5 MSS CAP Part 2_Appx B_FINAL

Appendix B

This page intentionally left blank

ELECTRIC
01=2'1 I RESEARCH INSTITUTE Memorandum
March 2, 2016
TO: Ed Sullivan and Tyler Hardin, Duke Energy
FROM: Bruce Hensel, EPRI
SUBJECT: MARSHALL MODEL REVIEW
Summary
EPRI has reviewed the revised Marshal model report and files provided by Duke Energy,
HDR Engineering, and the University of North Carolina -Charlotte. The review was
performed by Tim Dale (Intera), with input by Chunmiao Zheng and myself. Based on this
review, it is our opinion that, subject to the caveats below, this model is set-up and meets its
flow and transport calibration objectives sufficiently to meet its final objective of predicting
effects of corrective action alternatives on groundwater quality. The caveat associated with
this opinion is:
• The use of constant concentration boundaries beneath the dry ash landfill, rather than
placing these cells within these facilities, results in greater mass addition to the model
than if modeled using recharge, because lateral flow through these boundaries also
adds concentration to the model. This simulation approach was necessary because the
facilities are above the water table. However, it is conservative because it results in
greater concentration/mass addition to the model than suggested by the site
conceptual model.
Specific Comments
Model Report, Setup, and Calibration
a) Is the objective/purpose of modeling clearly defined?
Yes. The objective and purpose of the modeling is clearly defined in Section 1.2 as
consisting of three main activities: development of a calibrated steady-state flow model of
current conditions, development of a historical transient model of constituent transport
calibrated to current conditions, and predictive simulations of a cap in-place scenario. The
predictive simulation was not considered as part of this review.
b) Is the site description adequate?
Yes. Section 2 of the model report provides a description of the site that is adequate for
evaluating the model for both flow and transport purposes.
c) Is the conceptual model well described with appropriate assumptions?
Yes. The conceptual model section contains subsections discussing hydrogeology, the
source areas, the groundwater flow system, hydrologic boundaries, hydraulic boundaries,

Marshall Model Review
March 2, 2016
Page 2
sources and sinks, a limited discussion of water balance, modeled constituents of interest, and
constituent transport. The CSA report is referenced in describing aquifer properties.
d) Is the numerical model properly set up (steady state or transient; initial condition;
boundary conditions; parameterization; etc)?
i) Appropriateness of the simulator
The use of MODFLOW-NWT and MT3DMS to simulate groundwater flow and contaminant
transport, respectively, are both appropriate for the modeling objectives and represent an
industry standard in choice of simulators. However, MODFLOW-NWT has a limitation in
that it does not enable use of recharge concentrations with MT3DMS. As discussed later, this
effects the model simulation for some sources.
ii) Discretization: temporal and spatial (x -y notably z)
The 40 x 40 foot spatial discretization for this model is adequate to delineate differences in
simulated heads and concentrations for all reasonable calibration and predictive purposes.
For transport simulations, the Courant Number and the Grid Peclet Number can be used to
determine whether discretization is numerically appropriate for a given model. In this model,
transport time steps are automatically calculated by the simulator based on a specified
Courant Number constraint of 1. This ensures that temporal discretization is appropriate for
the spatial discretization of the model.
The Grid Peclet Number (Pe_grid = Al/a) can be used to evaluate whether numerical
dispersion dominates constituent transport based on spatial discretization and physical
dispersion. Grid Peclet numbers preferably less than 2 and no more than 10 are generally
recommended to minimize numerical dispersion.
The lateral discretization (Ax = Ay = 40 feet) coupled with the longitudinal dispersivity of 70
feet for all constituents results in Grid Peclet numbers of 0.57, which fits within the criteria.
The transverse lateral dispersivity of 7 feet results in Grid Peclet numbers of approximately
5.7, which is also within the criterion.
The vertical discretization is more variable than the horizontal discretization. Vertical layer
thickness in the primary transport zone in layers 5, 6, and 7 (saprolite and alluvium) varied
from less than 1 to 38 feet. Vertical dispersivity (az) is 0.7 feet for all constituents, which
results in a grid Peclet number (Pe_grid = Az/av) as high as 54. In layer 8 (transition zone),
thickness ranges from less than 1 to 26 feet, resulting in vertical grid Peclet numbers of 2.5 to
12.5, and in layers 9 and 10 (bedrock) layer thickness is uniformly 100 feet and 430 feet,
respectively, resulting in a vertical grid Peclet numbers gtreater than 100. These values
indicate that numerical dispersion can exert an influence on vertical transport in this model,
particularly in the bedrock layers, and may result in deeper transport than would occur by
dispersion and flow alone.
There may also be some concern that, due to their thickness, any mass transported to layers 9
and 10 will be subject to a large degree of dilution. However, the horizontal hydraulic
conductivity of these layers is an order of magnitude or more lower than overlying layers,
and the only source or sink boundaries in these layers are four wells, set in layer 9 near the

Marshall Model Review
March 2, 2016
Page 3
lateral boundaries of the model. A review of flow vectors indicates that the model predicts
flow from the boundary toward these wells, which suggests that they are not expected to be
affected by constituents added in the source areas. As a result, there is little impetus for mass
to migrate to layers 9 and 10—other than via numerical dispersion—and they are not
expected to have a significant effect on mass transport.
iii) Hydrologic framework –hydraulic properties
The hydrostratigraphy and hydraulic property ranges from the CSA report are discussed in
adequate detail in Section 2 of the model report.
Sorption coefficients used in the transport modeling differed from those presented in the
geotechnical report, but were within published ranges.
iv) Boundary conditions
The upgradient portions of the flow model are laterally bounded by no -flow boundaries
based on natural topographic features. In some cases, boundaries are relatively close to
source areas. However, the potential impact of these boundaries on flow and transport is
minimized by modeling them as no -flow boundaries, rather than constant head boundaries.
Downgradient boundaries consist of constant head boundaries representing Lake Norman and
the unnamed tributary.
Upland streams are represented using drain boundaries, which do not input water to the
model. As a result, the primary source of water to the model is recharge from precipitation
outside the ash basins, and recharge from infiltration within the ash basins. Recharge rates
were initially set based on published documents and adjusted during calibration, which is an
accepted modeling practice. Modeled recharge rates were reasonable for the
hydrostratigraphy of the area and conceptual model.
Modeled recharge within and outside the various source areas was examined. Values were
about 33,000 ft3/d for the source areas, compared to 88,000 ft3/d for the entire model domain
(i.e., recharge from ash basin infiltration constituted approximately 38% of the water input to
the model). These results indicate that groundwater flow for most of the model domain is
derived from recharge from precipitation, and groundwater flow near the ash basins is
appropriately derived from a mixture of recharge from precipitation and infiltration from the
ash basins.
The transport model used constant concentration boundaries to input mass/concentration
from the ash basins. These boundaries were placed in layers 1 through 4 for the active ash
pond and PV structural fill, and in layers 5 and 6 for all other source areas. Recharge was not
used to add concentration to the model. This selection of transport model boundary
conditions has three potential ramifications:
• If constant concentrations cells representing a source are dry, then recharge from
infiltration through the source at that grid position will enter the model with a
concentration of zero, which does not agree with the conceptual model for this
facility. This condition was mitigated by vertically stacking constant concentration

Marshall Model Review
March 2, 2016
Page 4
cells at grid positions representing source areas to assure that they intersected the
water table.
• For the sources simulated by constant concentration cells in layers 5 and 6, lateral
flow can cause addition of mass / concentration to the model that would not occur if
the source area was simulated solely using recharge.
• The placement of constant concentration cells in layers 5 and 6 will inhibit the
model's ability to simulate certain caps, because lateral flow through these constant
concentration cells will continue to add mass/concentration to the model even
though leaching and infiltration may be greatly reduced by capping. Simulation of a
cap with a geomembrane barrier layer remains viable over the long term because
these caps are capable of reducing leachate release to negligible volumes, and can be
simulated by removing the constant concentration cells.
v) Initial conditions in transient simulations
The flow model was calibrated to steady state conditions, where initial conditions are not
relevant apart from numerical convergence, which was achieved. The transient flow model
used for transport modeling was essentially three steady state flow models strung together,
where initial conditions were again not relevant.
Simulation of the main ash basin begins in 1965, with other sources added over time, which
matches the site conceptual model. Outside the source areas, the transient transport model
assumes non -zero initial concentrations in 1965; however, concentration is not added via
boundary conditions to maintain the initial concentrations. As a result, areas of the model that
are not affected by the modeled sources show slowly decreasing "background"
concentrations over time as concentration input via the initial condition is conceptually
flushed out by added (recharge) water with a specified concentration of zero. The effect of
the decreasing background concentrations within model areas affected by the source terms is
conceptually dependent on the where the area lies relative to the source terms. Immediately
downgradient of the source terms, concentrations are dominated by the source terms, and
should not be noticeably affected by the decreasing background concentration. In concept,
concentrations near the peripheries of the modeled plume may show concentration decrease
over time due to the decrease in simulated background. A review of concentration vs time
plots for targets within the boron model showed numerous examples outside the influence of
the source term where concentration decreased during the calibration period; however
reviewed targets within the influence of the source areas showed little concentration decrease
prior to effects of the source, and concentration increases—not decreases—after the source
term began to effect modeled concentration at those points in the model.
vi) Convergence criteria and mass balance errors
The head tolerance in the NWT packages of le -4 is more than adequate in ensuring head
precision for the purposes of the model. The flow model mass balance discrepancy reported
in the output file of 0.00 percent is more than adequate in ensuring minimal flow mass
balance errors. The concentration mass balance discrepancy for MT3DMS was lower than

Marshall Model Review
March 2, 2016
Page 5
0.1 percent for all constituents except thallium, which indicates negligible mass -balance
error. For thallium, the mass balance discrepancy was -1.7%. All of the cumulative mass
balance errors are adequate in ensuring minimal constituent mass balance errors by the end of
the historical simulation.
e) Is the calibration done properly and adequately?
For flow calibration to heads, the Normalized Root Mean Square of the Error is 5.5%
percent, which is below the industry standard of 10 percent (i.e., below 10 percent is
acceptable). The plot of simulated vs. observed heads shows both positive and negative
residuals with very little bias in the residuals.
Comparison of simulated and observed concentrations for each of the COIs is discussed by
constituent. The transport calibration was primarily evaluated based on its ability to simulate
high concentrations where measured concentrations are significantly above background. This
comparison was performed using targets outside of source areas.
Antimony: The model yielded near -background concentrations (< 3 ug/L) at the two targets
with observed antimony concentrations greater than 6 ug/L.
Arsenic: One of two values with observed concentration higher than 10 ug/L had a
concentration higher than 10 ug/L in the calibration results, while one well with an observed
concentration of less than 1 ug/L had a modeled concentration of 12 ug/L.
Barium: The model only yielded one concentration outside the source areas with
concentration higher than background (-160 ug/L). This result was comparable to observed
(325 ug/L modeled vs 450 ug/L observed). The model did not predict concentrations
appreciably higher than background for three other targets with observed concentrations
between 400 and 700 ug/L.
Beryllium: There was only target outside them source areas with an observed concentration
higher than the modeled background value of 1.0, although it was only 1.3 ug/L.
Boron: There were 39 targets with concentrations above background value of 100 ug/L and
all of these were simulated with concentrations above background. For the 45 targets below
background concentrations, 23 were simulated with concentrations higher than background.
Chloride: The model adequately reproduced chloride concentrations lower than 100 mg/L.
Concentrations higher than 100 mg/L were achieved at 1 of 5 targets with observed
concentrations above 100 mg/L.
Chromium: There were only two targets outside the source area with observed chromium
concentrations greater than 20 ug/L, and the model predicted concentrations lower than 20
ug/L for both of these points.
Cobalt: Five targets had observed cobalt concentrations greater than 10 ug/L, and the model
yielded near background (simulated at 2.5 ug/L) concentrations at all five of these targets.
Hexavalent Chromium: With one exception, observed concentrations for hexavalent
chromium concentration were lower than modeled background. The model yielded a near
simulated background result (2.3 ug/L) at this monitoring point.

Marshall Model Review
March 2, 2016
Page 6
Selenium: There were four targets with observed selenium concentrations higher than the
simulated background value of 10 ug/L. The model did not yield concentrations higher than
10 ug/L at any targets outside the source areas.
Sulfate: There were 74 targets with concentrations above background value of 1460 ug/L and
63 of these were simulated with concentrations above background. For the 11 targets below
background concentrations, 10 were simulated with concentrations lower than background.
Thallium: There are no modeled or observed thallium concentrations outside the source areas
greater than the simulated background concentration of 0.5 ug/L.
Vanadium: The model yielded vanadium concentrations at simulated background levels (2.5
ug/L) for at all eight targets where observed concentrations were greater than 10 ug/L.
In summary, the transport calibration varies among the thirteen COIs. Boron and sulfate can
be considered to have a good fit between measured and simulated, as low/high concentration
trends are generally similar between the measured and simulated values. The other COIs had
few targets with concentration higher than background that could be used for calibration
In general, it is difficult to achieve strong concentration match for large numbers of modeled
constituents, particularly if some are affected by geochemical reactions that are not simulated
by MT3DMS. However, the constituents with good concentration match (boron and sulfate)
will enable use of the model for its stated objective.
i) Property/boundary condition correlation —parameter bounds
The flow model was calibrated by adjusting recharge and hydraulic conductivity, an accepted
modeling practice. The transport model was calibrated by adjusting source concentrations
and the areas in which these concentrations occurred, effective porosity, and the distribution
coefficient. The source concentration variations reflect the variable nature of the sources at
the site, and the other adjustments are accepted modeling practice.
ii) Discretization of calibration parameters
Hydraulic conductivity varies by hydrostratigraphic unit, and model layers are used to
differentiate between hydrostratigraphic units. Within a given layer, calibrated hydraulic
properties are either uniform or based on zones of piece -wise constancy, depending on the
properties of each hydrostratigraphic unit and calibration needs of the model. Fractured
bedrock was modeled as an equivalent porous medium with very low effective porosity to
represent the effect of fractures on transport. These are all accepted modeling practices.
Dispersivity (longitudinal, transverse, and vertical) was simulated using a single value for the
entire model domain. Effective porosity was varied by hydrostratigraphic unit, with low
values for fractured media, which is standard modeling practice.
Is the sensitivity analysis conducted and if so, correctly?
i) Sensitivity Analysis approach (look for parameters which maybe insensitive to flow
but not to transport)
Sensitivity testing for the flow model varied horizontal and vertical hydraulic conductivity in
key transport zones, and recharge by 20 percent. This is a reasonable approach for testing

Marshall Model Review
March 2, 2016
Page 7
flow model sensitivity. The transport model sensitivity analysis was not repeated for this
version of the model. We recommend performing the sensitivity analysis for the revised
model.
Model Files:
a) Can the model be run with the input files provided by the developer?
Yes.
b) Do the model results match those presented in the report?
i) Independent check of input data vs. conceptual model/report
Some discrepancies were noted between draft documentation and model inputs. These
discrepancies do not adversely affect the ability of the model to meet its objectives, and we
understand that the documentation will be revised to address the discrepancies.
ii) Check of water balance vs. conceptual model
All water input to the model is via recharge, and as previously noted the majority of water
input to the model is by recharge outside the boundary of the ash pond. Outflows are largely
to the (69%) to interior drain cells representing streams, with most of the remainder to the
constant head cells representing Lake Norman and the unnamed tributary (31%), and less
than 1% to wells. This indicates a model domain that largely reflects the natural flow system,
and that is not overly dominated by lateral boundary effects or infiltration from the ash
ponds.
iii) Independent check of model results vs. those reported
Independently generated model results are consistent with what is described in the report.

This page intentionally left blank

Groundwater Flow and Transport Model
Marshall Steam Station
Catawba County, NC
Investigators:
F)l
HDR Engineering, Inc.
440 S. Church St, Suite 1000
Charlotte, NC 28202
Contributors:
UNC, CHARiMTE
William G. Langley, Ph.D., P.E.
Dongwook Kim, Ph.D.
UNC Charlotte / Lee College of Engineering
Department of Civil and Environmental Engineering
EPIC Building 3252
9201 University City Blvd.
Charlotte, NC 28223
Revised March 1, 2016

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
TABLE OF CONTENTS
1 Introduction............................................................................................................................1
1.1 General Setting and Background...................................................................................1
1.2 Third Party Review.........................................................................................................2
2 Conceptual Model..................................................................................................................2
2.1 Geology and Hydrogeology............................................................................................2
2.2 Hydrostratigraphic Layer Development..........................................................................3
2.3 Ash Management Areas.................................................................................................4
2.3.1 Ash Basin................................................................................................................5
2.3.2 Dry Ash Landfill.......................................................................................................5
2.3.3 FGD Landfill............................................................................................................6
2.3.4 Industrial Landfill No. 1............................................................................................6
2.3.5 Demolition Landfill...................................................................................................6
2.3.6 Asbestos Landfill.....................................................................................................6
2.3.7 Photovoltaic Farm Structural Fill.............................................................................7
2.4 Groundwater Flow System.............................................................................................7
2.5 Hydrologic Boundaries...................................................................................................7
2.6 Hydraulic Boundaries.....................................................................................................7
2.7 Sources and Sinks..........................................................................................................8
2.8 Water Balance................................................................................................................8
2.9 Modeled Constituents of Interest....................................................................................8
2.10 COI Transport.................................................................................................................9
3 Computer Model..................................................................................................................10
3.1 Model Selection............................................................................................................10
3.2 Model Description.........................................................................................................10
4 Groundwater Flow and Transport Model Construction........................................................10
4.1 Model Hydrostratigraphy..............................................................................................11
4.2 Groundwater Vistas Version 6......................................................................................12
4.3 Model Domain and Grid................................................................................................12
4.4 Hydraulic Parameters...................................................................................................13
4.5 Flow Model Boundary Conditions.................................................................................13
4.6 Flow Model Sources and Sinks....................................................................................14
4.7 Flow Model Calibration Targets....................................................................................14

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
4.8
Transport Model Parameters........................................................................................14
4.9
Transport Model Boundary Conditions.........................................................................16
4.10
Transport Model Sources and Sinks............................................................................16
4.11
Transport Model Calibration Targets............................................................................16
5 Model Calibration to Current Conditions..............................................................................16
5.1
Flow Model Residual Analysis......................................................................................16
5.2
Flow Model Sensitivity Analysis....................................................................................17
5.3
Transport Model Calibration and Sensitivity.................................................................18
5.4
Advective Travel Times................................................................................................19
5.5
One Year's Advective Travel Time from Residential Pumping Wells ...........................19
6 Simulations of Closure Scenarios........................................................................................19
6.1
Existing Conditions Scenario........................................................................................19
6.2
Cap -In -Place Scenario.................................................................................................20
7 Closure
Scenario Results....................................................................................................20
7.1
Antimony.......................................................................................................................21
7.2
Arsenic..........................................................................................................................21
7.3
Barium..........................................................................................................................21
7.4
Beryllium.......................................................................................................................22
7.5
Boron............................................................................................................................22
7.6
Chloride........................................................................................................................22
7.7
Chromium.....................................................................................................................23
7.8
Cobalt...........................................................................................................................23
7.9
Hexavalent Chromium..................................................................................................23
7.10
Selenium.......................................................................................................................24
7.11
Sulfate..........................................................................................................................24
7.12
Thallium........................................................................................................................25
7.13
Vanadium.....................................................................................................................25
8 Summary .............................................................................................................................25
8.1
Model Assumptions and Limitations.............................................................................25
8.2
Model Predictions.........................................................................................................26
9 References..........................................................................................................................28

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
TABLES
No table of figures entries found.
FIGURES
Figure 1 Conceptual Groundwater Flow Model/Model Domain
Figure 2 Model Domain North-South Cross section A -A' through Inactive and Active Ash Basins
Figure 3 Model Domain East-West Cross section B -B' through the Active Ash Basin
Figure 4 Flow Model Boundary Conditions
Figure 5 Model Layers 2-4 Recharge Areas and Contaminant Source Zones (Constant
Concentration Cells)
Figure 6 Model Layers 5-7 Contaminant Source Zones (Constant Concentration Cells)
Figure 7 Observation Wells in Shallow Groundwater Flow Layer
Figure 8 Observation Wells in Deep Groundwater Zone
Figure 9 Observation Wells in Bedrock Groundwater Zone
Figure 10 Hydraulic Conductivity Zonation in S Model Layers (Model Layers 2-4)
Figure 11 Hydraulic Conductivity Zonation in M1/M2 Model Layers (Model Layers 5-7)
Figure 12 Modeled Hydraulic Head vs. Observed Hydraulic Head
Figure 13 Hydraulic Potentiometric Head in Shallow Groundwater Zone (Model Layer 6)
Figure 14 Forward Particle Tracking Results
Figure 15 One -Year Reverse Particle Tracking from Residential Wells
Figure 16 Predicted Antimony in Monitoring Well AB -1 S
Figure 17 Predicted Antimony in Monitoring Well AB -2S
Figure 18 Predicted Antimony in Monitoring Well GWA-1 S
Figure 19 Predicted Antimony in Monitoring Well MW -6S
Figure 20 Initial (2015) Antimony Concentrations in Shallow Groundwater Zone
Figure 21 Initial (2015) Antimony Concentrations in Deep Groundwater Zone
Figure 22 Initial (2015) Antimony Concentrations in Bedrock Groundwater Zone
Figure 23 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Shallow
Groundwater Zone
Figure 24 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Deep
Groundwater Zone
Figure 25 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Bedrock
Groundwater Zone
Figure 26 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Shallow
Groundwater Zone
Figure 27 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Deep
Groundwater Zone
Figure 28 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Bedrock
Groundwater
Figure 29 Predicted Arsenic in Monitoring Well AB -1 S
Figure 30 Predicted Arsenic in Monitoring Well AB -2S
Figure 31 Predicted Arsenic in Monitoring Well GWA-1 S
Figure 32 Predicted Arsenic in Monitoring Well MW -6S
Figure 33 Initial (2015) Arsenic Concentrations in Shallow Groundwater Zone
Figure 34 Initial (2015) Arsenic Concentrations in Deep Groundwater Zone
Figure 35 Initial (2015) Arsenic Concentrations in Bedrock Groundwater Zone
Figure 36 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Shallow
Groundwater Zone
iv

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 37 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Deep
Groundwater Zone
Figure 38 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Bedrock
Groundwater Zone
Figure 39 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Shallow
Groundwater Zone
Figure 40 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Deep
Groundwater Zone
Figure 41 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Bedrock
Groundwater Zone
Figure 42 Predicted Barium in Monitoring Well AB -1S
Figure 43 Predicted Barium in Monitoring Well AB -2S
Figure 44 Predicted Barium in Monitoring Well GWA-1 S
Figure 45 Predicted Barium in Monitoring Well MW -6S
Figure 46 Initial (2015) Barium Concentrations in Shallow Groundwater Zone
Figure 47 Initial (2015) Barium Concentrations in Deep Groundwater Zone
Figure 48 Initial (2015) Barium Concentrations in Bedrock Groundwater Zone
Figure 49 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Shallow
Groundwater Zone
Figure 50 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Deep
Groundwater Zone
Figure 51 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Bedrock
Groundwater Zone
Figure 52 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Shallow
Groundwater Zone
Figure 53 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Deep
Groundwater Zone
Figure 54 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Bedrock
Groundwater Zone
Figure 55 Predicted Beryllium in Monitoring Well AB -1 S
Figure 56 Predicted Beryllium in Monitoring Well AB -2S
Figure 57 Predicted Beryllium in Monitoring Well GWA-1 S
Figure 58 Predicted Beryllium in Monitoring Well MW -6S
Figure 59 Initial (2015) Beryllium Concentrations in Shallow Groundwater Zone
Figure 60 Initial (2015) Beryllium Concentrations in Deep Groundwater Zone
Figure 61 Initial (2015) Beryllium Concentrations in Bedrock Groundwater Zone
Figure 62 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Shallow
Groundwater Zone
Figure 63 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Deep
Groundwater Zone
Figure 64 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Bedrock
Groundwater Zone
Figure 65 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Shallow
Groundwater Zone
Figure 66 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Deep
Groundwater Zone
Figure 67 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Bedrock
Groundwater Zone
Figure 68 Predicted Boron in Monitoring Well AB -11S
Figure 69 Predicted Boron in Monitoring Well AB -2S
Figure 70 Predicted Boron in Monitoring Well GWA-1 S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 71 Predicted Boron in Monitoring Well MW -6S
Figure 72 Initial (2015) Boron Concentrations in Shallow Groundwater Zone
Figure 73 Initial (2015) Boron Concentrations in Deep Groundwater Zone
Figure 74 Initial (2015) Boron Concentrations in Bedrock Groundwater Zone
Figure 75 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Shallow
Groundwater Zone
Figure 76 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Deep
Groundwater Zone
Figure 77 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Bedrock
Groundwater Zone
Figure 78 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Shallow
Groundwater Zone
Figure 79 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Deep
Groundwater Zone
Figure 80 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Bedrock
Groundwater Zone
Figure 81 Predicted Chloride in Monitoring Well AB -1 S
Figure 82 Predicted Chloride in Monitoring Well AB -2S
Figure 83 Predicted Chloride in Monitoring Well GWA-1 S
Figure 84 Predicted Chloride in Monitoring Well MW -6S
Figure 85 Initial (2015) Chloride Concentrations in Shallow Groundwater Zone
Figure 86 Initial (2015) Chloride Concentrations in Deep Groundwater Zone
Figure 87 Initial (2015) Chloride Concentrations in Bedrock Groundwater Zone
Figure 88 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Shallow
Groundwater Zone
Figure 89 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Deep
Groundwater Zone
Figure 90 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Bedrock
Groundwater Zone
Figure 91 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Shallow
Groundwater Zone
Figure 92 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Deep
Groundwater Zone
Figure 93 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Bedrock
Groundwater Zone
Figure 94 Predicted Chromium in Monitoring Well AB -1S
Figure 95 Predicted Chromium in Monitoring Well AB -2S
Figure 96 Predicted Chromium in Monitoring Well GWA-1 S
Figure 97 Predicted Chromium in Monitoring Well MW -6S
Figure 98 Initial (2015) Chromium Concentrations in Shallow Groundwater Zone
Figure 99 Initial (2015) Chromium Concentrations in Deep Groundwater Zone
Figure 100 Initial (2015) Chromium Concentrations in Bedrock Groundwater Zone
Figure 101 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in
Shallow Groundwater Zone
Figure 102 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in Deep
Groundwater Zone
Figure 103 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in
Bedrock Groundwater Zone
Figure 104 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Shallow
Groundwater Zone
vi

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 105 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Deep
Groundwater Zone
Figure 106 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Bedrock
Groundwater Zone
Figure 107 Predicted Cobalt in Monitoring Well AB -1S
Figure 108 Predicted Cobalt in Monitoring Well AB -2S
Figure 109 Predicted Cobalt in Monitoring Well GWA-1 S
Figure 110 Predicted Cobalt in Monitoring Well MW -6S
Figure 111 Initial (2015) Cobalt Concentrations in Shallow Groundwater Zone
Figure 112 Initial (2015) Cobalt Concentrations in Deep Groundwater Zone
Figure 113 Initial (2015) Cobalt Concentrations in Bedrock Groundwater Zone
Figure 114 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Shallow
Groundwater Zone
Figure 115 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Deep
Groundwater Zone
Figure 116 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Bedrock
Groundwater Zone
Figure 117 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Shallow
Groundwater Zone
Figure 118 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Deep
Groundwater Zone
Figure 119 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Bedrock
Groundwater Zone
Figure 120 Predicted Hexavalent Chromium in Monitoring Well AB -IIS
Figure 121 Predicted Hexavalent Chromium in Monitoring Well AB -2S
Figure 122 Predicted Hexavalent Chromium in Monitoring Well GWA-1 S
Figure 123 Predicted Hexavalent Chromium in Monitoring Well MW -6S3
Figure 124 Initial (2015) Hexavalent Chromium Concentrations in Shallow Groundwater Zone
Figure 125 Initial (2015) Hexavalent Chromium Concentrations in Deep Groundwater Zone
Figure 126 Initial (2015) Hexavalent Chromium Concentrations in Bedrock Groundwater Zone
Figure 127 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium
Concentrations in Shallow Groundwater Zone
Figure 128 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium
Concentrations in Deep Groundwater Zone
Figure 129 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium
Concentrations in Bedrock Groundwater Zone
Figure 130 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in
Shallow Groundwater Zone
Figure 131 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in
Deep Groundwater Zone
Figure 132 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in
Bedrock Groundwater Zone
Figure 133 Predicted Selenium in Monitoring Well AB -1S
Figure 134 Predicted Selenium in Monitoring Well AB -2S
Figure 135 Predicted Selenium in Monitoring Well GWA-1 S
Figure 136 Predicted Selenium in Monitoring Well MW -6S
Figure 137 Initial (2015) Selenium Concentrations in Shallow Groundwater Zone
Figure 138 Initial (2015) Selenium Concentrations in Deep Groundwater Zone
Figure 139 Initial (2015) Selenium Concentrations in Bedrock Groundwater Zone
Figure 140 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in Shallow
Groundwater Zone
vii

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 141 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in Deep
Groundwater Zone
Figure 142 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in
Bedrock Groundwater Zone
Figure 143 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Shallow
Groundwater Zone
Figure 144 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Deep
Groundwater Zone
Figure 145 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Bedrock
Groundwater Zone
Figure 146 Predicted Sulfate in Monitoring Well AB -1 S
Figure 147 Predicted Sulfate in Monitoring Well AB -2S
Figure 148 Predicted Sulfate in Monitoring Well GWA-1 S
Figure 149 Predicted Sulfate in Monitoring Well MW -6S
Figure 150 Initial (2015) Sulfate Concentrations in Shallow Groundwater Zone
Figure 151 Initial (2015) Sulfate Concentrations in Deep Groundwater Zone
Figure 152 Initial (2015) Sulfate Concentrations in Bedrock Groundwater Zone
Figure 153 Existing Conditions Scenario 1 - 2115 Predicted Sulfate Concentrations in Shallow
Groundwater Zone
Figure 154 Existing Condition Scenario 1 - 2115 Predicted Sulfate Concentrations in Deep
Groundwater Zone
Figure 155 Existing Conditions Scenario 1 - 2115 Predicted Sulfate Concentrations in Bedrock
Groundwater Zone
Figure 156 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Shallow
Groundwater Zone
Figure 157 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Deep
Groundwater Zone
Figure 158 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Bedrock
Groundwater Zone
Figure 159 Predicted Thallium in Monitoring Well AB -1S
Figure 160 Predicted Thallium in Monitoring Well AB -2S
Figure 161 Predicted Thallium in Monitoring Well GWA-1 S
Figure 162 Predicted Thallium in Monitoring Well MW -6S
Figure 163 Initial (2015) Thallium Concentrations in Shallow Groundwater Zone
Figure 164 Initial (2015) Thallium Concentrations in Deep Groundwater Zone
Figure 165 Initial (2015) Thallium Concentrations in Bedrock Groundwater Zone
Figure 166 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Shallow
Groundwater Zone
Figure 167 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Deep
Groundwater Zone
Figure 168 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Bedrock
Groundwater Zone
Figure 169 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Shallow
Groundwater Zone
Figure 170 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Deep
Groundwater Zone
Figure 171 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Bedrock
Groundwater Zone
Figure 172 Predicted Vanadium in Monitoring Well AB -1S
Figure 173 Predicted Vanadium in Monitoring Well AB -2S
Figure 174 Predicted Vanadium in Monitoring Well GWA-1 S
viii

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 175 Predicted Vanadium in Monitoring Well MW -6S
Figure 176 Initial (2015) Vanadium Concentrations in Shallow Groundwater Zone
Figure 177 Initial (2015) Vanadium Concentrations in Deep Groundwater Zone
Figure 178 Initial (2015) Vanadium Concentrations in Bedrock Groundwater Zone
Figure 179 Existing Conditions Scenario 1 - 2115 Predicted Vanadium Concentrations in
Shallow Groundwater Zone
Figure 180 Existing Conditions Scenario 1 - 2115 Predicted Vanadium Concentrations in Deep
Groundwater Zone
Figure 181 Existing Conditionsc Scenario 1 - 2115 Predicted Vanadium Concentrations in
Bedrock Groundwater Zone
Figure 182 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Shallow
Groundwater Zone
Figure 183 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Deep
Groundwater Zone
Figure 184 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Bedrock
Groundwater Zone
ACRONYMS
2L North Carolina surface water standards as specified in T15 NCAC 02B .0211 and
.0216 (amended effective January 2015)
3-D Three-dimensional
CAP Corrective Action Plan
CCR coal combustion residuals
COI constituent of interest
CSA comprehensive site assessment
BR bedrock wells
D deep wells
NCDHHS North Carolina Department of Health and Human Services
EPRI Electric Power Research Institute
FGD flue gas desulfurization
HSL health screening level
IMAC interim maximum allowable concentration
MW megawatt
MSS Marshall Steam Station
NRMSE normalized root mean square error
PPBC provisional background concentration
RMS root mean squared
S shallow wells
ix

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
INTRODUCTION
The purpose of this study is to predict the groundwater flow and constituent transport that may
occur as a result of different possible closure actions at the site. The study consists of three
main activities: development of a calibrated steady-state flow model of site conditions observed
in June 2015, development of a historical transient model for constituent transport calibrated to
current conditions, and predictive simulations of the closure scenrios.
1.1 General Setting and Background
Duke Energy owns and operates the Marshall Steam Station (MSS), located on a 1,446 -acre
tract adjacent to Lake Norman in Catawba County near the town of Terrell, North Carolina. MSS
began operation in 1965 as a coal-fired generating station and currently operates four coal-fired
units. The first two units (Units 1 and 2) began operation in 1965 and 1966, generating 350 MW
each. The remaining units (Units 3 and 4) began operation in 1969 and 1970, generating 648
MW each. Improvements to the plant since 1970 have increased the electric generating
capacity to 2,090 MW. The coal combustion residuals (CCR) from the coal combustion process
at MSS have historically been stored in the station's ash basin located to the north of the station
and adjacent to Lake Norman. The ash basin at MSS consists of a single cell impounded by an
earthen dike located on the southeast end of the ash basin. The ash basin was constructed in
1965 and is located north of the power plant. Inflows from the station to the ash basin are
discharged into the southwest portion of the ash basin as shown on CSA Report Figures 2-1
through 2-4' (HDR 2015a).
The ash basin is situated between the MSS station to the south, a topographic divide located
along Sherrills Ford Road to the west, Island Point Road to the north, and Duke Energy property
to the east. Natural topography at the site generally slopes downward from these divides to the
ash basin and toward Lake Norman (CSA Report Figure 2-2). The ash basin is described further
in Section 2.3 below. A 1954 USGS topographic map depicting the site prior to construction of
the ash basin is shown on CSA Report Figure 2-3.
The air pollution control system for the coal-fired units at MSS includes a flue gas
desulfurization (FGD) system that was placed into operation in 2007. Coal is delivered to the
station by a railroad line. Other areas of the site are occupied by facilities supporting the
production or transmission of power (one switchyard and associated transmission lines), the
FGD wastewater treatment system, and the gypsum handling station (associated with the FGD
system). (See CSA Report Figure 2-4).
Based on the CSA site investigation, the groundwater system in the natural materials (alluvium,
soil, soil/saprolite, and fractured bedrock) at MSS is consistent with the regolith -fractured rock
system and is an unconfined, connected system of flow layers (CSA Report Figure 5-5). The
1 Please refer to the Comprehensive Site Assessment Report, Marshall Steam Station Ash Basin, September 2015
(HDR 2015a) for more information and referenced CSA Report figures and tables.

