2014-11-26 Comments on GW Assessment Work Plans

SOUTHERN ENVIRONMENTAL LAW CENTER
Telephone [phone] WEST ROSEMARY STREET, SUITE 220 Facsimile 919-929-9421
CHAPEL HILL, NC 27516-2356
November 26, 2014
VIA EMAIL AND U.S. MAIL
Mr. Tom Reeder, Director
N.C. DENR, Division of Water Resources
1601 Mail Service Center
Raleigh, NC 27699-1601
[e-mail]
Re: Duke Energy Groundwater Assessment Work Plans and Drinking Water Supply
Well and Receptor Surveys
Dear Mr. Reeder:
The Southern Environmental Law Center, on behalf of itself and its conservation
organization clients in the coal ash enforcement actions filed by DENR against Duke Energy,
submits the following comments and observations on the Proposed Groundwater Assessment
Work Plans and Drinking Water Supply Well and Receptor Surveys submitted by Duke Energy
in September 2014.
General Comments
DENR sent Duke Energy a series of letters earlier this month requiring revisions to
Duke's Groundwater Assessment Work Plans. These letters identified some of the serious
deficiencies of Duke Energy's proposals and mandated a more rigorous approach. In addition,
DENR should require Duke Energy to correct the following significant problems common to all
the September 2014 groundwater assessment work plan proposals and receptor surveys
submitted by Duke Energy:
Assessments must identify the relative position of the bottom of ash and the water
table
The relative positions of the deepest disposed ash and the water table must be
determined. Duke must verify through review of construction records or pre -
development topography where the lowest elevation ash is expected to be located in each
ash basin or storage area. At least one boring in each ash basin and storage area must be
advanced at the location expected to be located above the lowest point of disposed ash
within each. Identification of the relative positions of the bottom elevation of disposed
ash and the underlying water table is critical in evaluating the effectiveness of possible
closure scenarios.
Charlottesville • Chapel Hill • Atlanta • Asheville • Birmingham • Charleston • Nashville • Richmond • Washington, DC

Need for monitoring wells at or near the base of ash
The work plans generally call for water table and deep (bedrock) monitoring wells to be
constructed within ash landfills and basins to characterize pore water chemistry within
the ash. Samples of pore water within the waste, at or near the bottom of each ash basin
and storage area, are critically needed to characterize the concentration of ash -related
constituents in leachate that is migrating from the facility. Leachate concentrations in ash
storage areas and basins typically increase with depth. Leachate at or near the bottom of
the impoundment or landfill has migrated through the waste column and has had
sufficient contact time to come into chemical equilibrium with the waste matrix. The
chemical composition of leachate collected from the bottom of the ash basins and storage
areas will more realistically represent the chemistry of leachate that is leaving the units to
migrate with groundwater and must be used in developing the source term for input to the
groundwater model. While useful for evaluating the water table elevation within the ash,
water table wells will not provide the source concentration information needed to
adequately model migration of contaminants from the site. In an ash basin, the
concentration of ash -related constituents at the water table will more closely resemble the
chemistry of water discharged through the NPDES permitted outfall than the chemistry of
groundwater that is likely to migrate out of the facility and into groundwater.
Site -Specific Background Concentrations
The work plans should be modified to require evaluation of the validity of background
groundwater monitoring locations and what the unimpacted background concentration
should be. This evaluation should consider more than the relationship between
groundwater standard exceedances and turbidity, or argue that high concentration of ash -
related constituents are naturally occurring in the groundwater. It should investigate
whether historic high ash basin water levels may have provided sufficient hydraulic head
to reverse gradients and drive flow away from the impoundments in the previously
upgradient direction. If water in the impoundments is or was sufficiently high to reverse
natural gradients, the previous and planned sampling could be detecting ash -related
contaminants that are or were migrating in what would be expected to be upgradient
under natural conditions. The groundwater model can be used to investigate groundwater
flow and contaminant distribution under high pond water conditions. Use of impacted
analyses from wells erroneously assumed to represent background conditions would skew
subsequent statistical evaluations.
Groundwater Modeling
Each of the assessment work plans indicate that Synthetic Precipitation Leaching
Procedure (SPLP) testing will be conducted on ash samples to evaluate leaching
potential. Work plans produced by HDR specifically state that results of these tests will
be used to determine the source term for groundwater modeling. Work plans produced
by Synterra do not specify the intended use, but deriving the source term for modeling the
site is the most obvious choice.
Application of short duration, low solid -ratio (dilute) leaching tests like the SPLP test
routinely underestimate the concentration of contaminants in flyash-derived
leachates. The procedure does not allow ash constituents sufficient time to come into

