1812_2025 Q4 ILF Groundwater Conditions Report_20260130

INTERNAL
(� DUKE
ENERGY
January 30, 2026
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 — October 2025 through December 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 October 2025 through December 2025 (Q4 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 (Q1 2025) will be submitted by May 1, 2026.
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,
014r� kc>,��
Anne Davin, E.I.
Environmental Services
Attachments: Industrial Landfill No.1 (1812-INDUS-2008) Groundwater Conditions Quarterly Report — October
2025 through December 2025 (SynTerra; January 2026)
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

INTERNAL
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

LIP
synTerra
Science & Engineering Consultants
synterracorp.com
GROUNDWATER CONDITIONS QUARTERLY REPORT —
OCTOBER 2025 TO DECEMBER 2025
INDUSTRIAL LANDFILL NO. 1
PERMIT NO. 1812-INDUS-2008)
FOR
MARSHALL STEAM STATION
8320 EAST CAROLINA HIGHWAY 150
TERRELL, NC 28682
JANLIARY 29, 2026
PREPARED FOR
r DUKE
CA����i ENERGY.:
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Q� H4e'-. =DUKE ENERGY CAROLINAS, LLC
SEAL =
056667
CC
G. Thomas Colton, NC P.E. No. 056667 Brooke Patton
Associate Engineer/Project Manager Project Scientist
Scott A. Spinner, NC L.G.
Senior Peer Reviewer

Groundwater Conditions Quarterly Report — October 2025 to December 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
LIST OF FIGURES
Figure 1 Site Location Map
Figure 2 Monitoring Locations
Figure 3 Groundwater Elevation Contours — Upper Flow Zone (January 2026)
Figure 4A Upgradient of Phase 2 (ILF-2S/D, MW-4/D, GWA-4S/D, and CLF21-10)
Figure 413 Within Phase 2 (CLF21-11, CLF21-12, CLF21-13/13R, and CLF21-14/14R)
Figure 4C Within and West of Phase 2 (CLF21-15 and CLF24-505)
Figure 4D Downgradient and West of Phase 2 (CLF22-306/306R, CLF22-307/307R, CLF24-
503 and CLF24-504)
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
January 2026
Page i
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — October 2025 to December 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
I1[3111]y_T4.1111►VIA1;7_VUZI 13:ATJr_'%V[11]► l
Duke Energy Duke Energy Carolinas, LLC
DWM Division of Waste Management
gpm gallons per minute
ILF Industrial Landfill (Permit No. 1812-INDUS-2008)
NCDEQ North Carolina Department of Environmental Quality
reporting period fourth quarter 2025 (October 2025 to December 2025)
Site Marshall Steam Station
January 2026
Page H
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — October 2025 to December 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 fourth quarter of 2025 [October 2025 to December 2025 (reporting
period)] were used to evaluate groundwater conditions for the ILF Phase 2 (includes Cell 5 and
Cell 6), Phase 3 and 4, and Future Phase 5. Groundwater levels are monitored at piezometers,
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 13 of the
17 monitoring locations. Groundwater level trends could not be analyzed at 3 locations;
CLF22-306 and CLF22-307 were occasionally dry during the reporting period but
generally stable and CLF24-503 was abandoned in November 2025. Groundwater levels
increased at CLF24-504; which is located west of ILF Phase 4 and Future Phase 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 52 months. During the reporting
period, the average pumping rate was approximately 6.7 gallons per minute (gpm), a
decrease compared to that of the previous reporting period (7.4 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.
January 2026
Page 1-1
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — October 2025 to December 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 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 January 6, 2026, for the upper
(shallow) flow zone and were used to generate groundwater elevation contours (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 third 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 December
2025 (Figure 4A through Figure 4J). Key observations of those data include:
• Groundwater level data collected from July 2021 (when monitoring started) through
December 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 20 monitored locations. Stable groundwater levels were observed at five
of 20 locations (CLF21-11, CLF24-502, CLF24-503, and CLF24-505).
Decreasing or stable water level trends were observed in locations downgradient of
Phase 3 and Phase 4 during the reporting period, except for CLF24-504, which is located
side -gradient of the ILF Future Phase 5. CLF22-306 and CLF22-307 were not able to be
analyzed for trends; CLF24-503 was abandoned during the reporting period.