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
MSS groundwater system is divided into three layers referred to in the CSA as the shallow,
deep (or transition zone), and bedrock flow layers to distinguish the flow layers within the
connected aquifer system. In general, groundwater within the shallow, deep and bedrock layers
flows from northwest and north to the southeast toward Lake Norman.
1.2 Third Party Review
The calibrated flow and transport model third -party peer review team was coordinated by the
Electric Power Research Institute (EPRI) and included Dr. Chunmiao Zheng from the University
of Alabama, James Rumbaugh from Environmental Simulations, Inc, and experienced modelers
from Intera, Inc. The reviewers were provided with the conceptual site model, the MSS
Comprehensive Site Assessment (CSA) Report (HDR 2015a), a draft model report, and digital
model input and output files, allowing them to reconstruct the model for independent review.
During the course of the review, the reviewers communicated with the modelers in order to
better understand how the model was developed and calibrated. As a result of these
communications, the model was modified and recalibrated, which allowed the reviewers to
conclude that the model was constructed and calibrated sufficiently to achieve its primary
objective of comparing the effects of closure alternatives on nearby groundwater quality. In
addition, the reviewers identified limitations with the model, which are included in the discussion
of model limitations later in this documentation.
After EPRI acceptance of the initial MSS groundwater model, the model was refined to
incorporate post -CSA data. These changes did not change the model structure or boundaries
and did not deviate from EPRI guidelines. An independent review of the refined MSS model was
conducted by EPRI and found that the model was sufficient to meet the objecties of predicting
effects of corrective action alternatives on groundwater quality.
2 CONCEPTUAL MODEL
The site conceptual model for MSS is primarily based on the CSA Report. The CSA Report
contains extensive detail and data related to most aspects of the site conceptual model that are
used in this study.
2.1 Geology and Hydrogeology
The MSS site is located within the Charlotte terrane, one of a number of tectonostratigraphic
terranes that have been defined in the southern and central Appalachians and is in the western
portion of the larger Carolina superterrane (CSA Report Figure 5-1). The Charlotte terrane is
dominated by a complex sequence of plutonic rocks that intrude a suite of metaigneous rocks. A
geologic map of the area around MSS is shown in CSA Report Figure 5-2.
The fractured bedrock is overlain by a mantle of unconsolidated material known as regolith. The
regolith includes residual soil and saprolite zones and where present, alluvial deposits.
Saprolite, the product of chemical weathering of the underlying bedrock, is typically composed
of clay and coarser granular material and reflects the texture and structure of the rock from
which it was formed. The weathering products of granitic rocks are quartz -rich and sandy

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
textured. Rocks poor in quartz and rich in feldspar and ferro-magnesium minerals form a more
clayey saprolite.
The groundwater system in the Piedmont province, in most cases, is comprised of two
interconnected layers, or mediums: 1) residual soil/saprolite and weathered fractured rock
(regolith) overlying 2) fractured crystalline bedrock. The regolith layer is a thoroughly weathered
and structureless residual soil that occurs near the ground surface with the degree of
weathering decreasing with depth. The residual soil grades into saprolite, a coarser grained
material that retains the structure of the parent bedrock. Beneath the saprolite, partially
weathered/fractured bedrock occurs with depth until sound bedrock is encountered. This layer
serves as the principal storage reservoir and provides an intergranular medium through which
the recharge and discharge of water from the underlying fractured rock occurs. Within the
fractured crystalline bedrock layer, the fractures control both the hydraulic conductivity and
storage capacity of the rock mass. A transition zone at the base of the regolith has been
interpreted to be present in many areas of the Piedmont. It is described as consisting of partially
weathered/fractured bedrock and lesser amounts of saprolite that grades into bedrock and is
considered to be the most permeable part of the system (HDR 2015a).
2.2 Hydrostratigraphic Layer Development
Soil conditions encountered in the borings showed minimal variation across the site. Residual
soil consists of clayey sand, silty sand, silty sand with gravel, micaceous silty sand, and gravel
with silt and sand. The following materials were encountered during the CSA and are consistent
with material descriptions from previous site exploration studies.
Ash — Ash was encountered in borings advanced within the ash basin and ash storage areas,
as well as through dikes. Ash was generally described as gray to dark gray, non -plastic, loose to
medium dense, dry to wet, fine to coarse-grained.
Fill — Fill material generally consisted of reworked silts, clays, and sands that were borrowed
from one area of the site and redistributed to other areas. Fill was generally classified as silty
sand, clay with sand, clay, and sandy clay on the boring logs. Fill was used in the construction
of dikes, and as cover for ash storage areas.
Alluvium —Alluvium encountered in borings during the project was classified as clay and sand
with clay. In some cases alluvium was logged beneath ash.
Residuum (Residual soils) — Residuum is the in-place weathered soil that consists primarily of
silt with sand, clayey sand, sandy clay, clay with gravel, and clayey silts. Residuum varied in
thickness and was relatively thin compared to the thickness of saprolite.
Saprolite/Weathered Rock — Saprolite is soil developed by in-place weathering of rock that
retains remnant bedrock structure. Saprolite consists primarily of medium dense to very dense
silty sand, sandy silt, sand, sand with gravel, sand with clay, clay with sand, and clay. Sand
particle size ranges from fine to coarse grained. Much of the saprolite is micaceous.

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Partially Weathered/Fractured Rock — Partially weathered (slight to moderate) and/or highly
fractured rock encountered below auger refusal.
Bedrock — Sound rock in boreholes, was generally slightly weathered to fresh and relatively
unfractured.
Based on the CSA, the groundwater system is consistent with the regolith -fractured bedrock
system. To define the hydrostratigraphic units the following classification system was used and
is based on standard penetration testing (N) values, Recovery (REC), and Rock Quality
Designation (RQD) collected during the drilling and logging of boreholes.
The material designations shown below (M1, M2, TZ, and BR) are used on the geologic cross-
sections with transect locations in the CSA Report Figure 8-2. The ash, fill and alluvial layers
are represented by A, F, and S, respectively, on cross sections and in tables in the CSA Report.
The ranges of hydrostratigraphic layer properties measured at MSS are provided in CSA Report
Tables 11-7 through 11-11. To further define the hydrostratigraphic units, the following
classification system was used based on standard penetration testing values, recovery (REC),
and rock quality designation (RQD) collected during drilling and logging of boreholes.
The ash, fill, and alluvial layers are as encountered at the site. The natural system (except
alluvium) includes the following layers:
M1 — Soil/Saprolite:
M2 — Saprolite/Weathered Rock:
TZ — Transition Zone:
BR — Bedrock:
N<50
N>50 or REC<50%
REC>50% and RQD<50%
REC>85% and RQD>50%.
Rock core runs that fell between the values for TZ and BR (REC<85% and RQD>50% or
REC>85% and RQD<50%) were assigned a hydrostratigraphic layer based on a review of the
borehole logs, rock core photographs, and geologic judgment. The same review was performed
to determine the thickness of the transition zone just in case it extended into the next core run,
which when reviewed alone might have met the bedrock criterion, because of potential core loss
or fractured/jointed rock with indications of water movement (iron/manganese staining).
2.3 Ash Management Areas
Historical and current information about the MSS ash basin system compiled by HDR was used
to develop a conceptual understanding that was developed into numerical groundwater flow
models. Refer to CSA Report Figures 2-2 and 2-4 for locations of the ash basin system
components described below.
Coal ash residue from the coal combustion process has historically been disposed in the MSS
ash basin. Fly ash from the electrostatic precipitators was collected in hoppers. Bottom ash and
boiler slag was collected in the bottom of the boilers. After collection, both fly ash and bottom
ash/boiler slag were sluiced to the ash basin using conveyance water withdrawn from Lake
Norman. Refer to CSA Report Figure 2-4 for a depiction of these features. During operation of
the coal-fired units, the sluice lines discharged the water/slurry and other flows to the southwest
4

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
portion of the ash basin. Inflows to the ash basin are highly variable due to variability in station
operations and weather.
The ash basin at MSS consists of a single cell impounded by an earthen dike located on the
southeast end of the ash basin. The ash basin is located north of the power plant. Inflows from
the station to the ash basin are discharged into the southwest portion of the ash basin.
Discharge from the ash basin is through a concrete discharge tower located in the eastern
portion of the ash basin. The concrete discharge tower drains through a 30 -inch -diameter slip -
lined corrugated metal pipe, which discharges into Lake Norman. The ash basin pond elevation
is controlled by the use of concrete stoplogs in the discharge tower. The following sections
provide additional details of the MSS ash basin, ash storage areas, and other waste
management units.
2.3.1 Ash Basin
The initial MSS ash basin was constructed in 1965 by building an earthen dike at the confluence
where Holdsclaw Creek historically entered the Catawba River. The earthen dike was
constructed to impound water and ash was sluiced to the basin. In general, the ash basin is
located in a historical depression formed from Holdsclaw Creek and small tributaries that fed the
creek. The basin has a dendritic shape consisting of coves of deposited ash, dikes that impound
ash in portions of the basin, and four main areas of ponded water. The area contained within the
ash basin waste boundary is approximately 394 acres
All coal ash from MSS operations was disposed of in 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 (described
below) and bottom ash has continued to be sluiced to the ash basin.
While FGD residue is not placed in the ash basin, contact stormwater and leachate from the
FGD landfill, along with FGD wastewater treatment system effluent, are routed to the ash basin.
The FGD residue produced by the air treatment system at MSS is primarily gypsum
(CaSO4.2H2O) and is sold for re -use or disposed of in one of the on-site landfills. Bottom ash is
sluiced to concrete pits where the water is allowed to decant and then flow to the ash basin via
a discharge canal. Bottom ash is then excavated from the pit and discharge canal that flows to
the ash basin, and sold for off-site beneficial reuse or used for roads at the ash basin facility.
During operations, the sluice water/ash slurry (and other flows) is discharged into the southwest
portion of the ash basin.
2.3.2 Dry Ash Landfill
Two unlined ash landfill units, referred to as the Phase I and Phase II dry ash landfill, are
located adjacent to the east and northeast portions of the ash basin, respectively. Phase I
contains approximately 280,000 tons of fly ash, which was placed from September 1984 to
March 1986. Placement of ash in the Phase II area began in approximately March of 1986 and
was completed in 1999. Phase II contains approximately 2,515,000 tons of fly ash. The
approximate boundaries of Phase I and 11 landfill units are shown on CSA Report Figures 2-2

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
and 2-7. These units were constructed prior to the requirement for lining industrial landfills and
were closed with a soil cover system.
2.3.3 FGD Landfill
The FGD landfill (NCDEQ2 Division of Solid Waste Permit No. 1809 -INDUS) is located to the
west of the ash basin. In general, the topography of this landfill site slopes from the west-
northwest to the east-southeast towards the ash basin. The landfill ceased operation and was
temporarily closed in October 2015. The landfill is permitted to receive the following types of
waste generated at Duke Energy Corporation facilities: FGD residue (gypsum), clarifier sludge,
fly ash, bottom ash, construction and demolition waste, asbestos waste, mill rejects (pyrites),
waste limestone material, land clearing and inert debris, boiler slag, ball mill rejects, sand blast
material, and coal waste. The landfill is constructed with an engineered liner system. Contact
stormwater and leachate are collected and piped or discharged to the ash basin.
2.3.4 Industrial Landfill No. 1
The Industrial Landfill No. 1 (NCDEQ Permit No. 1812 -INDUS) is located adjacent to the north
portion of the ash basin. The landfill was constructed with a leachate collection and removal
system and a three -component liner system consisting of a primary geomembrane, secondary
geomembrane (with a leak detection system between them), and soil liner. The landfill is
permitted to receive the following types of waste generated at Duke Energy Corporation
facilities: fly ash, bottom ash, FGD residue, FGD clarifier sludge, asbestos material, land
clearing and inert debris, coal mill rejects, waste limestone material, boiler slag, construction
and demolition waste, sand blast material, ball mill rejects, coal waste, and pyrites. The landfill
was constructed over portions of residual material and over portions of the ash basin. The
subgrade for portions of this landfill were constructed of fly ash under the structural fill rules
found in 15A NCAC 138.1700 et seq. Contact stormwater and leachate are collected and piped
to the ash basin.
2.3.5 Demolition Landfill
The demolition landfill (NCDEQ Permit No. 1804 -INDUS) is located adjacent to the north portion
of the ash basin directly north of the dry ash landfill (Phase II). The landfill received construction
and demolition waste from MSS starting in September 1984 and was closed with a soil cap in
2008.
2.3.6 Asbestos Landfill
The asbestos landfill (NCDEQ Permit No. 1804 -INDUS) is located adjacent to the north portion
of the ash basin and adjacent to the demolition landfill. This landfill received asbestos waste
from MSS and other Duke Energy facilities starting in December 1987. The landfill was closed
with a soil cap in 2008.
2 Prior to September 18, 2015, the NCDEQ was referred to as the North Carolina Department of Environment and
Natural Resources (NCDENR). Both naming conventions are used in this report, as appropriate.
M

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
2.3.7 Photovoltaic Farm Structural Fill
The photovoltaic farm structural fill (PV structural fill) was constructed of fly ash under the
structural fill rules found in 15A NCAC 13B.1700 et seq. and is located adjacent to and partially
on top of the northwest portion of the ash basin. The PV structural fill is used for renewable
energy production and contains a solar panel field on the south portion of the structural fill unit.
Placement of dry ash in the structural fill began in October 2000. The structural fill was
completed and closed in February 2013.
2.4 Groundwater Flow System
Groundwater is recharged by infiltration where the ground surface is permeable, including the
dike and ash of the ash basin system where exposed at the ground surface. After infiltrating the
ground surface, water in the unsaturated zone percolates downward to the unconfined water
table, except where ponded water conditions exist on portions on the ash basin. From the water
table, groundwater moves downward and then laterally through unconsolidated material
(residual soil/saprolite) into the weathered, fractured rock, then into fractured bedrock.
Groundwater discharges where drains intersect the water table and where hydrostatigraphic
layers outcrop at the unnamed stream and Lake Norman to the southeast.
Mean annual recharge in the Piedmont ranges from 4.0 to 9.7 inches per year (Daniel
2001).However, given that it has not been measured or estimated in the CSA or other studies of
the site, recharge to the ash basin system was estimated by considering it as a calibration
parameter in the groundwater flow model.
Based on the site investigation, the groundwater system in the natural materials (alluvium, soil,
soil/saprolite, and bedrock) at MSS is consistent with the regolith -fractured rock system and is
an unconfined, connected system of flow layers. The MSS groundwater system is divided into
three layers referred to as the shallow, deep , and bedrock flow layers to distinguish the flow
layers within the connected aquifer system. In general, groundwater within the shallow and deep
layers (S and D wells) and bedrock layer (BR wells) flows from northwest and north to the
southeast toward Lake Norman (CSA Report Figures 6-5 through 6-7).
In accordance with the Piedmont Slope Aquifer System (LeGrand 2004), fractured density in
bedrock decreases with depth, limiting deep groundwater flow (CSA Report Figure 5-5).
2.5 Hydrologic Boundaries
The major discharge location for the groundwater system at MSS, Lake Norman to the
southeast (CSA Report Figure 2-4), serves as a hydrologic boundary for the site. Drainage
features within small catchments in the upland area of the site act as shallow hydrologic
boundaries. In the groundwater flow model, these features are treated as internal water sinks as
described in Section 4.5.Hydraulic Boundaries
2.6 Hydraulic Boundaries
Hydraulic boundaries at MSS consist of liner systems beneath waste management units
described in Section 2.3. These are the FGD landfill and the Industrial Landfill No. 1. In Section

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
4.6, recharge to the groundwater model is adjusted to account for a waste management unit
being lined.
The groundwater flow system at MSS does not have any other impermeable barriers or
boundaries with the exception of bedrock at depth where fracture density, and fracture flow, is
minimal. Natural groundwater divides exist along topographic divides, but are a result of local
flow conditions as opposed to barriers.
2.7 Sources and Sinks
Recharge, including that to the ash basin, is the major source of water for the groundwater
system. Most of this water discharges to the hydrologic boundary at Lake Norman and local
drains. Recharge that infiltrates the FGD landfill and Industrial Landfill No. 1 is intercepted by
the liner system at depth and is diverted to the ash basin.
The CSA receptor survey identified four public water supply wells and 83 private water supply
wells in use, along with six assumed private water supply wells, located within the 0.5 -mile
radius of the ash basin Compliance Boundary. No water supply wells (including irrigation wells
and unused or abandoned wells) were identified between the source area and Lake Norman
(HDR 2015a). Four private water supply wells are included in the model domain and are
pumping at assumed rates of 400 gpd each based on average EPA household usage.
The CSA does not consider any effect that these wells may have on groundwater flow at the
site, nor does it identify other sources or sinks. The CSA does not suggest that the MSS ash
basin is within the capture zone or zone of influence of any extraction well or wells.
Furthermore, it states that the groundwater flow direction across the site is away from the
direction of the nearest public or private water supply wells.
2.8 Water Balance
Over an extended period of time, the rate of water inflow to the modeled area is equal to its rate
of water outflow. That is, there is no net change in groundwater storage. Water enters the
groundwater system through recharge and ultimately discharges to the Lake Norman.
2.9 Modeled Constituents of Interest
As defined in the CSA, constituents are those chemicals or compounds that were identified in
the approved groundwater assessment plans for sampling and analysis. If a constituent
exceeded its respective regulatory standard or screening level in the medium in which it was
found, the constituent was then termed a COI.
The CSA found the following COls in ash basin porewater: antimony, arsenic, barium, beryllium,
boron, cadmium, chloride, chromium, cobalt, iron, lead, manganese, nickel, selenium, sulfate,
thallium, and vanadium. Hexavalent chromium was also included as a modeled COI due to
exceedances of its North Carolina Department of Health and Human Services (NCDHHS health
screening level (HSL) in groundwater downgradient of the ash basin and dry ash landfill (Phase
1). Exclusive of cadmium, lead, and manganese, all of these COls were considered in the
0

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
transport simulations. Iron and manganese are naturally occurring in the groundwater system
and require more complex modeling than what is currently being performed.
The simulated Cols occur at elevated levels in groundwater near the ash basin (CSA Report
Figures 10-75 to 10-98, 10-108 to 10-116, and 10-120 to 10-122). Boron, chloride, and sulfate
are considered mobile in groundwater as they do not readily precipitate or adsorb to soils. The
other COls adsorb to commonly occurring soil types based upon the linear sorption coefficient
(Kd) analysis performed.
2.10 COI Transport
COls entered the ash basin system in the dissolved phase and solid phase of the station's
wastewater discharge. Some constituents are also present in native soils and groundwater
beneath the basin. The accumulation and subsequent release of chemical constituents in the
ash basin over time is complex. In the active and inactive ash basin, constituents may incur
phase changes via dissolution, precipitation, chemical reactions and adsorption/desorption.
Dissolved phase constituents may incur these phase changes as they are transported by
advection and dispersion in groundwater flowing downgradient from the inactive/active ash
basin areas. In the fate and transport model, chemical constituents enter in the dissolved phase
by specifying a steady-state concentration in the ash porewater. Phases changes (dissolution,
precipitation, adsorption, and desorption) are collectively taken into account by specifying a
linear sorption coefficient (distribution coefficient [Kd]). The accumulation and subsequent
release of chemical constituents in the ash basin over time is a complex process. In the
conceptual fate and transport model, it was assumed that the entry of constituents into the ash
basin is represented by a constant concentration in the saturated zone of the basin, which is
flushed by recharge water infiltrating from above.
At the ash storage area, leachable constituents enter the dissolved phase during transient
infiltration events through the stored ash. Infiltration with constituents in solution moves
downward through the stored ash and underlying, unsaturated soils and finally into groundwater
at the water table. Dissolved phase constituents may incur phase changes also as they migrate
through the stored ash and native soils to the water table. In the conceptual fate and transport
model, it was assumed that the entry of constituents into groundwater beneath the ash storage
area is represented by a constant concentration at the water table beneath the ash storage
area, which is continually flushed by infiltrating recharge from above.
The following approach was used for transport modeling:
A "physical -type" modeling approach was used, as site-specific geochemical conditions
are not understood or characterized at the scale and extent required for inclusion in the
model.
• The flux of contaminant mass from the ash sources is not quantified, so it is not included
in the conceptual site model or represented in the numerical model. As such, a simplified
approach was used and the entry of constituents was represented in the model using a
constant concentration in the saturated zone of the basin (which is continually flushed by
water moving through the porous media). The constant concentration cells cover the
M

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
source areas and the concentrations for each of these sources were determined during
transport model calibration.
• The retardation effects of the COI (e.g., by adsorption onto solid surfaces) were
collectively taken into account by specifying a linear soil -water partitioning coefficient
(K d).
3 COMPUTER MODEL
3.1 Model Selection
The computer code MODFLOW solves the system of equations that quantify the flow of
groundwater in three dimensions (3-D). MODFLOW can simulate steady-state and transient
flow, as well as confined and water table conditions. Additional components of groundwater can
be considered, including: pumping wells, recharge, evapotranspiration, rivers, streams, springs,
and lakes. The information assembled in the conceptual site model is translated into its
numerical equivalent from which a solution is generated by MODFLOW.
3.2 Model Description
The specific MODFLOW package chosen for the study is NWT—a Newton formulation of
MODFLOW-2005 that is specifically designed for improving the stability of solutions involving
drying and re -wetting under water table conditions (Niswonger et al. 2011). The numerical code
selected for the transport model is MT3DMS (Zheng and Wang 1999). MT3DMS is multi -
species 3-dimensional mass transport model that can simulate advection, dispersion/diffusion,
and chemical reaction of COls in groundwater flow systems, and has a package that provides a
link to the MODFLOW codes. The MODFLOW-NWT and MT3DMS input packages used to
create the groundwater flow and transport models, and a brief description of their use, are
provided in Table 1.
4 GROUNDWATER FLOW AND TRANSPORT MODEL CONSTRUCTION
The flow and transport model for the study was developed through a multi -step process. First, a
3-D model of the site hydrostratigraphy was constructed based on historical site construction
drawings and field data. Once the model domain was determined, a 3-D steady-state
groundwater model based on the hydrostratigraphy and the site conceptual model was
produced. Flow parameters, assigned to the numerical grid, were adjusted during the steady-
state flow model calibration process. Once the flow model was calibrated, a transient transport
simulation for the selected COls was developed, and then calibrated by adjusting transport
parameters and revising flow parameters to best match the observed (2015) concentrations and
water levels in selected monitoring wells.
Three terrain surface models for MSS were created using geographic information systems (GIS)
software: 1) current existing surface, 2) pre -construction surface without ash and ash basin
dikes, and 3) pre -construction surface with dikes but without ash. An interpolation tool in ArcGIS
10

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
10.3 software was used to generate the terrain surfaces as raster datasets with 20 -foot cells
Each surface was created to cover the extent of the groundwater model domain.
4.1 Model Hydrostratigraphy
The model hydrostratigraphy was developed using historical site construction drawings and
borehole data to construct three-dimensional surfaces representing contacts between
hydrostratigraphic units with properties provided in CSA Report Tables 11-8 through 11-12
(HDR 2015a).
1) Existing Ground Surface
Topographic and bathymetric elevation contours and spot elevations were produced from
surveys conducted in 2014. Since these surveys did not cover the entire model extent, elevation
data extracted as spot elevations from the North Carolina Floodplain Mapping Program's 2010
LiDAR elevation data were used for the areas surrounding the surveys. At MSS, simplified
elevation contours were digitized along the river channels to depress the surface a small
amount below water level.
2) Pre -construction Surface
Elevation contours of the original ground surface were digitized in CAD from engineering
drawings supplied by Duke Energy. These data were imported into GIS, and georeferenced.
These contours were trimmed to the areas underlying ash basins, dams, dikes and ash storage
areas. The source data used in the existing surface were then replaced by the original surface
data where there was overlap. Elevation data from coal storage areas were removed. The pre -
construction surface was then created using the combination of original surface elevations,
2014 survey elevations, and 2010 LiDAR elevations.
3) Pre -construction Surface with Dikes
Surface models of the ash basin dams and dikes were constructed from crest elevations as
determined from the 2014 survey and slopes on the engineering drawings. Only the sections of
the dams and dikes facing the ash basins were modeled in this way. The 2014 survey data were
used for dike/dam crests and outwardly facing surfaces. These surfaces were merged with the
pre -construction surface. These GIS data sets were exported into formats readable by
RockWorks and GMS MODFLOW.
4) 3-D Hydrostratigraphic Grids
The natural materials in the CSA boreholes and existing boreholes were assigned a
hydrostratigraphic layer using the classification scheme in Section 2,2 and. In the portions of the
area to be modeled for which borehole data is not available, dummy boreholes were used to
extend the model to the model boundaries. These boreholes were based on the
hydrostratigraphic thickness of the existing boreholes and the elevation of the existing boreholes
based on the assumption that the hydrostratigraphic layers are a subdued replica of the original
topography of the site and geologic judgment.
11

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
The grid of the pre -construction ground surface (described above) was used to constrain the
modeling of the natural layers. For gridding the data on a 20 feet x 20 feet grid across the area
to be modeled, a hybrid algorithm was used with inverse distance weighted two (2) and
triangulation weighted one (1) and declustering, smoothing, and densifying subroutines. The
declustering option is used to remove duplicate points and de -cluster clustered points. The
option creates a temporary grid with a z -value assigned based on the closet data point to the
midpoint of a voxel. The smoothing option averages the z -values in a grid based on a filter size.
For this modeling, the z -value is assigned the average of itself and that of the eight nodes
immediately surrounding it. One smoothing pass is made. The densify option adds additional
points to the xyz input by fitting a Delaunay triangulation network to the data and adding the
midpoint of each triangle to the xyz input points. The net result is that the subsequent gridding
process uses more control points and tends to constrain algorithms that may become creative in
areas of little control. Only one densification pass is made. The completed model grids were
exported in spreadsheet format for use in the groundwater flow and transport model.
4.2 Groundwater Vistas Version 6
Groundwater Vistas developed by ESI, Inc. was employed to carryout flow and transport
modeling for this analysis phase. MODFLOW and MT3DMS files from the Corrective Action
Plan (CAP) Part 1 Report (HDR 2015b) were imported to Vistas for model refinement. Full
documentation of Vistas software can be found at
http://groundwatermodels.com/Groundwater Vistas.php
4.3 Model Domain and Grid
The model domain encompasses the MSS site, including a section of Lake Norman and all site
features relevant to the assessment of groundwater associated with the ash basin. The model
domain extends beyond the ash basin to hydrologic boundaries such that groundwater flow and
COI transport through the area is accurately simulated without introducing artificial boundary
effects.
The bounding rectangle around the model domain extends 11,000 feet north to south and
12,000 feet east to west and has a grid consisting of 273,557 active cells in ten layers (Figures
1 through 3). The grid spacing is 40 feet by 40 feet. In plan view, the MSS model domain is
bounded by the following hydrologic features of the site (Figure 4 and CSA Report Figure 2-4):
• the northwestern shore of Lake Norman to the southeast,
• an unnamed stream and groundwater divide corresponding to the topographic divide to
the east,
• the groundwater divide corresponding to the topographic divide to the north along Island
Point Road, and
• the groundwater divide corresponding to the topographic divide to the west and south
along the coal delivery rail line.
The domain boundary was developed by manually digitizing the topographic divides using a
base map containing 2 -foot Lidar contours. The lower limit of the model domain coincides with
12

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
an assumed maximum depth of water yielding fractures in bedrock. This was estimated to be
530 feet below the base of the transition zone across the site upper limit based on a review of
boring logs contained in the CSA.
There are a total of 11 model layers divided among the identified hydrostratigraphic units to
simulate flow with a vertical flow component. The units are represented by the model layers
listed below:
• Model layers 1 - 3
• Model layers 2 - 4
• Model layer 5 and 6
• Model layer 7
• Model layer 8
• Model layers 9 - 10
Ash Material
Dike and Ash Storage Material
M1 Saprolite and Alluvium where present
M2 Saprolite
TZ Transition Zone
Fractured Bedrock
In the groundwater flow model, fractured bedrock was simulated as an equivalent porous
medium. The materials comprising each layer and typical layer thicknesses are shown in the
north -south and east -west cross-sections through the active/inactive ash basin areas on Figure
2 and Figure 3.
4.4 Hydraulic Parameters
Horizontal and vertical hydraulic conductivities, which are specific for each hydrostratigraphic
unit, are the primary determinants of groundwater flow for a given configuration of boundary
conditions and sources and sinks, including recharge. Field measurements of these parameters
from CSA Report Tables 11-7 through 11-11 provided guidance for their selection during the
flow model calibration. The values assigned to the model are shown in Table 2.
4.5 Flow Model Boundary Conditions
Boundary conditions for the MSS flow model are one of two types: constant head or drain. No -
flow boundaries of the site have no prescribed boundary in the model. The outer boundary of
the model domain was selected to coincide with physical hydrologic boundaries at Lake Norman
and drainage features, and no flow boundaries at groundwater divides corresponding to
topographic divides (flow model boundary conditions are shown on Figure 4).
At Lake Norman and the cove below the unnamed stream to the east and southeast, a constant
head boundary was applied at layers above fractured bedrock (layers 9 and 10) with bottom
elevations below the water surface elevation, which was taken to be 755 feet as indicated on
CSA Report Figures 6-5 to 6-7.
Drainage features within small catchments in the upland area of the site, the unnamed stream to
the east, and other selected low areas act as shallow hydrologic boundaries. Internal drain
boundaries were applied at these locations to limit the rise of the modeled water table above
ground surface (Figure 4). Drain boundaries were applied with an assumed conductance of 10
feet/day, an assumed bed thickness of one foot, and width equal to the model cell width.
13

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
It is noted that constant head boundary conditions may not be valid for groundwater extraction
as a corrective action alternative. In this case, the constant head boundary assumption should
be validated by a pump test or other means.
4.6 Flow Model Sources and Sinks
Recharge is the main source considered in the model. (Drainage boundaries are described
above as flow boundary conditions.) Mean annual recharge in the Piedmont ranges from 4.0 to
9.7 inches per year (Daniel 2001). Recharge applied to the inactive ash basin area of the model
and areas outside the inactive ash basin were assigned a value of 6.6 inches per year; the
includes dry ash landfill Phase I. Industrial Landfill No. 1 and The FGD residue landfill were
constructed with liners, and as a result the model recharge was set to zero. The recharge at the
PV structural fill and dry ash landfill Phase 2 are 6.6 and 4.0 inches per year, respectively.
Recharge within the active ash basin was calculated using Darcy equations based on the area
of the ash basin, the approximate depth of water or saturated ash, and the range of measured
hydraulic conductivity values within the ash and fill. The recharge rate applied to the active ash
basin area was 12.3 inches per year. The recharge areas in the model are shown on Figure 5.
Pumping wells were identified in the CSA. Four residential pumping wells are within the current
model domain and have been included as active pumping wells completed within the bedrock
layer during calibration and predictive scenarios. Actual pumping rates are unknown, so a
constant pumping rate of 400 gpd, which is the average EPA household usage, has been used.
4.7 Flow Model Calibration Targets
The steady-state flow model calibration targets were the 72 water level observations made in
July 2015. These wells include 33 wells screened in the ash, the dikes, and shallow zone
(S/M1/M2), 30 wells in the transition zone, and 9 wells in fractured bedrock. The observation
values were assigned by layer as shown in Table 3. The observation wells in shallow (M1/M2),
deep (TZ), and bedrock (BR) groundwater zones are shown on Figures 7, 8, and 9.
4.8 Transport Model Parameters
The calibrated, steady-state flow model was used to apply flow conditions for the transport
model at the ash basin, the dry ash landfill Phases I and II, and the PV structural fill where
elevated concentrations of COls were detected during the July 2015 sampling event (CSA
Report Figure 2-1 and Tables 4 and 5). Although their approximate dates of operation are
known, the sluiced ash loading histories for these locations are not available. In order to
calibrate the transport model to existing conditions, constant concentration source zones were
applied at the ash (model layer 4) in the active and inactive ash basins starting from the date
when the first ash basin was placed in service (i.e., 1965). The relevant input parameters were
the constant concentration at the source zone, the linear sorption coefficient (Kd) for sorptive
constituents (including all COls, except for sulfate), the effective porosity, and the dispersivity
tensor.
The conceptual transport model specifies that COls enter the model from the shallow saturated
source zones in the inactive/active ash basin.The range of Kd values applied was derived from
14

