
847.37
54.22
847.75
54.95
847.02
ILF-2D
3/31/2019
7/30/2021
885.14
885.57
101.6
91.6
101.6
793.57
783.57
41.77
843.37
41.72
843.42
42.15
842.99
42.10
843.04
ILF-2S
3/31/2019
7/30/2021
884.79
885.21
51.6
41.6
51.6
843.21
833.21
44.57
840.22
44.60
840.19
44.69
840.10
44.67
840.12
MW-4
6/30/1989
7/30/2021
867.15
863.81
53.6
43.6
53.6
823.55
813.55
38.66
828.49
38.85
828.30
39.05
828.10
39.00
828.15
MW-4D
10/12/2006
7/30/2021
866.74
863.42
63.9
58.9
63.9
807.87
802.87
39.05
827.69
39.40
827.34
39.50
827.24
39.38
827.36
Notes:
# - Piezometer replaced to facilitate excavation. Replacement piezometers are located near original piezometers.
BGS - below ground surface
Ft - feet
NAVD 88 - North American Vertical Datum of 1988
TOC - top of casing
Prepared by: TWL Checked by: PBT
Page 1 of 1

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
APPENDIX A
WATER -LEVEL MONITORING DATA FILES
INCLUDED AS EXCEL FILE)
L7
synTerra
Science & Engineering Consultants

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
APPENDIX B
GROUNDWATER MODEL PREDICTED TREND FILES
INCLUDED AS EXCEL FILE)
L7
synTerra
Science & Engineering Consultants

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
APPENDIX C
UNDERDRAIN PUMPING DATA FILES
INCLUDED AS EXCEL FILE)
L7
synTerra
Science & Engineering Consultants

Groundwater Conditions Quarterly Report — April 2025 to June 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
APPENDIX D
MANN-KENDALL DATA
INCLUDED AS EXCEL FILE)
L7
synTerra
Science & Engineering Consultants