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.
January 2026 Page 2-1
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — October 2025 to December 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
Upgradient of the Phase 2
Water levels upgradient of the Phase 2 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
Figure 4A
MW-4D
Deep
Stable
Decreasing
East of the ILF Phase 2
Figure 4A
ILF-2S
Shallow
Stable
Decreasing
North of the ILF
Figure 4A
ILF-2D
Deep
Stable
Decreasing
North of the ILF
Figure 4A
GWA-4S
Shallow
Stable
Decreasing
West of the ILF Phase 2
Figure 4A
GWA-4D
Deep
Stable
Decreasing
West of the ILF Phase 2
Figure 4A
LCLF21-10
Shallow
Stable
Decreasing
West of the ILF Phase 2
Figure 4A
Within the Phase 2
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, Outside of Cell 5 and Cell 6
Water levels at the perimeter of the Phase 2 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 4B
CLF21-12
Shallow
Stable
Decreasing
Southwest of Cell 5
Figure 4B
CLF21-13R
Shallow
Stable
Decreasing
South of Cell 5
Figure 4B
CLF21-14R
Shallow
Decreasing
Decreasing
East of Cell 6
Figure 4B
CLF21-15
Shallow
Decreasing
Decreasing
East of Cell 6
Figure 4C
CLF24-505
Shallow
Stable
Decreasing
West of Cell 5
Figure 4C
Downgradient of the Phase 2
Water levels downgradient of the Phase 2 are decreasing or stable, except for CLF24-
504 where water levels temporarily increased during the reporting period.
January 2026
Page 2-2
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — October 2025 to December 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
Additionally, water level trends at CLF22-306 and CLF22-307 could not be analyzed due
being dry during the reporting period. The trends in CLF22-306 and CLF22-307 appear
generally stable (Figure 4D). 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
Cannot Analyze
due to becoming
CLF22-306
Shallow
Decreasing
Downgradient of the Phase 3
Figure 4D
dry but visibly
stable
Cannot Analyze
due to becoming
CLF22-307
Shallow
Decreasing
Downgradient of the Phase 3
Figure 4D
dry but visibly
stable
Abandoned
CLF24-503
Shallow
During Reporting
Stable
West of Future Phase 5
Figure 4D
Period
CLF24-504
Shallow
Increasing
Decreasing
West of Future Phase 5
Figure 4D
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 49 months. The average pumping
rate during the reporting period was 6.7 gpm. ILF Phase 2 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 0.9 million
gallons of water during the reporting period. The Phase 2 Cell 5 underdrain pump had an
average flow rate of 6.7gpm overall during the reporting period. Monthly average flow rates
during the reporting period were as follows:
• October 2025 — 6.8 gpm
• November 2025 — 6.9 gpm
• December 2025 — 6.5 gpm
January 2026
Page 2-3
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — October 2025 to December 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 Phases 2, 3, and 4and the Future Phase 5:
• Phase 2, Cell 5:
o Continued underdrain operations, with an average flow rate of approximately
6.7 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 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 underway.
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 Phase 5 expansion:
o Continued passive dewatering and excavation of coal combustion residuals.
January 2026
Page 3-1
Project: 00.0083.46.11

Groundwater Conditions Quarterly Report — October 2025 to December 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.
January 2026
Page 4-1
Project: 00.0083.46.11

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

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REVISED BY IF FOREMAN DATE_ 01/26/2026
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NOT BE USED FOR DESIGN OR ENGINEERING PURPOSES. TOPOGRAPHY PROVIDED
• 9 •BY TRANSASH.