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
UNCC laboratory measured values and adjusted to achieve calibration in the model. The most
appropriate method to calibrate the transport model was to use the lower limit of measured Kd
values to produce an acceptable agreement between measured and modeled concentrations.
Thus, an effective Kd value results that likely represents the combined result of intermittent
activities over the service life of the ash basin. These may include pond dredging, dewatering
for dike construction, and ash grading and placement. This approach is expected to produce
conservative results, as sorbed constituent mass is released and transported downgradient.
The Kd values for the COls were applied as follows:
• Antimony: 1.0 mL/g
• Arsenic: 480 mL/g
• Barium: 1.0 mL/g
• Beryllium: 1.0 mL/g
• Boron: 0.1 mL/g
• Hexavalent chromium: 1.0 mL/g
• Chloride: conservative (sorption not modeled)
• Cobalt: 1.0 mL/g
• Chromium: 1.0 mL/g
• Selenium: 1.0 mL/g
• Sulfate: conservative (sorption not modeled)
• Thallium: 70 mL/g
• Vanadium: 25 mL/g
The bulk density used in the model is 2.65 grams/cubic centimeter for deep and bedrock
materials, 2.385 grams/cubic centimeter for the transition zone and 2.12 grams/cubic centimeter
for saprolite and alluvium.
The velocity of COls in groundwater is related to the effective porosity of the porous medium.
Effective porosity applied was estimated based on the values reported in the CSA. All values
applied to the model are shown in Table 4. Dispersivity is a physical property of the aquifer
medium and is normally a fraction of the field scale problem (i.e., plume length), commonly 10%
(Zheng and Bennett 2002). The dispersivity quantifies the degree to which mechanical
dispersion of COls occurs. Dispersivity values of 70 feet, 7 feet, and 0.7 feet (longitudinal,
transverse horizontal, transverse vertical) were applied in this model. The commonly applied
estimate is 10% of the observation scale. In order to avoid artificial oscillation in the numerical
solution to the advection dispersion equation, the grid Peclet number, or the ratio of grid spacing
to longitudinal dispersivity, should be less than two (Zheng and Bennett 2002). The longitudinal
and transverse dispersivity results in grid Peclet numbers of 0.5 and 5.0 respectively, which are
within the acceptable range. Directly beneath the ash basin system, shallow groundwater flow is
vertical downward. In this case, the grid Peclet number criteria will not be met due to the
relatively small value for vertical dispersivity and the relatively large grid spacing, or thickness of
the model layers at depth. The effect of numerical oscillation on modeled concentration and
mass transport is indeterminate. However any effect is considered to be limited as vertical
groundwater flow transitions to horizontal over a short distance beneath the ash basin system.
15

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
4.9 Transport Model Boundary Conditions
The transport model boundary conditions have an initial concentration of zero where water
leaves the model. The background concentration used as initial concentrations for each COI is
the proposed provisional background concentration (PPBC) identified in the CAP Part 1.
Recharge does not have a specified concentration.
The background concentrations for the COls applied as initial concentrations are as follows:
• Antimony: 2.5 pg/L
• Arsenic: 5.0 pg/L
• Barium: 157.3 pg/L
• Beryllium: 1.0 pg/L
• Boron: 100 pg/L
• Chloride: 3,500 pg/L
• Chromium: 11.3 pg/L
• Cobalt: 2.5 pg/L
• Hexavalent Chromium: 2.8 pg/L
• Selenium: 10 pg/L
• Sulfate: 1,460 pg/L
• Thallium: 0.5 pg/L
• Vanadium: 3.9 pg/L
4.10 Transport Model Sources and Sinks
The ash basin, the dry ash landfill Phases I and 11, and the PV structural fill are the sources for
COls in the model. During the transport model calibration and the existing conditions scenario,
the sources were modeled as constant concentration cells in model layers 2 through 4 (Figure
5) and layers 5 through 7 (Figure 6). The concentrations are based on COI measurements in
the shallow zone during the June/July 2015 sampling event. The transport model sinks
correspond to the constant head boundaries of the flow model. Water and COI mass are
removed from the model cells comprising these boundaries.
4.11 Transport Model Calibration Targets
The calibration targets are the measured COI concentrations for the June/July 2015 sampling
event as shown in CSA Report Tables 7-5 and 10-7 to 10-9. Specific calibration targets for the
transport model calibration are discussed in Section 5.3.
5 MODEL CALIBRATION TO CURRENT CONDITIONS
5.1 Flow Model Residual Analysis
The flow model was calibrated to the water level observations obtained during June 2015 in the
shallow, deep, and bedrock wells (Table 3). The water table elevation in the ash basin cells and
16

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
selected depressions across the site were also considered as calibration targets. The
observation data from this single point in time were used as a flow model calibration data set.
The locations of the observation wells are shown on Figures 7, 8, and 9. The initial trial -and -
error calibration assumed homogeneous conditions in each model layer. Recharge was also
fixed at reasonable values early in the calibration process, and then refinements were made by
adjusting hydraulic conductivity zones, as shown on Figures 10 and 11. The basis for delineating
the zones in this way was to obtain the best local calibration using conductivity values within the
range of measurements from monitoring well testing as documented during the CSA.
The calibrated flow model parameters are provided in Table 2. Modeled and observed water
levels (post -calibration) are compared in Table 3 and on Figure 12. The calibrated flow model is
assumed to represent long term, steady-state flow conditions for the site and the ash basin
system under long-term, average conditions. This assumption should be verified as additional
data are collected from the existing and any additional monitoring wells.
The square root of the average square error (also referred to as the root mean squared error, or
RMS error) of the modeled versus observed water levels for wells gauged in June 2015 is also
provided in Table 3. The model calibration goal is an RMS error less than 10% of the change in
head across the model domain. The ratio of the average RMS error to total measured head
change is the normalized root mean square error (NRMSE). The NRMSE of the calibrated
model is 5.5%.
Hydraulic head contours for the shallow zone of the calibrated flow model are shown on Figure
13. In the upland area of the site, groundwater flow in the shallow, deep, and fractured bedrock
zones follows the original, pre -ash basin pattern of flow in the small catchments and converges
on the former Holdsclaw Creek drainage basin. Thus the groundwater flow direction in the
upland area is to the south, southeast, and east. After converging on the main body of the ash
basin, the dominant groundwater flow direction is to the southeast toward the ash basin dike
and the dry ash landfill Phase I. Locally the water table gradient is high as groundwater
approaches and intercepts the dike and landfill. Groundwater passing beneath the landfill
discharges to the cove and unnamed stream to the east. Groundwater passing through and
beneath the dike discharges to Lake Norman.
In Section 2.5, drainage features within small catchments in the upland area of the site are
characterized as shallow hydrologic boundaries. These features are important elements of the
model as they represent the mechanism by which shallow groundwater discharges to the
surface. In the model, nearly 70% of recharge entering the basin discharges to the upland
drains, which is reasonable considering that the small catchments make up about two thirds of
the basin area.
5.2 Flow Model Sensitivity Analysis
It is important to understand the sensitivity of the flow model parameters on the predicted
hydraulic head field, so that the affects of changing the parameters are known. The sensitivity of
flow model parameters was tested by varying a subset of parameters by 20% above and below
17

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
the values used in the calibrated flow model. The sensitivity was evaluated by re -running the
model and comparing the NRMSE for each simulation (Table 5). A smaller NRMSE indicates
that the model is better calibrated (i.e., model -predicted hydraulic head values are a better
match to the actual or observed values). Using this approach, it was determined that NRMSE is
maximized and the flow model is most sensitive to changes in horizontal hydraulic conductivity
in the shallow aquifer, followed by changes in recharge outside of the ash basin. The least
sensitive flow model parameter tested (minimized NRMSE) was changed in the vertical
hydraulic conductivity in the shallow groundwater zone and transition zone.
5.3 Transport Model Calibration and Sensitivity
For the transport model calibration, the calibration parameters consisted of the constant source
concentrations, porosity and the linear sorption coefficient (Kd) for each COI. These parameters
were adjusted to minimize residual concentrations in target wells. The model assumed initial
concentrations within the groundwater system for all COls at the beginning of operations
approximately 50 years ago (1965). A source term matching the porewater concentrations for
each COI was applied within the active ash basin at the start of the calibration period in 1965,
and the Dry Ash Landfills and PV structural fill at the time they became active in 1984 and 2000,
respectively (see Section 2.3). The source concentrations were adjusted within the range of
porewater concentrations to match measured values in the downgradient monitoring wells
where exceedances of the 2L Standard or interim maximum allowable concentration (IMAC)
were observed for Cols in June 2015. Monitoring wells with measured values below the 2L
Standard or IMAC were also used during model calibration. Additionally, during transport model
calibration, the flow model parameters were also modified to refine the calibration. This iterative
process provided a better flow and transport calibration, as the spatial extent of elevated
constituents provides insight into groundwater flow directions and velocities.
The calibration results (comparing measured versus predicted model concentrations) are
provided in Table 6. In addition, Table 6 shows calibration source concentrations in the active
ash basin, Dry Ash landfill Phases I and II, and the PV structural fill. The locations of monitoring
wells are shown on Figures 7, 8, and 9. Note that the concentrations for each COI from model
calibration runs were used as initial (2015) concentrations for the Cap -in -Place scenario.
Detailed sensitivity analyses for porosity, dispersivity, and sorption were not completed as part
of CAP Part 2 as informal analysis indicated that sensitive parameters did not change due to
revisions to the model parameters. A decrease in the sorption coefficient (Kd) resulted in an
increase in the spatial extent in the modeled concentrations from the source areas. An increase
in porosity and dispersivity also resulted in an increase in the spatial extent in the modeled
concentrations from the source areas.
3 North Carolina Groundwater Rules; Title 15A, Subchapter 02L of the NC Administrative Code.
18

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
5.4 Advective Travel Times
Particle tracking was performed during model calibration to determine if advective travel times
are reasonable. Particles were placed at wells located near Lake Norman and selected
upgradient locations. The particle tracks are shown on Figure 14 for 18 wells and predicted
advective travel times are provided in Table 7.
5.5 One Year's Advective Travel Time from Residential Pumping Wells
As previously discussed, four residential pumping wells are included in the model domain,
pumping at a rate of 400 gpd each. The advective travel time one year from each well was
performed using MODPATH and is shown on Figure 15. The one-year advective travel time
pathlines do not intersect the Compliance Boundary at MSS.
6 SIMULATIONS OF CLOSURE SCENARIOS
The groundwater model, calibrated for flow and constituent fate and transport under existing
conditions, was used to evaluate two ash basin closure scenarios at MSS: the Existing
Conditions scenario and the Cap -in -Place scenario. These simulations produce flow and
transport results for conditions that are beyond the range of those considered during model
calibration. Thus, the model should be recalibrated and verified over time as new data become
available in order to reduce predictive uncertainty. The model domain developed for the Existing
Conditions scenario was applied without modification for the Cap -in -Place scenario. For this
scenario, recharge was set to zero over the ash basin and ash storage areas to simulate an
impermeable cap. Note that source concentrations remained active in the model, as long as
they remained saturated. The flow model parameters used for the Cap -in -Place model were the
same as those used for the Existing Conditions model.
6.1 Existing Conditions Scenario
The Existing Conditions scenario consists of modeling each constituent for 250 years into the
future using the calibrated flow and transport model. This time is sufficient to reach steady-state
concentrations across the site and at the Compliance Boundary. Concentrations will result in
values similar to the source concentrations for this scenario with source concentrations being
held at a constant value for the entire simulation period. Thereafter, the concentrations and
mass flux of dissolved constituents at the Compliance Boundary remain constant. This scenario
represents the most conservative scenario in terms of groundwater concentrations on- and off-
site, and COls discharging to Lake Norman.
The time to achieve a steady-state concentration plume depends on the source zone location
relative to the Compliance Boundary and its loading history—the ash basin becomes active in
1965, whereas the dry ash landfills and PV become active in 1983 and 1996, respectively.
Source zones close to the Compliance Boundary will cause steady-state conditions to be
reached faster. The time to steady-state concentration is dependent on the sorptive
characteristics of each COI. Sorptive COls will be transient for a longer time period as their peak
breakthrough concentration travels at a rate that is less than the groundwater pore velocity.
19

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Lower effective porosity will result in shorter times to achieve steady-state for sorptive and non
sorptive COIs.
6.2 Cap -In -Place Scenario
The Cap -in -Place scenario simulates the effects of covering the ash basin, dry ash landfill
Phases I and II, and the PV structural fill with an engineered cap. In the model, recharge at the
ash basin, dry ash landfills and PV structural fill, is set to zero. Groundwater flow is affected by
this scenario as the water table is lowered and groundwater velocities are reduced beneath the
capped areas. The water table just upgradient of the earthen dam in the ash basin is reduced by
approximately 10 feet, and in the ash basin between the PV structural fill and dry ash landfill
Phase II, it is reduced by approximately 1 foot.
In the model, the non-sorptive COls will move downgradient at the pore velocity of groundwater
and will be displaced by the passage of a single pore volume, while sorptive COI migration in
groundwater is retarded because of sorption onto and interaction with subsurface soil/rock. The
predicted COI concentrations from the 2015 calibration model are used as the initial
concentrations for the Cap -in -Place scenario since it is assumed (for modeling purposes) that
the corrective action was implemented at that time.
7 CLOSURE SCENARIO RESULTS
Closure scenario results are presented as predicted concentration versus time plots in
downgradient monitoring wells and as groundwater concentration maps for each modeled COI
on Figures 16 through Figure 184, as discussed in the following sub -sections. The constituent
concentrations were analyzed at four downgradient monitoring wells: A13-1 S, A13 -2S, GWA-1 S,
and MW -6S (Figure 7) for all COIs.
Plots of concentration versus time are referenced to 1965, since that is the year that the ash
basin became effective. Concentration maps are referenced to an initial time in 2015,
representing the end of the calibration period.
It should be noted that simulated concentrations in 2015, and thereafter can become slightly
higher than the PPBC under the Industrial Landfill No. 1 and at the southeastern boundary of
the domain near the cove of Lake Norman. Since there are not any source zones place in the
Industrial Landfill No. 1, and there are no plumes associated with some of these anamolously
high concentrations near Lake Norman, these can be regarded as inaccurately high values, and
thus are considered to be lower than the PPBC. This is likely due to unsaturated (dry) cells in
the shallow groundwater zone (model layers 5-7) and small numerical errors near the boundary.
All COls are affected by this in at least one of these locations, except for boron, chloride,
sulfate, and thallium.
20

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
7.1 Antimony
Figures 16 through 19 show predicted antimony concentrations at downgradient monitoring
wells AB -11S, AB -2S, GWA-1 S, and MW -6S for both Existing Conditions and Cap -in -Place
model scenarios. Under the Existing Conditions scenario, antimony initially exceeds the IMAC of
1 pg/L at the four downgradient wells, but then decreases below the IMAC over time. Note that
the proposed PPBC used for modeling (2.5 pg/L) is two and one-half times higher than the
IMAC; this results in predicted antimony concentrations that exceed the IMAC. The Cap -in -
Place scenario has little effect on concentrations over time (the curves are similar to Existing
Conditions). Figures 20 to 22 show initial (2015) antimony concentrations in the shallow, deep
and bedrock groundwater zones. In 2015, the Existing Conditions scenario (Figures 23 to 25),
and the Cap -in -Place scenario (Figures 26 to 28), antimony is predicted to remain below the
PPBC, but to remain above the IMAC at the model interface or Compliance Boundary in all
groundwater zones. No observable changes are noted for the Cap -in -Place scenario, as
compared to the Existing Conditions scenario.
7.2 Arsenic
Figures 29 through 32 show predicted arsenic concentrations at the downgradient monitoring
wells for both model scenarios. The curves show that under the Existing Conditions scenario,
arsenic concentrations are predicted to remain steady or slightly decline throughout the
modeled period and do not exceed the 2L Standard (10 pg/L) or the PPBC (5 pg/L) at the
downgradient well locations. The Cap -in -Place scenario has little effect on predicted arsenic
concentrations (i.e., the two curves are similar). Figures 33 through 35 show arsenic in 2015,
and Figures 36 through 38 show predicted arsenic in 2115 for the Existing Conditions scenario
in 2115. Figures 39 through 41 show arsenic concentrations under the Cap -in -Place scenario in
2115. In 2015 and under both scenarios in 2115, in all groundwater zones, arsenic remains
below the 2L Standard and PPBC at the model interface or Compliance Boundary.
7.3 Barium
Figures 42 through 45 show predicted barium concentrations at the downgradient monitoring
wells under both scenarios. The concentration curves show that under existing conditions,
barium does not exceed the 2L Standard (700 pg/L), and maintains or decreases below the
PPBC (157.3 pg/L) for both scenarios. The Cap -in -Place scenario has little effect on barium
concentrations as the two curves are similar. Figures 46 to 48 show initial (2015) barium
concentrations in the shallow, deep and bedrock groundwater zones. Figures 49 to 54 show that
barium is predicted to remain below the 2L Standard and PPBC at the model interface or
Compliance Boundary under the Existing Conditions and Cap -in -Place scenarios (applies to all
groundwater zones). For the Cap -in -Place scenario, barium concentrations remain relatively
unchanged, relative to the Existing Conditionsscenario.
21

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
7.4 Beryllium
Figures 55 through 58 show predicted beryllium concentrations at the downgradient monitoring
wells. The figures show that under both scenarios beryllium remains below the IMAC (4 pg/L) at
AB -1 S, AB -2S, GWA-1 S, but exceeds the IMAC at MW -6S. Beryllium exceeds the PPBC (1
pg/L) at all of the wells with the exception of AB -2S. The Cap -in -Place scenario has little effect
on predicted concentrations, except at MW -6S, where concentrations are lower for the Cap -in -
Place scenario, although beryllium concentrations are predicted to remain above the IMAC.
Figures 59 through 61 show predicted beryllium concentrations in shallow, deep and bedrock
zones in 2015, and Figures 62 through 64 show beryllium concentrations in 2115 (after 100
years) for the Existing Conditions scenario. Beryllium is predicted to remain below the IMAC, but
to increase above the PPBC in all groundwater zones at the Compliance Boundary in 2015.
Under the Existing Conditions scenario, beryllium is predicted to exceed the IMAC in 2115 in the
shallow and deep groundwater zones, and to exceed the PPBC in all groundwater zones, at the
model interface or Compliance Boundary. For the Cap -in -Place scenario (Figures 65 to 67), the
lateral extent of the beryllium plume is slightly reduced relative to the Existing Conditions
scenario, and the IMAC is not exceeded at the model interface or Compliance Boundary in the
shallow and deep groundwater zones, while the PPBC is exceeded in all groundwater zones
7.5 Boron
Figures 68 through 71 show predicted boron concentrations at the four downgradient monitoring
wells. For the Existing Conditions and Cap -in -Place scenarios, boron exceeds the 2L Standard
(700 pg/L) at AB -1 S and MW -6S. Boron exceeds the PPBC (100 pg/L) for both model scenarios
at all four wells, except for the Cap -in -Place scenario at GWA-1 S. The Cap -in -Place scenario
shows reduced concentrations as compared to Existing Conditions results. Figures 72 through
74 show boron concentrations in the shallow, deep and bedrock zones in 2015, while Figures
75 through 77 show them in 2115, or in 100 years, under the Existing Conditions scenario, and
Figures 78 through 80 show them under the Cap -in -Place scenario in 2115. Boron is predicted
to exceed the 2L Standard at the model interfaceor Compliance Boundary in 2015, and is
predicted to exceed the 2L Standard at the model interface, in all groundwater zones for both
scenarios in 2115. The lateral extent of the boron plume is slightly reduced under the Cap -in -
Place scenario, relative to the Existing Conditions scenario.
7.6 Chloride
Figures 81 through 84 show predicted chloride concentrations at the downgradient monitoring
wells for both scenarios. Chloride concentrations reach a steady-state at all four wells during the
modeled period and remain below the 2L Standard (250,000 pg/L). Chloride exceeds the PPBC
(3,500 pg/L) under both modeled scenarios at all of the wells over time, except for the Cap -in -
Place scenario at GWA-1 S where chloride concentrations decrease to a level below the PPBC.
Considering the Cap -in -Place scenario, chloride decreases substantially relative to the Existing
Conditions scenario at MW -6S but exceeds the predicted Existing Conditions concentrations at
AB -1 S. Figures 85 through 87 show predicted chloride concentrations in the shallow, deep and
bedrock zones in 2015, and Figures 88 through 90 show them in 2115 (after 100 years for
Existing Conditions). Figures 91 through 93 show predicted chloride in 2115 under the Cap -in -
22

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Place scenario. Chloride is predicted to remain slightly below the 2L Standard (and exceed the
PPBC) at the model interface or Compliance Boundary under both scenarios in all groundwater
zones. After 100 years, the lateral extent of the chloride plume is only slightly reduced by
capping the ash.
7.7 Chromium
Figures 94 through 97 show predicted chromium concentrations at the downgradient monitoring
wells. Under the Existing Conditions and Cap -in -Place scenarios, chromium exceeds the 2L
Standard (10 pg/L) at GWA-1 S and MW -6S, and declines below the 2L Standard at AB -1 S and
AB -2S. Note that the PPBC (11.3 pg/L) is higher than the standard; this results in predicted
chromium concentrations that exceed the standard. Note that MW -6S is the only well where
chromium will exceed the PPBC. For the Cap -in -Place scenario, predicted chromium
concentrations are substantially lower at two of the wells (GWA-1 S and MW -6S) as compared to
the Existing Conditions scenario. Figures 98 through 100 show chromium concentrations in the
shallow, deep and bedrock groundwater zones in 2015, and Figures 101 through 103 show
them in 2115 (after 100 years) under the Existing Conditions scenario. Figures 104 to 106 show
Cap -in -Place scenario chromium concentrations in 2115. Under both scenarios chromium
concentrations are predicted to exceed both the 2L Standard and PPBC at the model interface
or Compliance Boundary (all groundwater zones). Under the Cap -in -Place scenario, the extent
of the chromium plume in 2115 and maximum concentrations are only slightly reduced relative
to the Existing Conditions scenario.
7.8 Cobalt
Figures 107 through 110 show predicted cobalt concentrations at the downgradient monitoring
wells. For the Existing Conditions scenario, predicted cobalt concentrations increase at two
wells (GWA-1 S and MW -6S) and decrease at two wells (AB -1 S and AB -2S). The cobalt at one
well (AB -2S) declines below the IMAC (1 pg/L). Note that the PPBC used for modeling (2.5
pg/L) is two and one-half times higher than the standard; this results in predicted cobalt
concentrations that exceed the IMAC. Under the Cap -in -Place scenario, predicted cobalt
increases or remains the same in all four wells, and below the Existing Conditions
concentrations at two wells (GWA-1 S and MW -6S) and increase above the Existing Conditions
concentrations at the other two wells (AB -1 S and AB -2S). Figures 111 through 113 show cobalt
concentrations in the shallow, deep and bedrock zones in 2015, and Figures 114 through 116
show them in 2115 (after 100 years under the Existing Conditions scenario). Figures 117 to 119
show predicted cobalt under the Cap -in -Place scenario. The predicted cobalt concentrations
exceed the IMAC and PPBC at the model interface or Compliance Boundary in 2115 under both
model scenarios (all groundwater zones). Relative the Existing Conditions scenario, the lateral
extent of the cobalt plumes decrease slightly under the Cap -in -Place scenario.
7.9 Hexavalent Chromium
Figures 120 through 123 show predicted hexavalent chromium concentrations at the
downgradient monitoring wells. For both scenarios, hexavalent chromium is predicted to decline
steeply at three of the wells over the period, while the fourth well (GWA-1 S) decreases only
23

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
slightly below the PPBC (2.8 pg/L). All four wells show that predicted hexavalent chromium
remains above the NCDHHS HSL (0.07 pg/L) for the duration of the modeled period (both
scenarios). Note that capping the ash has little effect on hexavalent chromium concentrations,
as the two curves are similar. Figures 124 through 126 show hexavalent concentrations in the
shallow, deep and bedrock zones in 2015, and Figures 127 to 129 show predicted
concentrations in 2115 (Existing Conditions scenario). Figures 130 to 132 show predicted
hexavalent chromium concentrations in 2115. In 2015 and 2115, hexavalent chromium
concentrations are predicted to exceed the NCDHHS HSL at the model interface or Compliance
Boundary in all groundwater zones (both future model scenarios). Hexavalent chromium
concentrations remain below the PPBC at the model interface or Compliance Boundary in all
groundwater zones in 2015 and in 2115 under both scenarios. For the Cap -in -Place scenario,
predicted hexavalent chromium concentrations are nearly unchanged, or slightly increase
relative to the Existing Conditions scenario.
7.10 Selenium
Figures 133 through 136 show predicted selenium concentrations at the four downgradient
monitoring wells. Under the Existing Conditions and Cap -in -Place scenarios, selenium
concentrations are predicted to decrease significantly at three wells, but to a lesser extent at
one well (GWA-1S). The predicted selenium concentrations remain below both the IMAC (20
pg/L) and the PPBC (10 pg/L). Note that the Cap -in -Place scenario has a minimal effect on
predicted selenium concentrations, as the two curves are similar. Figures 137 through 139 show
predicted selenium concentrations in the shallow, deep and bedrock zones in 2015, and Figures
140 through 142 show them in 2115 under the Existing Conditions scenario. Figures 143
through 145 show predicted selenium concentrations in 2115 under the Cap -in -Place scenario.
Selenium is predicted to remain below the IMAC and PPBC in 2015 and 2115 at the model
interface or Compliance Boundary under both modeled scenarios in all groundwater zones.
7.11 Sulfate
Figures 146 through 149 show predicted sulfate concentrations at the four monitoring wells. For
the Existing Conditions scenario, sulfate increases above the PPBC (1,460 pg/L) and achieves
steady-state concentrations at each of the selected wells during the modeled period. Sulfate
concentrations are predicted to remain below the 2L Standard (250,000 pg/L) at the four
selected downgradient wells. The concentration of sulfate is predicted to decrease under the
Cap -in -Place scenario in all four wells, relative to the Existing Conditions scenario. Figures 150
through 152 show predicted sulfate concentrations in the shallow, deep and bedrock zones in
2015, and Figures 153 through 155 show sulfate concentrations in 2115 under the Existing
Conditions scenario. Figures 156 through 158 show predicted sulfate under the Cap -in -Place
scenario in 2115. Sulfate is predicted to exceed the PPBC, but to remain below the 2L
Standard, at the model interface or Compliance Boundary in 2015 and 2115 (both model
scenarios in all groundwater zones). Although, in the Existing Conditions scenario, predicted
sulfate concentrations approach the 2L Standard at the model interface on the southern end of
the site. Under the Cap -in -Place scenario, the lateral extent of the sulfate plume is somewhat
reduced after 100 years, relative to the Existing Conditions scenario.
24

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
7.12 Thallium
Figures 159 through 162 show predicted thallium concentrations at the four downgradient
monitoring wells. Under the Existing Conditions scenario, thallium concentrations in all of the
wells are predicted to remain unchanged or decrease below the PPBC (0.5 pg/L). The thallium
concentrations decrease below the IMAC (0.2 pg/L) at one well (AB -2S). The Cap -in -Place
scenario has little effect on concentrations, as the two curves are similar. Note that the PPBC
used for modeling (0.5 pg/L) is one and one-half times higher than the IMAC; this results in
predicted thallium concentrations that exceed the IMAC. Figures 163 through 165 show
predicted thallium concentrations in the shallow, deep and bedrock groundwater zones in 2015,
and Figures 166 through 168 show thallium in 2115 under the Existing Conditions scenario.
Figures 169 through 171 show predicted thallium concentrations under the Cap -in -Place
scenario in 2115. Thallium is predicted to exceed the IMAC, but remain below the PPBC, at the
model interface or Compliance Boundary in 2015 and 2115 (both model scenarios in all
groundwater zones). Under the Existing Conditions scenario, predicted thallium concentrations
remain relatively unchanged from 2015 to 2115. Under the Cap -in -Place scenario, the extent of
the thallium plume in 2115 is similar to that under the Existing Conditions scenario.
7.13 Vanadium
Figures 172 through 175 show predicted vanadium concentrations at the four downgradient
monitoring wells. Under the Existing Conditions scenario, vanadium concentrations decline
below the PPBC (3.9 pg/L) in two wells (AB -1 S and AB -2S) and remain near the PPBC in the
other two wells (GWA-1 S and MW -6S). Note that the PPBC used for modeling (3.9 pg/L) is 13
times higher than the IMAC of 0.3 pg/L; this results in predicted cobalt concentrations that
exceed the IMAC. Figures 176 through 178 show vanadium concentrations in the shallow, deep
and bedrock zones in 2015, and Figures 179 through 181 show vanadium levels in 2115 under
the Existing Conditions scenario . Figures 182 through 184 show predicted vanadium
concentrations under the Cap -in -Place scenario in 2115. Vanadium is predicted to exceed the
IMAC, but remain below the PPBC, at the model interface or Compliance Boundary in 2015 and
2115 for both model scenarios (all groundwater zones). Under the Existing Conditions scenario,
vanadium concentrations in the shallow zone increase and spread during the period from 2015
to 2115. The extent of the vanadium plume and maximum concentrations in 2115 are similar for
both scenarios.
8 SUMMARY
8.1 Model Assumptions and Limitations
The model assumptions include the following:
• The steady-state flow model was calibrated to hydraulic heads measured at observation
wells in June/July 2015 and considered the ash basin water level. The model is not
calibrated to transient water levels over time, recharge or river flow. A steady-state
calibration does not consider changes in groundwater storage and groundwater flux to
surface water with time.
25

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
• In the MODFLOW groundwater flow model, fractured bedrock was simulated as an
equivalent porous medium.
• The model was calibrated by adjusting the constant source concentrations at the ash
basin and ash storage areas to reasonably match 2015 COI concentrations in
groundwater.
• For the purposes of numerical modeling and comparing closure scenarios, it is assumed
that the selected closure scenario was completed in 2015.
• Predictive simulations were performed and steady-state flow conditions were assumed
from the time that the ash basin and ash storage areas were placed in service (1965)
through the current time until the end of the predictive simulations (2265).
• COI source zone concentrations at the ash basin and ash storage areas were applied
uniformly within each source area and assumed to be constant with respect to time for
transport model calibration.
• The uncertainty in model parameters and predictions has not been quantified; therefore,
the error in the model predictions is not known. It is assumed the model results are
suitable for a relative comparison of closure scenario options.
• Since Lake Norman is modeled as a constant head boundary in the numerical model, it
will not be possible to assess the effects of pumping wells or other groundwater sinks
that are near this boundary.
• The model does not account for varying geochemical conditions such as pH and redox
potential that could affect COI mobility and change modeling results. As identified by
HDR, site-specific geochemistry and geochemical modeling will be considered in CAP
Part 2.
8.2 Model Predictions
The model predictions are summarized as follows:
• Antimony — The IMAC is predicted to be exceeded, while the concentrations remain
below the PPBC at the model interface or Compliance Boundary for Existing Conditions
and Cap -in -Place scenarios.
• Arsenic — The predicted concentrations remain below the 2L Standard and PPBC at the
model interface or Compliance Boundary under the Existing Conditions and Cap -in -
Place scenarios.
• Barium — The predicted concentrations remain below the 2L Standard and the PPBC at
the model interface or Compliance Boundary under the Existing Conditions and the Cap-
in -Place scenarios.
• Beryllium — The IMAC is predicted to be exceeded, while the concentrations remain
below the PPBC at the model interface or Compliance Boundary for the Existing
Conditions scenario.
K•

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
• Boron — The 2L Standard and PPBC are predicted to be exceeded at the model
interface or Compliance Boundary under the Existing Conditions and the Cap -in -Place
scenarios.
• Chloride — The predicted concentrations remain below the 2L Standard, while the
concentrations exceed the PPBC at the model interface or Compliance Boundary under
the Existing Conditions and Cap -in -Place scenarios.
• Chromium — The 2L Standard and PPBC at the model interface or Compliance
Boundary are predicted to be exceeded under Existing Conditions and Cap -in -Place
scenarios.
• Cobalt — The IMAC and PPBC at the model interface or Compliance Boundary are
predicted to be exceeded for Existing Conditions and Cap -in -Place scenarios.
• Hexavalent chromium — The NCDHHS HSL Standard is predicted to be exceeded, while
concentrations remain below the PPBC at the model interface or Compliance Boundary
under Existing Conditions and Cap -in -Place scenarios.
• Selenium — The predicted concentrations remain below the IMAC and PPBC at the
model interface or Compliance Boundary under the Existing Conditions and Cap -in -
Place scenarios.
• Sulfate — The predicted concentrations remain below the 2L Standard, but exceed the
PPBC, at the model interface or Compliance Boundary under the Existing Conditions
and Cap -in -Place scenarios.
• Thallium — The IMAC is predicted to be exceeded, while the concentrations remain
below the PPBC at the model interface or Compliance Boundary for Existing Conditions
and Cap -in -Place scenarios.
• Vanadium — The IMAC is predicted to be exceeded, while the concentrations remain
below the PPBC at the model interface or Compliance Boundary for Existing Conditions
and Cap -in -Place scenarios.
27

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
9 REFERENCES
Daniel, C.C., III, 2001, Estimating ground -water recharge in the North Carolina Piedmont for
land use planning [abs.], in 2001 Abstracts with Programs, 50th Annual Meeting,
Southeastern Section, April 5-6, 2001: Raleigh, N.C., The Geological Society of
America, v. 33, no. 2, p. A-80.
Haven, W.T. Introduction to the North Carolina Groundwater Recharge Map -Groundwater
Circular Number 19, North Carolina Department of Environment and Natural Resources
Division of Water Quality, Groundwater Section.
HDR. 2015a. Comprehensive Site Assessment Report, Marshall Steam Station Ash Basin,
September 2015.
HDR, 2015b. Corrective Action Plan Part 1. Marshall Steam Station Ash Basin, November 20,
2015.
Langley, W.G. and Oz, S. 2015. Soil Sorption Evaluation Marshall Steam Station, UNC -
Charlotte, October 2015.
LeGrand, H. E. 2004. A Master Conceptual Model for Hydrogeological Site Characterization in
the Piedmont and Mountain Region of North Carolina, A Guidance Manual, North
Carolina Department of Environment and Natural Resources Division of Water Quality,
Groundwater Section.
Niswonger, R.G., Panday, S., and Ibaraki, M. 2011. MODFLOW-NWT, A Newton formulation for
MODFLOW-2005: U.S. Geological Survey Techniques and Methods 6-A37, 44 p.
Zheng, C. and Bennett, G. 2002. Applied Contaminant Transport Modeling, Second Edition,
Wiley Interscience.
Zheng, C. and Wang, P. 1999. MT3DMS, A modular three-dimensional multi -species transport
model for simulation of advection, dispersion and chemical reactions of contaminants in
groundwater systems, Documentation and Users Guide, U.S. Army Engineer Research
and Development Center Contract Report SERDP-99-1, Vicksburg, MS, 202 p.
28

This page intentionally left blank

This page intentionally left blank

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
TABLES
Table 1 MODFLOW and MT3DMS Input Packages Utilized
Table 2 Model Hydraulic Conductivity
Table 3 Observed vs. Predicted Hydraulic Head
Table 4 Model Effective Porosity
Table 5 Flow Parameter Sensitivity Analysis
Table 6 Transport Model Calibration Results
Table 7 Predicted Advective Travel Time to Boundary

