Marshall Data Gap Evaluation TM

1610
synTerra
TECHNICAL MEMORANDUM
Date: November 14, 2018 File: 1026.18.06N
To: Tyler Hardin (Duke Energy)
Cc: Kathy Webb (SynTerra)
From: Brian Wilker, P.G. ��J_
Subject: Data Gap Evaluation Work Plan — Marshall Steam Station
Introduction
Duke Energy Carolinas, LLC (Duke Energy) owns and operates the Marshall Steam
Station (MSS, Plant, or Site) in Terrell, North Carolina. The MSS, which encompasses
approximately 1,446 acres, began operation as a coal-fired electricity -generating facility
in 1965. The Plant currently contains four active coal combustion units. The MSS ash
basin, located north of the Plant, contains ash generated from the historic and active
coal combustion at the Site (Figure 1). Fly ash and bottom ash were sluiced to the ash
basin from approximately 1965 until 1984. Fly ash precipitated from flue gas and
bottom ash collected in the bottom of the boilers were sluiced to the ash basin using
conveyance water withdrawn from Lake Norman. Since 1984, fly ash has mainly been
disposed of in the on -Site Dry Ash Landfills and the sluicing of bottom ash to the ash
basin has continued.
In addition to the on -Site Dry Ash Landfills, a Structural Fill (also known as the PV
Structural Fill) consisting of fly ash and bottom ash was constructed under the
structural fill rules found in 15A NCAC 13B .1700 et seq. (Reference No. CCB0031), as
well as Duke Energy's Distribution of Residuals Solids Permit issued by the former
North Carolina Department of Environment and Natural Resources (NCDENR)
Division of Water Quality (DWQ). The PV Structural Fill is located adjacent to, and
partially on top of, the northwest portion of the ash basin and is unlined (Figure 1).
The Industrial Landfill No. 1 (ILF) (NCDEQ Permit No. 1812-INDUS-2008) is located
adjacent to the north portion of the ash basin (Figure 1). The subgrade for portions of
this landfill were constructed of fly ash under the structural fill rules found in 15A
NCAC 13B .1700 et seq. (Reference No. CCB0072). The landfill was constructed over
portions of residual material and over portions of the unlined ash basin.
Groundwater and soil assessment activities proposed for these potential additional
source areas, other than the ash basin, are described herein.
P: \ Duke Energy Carolinas \ 18. MARSHALL \ 06.EHS CAMA Compliance Support \ 06N. Data Gap Evaluation Work
Plan\Data Gap Work Plan\Marshall Data Gap Evaluation TM.docx

Data Gap Evaluation Work Plan November 14, 2018
Duke Energy Carolinas, LLC - Marshall Steam Station
Page 2 of 5
Regulatory Background
In 2014, The North Carolina General Assembly passed the Coal Ash Management Act
(CAMA). CAMA required owners of a coal combustion residuals (CCR) surface
impoundment to conduct detailed assessment of site groundwater within and
surrounding the CCR surface impoundment.
During the CAMA Comprehensive Site Assessment (CSA), the primary source of CCR-
related constituents in groundwater and soil at the Site was identified as the ash
contained within the ash basin. One well cluster (AB-20S/D) was installed through the
PV Structural Fill during CAMA-associated fieldwork. Other groundwater monitoring
wells were installed west (GWA-4S/D) and south (AB-17S/D) of the ILF during the
CAMA field activities. Two existing wells (MW-4/D), located off the southeast corner of
the ILF, were used in the National Pollutant Discharge Elimination System (NPDES)
groundwater monitoring network, which is no longer active.
Because of boron's mobility, it is commonly used as an indicator of CCR effects on
groundwater. Boron concentrations detected in ash pore water within the PV Structural
Fill at AB-20S are elevated (78,900 µg/L in August 2018). Additionally, CAMA
assessment data indicated several constituents of interest identified in the updated
CAMA CSA (e.g. cobalt and strontium) in groundwater samples at concentrations
uncharacteristic of Site background groundwater. Potential groundwater effects from
the PV Structural Fill and ILF subgrade Structural Fill would eventually coincide with
the known groundwater plume from the ash basin. Therefore, these areas are being
evaluated as data gaps under CAMA regulation.
Station Description
Coal-fired power generation began at MSS in 1965 and remains active. CCRs have been,
and continue to be, sluiced to the ash basin system located north of the power
generation plant. Sluicing operations are anticipated to cease in 2019. The Site contains
several ash management areas, most of which are closed landfills under corresponding
NCDEQ Solid Waste Section permits. The ash basin and ILF remain active ash
management areas at the Site. Active sluicing, which contributes to free-standing water
within the ash basin, is controlled downgradient by the ash basin dam and the NPDES
outfall/discharge to Lake Norman (east side of ash basin).
The topography and corresponding potentiometric surface at the Site generally slope
downward from the northwest to the southeast toward Lake Norman. Slight variations
in localized groundwater flow direction may exist, but flow is predominantly northwest
to southeast. The Site layout is shown on Figure 1.
P: \ Duke Energy Carolinas \ 18. MARSHALL \ 06.EHS CAMA Compliance Support \ 06N. Data Gap Evaluation Work
Plan\Data Gap Work Plan\Marshall Data Gap Evaluation TM.docx