5. CLF-503 WAS ABANDONED IN THE REPORTING PERIOD.
6. AERIAL IMAGERY IS A COMBINATION OF DUKE ENERGY PROPELLER AERIAL
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REVISED BY L. FOREMAN DATE: 01/28/2026 INDUSTRIAL LANDFILL NO. 1
CHECKED BY T. COLTON DATE: 01/28/2026
APPROVED BY T. COLT
DATE: 01/28/2026 (PERMIT NO. 1812-INDUS-2008)
PROJECT MANAGER: T. COLTON MARSHALL STEAM STATION
synTerra TERRELL, NORTH CAROLINA
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a _,_ ,• :, : RPM" 790 INDUSTRIAL LANDFILL NO. 1 WASTE BOUNDARY
CLF24-504 $10
1 $°0 808.66 yi am0 BOUNDARY BETWEEN LANDFILL PHASES AND CELLS
LEACHATE BASIN
. » a - DUKE ENERGY CAROLINAS PROPERTY LINE
0
/ N
CLF24-503^N... o ' TOPOGRAPHIC CONTOUR (10' INTERVAL)
�' • 777.40 > STREAM (AMEC NRTR)
NOTES.
1. WATER LEVELS WERE COLLECTED ON JANUARY 6, 2026.
c � m
.I
2. ELEVATIONS ARE REFERENCED TO THE NORTH AMERICAN VERTICAL DATUM OF 1988
`°" - '� i I ¢ ds.. •• (NAVD 88).
v O - ` 3 THE STREAMS AND WETLANDS JURISDICTIONAL DETERMINATION WAS APPROVED BY THE
CLF22 306 U.S. ARMY CORPS OF ENGINEERS ON OCTOBER 25, 2017 (SAW 2015 01412) WETLANDS AND
<•o�•?- - 785.38 6`o yr STREAMS BOUNDARIES WERE OBTAINED FROMAMEC FOSTER WHEELER ENVIRONMENTAL
AND INFRASTRUCTURE, INC. NATURAL RESOURCES TECHNICAL REPORT (NRTR) DATED JUNE
2015.
4. THE TOPOGRAPHY IS SHOWN FOR REFERENCE PURPOSES ONLY AND SHOULD NOT BE
USED FOR DESIGN OR ENGINEERING PURPOSES. TOPOGRAPHY PROVIDED BY TRANSASH.
p• -}, n1`�.` .4• Y %r� = *�.`,� 5. BOUNDARIES ARE PROVIDED BY DUKE ENERGY AND ARE APPROXIMATE.
is
K, ' - `-•'si'j - v": n ° - 6. AERIAL IMAGERY IS A COMBINATION OF DUKE ENERGY PROPELLER AERIAL PHOTOGRAPHY
CAPTURED ON DECEMBER 19, 2025, AND MAXAR SATELLITE IMAGERY OBTAINED FROM ESRI
'i f `-?✓L _ • L % F" ONLINE, CCAPTURED ON AUGUST 23, 2021.
7 DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
-' - _ - ' •� y COORDINATE SYSTEM RIPS 3200 (NAD 83).
— i
r� •-' - j - - - 8. ^ - WELL IS ABANDONED. WATER LEVEL FROM MOST RECENT WATER LEVEL SWEEP
6
`CLF22 3 7 - o�_ � >, ,. i (11/4/20 25). )
n (� F
777.9(0 7 — i r 9. CLF-UD IS NOT APPLICABLE NA BECAUSE IT IS A SET UNDERDRAIN PUMP LOCATION.
13. A
X
•,5 71 - r- •+•+. .t^ .. - °` GRAPHIC SCALE
200 0 200 400 FIGURE 3
1 -
DUKE
GROUNDWATER ELEVATION CONTOURS
ENERGY. (IN FEET)
1�-AsouNAS UPPER FLOW ZONE (JANUARY 2026)
DRAWN BY: T. KING DATE: 05/12/2022 GROUNDWATER CONDITIONS QUARTERLY REPORT
REVISED BY: L FOREMAN DATE:01/28/2026 OCTOBER 2025 THROUGH DECEMBER 2025
n F CHECKED BY: B. PA70N DATE:01/28/2026 INDUSTRIAL LANDFILL NO. 1 (PERMIT NO. 1812-INDUS-2008)
!E+ APPROVED BY: T. COLTON DATE: 01/28/2026 MARSHALL STEAM STATION
PROJECT MANAGER: T. COLTON
WnTerra TERRELL, NORTH CAROLINA
- - wwws nterracor .com
G.\O ARCGIS PRO PROJECTS\DUKE ENERGY\MARSHALL\2025\GW CONDITIONS OUARTERLY REPORT\GW CONDITIONS OUARTERLY REPORT JULYAPRX

ILF-2S/D
MW-4/D
848
834
846 I
00 ° °
b
00
0
0 0 0
0
832
0
> 844 I 0 8 0 0 0 00 0
° ° °° °4 O
>
Z o° 0 r°° °p o
n On
C. °
_
Z
o
842 ° 00 00
;�
'..'
