1812_DukeMarshall_ ILF_Ph5 Hydrogeo_Investigation_WP_FID1891114_20240731

(' DUKE
ENERGY-.
July 31, 2024
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: Hydrogeological and Geotechnical Field Investigation Work Plan
Marshall Industrial Landfill No.1, Phase 5
Permit No.: 1812-INDUS
Marshall Steam Station
Terrell, North Carolina 28682
Dear Ms. Moutos,
525 South Tryon Street
Charlotte, NC 28202
Duke Energy Carolinas (Duke Energy) requests approval from the Division of Waste Management
(Division) for conducting hydrogeological and geotechnical investigation within and at the perimeter of the
future Phase 5 (Cell 9) footprint of the Industrial Landfill No.1 (1812-INDUS; ILF) located at the Marshall
Steam Station.
Duke Energy is actively preparing a permit to construct application for Phase 5 of the ILF. To support the
landfill design, additional subsurface exploration (investigation) to assess geologic/hydrogeologic and
general geotechnical characteristics is planned within and at the perimeters of future Phase 5. The
additional borings and piezometers part of this investigation would be used to supplement existing boring
data and piezometers/monitoring wells installed. The attached work plan provides a description of the
investigation.
Installation of piezometers would be supervised by qualified geotechnical field support that is under the
direct supervision of and in contact with a Licensed Geologist. Actual locations will be determined based
on field conditions and approved by Duke Energy and a Licensed Geologist. Piezometers would be installed
and extended by a North Carolina licensed well contractor in accordance with subchapter 02C of the North
Carolina Administrative Code. Duke Energy will provide boring logs, well construction logs, and well
abandonment logs to the Division upon completion of the field work.
If you need additional information regarding this request do not hesitate to email or call me at
Ashley. [e-mail] or [phone].
Regards,
Ashley Healy, P.G.
Environmental Services
Attachments: Hydrogeological and Geotechnical Field Investigation Work Plan (AECOM, July 2024)
cc (via e-mail): Deana Yitbarek, NCDEQ
Sherri Stanley, NCDEQ
Scott Saunders, Duke Energy
www.duke-energy.com Page 1 of 2

Jake Muessen, Duke Energy
Anne Davin, Duke Energy
Tyler Hardin, Duke Energy
Kim Witt, Duke Energy
Ryan Doyle, AECOM
John Bove, AECOM
www.duke-energy.com Page 2 of 2

DUKE ENERGY
MARSHALL STEAM STATION
INDUSTRIAL LANDFILL NO 1 EXPANSION
DESIGN AND PERMITTING (PHASE 5)
HYDROGEOLOGIC AND GEOTECHNICAL FIELD INVESTIGATION
FIELD INVESTIGATION WORK PLAN (REV 0)
CATAWBA COUNTY, NORTH CAROLINA
Prepared for
DUKE
ENERGY
Duke Energy Carolinas, LLC
400 South Tryon Street
Charlotte, North Carolina 28202
July 31, 2024
Prepared by
ASCOM
5438 Wade Park Blvd. Suite 200
Raleigh, North Carolina 27607

AECOM July 31, 2024
Duke Energy — Marshall Steam Station
ILF Phase 5 Expansion Design and Permitting — Hydrogeologic and Geotechnical Field Investigation
TABLE OF CONTENTS
1. INTRODUCTION.............................................................................................................1
2. PROPOSED HYDROGEOLOGIC AND GEOTECHNICAL FIELD INVESTIGATION ...... 1
2.1 Exploration of the Proposed Landfill Expansion................................................................. 1
2.2 Proposed Laboratory Testing............................................................................................. 3
3. REPORTING...................................................................................................................4
4. SAFETY..........................................................................................................................4
5. FIELD CREW..................................................................................................................4
6. SCHEDULE.....................................................................................................................4
Tables
Table 1 Summary of Proposed Soil Boring and Piezometer Locations
Figures
Figure 1 Site Vicinity Map - Aerial
Figure 2 Proposed Instrumentation Plan
AOcom