Data Gap Evaluation Work Plan November 14, 2018
Duke Energy Carolinas, LLC - Marshall Steam Station
Data Gap Evaluation Objectives
Objectives of the data gap evaluations include:
Page 3 of 5
• Characterization of inorganic constituents associated with the PV Structural
Fill and ILF subgrade Structural Fill area soils
• Characterization of inorganic constituent concentrations in shallow, deep,
and bedrock groundwater along the downgradient perimeters of the PV
Structural Fill and ILF subgrade Structural Fill area
• Comparison of inorganic constituent concentrations associated with the PV
Structural Fill and ILF subgrade Structural Fill areas soil and groundwater
with Site background concentrations
Soil Assessment
Soils will be sampled and analyzed for inorganic parameters to determine whether they
are a potential secondary source of constituents that can leach into underlying
groundwater. Soil samples will be collected from five locations proposed for
monitoring well installations (Figure 1). Three locations are proposed for the PV
Structural Fill area and two locations are proposed for the ILF subgrade Structural Fill
(Table 1).
Soil samples will be collected at approximately 2-foot intervals from ground surface to
the top of the groundwater table [approximately 10 feet to 15 feet below ground surface
(bgs)] at proposed locations around the PV Structural Fill (Table 1). Soil samples will
be collected at approximately 5-foot intervals from ground surface to the top of the
groundwater table (approximately 40 feet bgs) at proposed locations around the ILF
subgrade Structural Fill (Table 1). An additional soil sample will be collected below the
water table within the new shallow (S) and deep (D) well screen intervals at each
location (shallow only at ILF-2).
Soil samples will be analyzed for inorganic parameters listed on Table 2. Where
applicable, soil samples collected from surficial zones (2 feet to 3 feet bgs) and
immediately above the water table will also be analyzed using synthetic precipitation
leaching procedure (SPLP) for leaching potential.
The quality of continuous cores produced for subsurface characterization purposes is of
high importance; therefore, sonic drilling is recommended as the method of installation
for the data gap evaluation wells. The boreholes will be properly flushed to remove
fluids and cuttings prior to the installation of the monitoring wells. As recommended
by NCDEQ, Duke/SynTerra will consult closely with drillers to use appropriately sized
P: \ Duke Energy Carolinas \ 18. MARSHALL \ 06.EHS CAMA Compliance Support \ 06N. Data Gap Evaluation Work
Plan\Data Gap Work Plan\Marshall Data Gap Evaluation TM.docx

Data Gap Evaluation Work Plan November 14, 2018
Duke Energy Carolinas, LLC - Marshall Steam Station Page 4 of 5
filter packs and screens. Continuous soil cores, collected from the ground surface to the
top of bedrock, will serve these purposes:
• Document the underlying stratigraphy.
• Identify the depth where the water table and transition zone are encountered,
and the thickness of the transition zone (with the exception of ILF-2S).
• Facilitate well construction design.
• Collect samples from a depth corresponding approximately with the middle of
the well screens of shallow and deep zone wells.
Groundwater Assessment
Nine groundwater monitoring wells that would be used to characterize groundwater in
the shallow, deep, and bedrock groundwater flow zones along the downgradient
(eastern) perimeter of the PV Structural Fill (Figure 1; Table 1) are proposed for
installation. Groundwater in soil and saprolite material is considered to be in the
shallow flow zone. Groundwater within partially weathered rock or transition zone
material underlying the shallow zone and overlying competent bedrock is considered to
be in the deep flow zone. The bedrock flow zone is considered competent bedrock with
occasional water -producing fractures, typically encountered within the top 50 feet of
competent rock. Wells will be installed as clusters (PVSF-1S/D/BR through PVSF-
3S/D/BR). It is proposed that each of those clusters would consist of one shallow (S), one
deep (D), and one bedrock (BR) groundwater monitoring well as conditions allow. The
total number of wells installed at each location may vary depending on conditions
encountered during drilling activities (i.e. insufficient transition zone thickness for a
well screen).
Four groundwater monitoring wells that would be used to characterize groundwater in
the shallow, deep, and bedrock groundwater flow zones near the ILF subgrade
Structural Fill (Figure 1; Table 1) are proposed for installation. One well cluster (ILF-
1S/D/BR) downgradient (south) of the ILF is proposed. That well cluster would serve as
a replacement for the AB-17 well cluster (the abandonment of which is expected in Q4
2018 or Q12019). As requested by the NCDEQ Mooresville Regional Office (MRO), one
shallow well north of the ILF is proposed.
Additional proposed well installation details are provided on Table 1. Specific well
locations may be shifted depending on access and field conditions at the time of
installation. Groundwater samples will be analyzed for inorganic constituents listed on
Table 3.
P: \ Duke Energy Carolinas \ 18. MARSHALL \ 06.EHS CAMA Compliance Support \ 06N. Data Gap Evaluation Work
Plan\Data Gap Work Plan\Marshall Data Gap Evaluation TM.docx