830
C
0
O
0
° O
00
—
•f0
fW ° 0 0 ° 000
J_
00 0
0
4-
00 000
0❑ 70 0 00 0 0 00 0 0 0 00 0 0 0
840
M
N
6° 6° ]0 ° 00 0 00
4
LU
LU
82$
p
p 0 00 00 0 00 000
60
W
2
0 0
00
838
O
O
836 I
Q
0
�
0
D6/2021 1212021 062022 122022 062023 12 023 062024 122024 062025 122025
D$ 1)21
12f21)21 D6 1)22 12f21)22 06,1^2023 12f21)23 08ir2024 12 1)24 D&2D25 12025
Date
Date
ILF-2S - Total water level change from transducer installation on 07/30/2021 to 01/06/2026 is -1.9 feet.
MW-4 - Total water level change from transducer installation on 07/30/2021 to 01/06/2026 is -4.8
feet.
ILF-2D - Total water level change from transducer installation on 07/30/2021 to 01/06/2026 is -2.4 feet.
MW-41) - Total water level change from transducer installation on 07/30/2021 to 01/06/2026 is
-5.1 feet.
GWA-4S/D
$
CLF21-10
$
842
854
00
C 852
6
0 I
> ° I_
Q
Z
0 0 0
0 0
0
Z 1
Q,� O
0 0 0 0 0 0 op 0 IL
+j 8ifti F' — -
i V J V
SL
i�
��
0 �. O 0 O 0 0 00 0 O 0
¢ 0 0
4 QQ
C 0
4
_
O
++
840
Q
T 0 -
1
4 _
0 °
848 ¢°04 op b0°
C
'
W
0 00
Q CG p° 0
o ° Oq0 °0 0 74 Op O
L
° 0 0040
° 0
LU t o 0 0 o tld 000 70 0 d 00
f0
W
846
2
3
8392
C
0
I
i $+44 I i I I i j� i III auk ly i 1 I.i j- iijil iji ii
gag
o
MI)21 12r2D21 06/2022 122M 0&2023 122023 0&2024 12J2024 OW025 1=025
W62021
12)2021 OU2022 12J2022 0&2023 112023 M&2024 1212024 Hb2025 12J2025
Date
Date
GWA-4S - Total water level change from transducer installation on 07/30/2021 to 01/06/2026 is -4.6 feet.
CLF21-10 -Total water level change from transducer installation on 08/10/2021 to 01/06/2026 is
-1.2 feet.
GWA-4D - Total water level change from transducer installation on 07/30/2021 to 01/06/2026 is -5.0 feet.
LEGEND Notes:
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE4A
Cell 5 construction start (5/31/2021) NAVD 88— North American Vertical Datum of 1988
��,
d
DUKE
REVISED BY: H. CUNNINGHAM DATE: 1/22/2026
GROUNDWATER ELEVATION HYDROGRAPHS
Future Phases 3 through 5 CCR excavation start (6/18/2021) Ft. - feet
ti
ENERGY.
UPGRADIENT OF PHASE 2 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021) in. - inches
CAROLINAS
REVIEWED BY: T. COLTON DATE: 1/22/2026
(ILF-2S/D, MW-4/D, (GWA-4S/D AND CLF21-10)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone (Transducer Data) Manual Water Level Measurement
APPROVED BY: T. COLTON DATE: 1/22/2026
GROUNDWATER CONDITIONS QUARTERLY REPORT
Daily Total Rainfall (inches)
��
Deep Groundwater Flow Zone (Transducer Data)
Transient Groundwater Model Water Level Predicted Trend (Shallow)
PROJECT MANAGER: T. COLTON
OCTOBER 2025 THROUGH DECEMBER 2026
Bedrock Groundwater Flow Zone (Transducer Data)
Transient Groundwater Model Water Level Predicted Trend (Deep)
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
Transient Groundwater Model Water Level Predicted Trend (Bedrock)
synTerra
F www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF21-11
CLF21-12
830
828
00
00
825
Q
Z
U.
