1812_DukeMarshall_Ph4GWSep_FID2076445_20250730

DUKE
ENERGY®
July 30, 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
Re: Groundwater Vertical Separation Documentation
Industrial Landfill No. 1 Phase 4, Cell 8
Permit No.: 1812-INDUS-2008
Marshall Steam Station
Catawba County, North Carolina
Dear Ms. Moutos:
525 South Tryon Street
Charlotte, NC 28202
Mail Code DEP-36A
Attached to this letter is historical and recent groundwater elevation data for monitoring locations within and in
the vicinity of Industrial Landfill No. 1 (ILF; Permit No. 1812-INDUS-2008) at the Marshall Steam Station located
near Terrell, in Catawba County, North Carolina. This data is being provided as a demonstration of groundwater
vertical separation for ILF Phase 4, Cell 8 as required by North Carolina General Statutes (NCGS) Article 9
130A- 295.6(f). Attached to this submittal are slides showing the updated groundwater separation figures for
the landfill as of March 10, 2025. This date was selected because it represents a comprehensive dataset used
to generate the contour figure. Groundwater elevation in the vicinity of the ILF Phase 4, Cell 8 has continued
to be monitored through July 1, 2025, and has been attached for reference. The abandonment of monitoring
wells CLF-401, CLF23-406, and CLF23-407 was approved by the Division February 14, 2025. The
abandonment of monitoring wells CLF-402, CLF23-405, and CLF23-408 was approved by the Division March
13, 2025.
Groundwater elevations have been and continue to be monitored throughout the expansion of the ILF.
Groundwater elevations demonstrated substantial vertical separation (>20 feet) between the water table and
the compacted soil liner (CSL) design grades of ILF Phase 4, Cell 8 on March 10, 2025 (shown in the attached
slides). Groundwater elevations in the vicinity of the ILF continue to decrease, improving groundwater vertical
separation for ILF Phase 4, Cell 8. For locations within the vicinity of the ILF Phase 4, Cell 8 (CLF-402R, CLF21-
13R, CLF22-306RR, CLF22-307R, CLF23-405, CLF23-408R, CLF24-501, CLF24-502) groundwater
elevations have changed between +1.56 ft (CLF24-502) and -28.03 ft (CLF23-405). The slight increase in
groundwater elevation in piezometers CLF24-502 and CLF24-503 is likely due to limited duration of data
collection, as these piezometers were installed last year. All fluctuations in groundwater elevation have
maintained separation between the base grades of the ILF Phase 4, Cell 8 and the top of the groundwater
surface of greater than 20 feet.
If you have any questions or need additional information regarding this submittal, please contact me at
[e-mail], or 919-616-2333.
Page 1 of 2

Industrial Landfill No. 1 Phase 4, Cell 8 - Groundwater Vertical Separation
July 30, 2025
Sincerely,
Anne Davin, E.I.
Environmental Services
Attachments: Marshall Industrial Landfill No. 1 Comprehensive Groundwater Elevation Monitoring Data
(SynTerra, July 2025)
Industrial Landfill No. 1 Phase 4 Groundwater Vertical Separation Update Presentation (Duke
Energy, July 30, 2025)
Cc: Deana Yitbarek, NCDEQ
Sherri Stanley, NCDEQ
Ashley Healy, Duke Energy
Ed Sullivan, Duke Energy
Tyler Hardin, Duke Energy
Kim Witt, Duke Energy
Jake Muessen, Duke Energy
Dan Zakary, Duke Energy
Page 2 of 2

Marshall Landfill Phase 4
Groundwater Separation
Based on March 2025 Data

Interpolated GW Elevation
within Landfill Phase 4
(3/10/2025 data)
Well ID
Easting
Northing
March 2025 WL (ft)
CLF-402R
1413217.80
685598.80
789.16
CLF21-11
1412572.20
686572.30
825.71
CLF21-12
1412518.20
686217.40
819.84
CLF21-13R
1412818.66
686085.92
812.10
CLF21-14R
1414268.70
686027.10
818.88
CLF21-15
1414410.00
686307.70
822.86
CLF22-306RR
1413817.98
685002.97
787.04
CLF22-307R
1413298.66
684435.19
778.91
CLF23-405
1413022.67
684921.13
776.88
CLF23-408R
1413270.88
685262.35
779.82
CLF24-501
1412762.60
685106.80
783.60
CLF24-502
1412572.20
685104.50
793.50
CLF24-503
1412442.40
685371.10
796.58
CLF24-504
1412287.10
685599.00
811.87
CLF24-505
1412145.50
686132.70
828.54
MW-04
1414395.00
686658.00
828.60
Notes:
1. Head contours interpolated by Surfer using the Kriging gridding method
2. Contour interval = 0.5 feet
F21-15
�CLF21-14R

Interpolated GW Elevation
within Landfill Phase 4
(3/10/2025 data)
Well ID
Easting
Northing
March 2025 WL (ft)
CLF-402R
1413217.80
685598.80
789.16
CLF21-11
1412572.20
686572.30
825.71
CLF21-12
1412518.20
686217.40
819.84
CLF21-13R
1412818.66
686085.92
812.10
CLF21-14R
1414268.70
686027.10
818.88
CLF21-15
1414410.00
686307.70
822.86
CLF22-306RR
1413817.98
685002.97
787.04
CLF22-307R
1413298.66
684435.19
778.91
CLF23-405
1413022.67
684921.13
776.88
CLF23-408R
1413270.88
685262.35
779.82
CLF24-501
1412762.60
685106.80
783.60
CLF24-502
1412572.20
685104.50
793.50
CLF24-503
1412442.40
685371.10
796.58
CLF24-504
1412287.10
685599.00
811.87
CLF24-505
1412145.50
686132.70
828.54
MW-04
1414395.00
686658.00
828.60
Notes:
1. Head contours interpolated by Surfer using the Kriging gridding method
2. Contour interval = 0.5 feet
CLF21-14 R

Calculated GW
Separation from the
bottom of the Landfill
Phase 4 subgrade
(3/10/2025 data)
• GW separation was calculated as
subgrade elevation — interpolated
groundwater elevation
• Separation > 20 feet everywhere
within the Landfill Phase 4 footprint
TN Mai 2025 GW separation
48
44
40
36
32
28
24
20