Marshall Steam Station July 31, 2024
ILF Phase 5 Expansion Design and Permitting — Hydrogeologic and Geotechnical
Field Investigations Work Plan (Rev.0)
1. INTRODUCTION
This Work Plan provides a description of the proposed subsurface exploration (investigation) to
assess geologic/hydrogeologic and general geotechnical characteristics to support the design
and permitting of the planned Phase 5 expansion of the Industrial Landfill (ILF) No. 1 at the
Marshall Steam Station in Catawba County, North Carolina. The investigation will be used to
analyze existing conditions beneath the proposed landfill cell, obtain groundwater
measurements to design and demonstrate separation between the base of the landfill and the
groundwater table, determine the hydrogeologic characteristics of the subsurface soils, and
support geotechnical design of the proposed landfill cell. Figure 1 presents a Site Vicinity Map.
The subsurface exploration and hydrogeologic study will comply with 15A NCAC 1313.504(c)(3)
and support the permitting of the lateral expansion of the ILF. For the Permit to Construct (PTC),
exploration is required to characterize the subsurface conditions as well as groundwater levels.
The design of the Phase 5 Expansion will be based upon measured groundwater levels and the
measured seasonal high groundwater table (SHGWT).
The Phase 5 Expansion will be designed to tie into adjacent Phases 2 and 4 as shown in Figure
2.
The main purposes of the proposed field exploration are summarized below:
- Obtain data to facilitate calculation of the average depth to groundwater and groundwater
flow direction/gradient within the proposed investigation area, to include SHGWT;
Classify soils and formation(s) and measure geotechnical properties;
Evaluate the depth to bedrock; and,
Gather additional information to support the understanding of subsurface conditions.
2. PROPOSED HYDROGEOLOGIC AND GEOTECHNICAL FIELD INVESTIGATION
2.1 Exploration of the Proposed Landfill Expansion
AECOM proposes to drill 5 additional borings in the ILF Phase 5 Expansion area to support the
PTC application. AECOM plans to extend borings to the top of bedrock or a maximum depth of
60-ft. Borings will be converted to piezometers with estimated depths ranging from 15 ft to 35 ft
below ground surface (bgs). Estimated depths are based on historic borings conducted in and
around Phase 5. These borings, and the historic borings, will be used to classify soils and
measure geotechnical properties as well as evaluate the depth to bedrock. Proposed boring
locations are shown in Figure 2. The five proposed piezometers will be used in conjunction with
existing piezometers located in the general expansion area to develop the potentiometric
surface for Phase 5.
Table 1 (next page) provides a summary of the planned borings and piezometers discussed
above.

Marshall Steam Station July 31, 2024
ILF Phase 5 Expansion Design and Permitting — Hydrogeologic and Geotechnical
Field Investigations Work Plan (Rev.0)
Table 1 — Summary of Proposed Soil Boring and Piezometer Locations
Est. Depth of
Northing'
Easting'
Est. Boring
Water (based
Est. Piezometer
Test ID
(ft)
(ft)
Depthi
on existing
Depth
(ft. bgs)
data)
(ft. bgs)
ft. bgs)
CLF24-501
685110.625
1412770.224
32
10
32
CLF24-502
685144.642
1412487.514
17
5
17
CLF24-503
685347.843
1412460.855
27
13
27
CLF24-504
685599.041
1412287.682
30
27
30
CLF24-505
686126.539
1412168.559
27
25
27
Note:
(1) Proposed boring locations are approximate. As -drilled locations will be surveyed after drilling.
(2) Estimated Boring Depth is based on the estimated depth to top of rock. Borings will extend to top of rock or
60-ft, whichever is shallower.
Proposed boring locations are anticipated to be staked 1 week prior to drilling. Duke Energy will
clear access to the boring locations, as needed, prior to the commencement of field work. As of
this time, AECOM anticipates that no clearing will be required to access the proposed
piezometer locations. Duke Energy will contract with a subsurface utility locating firm, to clear
each proposed boring location for underground utilities in accordance with Duke Energy
procedures.
AECOM is subcontracting SAEDACCO, a North Carolina licensed drilling contractor, to conducl
the drilling phases of the investigation using a drill rig that can perform boring and piezometer
installation. An AECOM geologist or engineer will oversee the work. The proposed drilling
program will be completed by SAEDACCO using Hollow Stem Auger (HSA) Methods. Standard
penetration tests (SPT), as specified in ASTM D-1586-84, will be used to collect soil samples
continuously for the first 10 ft of each boring below the natural soil surface, and then at five-foot
intervals until SPT refusal is encountered. Refusal will be defined using the objective ASTM
standard, ASTM D-1586-84, as 100 SPT blows per foot. Soil samples will be placed in a
sealable plastic bag or jar and saved for geotechnical analysis. An AECOM geologist or
engineer will log each borehole for lithology and collect soil samples for analyses at a
geotechnical testing laboratory.
Each piezometer will be installed and constructed in accordance with 15 NCAC 02C.0108.
Standpipe piezometers will consist of one 10-foot long, 0.010-inch machine -slotted, 2-inch ID,
Schedule 40 PVC well screen and 2-inch ID, Schedule 40 PVC riser pipes placed at the bottom
of the boring. The annular space around the well screen will be filled with graded sand at least 2
feet above the top of the well screen. A minimum 3-foot thick layer of bentonite will be placed
over the sand and hydrated. The remaining annular space will be filled with grout to the ground
surface. Each piezometer will be completed with a locking, steel stick up well casing protected
Pa