6L 024 ,I
0
f6
i
022
W
L
020
c
0
L
v 818 � I
06J2021 1212021 06J2022 1212022 06J2023 1212023 06J2024 12J2024 W2025 12J2025
Date
CLF21-11- Total water level change from transducer installation on 08/09/2021 to 01/06/2026 is -4.9 feet.
8
6
2
0
825 -
00 820 -
Q
Z Ly 815
c
f0
i
810 -
W
L
3
-
3
o
/
V
;l
5 ° ° 0 ° 00
0 q00 00000000°000 00AJh
0 0
L
t
1
1
k
ti
ti
ti
w
III
s
4 _
6
d
06J2021 1=021 0612022 12J2022 062023 12J2023 06J2024 1212024 06J2025 12J2025
Date
CLF21-12 - Total water level change from transducer installation on 08/09/2021 to 01/06/2026 is -4.0 feet.
M
C
FY
CLF21-13 13R
CLF21-14/14R
8
822
-
In April of the Q2 2022 reporting period,
82d
piezometer CLF21-14 was extended and
•
,
I' re -named CLF21-14R.
q q
0 0000 0 0°
°
00
Q
821
I,
6
6
00
/ 815
Q
T
Z
%
•
Z
`
0 0o 00 0 0
q
�
820
O
I
LL
\
0 00 0
Oq
i
r
C
I.
1
�.
i
\
00
4
-W
i
4
810
0 0 0
f0
M
•
• i 0 0
i.+
M
•�
LU
Big
D
Awe
0 0
O 0 0
Qj
W
%
\
L
•
qq O
q q
8d5
'
+v+
3
q as
C.
3
2
c
818
q°
2
o
0 800
A,
a
I
III
i
817
0
0
W2021 1=021 06J2022 1=22 06J2023
12J2023 062024 1212024 06J20251 12J2025
06f 1 122021
W2022 122022 flB= IM022 06J2024 12J2024 W2025 12J2025
Date
Date
CLF21-13R - Total water level change from transducer installation on 11/08/2021 to 01/06/2026 is -8.9 feet.
CLF21-14R - Total water level change from transducer installation on 04/08/2022 to 01/06/2026 is +0.1 feet.
CLF21-13 - Total water level change from transducer installation on 08/09/2021 to 10/01/2021 is -0.2 feet.
CLF21-14
- Total water level change from transducer installation on 08/13/2021 to 03/22/2022 is -3.0 feet.
LEGEND
Notes:
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE4B
Cell 5 construction start (5/31/2021)
NAVD 88— North American Vertical Datum of 1988
DUKE
GROUNDWATER ELEVATION HYDROGRAPHS
Future Phases 3 through 5 CCR excavation start (6/18/2021)
Ft. - feet
ti
ENERGY.
REVISED BY: H. CUNNINGHAM DATE: 1/22/2026
WITHIN PHASE 2 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021)
in. - inches
CAROLINAS
REVIEWED BY: T. COLTON DATE: 1/22/2026
(CLF21-11, CLF21-12, CLF21-13/13R AND CLF21-14/14R)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone (Transducer Data)
Manual water Level Measurement
APPROVED BY: T. COLTON DATE: 1/22/2026
GROUNDWATER CONDITIONS QUARTERLY REPORT
Shallow Groundwater Flow Zone (Transducer Data)
Daily Total Rainfall (inches)
�,�
PROJECT MANAGER: T. COLTON
OCTOBER 2025 THROUGH DECEMBER 2026
Transient Groundwater Model water level predicted trend (Shallow)
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
synTerra
F www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF21-15
CLF24-505
seo
see
$
826
The CLF21-15transducer
B
829
6
00
°
was removed in April 2023
0
C
and replaced in July 2023
Q
Q
Z
Z
�;
•,
++ 824
0
° O O°°
O°
4
_
c
O
820
4
O
� O ° ° ° 00
O
°
° °
+'
f0
>
DO
°
° $ O °
•
e22
°
cp
W
L
I I
°C
1
827
2
�
c 820
'
o
44,
oL
Q
I 101111IL it ' 11 if I 1bl'Ild117.