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 1 MODFLOW and MT3DMS Input Packages Utilized
MODFLOW Input Package
Description
Name (NAM)
Contains the names of the input and output files used in the
model simulation and controls the active model program
Basic (BAS)
Specifies input packages used, model discretization, number of
model stress periods, initial heads and active cells
Contains finite -difference grid information, including the number
Discretization (DIS)
and spacing of rows and columns, number of layers in the grid,
top and bottom model layer elevations and number of stress
periods
Specified Head and
Specifies a head and/or a concentration that remains constant
Concentration (CHD)
throughout the simulation
Drain (DRN)
Acts as a "drain" to remove water from the groundwater system.
Simulates drainage areas within the model
Recharge (RCH)
Simulates areal distribution of recharge to the
groundwater system
Newton Solver (NWT)
Contains input values and the Newton and matrix
solver options
Upstream Weighting (UPW)
Replaces the LPF and/or BCF packages and contains the input
required for internal flow calculations
Flow Transfer Link File (LMT)
Used by MTDMS to obtain the location, type, and flow rates of
all sources and sinks simulated in the flow model
MT31DMS Input Package
Description
Flow Transfer Link File (FTL)
Reads the LMT file produced by MODFLOW
Basic Transport Package (BTN)
Reads the MODFLOW data used for transport simulations and
contains transport options and parameters
Advection (ADV)
Reads and solves the selected advection term
Dispersion (DSP)
Reads and solves the dispersion using the explicit finite -
difference formulation
Source and Sink Mixing (SSM)
Reads and solves the concentration change due to sink/source
mixing using the explicit finite -difference formulation
Chemical Reaction (RCT)
Reads and solves the concentration change due to chemical
reactions using the explicit finite -difference formulation
Generalized Conjugate Gradient
Solves the matrix equations resulting from the implicit solution of
(GCG) Solver
the transport equation

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 2 Model Hydraulic Conductivity
Model
Layer
Hydrostrati-
graphic Unit
Measured Value
Range'
Calibrated Model Value
Horizontal
Hydraulic
Conductivity
ft/day
Horizontal Hydraulic
Conductivity
ft/day
Vertical Hydraulic
Conductivity
ft/day
1-4
Ash
0.67-3.72
Z-2
3.80
0.76
2-4
Fill
0.33-0.83
Z-3
0.05
0.05
Z-13
2.13
2.13
Z-14
2.15
2.15
Alluvium
Z-15
11.46
1.15
Z-9
1.79
0.36
5-6
M1
4.44-2.18
Z-10
12.00
1.20
Z-4
3.05
0.31
7
M2
5.95-2.50
Z-5
7.49
0.75
Z-7
1.02
0.10
Z-16
14.00
2.80
Z-8
2.41
0.48
Z-6
5.79
1.16
8
TZ
7.7-2.3
TZ
2.50
0.25
9-10
BR
0.96-7.34
BR
0.15
0.15
'Range = geometric mean +/- one standard deviation (see CSA Report Tables 11-9 and 11-10)

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 3 Observed vs. Predicted Hydraulic Head
Well Name
Model Layer
Measured WL
ft MSL
Modeled WL
ft MSL
Residual
ft MSL
AB -10D
8
789.04
791.85
-2.81
AB -10S
2
789.16
791.79
-2.63
AB-10SL
4
788.98
791.82
-2.84
AB -11 D
8
795.10
796.39
-1.29
AB -11S
6
793.18
796.22
-3.04
AB12D
8
790.86
792.73
-1.87
AB -12S
2
790.69
792.61
-1.92
AB-12SL
4
790.50
792.68
-2.18
AB -13D
8
797.67
802.25
-4.58
AB13S
2
797.30
802.08
-4.78
AB -14D
8
809.51
816.90
-7.39
AB -14S
6
808.68
816.98
-8.30
AB-15BR
9
804.03
808.21
-4.18
AB -15D
8
802.75
806.76
-4.01
AB -15S
2
804.46
806.91
-2.45
AB-15SL
5
800.89
806.66
-5.77
AB -16D
8
813.95
812.08
1.87
AB -16S
6
814.26
811.79
2.47
AB -17D
8
818.96
821.93
-2.97
AB -17S
2
818.42
821.94
-3.52
AB -18D
8
817.86
820.13
-2.27
AB -18S
6
817.69
820.12
-2.43
AB -1 BR
9
771.16
766.27
4.89
AB -1 D
8
770.08
764.81
5.27
AB -1S
6
767.10
764.74
2.36
AB -20D
8
827.48
829.91
-2.43
AB -20S
6
829.31
829.88
-0.57
AB -21 D
8
792.47
798.82
-6.35
AB -21 S
6
791.30
798.90
-7.60
AB -21D
8
766.60
767.60
-1.00
AB -2S
6
760.71
767.53
-6.82
AB -31D
8
797.23
794.34
2.89
AB -3S
2
798.48
794.60
3.88
AB -41D
8
799.61
797.83
1.78
AB -4S
2
799.61
797.80
1.81
AB-4SL
4
799.36
797.81
1.55
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 3 Observed vs. Predicted Hydraulic Head (continued)
Well Name
Model Layer
Measured WL
ft MSL
Modeled WL
ft MSL
Residual
ft MSL
AB -513R
9
799.25
801.58
-2.33
AB -51D
9
799.34
801.66
-2.32
AB -5S
2
799.45
801.75
-2.30
AB-6BR
9
817.10
813.33
3.77
A13 -61D
8
817.86
813.84
4.02
AB -6S
2
819.78
813.73
6.05
AB -7D
8
813.33
809.24
4.09
AB -7S
6
814.17
809.28
4.89
AB-9BR
9
790.62
793.02
-2.40
AB -91D
8
789.31
791.65
-2.34
AB -9S
6
789.75
791.67
-1.92
AL -1 D
8
773.72
779.96
-6.24
AL -1S
6
778.71
780.01
-1.30
AL -213R
9
803.63
799.30
4.33
AL -21D
8
801.67
799.44
2.23
AL -2S
6
800.18
799.48
0.70
AL -31D
8
805.30
804.86
0.44
AL -3S
4
805.98
804.77
1.21
AL -4D
8
812.75
804.68
8.07
GWA-1 BR
9
764.34
771.67
-7.33
GWA-1 D
8
760.78
766.48
-5.70
GWA-1 S
6
760.84
766.46
-5.62
GWA-21D
8
802.69
804.08
-1.39
GWA-2S
6
803.14
804.13
-0.99
GWA-31D
8
833.00
833.19
-0.19
GWA-3S
6
830.29
833.21
-2.92
GWA-41D
8
843.45
831.16
12.29
GWA-4S
6
843.57
831.31
12.26
GWA-51D
8
812.79
811.87
0.92
GWA-5S
6
812.57
811.99
0.58
GWA-61D
8
803.21
802.38
0.83
GWA-6S
6
803.44
802.34
1.10
GWA-7D
8
800.03
792.62
7.41
GWA7S
6
797.02
792.41
4.61
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 3 Observed vs. Predicted Hydraulic Head (continued)
Max 846.36 Sum s.e
Measured WL
Modeled WL
Residual
Well Name
Model Layer
NRMSE
0.055
ft MSL
ft MSL
ft MSL
GWA-9BR
9 846.36
834.66
11.70
MW-14BR
9 773.78
783.27
-9.49
Max 846.36 Sum s.e
1576.31
Min 760.71 No. of wells
72.00
Max -Min 85.65 RMSE
4.68
NRMSE
0.055
Notes:
1. S or SL — shallow groundwater zone
2. D — deep groundwater zone
3. BR — bedrock groundwater zone
4. WL — water level
5. ft - feet
6. MSL — mean sea level

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 4 Model Effective Porosity
Model
Layer
Hydrogeologic
Unit
Effective Porosity
1 -3
Ash and Dike Materials
0.15
4
Dike Materials
0.15
5-6
M1 - Saprolite and Alluvium
0.15
7
M2 - Saprolite
0.15
8
Transition Zone
0.01
9-10
Bedrock
0.005
Table 5 Flow Parameter Sensitivity Analysis
Notes:
1. NRMSR - normalized root mean squared error
2. Kh - horizontal hydraulic conductivity
3. Kv - vertical hydraulic conductivity
Calibrated
Calibrated +20%
Calibrated -20%
Parameter
NRMSR
NRMSR (Head)
%
NRMSR (Head)
%
(Head)
Shallow
0.0552
1.10
0.0555
1.65
Zone Kh
Shallow
0.0546
0.00
0.0546
0.00
Zone Kv
Transition
0.0547
0.18
0.0546
0.00
Zone Kh
0.0546
Transition Zone
0.0546
0.00
0.0546
0.00
Kv
Recharge
0.0547
0.18
0.0564
3.30
ex. Ash Bbasin
Recharge
0.0544
-0.36
0.0556
1.83
Ash Bbasin
Notes:
1. NRMSR - normalized root mean squared error
2. Kh - horizontal hydraulic conductivity
3. Kv - vertical hydraulic conductivity

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results
COI
Monitoring Well
Measured
Concentration
p/L
Predicted
Concentration
N/L
Antimony
Ash Basin Constant
Concentration Range
= 0.5 - 25 pg/L
Ash Storage
Area Concentration
= 0.5 pg/L
PV Structural
Fill Concentration
= 25 pg/L
Sorption
Coefficient [Kd] = 1
mL/g
AB -10S
0.75
0.50
AB-10SL
1.30
1.00
AB -10D
0.50
2.48
AB -11 D
0.50
2.49
AB -11 S
2.50
1.00
AB12D
0.54
2.50
AB -12S
0.50
0.50
AB-12SL
0.18
0.50
AB -13D
0.97
5.15
AB13S
21.80
20.00
AB -14D
0.66
2.47
AB -14S
1.00
1.00
AB-15BR
0.16
2.90
AB -15D
0.18
2.87
AB -15S
0.18
15.58
AB-15SL
0.25
14.46
AB -16D
0.50
2.52
AB -16s
6.20
2.64
AB -17D
0.64
2.49
AB -17S
0.50
1.00
AB -18D
0.22
2.50
AB -18S
0.50
0.50
AB -18S
0.50
0.50
AB -1 BR
0.50
2.48
AB -1 D
0.50
2.48
AB -1S
0.50
0.75
AB -20D
0.32
2.50
AB -20S
26.60
25.00
AB -21 D
0.50
2.46
AB -21 S
0.50
0.50
AB -21D
0.50
1.24
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Antimony
(cont.)
A13 -2S
0.22
0.36
AB -3D
0.57
2.49
AB -3S
0.50
0.50
AB -4D
0.17
2.10
AB -4S
0.30
0.50
AB-4SL
0.91
1.00
AB-5BR
0.19
2.50
AB -51D
0.16
2.22
AB -5S
2.50
1.00
AB-6BR
1.30
2.45
AB -61D
0.50
2.45
AB -6S
0.50
0.40
AB -7D
0.41
2.50
A13 -81D
0.44
2.50
AB -8S
0.50
1.00
AB-9BR
0.30
2.49
AB -91D
0.23
2.49
A13 -9S
0.50
0.22
AL -11D
0.80
2.45
AL -1S
0.30
0.52
AL -2 B R
0.31
2.50
AL -21D
0.50
2.04
AL -2S
0.40
0.50
AL -31D
0.16
2.50
AL -3S
12.20
0.37
AL -41D
0.50
2.04
GWA-1 BR
0.16
2.49
GWA-1 D
0.92
2.49
GWA-1 S
0.26
2.49
GWA-21D
4.10
1.79
GWA-2S
0.50
2.34
GWA-31D
0.50
2.08
GWA-3S
0.31
1.35
GWA-41D
0.50
0.20
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Antimony
(cont.)
GWA-4S
0.27
GWA-51D
0.50
0.03
GWA-5S
0.79
GWA-61D
11.40
2.50
GWA-6S
0.66
0.96
GWA-7D
0.50
2.34
GWA-7S
0.50
0.93
MW -10D
0.50
2.49
MW -10S
0.45
2.17
MW -11 D
0.50
2.08
MW -11 D
0.45
2.08
MW -12D
0.50
2.36
MW -12S
0.73
1.41
MW -13D
0.50
2.44
MW -13S
0.50
1.64
MW-14BR
0.22
2.49
MW -14D
0.23
1.89
MW -14S
2.50
1.22
MW -4D
0.50
MW -7S
0.50
0.82
Arsenic
Ash Basin Constant Concentration Range = 10 - 6,400 pg/L
Ash Storage Area Concentration Range = 10 - 150 pg/L
PV Structural Fill Concentration = 115 pg/L
Sorption Coefficient [Kd] = 48 mL/g
AB -10D
1.2
5.0
AB -10S
410.0
400.0
AB-10SL
1330.0
1350.0
AB -11 D
0.3
5.0
AB -11S
2.8
5.0
AB -12D
1.3
5.0
AB -12S
145.0
150.0
AB-12SL
6380.0
6400.0
AB -13D
0.9
12.3
AB -13S
591.0
650.0
AB -14D
0.9
5.0
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Arsenic
(cont.)
AB -14S
799.0
800.0
AB-15BR
0.4
5.0
AB -15D
0.6
5.0
AB -15S
511.0
513.1
AB-15SL
864.0
353.6
AB -16D
0.1
5.0
AB -16s
0.7
5.2
AB -17D
1.5
5.0
AB -17S
238.0
240.0
AB -18D
2.8
5.0
AB -18s
2060.0
2450.0
A13-1 BR
0.3
5.0
AB -1 D
0.5
5.0
A13 -1S
5.7
4.8
AB -20D
0.2
5.0
AB -20S
95.4
115.0
AB -21 D
0.5
5.0
AB -21 S
439.0
440.0
AB -21D
0.3
5.0
A13 -2S
0.3
2.4
AB -31D
0.8
5.0
A13 -3S
2.3
10.0
AB -41D
0.4
5.0
AB -4S
1.3
10.0
AB-4SL
923.0
930.0
AB-5BR
1.7
5.0
AB -51D
2.1
5.0
A13 -5S
9.9
10.0
AB-6BR
6.6
5.1
A13 -61D
1.8
5.1
AB -6S
3180.0
3719.9
AB -7D
2.6
5.0
AB -81D
1.3
5.0
A13 -8S
103.0
105.0
AB-9BR
0.9
5.0
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
la /L
Predicted
Concentration
N /L
Arsenic
(cont.)
AB -91D
1.0
5.0
A13 -9S
1.0
8.8
AL -11D
0.6
5.0
AL -1S
2.7
8.9
AL -2 B R
0.7
5.0
AL -21D
0.6
5.5
AL -2S
1.2
150.0
AL -31D
0.7
5.0
AL -3S
189.0
99.9
AL -41D
0.4
5.0
GWA-1 BR
0.3
5.0
GWA-1 D
0.7
5.0
GWA-1 S
0.2
5.0
GWA-21D
0.4
5.0
GWA-2S
0.5
5.0
GWA-31D
0.5
5.0
GWA-3S
0.2
4.9
GWA-41D
2.9
3.2
GWA-4S
0.5
GWA-51D
0.2
2.2
GWA-5S
1.4
GWA-61D
0.9
5.0
GWA-6S
0.1
4.9
GWA-7D
0.9
5.0
GWA-7S
2.4
4.8
MW -10D
0.2
5.0
MW -10S
0.5
5.0
MW -11 D
1.6
5.0
MW -11 D
0.3
5.0
MW -12D
0.4
5.0
MW -12S
0.5
4.9
MW -13D
0.5
5.0
MW -13S
0.1
5.0
MW-14BR
0.3
5.0
MW -14D
0.5
5.0
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Arsenic
(cont.)
MW -14S
0.5
4.9
MW -4
2.5
MW -4D
0.3
MW -7S
10.4
4.9
Barium
Ash Basin Constant
Concentration Range
= 14 - 780 pg/L
Ash Storage Area
Concentration Range
= 180 - 570 pg/L
PV Structural
Fill Concentration
= 460 pg/L
Sorption
Coefficient [Kd] = 1
mL/g
AB -10D
420.0
157.3
AB -10S
160.0
160.0
AB-10SL
370.0
380.0
AB -11 D
12.0
157.3
AB -11 S
110.0
110.0
AB -12D
180.0
157.3
AB -12S
330.0
350.0
AB-12SL
780.0
800.0
AB -13D
200.0
160.4
AB -13S
390.0
485.0
AB -14D
150.0
157.3
AB -14S
44.0
50.0
AB-15BR
130.0
157.3
AB -15D
210.0
157.3
AB -15S
580.0
382.8
AB-15SL
450.0
325.3
AB -16D
150.0
157.3
AB -17D
33.0
157.3
AB -17S
240.0
250.0
AB -18D
46.0
157.3
AB -18s
340.0
350.0
AB -1 BR
21.0
157.3
AB -1 D
440.0
157.3
AB -1S
100.0
150.4
AB -20D
58.0
157.3
AB -20S
460.0
460.0
AB -21 D
200.0
157.3
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Barium
(cont.)
AB -21 S
630.0
630.0
AB -21D
100.0
157.3
AB -2S
92.0
62.0
AB -31D
160.0
157.3
AB -3S
20.0
80.0
AB -41D
78.0
157.3
AB -4S
76.0
80.0
AB-4SL
88.0
85.0
AB-5BR
300.0
157.3
AB -51D
420.0
157.3
AB -5S
14.0
15.0
AB-6BR
51.0
157.3
AB -61D
170.0
157.3
AB -6S
210.0
185.9
AB -7D
110.0
157.3
AB -81D
100.0
157.3
AB -8S
87.0
85.0
AB-9BR
95.0
157.3
AB -91D
190.0
157.3
AB -9S
26.0
14.9
AL -1 D
660.0
157.3
AL -1S
280.0
268.7
AL-2BR
180.0
157.3
AL -21D
180.0
157.1
AL -2S
960.0
180.0
AL -31D
150.0
157.3
AL -3S
78.0
643.3
AL -41D
280.0
157.3
GWA-1 BR
36.0
157.3
GWA-1 D
140.0
157.3
GWA-1 S
87.0
157.3
GWA-21D
140.0
157.3
GWA-2S
100.0
157.3
GWA-61D
71.0
157.3
GWA-7D
230.0
157.3
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Barium
(cont.)
GWA-7S
290.0
150.5
MW -11 D
64.0
157.3
MW-14BR
23.0
157.3
Beryllium
Ash Basin Constant
Concentration Range
= 0.5 - 24 pg/L
Ash Storage Area
Concentration Range
= 1 - 10 pg/L
PV Structural
Fill Concentration
= 5 pg/L
Sorption
Coefficient [Kd] = 1
mL/g
AB -10D
0.1
1.0
AB -10S
0.7
1.0
AB-10SL
0.4
0.5
AB -11 D
0.2
1.0
AB -11 S
0.7
0.5
AB -12D
0.2
1.0
AB -12S
0.1
0.5
AB-12SL
0.1
0.5
AB -13D
0.2
0.7
AB -13S
0.4
0.5
AB -14D
0.2
1.0
AB -14S
0.6
0.5
AB-15BR
0.2
1.0
AB -15D
0.2
1.0
AB -15S
0.2
0.2
AB-15SL
0.2
0.5
AB -16D
0.2
1.0
AB -17D
0.2
1.0
AB -17S
0.2
0.5
AB -18D
0.2
1.0
AB -18s
0.2
0.5
AB -1 BR
0.2
1.0
AB -1 D
0.2
1.0
AB -1S
1.3
0.7
AB -20D
0.2
1.0
AB -20S
5.4
5.0
AB -21 D
0.2
1.0
AB -21 S
0.2
0.5
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Beryllium
(cont.)
AB -21D
0.2
0.7
AB -2S
0.2
0.2
AB -31D
0.2
1.0
AB -3S
2.0
1.0
AB -41D
0.1
4.8
AB -4S
0.2
1.0
AB-4SL
0.2
0.5
AB-5BR
0.2
1.0
AB -51D
0.1
5.2
AB -5S
23.5
24.0
AB-6BR
0.2
1.0
AB -61D
0.3
1.0
AB -6S
0.2
0.4
AB -71D
0.2
1.0
AB -81D
0.1
1.0
AB -8S
0.1
0.5
AB-9BR
0.2
1.0
AB -91D
0.2
1.0
AB -9S
0.2
AL -11D
0.2
1.0
AL -1S
9.9
9.5
AL-2BR
0.2
1.0
AL -21D
0.2
0.9
AL -2S
1.0
1.0
AL -31D
0.2
1.0
AL -3S
1.2
0.7
AL -41D
0.2
0.8
GWA-1 BR
0.2
1.0
GWA-1 D
0.2
1.0
GWA-1S
0.5
1.0
GWA-21D
0.2
0.7
GWA-2S
0.2
0.9
GWA-61D
0.2
1.0
GWA-71D
0.2
0.9
GWA-7S
0.2
0.4
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Beryllium
(cont.)
MW -11 D
0.1
0.8
MW-14BR
0.2
1.0
Boron
Ash Basin Constant
Concentration Range
= 50 - 66,600 pg/L
Ash Storage Area
Concentration Range
= 100 - 90,00 pg/L
PV Structural
Fill Concentration =
41,700 pg/L
Sorption
Coefficient [Kd] = 0.1
mL/g
AB -10D
1200.0
330.7
AB -10S
20600.0
20600.0
AB-10SL
9400.0
9400.0
AB -11 D
26.0
97.2
AB -11 S
50.0
50.0
AB -12D
3500.0
125.3
AB -12S
66600.0
66600.0
AB-12SL
3300.0
3300.0
AB -13D
50.0
3467.6
AB -13S
1200.0
2150.0
AB -14D
130.0
1336.0
AB -14S
10500.0
10500.0
AB-15BR
50.0
385.8
AB -15D
53.0
363.7
AB -15S
3100.0
1697.8
AB-15SL
930.0
1966.4
AB -16D
50.0
113.3
AB -16s
44.0
189.0
AB -17D
50.0
356.1
AB -17S
6000.0
6000.0
AB -18D
50.0
110.7
AB -18s
2100.0
2100.0
AB -1 BR
120.0
887.1
AB -1 D
380.0
904.5
AB -1S
5200.0
3459.6
AB -20D
50.0
125.4
AB -20S
41700.0
41700.0
AB -21 D
50.0
108.3
AB -21 S
1300.0
1300.0
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Boron
(cont.)
AB -21D
370.0
379.2
AB -2S
37.0
152.6
AB -31D
170.0
148.1
AB -3S
250.0
300.0
AB -41D
380.0
523.2
AB -4S
150.0
300.0
AB-4SL
850.0
500.0
AB-5BR
50.0
119.8
AB -51D
34.0
597.2
AB -5S
1500.0
1200.0
AB-6BR
93.0
413.1
AB -61D
5500.0
415.6
AB -6S
6200.0
5765.9
AB -71D
50.0
96.0
AB -81D
50.0
134.7
AB -8S
790.0
790.0
AB-9BR
50.0
119.9
AB -91D
50.0
122.7
AB -9S
50.0
30.2
AL -11D
1300.0
1038.5
AL -1S
4600.0
4673.9
AL-2BR
2100.0
327.5
AL -21D
6500.0
7134.1
AL -2S
6500.0
6500.0
AL -31D
4000.0
307.2
AL -3S
73400.0
44556.8
AL -41D
15200.0
705.7
GWA-1 BR
50.0
105.8
GWA-1 D
50.0
106.1
GWA-1S
50.0
106.5
GWA-21D
50.0
25.1
GWA-2S
50.0
45.0
GWA-31D
50.0
32.2
GWA-3S
50.0
18.4
GWA-41D
50.0
11.1
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Boron
(cont.)
GWA-4S
50.0
GWA-51D
50.0
11.2
GWA-5S
50.0
GWA-61D
50.0
99.6
GWA-6S
50.0
10.2
GWA-7D
45.0
68.1
GWA-7S
34.0
24.0
MW -10D
50.0
567.5
MW -10S
50.0
735.5
MW -11 D
50.0
35.1
MW -11 D
50.0
35.1
MW -12D
50.0
54.9
MW -12S
50.0
17.7
MW -13D
50.0
52.0
MW -13S
50.0
22.6
MW-14BR
29.0
240.7
MW -14D
2600.0
2178.9
MW -14S
2700.0
1848.0
MW -4D
50.0
MW -7S
5300.0
4701.9
Chloride
Ash Basin Constant Concentration Range = 1100 - 3,650,000 pg/L
Ash Storage Area Concentration Range = 1400 - 260,000 pg/L
PV Structural Fill Concentration = 51,500 pg/L
Sorption Coefficient [Kd] = 0 mL/g
AB -10D
5100.0
4517.4
AB -10S
7400.0
7400.0
AB-10SL
7600.0
7600.0
AB -11 D
4200.0
725.8
AB -11S
1800.0
1800.0
AB -12D
464000.0
6000.8
AB -12S
3650000.0
3650000.0
AB-12SL
27800.0
27800.0
AB -13D
3400.0
6145.9
AB -13S
1100.0
1100.0
AB -14D
1800.0
9198.8
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Chloride
(cont.)
AB -14S
8000.0
8000.0
AB-15BR
4200.0
5643.0
AB -15D
3400.0
5477.6
AB -15S
8100.0
6712.7
AB-15SL
4200.0
7621.7
AB -16D
5200.0
360.7
AB -16s
2900.0
728.8
AB -17D
2400.0
800.3
AB -17S
9700.0
9700.0
AB -18D
3300.0
1263.9
AB -18s
8900.0
8500.0
A13-1 BR
28700.0
48054.8
AB -1 D
201000.0
46701.1
A13 -1S
223000.0
30580.5
AB -20D
1900.0
15735.5
AB -20S
51500.0
51500.0
AB -21 D
4800.0
4716.6
AB -21 S
84600.0
84600.0
AB -21D
4500.0
19866.7
A13 -2S
7800.0
7432.3
AB -31D
4500.0
25501.9
A13 -3S
4100.0
5600.0
AB -41D
8200.0
20820.9
AB -4S
7100.0
5600.0
AB-4SL
9600.0
9600.0
AB-5BR
5100.0
12067.5
AB -51D
4400.0
24153.6
A13 -5S
47400.0
47400.0
AB-6BR
12100.0
335.6
A13 -61D
4300.0
337.3
AB -6S
2900.0
2696.9
AB -7D
7300.0
593.8
AB -81D
3100.0
679.8
A13 -8S
2800.0
2800.0
AB-9BR
4300.0
1833.8
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Chloride
(cont.)
A13 -91D
3000.0
1896.8
A13 -9S
2400.0
1466.5
AL -11D
222000.0
169714.6
AL -1S
260000.0
250614.1
AL -2 B R
2500.0
918.8
AL -21D
3500.0
2487.3
AL -2S
1400.0
3500.0
AL -31D
2300.0
600.6
AL -3S
17300.0
951.2
AL -41D
1900.0
88.3
GWA-1 BR
3500.0
10157.7
GWA-1 D
4500.0
10349.5
GWA-1 S
3000.0
10576.6
GWA-21D
9100.0
40.4
GWA-2S
940.0
37.5
GWA-31D
3600.0
24.1
GWA-3S
2200.0
18.9
GWA-41D
5200.0
GWA-4S
3700.0
GWA-51D
1900.0
GWA-5S
6600.0
GWA-61D
7000.0
32.6
GWA-6S
3100.0
1.6
GWA-7D
3200.0
86.8
GWA-7S
3600.0
41.4
MW -10D
1300.0
70554.0
MW -10S
840.0
69132.6
MW -11 D
2000.0
12.7
MW -11 D
2000.0
11.7
MW -12D
800.0
73.4
MW -12S
1000.0
25.6
MW -13D
4300.0
36.2
MW -13S
3800.0
34.5
MW-14BR
10800.0
75821.8
MW -14D
33700.0
100061.8
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Chloride
(cont.)
MW -14S
82700.0
68950.7
MW -4
1900.0
MW -4D
1200.0
MW -7S
239000.0
17527.4
Chromium
Ash Basin Constant
Concentration Range
= 0.5 - 54 pg/L
Ash Storage Area
Concentration Range
= 3 - 30 pg/L
PV Structural
Fill Concentration
= 72 pg/L
Sorption
Coefficient [Kd] = 1
mL/g
AB -10D
2.5
11.2
AB -10S
7.8
8.0
AB-10SL
3.8
1.0
AB -11 D
1.8
11.3
AB -11 S
4.4
4.0
AB -12D
1.7
11.3
AB -12S
0.4
0.5
AB-12SL
1.0
1.0
AB -13D
6.8
7.1
AB -13S
4.0
2.0
AB -14D
3.4
11.1
AB -14S
7.2
7.0
AB-15BR
1.3
11.0
AB -15D
2.6
11.0
AB -15S
1.1
1.4
AB-15SL
0.8
2.8
AB -16D
1.5
11.1
AB -17D
7.8
11.2
AB -17S
0.8
1.0
AB -18D
1.4
11.3
AB -18s
4.2
4.0
AB -1 BR
0.5
11.2
AB -1 D
1.1
11.2
AB -1S
1.0
3.8
AB -20D
2.0
11.3
AB -20S
71.6
72.0
AB -21 D
1.2
11.1
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Chromium
(cont.)
AB -21 S
0.5
0.5
A13 -21D
1.3
4.5
AB -2S
1.2
1.2
AB -31D
1.6
11.3
AB -3S
0.9
1.0
A13 -41D
0.7
17.7
AB -4S
0.7
1.0
AB-4SL
1.0
4.0
AB-5BR
2.0
11.3
A13 -51D
3.4
19.0
AB -5S
53.9
54.0
AB-6BR
7.4
11.1
AB -61D
1.2
11.1
A13 -6S
0.8
0.4
AB -7D
4.8
11.3
AB -81D
5.9
11.3
AB -8S
0.7
1.0
AB-9BR
4.4
11.2
AB -91D
6.3
11.2
A13 -9S
4.2
2.1
AL -1 D
5.0
11.2
AL -1S
30.9
28.6
AL-2BR
17.5
11.3
AL -21D
2.5
9.3
AL -2S
15.5
3.0
AL -31D
1.9
11.3
AL -3S
8.9
10.2
AL -41D
2.3
9.2
GWA-1 BR
3.6
11.3
GWA-1 D
4.0
11.3
GWA-1 S
1.8
11.3
GWA-21D
182.0
8.1
GWA-2S
2.3
10.6
GWA-31D
17.9
11.3
GWA-7D
6.7
10.6
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Chromium
(cont.)
GWA-7S
22.1
4.2
MW -11 D
7.6
9.4
MW-14BR
4.3
11.3
Hexavalent
Chromium
Ash Basin Constant
Concentration Range
= 0.02 - 0.08 pg/L
Ash Storage Area
Concentration Range
= 0.02 - 0.35 pg/L
PV Structural
Fill Concentration
= 0.5 pg/L
Sorption
Coefficient [Kd] = 1.0
mUg
AB -12D
0.031
2.80
AB -12S
0.02
1
AB-12SL
0.02
0.02
AB-15BR
0.02
2.71
AB -15D
0.02
2.72
AB-15SL
0.02
0.16
AB -1 BR
0.02
2.78
AB -1 D
0.02
2.78
AB -1S
0.02
0.69
AB -41D
0.02
2.11
AB -4S
0.082
0.09
AB-4SL
0.02
0.02
MW -10D
0.42
2.78
MW -10S
0.14
2.43
MW -11 D
4
2.33
MW -11 D
4.6
2.33
MW -12D
0.25
2.64
MW -12S
0.5
1.58
MW -13S
0.79
1.84
MW -14D
0.11
2.11
MW -14S
0.32
1.36
MW -4
1
MW -4D
0.32
Cobalt
Ash Basin Constant Concentration Range = 0.5 - 134 pg/L
Ash Storage Area Concentration Range = 4 - 16 pg/L
PV Structural Fill Concentration = 425 pg/L
Sorption Coefficient [Kd] = 1 mL/g
AB -10D
6.6
2.5
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Cobalt
(cont.)
AB -10S
4.1
4.0
AB-10SL
3.6
4.0
AB -11 D
0.3
2.5
AB -11 S
4.4
4.0
AB -12D
0.4
2.5
AB -12S
0.3
0.5
AB-12SL
0.4
0.5
AB -13D
2.4
1.7
AB -13S
4.8
2.0
AB -14D
0.6
2.5
AB -14S
1.0
1.0
AB-15BR
0.5
2.5
AB -15D
0.6
2.5
AB -15S
2.7
1.4
AB-15SL
6.1
1.7
AB -16D
4.7
2.5
AB -16s
22.6
1.4
AB -17D
2.5
2.5
AB -17S
1.0
1.0
AB -18D
1.0
2.5
AB -18s
0.2
0.5
AB -1 BR
0.5
2.5
AB -1 D
4.3
2.5
AB -1S
27.1
1.1
AB -20D
0.5
2.5
AB -20S
423.0
425.0
AB -21 D
6.4
2.5
AB -21 S
4.1
4.0
AB -21D
0.9
1.2
AB -2S
3.1
0.4
AB -31D
0.5
2.6
AB -3S
13.5
5.0
AB -41D
0.4
24.2
A134S
0.5
5.0
AB-4SL
0.3
0.5
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Cobalt
(cont.)
A13 -513R
7.9
2.6
A13 -51D
9.4
26.4
AB -5S
134.0
134.0
AB-6BR
0.5
2.5
AB -61D
2.2
2.5
A13 -6S
0.2
0.4
AB -7D
0.7
2.5
AB -81D
1.4
2.5
AB -8S
45.5
45.0
AB-9BR
0.5
2.5
AB -91D
28.1
2.5
AB -9S
2.2
0.8
AL -11D
1.3
2.5
AL -1S
11.8
11.4
AL-2BR
0.2
2.5
AL -21D
15.8
2.5
AL -2S
4.4
4.0
AL -31D
1.3
2.5
AL -3S
4.1
2.7
AL -41D
7.4
2.0
GWA-1 BR
1.7
2.5
GWA-1 D
0.2
2.5
GWA-1 S
5.5
2.5
GWA-21D
0.2
1.8
GWA-2S
2.6
2.3
GWA-31D
0.5
2.1
GWA-3S
0.6
1.4
GWA-41D
0.7
0.2
GWA-4S
6.9
GWA-51D
0.2
0.0
GWA-5S
2.4
GWA-61D
1.0
2.5
GWA-6S
0.8
1.0
GWA-7D
1.0
2.3
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Cobalt
(cont.)
GWA-7S
8.4
0.9
MW -10D
0.5
2.5
MW -10S
0.2
2.2
MW -11 D
0.6
2.1
MW -11 D
0.6
2.1
MW -12D
2.7
2.4
MW -12S
2.0
1.4
MW -13D
0.2
2.4
MW -13S
0.2
1.6
MW-14BR
0.2
2.5
MW -14D
2.4
2.2
MW -14S
8.2
1.4
MW -4
2.5
MW -4D
0.5
MW -7S
57.6
0.8
Selenium
Ash Basin Constant
Concentration Range
= 0.5 - 12 pg/L
Ash Storage Area
Concentration Range
= 10 - 110 pg/L
PV Structural
Fill Concentration
= 454 pg/L
Sorption
Coefficient [Kd] = 1
mL/g
AB -10D
0.5
9.9
AB -10S
1.8
2.0
AB-10SL
1.6
1.5
AB -11 D
0.5
10.0
AB -11S
2.5
2.5
AB -12D
0.5
10.0
AB -12S
2.2
2.0
AB-12SL
0.5
0.5
AB -13D
0.4
6.9
AB -13S
12.1
12.0
AB -14D
0.4
9.9
AB -14S
1.0
1.0
AB-15BR
0.5
9.8
AB -15D
0.5
9.8
AB -15S
0.5
0.2
AB-15SL
0.5
1.6
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Selenium
(cont.)
AB -16D
0.9
9.8
A13 -16s
0.2
5.0
AB -17D
0.4
9.9
AB -17S
0.5
0.5
AB -18D
0.4
10.0
A13 -18s
0.4
0.5
AB -1 BR
0.5
9.9
AB -1 D
0.5
9.9
AB -1S
6.1
3.3
AB -20D
0.5
10.0
AB -20S
454.0
454.0
AB -21 D
0.4
9.8
AB -21 S
0.2
0.5
A13 -21D
0.6
4.9
AB -2S
1.4
1.5
AB -31D
0.5
10.0
AB -3S
1.8
2.0
A13 -41D
0.5
8.1
AB -4S
3.3
2.0
AB-4SL
0.7
1.0
AB-5BR
0.5
10.0
A13 -51D
0.5
8.7
AB -5S
3.3
3.0
AB-6BR
2.7
9.8
AB -61D
0.5
9.8
A13 -6S
0.4
0.4
AB -7D
1.8
10.0
AB -81D
0.5
10.0
AB -8S
0.5
0.5
AB-9BR
0.5
9.9
AB -91D
0.8
9.9
AB -9S
0.4
AL -11D
0.5
9.8
AL -1S
1.0
9.6
AL -2 B R
24.0
10.0
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Selenium
(cont.)
AL -21D
13.6
9.7
AL -2S
108.0
13.0
AL -31D
16.7
10.0
AL -3S
28.5
74.0
AL -41D
9.0
8.2
GWA-1 BR
0.4
10.0
GWA-1 D
0.6
10.0
GWA-1S
0.8
10.0
GWA-21D
5.0
7.2
GWA-2S
0.3
9.3
GWA-31D
0.4
8.3
GWA-3S
0.5
5.4
GWA-41D
0.6
1.4
GWA-4S
0.5
GWA-51D
0.5
1.2
GWA-5S
0.7
GWA-61D
1.1
10.0
GWA-6S
0.5
3.8
GWA-7D
0.4
9.4
GWA-7S
0.4
3.7
MW -10D
0.3
9.9
MW -10S
0.5
8.7
MW -11 D
0.2
8.3
MW -11 D
0.2
8.3
MW -12D
0.3
9.4
MW -12S
0.5
5.6
MW -13D
0.5
9.7
MW -13S
0.5
6.6
MW-14BR
1.3
10.0
MW -14D
3.2
7.8
MW -14S
5.0
5.0
MW -4
2.5
MW -4D
0.5
MW -7S
15.0
3.3
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
la /L
Predicted
Concentration
N /L
Sulfate
Ash Basin Constant
Concentration Range = 1,200
— 8,000,000 pg/L
Ash Storage Area Concentration
Range = 60,000
— 3,300,000 pg/L
PV Structural
Fill Concentration =
560,000 pg/L
Sorption
Coefficient [Kd] = 0
mL/g
AB -10D
11000
142366
AB -10S
857000
857000
AB-10SL
670000
520000
AB -11D
7600
53173
AB -11 S
1200
1200
AB -12D
219000
37681
AB -12S
923000
923000
AB-12SL
19600
19600
AB -13D
26800
56573
AB -13S
36100
36100
AB -14D
22800
109185
AB -14S
1180000
120000
AB-15BR
61900
24425
AB -15D
28400
23974
AB -15S
114000
90031
AB-15SL
33600
82892
AB -16D
61900
4262
AB -16s
4300
9537
AB -17D
13600
11374
AB -17S
183000
183000
AB -18D
6000
1640
AB -18s
9100
9100
AB -1 BR
37600
94414
AB -1 D
32000
94929
AB -1S
142000
62759
AB -20D
16300
175122
AB -20S
3560000
560000
AB -21D
8300
14534
AB -21 S
353000
260000
AB -21D
178000
176934
AB -2S
19600
67770
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Sulfate
(cont.)
AB -3D
90000
113136
A13 -3S
366000
366000
AB -41D
33300
21266
AB -4S
34500
42500
AB-4SL
42500
42500
AB-5BR
86400
53190
AB -51D
18800
110416
AB -5S
8850000
8000000
AB-6BR
98600
71950
A13 -61D
36800
72264
AB -6S
646000
600780
AB -7D
43700
7406
AB -81D
124000
30543
A13 -8S
368000
368000
AB-9BR
47500
3185
AB -91D
12900
3212
AB -9S
4600
2811
AL -11D
17100
45425
AL -1S
62200
62245
AL-2BR
176000
171473
AL -2D
386000
506484
AL -2S
979000
979000
AL -31D
402000
349713
AL -3S
3160000
2032904
AL -41D
308000
13986
GWA-1 BR
43800
96606
GWA-1 D
189000
98448
GWA-1 S
4000
100610
GWA-21D
70700
273
GWA-2S
22400
164
GWA-31D
11800
242
GWA-3S
1600
196
GWA-41D
24200
GWA-4S
1000
GWA-51D
4000
8
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Sulfate
(cont.)
GWA-5S
6200
GWA-61D
57100
11
GWA-6S
540
1
GWA-71D
9200
50
GWA-7S
11300
28
MW -10D
3500
59275
MW -10S
1000
35063
MW -11 D
1200
5
MW -11 D
1200
5
MW -12D
4000
25
MW -12S
650
9
MW -13D
760
235
MW -13S
1000
300
MW-14BR
12900
72118
MW -14D
207000
95818
MW -14S
223000
66107
MW -4
1000
MW -4D
1000
MW -7S
153000
91950
Thallium
Ash Basin Constant Concentration Range = 0.025 — 1.4 pg/L
Ash Storage Area Concentration Range = 0.1 — 0.35 pg/L
PV Structural Fill Concentration = 15 pg/L
Sorption Coefficient [Kd] = 70 mL/g
AB -10D
0.1
0.5
AB -10S
0.3
0.3
AB-10SL
0.3
0.3
AB -11D
0.1
0.5
AB -11S
0.1
0.5
AB -12D
0.1
0.5
AB -12S
0.1
0.1
AB-12SL
0.1
0.1
AB -13D
0.0
0.5
AB -13S
1.0
1.0
AB -14D
0.1
0.5
AB -14S
0.2
0.3
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Thallium
(cont.)
AB-15BR
0.1
0.5
AB -15D
0.1
0.5
AB -15S
0.1
AB-15SL
0.0
0.3
AB -16D
0.0
0.5
A13 -16s
0.0
0.5
AB -17D
0.0
0.5
AB -17S
0.1
0.1
AB -18D
0.0
0.5
A13 -18s
0.1
0.1
AB -1 BR
0.1
0.5
AB -1 D
0.1
0.5
AB -1S
0.3
0.5
AB -20D
0.1
0.5
AB -20S
14.8
15.0
AB -21 D
0.1
0.5
AB -21 S
0.1
0.1
A13 -21D
0.0
0.5
AB -2S
0.1
0.2
AB -3D
0.0
0.5
AB -3S
2.0
1.4
A13 -41D
0.1
0.5
AB -4S
0.8
1.4
AB-4SL
0.1
0.1
AB-5BR
0.1
0.5
A13 -51D
0.0
0.5
AB -5S
0.5
0.5
AB-6BR
0.1
0.5
AB -61D
0.0
0.5
A13 -6S
0.0
0.0
AB -7D
0.0
0.5
AB -81D
0.0
0.5
AB -8S
0.7
1.0
AB-9BR
0.0
0.5
AB -91D
0.0
0.5
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Thallium
(cont.)
AB -9S
0.0
AL -11D
0.1
0.5
AL -1S
0.3
0.5
AL-2BR
0.0
0.5
AL -21D
0.1
0.1
AL -2S
0.1
0.5
AL -31D
0.0
0.5
AL -3S
1.8
0.1
AL -41D
0.1
0.5
GWA-1 BR
0.1
0.5
GWA-1 D
0.0
0.5
GWA-1S
0.0
0.5
GWA-21D
0.0
0.5
GWA-2S
0.1
0.5
GWA-31D
0.1
0.5
GWA-3S
0.1
0.5
GWA-41D
0.0
0.2
GWA-4S
0.1
GWA-5D
0.1
GWA-5S
0.1
GWA-61D
0.0
0.5
GWA-6S
0.1
0.5
GWA-7D
0.1
0.5
GWA-7S
0.1
0.5
MW -10D
0.1
0.5
MW -10S
0.1
0.5
MW -11 D
0.1
0.5
MW -11 D
0.1
0.5
MW -12D
0.0
0.5
MW -12S
0.0
0.5
MW -13D
0.1
0.5
MW -13S
0.1
0.5
MW-14BR
0.1
0.5
MW -14D
0.1
0.5
MW -14S
0.1
0.5
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(pg/L
Predicted
Concentration
N /L
Thallium
(cont.)
MW -4
0.5
MW -41D
0.1
MW -7S
0.4
0.5
Vanadium
Ash Basin Constant
Concentration Range
= 0.2 - 85 pg/L
Ash Storage Area
Concentration Range
= 1 - 8.5 pg/L
PV Structural
Fill Concentration
= 160 pg/L
Sorption
Coefficient [Kd] = 25
mL/g
AB -10D
9.2
3.9
AB -10S
19.4
19.0
AB-10SL
12.7
13.0
AB -11 D
2.3
3.9
AB -11 S
20.8
21.0
AB -12D
2.5
3.9
AB -12S
1.1
1.0
AB-12SL
2.6
2.5
AB -13D
1.1
4.9
AB -13S
24.1
24.0
AB -14D
3.3
3.9
AB -14S
17.9
18.0
AB-15BR
1.0
3.9
AB -15D
1.4
3.9
AB -15S
1.4
0.6
AB-15SL
1.6
2.8
AB -16D
0.6
3.9
AB -16s
1.0
3.8
AB -17D
7.1
3.9
AB -17S
2.2
2.0
AB -18D
4.2
3.9
AB -18s
1.1
1.0
AB -1 BR
0.4
3.9
AB -1 D
1.1
3.9
AB -1S
1.0
3.6
AB -20D
1.1
3.9
AB -20S
157.0
160.0
AB -21 D
0.7
3.9
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
(jig/L)N
Predicted
Concentration
/L
Vanadium
(cont.)
AB -21 S
0.3
0.2
A13 -21D
1.8
3.9
AB -2S
1.8
1.5
AB -31D
2.3
3.9
AB -3S
0.8
1.0
A13 -41D
0.5
3.9
AB -4S
1.1
1.0
AB-4SL
10.9
11.0
AB-5BR
0.8
3.9
A13 -51D
3.4
3.9
AB -5S
83.0
85.0
AB-6BR
7.4
3.9
AB -61D
0.9
3.9
A13 -6S
1.9
1.8
AB -7D
57.5
3.9
AB -81D
5.1
3.9
AB -8S
1.5
1.5
AB-9BR
2.4
3.9
AB -91D
2.5
3.9
A13 -9S
1.0
0.2
AL -11D
1.9
3.9
AL -1S
8.5
7.7
AL-2BR
4.5
3.9
AL -21D
0.8
3.9
AL -2S
6.5
1.0
AL -31D
0.7
3.9
AL -3S
163.0
4.4
AL -41D
2.4
3.9
GWA-1 BR
3.5
3.9
GWA-1 D
9.3
3.9
GWA-1 S
1.7
3.9
GWA-21D
12.2
3.9
GWA-2S
0.3
3.9
GWA-31D
24.6
3.9
GWA-3S
0.6
3.8
GWA-41D
8.6
2.1
Continued on next page