Marshall Steam Station July 31, 2024
ILF Phase 5 Expansion Design and Permitting — Hydrogeologic and Geotechnical
Field Investigations Work Plan (Rev.0)
by 4 bollards in a 2'x2' concrete pad. A 5-foot length of well screen may be used in lieu of the
10-foot screen based on field judgement. In accordance with 15 NCAC 02C.0108, in the event
of a shallow water table (less than 5 feet below grade measured at the 0-hour reading or 24-
hour reading), a minimum 6-inch sand pack above the screen, a minimum 6-inch-thick seal, and
at least one foot of grout will be used.
It is assumed that any waste (soils or water) created during drilling activities will be thinly spread
in the vicinity of the drilling location. After completion of the field investigation, the boring
locations will be surveyed by a North Carolina licensed surveyor, subcontracted by AECOM.
Undisturbed soil samples may be collected based upon observations made during drilling
activities using Shelby tubes in accordance with ASTM D 6519. If Shelby tube samples are
collected, the samples will be sealed using expandable caps. Undisturbed samples will be
collected through soil borings offset approximately 5-feet from the original boring location. These
offset borings will be backfilled with grout upon completion.
A boring/construction log will be prepared by the onsite AECOM representative(s) to provide a
detailed record of each boring. As mentioned in the previous section, field logs will be prepared
during the field activities and will be completed as the exploration progresses.
AECOM will perform slug testing on the five (5) newly installed piezometers to determine the
hydraulic conductivity and obtain estimates of the hydrogeologic properties of the uppermost
aquifer. Slug testing will occur after drilling has been completed. The slug tests will be monitored
using down -well pressure transducers and data -loggers to record head pressure converted to
water levels. Water levels will be measured using an electronic water level meter and the data
manually recorded during the piezometer recovery tests. Upon completion of the slug tests,
transducers will be installed in each piezometer to obtain groundwater measurements.
2.2 Proposed Laboratory Testing
A laboratory testing program will be implemented and focused on characterizing the index
properties (moisture content, gradation, and plasticity) of the subsurface soils. AECOM will
subcontract with a soils laboratory to perform the testing.
The laboratory testing program will include conducting the following, but will be subject to
change based on actual field conditions encountered and samples retrieved:
- Grain Size Distribution (ASTM D6913)
- Hydrometer (ASTM D7928)
- Atterberg Limits (ASTM D4318)
- Specific Gravity (ASTM D854)
- Moisture Content (ASTM D2216)
Samples will be selected for lab testing after the completion of field investigation and review of
preliminary field data. Some of the above tests may not be performed if the soil types are not
appropriate for those tests.
Cl