826
°
o4
W2021 1212021 0612022 1212022 W2023 1212023 0612024 1212024 0612025 1212025
0&2021
1212021 OEl2022 12i2022 062023 1212023 0&2024 1=24 06202" 1212D25
Date
CLF24-505 - Total water level change from transducer installation on 09/03/2023 to 01/06/2026 is -2.3 feet.
CLF21-15 - Total water level change from transducer installation on 08/13/2021 to 01/06/2026 is -4.0
feet.
Total water level change from transducer installation on 07/31/2023 to 12/31/2023 is -2.1 feet.
Space Not Used
Space Not Used
LEGEND Notes:
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE4C
Cell 5 construction start (5/31/2021) NAVD 88— North American Vertical Datum of 1988
DUKE
GROUNDWATER ELEVATION HYDROGRAPHS
Future phases 3 through 5 CCR excavation start (6/18/2021) Ft. - feet
ti ENERGY.
REVISED BY: H. CUNNINGHAM DATE: 1/22/2026
WITHIN AND WEST OF PHASE 2 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021) in. - inches
CAROLINAS
REVIEWED BY: T. COLTON DATE: 1/22/2026
(CLF21-15 AND CLF24-505)
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone (Transducer Data) � Manual Water Level Measurement
APPROVED BY: T. COLTON DATE: 1/22/2026
GROUNDWATER CONDITIONS QUARTERLY REPORT
Shallow Groundwater Flow Zone (Transducer Data) Daily Total Rainfall (inches)
�,�
PROJECT MANAGER: T. COLTON
OCTOBER 2025 THROUGH DECEMBER 2025
Transient Groundwater Model water level predicted trend (Shallow)
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
synTerra
www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

CLF22-306/306R
CLF22-307/307R
CLF22-307 became
8 CLF22-306
g dry prior to
810
became dry
abandonment.
prior to
The piezometer
abandonment.
810
and transducer
805
ti
The piezometer
were reinstalled in
and transducer
5
�
y
5 July 2024.
00
were reinstalled
00,�'*
; •
in July 2024.
800
> 800
Z
CLF22-306 was
Z
•
+.;
not used in theU.
{;
%
795
1
7 Transient
4=
=
¢
C
Groundwater
o 700
x *
+�
.
M Model
M
>
c calibration,
>
c
M790
•
°
M water level
w
°o oo
° ° ° °
predictions
2
c+o
°
2 were prepared
o 780
00 0
7g5
following
l oo o°
3
installation of
3
°
° o o° do o o
O
CLF22-306 (after
o
C7 700
Transient
C9 770
0 Groundwater
0
O6i2021
12i2021 Ofii2022 12l2022 0fii2023 1Date 0&2024 12i2024 0fii202�� 12l2025
Model
Mfi2021
12l2021 0&2022 12l2022 062023 1=023 0&2024 12l2024 0&202" 121202"
calibration)
Date
CLF22-306 - Total water level change from transducer installation on 04/08/2022 to 06/26/2024
is -12.0 feet.
CLF22-307 - Total water level change from transducer installation on 04/08/2022 to 06/26/2024
is -11.3 feet.
CLF22-306R - Total water level change from transducer installation on 07/11/2024 to 01/06/2026
is -0.8 feet.
CLF22-307R - Total water level change from transducer installation on 07/11/2024 to 01/06/2026
is -4.5 feet.
CLF24-503
CLF24-504
$
$
800
�
8'12
O
°
798
00
5
°
5
00
O
00
o
0 o
Z 795
Z
++
-71
i+
4 C
=
4• C
O
O
o
_�
794
� 808
°
O
C
W
W
o
�+
2
+'
2
3 792
o3
°
= 805
3
3
O
O
/L) 790
v
V
0
0&2021
1222021 0&2022 1212022 0&2023 12;2023 M;202- 12;202- M;2025 1212025
0&2021
1212021 0&2022 1212022 0&2023 1212023 0&2024 1212024 0&2025 1212025
Date
Date
CLF24-503 - Total water level change from transducer installation on 09/03/2023 to 01/06/2026 is -5.4
feet.