Data Gap Evaluation Work Plan
November 14, 2018
Duke Energy Carolinas, LLC - Marshall Steam Station
Page 5 of 5
Data Gap Evaluation Results
Results of the data gap evaluation activities will be provided in the Corrective Action
Plan (CAP) report. It is anticipated that soil data and two rounds of groundwater
sample analytical data will be part of the data evaluation in the CAP. Conclusions
based on data evaluation would also be provided.
ATTACHMENTS:
Figure 1 Proposed Data Gap Evaluation Locations
Table 1 Proposed Data Gap Evaluation Locations
Table 2 Soil Analytical Methods
Table 3 Groundwater Analytical Methods
P: \ Duke Energy Carolinas \ 18. MARSHALL \ 06.EHS CAMA Compliance Support \ 06N. Data Gap Evaluation Work
Plan\Data Gap Work Plan\Marshall Data Gap Evaluation TM.docx

Data Gap Evaluation Work Plan
November 14, 2018
Duke Energy Carolinas, LLC - Marshall Steam Station
ATTACHMENTS
P: \ Duke Energy Carolinas \ 18. MARSHALL \ 06.EHS CAMA Compliance Support \ 06N. Data Gap Evaluation Work
Plan\Data Gap Work Plan\Marshall Data Gap Evaluation TM.docx

9
�p
9°..
Ian 7L� i�� 2SiLL•7L':
AB-20S/D '.
PV STRUCTURAL
FILL
- AI
r� f
WA-12S/D/BR �.
a
RPY�Rt
r
9 � 1
- vim' � / •
- I ♦ / .row Milt
171. • Y .
ILFAS/D • �� • i + f
SL/D/BR ASH LANDFILL ■
(PHASE II) . t •, MW-5
AL-2S/D/BR/BRL+ 3 _
- CCR-16S/D r...
GWA-TS/D
MW 2 CCR-1-r+5/n acN t aNnvu I •nAi e.cintoo
I MB-12S/SL/D/BR
_ AB-101
- AB-9S/D/BR
■ ,r
CCR-12S/D
q ACCESS ROADr
STRUCTURAL ASH BASIN
FILL
MIS-10 M W--i
FGD RESID MW-9.
LANDFILL AB-3S/D {
MS-1� AB-2S�
_ ♦ rCCR-2�
CCR-1 S/D
MS-12
GWA-1SIDIBRr
e
N ♦ 1
A - /
.0000,
Ps
o .
LEGEND
I
'�♦. PROPOSED MONITORING WELL/ O
SOIL SAMPLING LOCATION
EXISTING MONITORING WELL
f •---- ASH BASIN WASTE BOUNDARY
• — - — ..ASH BASIN COMPLIANCE BOUNDARY
LANDFILL BOUNDARY
r
+ - STRUCTURAL FILL BOUNDARY
t-7 LANDFILL COMPLIANCE BOUNDARY
C-. DUKE ENERGY CAROLINAS MARSHALL PLANT
i/ — - - ' SITE BOUNDARY
•
�.:Y.
NOTES:
?..
PROPOSED WELL LOCATION SHOWN ARE APPROXIMATED. EXACT WELL LOCATIONS
l
WILL BE DETERMINED BASED ON ACCESS AND FIELD CONDITIONS AT THE TIME OF
WELL INSTALLATION.
•
•
ti
PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY CAROLINAS.
I
AERIAL PHOTOGRAPHY OBTAINED FROM GOOGLE EARTH PRO ON JULY 26, 2018.
�.•;
■
IMAGE COLLECTED ON MATCH 30, 2018.
yl
r
DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD83/2011).
d
600 soo 0 600 1,200
FIGURE 1
GRAPHIC SCALE IN FEET
PROPOSED DATA GAP EVALUATION LOCATIONS
synTerra
MARSHALL STEAM STATION
148 RIVER STREET, SUITE 220
GREENVILLE, SOUTH CAROLINA 29601
PHONE 864A21-9999
DUKE ENERGY CAROLINAS, LLC
(' DUKE
�w.svnterracoracom
TERRELL, NORTH CAROLINA
ENERGY.
PROJECT MANAGER: GB. WILKER DATE:11/06/2018
CAROLINAS
CHECKED BY: B. WILKER
P:\Duke Enerav Pro ress.1026\00 GIB BASE DATA\Marshall\Ma
dots\MISC\Fi 01 - DataGap Pro osedWells 20181105.mxd