Marshall Steam Station July 31, 2024
ILF Phase 5 Expansion Design and Permitting — Hydrogeologic and Geotechnical
Field Investigations Work Plan (Rev.0)
3. REPORTING
The findings from the investigation for ILF Phase 5 will be included in the Design Hydrogeologic
Report and the PTC Engineering and Facility Plan.
Substantial changes to or deviations from the Work Plan will be submitted to NCDEQ for review
and approval as required.
4. SAFETY
AECOM maintains a site -specific Environmental Health and Safety Plan (EHASP) to address
the safety needs of the planned fieldwork to be completed. The EHASP includes individual job
hazard analyses (JHAs) for the tasks planned for the proposed field investigation. The EHASP
also addresses environmental site concerns related to the fieldwork. The EHASP includes
Safety Data Sheets (SDS) sheets for materials used at MSS projects in the past or planned to
be used during these site activities. A copy of the EHASP will be kept with the AECOM field
crews during the field activities. Updates to the EHASP will be made to comply with the
requirements of the Readiness Review package.
5. FIELD CREW
AECOM will assign one field professional to oversee drilling, piezometer installation, and survey
activities. AECOM will direct the drill crew, log borings, collect samples, and oversee piezometer
installation as well as manage the day-to-day site safety and coordination activities. The field
professional will act as the Site Safety Officer (SSO) throughout the investigation.
6. SCHEDULE
AECOM assumes the field work will require 7 (non-consecutive) days to complete, including
advancing the borings, installing piezometers, surveying the as -built piezometers, and
conducting slug tests. Work will start after regulatory and Duke Energy approvals are received
and safe access to the boring locations is established.
C!

Marshall Steam Station July 31, 2024
ILF Phase 5 Expansion Design and Permitting — Hydrogeologic and Geotechnical
Field Investigations Work Plan (Rev.0)
FIGURES

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0 INCHES 1 2 3 TENTHS 10 20 30 4 5 6 1
REV. 0
_LE END
EXISTING SITE FEATURE (APPROXIMATE)
DUKE ENERGY PROPERTY BOUNDARY
LANDFILL LIMITS OF WASTE
ILF BOUNDARY
LANDFILL AREA - FUTURE PHASE 5
1. THE AERIAL PHOTOGRAPH WAS OBTAINED FROM BING (MICROSOFT CORPORATION, 2020).
2. RECENT MODIFICATIONS TO THE ILF, ASH BASIN, INCLUDING REMOVAL OF CCR, CONSTRUCTION OF
STORMWATER FACILITIES, ACCESS ROADS AND GROUNDWATER MONITORING/REMEDIATION SYSTEMS,
MAY NOT BE REFLECTED IN AERIAL PHOTOGRAPH.
0 500 1000 1500
GRAPHIC SCALE (IN FEET)
SITE VICINITY MAP - AERIAL
MARSHALL STEAM STATION
INDUSTRIAL LANDFILL NO. 1 PHASE 5 EXPANSION
CATAWBA COUNTY, NORTH CAROLINA
FOR ISSUED FOR REVIEW
SCALE: AS SHOWN DES: RLP
DUKE
DWG TYPE: .DWG DFTR : MCS
JOB NO:
60697246 CHKD: RPD
ENERGY DATE: 07/20/2024 ENGR : RPD
_ FILENAME: APPD: JAB
DWG SIZE DRAWING NO. REVISION
ANSI D FIGURE 1 p
22.0"x34.0"
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LEGEND
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♦ PROPOSED AECOM SOIL BORING AND PIEZOMETER LOCATION
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0 INCHES 1 2 3 TENTHS 10 20 30 4 5
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PROPOSED INSTRUMENTATION PLAN
MARSHALL STEAM STATION
♦� '�. INDUSTRIAL LANDFILL NO. 1 PHASE 5 EXPANSION
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CATAWBA COUNTY, NORTH CAROLINA
' FOR ISSUED FOR REVIEW
SCALE: AS SHOWN DES: RLP
_ DUKE
1• � DWG TYPE: .DWG DFTR: MCS
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JOB NO: 60697246 CHKD: RPD
ENERGY DATE: 07/20/2024 ENGR : RPD
FILENAME: APPD: JAB
DWG SIZE DRAWING NO. REVISION
ANSI D FIGURE 2 0
22.0"x34.0"
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