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 6 Transport Model Calibration Results (continued)
COI
Monitoring Well
Measured
Concentration
p /L
Predicted
Concentration
N /L
Vanadium
(cont.)
GWA-4S
19.5
GWA-51D 1.8
1.4
GWA-5S 9.2
GWA-61D 12.8
3.9
GWA-6S 0.9
3.7
GWA-7D 6.1
3.9
GWA-7S 23.7
3.6
MW -10D 3.2
3.9
MW -10S 0.3
3.9
MW -11 D 23.8
3.9
MW -11 D 23.8
3.9
MW -12D 4.6
3.9
MW -12S 0.5
3.8
MW -13D 5.9
3.9
MW -13S 4.8
3.9
MW-14BR 4.3
3.9
MW -14D 1.3
3.9
MW -14S 0.4
3.7
MW -4 2.2
MW -4D 2.8
MW -7S 4.6
3.8
Notes:
1. mL/g - milliliters per gram
2. pg/L - micrograms per liter

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Table 7 Predicted Advective Travel Time to Boundary
Groundwater
Zone
Monitoring Well
Advective Travel Time
to Boundary (days)
Shallow
MW -14
552
AB -1S
589
AB -16S
2,567
GWA-22S
9,026
AL -2S
10,813
Deep
AB -2D
439
GWA7S
639
AB -17D
1,077
AB -13D
1,773
AB -5D
7,484
AB -21 D
14,926
Bedrock
AB -1 BR
33
MW14-BR
91
AB -11 D
696
AB6-BR
1,061
AB3-BR
3,998
AB12-BR
4,813
AB -20D
6,343
Note:
Computed travel time over 3-D flow path using flow and transport terms from the
groundwater flow and transport model.

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
FIGURES
Figure 1 Conceptual Groundwater Flow Model/Model Domain
Figure 2 Model Domain North-South Cross section A -A' through Inactive and Active Ash Basins
Figure 3 Model Domain East-West Cross section B -B' through the Active Ash Basin
Figure 4 Flow Model Boundary Conditions
Figure 5 Model Layers 2-4 Recharge Areas and Contaminant Source Zones (Constant
Concentration Cells)
Figure 6 Model Layers 5-7 Contaminant Source Zones (Constant Concentration Cells)
Figure 7 Observation Wells in Shallow Groundwater Flow Layer
Figure 8 Observation Wells in Deep Groundwater Zone
Figure 9 Observation Wells in Bedrock Groundwater Zone
Figure 10 Hydraulic Conductivity Zonation in S Model Layers (Model Layers 2-4)
Figure 11 Hydraulic Conductivity Zonation in M1/M2 Model Layers (Model Layers 5-7)
Figure 12 Modeled Hydraulic Head vs. Observed Hydraulic Head
Figure 13 Hydraulic Potentiometric Head in Shallow Groundwater Zone (Model Layer 6)
Figure 14 Forward Particle Tracking Results
Figure 15 One -Year Reverse Particle Tracking from Residential Wells
Figure 16 Predicted Antimony in Monitoring Well AB -1 S
Figure 17 Predicted Antimony in Monitoring Well AB -2S
Figure 18 Predicted Antimony in Monitoring Well GWA-1 S
Figure 19 Predicted Antimony in Monitoring Well MW -6S
Figure 20 Initial (2015) Antimony Concentrations in Shallow Groundwater Zone
Figure 21 Initial (2015) Antimony Concentrations in Deep Groundwater Zone
Figure 22 Initial (2015) Antimony Concentrations in Bedrock Groundwater Zone
Figure 23 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Shallow
Groundwater Zone
Figure 24 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Deep
Groundwater Zone
Figure 25 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Bedrock
Groundwater Zone
Figure 26 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Shallow
Groundwater Zone
Figure 27 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Deep
Groundwater Zone
Figure 28 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Bedrock
Groundwater
Figure 29 Predicted Arsenic in Monitoring Well AB -1 S
Figure 30 Predicted Arsenic in Monitoring Well AB -2S
Figure 31 Predicted Arsenic in Monitoring Well GWA-1 S
Figure 32 Predicted Arsenic in Monitoring Well MW -6S
Figure 33 Initial (2015) Arsenic Concentrations in Shallow Groundwater Zone
Figure 34 Initial (2015) Arsenic Concentrations in Deep Groundwater Zone
Figure 35 Initial (2015) Arsenic Concentrations in Bedrock Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 36 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Shallow
Groundwater Zone
Figure 37 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Deep
Groundwater Zone
Figure 38 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Bedrock
Groundwater Zone
Figure 39 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Shallow
Groundwater Zone
Figure 40 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Deep
Groundwater Zone
Figure 41 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Bedrock
Groundwater Zone
Figure 42 Predicted Barium in Monitoring Well AB -1S
Figure 43 Predicted Barium in Monitoring Well AB -2S
Figure 44 Predicted Barium in Monitoring Well GWA-1 S
Figure 45 Predicted Barium in Monitoring Well MW -6S
Figure 46 Initial (2015) Barium Concentrations in Shallow Groundwater Zone
Figure 47 Initial (2015) Barium Concentrations in Deep Groundwater Zone
Figure 48 Initial (2015) Barium Concentrations in Bedrock Groundwater Zone
Figure 49 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Shallow
Groundwater Zone
Figure 50 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Deep
Groundwater Zone
Figure 51 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Bedrock
Groundwater Zone
Figure 52 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Shallow
Groundwater Zone
Figure 53 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Deep
Groundwater Zone
Figure 54 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Bedrock
Groundwater Zone
Figure 55 Predicted Beryllium in Monitoring Well AB -1S
Figure 56 Predicted Beryllium in Monitoring Well AB -2S
Figure 57 Predicted Beryllium in Monitoring Well GWA-1 S
Figure 58 Predicted Beryllium in Monitoring Well MW -6S
Figure 59 Initial (2015) Beryllium Concentrations in Shallow Groundwater Zone
Figure 60 Initial (2015) Beryllium Concentrations in Deep Groundwater Zone
Figure 61 Initial (2015) Beryllium Concentrations in Bedrock Groundwater Zone
Figure 62 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Shallow
Groundwater Zone
Figure 63 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Deep
Groundwater Zone
Figure 64 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Bedrock
Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 65 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Shallow
Groundwater Zone
Figure 66 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Deep
Groundwater Zone
Figure 67 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Bedrock
Groundwater Zone
Figure 68 Predicted Boron in Monitoring Well AB -IIS
Figure 69 Predicted Boron in Monitoring Well AB -2S
Figure 70 Predicted Boron in Monitoring Well GWA-1 S
Figure 71 Predicted Boron in Monitoring Well MW -6S
Figure 72 Initial (2015) Boron Concentrations in Shallow Groundwater Zone
Figure 73 Initial (2015) Boron Concentrations in Deep Groundwater Zone
Figure 74 Initial (2015) Boron Concentrations in Bedrock Groundwater Zone
Figure 75 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Shallow
Groundwater Zone
Figure 76 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Deep
Groundwater Zone
Figure 77 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Bedrock
Groundwater Zone
Figure 78 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Shallow
Groundwater Zone
Figure 79 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Deep
Groundwater Zone
Figure 80 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Bedrock
Groundwater Zone
Figure 81 Predicted Chloride in Monitoring Well AB -11S
Figure 82 Predicted Chloride in Monitoring Well AB -2S
Figure 83 Predicted Chloride in Monitoring Well GWA-1 S
Figure 84 Predicted Chloride in Monitoring Well MW -6S
Figure 85 Initial (2015) Chloride Concentrations in Shallow Groundwater Zone
Figure 86 Initial (2015) Chloride Concentrations in Deep Groundwater Zone
Figure 87 Initial (2015) Chloride Concentrations in Bedrock Groundwater Zone
Figure 88 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Shallow
Groundwater Zone
Figure 89 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Deep
Groundwater Zone
Figure 90 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Bedrock
Groundwater Zone
Figure 91 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Shallow
Groundwater Zone
Figure 92 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Deep
Groundwater Zone
Figure 93 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Bedrock
Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 94 Predicted Chromium in Monitoring Well AB -1S
Figure 95 Predicted Chromium in Monitoring Well AB -2S
Figure 96 Predicted Chromium in Monitoring Well GWA-1S
Figure 97 Predicted Chromium in Monitoring Well MW -6S
Figure 98 Initial (2015) Chromium Concentrations in Shallow Groundwater Zone
Figure 99 Initial (2015) Chromium Concentrations in Deep Groundwater Zone
Figure 100 Initial (2015) Chromium Concentrations in Bedrock Groundwater Zone
Figure 101 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in
Shallow Groundwater Zone
Figure 102 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in Deep
Groundwater Zone
Figure 103 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in
Bedrock Groundwater Zone
Figure 104 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Shallow
Groundwater Zone
Figure 105 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Deep
Groundwater Zone
Figure 106 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Bedrock
Groundwater Zone
Figure 107 Predicted Cobalt in Monitoring Well AB -1 S
Figure 108 Predicted Cobalt in Monitoring Well AB -2S
Figure 109 Predicted Cobalt in Monitoring Well GWA-1S
Figure 110 Predicted Cobalt in Monitoring Well MW -6S
Figure 111 Initial (2015) Cobalt Concentrations in Shallow Groundwater Zone
Figure 112 Initial (2015) Cobalt Concentrations in Deep Groundwater Zone
Figure 113 Initial (2015) Cobalt Concentrations in Bedrock Groundwater Zone
Figure 114 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Shallow
Groundwater Zone
Figure 115 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Deep
Groundwater Zone
Figure 116 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Bedrock
Groundwater Zone
Figure 117 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Shallow
Groundwater Zone
Figure 118 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Deep
Groundwater Zone
Figure 119 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Bedrock
Groundwater Zone
Figure 120 Predicted Hexavalent Chromium in Monitoring Well AB -1 S
Figure 121 Predicted Hexavalent Chromium in Monitoring Well AB -2S
Figure 122 Predicted Hexavalent Chromium in Monitoring Well GWA-1 S
Figure 123 Predicted Hexavalent Chromium in Monitoring Well MW -6S3
Figure 124 Initial (2015) Hexavalent Chromium Concentrations in Shallow Groundwater Zone
Figure 125 Initial (2015) Hexavalent Chromium Concentrations in Deep Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 126 Initial (2015) Hexavalent Chromium Concentrations in Bedrock Groundwater Zone
Figure 127 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium Concentrations
in Shallow Groundwater Zone
Figure 128 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium
Concentrations in Deep Groundwater Zone
Figure 129 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium Concentrations
in Bedrock Groundwater Zone
Figure 130 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in
Shallow Groundwater Zone
Figure 131 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in
Deep Groundwater Zone
Figure 132 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in
Bedrock Groundwater Zone
Figure 133 Predicted Selenium in Monitoring Well AB -11S
Figure 134 Predicted Selenium in Monitoring Well AB -2S
Figure 135 Predicted Selenium in Monitoring Well GWA-1 S
Figure 136 Predicted Selenium in Monitoring Well MW -6S
Figure 137 Initial (2015) Selenium Concentrations in Shallow Groundwater Zone
Figure 138 Initial (2015) Selenium Concentrations in Deep Groundwater Zone
Figure 139 Initial (2015) Selenium Concentrations in Bedrock Groundwater Zone
Figure 140 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in Shallow
Groundwater Zone
Figure 141 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in Deep
Groundwater Zone
Figure 142 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in
Bedrock Groundwater Zone
Figure 143 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Shallow
Groundwater Zone
Figure 144 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Deep
Groundwater Zone
Figure 145 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Bedrock
Groundwater Zone
Figure 146 Predicted Sulfate in Monitoring Well AB -1S
Figure 147 Predicted Sulfate in Monitoring Well AB -2S
Figure 148 Predicted Sulfate in Monitoring Well GWA-1 S
Figure 149 Predicted Sulfate in Monitoring Well MW -6S
Figure 150 Initial (2015) Sulfate Concentrations in Shallow Groundwater Zone
Figure 151 Initial (2015) Sulfate Concentrations in Deep Groundwater Zone
Figure 152 Initial (2015) Sulfate Concentrations in Bedrock Groundwater Zone
Figure 153 Existing Conditions Scenario 1 - 2115 Predicted Sulfate Concentrations in Shallow
Groundwater Zone
Figure 154 Existing Condition Scenario 1 - 2115 Predicted Sulfate Concentrations in Deep
Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 155 Existing Conditions Scenario 1 - 2115 Predicted Sulfate Concentrations in Bedrock
Groundwater Zone
Figure 156 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Shallow
Groundwater Zone
Figure 157 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Deep
Groundwater Zone
Figure 158 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Bedrock
Groundwater Zone
Figure 159 Predicted Thallium in Monitoring Well AB -11S
Figure 160 Predicted Thallium in Monitoring Well AB -2S
Figure 161 Predicted Thallium in Monitoring Well GWA-1 S
Figure 162 Predicted Thallium in Monitoring Well MW -6S
Figure 163 Initial (2015) Thallium Concentrations in Shallow Groundwater Zone
Figure 164 Initial (2015) Thallium Concentrations in Deep Groundwater Zone
Figure 165 Initial (2015) Thallium Concentrations in Bedrock Groundwater Zone
Figure 166 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Shallow
Groundwater Zone
Figure 167 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Deep
Groundwater Zone
Figure 168 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Bedrock
Groundwater Zone
Figure 169 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Shallow
Groundwater Zone
Figure 170 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Deep
Groundwater Zone
Figure 171 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Bedrock
Groundwater Zone
Figure 172 Predicted Vanadium in Monitoring Well AB -11S
Figure 173 Predicted Vanadium in Monitoring Well AB -2S
Figure 174 Predicted Vanadium in Monitoring Well GWA-1 S
Figure 175 Predicted Vanadium in Monitoring Well MW -6S
Figure 176 Initial (2015) Vanadium Concentrations in Shallow Groundwater Zone
Figure 177 Initial (2015) Vanadium Concentrations in Deep Groundwater Zone
Figure 178 Initial (2015) Vanadium Concentrations in Bedrock Groundwater Zone
Figure 179 Existing Conditions Scenario 1 - 2115 Predicted Vanadium Concentrations in
Shallow Groundwater Zone
Figure 180 Existing Conditions Scenario 1 - 2115 Predicted Vanadium Concentrations in Deep
Groundwater Zone
Figure 181 Existing Conditionsc Scenario 1 - 2115 Predicted Vanadium Concentrations in
Bedrock Groundwater Zone
Figure 182 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Shallow
Groundwater Zone
Figure 183 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Deep
Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 184 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Bedrock
Groundwater Zone

l]IUUfIUWdICI
Discharge
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 1 Conceptual Groundwater Flow Model/Model Domain
ow
ndwater
charge

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
L.
A'
A9�
Qke
5
rz
BR
Figure 2 Model Domain North-South Cross section A -A' through Inactive and Active Ash Basins

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
B B'
L,.
Figure 3 Model Domain East-West Cross section B -B' through the Active Ash Basin
d
B B'
L,.
Figure 3 Model Domain East-West Cross section B -B' through the Active Ash Basin

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 4 Flow Model Boundary Conditions

IV' —7c y_ a
,,; f Recharge=O.Oinlyr
t
X. --eO. t
Recharge=4
Recharge=6.6inlyr
i/
Recharge=O.Oinlyr '
Legend
DUKE ENERGY PROPERTY
BOUNDARY
ASH BASIN 'PASTE
BOUNDARY
LANDFILLJASH STORAGE
AREA BOUNDARY
_ ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
.Oinlyr
e �
o _
a
i
'sN
A
750 1,500
Feet
WITH DUKE ENERGY source: LvfflW,1�1 -C''TvUI}� dl I
PROPERTY BOUNDARY K ,aGeograph is NESlAIrbU D USQA, USG „qE�X, E�p�JIf1Q,
Constant Concentration "" 'k''�'' MODEL DOMAIN Aerogrid, IGN, IGP: sMsstopo and the GIS User Comm unity
— t
Figure 5 Model Layers 2-4 Recharge Areas and Contaminant Source Zones (Constant
Concentration Cells)

U_ -j
Structural Fill
Industrial Landfill
toe
-
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
"OF"
i
y FGD Resic
# VLandfill
z
i
t
✓ t
—
b
d
�
Legend
`
ti
r
DUKE ENERGY PROPERTY
\t
BOUNDARY
ASH BASIN WASTE
BOUNDARY
hN
/• I5
LANDFILJASEH STORAGE
f'
AREA BOUNDARY
✓
' ♦ 0 750 1,500
ASH BASIN COMPLIANCE
BOUNDARY
ti
ASH BASIN COMPLIANCE
Feet
BOUNDARY COINCIDENT
WITH DUKE ENERGY
,
Source. ESrI, Elgltal GlO�]E, 2E'OEye. I-6D,e �p,1 h f
PROPERTY BOUNDARY
-
Constant Concentration
Geogra['hics CNESI,gIr• S. USDA USGS, AFX, Gettnap(ping
MODEL DOMAIN
�
Aerogrid, IGN; LE -P; s i Q,-ancf khe GIS user C©Inoiunity
Figure 6 Model Layers 5-7 Contaminant Source Zones (Constant Concentration Cells)

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 7 Observation Wells in Shallow Groundwater Flow Layer

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 8 Observation Wells in Deep Groundwater Zone

11
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
9BR
[
MW -1 4113R
•
AB-9BR
} AB -66R`
AB-5BR
•
•
Legend
DUKE ENERGY PROPERTY
i BOUNDARY
,
ASH BASIN V% ASTE
BOUNDARY
LANDFILL/ASH STORAGE
_
AREA BOUNDARY
fl
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
MODEL DOMAIN
Figure 9 Observation Wells
in Bedrock Groundwater Zone
N
A
750 1,500
Feet

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 10 Hydraulic Conductivity Zonation in S Model Layers (Model Layers 2-4)

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 11 Hydraulic Conductivity Zonation in M1/M2 Model Layers (Model Layers 5-7)

850
0
830
W
E 810
M
= 800
a�
t'a
_ 790
E
LA
780
770
760
750
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Modeled vs. Observed Head
Y = 0.8828x+94.234
r*
R'=0.9445
i*±" '
�+ r
* r
750 760 770 780 790 800 810 820
Observed Heads (ft msl)
Figure 12 Modeled Hydraulic Head vs. Observed Hydraulic Head
830 840 850

�a
Of
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
V
i
Legend
+.
DUKE ENERGY PROPERTY
BOUNDARY
t.
ASH BASIN WASTE
hN
BOUNDARY
LANDFILIJASH STORAGE
_
AREA BOUNDARY
_
-
0 750 1,500
ASH BASIN COMPLIANCE
G
BOUNDARY
ASH BASIN COMPLIANCE
Feet
BOUNDARY COINCIDENT
VdTH DUKE ENERGY
Soume' ESrl, QJ5011 t
PROPERTY BOUNDARY
G20gt"e phlGS. Clal f
' la- Bldpplh
MODEL DOMAIN
- A2fogrld, IGN.IIr', I
Unity
Figure 13 Hydraulic Potentiometric
Head in Shallow Groundwater Zone (Model Layer 6)

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 14 Forward Particle Tracking Results

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 15 One -Year Reverse Particle Tracking from Residential Wells

3.0
2.5
Z0
r-,
3 1,5
C
O
1.0
C
QJ
c3
C
D
U ©.5
0.0 � r
Ln It
rD 00
M M
r -I r -I
Notes:
1. µg/L=mirrogramsper liter
2. Anti morry IMAC value=1 µgf L
3. Antimony PPBC=2.5 µg/L
Predicted Antimony Concentration at AB -1S
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
—Existing Conditions
—Cap -in -Place
— -Antimony IMAC
O N r.0 C Q O N sip 0 O N sD 000 O
O O O CD CD rl "I rl "I rl N N N N N M
N N N N N N N N N N N N N N N N
Time (Years)
Figure 16 Predicted Antimony in Monitoring Well ABAS

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Antimony Concentration at A13 -2S
2.5
—Existing Conditions
Cap -in -Place
2.0 — -Antimony IMAC
1.5
to
c
1.0
m
c�
V 0.5
0.0 -
� € It a N �.D 00 o N coo 00 a N rID 00 0
rn M o o 0 o a r_4 r_� r_4 r_4 r_� N N rl rl rq m
Notes:
1. pg/L=microgramsperliter Time (Years)
2. Anti monyIMAC value=l. pg/L
S. Anti m ony PPBC = 2.5 pg/L
Figure 17 Predicted Antimony in Monitoring Well A13 -2S

3.0
pmm
2.0
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Antimony Concentration at GWA-1S
U 0.5
�S 00 00 00 Of]
Ol d3 O O O d O N N N N N CO
N N N N N N N N N N N N N N N N
Notes:
1. µg/L = micrograms per liter Time (Years)
2. Antimony IMAC value = 1 µg/L
3. Antimony PPBC = 2.5 ug/L
Figure 18 Predicted Antimony in Monitoring Well GWA-1S

2.5
O7
r-,
0 1.5
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Antimony Concentration at MW -6S
0.0
Ln .9t -t qt
;.0 00 c rl
Cf) 0) c c
rl r-4 rl rq
Notes:
1. [ig/L=micrograrrsper fiter
2. Antimony IMAC ua iue=1 µg/L
S. Anti monyPpBC=2.5 µg/L
� cc a N C.0 o 4 qt `ta o N s�0 cc a
CD o o r-� r-� r-� "I "I rl N N N N m
Time (Years)
Figure 19 Predicted Antimony in Monitoring Well MW -6S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 20 Initial (2015) Antimony Concentrations in Shallow Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L = micrograms per liter Ro
2. Antimony IMAC value = 1 pg/L L �'
3. Antimony PPBC = 2.5 Ng/L
v
E h
cci
O
_I
m
N LEGEND
m Dry Cell y –
N E 11
<= 0.5
O
L 0.5 - 1 (Standard)
LL 1 -2.5 (Background
�I Concentration)
0
2.5-5
or A
EI 5-50
50-250
m
L
E 250- 1,000
4, - j
161,000 - 5,000
0
a 5,000 - 7,306
DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
w ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
c — — BASIN COMPLIANCE
N
rn BOUNDARY
o LANDFILL/STRUCTURAL FILL _
r
N BOUNDARY 0
500 1.000
U
MODEL DOMAIN 1
Feet
Figure 21 Initial (2015) Antimony Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Antimony IMAC value = 1 pg/L
3. Antimony PPBC = 2.5 Ng/L a
E
(6
N
N
O
l9
LEGEND
Dry Cell
0.5N
O�
0.5 -1 (Standard)
1 -2.5 (Background
r Concentration)
0
2.5-5
o'
a 5-50
m
50-250 '
L
E 250-1,000
lT/
ISI 1,000 - 5,000
0
a 5,000 -7,306
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
ca
= MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
1
N
A
0 500 1.000
Feet
Figure 22 Initial (2015) Antimony Concentrations in Bedrock Groundwater Zone

