Additional Source Area Assessment TM_20181129

1610
synTerra
TECHNICAL MEMORANDUM
Date: November 29, 2018 File: 1026.18
To: Tyler Hardin (Duke Energy)
Cc: Kathy Webb (SynTerra)
From: Brian Wilker, P.G. �;J—
Subject: Marshall Steam Station Additional Source Areas Assessment Work Plan
Introduction
Duke Energy Carolinas, LLC (Duke Energy) owns and operates the Marshall Steam
Station (MSS or Site) in Terrell, North Carolina. 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. Coal used for
electricity generation is transported to the Site by railroad and stored on approximately
35 acres north of the power generation plant (coal pile). Gypsum, a byproduct of the
coal combustion process, is stored on approximately 3.5 acres west of the coal pile
(Figure 1). Groundwater and soil assessment activities proposed for the coal pile and
the gypsum storage area are described herein.
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), a source of CCR-related
constituents in groundwater and soil at the Site was identified as the ash contained
within the ash basin. Groundwater monitoring wells were installed east of the coal pile
(GWA-1 cluster) and gypsum pad area (GWA-2 cluster) during CAMA-associated
fieldwork. Additionally, for compliance with the Environmental Protection Agency's
Coal Combustion Residuals (CCR) Rule, wells were installed along the perimeter (north
and east) of the coal pile area (CCR-1, CCR-2, and CCR-3 clusters).
In a letter dated September 8, 2017, the North Carolina Department of Environmental
Quality (NCDEQ) Division of Water Resources provided Duke Energy technical
direction regarding the assessment and corrective action for additional sources at coal
ash facilities. The letter reiterated the rules and requirements outlined in Title 15A
North Carolina Administrative Code (NCAC) Subchapter 02L (02L), which requires
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Additional Source Areas Assessment Work Plan November 29, 2018
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Duke Energy to address groundwater impacts from other potential primary and
secondary sources other than the CCR surface impoundment. For this reason, Duke
Energy understands soils and underlying groundwater at the coal pile area and at the
gypsum storage area to be additional potential sources of inorganic constituents that
will be assessed apart from CAMA.
Station Description
Coal-fired power generation began at MSS in 1965 and remains active. CCR have been,
and continue to be, sluiced to the ash basin system located north of the power
generation plant. It is anticipated that sluicing operations will cease in 2019. Coal used
to fuel power -generating units is transported to the Site by railroad and is stored on
approximately 35 acres north of the power -generation plant and south of the ash basin.
Gypsum, a coal combustion byproduct, is stored on an approximately 3.5-acre lined
concrete pad west of the coal pile area (Figure 1).
The topography and corresponding potentiometric surface at the Site generally slopes
downward from the northwest to the southeast toward Lake Norman. The Site layout is
shown on Figure 1.
Additional Source Area Assessment Objectives
Objectives of the additional source area assessments include:
• Characterization of inorganic constituents associated with soils at and near
the coal pile and soils at the gypsum storage area
• Characterization of inorganic constituent concentrations in shallow and deep
groundwater along the perimeters of the coal pile and gypsum storage area
• Comparison of inorganic constituent concentrations in soil and groundwater
related to source areas with background concentrations
Soil Assessment
Unsaturated soils in the potential source areas will be sampled and analyzed for
inorganic parameters to determine whether they are a secondary source of constituents
that can leach into underlying groundwater. Soil samples will be collected from six
locations proposed for the installation of monitoring wells (Figure 1). Three locations
are proposed for the coal pile area, and three locations are proposed for the gypsum
pad area (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 12 feet below ground surface
(bgs)] at proposed locations surrounding the coal pile (Table 1). Soil samples will be
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Additional Source Areas Assessment Work Plan November 29, 2018
Duke Energy Carolinas, LLC - Marshall Steam Station
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collected at approximately 5-foot intervals from ground surface to the top of the
groundwater table (approximately 25 feet to 30 feet bgs) at proposed locations
surrounding the gypsum storage area (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.
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.