TABLE 1
PROPOSED DATA GAP EVALUATION LOCATIONS
MARSHALL STEAM STATION
DUKE ENERGY CAROLINAS, LLC, TERRELL, NC
Initial Purpose
Well ID
Proposed Screen
Interval'
(ft bgs)
Comments 2
Industrial Landfill
No. 1
ILF-1S
30-40
Estimated depths based on AB-17D
boring log
ILF-1D
80-90
ILF-113R
120-130
ILF-2
30-40
PVSF-1S
15-25
Estimated depths based on AB-6
cluster boring logs
PVSF-1 D
40-50
PVSF-1BR
90-100
PV Structural Fill
PVSF-2S
20-30
Estimated depths based on AB-15
cluster boring logs
PVSF-2D
55-65
PVSF-2BR
90-100
PVSF-3S
10-20
Estimated depths based on GWA-3
cluster boring logs
PVSF-3D
35-45
PVSF-3BR
60-70
Notes:
1 Proposed screened intervals are estimated based on nearby borings/wells that have been previously installed and are
subject to change based on field observations.
2 Stratigraphy characterization and sub -surface soil sampling is best accomplished for the anticipated subsuface
conditions at the site by use of rotosonic drilling methods.
The actual number of wells to be installed at each location are subject to change based on field observations
P:\Duke Energy Carolinas\18. MARSHALL\06.EHS CAMA Compliance Support\06N. Data Gap Evaluation Work Plan\Data Gap Work Plan\
Table 1 Proposed Data Gap Evaluation Locations Page 1 of 1

TABLE 2
SOIL ANALYTICAL METHODS
MARSHALL STEAM STATION
DUKE ENERGY CAROLINAS, LLC, TERRELL, NC
INORGANIC COMPOUNDS
UNITS
METHOD
Aluminum
mg/kg
EPA 6010D
Antimony
mg/kg
EPA 6020B
Arsenic
mg/kg
EPA 6020B
Barium
mg/kg
EPA 6010D
Beryllium
mg/kg
EPA 6010D
Boron
mg/kg
EPA 6010D
Cadmium
mg/kg
EPA 6020B
Calcium
mg/kg
EPA 6010D
Chloride
mg/kg
EPA 9056A
Chromium
mg/kg
EPA 6010C
Cobalt
mg/kg
EPA 6020A
Copper
mg/kg
EPA 6010C
Iron
mg/kg
EPA 6010C
Lead
mg/kg
EPA 6020B
Magnesium
mg/kg
EPA 6010D
Manganese
mg/kg
EPA 6010C
Mercury
mg/kg
EPA 7471 B
Molybdenum
mg/kg
EPA 6010D
Nickel
mg/kg
EPA 6010C
Nitrate as Nitrogen
mg/kg
EPA 9056A
pH
Su
EPA 9045D
Potassium
mg/kg
EPA 6010D
Selenium
mg/kg
EPA 6020B
Sodium
mg/kg
EPA 6010D
Strontium
mg/kg
EPA 6010D
Sulfate
mg/kg
EPA 9056A
Thallium (total, low level)
mg/kg
EPA 6020B
Total Organic Carbon
mg/kg
EPA 9060
Vanadium
mg/kg
EPA 6020B
Zinc
mg/kgmg/kg
EPA 6010C
Prepared by: RBI Checked by: WJW
Notes•
1. Soil samples to be analyzed for Total Inorganics using USEPA Methods 6010/6020 and pH using USEPA Method 9045, as noted above.
2. Ash samples to be analyzed for Total Inorganics using USEPA Methods 6010/6020 and pH using USEPA Method 9045; select ash
samples will also be analyzed for leaching potential using SPLP Extraction Method 1312 in conjunction with USEPA Methods 6010/6020.
3. Analytical methods and reporting limits as presented were applicable at time of CSA field implementation in 2015. Analytical methods
and reporting limits are updated periodically and applied as appropriate.
meq/100g - millequivalents per 100 grams
mg/kg - Milligrams per kilogram
my - Millivolts
S.U. - Standard Unit
P:\Duke Energy Carolinas\18. MARSHALL\06.EHS CAMA Compliance Support\06N. Data Gap Evaluation Work Plan\Data Gap Work Plan\
Table 2 Soil Analytical Methods Page 1 of 1