Notes:
0.5 - 1 (Standard)
1. pg/Ljcrograms per liter
1 -2.5 (Background
2. AntiIMAC value = 1 pg/L
Concentration)
3. AntiPPBC = 2.5 pg/L
o
E
r
.6
V
V
N I LEGEND
.01 Dry Cell
V1N <= 05
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
L�
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
0 500 1,000
Feet
Figure 23 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Shallow Groundwater Zone
0.5 - 1 (Standard)
P
i
1 -2.5 (Background
Concentration)
CI
0
2.5-5
_Y
T
5-50
x
50-250
m
`m
250- 1,000
s
u 161,000
- 5,000
0
a 5,000 - 7,306
m
E —
— DUKE ENERGY PROPERTY
c
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
—
?
—
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
L�
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
0 500 1,000
Feet
Figure 23 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Shallow Groundwater Zone

Notes:
1. tag/L =micrograms per liter
2. Antimony IMAC value = 1 tag/L
3. Antimony PPBC = 2.5 tag/L
E
cci
N
N
O
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL _
N BOUNDARY
MODEL DOMAIN
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 24 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Deep Groundwater Zone
N
LEGEND
F
m
Dry Cell
N
O
<= 0.5
L
0.5 - 1 (Standard)
LL
1 -2.5 (Background
Concentration)
�I
2.5-5
a
5-50
m
50-250
L
E
250- 1,000
- 5,000
161,000
0
a 5,000 - 7,306
DUKE ENERGY PROPERTY
c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUNDARYCOINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL _
N BOUNDARY
MODEL DOMAIN
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 24 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Antimony IMAC value = 1 pg/L
3. Antimony PPBC = 2.5 Ng/L a
l9
LEGEND
Dry Cell
0.5N
O
I
0.5 -1 (Standard)
1 -2.5 (Background
r Concentration)
0
2.5-5
o'
a 5-50
m
50-250 '
L
E 250-1,000
lT/
ISI 1,000 - 5,000
0
a 5,000 -7,306
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
V
MODEL DOMAIN
I
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
= J
N
A
0 500 1.000
Feet
Figure 25 Existing Conditions Scenario 1 - 2115 Predicted Antimony Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Antimony IMAC value = 1 pg/L
3. Antimony PPBC = 2.5 pg/L
E
cci
N
N
l9
N
LEGEND
m
Dry Cell
N
O
<= 0.5
I
L
0.5 - 1 (Standard)
U-
1 -2.5 (Background
Concentration)
V
0
2.5-5
a
5-50
m
50-250
L
E
250- 1,000
- 5,000
161,000
0
a 5,000 - 7,306
E _
DUKE ENERGY PROPERTY
N
BOUNDARY
m
ASH BASIN WASTE
L
m
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
c
w
ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 26 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Antimony IMAC value = 1 Ng/L
3. Antimony PPBC = 2.5 pg/L
LEGEND
a Dry Cell
V
<= 0.5
7
0.5 - 1 (Standard)
Q 1 -2.5 (Background
CI Concentration)
0
2.5-5
_Y
i 5-50
Z
m
50-250
in
250-1,000
s
1,000 - 5,000
0
a 5,000 - 7,306
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
i—
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 27 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Deep Groundwater Zone

Notes:
1. tag/L = micrograms per liter
2. Antimony IMAC value = 1 tag/L
3. Antimony PPBC = 2.5 Ng/L
E
(6
N
N
LEGEND
co I
Dry Cell
N�
— 0.5
O
0.5 - 1 (Standard)
1 -2.5 (Background
r Concentration)
0
2.5-5
E: 5-50
50-250
L
E 250-1,000
lT/
ISI 1,000 - 5,000
0
a 5,000 - 7,306
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
V
MODEL DOMAIN
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 28 Cap -in -Place Scenario 2 - 2115 Predicted Antimony Concentrations in Bedrock Groundwater

12.0
10.0
8.0
bo 6.0
C
0
I` 4.0
00
C
0
V 20
0.0 +
Ln
uO
m
ri
Predicted Arsenic Concentration at AB -1S
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Existing Conditions
Cap -in -Place
— -Arsenic 2L
00 o rrl s.D c o o rrl s.D 00 o rry ;.D W o
ai o O O O O ri r -I ri r -I r -I N N N N N M
r -I N N N N N N N N N N N N N N N N
M otes:
1. µg/L=rncrogramsperliter
2. Ars en it 2L Sta ndard = S o jig/ L
S. Arsenic PRBC=54g/L
Time (Years)
Figure 29 Predicted Arsenic in Monitoring Well A13 -1S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 30 Predicted Arsenic in Monitoring Well A13 -2S
Predicted Arsenic Concentration at AB -2S
12.0
10.0_-----�—
—Existing Conditions
$ 0
_
Cap -in -Place
—
-,arsenic 2L
6.0
b
C
O
+, 4.0
ca
v
U
Mann
2.0
0.0
-,
� 00 o
I'D o N I'D o
N
a
m rn o
rri 00 00
0 0 o a r -I r_� r -I r. -i r_q rq
N N r� r.r r.i
N
r�
�.D 00
N N ry ro
ati c.i ry rd
Notes:
1. µg/L=rnicroaranuperliker
Time (Years)
2. Arsenic 2L Standard= l4 M/L
S. Arsenic PPBC=5M/L
Figure 30 Predicted Arsenic in Monitoring Well A13 -2S

12.0
10.0
ouo
6.0
0
0
4.0
ar
0
V
2.0
0.0 cc�� ¢¢
0 0000 N 000 C7 N 0�0 b N 0�0
07 0) O 'O O 0 Q .1 N N N N N M
�-I —i N N N N N N N N N N N N N N N N
Notes:
1. µg/L = micrograms per liter
2. Arsenic 2LStandard=10kg/L Time (Years)
3. Arsenic 'PPBC = 5µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Arsenic Concentration at GWA-15
Figure 31 Predicted Arsenic in Monitoring Well GWA-1S

12.0
110111;
111
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Arsenic Concentration at MW -65
0.0
Lr)�t Tt �t
z ooCD N
rn CD CD
rq
Motes:
1. µg/L=microgramsper liter
2. Arsenic2L3tandard=10 µg/L
3. Arsenic PPBC=5M/L
z 00 0 r � Kt o00 c N z X c
N CD CD
N N
Time (Years)
Figure 32 Predicted Arsenic in Monitoring Well MW -6S

Notes:
1. pg/L = micrograms per liter
2. Arsenic 2L Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
E
(6
N
N
N I LEGEND
Dry Cell
NI _
O
1-2.3
2.3 - 5 (Background
r Concentration)
0
5 -10 (Standard)
a 10-100
m
100-250
L
E 250-500
m
500-2,500
O
a 2,500 - 5,144
E — —
DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1.000
Feet
Figure 33 Initial (2015) Arsenic Concentrations in Shallow Groundwater Zone

E
D
V
V
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L = micrograms per liter ✓ ,� !
2. Arsenic 21- Standard = 10 pg/L !
3. Arsenic PPBC = 5 pg/LOIL~
Amer,
N LEGEND
n Dry Cell
14
<= 1
i
1-2-3
P 2.3 - 5 (Background
CI Concentration)
0
r 5 - 10 (Standard)
i
10-100
x
100-250
`m
250-500
s
u 16500-2,500
0
a 2,500 - 5,144
E
DUKE ENERGY PROPERTY
c BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
DLANDFILL/STRUCTURAL FILL _
N BOUNDARY
U '
MODEL DOMAIN
r
N
A
0 500 1.000
Feet
Figure 34 Initial (2015) Arsenic Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Arsenic 2L Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
C9
N LEGEND
I
m Dry Cell y
N
o
L
1-2.3
LL 2.3 - 5 (Background
�I Concentration)
5 - 10 (Standard) 1
a 10-100 {1
100-250
m
L
E 250-500
`m
`
500-2,500
0
a 2,500 - 5,144
m
E �
� DUKE ENERGY PROPERTY
c
BOUNDARY
N
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N
_
BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 35 Initial (2015) Arsenic Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Arsenic 2L Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
N I LEGEND
Dry Cell
NI _
O
1-2.3
LL 2.3 - 5 (Background
�i Concentration)
0
5 -10 (Standard)
a 10-100
100-250
m
L
250-500
l9
N500-2,500
0
a 2,500 - 5,144
E — —
DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
o O.5 MILE OFFSET FROM ASH
0- I — — BASIN COMPLIANCE
rn BOUNDARY
6 LANDFILL/STRUCTURAL FILL
N BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
� = J
N
A
0 500 1.000
Feet
Figure 36 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Arsenic 2L Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
N LEGEND
m Dry Cell y
N F� <= 1 11
o
i
L
1-2-3
LL 2.3 - 5 (Background
�I Concentration)
0
5 - 10 (Standard)
10-100
100-250
m
E 250-500
`m
16 500-2,500
0
a 2,500 - 5,144
DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
V
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH L%
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
e _ ,r • I _
t
— — BASIN COMPLIANCE
rn BOUNDARY
-
\
LANDFILL/STRUCTURAL FILL
N BOUNDARY
_
MODEL DOMAIN
N
A
0 500 1.000
Feet
Figure 37 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Arsenic 21- Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N LEGEND
p
m Dry Cell y
N
o
L
1-2.3
LL 2.3 - 5 (Background
�I Concentration)
5 - 10 (Standard) 1
a
10-100 1l
100-250
m _ !
E 250-500
`m
16 500-2,500
0
a 2,500 - 5,144
m
E � � DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
V
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL _ r
N BOUNDARY
V
MODEL DOMAIN
N
A
0 500 1.000
Feet
Figure 38 Existing Conditions Scenario 1 - 2115 Predicted Arsenic Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Arsenic 2L Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
E
cc
N
N
OI
l9
LEGEND
Dry Cell
N _
OI
a�
1-2.3
LL 2.3 - 5 (Background
�i Concentration)
0
0 5 -10 (Standard)
a 10-100
=�
100-250
m
2 250-500
N500-2,500
0
a 2,500 - 5,144
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
0
0.5 MILE OFFSET FROM ASH
r
BASIN COMPLIANCE
N
rn
BOUNDARY
n
o
LANDFILL/STRUCTURAL FILL
N
m
BOUNDARY
0 500 1.000
U
MODEL DOMAIN
Feet
Figure 39 Cap -in -Place Scenario 2 -
2115 Predicted Arsenic Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Arsenic 2L Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
E
N
N
N LEGEND
e
m Dry Cell y
N
C
L 1-2.3
LL 2.3 - 5 (Background
�I Concentration)
5 - 10 (Standard) 1
¢ 10-100 {l
100-250
m
L
E 250-500
`m
` 500-2,500
0
a 2,500 - 5,144
m
E � � DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARYok Will.
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL 60MAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 40 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Arsenic 2L Standard = 10 pg/L
3. Arsenic PPBC = 5 pg/L
E
cci
N
N
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
LEG END
m Dry Cell y
N <= 1 11
o
L
1-2.3
LL 2.3 - 5 (Background
LI Concentration)
5 - 10 (Standard) 1
a 10-100 {1
100-250
m _
E 250-500
`m
16 500-2,500
0
a 2,500 - 5,144
m
E � � DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
V
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
N
— — BASIN COMPLIANCE
rn BOUNDARY
-
LANDFILL/STRUCTURAL FILL
N BOUNDARY
_ r
MODEL DOMAIN
r
N
A
0 500 1.000
Feet
Figure 41 Cap -in -Place Scenario 2 - 2115 Predicted Arsenic Concentrations in Bedrock Groundwater Zone

800.0
700.0
600.0
500.0
r-,
�
400.0
c
a
+� 300.0
c
m
200.0
100.0
0.0
Ln It
rID0
cc
)
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Barium Concentration at AB -1S
Notes:
1. µ;;IL=rnicro:grarnsperliter
2. Bariurn 2L Standard = 7DD pgf L
3. Bariurn PPB C=157.3 pg/L
CD N � 00 CD N � 00 o N � 00 CD
Q Q CD CD Q����� N N N N r4 rn
Time (Years)
Figure 42 Predicted Barium in Monitoring Well AB -1S

r.1a411C
700.0
600.0
500.0
400.0
0
300.0
200,0
u
100.0
0.0
00CD N
cr, CD CD
Notes:
1. pfl/L=mieroaramsperliter
2. BaIum 2L Standard =744µg/L
3. Barium PPBC=1S 7.3 pg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Barium Concentration at AB -25
CD
Q CD CD ����� N N N N N M
Time (Years)
Figure 43 Predicted Barium in Monitoring Well AB -2S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 44 Predicted Barium in Monitoring Well GWA-1S
Predicted Barium Concentration at GENA -1S
8001.0
700.0
600.0 -
—Existing
Conditions
Cap -in -Place
50101.0
r-,
—
-Barium 2L
470.01 m
c
0
300.01
-
200.0
-
0
U
1001.0
0.0
-
� 00
0 N � 00 o N � CD N
� 00 CD
crs m
rl rl
00
o o Q CD CD r. -i T__q T__q T__q T__q N N
N N n1 iV i'wl e� N CV N CV N N
N N N m
N N N c.l
Notes:
1. [ig/L=micragramsper liter
2. B a ri urn 2L Sta ndard = 70D M/L
Time (Years)
3_ &arium PPBC=157.3µg/L
Figure 44 Predicted Barium in Monitoring Well GWA-1S

:ff f
70,0.0
r-,
t 400.0
C
0
W 300.0
e�
C
Qv
200.0
0
U
1001.0
0.0 i Jar
Lr7 qf ;t
00 CD rl
0) cr) CD CD
r -I rl rJ N
Notes-
1- µgj'L= m icrog ra ms p er liter
2. Barium 2LStandard=744µg/L
3. Barium PPBC=157.3 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Barium Concentration at M'wJ1f-65
Existing Conditions
—Cap -in -Place
— -Barium 2L
00 CD r l tD 00 CD 4 L.D 04 CD
0 O C1 r1 r_� r1 r_� r1 N rU N rel N M
N N rl N N N N N N N N rl N N
Time (Years)
Figure 45 Predicted Barium in Monitoring Well MW -6S

Notes:
1. pg/L = micrograms per liter
2. Barium 2L Standard = 700 pg/L
3. Barium PPBC = 157.3 pg/L
E
N
N
l9
LEGEND
CU
Dry Cell
N
0
<=38.4
i
P
38.4-99
99 - 157.3 (Background
Concentration)
r
0
157.3-250
a
250-500
m
500 - 700 (Standard)
L
E
lT/
700-1,000
1,000 - 1,500
0
a
1,500 - 1,891
E
DUKE ENERGY PROPERTY
c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 46 Initial (2015) Barium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Barium 2L Standard = 700 pg/L
3. Barium PPBC = 157.3 pg/L
l9
N LEGEND
a Dry Cell
V
<=38.4
38.4-99
Q' 99 - 157.3 (Background
Ci Concentration)
0
157.3-250
Y
250-500
i
m
500 - 700 (Standard)
ro
700-1,000
s
1,000 - 1,500
0
a 1,500 - 1,891
E
DUKE ENERGY PROPERTY
c BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
DLANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
0
L j
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 47 Initial (2015) Barium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Barium 2L Standard = 700 pg/L
3. Barium PPBC = 157.3 pg/L
N LEGEND
p
n Dry Cell
V
—38.4
i
38.4 - 99
P 99 - 157.3 (Background
Concentration)
CI
r 157.3 - 250
1
{1
1 250 - 500
x
500 - 700 (Standard)
m
700- 1,000
s
1,000 - 1,500
u `
0
a 1,500 - 1,891
m
E � � DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
0 ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
DLANDFILL/STRUCTURAL FILL
_ r
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 48 Initial (2015) Barium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Barium 2L Standard = 700 Ng/L
3. Barium PPBC = 157.3 Ng/L
� • _...-• .--tee,•
E
N
N
N
LEGEND
CU
Dry Cell
N
of
<=38.4
a�
38.4 - 99
LL
99 - 157.3 (Background
Concentration)
�i
157.3 - 250
a
250 - 500
=�
m
500 - 700 (Standard)
L
E
lT/
700 - 1,000
1,000 - 1,500
0
a
1,500 - 1,891
E
DUKE ENERGY PROPERTY
'c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
0
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
6 LANDFILL/STRUCTURAL FILL
N BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 49 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Barium 2L Standard = 700 pg/L
3. Barium PPBC = 157.3 pg/L
N LEGEND
e
m Dry Cell y
N 11
o
<=38.4
i
L 38.4 - 99
99 - 157 3 (Back round
u-
Concentration)
�I
0
157.3 - 250
a
250 - 500
=�
m
500 - 700 (Standard)
L
E
l0
700- 1,000
1,000 - 1,500
`
0
a 1,500 - 1,891
DUKE ENERGY PROPERTY
'c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
o LANDFILL/STRUCTURAL FILL _
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 50 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Barium 2L Standard = 700 pg/L
3. Barium PPBC = 157.3 pg/L
N LEGEND
I
m Dry Cell y
N 11
o
<=38.4
i
38.4 - 99
z
LL 99 - 157.3 (Background
�I Concentration)
157.3 - 250 — 1
a 250 - 500 {1
=� 500 - 700 (Standard)
m
L
E 700- 1,000
l0
` 1,000 - 1,500
0
a 1,500 - 1,891
m
E � � DUKE ENERGY PROPERTY
c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
V
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
ml IN BOUNDARY
BOU
LANDFILL/STRUCTURAL FILL _ r
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 51 Existing Conditions Scenario 1 - 2115 Predicted Barium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Barium 2L Standard = 700 pg/L
3. Barium PPBC = 157.3 Ng/L
E
N
O
l9
LEGEND
CU
Dry Cell
N
0
<=38.4
i
38.4 - 99
99 - 157.3 (Background
Concentration)
r
0
157.3 - 250
a
250 - 500
m
500 - 700 (Standard)
L
E
lT/
700 - 1,000
1,000 - 1,500
0
a
1,500 - 1,891
DUKE ENERGY PROPERTY
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
6 I LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
I
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 52 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Shallow Groundwater Zone

J
es:Ig/L= micrograms per liter
arium 2L Standard = 700 Ng/L
arium PPBC = 157.3 pg/L
E
cci
N
N
O
_I
m
N LEGEND
CU
Dry Cell
N
of
<=38.4
2 38.4 - 99
99 - 157.3 (Background
VI Concentration)
0
157.3 - 250
a 250 - 500
m
500 - 700 (Standard)
L
E 700 - 1,000
lT/
1,000 - 1,500
0
a 1,500 - 1,891
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
J J
1
#o
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1.000
Feet
Figure 53 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Deep Groundwater Zone

Notes:
1. fag/L = micrograms per liter
2. Barium 2L Standard = 700 pg/L
3. Barium PPBC = 157.3 pg/L
N
LEGEND
CU
Dry Cell
N
0
<=38.4
i
38.4 - 99
99 - 157.3 (Background
Concentration)
r
157.3 - 250
a
250 - 500
m
500 - 700 (Standard)
L
E
lT/
700 - 1,000
1,000 - 1,500
0
a
1,500 - 1,891
DUKE ENERGY PROPERTY
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
6 LANDFILL/STRUCTURAL FILL
N BOUNDARY
8 MODEL DOMAIN
1
.11 i �, s
L J� �"' !
/ I
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 54 Cap -in -Place Scenario 2 - 2115 Predicted Barium Concentrations in Bedrock Groundwater Zone

Predicted Beryllium Concentration at AB-1S
4,5
4.0
15
10
15
an
0
2.0
m
c
1.5
1.0
0.5
0,0 -I
Ln It It It
tD as CD N
M M c CD
rl r-I r.l hJ
Notes:
1. �igv/L=microgramsper liter
2. BerylliumIMAEvalue=4µg/L
S. Beryl lium PPBC=1 �/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Existing Conditions -
Cap -in -Place
— -Beryllium IMAC
o c o r_� r_� r_� r_� "i N N N N N M
N N N N N N N N N N el N N N
Time (Years)
Figure 55 Predicted Beryllium in Monitoring Well AB-1S

4.5
4.0
3.5
3.0
2.5
tQ
2.0
D
}, 1.5
c
m
c�
0 1.0
U
0.5
0.0
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Beryllium Concentration at AB-2S
-Existing Conditions
Cap-i n-Place
-Beryllium IMAC
UD 00 0 N � 00 CD N � 00 a N � 00 CD
m C) ® o 0 a O ri ri ri ri ri N N N N N m
r-I r-i N N N N N N N N N N N N N N N N
Notes
1. IiE/L = rn icrogra rrn per liter
2. BerylliumIMAC value=4µg/L Time (Years)
3. BerylliumPPBC=1µg/L
Figure 56 Predicted Beryllium in Monitoring Well AB-2S

Predicted Beryllium Concentration at GWA-IS
4.5
4.0
3.5
3.0
ao
2.5
3
O 2.0
L
�
1.5
tr.7
1.0
0.5
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Existing Conditions
Cap -in -Place _.
-Berylliurn IIVAC
0.0 -I —�
LO
7 ;8 8�rt%j 4 Z8;8 8
r-I r-1 [V N N N N N fV N N N N N N N N N
Notes:
1. µg/L = micrograms per liter
2. Beryllium IMACvalue=4 WJL Time (Years)
3. Beryllium PPBC= I µg/L
Figure 57 Predicted Beryllium in Monitoring Well GWA-IS

Predicted Beryllium Concentration at MW-6
7.0
AD]
5.0
1.0
0.0
Ln I*It It
00 CD N
0) C) CD CD
r-I
Notes:
1. pgfL=micrtrgramsper liter
2. Beryl flu mIMAC vaWe=4µg/L
S. Beryl liu rn PPBC= I pipjL
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
C� O G r-I r-I rl "I "I N N N N rJ rn
rJ N N N N N N N N N N N N N
Time (Years)
Figure 58 Predicted Beryllium in Monitoring Well MW-6S

Notes:
1. pg/L = micrograms per liter
2. Beryllium IMAC value = 4 pg/L
3. Beryllium PPBC = 1 pg/L
k ,
E
(D
N
N
N
LEGEND
m
Dry Cell
N
0
<= 0.33
4I
0.33 - 1 (Background
—
Concentration)
CL
I
1 -4 (Standard)
4-6
a
8-9
m
9-12
L
E
ro
12-15
16
15 - 18
a 18 - 21.5
m
E — —
DUKE ENERGY PROPERTY
c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 59 Initial (2015) Beryllium Concentrations in Shallow Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Beryllium ]MAC value = 4 pg/L
3. Beryllium PPBC = 1 pg/L
°
E
D
V
V
N I LEGEND
.01 Dry Cell
<= 0.33
0.33 - 1 (Background
` Concentration)
rn
ci 1 -4 (Standard)
0
4-6
Y
i 6-9
m
9-12
C
12-15
U 15 - 18
0
° 18 - 21.5
a
E
DUKE ENERGY PROPERTY
c BOUNDARY
N
n ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L ASH BASIN COMPLIANCE
0
Y _ _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
m
0 0.5 MILE OFFSET FROM ASH
i — — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/5TRUCTURAL FILL
N
BOUNDARY
U
N MODEL DOMAIN
e
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
N
A
0 500 1,000
Feet
Figure 60 Initial (2015) Beryllium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Beryllium IMAC value = 4 pg/L
3. Beryllium PPBC = 1 pg/L
N LEGEND
n Dry Cell
V
<= 0.33
0.33 - 1 (Background
`
Concentration)
rn
CI
1 -4 (Standard)
0
N
4-6
Y
T
8-9
x
9-12
m
12-15
m
s
15 - 18
0
a 18 - 21.5
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
2
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 61 Initial (2015) Beryllium Concentrations in Bedrock Groundwater Zone

Notes:
1. Ng/L =micrograms per liter
2. Beryllium IMAC value = 4 Ng/L
3. Beryllium PPBC = 1 Ng/L
E + .
D
V
N I LEGEND
.01 Dry Cell
V1N <= 0.33
4
0.33 - 1 (Background
-
Concentration)
rn
CI
1 -4 (Standard)
0
N
4-6
Y
T
8-9
x
9-12
m
12-15
s
15 - 18
0
a 18 - 21.5
m
E —
— DUKE ENERGY PROPERTY
c
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
—
?
—
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
z� N
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 62 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Shallow Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Beryllium ]MAC value = 4 pg/L
3. Beryllium PPBC = 1 pg/L
911iF:
N
LEGEND
n
Dry Cell
4
<= 0.33
VI
0.33 - 1 (Background
`
rn
Concentration)
CI
1 -4 (Standard)
0
4-6
it 6-9
x
9-12
m
12-15
ro
s
15 - 18
0
a 18 - 21.5
E
DUKE ENERGY PROPERTY
c
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
2
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
FILL
ZLANDFILL/STRUCTURAL
N
BOUNDARY
MODEL DOMAIN
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 63 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Beryllium IMAC value = 4 Ng/L
3. Beryllium PPBC = 1 Ng/L
w1E -
D
V
V
N I LEGEND
.01 Dry Cell
<= 0.33
0.33 - 1 (Background
` Concentration)
rn
ci 1 -4 (Standard)
0
4-6
Y
i 6-9
m
9-12
C
12-15
U 15-1$
0
° 18 - 21.5
a
m
E � � DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L ASH BASIN COMPLIANCE
0
Y _ _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
m
0 0.5 MILE OFFSET FROM ASH
i — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/5TRUCTURAL FILL
N
BOUNDARY
U
N MODEL DOMAIN
u
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r* 4
N
A
0 500 1,000
Feet
Figure 64 Existing Condition Scenario 1 - 2115 Predicted Beryllium Concentrations in Bedrock Groundwater Zone

Notes:
1. fag/L = micrograms per liter
2. Beryllium IMAC value = 4 Ng/L
3. Beryllium PPBC = 1 gg/L
V
V
CI
N LEGEND
n Dry Cell
V
<= 0.33
D
0.33 - 1 (Background
`
Concentration)
rn
CI
1 -4 (Standard)
0
N
4-6
Y
T
8-9
x
9-12
m
12-15
m
s
15 - 18
0
a 18 - 21.5
E —
— DUKE ENERGY PROPERTY
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
k),
�r
4
map-
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
NN
1
1 500 1,000
a-
r -
et
1a N
-
il
Figure 65 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Shallow Groundwater Zone

Notes:
1. ug/L =micrograms per liter
2. Beryllium IMAC value = 4 Ng/L
3. Beryllium PPBC = 1 Ng/L
.6
V
V
l9
N LEGEND
n Dry Cell
V
<= 0.33
0I 0.33 - 1 (Background
= Concentration)
rn
CI 1 -4 (Standard)
0
4-6
it 6-9
x
9-12
m
12-15
ro
s
15 - 18
0
a 18 - 21.5
m
E �
� DUKE ENERGY PROPERTY
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
L
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
FILL
ZLANDFILL/STRUCTURAL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 66 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Beryllium IMAC value = 4 Ng/L
3. Beryllium PPBC = 1 Ng/L
i
N I LEGEND
.01 Dry Cell
<= 0.33
0.33 - 1 (Background
` Concentration)
rn
ci 1 -4 (Standard)
0
4-6
Y
i 6-9
m
9-12
C
12-15
U 15 - 18
0
° 18 - 21.5
a
m
E � � DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L ASH BASIN COMPLIANCE
0
Y _ _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
m
0 0.5 MILE OFFSET FROM ASH
i — — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/5TRUCTURAL FILL
N
BOUNDARY
U
N MODEL DOMAIN
y
4- r
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 67 Cap -in -Place Scenario 2 - 2115 Predicted Beryllium Concentrations in Bedrock Groundwater Zone

Predicted Boron Concentration at AB-1S
2,000
1,800
1,600
1,400
aO
1,200
c
O
1,000
L
U
800
r-
O
u
600
400
200
0
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Ln lD 00 N Cf 0�0 f�V Z� 0Zo N lC1
f]� M Q Q O Q 0 c-I r-I •--I -1 -1 N N N N
.--I -4 N [V rV N N N N N N N N rV N N
Notes:
1. µg/L = micrograms per liter
2.Boron 2LStandard =700µg/L Time (Years)
3_ Boron PPBC= 100 µg/L
Figure 68 Predicted Boron in Monitoring Well ABAS

Predicted Boron Concentration at AB-2S
M
700
M
J
500
0
400
r�
r- 300
0
u
200
100
0
Sip 00 N 0000 N CO N
M M Q Q O O 4 —4 —I r-I r-I r-I N N N N
N N N N N N N N N N N N
Notes:
1. µg/L = micrograms per liter
2.Boron 2LStandard =700µg/L Time (Years)
3. Boron PPBC = 100 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 69 Predicted Boron in Monitoring Well AB-2S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Boron Concentration at GWA-IS
s00
700 -
600 -
Existing Conditions
_
Cap -in -Place
t
4 500
-Boron ZL
O
P 400
300 -
G
V
200 -
100
0LO -
C�
lD 00 N Cf 0�0 f��l 00*0 N
CV) a) Q Q O Q 0 c-I r-I •--I .--I -1 N rV N N
.--I .--I N [V N N N N N N N N N N N N
Notes:
1. µg/L = micrograms per liter
Time (Years)
2.Boron 2LStandard =700µg/L
3. Boron PPBC = 100 µg/L
Figure 70 Predicted Boron in Monitoring Well GWA-IS

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Boron Concentration at MW-65
800
700
600
500
tw
400
Existing Conditions
300
Cap -in -Place
u
-
-Boron 2L
0 200
100
0
N
¢¢
N Cb
C4 0000
t7) M
0000 0000
O O O O O
N N N N
r-I c-I
N N N N N N N N N N
N N N N
Notes:
1. µg/L = micrograms per liter
Time (rears)
2.Boron 2LStandard =700µg/L
3_ Boron PPBC= 100 µg/L
Figure 71 Predicted Boron in Monitoring Well MW-6S

Notes:
1. Ng/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC = 100 pg/L
V_
'1I LEGEND
C
N
Dry Cell
N
C
-- 50
I
50 - 100 (Background
m
Concentration)
100 - 350
350 - 700 (Standard) ,W
700 - 2,000
N
s 2,000 - 5,000
0 5,000 - 10,000
0
a 10,000 - 20,000
c 20,000 - 90,000
'm
m
n DUKE ENERGY PROPERTY
C � �
3 BOUNDARY
rn ASH BASIN WASTE
BOUNDARY
L
r ASH BASIN COMPLIANCE
BOUNDARY
u ASH BASIN COMPLIANCE
° _ BOUNDARY COINCIDENT
2 WITH DUKE ENERGY
N PROPERTY BOUNDARY
rn
D LANDFILL/STRUCTURAL
N
FILL BOUNDARY
MODEL DOMAIN
III
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
��.An
N
A
0 500 1,000
J �
Feet
Figure 72 Initial (2015) Boron Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC - 100 pg/L
'1I LEGEND /
C
N
'_ Dry Cell
in
<= 50
I �
50 - 100 (Background
m
Concentration)
100 - 350
350 - 700 (Standard)
700 - 2,000
N
s 2,000 - 5,000 1
0 5,000 - 10,000
0
a 10,000 - 20,000
E
c 20,000 - 90,000
N
ro
n _ DUKE ENERGY PROPERTY
C �
3 BOUNDARY
m ASH BASIN WASTE
0) BOUNDARY
C
r ASH BASIN COMPLIANCE
j BOUNDARY
ASH BASIN COMPLIANCE
° BOUNDARY COINCIDENT
o
i WITH DUKE ENERGY
05
I PROPERTY BOUNDARY
LANDFILL/STRUCTURAL
z FILL BOUNDARY
N
MODEL DOMAIN
I
011
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 73 Initial (2015) Boron Concentrations in Deep Groundwater Zone
11111110 1
N
0 500 1,000
Feet

Notes:
1. pg/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC = 100 pg/L
LEGEND
Dry Cell
V)
r-
- — 50
I
50 - 100 (Background
m
Concentration)
' 100 - 350
350 - 700 (Standard)
700 - 2,000
N
s 2,000 - 5,000
0 5,000 - 10,000
0
10,000 - 20,000
c - 20,000 - 90,000
N
ro
n DUKE ENERGY PROPERTY
C �
3 BOUNDARY
oTi ASH BASIN WASTE
BOUNDARY
r ASH BASIN COMPLIANCE
j BOUNDARY
ASH BASIN COMPLIANCE
o BOUNDARY COINCIDENT
i WITH DUKE ENERGY
rn PROPERTY BOUNDARY
LANDFILL/STRUCTURAL
z FILL BOUNDARY
N
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
s
0 500 1,000
Feet
Figure 74 Initial (2015) Boron Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC = 100 pg/L
LEGEND
Dry Cell
V)
C
i
50 - 100 (Background
Concentration)
100 - 350
350 - 700 (Standard)
4
l\
700 - 2,000
N
s 2,000 - 5,000
0 5,000 - 10,000
0
10,000 - 20,000
c 20,000 - 90,000
'm
n DUKE ENERGY PROPERTY
C � �
3 BOUNDARY
rn ASH BASIN WASTE
0) BOUNDARY
L
r ASH BASIN COMPLIANCE
BOUNDARY
u ASH BASIN COMPLIANCE
o _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
LANDFILL/STRUCTURAL
N FILL BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
0 500 1,000
Feet
Figure 75 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC = 100 Ng/L e
"1I LEGEND
C
Dry Cell
c
c° <= 50
M
50 - 100 (Background
E2 Concentration)
m
100 - 350
v 350 - 700 (Standard)
700 - 2,000
E2
2,000 - 5,000 -1
0 5,000 - 10,000
a 10,000 - 20,000
E
'c 20,000 - 90,000
N
ro
m _ DUKE ENERGY PROPERTY
L �
BOUNDARY
m ASH BASIN WASTE
0 BOUNDARY
w
Y ASH BASIN COMPLIANCE
p BOUNDARY
ASH BASIN COMPLIANCE
o _ BOUNDARY COINCIDENT
0- WITH DUKE ENERGY
.NI PROPERTY BOUNDARY
rn
o I LANDFILL/STRUCTURAL
Z FILL BOUNDARY
N
r MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
1
N
A
0 500 1,000
Feet
Figure 76 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Deep Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 77 Existing Conditions Scenario 1 - 2115 Predicted Boron Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC = 100 pg/L
P
x
x
E
o �
vi
LEGEND
C
Dry Cell
c) IL<= 50
f
r
m 50 - 100 (Background
N Concentration)
`b
100 - 350
350 - 700 (Standard)
1
t 700 - 2,000
2,000 - 5,000
N It 1
0
5,000 - 10,000
0
a
10,000 - 20,000
E
20,000 - 90,000
m
m
DUKE ENERGY PROPERTY
_
L -
BOUNDARY
rn
ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
o BOUNDARY
ASH BASIN COMPLIANCE
— — BOUNDARY COINCIDENT
a WITH DUKE ENERGY
PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
z FILL BOUNDARY
N
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
k
0 500 1,000
Feet
Figure 78 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC = 100 pg/L
x
E
N
"1I LEGEND
Dry Cell
C
c i � <= 50
i
r 50 - 100 (Background
N 1 Concentration)
100 - 350
350 - 700 (Standard)
t 700 - 2,000
N
2,000 - 5,000
5,000 - 10,000
0
-o
10,000 - 20,000
CU
_ 20,000 - 90,000
N
ro
DUKE ENERGY PROPERTY
3 BOUNDARY
rn _ ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
o BOUNDARY
u ASH BASIN COMPLIANCE
o _ _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
z FILL BOUNDARY
P
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 79 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Boron 2L Standard = 700 pg/L
3. Boron PPBC = 100 pg/L
LEGEND
Dry Cell
C
c i � <= 50
i
r 50 - 100 (Background
N 1 Concentration)
100 - 350
350 - 700 (Standard)
t 700 - 2,000
N
2,000 - 5,000
5,000 - 10,000
v
10,000 - 20,000
CU
_ 20,000 - 90,000
N
ro
DUKE ENERGY PROPERTY
3 BOUNDARY
rn _ ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
o BOUNDARY
u ASH BASIN COMPLIANCE
o _ _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
z FILL BOUNDARY
P
MODEL DOMAIN
i
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 80 Cap -in -Place Scenario 2 - 2115 Predicted Boron Concentrations in Bedrock Groundwater Zone