CLF24-504 - Total water level change from transducer installation on 09/03/2023 to 01/06/2026 is -5.0
feet.
LEGEND Notes:
DRAWN BY: D.AVARD DATE:07/21/2021
FIGURE4D
Cell 5 construction start (5/31/2021) NAVD 88— North American Vertical Datum of 1988
DUKE
GROUNDWATER ELEVATION HYDROGRAPHS
Future phases 3 through 5 CCR excavation start (6/18/2021) Ft. - feet
ti: ENERGY.,.
REVISED BY: H. CUNNINGHAM DATE: 1/22/2026
DOWNGRADIENT AND WEST OF THE PHASE 2 EXPANSION
Cell 5 Blanket Underdrain construction start (9/20/2021) in. - inches
CAROLINAS
REVIEWED BY: T. COLTON DATE: 1/22/2026
(CLF22-306/306R, CLF22-307/307R, CLF24-503, AND CLF24-504 )
Cell 5 Blanket Underdrain construction completion (10/22/2021)
Shallow Groundwater Flow Zone (Transducer Data) Manual Water Level Measurement
APPROVED BY: T. COLTON DATE: 1/22/2026
GROUNDWATER CONDITIONS QUARTERLY REPORT
Shallow Groundwater Flow Zone (Transducer Data) Daily Total Rainfall (inches)
10
PROJECT MANAGER: T. COLTON
OCTOBER 2025 THROUGH DECEMBER 2025
Transient Groundwater Model water level predicted trend (Shallow)
INDUSTRIAL LANDFILL NO 1. (PERMIT NO. 1812-INDUS-2008)
synTerra
F www.synterracorp.com
MARSHALL STEAM STATION, TERRELL, NORTH CAROLINA

Legend
x Actual Pumping Flow Rate (gpm)
Rainfall Daily Total (inches)
Steady State Blanket Underdrain Model Flow of
18 gpm as presented in Technical Memorandum:
Modeling Support for the ILF Phase 2 Permit to Construct
Modifications
x
xx
x x x
x x xxx, x x x x
x >M x
x
x c x
x x x x x
,x xxrk x x�ljlir x
�
x �CM%&4111111&
x
y x
xNX
x x
x
x x x i �l�i�il���iU��[
1210112 021 1210112022
Notes:
gpm - gallons per minute
12:ii1:2i12')
Date
x
1210112024 12JO112025
B
c�
U
S
DRAWN BY: T. COLTON DATE: 10/13/2021
FIGURE 5
UDUKE
ENERGY
REVISED BY: H. CUNNINGHAM DATE: 1/22/2026
CELL 5 (UNDERDRAIN) ACTUAL PUMPING FLOW RATE
CAROLINAS
CHECKED BY: S. SPINNER DATE: 1/22/2026
GROUNDWATER CONDITIONS QUARTERLY REPORT
APPROVED BY: T. COLTON DATE: 1/22/2026
PROJECT MANAGER: T. COLTON
OCTOBER 2025 THROUGH DECEMBER 2025
INDUSTRIAL LANDFILL NO. 1 (PERMIT NO. 1812-INDUS-2008)
��
www.synterracorp.com
smTerra
MARSHALL STEAM STATION
7'
TERRELL, NORTH CAROLINA

Groundwater Conditions Quarterly Report — October 2025 to December 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
OCTOBER 2025 THROUGH DECEMBER 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)
09/29/2025
Groundwater
Elevation
(Ft-NAVD 88)
09/29/2025
Water Level
Measurement
(Ft-TOC)
11/04/2025
Groundwater
Elevation
(Ft-NAVD 88)
11/04/2025
Water Level
Measurement
(Ft-TOC)
12/04/2025
Groundwater
Elevation
(Ft-NAVD 88)
12/04/2025
Water Level
Measurement
(Ft-TOC)
01/06/2026
Groundwater
Elevation
(Ft-NAVD 88)
01/06/2026
CLF21-10
8/6/2021
8/6/2021
857.75
857.75
32.0
22.0
32.0
835.75
825.75
17.67
840.08
17.90
839.85
17.90
839.85
17.90
839.85
CLF21-11
8/5/2021
8/5/2021
850.17
850.08
41.6
31.6
41.6