TABLE 3
GROUNDWATER ANALYTICAL METHODS
MARSHALL STEAM STATION
DUKE ENERGY CAROLINAS, LLC, TERRELL, NC
PARAMETER RL UNITS METHOD
FIELD PARAMETERS
H
NA
SU
Field Water Quality Meter
Specific Conductance
NA
µS/Cm
Field Water Quality Meter
Temperature
NA
oC
Field Water Quality Meter
Dissolved Oxygen
NA
m L
Field Water Quality Meter
Oxidation Reduction Potential
NA
mV
Field Water Quality Meter
Turbidity
NA
NTU
ality Meter
Ferrous Iron
NA
m L
Field Test Kit
INORGANICS
Aluminum
0.005
m L
EPA 200.7 or 6010D
Antimony
0.001
m L
EPA 200.8 or 6020E
Arsenic
0.001
m L
EPA 200.8 or 6020A
Barium
0.005
m L
EPA 200.7 or 6010C
Beryllium
0.001
m L
EPA 200.8 or 6020A
Boron
0.05
m L
EPA 200.7 or 6010C
Cadmium
0.001
m L
EPA 200.8 or 6020A
Chromium
0.001
m L
EPA 200.8 or 6010C
Cobalt
0.001
m L
EPA 200.8 or 6020A
Copper
0.001
m L
EPA 200.8 or 6020B
Iron
0.01
m L
EPA 200.7 or 6010C
Lead
0.001
m L
EPA 200.8 or 6020A
Manganese
0.005
m L
EPA 200.7 or 6010C
Mercury low level
0.005
n L
1631 ONLY
Molybdenum
0.001
m L
EPA 200.8 or 6020B
Nickel
0.001
m L
EPA 200.8 or 6020B
Phosphorus
0.005
m L
EPA 365.1
Selenium
0.001
m L
EPA 200.8 or 6020A
Strontium
0.005
m L
EPA 200.7 or 6010C
Thallium low level
0.0002
m L
EPA 200.8 or 6020A
Vanadium low level
0.0003
m L
EPA 200.8 or 6020A
Zinc
0.005
m L
EPA 200.7 or 6010C
RADIONUCLIDES
Radium 226
1
1 PQ/L
1EPA 903.1 Modified
Radium 228
1
1 PQ/L
I EPA 904.0/SW846 9320 Modified
Uranium 233 234 236 238
Varies by isotope
I µg/mL
ISW846 3010A/6020A
ANIONS/CATIONS
Alkalinity as CaCO3
5
m L
SM 2320B
Bicarbonate
5
m L
SM 2320
Calcium
0.01
m L
EPA 200.7
Carbonate
5
m L
SM 2320
Chloride
0.1
m L
EPA 300.0 or 9056A
Magnesium
0.005
m L
EPA 200.7
Methane
0.01
m L
RSK 175
Nitrate as Nitrogen
0.01
m -N L
EPA 353.2
Potassium
0.1
m L
EPA 200.7
Sodium
0.05
m L
EPA 200.7
Sulfate
0.1
m L
EPA 300.0 or 9056A
Sulfide
0.1
mg/L
SM4500S2-D
Total Dissolved Solids
25
m L
SM 2540C
Total Organic Carbon
0.1
m L
ism 5310C EPA9060A
Total Suspended Solids
1 2.5
1 m L
ISM 2450D
Prepared by: RBI Checked by: WJW
Notes:
1. Select constituents will be analyzed for total and dissolved concentrations.
2. Analytical methods and reporting limits as presented were applicable at time of CSA field implementation in 2015. Analytical methods and reporting limits are updated periodically and
applied as appropriate.
OC - Degrees Celsius
pS/cm = micro -Siemens per centimeter
mg/L - Milligrams per liter
mg - N/L - Milligrams nitrogen per liter
my - Millivolts
NA - Not analyzed
NTU - Nephelometric turbidity unit
pCi/L - picocuries per liter
RL = reporting limit
S.U. - Standard Unit
ug/mL - micrograms per milliliter
P:\Duke Energy Carolinas\18. MARSHALL\06.EHS CAMA Compliance Support\06N. Data Gap Evaluation Work Plan\Data Gap Work Plan\Table 3 - GW Analytical Methods Page 1 of 1