34[?,4QO
25a,DDO
2GD,4Q0
r—,
3 15a,GGO
O
M
14C),4Q0
c3
0
V
.1 11C
0
Ln
tD
cr)
ri
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Chloride Concentration at AB-1S
vt 000 CD N � 00 O N �t s.DD 00 O N w cc a
a) O rD O CD O r-I r-I r-I r-I r-I N N N N N M
r-I N N N N N N N N N N N N N N N N
Notes:
1. µg/L=micrograrnsper liter
2.ChIoride2L5tandard=L90,ODDMJL Time (Years)
3. Chloride PPBC = 3,900 µgf L
Figure 81 Predicted Chloride in Monitoring Well ABAS

Predicted Chloride Concentration at AB-25
3(]4,DGG
250,000
gal},BI}4
3 15o,l)oa
0
M
w
0
U 54,40t7
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Existing Conditions
—Cap-in-Place
— -Chloride A
C) } �}
� CO O N tZo 0 o N �.D 000 0 N ..D 00 o
am rn 0 0 0 0 0 r-I r-I r_� r-I r-I N N N rwl N ro
rl "I rV N N N N N N N rV N N rU N rV N rV
Notes:
1. µg/L= micrograms per liter
Z_Chloride2LStandard=250,000pigfL Time (Years)
3_ Chloride PPBC= 3,544 µg/L
Figure 82 Predicted Chloride in Monitoring Well A13-2S

25 a,0OO
20a,0OO
� 15Q,0OO
0
Ln It
sD 00
rn am
Notes:
S. µg/L=rn crogramsper ter
2. ChIonde2LStandard=25b,000pg1L
S. ChIoridePPEIC= 5,5W µgf L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Chloride Concentration at GWA-1
CD � voo a N s�D [ 0 CD N c�D C00 CD
Ca CD CD O CD rl rl rl rl rl N r4 N N N rn
N N N N N N N N N N N N N N N N
Time (Years)
Figure 83 Predicted Chloride in Monitoring Well GWA-1S

3()0,0D'®'
250,0D0
20D,000
J
ba 150,000
7
C
0
1DD,000
C
s�
C
G
V sD,000
0
Ln It
CD 44
C) 01
r-I ri
Predicted Chloride Concentration at MW-65
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
ons
It N � 00 o N � 00 a N � 00 o
CD O CD O CD ri r-I ri r-I r-I N N N N N fln
N N N N N N N N N N N N N N N N
N ates:
1. µg/L=micragramsper liter
2.Chloride2L5tartdard=250,OOOpLg/L Time (Years)
S. ChlaridePPBC= 3,5W µg/L
Figure 84 Predicted Chloride in Monitoring Well MW-6S

Notes: I
1. pg/L = micrograms per liter
2. Chloride 2L Standard =
250,000 pg/L
3. Chloride PPBC = 3,500 pg/L
N yy
O ■�
L LEGEND
N
? Dry Cell
m
N pr — 3,500 (Background
o Concentration)
L
3,500 - 5,000
LL
5,000 - 9,810
a
9,810 - 15,000
15,000 - 50,000
a
¢
U
50,000 - 100,000
m
100,000 - 250,000
(Standard)
250,000 - 500,000
4
0
a 500,000 - 751011
DUKE ENERGY PROPERTY
'c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
N BOUNDARY
rn
LANDFILL/STRUCTURAL FILL
N BOUNDARY
80
M MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
f4 A
�r
P-
N
0 500 1,000
Feet
Figure 85 Initial (2015) Chloride Concentrations in Shallow Groundwater Zone

Notes: I f�
1. pg/L = micrograms per liter
2. Chloride 2L Standard =
250,000 pg/L
3. Chloride PPBC = 3,500 pg/L
p C
E r �j
V
V"
N
LEGEND
>
n
Dry Cell
Pr
<= 3,500 (Background
Concentration)
0
3,500 - 5,000
5,000 - 9,810
9,810 - 15,000
15,000 - 50,000
50,000 - 100,000
100,000 - 250,000
(Standard)
s
u 4
250,000 - 500,000
0
a 500,000 - 751011
E
DUKE ENERGY PROPERTY
c
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
DLANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 86 Initial (2015) Chloride Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Chloride 2L Standard =
250,000 Ng/L
3. Chloride PPBC = 3,500 fag/L
t LEGEND
N
A
Dry Cell
m
N <= 3,500 (Background
o Concentration)
0 3,500 - 5,000
0I
L 5,000 - 9,810
R I 9,810 - 15,000
15,000 - 50,000
50,000 - 100,000
t 100,000 - 250,000
(Standard)
250,000 - 500,000
0
a 500,000 - 751011
E
DUKE ENERGY PROPERTY
'c BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
0- — — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
0 500 1.000
Feet
Figure 87 Initial (2015) Chloride Concentrations in Bedrock Groundwater Zone

Notes:
1. fag/L = micrograms per liter
2. Chloride 2L Standard =
250,000 pg/L
3. Chloride PPBC = 3,500 pg/L "
N
N yy
O ■�
L LEGEND
N
? Dry Cell
m
N pr — 3,500 (Background
o Concentration)
L
3,500 - 5,000
LL
5,000 - 9,810
�I
a
9,810 - 15,000
15,000 - 50,000
a
¢
U
50,000 - 100,000
m
100,000 - 250,000
(Standard)
250,000 - 500,000
4
0
a 500,000 - 751011
m
E �
� DUKE ENERGY PROPERTY
c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUND ARYCOINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
ZLANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 88 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Chloride 2L Standard =
250,000 pg/L
3. Chloride PPBC = 3,500 Ng/L
N
LEGEND
>
n
Dry Cell
Pr
<= 3,500 (Background
Concentration)
0
3,500 - 5,000
5,000 - 9,810
9,810 - 15,000
15,000 - 50,000
50,000 - 100,000
100,000 - 250,000
(Standard)
s
u 4
250,000 - 500,000
0
a 500,000 - 751011
E
DUKE ENERGY PROPERTY
c
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
i N
0 500 1,000
Feet
Figure 89 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Deep Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
LANDFILL/STRUCTURAL FILL
N BOUNDARY
V
MODEL DOMAIN
Figure 90 Existing Conditions Scenario 1 - 2115 Predicted Chloride Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Chloride 2L Standard =
250,000 pg/L
3. Chloride PPBC = 3,500 pg/L
E
cci
N
N
O
L LEGEND
? Dry Cell
m
N pr — 3,500 (Background
o Concentration)
L
3,500 - 5,000
LL
5,000 - 9,810
�I
a
9,810 - 15,000
15,000 - 50,000
a
¢
U
50,000 - 100,000
t
100,000 - 250,000
(Standard)
250,000 - 500,000
4
0
a 500,000 - 751011
m
E �
� DUKE ENERGY PROPERTY
c
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
� ;v
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
0 500 1,000
Feet
Figure 91 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L =micrograms per liter
2. Chloride 2L Standard =
1■..�'
250,000 pg/L
3. Chloride PPBC = 3,500 pg/L
o -
D '
V
V
LEGEND
N
Dry Cell
D
<= 3,500 (Background
Concentration)
W 3,500 - 5,000
5,000 - 9,810
9,810 - 15,000
15,000 - 50,000
50,000 - 100,000
100,000 - 250,000
(Standard)
s
250,000 - 500,000
0
a 500,000 - 751011
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
J
i
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1,000
Feet
Figure 92 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Chloride 2L Standard =
250,000 Ng/L
3. Chloride PPBC = 3,500 Ng/L
0
E
D
V
V
LEGEND
N
Dry Cell
a
<= 3,500 (Background
Concentration)
3.500 - 51000
P 5,000 - 9,810
o I 9,810 - 15,000
15,000 - 50,000
50,000 - 100,000
100,000 - 250,000
(Standard)
s
250,000 - 500,000
0
a 500,000 - 751011
E
DUKE ENERGY PROPERTY
c BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
2 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
1
4i
10
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
t
N
A
0 500 1,000
Feet
Figure 93 Cap -in -Place Scenario 2 - 2115 Predicted Chloride Concentrations in Bedrock Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Chromium Concentration at AB -1ST
12.0
10.0
misting Conditions
Cap -in -Place
8.0
—
-Chromiurm 2L
6.0
0
4.©
0
u
2.0
0.0 -
C)� CD
CD CD CD CD ����� N rq
N rq N CD
ro
Mates:
1. µ-/L=microgramsperliter
Time (Years)
2. Chromium2LStandard=10µdL
3. Chromium PPRC=11.3 µgJL
Figure 94 Predicted Chromium in Monitoring Well AB -IS

12.0
11M
M.
ba 6.0
c
0
4.0
c
�u
c
0
U 20
Predicted Chromium Concentration at AB-2S
Ln
r4D00 c N
0) � 0 0 0
r-I
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
It It It It 4 � 4t � �t 4��t It
c.a oa c N CA 40 0 N z oo a
a rl rl rl r-� r-� N N r.l rJ rJ Cn
r.l r.l N N r.l r.l r l r.l
Notes:
1. µg{L=microgramsperliter
2.Chromium2LStenderd=10pg/L Time (Years)
S. ChromiumPP8C=11.3 Ng/L
Figure 95 Predicted Chromium in Monitoring Well A13-2S

Predicted Chromium Concentration at GWA-15
11.4
11.2
11.0
10.8
10.6
r-
0
10.4
c
10.2
0
U
10.0
9.8
Ln
cc a �
rq rq N
N ates.:
1. µg/L= micrograms per liter
2. Chromium 2LStandard=1Olrg/L
S. ChromiumPPBC=11.5 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
It tt It It 4 Int Int Iqt t 4 �t llzt It
�.D cc o N sID 00 CD N s.D 00 0
Co o r-I ri r-I ri r-I N N N N N ro
N N N N N N N N N N N N N
Time (Years)
Figure 96 Predicted Chromium in Monitoring Well GWA-1S

Predicted Chromium Concentration at MW-6S
25.0
20.0
15.0
0
L 10.0
i3
0
U
5.0
0.0
S.O 40 O N 5.O 00
rl s-I N N N N N
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
O N s.D cc O N S.D 00 O
ri r-I r' r-I r' N N N N N rn
N N N N N N N N N N N
Notes
1. µgfL= micrograms per liter
2.Chromium2L5tarrdard=14µgfL Time (Years)
3- Chromium PPBC=11.3 ugf L
Figure 97 Predicted Chromium in Monitoring Well MW-6S

Notes:
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 pg/L
l9
ro
LEGEND
a Dry Cell
V r
5
1.9 - 5
P 5-8
CI
8 - 10 (Standard)
r 10 - 11.3 (Background
i Concentration)
x
11.3 - 30
m
m
30 - 60
60 - 90
0
a 90 - 123
E — —
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
m
— — BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
2 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
u f
h�
f
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
nN
7
N
A
0 500 1.000
Feet
Figure 98 Initial (2015) Chromium Concentrations in Shallow Groundwater Zone

Notes: 10
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 pg/L iP
E
.6
V
V
OI LEGEND
ro
a Dry Cell
V r
1.9 - 5
P 5-8
C
0 8 - 10 (Standard)
a
r 10 - 11.3 (Background
i Concentration)
x
11.3 - 30
m
N 30 - 60
m
60 - 90
0
a 90 - 123
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
2 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
L I
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
`!p N
0 500 1.000
Feet
Figure 99 Initial (2015) Chromium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 pg/L
0
D
LEGEND y
ro
a Dry Cell
V r
1.9 - 5
P 5-8
C
0 8 - 10 (Standard)
a
r 10 - 11.3 (Background
i Concentration)
x
11.3 - 30
m
m
30 - 60
60 - 90
0
a 90 - 123
E — —
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
m
— — BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 100 Initial (2015) Chromium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 Ng/L
LEGEND
s
9 Dry Cell
V
m 1.9 - 5
°°I 5-8
C
°0 8- 10 (Standard)
r 10 - 11.3 {Background
T Concentration)
i
11.3 - 30
30 - 60
d: 60 - 90
a 90 - 123
E � � DUKE ENERGY PROPERTY
BOUNDARY
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
c
L ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
U PROPERTY BOUNDARY
w
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
m BOUNDARY
LAND FILLSTRUCTURAIL FILL
m BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
0 500 1,000
® �1
�f Feet
Figure 101 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in Shallow Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L = micrograms per liter (` y ! !
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 pg/LOIL
0
E
.6
V
V
l9
N LEGEND
n Dry Cell y
V 4
1.9-5
P 5 8
0 8- 10 (Standard)
r 10 - 11.3 (Background
i Concentration)
x I
11-3-30
30 - 60
ro
s
4 60 - 90
0
a 90-123
E
DUKE ENERGY PROPERTY
BOUNDARY
N �-
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
L ASH BASIN COMPLIANCE
0
BOUND ARYCOINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL _ r
n BOUNDARY
MODEL DOMAIN
N
A
0 500 1.000
Feet
Figure 102 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 Ng/L
LEGEND
ca
Dry Cell
N r
o
i
1.9 - 5
LL 5-8
r�
a
8 - 10 (Standard)
10 - 11.3 (Background
a Concentration)
11.3 - 30
m
L
E 30 - 60
m
N 60 - 90
0
a 90 - 123
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
N BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
CL I — — BASIN COMPLIANCE
rn BOUNDARY
6 I LANDFILL/STRUCTURAL FILL
BOUNDARY
U
MODEL DOMAIN
Y
A
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1.000
Feet
Figure 103 Existing Conditions Scenario 1 - 2115 Predicted Chromium Concentrations in Bedrock Groundwater Zone

Notes: 10
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 pg/L iP
i
N LEGEND
n Dry Cell
V
1.9-5
rn 5 8
0 S- 10 (Standard)
r 10 - 11.3 (Background
i Concentration)
x j
11.3 - 30
if) An
u 4
i60 - 90
0
a 90-123
E _
_ DUKE ENERGY PROPERTY
�
BOUNDARY
N
m
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L
0
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
—
—
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
-
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1.000
Feet
Figure 104 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 pg/L
E
.6
V
V
�I LEGEND
a Dry Cell
V r /
1.9 - 5
P 5-8
i
C
0 8 - 10 (Standard)
a
r 10 - 11.3 (Background
i Concentration)
x
11.3 - 30 '
m
m
30 - 60
60 - 90
0
a 90 - 123
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
2 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
s_ )
1! I +t
N
A
0 500 1.000
Feet
Figure 105 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Chromium 2L Standard = 10 pg/L
3. Chromium PPBC = 11.3 pg/L r
LEGEND
ca
Dry Cell
N
o
1.9 - 5
LL 5-8
r�
a
8 - 10 (Standard)
10 - 11.3 (Background
a Concentration)
11.3 - 30
m
L
E 30 - 60
m
N 60 - 90
0
a 90 - 123
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
N BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
6 I LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1.000
Feet
Figure 106 Cap -in -Place Scenario 2 - 2115 Predicted Chromium Concentrations in Bedrock Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Cobalt Concentration at AB -IS
3.0
—Existing Conditions
—Cap-in-Place
2.5 — -Cobalt IMAC
2.0
bo
1 1.5
C
0
c
0
U
0.5
0.0
Ln w 00 CD N � 00 o N �.D 00 a r �.D 00 o
M M o CS CS CD o r.� r.� r_� r.� r.� N r.l r l r l r l ro
Notes:
1. µg/L=rnicrograms. per liter
2.CottaItIMAC value=lµg/L Time (Years)
S. CobaIt PPK=25 µg/L
Figure 107 Predicted Cobalt in Monitoring Well A13-1S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Cobalt Concentration at AB-2S
2.5
—Existing Conditions
Cap -in -Place
2.0
— -Cobalt IMAC
1.5
to
0 1.0
-_- -f -_-
L
f.i
0.5
0.0
f I s ! II}
ed
e -Itt It
CD 00 CS N CD 00 Cy N s.D 00 CS N CD 00 Cy
cr) QS Cy C1 Cy C7 Cy r-I rl r-I r-I rl N N N N N C 1
rl rl N N N N N N N N N N N N N N N N
Notes:
1. µg/L=micrograrnsperliter
2.CobattIMAC ualue=1M/L Time (Years)
S. Coba It PPBC = 2.5 IYgf L
Figure 108 Predicted Cobalt in Monitoring Well AB-2S

6.0
5.0
I? KOM
1.0
Predicted Cobalt Concentration at GWA-1S
Existing Conditions
Cap -in -Place
— -Cobalt IMAC
0.0 -I-
Ln
La
am
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
cc o r � 00 o N � 00 ® N � 00 o
am CD CD o a CD rl r-I rl rl rl N N N N N m
rl N N N N N N N N N N N N N N N N
Motes:
1. µglL=rnlcrograrnsperliter
2. Cobalt IMAC va lue=1 µgJL
3. CobaItPPBC=2.5 pig{L
Time (Years)
Figure 109 Predicted Cobalt in Monitoring Well GWA-1S

9.0
8.0
7.0
6.0►
5.0
4.0
�o
Rl
L 3.0►
s.i
a 2.0
u
1.0
U.0
It It It
00 a N
a —I rl s *1 s'J
Notes_
1. µ /L=microgramsp•erliter
2. Coba It I MAC va Iu e=1 µg/L
9. CobaIt PPBC=2.5 µg/L
Predicted Cobalt Concentration at MW-65
c
N � co 0
Time (Years)
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
00 CD
N N N N N
Figure 110 Predicted Cobalt in Monitoring Well MW-6S

Notes:
1. pg/L = micrograms per liter
2. Cobalt IMAC value = 1 pg/L
3. Cobalt PPBC = 2.5 pg/L
_I
l9
N LEGEND
n Dry Cell
V
— pow <= 0.5
0.5 - 0.7
P 0.7 - 0,9
CI
0.9 - 1 (Standard)
0
r 1 -2.5 (Background
i Concentration)
x
2.5 - 4
m
`m
4-10.7
s
10.7 - 250
0
a 250 - 1,548
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
�Vj
E' u
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1.000
Feet
Figure 111 Initial (2015) Cobalt Concentrations in Shallow Groundwater Zone

Notes:
1. ug/L = micrograms per liter
2. Cobalt IMAC value = 1 pg/L
3. Cobalt PPBC = 2.5 pg/L
0
E
D
V
V
N LEGEND
n Dry Cell
V
- pow <= 0.5
0.5 - 0.7
P 0.7 - 0,9
CI
0 0.9 - 1 (Standard)
a
0
r 1 -2.5 (Background
i Concentration)
x
2.5 - 4
m
m
4 -10.7
s
10.7 - 250
0
a 250 - 1,548
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
? WITH DUKE ENERGY
PROPERTY BOUNDARY
0
2 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
A
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
0 500 1.000
Feet
Figure 112 Initial (2015) Cobalt Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Cobalt IMAC value = 1 pg/L
3. Cobalt PPBC = 2.5 pg/L
N LEGEND
n Dry Cell
V
- pow <= 0.5
a) 0.5 - 0.7
0.7 - 0,9
0.9 - 1 (Standard)
1 -2.5 (Background
Concentration)
2.5 - 4
4 -10.7
s
10.7 - 250
0
a 250 - 1,548
E — —
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
0
— — BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
A
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 113 Initial (2015) Cobalt Concentrations in Bedrock Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Cobalt IMAC value = 1 Ng/L
3. Cobalt PPBC = 2.5 Ng/L
cci
N
N
O
N LEGEND
m Dry Cell
N
<= 0.5
O
I
N 0.5 - 0.7
0.7 - 0.9
0.9 - 1 (Standard)
1 -2.5 (Background
Concentration)
2.5-4
E
4 - 10.7
lt7
4
10.7 - 250
0
a 250 - 1,548
m
E —
— DUKE ENERGY PROPERTY
c
BOUNDARY
N
ca
ASH BASIN WASTE
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
c
w
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
o
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
r�
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 114 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Cobalt IMAC value = 1 pg/L
3. Cobalt PPBC = 2.5 pg/L
E
N
N
l9
N
LEGEND
m
Dry Cell
N
O
<= 0.5
I
N
3
0.5 - 0.7
LL
0.7 - 0.9
�I
a
0.9 - 1 (Standard)
1 -2.5 (Background
a
Concentration)
m
2.5-4
E
4 - 10.7
lt7
10.7 - 250
4
0
a 250 - 1,548
E _
DUKE ENERGY PROPERTY
N
BOUNDARY
m
ASH BASIN WASTE
m
BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w
ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— —
BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 115 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Cobalt IMAC value = 1 pg/L
3. Cobalt PPBC = 2.5 Ng/L
l9
N LEGEND
n Dry Cell
V
pow <= 0.5
a) 0.5 - 0.7
0.7 - 0,9
0.9 - 1 (Standard)
1 -2.5 (Background
Concentration)
2.5 - 4
4 -10.7
s
10.7 - 250
0
a 250 - 1,548
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
t
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
i r N
100 0 500 1.000
116, Feet
Figure 116 Existing Conditions Scenario 1 - 2115 Predicted Cobalt Concentrations in Bedrock Groundwater Zone

Notes:
1. Ng/L =micrograms per liter
2. Cobalt IMAC value = 1 Ng/L
3. Cobalt PPBC = 2.5 Ng/L
N
N
l9
N
LEGEND
m
Dry Cell
N
O
<= 0.5
I
N
3
0.5 - 0.7
LL
0.7 - 0.9
I
r
a
0.9 - 1 (Standard)
1 -2.5 (Background
a
Concentration)
m
2.5-4
E
4 - 10.7
lt7
10.7 - 250
4
0
a 250 - 1,548
m
E — —
DUKE ENERGY PROPERTY
c
N
BOUNDARY
ca
ASH BASIN WASTE
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
c
w
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
o
WITH DUKE ENERGY
PROPERTY BOUNDARY
m
0
0.5 MILE OFFSET FROM ASH
— —
BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
u
0
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 117 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Shallow Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Cobalt ]MAC value = 1 pg/L
3. Cobalt PPBC = 2.5 Ng/L
0
E
D
V
V
N LEGEND
I
n Dry Cell
V
<= 0.5
I
N 0.5 - 0.7
3
P 0.7 - 0.9
I �
C
0 0.9 - 1 (Standard)
a
0
r 1 -2.5 (Background
�
1
i Concentration)
x
2.5-4
4 - 10.7
ro
s
'
4 10.7 - 250
0
a 250 - 1,548
E DUKE ENERGY PROPERTY
r
� BOUNDARY
N
m ASH BASIN WASTE
0 BOUNDARY
m
ASH BASIN COMPLIANCE
BOUNDARY
C
L ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
? — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
W., t. rm-,
N
A
0 500 1.000
Feet
Figure 118 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Cobalt IMAC value = 1 pg/L
3. Cobalt PPBC = 2.5 pg/L
N LEGEND
n Dry Cell
V
— pow <= 0.5
a) 0.5 - 0.7
0.7 - 0,9
0.9 - 1 (Standard)
1 -2.5 (Background
Concentration)
2.5 - 4
4 -10.7
s
10.7 - 250
0
a 250 - 1,548
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
A
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 119 Cap -in -Place Scenario 2 - 2115 Predicted Cobalt Concentrations in Bedrock Groundwater Zone

3.0
2.5
2.0
3 1.5
_
a
}, 1.0
f�
_
O
0.5
0.0
Predicted Hexavalent Chromium Concentration at AB-15
Ln 00 CD N
0) °) CD CD Q
Notes:
1. µgr`L=rnicrogramsper liter
2. Hexavalertchromium DHHSHSLvalue=0.47µgJL
3. HexavalentchromiumPH=2.9 M/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
— Existing Conditions
Cap -in -Place
-Chromium VI DHHS HSL
Ict It00 CD N kD 00 CD N � l0 CD
CD CD ,� �� ,� N N N N iq M
N N rq N N N N N N N N N N
Time (Years)
Figure 120 Predicted Hexavalent Chromium in Monitoring Well AB-1S

Predicted Hexavalent Chromium Concentration at AB-2S
10
2.5
2.0
0.0 1
00 CD N Kt
0' � 0 CD CD CD CD
Notes:
1. �kg.1L= micrograms perliter
2. HexavalentchromiumQHH5H5Lvalue=0.07µg/L
S. HexavalentchromiumPP&C=2.8 µg/L
Time (Years)
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
—Existing Conditions
Cap -in -Place
— -Chromium VI DHHS HSL
00 CD N � 00 CD
N N ry N N M
Figure 121 Predicted Hexavalent Chromium in Monitoring Well A13-2S

2.5
pro,
IN
0.0
Ln
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Hexavalent Chromium Concentration at GWA-1S
c`ta It �
rl N N N
N ates:
1. µg/L=rnicrogramsper liter
2. HexavalentrhromiumDHHSHSLvalue=0.07µg/L
3. HexavalentchramiurnPPBC=2.8 µg/L
Existing Conditions
—Cap-in-Place
— -Chromium VI DHHS HSL
— —
It
110
—
It
04
— —
It
0
—
I
N
— —
—
Et
I'D
— —
st
04
—
— —
—
—
g
CD
'
N
't
S.D
"t
00 G
CD
s-I
r-I
rf
s-I
s-I
N
N
N
N
N Cn
N
N
N
N
N
N
N
N
N
N
N
N N
Time (Years)
Figure 122 Predicted Hexavalent Chromium in Monitoring Well GWA-1S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Hexavalent Chromium Concentration at MW-65
3.0
2.5
PAI
tw
0
L
W 1.0
43
_
0
U
0.5
0.0
It It
00 CD N
rn C) o 0
N N
Motes:
1. µg/L=Microgramsper liter
2. HexavalerrtchromiumaHHSHSLvalue =0.07µg/L
S. H exavalent ch romiu m PPBC=2.8 µg/L
Time (Years)
Figure 123 Predicted Hexavalent Chromium in Monitoring Well MW-6S3

Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 pg/L
(L/
N
N
N LEGEND
CU
Dry Cell
N
of
<= 0.7 (Standard)
0.07 - 0.089
0.089 - 0.5
0.5 - 1.45
1.45 - 2.8 (Background
Concentration)
2.8 - 3.2
m
3.2 - 50
6 50 - 78
0
a 78 - 78A
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
N BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
uj ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
8 MODEL DOMAIN
L J11
V
H
r r r
0
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
2
N
A
0 500 1,000
Feet
Figure 124 Initial (2015) Hexavalent Chromium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 pg/L
ow
N
N
N LEGEND
CU
Dry Cell
N
0
<= 0.7 (Standard)
i
0.07 - 0.089
LL 0.089 - 0.5
�I
a
0.5 - 1.45
1.45 - 2.8 (Background
a Concentration)
2.8 - 3.2
m
L
3.2 - 50
6 50 - 78
0
a 78 - 78A
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
6 LANDFILL/STRUCTURAL FILL
BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
:'*,7
N
A
0 500 1.000
Feet
Figure 125 Initial (2015) Hexavalent Chromium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 Ng/L
IM
N LEGEND
a Dry Cell
V
�I
<= 0.7 (Standard)
0 0.07 - 0.089
0.089 - 0.5
0.5 - 1.45
1.45 - 2.8 (Background
Concentration)
2.8 - 3.2
3.2 - 50
U 50-78
0
a 78 - 78A
E — —
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
0
— — BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
A
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 126 Initial (2015) Hexavalent Chromium Concentrations in Bedrock Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 pg/L
N LEGEND
a Dry Cell
V
�I
<= 0.7 (Standard)
0.07 - 0.089
P 0.089 - 0.5
CI
0 0.5 - 1.45
a
c
r 1.45 - 2.8 (Background
i Concentration)
x
2.8 - 3.2
m
N 3.2 - 50
50 - 78
0
a 78 - 78A
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
2 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
BOUNDARY
N
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
0 500 1.000
5 �
Feet
Figure 127 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 Ng/L
N
N
l9
N LEGEND
CU
Dry Cell
N
<= 0.7 (Standard)
of
0.07 - 0.089
0.089 - 0.5
0.5 - 1.45
1.45 - 2.8 (Background
Concentration)
2.8 - 3.2
3.2 - 50
50 - 78
0
a 78 - 78A
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 128 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 Ng/L
If
N
l9
N LEGEND
CU
Dry Cell
N
0
<= 0.7 (Standard)
i
0.07 - 0.089
0.089 - 0.5
0.5 - 1.45
1.45 - 2.8 (Background
Concentration)
2.8 - 3.2
3.2 - 50
50 - 78
0
a 78 - 78A
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
N BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
uj ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
r MODEL DOMAIN
A
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 129 Existing Conditions Scenario 1 - 2115 Predicted Hexavalent Chromium Concentrations in Bedrock Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L {r, -
3. Hexavalent chromium PPBC I '
= 2.8 pg/L °--
CD
N
OI
l9
N LEGEND}
`°
Dry Cell
N
— 0.7 (Standard) p.
OI 'di'
0.07 - 0.089
LL 0.089 - 0.5 l
° 0.5 - 1.45 r
a
� 1.45 - 2.8 (Background \
Concentration)
2.8 - 3.2
m \
L
2 3.2 - 50
1
6 50 - 78 I
° a f � 7a - 7a.4
E DUKE ENERGY PROPERTY
BOUNDARY T- r
N
m ASH BASIN WASTE
N BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
uj ASH BASIN COMPLIANCE
°
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY t
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY J
8a I = MODEL DOMAIN
N
A
0 500 1,000
Feet
Figure 130 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in Shallow Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium (-
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 pg/L
� 8
0 �•_
l9
N LEGEND
CU
Dry Cell
N I
<= 0.7 (Standard)
of
0.07 - 0.089 I
LL 0.089 - 0.5 1 1
r� 1
a 0.5 - 1.45
1.45 - 2.8 (Background \
Concentration)
2.8 - 3.2
m
L
2 3.2 - 50
1
6 50-78 I
° a f � 7a - 7a.4
E — — DUKE ENERGY PROPERTY
BOUNDARY r
N 1 _
m ASH BASIN WASTE
N BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
uj ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE N
rn BOUNDARY h
o LANDFILL/STRUCTURAL FILL _ IF 'AT BOUNDARY 0 500 1,000
8a = MODEL DOMAIN EMNLiti 'may F
eet
., �.. _ i V a '. 7A'
Figure 131 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Hexavalent chromium
DHHS HSL value = 0.07 pg/L
3. Hexavalent chromium PPBC
= 2.8 pg/L
l9
N LEGEND
a Dry Cell
V
<= 0.7 (Standard)
DI
00.07 - 0.089
0.089 - 0.5
0.5 - 1.45
1.45 - 2.8 (Background
Concentration)
2.8 - 3.2
3.2 - 50
U 50-78
0
a 78 - 78A
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
0
— — BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
— BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 132 Cap -in -Place Scenario 2 - 2115 Predicted Hexavalent Chromium Concentrations in Bedrock Groundwater Zone

Predicted Selenium Concentration at AB -IS
25.0
NIXI;
15.0
C
0 10.0
4-0
M
L
Q�
U
Q
0 5.0
0.0 ¢¢ ¢ ¢¢ �}
0 0000 d r�J 000 r A b N lL1 0�0
M Ol d O G O 0 r-I . 4 —1 —4 —1 c A N r 4 N rV rn
rV N N N N N N N r 4 N
Notes:
1. µg/L = micrograms per liter
2. Selenium 2L Standard= 20 µg/L Time (Years)
3_ Selenium PPBC 10 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 133 Predicted Selenium in Monitoring Well A13-1S

Predicted Selenium Concentration at A13-2S
25.0
tills]
15.0
C
0 10.0
P
M
L-
Q�
U
Q
0 5.0
u
0.0
1D 0000 N 0�0 N lD 10�*o N 0O0
M M 4 O Q D Q —4 —4 N N N N N Cn
N N N N N N N N N N N N N N N
Notes:
1. µg/L = micrograms per liter Time (Years)
2. Selenium 2L Standard = 20 µg/L
3. Selenium PPBC 10 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 134 Predicted Selenium in Monitoring Well A13-2S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Selenium Concentration at GWA-1S
25.0
20.0 -
Existing Conditions
Cap -in -Place
15.0
J
—
-Selenium 2L
as
c
Ip
10.0 -
M
L
Q�
U
Q
5.0
0.0
-
k.D
¢¢
N l07 N
N
0000
d7 M
Oqo
0 Q Q Q Q . -I . 4 . -I I
000
. 1 N N
0Oq0
N N N M
I r1
N N N N N N N N N
N N N
N N N N
Notes:
1. µg/L = micrograms per liter
Time (Years)
2. Selenium
2L Standard = 20 µg/L
3. Selenium PPBC 10 µg/L
Figure 135 Predicted Selenium in Monitoring Well GWA-1S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
25.0
Predicted Selenium Concentration at MW-6S
20.0
Existing Conditions
15.0
-
Cap -in -Place
-Selenium 2L
ao
c
c
10.0
P
M
L
Q�
U
Q
u
5.0
0.0 —;
0 Co
000
000 17",
: 0�101
a) ❑l 0
O 0 O 0
N M
�-I -i N
N N N rV N N N N
N N N
CV N N N
Notes:
1. µg/L = micrograms per liter
Time (Years)
2. Selenium
2L Standard = 20 µg/L
3. Selenium PPBC 10 µg/L
Figure 136 Predicted Selenium in Monitoring Well MW-6S