equilibrium with the fluid, the solid -water ratio is far more dilute than under disposal
conditions, and the laboratory conditions do not represent the disposal conditions under
which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings. These tests were not designed or intended to
represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by installing and sampling
monitoring points at the base of the disposed ash to produce site-specific leachate source
concentrations.
Little discussion is provided in any of the work plans that describe how the models will
be used. When completed, the groundwater model should be used to investigate changes
to hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Report Contents
At least one geologic cross-section should pass through the deepest area of each of the
ash basins and storage areas to evaluate the relative positions of the bottom of the ash and
the water table. The cross-sections must include identification of leachate and
groundwater levels within and underlying the ash.
Drinking Water Well Surveys
Each of the surveys used current well water levels and site topography to develop maps
that show areas described as the Area of Potential Concern or Potential Area of
Interest. These areas are locations where preliminary analysis shows the potential for
groundwater impacts outside of the compliance boundary and do not include the potential
for pumping of the supply wells to draw contaminants even further toward the
wells. Because of these limitations, the areas should be considered preliminary and are
subject to modification as additional data are developed.
There are five plants that appear to have a greater than normal potential for offsite
exposures. The well surveys around the Allen, Belews Creek, Buck, Marshall, and
Sutton plants all show wells within or very near the area of interest. DENR should take
an aggressive stance on determining if water produced from wells within or very near the
areas of concern is safe for consumption. Wells in or very near these areas should be
sampled quickly in order to minimize potential exposure of the public.
Groundwater Assessment Work Plan Comments
The following are site-specific comments on the Groundwater Assessment Work Plans
submitted by Duke Energy that must be addressed in order to ensure the assessments are valid.

Our comments and observations are referenced to the specific sections of the reports that discuss
identified issues.
Cape Fear
Section 1.0, Page 1- Introduction — The text indicates that monitoring wells BGMW-4
and BGTMW-4 are considered to be background monitoring wells. This designation must
be tested before it may be taken as fact. The location of these two wells across Shaddox
Creek from the plant and downgradient of a nearby wood panel manufacturing facility
makes it likely that these wells represent downgradient water quality that is migrating
from the impoundments on the adjacent facilities rather than unimpacted water quality
representative of background conditions at the Cape Fear plant. The need for careful
evaluation of background conditions is especially important since the work plan indicates
that the wells have shown exceedances of water quality standards. Groundwater quality
data from wells potentially impacted by an off-site source should not be used to measure
unimpacted background water quality. Section 7.4.2 of the work plan should either be
modified to evaluate the validity of background groundwater monitoring locations or the
document should be modified to indicate that new background monitoring locations will
be established and the existing wells will not be used in statistical evaluations.
2. Section 1.0, Page 2 — Introduction — One of the primary goals of conducting the
groundwater assessment must be to identify the relative positions of the bottom elevation
of disposed ash and the underlying water table. Identification of the relative positions of
the bottom of disposed ash and the water table in each ash basin or storage area will have
a significant impact on the potential effectiveness of various closure scenarios.
3. Section 2.2, Page 3 — Ash Basins — The description of the ash basins indicates that at
least two of the basins currently retain water. The elevation of ponded water in the
impoundments must be identified. The proposed groundwater assessment must be
capable of determining if surface runoff is actually being retained in the ash basins or if
water in the impoundments represents the elevation of the water table at those locations.
4. Section 2.3, Page 4 — Groundwater Monitoring System — Monitoring wells located
across Shaddox Creek from the Cape Fear facility cannot represent background
groundwater quality on the site, especially since the existing wells are located
downgradient of another potential source of contaminants. Delete all references to these
wells as background monitoring points.
5. Section 5.0, Page 10 — Site Geology and Hydrogeology — The discussion of
groundwater gradients does not reflect the influence of ash basin water on groundwater
flow direction in the proximity of the basins. Infiltration of water from the
impoundments and into the groundwater likely created mounding in the area creating
radial flow away from the impoundments in all directions. The elevation of groundwater
in each impoundment must be established in order to establish whether mounding of
groundwater within and below the impoundment persists even though plant operations
have ceased.
2