Sonic drilling is recommended as the method of installation for the secondary source
area assessment wells due to the quality of continuous cores produced for subsurface
characterization purposes. The boreholes will be properly flushed to remove fluids and
cuttings prior to the installation of the monitoring wells. As recommended by the
North Carolina Department of Environmental Quality (NCDEQ), Duke/SynTerra will
consult closely with drillers to use appropriately -sized filter packs and screens.
Continuous soil cores will be collected from the ground surface to the top of bedrock
and will serve three purposes:
• Document the underlying stratigraphy.
• Identify the depth where the transition zone is encountered, the thickness of the
transition zone, and where the transition zone well will be screened.
• Collect soil samples from a depth corresponding approximately with the middle
of the well screens of shallow and deep zone wells.
Groundwater Assessment
Six groundwater monitoring wells that would be used to characterize groundwater in
the shallow and deep groundwater flow zones in the coal pile area ("CP") are proposed
for installation (Figure 1; Table 1). 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. Wells will be installed as clusters
(CP-1S/D through CP-3S/D). It is proposed that each of those clusters would consist of
one shallow ("S") and one deep ("D") 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).
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Additional Source Areas Assessment Work Plan
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Duke Energy Carolinas, LLC - Marshall Steam Station
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Six groundwater monitoring wells that would be used to characterize groundwater in
the shallow and deep groundwater flow zones in the gypsum storage area ("GP") are
proposed for installation (Figure 1; Table 1). Wells will be installed as clusters (GP-
1S/D through GP-3S/D). It is proposed that each of those clusters would consist of one
shallow ("S") and one deep ("D") groundwater monitoring well as conditions allow.
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.
Additional Source Areas Assessment Results
Due to the potential plumes from the coal pile and gypsum pad being coincident with
the ash basin, results of the additional source areas assessment activities will be
provided in the Corrective Action Plan (CAP) anticipated for submittal in December
2019. 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 Additional Source Area Assessment Locations
Table 1 Proposed Additional Source Area Monitoring Wells
Table 2 Soil Analytical Methods
Table 3 Groundwater Analytical Methods
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Additional Source Areas Assessment Work Plan
November 29, 2018
Duke Energy Carolinas, LLC - Marshall Steam Station
ATTACHMENTS
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TM.docx

TABLE 1
PROPOSED ADDITIONAL SOURCE AREA MONITORING WELLS
MARSHALL STEAM STATION
DUKE ENERGY CAROLINAS, LLC, TERRELL, NC
Initial Purpose
Well ID
Proposed Screen
Interval'
(ft bgs)
Comments 2
Coal Pile Area
Assessment
CP-1S
10-20
Estimated depths based on CCR-2
cluster boring logs
CP-1D
40-50
CP-2S
30-40
Estimated depths based on CCR-1
cluster boring logs
CP-2D
80-90
CP-3S
30-40
CP-3D
80-90
Gypsum Storage
Area Assessment
GP -IS
25-35
Estimated depths based on GWA-2
cluster boring logs
GP -ID
70-80
GP-2S
25-35
GP-2D
70-80
GP-3S
25-35
GP-3D
70-80
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.
Z Stratigraphy characterization and sub -surface soil sampling is best accomplished for the anticipated
subsuface conditions at the site by use of rotosonic drilling methods.
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Table 1 Source Area Assessment Wells 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/kq
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. Select soil 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
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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
0C
Field Water Quality Meter
Dissolved Oxygen
NA
m /L
Field Water Quality Meter
Oxidation Reduction Potential
NA
mV
I Field Water Quality Meter
Turbidity
NA
NTU
I Field Water Quality Meter
Ferrous Iron
NA
mg /L
IField Test Kit
INORGANICS
Aluminum
0.005
m /L
EPA 200.7 or 6010D
Antimony
0.001
m /L
EPA 200.8 or 6020B
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
I EPA 200.8 or 6020A
Zinc
0.005
m L
EPA 200.7 or 6010C
RADIONUCLIDES
Radium 226
1
Ci/L
EPA 903.1 Modified
Radium 228
1
Ci/L
EPA 904.0/SW846 9320 Modified
Uranium 233, 234, 236, 238
Varies by isotope
µg/mL
SW846 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
mg/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
SM 5310C EPA9060A
Total Suspended Solids
1 2.5
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
µS/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
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