818.53
808.53
24.60
825.57
24.75
825.42
24.77
825.40
24.68
825.49
CLF21-12
8/5/2021
8/5/2021
839.06
838.96
41.2
31.2
41.2
807.84
797.84
19.91
819.15
20.40
818.66
20.11
818.95
20.03
819.03
CLF21-13R
11/4/2021
11/8/2021
836.21
836.18
35.5
25.5
35.5
810.75
800.75
26.70
809.51
27.12
809.09
26.83
809.38
26.52
809.69
CLF21-14R
4/18/2022
4/18/2022
847.54
843.97
38.2
28.2
38.2
816.04
806.04
29.20
818.34
29.33
818.21
29.52
818.02
29.58
817.96
CLF21-15
8/10/2021
8/10/2021
864.37
864.37
55.0
45.0
55.0
819.37
809.37
42.09
822.28
42.16
822.21
42.25
822.12
42.30
822.07
CLF22-306
10/31/2024
12/5/2024
823.40
820.40
43.0
33.0
43.0
790.40
780.40
37.33
786.07
37.37
786.03
Dry
Dry
38.02
785.38
CLF22-307
6/25/2024
7/11/2024
807.50
804.30
32.1
22.1
32.1
785.40
775.40
29.65
777.85
29.80
777.70
Dry
Dry
29.60
777.90
CLF24-503
8/15/2024
9/3/2024
815.00
812.30
55.0
45.0
55.0
770.00
760.00
23.45
791.55
37.60
777.40
Abandoned
Abandoned
Abandoned
Abandoned
CLF24-504
8/13/2024
9/3/2024
834.40
831.40
54.0
44.0
54.0
790.40
780.40
27.32
807.08
27.03
807.37
26.65
807.75
25.74
808.66
CLF24-505
8/14/2024
9/3/2024
856.20
853.60
55.0
45.0
55.0
811.20
801.20
28.49
827.71
28.73
827.47
28.90
827.30
28.90
827.30
GWA-41)
6/12/2015
7/30/2021
902.45
899.38
89.1
84.1
89.1
818.38
813.38
55.26
847.19
55.56
846.89
55.31
847.14
55.47
846.98
GWA-4S
5/19/2015
7/30/2021
901.97
898.98
67.2
52.2
67.2
849.78
834.78
55.31
846.66
55.47
846.50
55.38
846.59
55.56
846.41
ILF-21)
3/31/2019
7/30/2021
885.14
885.57
101.6
91.6
101.6
793.57
783.57
42.23
842.91
42.15
842.99
44.89
840.25
44.30
840.84
ILF-2S
3/31/2019
7/30/2021
884.79
885.21
51.6
41.6
51.6
843.21
833.21
44.80
839.99
44.83
839.96
44.67
840.12
44.78
840.01
MW-4
6/30/1989
7/30/2021
867.15
863.81
53.6
43.6
53.6
823.55
813.55
39.08
828.07
39.90
827.25
39.50
827.65
39.65
827.50
MW-4D
10/12/2006
7/30/2021
866.74
863.42
63.9
58.9
63.9
807.87
802.87
39.70
827.04
39.97
826.77
39.84
826.90
39.90
826.84
Notes:
Ft - feet
NAVD 88 - North American Vertical Datum of 1988
TOC - top of casing
Prepared by: GTC BLP Checked by: CSB
Page 1 of 1

Groundwater Conditions Quarterly Report — October 2025 to December 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)
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Groundwater Conditions Quarterly Report — October 2025 to December 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)
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Groundwater Conditions Quarterly Report — October 2025 to December 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)
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Groundwater Conditions Quarterly Report — October 2025 to December 2025
Duke Energy Carolinas, LLC - Marshall Steam Station - Industrial Landfill No. 1
Terrell, North Carolina
APPENDIX D
MANN-KENDALL DATA
INCLUDED AS EXCEL FILE)
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