Notes:
1. Ng/L = micrograms per liter
2. Selenium 2L Standard = 20 pg/L
3. Selenium PPBC 10 Ng/L
11
N LEGEND
n Dry Cell
07
I
1
0.7-1 �
P 1 - 10 (Background 1
i
CI Concentration)
10 - 20 (Standard) '
r
20 - 50
50 - 75
75-100
t
ro
s
4 100 - 250
0
a 250 - 308
DUKE ENERGY PROPERTY
BOUNDARY
dl s"
n ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
V
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
? — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL _ r
T BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 137 Initial (2015) Selenium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Selenium 21- Standard = 20 pg/Lr
3. Selenium PPBC 10 pg/L
N LEGEND
n Dry Cell
V
— 0.7
I
0.7-1
3
P 1 - 10 (Background
CI Concentration) 1
o 1
10 - 20 (Standard)
Y
1 20 - 50
x
50 - 75
m �
75-100
ro
s
4
100 - 250
0
a 250 - 308
m
E �
� DUKE ENERGY PROPERTY
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
L
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
2
0.5 MILE OFFSET FROM ASH
—
— BASIN COMPLIANCE
rn
BOUNDARY
-
LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1.000
Feet
Figure 138 Initial (2015) Selenium Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Selenium 2L Standard = 20 Ng/L
3. Selenium PPBC 10 Ng/L
N LEGEND
n Dry Cell
V
<= 0.7
I
0.7-1
3
P 1 - 10 (Background 1
CI Concentration)
0
10 - 20 (Standard)
_Y
i 20 - 50
50 - 75 I
m
75-100
ro
s
i
4
100 - 250
o A
a 250 - 308 `
1
m
E �
� DUKE ENERGY PROPERTY
BOUNDARY
N
m
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
2
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY -
LANDFILL/STRUCTURAL FILL
m
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
44P 1
.armor
N
A
0 500 1.000
Feet
Figure 139 Initial (2015) Selenium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Selenium 2L Standard = 20 pg/L
3. Selenium PPBC 10 pg/L
v
LEGEND
Dry Cell
c 07
0.7-1
1 - 10 (Background
Concentration)
10 - 20 (Standard)
20 - 50
50 - 75
75-100
4 100 - 250
0
a 250 - 308
E
_ DUKE ENERGY PROPERTY
BOUNDARY
0
ca ASH BASIN WASTE
BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
m BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 140 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in Shallow Groundwater Zone

Notes.
1. Ng/L = micrograms per liter
2. Selenium 2L Standard = 20 pg/L
3. Selenium PPBC 10 pg/L
k
E
cci
N
N
OI
N LEGEND
Dry Cell
N _
O
<- 0.7
I
2 0.7 - 1
1 - 10 (Background
Concentration)
0
10 - 20 (Standard)
a 20 - 50
50-75
m
L
2 75 - 100
"9
m 100 - 250
O
a 250 - 308
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
21
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
r
F
■
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
0 0.5 MILE OFFSET FROM ASH
c — — BASIN COMPLIANCE N
rn BOUNDARY " n
o LANDFILL/STRUCTURAL FILL N
m BOUNDARY 0 500 1.000
U
MODEL DOMAIN Feet
Figure 141 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Selenium 2L Standard = 20 pg/L
3. Selenium PPBC 10 pg/L
l9'
N LEGEND
n Dry Cell
V
<= 0.7
I
0.7-1
3
P 1 - 10 (Background
CI Concentration)
0
10 - 20 (Standard)
Y
1 20 - 50
x
50 - 75
m
ro
75-100
s
4
100 - 250
0
a 250 - 308
m
E �
� DUKE ENERGY PROPERTY
BOUNDARY
N
m
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L
0
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
-
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
ir — 7
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 142 Existing Conditions Scenario 1 - 2115 Predicted Selenium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Selenium 2L Standard = 20 pg/L
3. Selenium PPBC 10 pg/L
rig
W
N LEGEND
a Dry Cell
N _
`- 0.7
�I
0.7 - 1
P' 1 - 10 (Background
Ci Concentration)
0
10 - 20 (Standard)
_Y
T 20 - 50
x
50-75
m
`m
75 - 100
100 - 250
0
a 250 - 308
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
Er
BOUNDARY
C
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
I
N
r
0 500 1,000
Feet
Figure 143 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Selenium 2L Standard = 20 pg/L
3. Selenium PPBC 10 pg/L r
0
E
D
V
V
ml -
N LEGEND
a Dry Cell
V _
�- 0.7
DI
2 0.7 - 1
Q 1 - 10 (Background
Ci Concentration)
0
10 - 20 (Standard)
Y
i 20 - 50
t
m
50-75 '
m
75 - 100
100 - 250
0
a 250 - 308
E — —
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
Er
BOUNDARY
C
ASH BASIN COMPLIANCE
0
— — BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Lj
a 4 ; ..�• � .ar�hor
.. N
0 500 1.000
Feet
Figure 144 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Selenium 2L Standard = 20 pg/L
3. Selenium PPBC 10 pg/L
N
LEGEND
n
Dry Cell
4
<= 0.7
P
3
0.7-1
P
i
1 - 10 (Background
Concentration)
CI
0
10 - 20 (Standard)
Y
20 - 50
x
m
50 - 75
ro
75-100
s
100 - 250
4
0
a 250 - 308
m
E � �
DUKE ENERGY PROPERTY
N
BOUNDARY
n
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
m
2
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
ZLANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 145 Cap -in -Place Scenario 2 - 2115 Predicted Selenium Concentrations in Bedrock Groundwater Zone

300,000
250,000
200,000
bio
0
Iz
M 150,000
C
ry
U
C
U 100,000
50,000
0
lD 00
C') 0')
Notes:
1. µg/L = micrograms per liter
2. Sulfate 2L Standard = 250,000 µg/L
3. Sulfate PPBC = 1,460 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Sulfate Concentration at AB -IS
8 N 3� 8 N 4 1 8 N 3
O O O O O N N N N
N N r4 N N N N N N N N N N N
Time (Years)
Figure 146 Predicted Sulfate in Monitoring Well ABAS

3 00, 000
250,000
200,000
bD
C
0
150,000
C
C
0 100,000
t F�f
0
Ln I:t
l0 00
C)') CY)
c-I c-I
Notes:
1. µg/L = micrograms per liter
2. Sulfate 2L Standard = 250,000 µg/L
3. Sulfate PPBC = 1,460 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Sulfate Concentration at A13-2S
N 00 U N 00 N
0 p 0 O 0 —4 .--1 .--I .--I .--I N N rI4 r4
r'J r4 N N N N fV N N N N N fV N
Time (Years)
Figure 147 Predicted Sulfate in Monitoring Well A13-2S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Sulfate Concentration at GWA-1S
300,000
250,000 -
Existing Conditions
Cap -in -Place
200,000
3
— -Sulfate 2L
c
0
150,000
M
c
a)
U
c
100,000
u°
50,000
0Ln
0 00
¢¢ 1070, r l 0�0
¢¢
N lD
G)
O O O O O .4 r-I r-I r-I
N N N N
c-I c-I
N N N N N N N N N rV
N N N N
Notes:
1. µg/L = micrograms per liter
(Years)
Time (nears)
2. Sulfate
2L Standard = 250,000 µg/L
3. Sulfate PPBC = 1,460 µg/L
Figure 148 Predicted Sulfate in Monitoring Well GWA-1S

250,000
J
200,000
r_
C
M 150,000
L.
C
dm
c�
C
0 100,000
5 0, 000
0
LD 00
C II 0)
c-I c-I
Notes:
1. µg/L = micrograms per liter
2. Sulfate 2L Standard = 250,000 µg/L
3. Sulfate PPBC = 1,460 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Sulfate Concentration at MW-6S
N 00 N Co N Cr
O O O O O —4 1-I —4 —4 N N N cv
N N rJ N N N N N N N N N N N
Time (Years)
Figure 149 Predicted Sulfate in Monitoring Well MW-6S

Notes: — —
1. pg/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L - +
3. Sulfate PPBC = 1,460 pg/L
LEGEND
a`) Dry Cell
2
ff — 970
0
-) , 970- 1,460 (Background
Concentration)
N
1,460 - 2,100
lil 2,100 - 10,000
x
10,000 - 30,300
m
v 30,300 - 31,000
N 31,000-250,000
0 (Standard)
0
250,000 - 1,000,000
c 1,000,000 - 7,700,267
'm
m
n _ DUKE ENERGY PROPERTY
C �
3 BOUNDARY
rn ASH BASIN WASTE
BOUNDARY
L
r ASH BASIN COMPLIANCE
BOUNDARY
u ASH BASIN COMPLIANCE
o _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
N PROPERTY BOUNDARY
LANDFILL/STRUCTURAL
FILL BOUNDARY
N
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
��.An
N
A
0 500 1,000
Feet
Figure 150 Initial (2015) Sulfate Concentrations in Shallow Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. Ng/L. = micrograms per liter
2. Sulfate 2L Standard =
r-7
250,000 pg/L
3. Sulfate PPBC = 1,460 pg/L A z
LEGEND
u Dry Cell
— 970
0
�I F 970 - 1,460 (Background
Concentration)
N
1,460 - 2,100
iil 2,100 - 10,000
x
10,000 - 30,300
m
30,300 - 31,000
N 31,000-250,000
o (Standard)
0
250,000 - 1,000,000
'm
-i 1,000,000 - 7,700,267
m
n _ DUKE ENERGY PROPERTY
C �
3 BOUNDARY
rn ASH BASIN WASTE
BOUNDARY
L
r ASH BASIN COMPLIANCE
BOUNDARY
u ASH BASIN COMPLIANCE
o BOUNDARY COINCIDENT
WITH DUKE ENERGY
N PROPERTY BOUNDARY
rn
LANDFILL/STRUCTURAL
N
FILL BOUNDARY
MODEL DOMAIN
N
A
0 500 1,000
Feet
Figure 151 Initial (2015) Sulfate Concentrations in Deep Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L
3. Sulfate PPBC = 1,460 pg/L
x
E
a � I
C
0 LEGEND
n dry Cell
r �= 970
01 970- 1,460 (Background 1
t Concentration)
ca 1,460 - 2,100
0-
1 2,100 - 10,000
U 10,000 - 30,300
m
E2 30,300 - 31,000 ,
ro
31,000-250,000
o (Standard)
a 250,000 - 1,000,000
E
c 1,000,000 - 7,700,267
N - "
m _ DUKE ENERGY PROPERTY
L �
BOUNDARY
m ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
3 BOUNDARY
a
ASH BASIN COMPLIANCE
° _ BOUNDARY COINCIDENT
2 WITH DUKE ENERGY N
rn PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
m FILL BOUNDARY 1 0 500 1,000
ca MODEL DOMAIN Feet
Figure 152 Initial (2015) Sulfate Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L
3. Sulfate PPBC = 1,460 pg/L
LEGEND
a`) Dry Cell
2
ff — 970
0
-) , 970- 1,460 (Background
N I concentration)
1,460 - 2,100
Lil
2,100 - 10,000
10,000 - 30,300
m
30,300 - 31,000
N 31,000-250,000
0 (Standard)
0
a 250,000 - 1,000,000
c 1,000,000 - 7,700,267
ro
n _ DUKE ENERGY PROPERTY
C �
3 BOUNDARY
rn ASH BASIN WASTE
BOUNDARY
L
r ASH BASIN COMPLIANCE
BOUNDARY
u ASH BASIN COMPLIANCE
o _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
N PROPERTY BOUNDARY
LANDFILL/STRUCTURAL
FILL BOUNDARY
N
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
��.An
N
A
0 500 1,000
J �
Feet
Figure 153 Existing Conditions Scenario 1 - 2115 Predicted Sulfate Concentrations in Shallow Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L �=
3. Sulfate PPBC = 1,460 pg/L
ter,.-t
J
N
LEGEND
i
u Dry Cell"
off — 970 j
01 970- 1,460 (Background Il
-61 Concentration) e
2F 1,460 - 2,100biw
1 ��
ai 2,100 - 10,000
10,000 - 30,300
N 30,300 - 31,000
m
31,000-250,000
o (Standard) rMfg
I 250,000 - 1,000,000
E�
'c 1,000,000 - 7,700,267
N
[� 4 t-
m DUKE ENERGY PROPERTY
m
BOUNDARY
S
rn ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
o BOUNDARY
u ASH BASIN COMPLIANCEIN
_ BOUNDARY COINCIDENT
ram` WITH DUKE ENERGY
IN
PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
m FILL BOUNDARY
_
0 500 1,000
Ca MODEL DOMAIN
Feet
Figure 154 Existing Condition Scenario 1 - 2115 Predicted Sulfate Concentrations in Deep Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. Ng/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L 4 `
3. Sulfate PPBC = 1,460 pg/L t -
E I �,
C
0 LEGEND
n dry Cell
c — 970 _.
0
01 970- 1,460 (Background
t Concentration)
P
ca 1,460 - 2,100
a� 2,100 - 10,000
U 10,000 - 30,300
m
E2 30,300 - 31,000 ,
ro
31,000-250,000
o (Standard)
a 250,000 - 1,000,000
E
c 1,000,000 - 7,700,267
N ..
m _ DUKE ENERGY PROPERTY
L �
BOUNDARY
m ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
3 BOUNDARY
a
ASH BASIN COMPLIANCE
° _ BOUNDARY COINCIDENT
2 WITH DUKE ENERGY N
rn PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
m FILL BOUNDARY 1 0 500 1,000
ca MODEL DOMAIN Feet
Figure 155 Existing Conditions Scenario 1 - 2115 Predicted Sulfate Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L
3. Sulfate PPBC = 1,460 pg/L
LEGEND
Dry Cell
— 970
�i 970 - 1,460 (Background
Concentration)
N
1,460 - 2,100
ii 2,100 - 10,000
z
10,000 - 30,300
30,300 - 31,000
s 31,000-250,000
o (Standard)
c 250,000 - 1,000,000
E
- 1,000,000 - 7,700,267
N
ro
n _ _ DUKE ENERGY PROPERTY
BOUNDARY
rn _ ASH BASIN WASTE
BOUNDARY
L
z ASH BASIN COMPLIANCE
BOUNDARY
ASH BASIN COMPLIANCE
o _ _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
w PROPERTY BOUNDARY
LANDFILL/STRUCTURAL
Z FILL BOUNDARY
MODEL DOMAIN
1
r�
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
0 500 1,000
*.' + Feet
Figure 156 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L
3. Sulfate PPBC = 1,460 pg/L
C
LEGEND
Dry Cell
— 970
U 970 - 1,460 (Background
L Concentration)
1,460 - 2,100
ai 2,100 - 10,000
10,000 - 30,300
N 30,300 - 31,000
caI
31,000-250,000
o (Standard)
250,000 - 1,000,000
E
1,000,000 - 7,700,267
N
ro
DUKE ENERGY PROPERTY
3 BOUNDARY
rn ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
o BOUNDARY
u ASH BASIN COMPLIANCE
o _ _ BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
z FILL BOUNDARY
P
MODEL DOMAIN
e
it
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 157 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Sulfate 2L Standard =
250,000 pg/L
3. Sulfate PPBC = 1,460 pg/L / v
LEGEND
U
Dry Cell
— 970
U 970 - 1,460 (Background
L Concentration)
1,460 - 2,100
ai 2,100 - 10,000
10,000 - 30,300
N 30,300 - 31,000
caI
31,000-250,000
o (Standard)
250,000 - 1,000,000
E
1,000,000 - 7,700,267
N
DUKE ENERGY PROPERTY
3 BOUNDARY
rn ASH BASIN WASTE
BOUNDARY
w
Y ASH BASIN COMPLIANCE
o BOUNDARY
u ASH BASIN COMPLIANCE
o — — BOUNDARY COINCIDENT
WITH DUKE ENERGY
w PROPERTY BOUNDARY
o LANDFILL/STRUCTURAL
z FILL BOUNDARY
P
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
IM N
0 500 1,000
Feet
Figure 158 Cap -in -Place Scenario 2 - 2115 Predicted Sulfate Concentrations in Bedrock Groundwater Zone

M.
0.4
J
bo 0.3
U 0'.1
0.0
L n 'St Et 'nt
CD 00 O N
M C) O O
r-I rl N N
Notes:
1. µgfL=mitrogramsper liter
2. Thallium IMACvalue=0.2ag/L
5. Thallium PPBC=0.5 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Thallium Concentration at AB-1S
LD 00 O N �T LD 00 CDN CT LD 00 O
Ca O O rl r- I r- I rl r—I N N N N N C1
N N N N N N N N N N N N N N
Time (Years)
Figure 159 Predicted Thallium in Monitoring Well A13-1S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Thallium Concentration at AB-2S
0.5
Existing Conditions
Cap -in -Place
0.4
-Thallium IMAC
0.3
J
t
CIC
0
0.2
Ip
M
L
Q�
U
©
0.1
-
u
0.0Ln
-
00
N 00 N 00 N
Cfl
4} M O
p p p Q -I •--I •--I •--I —4 N N
N N N Cr
N N N N N N
N N N N
Notes:
1.µg/L=
micrograms
per liter
Time (Years)
2. Thallium IMACvalue = 0.2 F[g/L
3_Thallium PPBC=0.5pg/L
Figure 160 Predicted Thallium in Monitoring Well A13-2S

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Thallium Concentration at G A-1S
0.
0.5
Existing Conditions
0.4
-
Cap -in -Place
—
-Thallium IMAC
b 0.3
0
0
c�
0.1
0. f' a
11t u
SD 00 Cr
e
N SD 00 0 N � s.D 00 Cr N
� S.D 00 O
M Oi Cr
r-I
C1 Cr Cr Cr rl rI rl rI rI N del
6� iti �1I
N N fV M
N ftil N N
Notes:
1. µafL=microgramsPer liter
Time (Years)
2. Thallium IMACvalue=0.2 µ /L
3. Thallium PPBC=0.5 µgfL
Figure 161 Predicted Thallium in Monitoring Well GWAAS

Predicted Thallium Concentration at MW-65
Imi
0.4
0.1
0.4
Lr) Itt It
�D 00 rq
M a-, CD o
r-I rl iJ r.l
Notes:
1. µgfL=microgramsper liter
2. Thallium IMAC ualue=0.2 µgf L
3_ Th a Ilium PPBC= 05 Ng/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
CD a CD r-1 r-� r-1 r-q r-q N N N N r.l m
rJ N r.l r � s *.l r.l nl rJ rJ rJ rJ rJ r� rJ
Time Years}
Figure 162 Predicted Thallium in Monitoring Well MW-6S

Notes:
1. Ng/L = micrograms per liter
2. Thallium IMAC value = 0.2 Ng/L
3. Thallium PPBC = 0.5 Ng/L
_I
N LEGEND
.01 Dry Cell
V1N <= 02 (Standard)
0.2 - 0.5 (Background
`
Concentration)
0.5-1
C
0
1-10
Y
T
10-20
x
20-30
m
30 - 40
ro
s
`
40 - 50
0
a 50 - 62
m
E —
— DUKE ENERGY PROPERTY
BOUNDARY
N
m
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
—
—
WITH DUKE ENERGY
PROPERTY BOUNDARY
m
0
0.5 MILE OFFSET FROM ASH
? — — BASIN COMPLIANCE
rn BOUNDARY
ZLANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 163 Initial (2015) Thallium Concentrations in Shallow Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Thallium IMAC value = 0.2 Ng/L
3. Thallium PPBC = 0.5 Ng/L
N I LEGEND
.01 Dry Cell
V1N <= 02 (Standard)
0.2 - 0.5 (Background
`
Concentration)
rn
it
05-1
C
0
1-10
_Y
T
10-20
x
20-30
m
30 - 40
ro
s
`
40 - 50
0
a 50 - 62
m
E �
� DUKE ENERGY PROPERTY
BOUNDARY
N
n
ASH BASIN WASTE
m
BOUNDARY
3
ASH BASIN COMPLIANCE
21
BOUNDARY
L
m
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
?
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
— — BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 164 Initial (2015) Thallium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Thallium IMAC value = 0.2 pg/L
3. Thallium PPBC = 0.5 pg/L
"r I -�
N
LEGEND
m
Dry Cell
N F�
0
<= 02 (Standard)
i
0.2 - 0.5 (Background
`—
rn
Concentration)
"I
05-1
r
1-10
10-20
=�
m
20-30
L
E
ro
30 - 40
40 - 50
`
0
a 50 - 62
E _
DUKE ENERGY PROPERTY
N
BOUNDARY
Co
ASH BASIN WASTE
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
w
0
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
o
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1,000
Feet
Figure 165 Initial (2015) Thallium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Thallium IMAC value = 0.2 Ng/L
3. Thallium PPBC = 0.5 Ng/L
N
O
N I LEGEND
€n I Dry Cell
NI
�' <= 02 (Standard)
0
0.2 - 0.5 (Background
Concentration)
L 0.5-1
r
1-10
10-20
=� 20-30
L
E 30 - 40
` 40 - 50
0
a 50 - 62
m
E � � DUKE ENERGY PROPERTY
c BOUNDARY
N
Co ASH BASIN WASTE
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENI
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM /
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL
N BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 166 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Shallow Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L
2. = micrograms per liter
Thallium IMAC value = 0.2 Ng/L
3. Thallium PPBC = 0.5 Ng/L
_.r 1 I 4
k -
E �
N
O
_I
m
N LEGEND
c2 Dry Cell
N
0
� <= 02 (Standard)
i
0.2 - 0.5 (Background r
rn
Concentration)
LLI 0.5 - 1"'�`
r
� 1-10 1
10-20
¢ {l
=� 20-30
E
L
30 - 40
ro
0 ` 40 - 50
0
a 50 - 62
E DUKE ENERGY PROPERTY `
BOUNDARY Y
N
m ASH BASIN WASTE
m BOUNDARY
ASH BASIN COMPLIANCE
El
BOUNDARY
w ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
c — — BASIN COMPLIANCE N
rn BOUNDARY n
o LANDFILL/STRUCTURAL FILL
N BOUNDARY ` 0 500 1,000
U
MODEL DOMAIN Feet
Figure 167 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Deep Groundwater Zone

Notes:
1Ng/L = micrograms per liter
iThallium IMAC value = 0.2 Ng/L
3. Thallium PPBC = 0.5 pg/L
D
V
LEGEND
s
.01 Dry Cell
<= 02 (Standard)
0.2 - 0.5 (Background
` Concentration)
rn
li 05-1
C
0
1-10
Y_
i 10-20
2
m
20-30
C
30 - 40
�i 40 - 50
0
a 50 - 62
m
E � � DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L ASH BASIN COMPLIANCE
v
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILLfSTRUCTURAL FILL
N
BOUNDARY
U
N MODEL DOMAIN
y
i—r
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1,000
Feet
Figure 168 Existing Conditions Scenario 1 - 2115 Predicted Thallium Concentrations in Bedrock Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Notes:
1. pg/L
2. =micrograms per liter
Thalliu
3. Thallium IMAC value = 0.2 pg/L
m PPBC = 0.5 pg/L j
V li
] it
l9
N LEGEND
n Dry Cell
V <= 02 (Standard)
i
V) 0.2 - 0.5 (Background
` Concentration)
C 0.5-1
o
Y 1 _ 10
i 10-20
20-30�
30 - 40
s
` 40 - 50
o
a � 50 - 62
m
E � � DUKE ENERGY PROPERTY
BOUNDARY '
N
m ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT}
WITH DUKE ENERGY
V
PROPERTY BOUNDARY
N
2 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE N
rn BOUNDARY n
D LANDFILL/STRUCTURAL FILL
N BOUNDARY r 0 500 1,000
U
MODEL DOMAIN l � � Feet
Figure 169 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Thallium IMAC value = 0.2 pg/L
3. Thallium PPBC = 0.5 pg/L
f
N I LEGEND
.01 Dry Cell
141 N <= 02 (Standard)
0.2 - 0.5 (Background
`
Concentration)
rn
CI
05-1
0
1-10
Y
T
10-20
x
20-30
m
30 - 40
ro
s
`
40 - 50
0
a 50 - 62
DUKE ENERGY PROPERTY
BOUNDARY
n
ASH BASIN WASTE
m
BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
li
0
ASH BASIN COMPLIANCE
BOUND ARYCOINCIDENT
WITH DUKE ENERGY
E2
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
? — BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N BOUNDARY
MODEL DOMAIN
Y � �
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
r
N
A
0 500 1,000
Feet
Figure 170 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Deep Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Thallium IMAC value = 0.2 pg/L
3. Thallium PPBC = 0.5 Ng/L
V
V
N
LEGEND
n
Dry Cell
V
<= 02 (Standard)
0.2 - 0.5 (Background
`
rn
Concentration)
CI
05-1
0
1-10
Y
T
10-20
x
m
20-30
ro
30 - 40
s
40 - 50
`
0
a 50 - 62
DUKE ENERGY PROPERTY
N
BOUNDARY
m
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
L
0
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
m
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
' ✓ A
N
A
0 500 1,000
Feet
Figure 171 Cap -in -Place Scenario 2 - 2115 Predicted Thallium Concentrations in Bedrock Groundwater Zone

Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Vanadium Concentration at AB-1S
4.5
4.0
3.5
3.0
—Existing Conditions
2.5
—Cap-in-Place
130
— -Vanadium IMAC
c 2.0
0
14
L.
1.5
0
c�
1=
1.0
0
05
. . . . . . . . . . . . . . . . . . . . .
0.0 1 — __T— ---T—
00 0 O N � 0 N � 0
cLn .D N spa o`t0 00 00
M M CD o 0 o CD r_� r_� r_� r_� r_� N N rU rq ro
T-1 T-1 r.l r l r� r l r.l r.J rJ r.J r.l r l r.l r.l r.l rJ r l r.l
Notes:
1. µg/L=microgramsper liter Time (Years)
Z. Vanadium IMAC walue=0.3 wjL
S. Vanadium PPBC=3.9 µ /L
Figure 172 Predicted Vanadium in Monitoring Well A13-1S

4.0
3.5
3.0
2.5
2.0
0.5
0.0
Predicted Vanadium Concentration at AB-25
.�t It �t
o
r-I r-I N N
Motes:
1. [ig/L=rnicrogramsper]ter
Z. Vanadium If41ACvaiue=4.3 µg/L
3. Vanadium PPBC= 3.IJ µgJL
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
G 0 o r-I r-� r-� "I r-I N N N N N ro
N N N N N N N N N N N N N N
Time (Years)
Figure 173 Predicted Vanadium in Monitoring Well AB-2S

Predicted Vanadium Concentration at GWA-IS
4.5
4.0
3.5
3.0
Q 2.0
0
Ip
1.5
0
a�
U
© 1.0
u
0.5
0.0 �} ¢
lD 00 N lD N 0�0 N l0 0
d3 M d O d O 0 N N N N N C+!
.--I —i N N N N N rV N N r4 N N N N N CV N
Notes:
1. µg/L = micrograms per liter Time (Years)
2. Vanadium IMAC value = 0.3 µg/L
3. Vanadium PPBC = 3.9 µg/L
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Figure 174 Predicted Vanadium in Monitoring Well GWA-1S

4,5
4.0
3,5
3.0
15
2.0
0
1.5
0 1,0
V
O' 5
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Predicted Vanadium Concentration at MW-6S
cccc o N It spa cc o N � cc o N spa cc 0
am 0 0 0 0 0 r-I r-I r-I r-I r-I N N N N N m
r-I N N rV N N N N N rV N N N N N N N
Notes:
1. µg/L=microgramsperliter Time (Years)
2. Vanadium I MAC va lu e = 0. 3 jjxJL
3. Vanadium PPBC= IS µg/L
Figure 175 Predicted Vanadium in Monitoring Well MW-6S

Notes:
1. pg/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 Ng/L
E
(6
N
N
N LEGEND
m`
Dry Cell
N
of
<= 0.3 (Standard)
0.3 - 1
Q 1 -3.9 (Background
rConcentration)
3.9-5
5 - 8.8
m
8.8 - 25
L
E 25 - 150
lSl
m 150 - 300
O
a 300 - 444
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
N BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
C
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
6 I LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
,+N
6
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
� J
N
A
0 500 1.000
Feet
Figure 176 Initial (2015) Vanadium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 pg/L
E
cci
N
N
l9
N LEGEND
Ca
Dry Cell
N
<= 0.3 (Standard)
0
i
P 0.3 - 1
Q 1 -3.9 (Background
rConcentration)
0
3.9-5
a 5 - 8.8
m
8.8 - 25
L
E 25 - 150
lSl
m ICI 150 - 300
O
a 300 - 444
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
6 LANDFILL/STRUCTURAL FILL
N BOUNDARY
8 MODEL DOMAIN
I
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
� = J
N
A
0 500 1.000
Figure 177 Initial (2015) Vanadium Concentrations in Deep Groundwater Zone
Feet

Notes:
1. Ng/L = micrograms per liter
2. Vanadium IMAC value = 0.3 Ng/L
3. Vanadium PPBC = 3.9 Ng/L
N LEGEND
n Dry Cell
V
<= 0.3 (Standard)
i
0.3-1
P 1 -3.9 (Background
CI Concentration)
r 3.9-5 1
T 5 - 8.8 {1
x
8.8 - 25
N 25 - 150
ro
s
`
150 - 300
0
a 300 - 444
m
E �
� DUKE ENERGY PROPERTY
BOUNDARY
N
m
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L
0
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
-
LANDFILL/STRUCTURAL FILL
m
BOUNDARY
7�
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 178 Initial (2015) Vanadium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 Ng/L
E
(6
N
N
O
N LEGEND
Ca
Dry Cell
N
0
<= 0.3 (Standard)
i
0.3 - 1
1 -3.9 (Background
r Concentration)
3.9-5
a 5 - 8.8
m
8.8 - 25
L
E 25 - 150
lSl
m ICI 150 - 300
O
a 300 - 444
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
N BOUNDARY
ASH BASIN COMPLIANCE
BOUNDARY
C
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
o WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
6 I LANDFILL/STRUCTURAL FILL
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 179 Existing Conditions Scenario 1 - 2115 Predicted Vanadium Concentrations in Shallow Groundwater Zone

Notes:
1. Ng/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 Ng/L
l9
N LEGEND
Ca
Dry Cell
N
0
<= 0.3 (Standard)
i
P 0.3 - 1
Q 1 -3.9 (Background
rConcentration)
0
3.9-5
a 5 - 8.8
m
8.8 - 25
L
E 25 - 150
lSl
m 150 - 300
O
a 300 - 444
DUKE ENERGY PROPERTY
BOUNDARY
N
m ASH BASIN WASTE
m BOUNDARY
S
ASH BASIN COMPLIANCE
BOUNDARY
c
w ASH BASIN COMPLIANCE
m
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
6 LANDFILL/STRUCTURAL FILL
BOUNDARY
8 MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
al I
N
A
0 500 1.000
Feet
Figure 180 Existing Conditions Scenario 1 - 2115 Predicted Vanadium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 pg/L
l9'
N LEGEND
e
n Dry Cell
V
<= 0.3 (Standard)
i
0.3-1
P 1 -3.9 (Background
CI Concentration)
r 3.9-5 � 1
T 5 - 8.8 {1
x
8.8 - 25
m
25 - 150
ro
s
`
150 - 300
0
a 300 - 444
m
E �
� DUKE ENERGY PROPERTY
BOUNDARY
N
m
ASH BASIN WASTE
BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
L
0
ASH BASIN COMPLIANCE
BOUNDARY COINCIDENT
WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn
BOUNDARY
-
D
LANDFILL/STRUCTURAL FILL
m
BOUNDARY
7�
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 181 Existing Conditionsc Scenario 1 - 2115 Predicted Vanadium Concentrations in Bedrock Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 Ng/L
0 7
.6
V
V 1
l9
N LEGEND
I
n Dry Cell y
V 4
<= 0.3 (Standard)
U)
0.3 - 1
Q 1 -3.9 (Background
Ci Concentration)
r 3.9-5 t
i 5 - 8.8
t
m
8.8 - 25
25 - 150 �rw
m
s
ICI 150 - 300
0
a 300 - 444
E _ DUKE ENERGY PROPERTY `
BOUNDARY
N
n ASH BASIN WASTE
m BOUNDARY
3
ASH BASIN COMPLIANCE
Er
BOUNDARY
ASH BASIN COMPLIANCE
Y
BOUNDARY COINCIDENT
D WITH DUKE ENERGY _
PROPERTY BOUNDARY
2 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
Few
N
A
0 500 1.000
Feet
Figure 182 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Shallow Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 Ng/L
_I
l9
LEGEND
n Dry Cell
V
<= 0.3 (Standard)
0.3 - 1 I
Q 1 -3.9 (Background ;
ci Concentration) }
0
3.9-5
Y
i 5 - 8.8
t
m
8.8 - 25
m
25 - 150
ICI 150 - 300
0
a 300 - 444
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
1
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 183 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Deep Groundwater Zone

Notes:
1. pg/L = micrograms per liter
2. Vanadium IMAC value = 0.3 pg/L
3. Vanadium PPBC = 3.9 Ng/L
E
D
V
l9
N LEGEND
n Dry Cell
V
<= 0.3 (Standard)
i
0.3 - 1
Q 1 -3.9 (Background
ci Concentration)
0
3.9-5
_Y
i 5 - 8.8
t
m
8.8 - 25
m
25 - 150
ICI 150 - 300
0
a 300 - 444
E
DUKE ENERGY PROPERTY
BOUNDARY
N
n ASH BASIN WASTE
N BOUNDARY
3
ASH BASIN COMPLIANCE
BOUNDARY
C
ASH BASIN COMPLIANCE
0
BOUNDARY COINCIDENT
D WITH DUKE ENERGY
PROPERTY BOUNDARY
0
0 0.5 MILE OFFSET FROM ASH
BASIN COMPLIANCE
rn BOUNDARY
D LANDFILL/STRUCTURAL FILL
N
BOUNDARY
MODEL DOMAIN
I
,99
1
t
Groundwater Flow and Transport Model
Marshall Steam Station Ash Basin
N
A
0 500 1.000
Feet
Figure 184 Cap -in -Place Scenario 2 - 2115 Predicted Vanadium Concentrations in Bedrock Groundwater Zone