6. Section 6.1, Page 11— Preliminary Statistical Evaluation — The inter -well statistical
evaluation discussed in this section compares concentrations of ash -related constituents in
compliance wells to concentrations measured in existing "background" wells. As was
previously discussed, the existing wells currently identified as background are
inappropriately located across Shaddox Creek and downgradient of an adjacent industrial
facility. Comparisons to these wells are not likely to represent comparison to true
background.
7. Section 7.1., Page 13 - Anticipated Ash Basin Boring Locations — Please verify
through review of construction records or pre -development topography where the lowest
elevation ash is expected to be located in each ash basin or storage area. At least one of
the borings in each ash basin and storage area must be advanced at the location expected
to be located above the lowest point of disposed ash within each. Identification of the
relative positions of the bottom elevation of disposed ash and the underlying water table
is critical in evaluating the effectiveness of possible closure scenarios.
8. Section 7.1., Page 13 - Anticipated Ash Basin Boring Locations — The discussion in
this section and Table 3 each indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples. The intended use of these samples is
not clear from the discussion but it must be made clear from the onset that SPLP results
cannot be used to approximate the source term for ash basin leachate concentrations in
the groundwater model. Application of short duration, low solid -ratio (dilute) leaching
tests like the SPLP test routinely underestimate the concentration of contaminants in
flyash-derived leachates. The procedure does not allow ash constituents sufficient time
to come into equilibrium with the fluid, the solid -water ratio is far more dilute than under
disposal conditions, and the laboratory conditions do not represent the disposal conditions
under which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings'. These tests were not designed or intended to
represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by measuring ash pore water
concentrations by installing and sampling monitoring wells set at the base of the disposed
ash. While useful for evaluating the water table elevation within the ash, water table
wells will not provide the source concentration information needed to adequately model
migration of contaminants from the site. In an ash basin the concentration of ash -related
constituents at the water table will more closely resemble the chemistry of water
discharged through the NPDES permitted outfall than the chemistry of groundwater that
is likely to migrate out of the facility and into groundwater.
'National Research Council (NRC), 2006, Managing Coal Combustion Residues in Mines, by Committee on Mine
Placement of Coal Combustion Wastes, National Research Council of the National Academies, The National
Academies Press, Washington, D.C., 2006.
5

9. Section 7.2, Page 14 — Inside Ash Basins — The work plan should require that each of
the ash basin soil borings be completed as monitoring wells or piezometers. Completion
of the ash borings as piezometers would facilitate determination of the elevation of
groundwater below the impoundment at very little cost since the borehole will already be
present.
10. Section 7.3, Page 14 — Anticipated Sediment and Surface Water Locations — Prior to
initiating field work the existing seep sampling information should be reviewed to verify
that all identified seeps have been accurately located, the elevation of the seep has been
determined, and that analytical data include all parameters required by the work plan for
groundwater samples. In the event that all of these pieces of information do not exist, the
seeps should be sampled as part of this investigation.
11. Section 7.4.2, Page 16 — Background Wells — The fact that the existing "background
wells" identified in the work plan (BGMW-4 and BGTMW-4) are located across
Shaddox Creek from the plant and downgradient of a nearby wood panel manufacturing
facility makes it likely that these wells represent downgradient water quality that is
migrating from the impoundments on the adjacent facilities rather than unimpacted water
quality representative of background conditions at the Cape Fear plant. Only the
proposed background monitoring wells should be included in the background data set and
used for statistical comparison to other monitoring locations. Even the new wells should
be evaluated before this designation may be taken as fact.
12. Section 7.4.3, Page 16 — Ash Basins — The work plan indicates that previous assessment
activities at the plant have included installation of monitoring wells and piezometers
within the ash basins and references Figure 4. It is unclear after reviewing Figure 4 if or
where existing monitoring wells or piezometers within the basins are located. Wells
screened within the waste, at or near the bottom of each ash basin and storage area, are
critically needed to characterize the concentration of ash -related constituents in leachate
that is migrating from the facility. Leachate concentrations in ash storage areas and
basins typically increase with depth. Leachate at or near the bottom of the impoundment
or landfill has migrated through the waste column and had sufficient contact time to come
into chemical equilibrium with the waste matrix. The chemical composition of leachate
collected from the bottom of the ash basins and storage areas will more realistically
represent the chemistry of leachate that is leaving the units to migrate with groundwater
and must be used in developing the source term for input to the groundwater model.
While useful for evaluating the water table elevation within the ash, water table wells will
not provide the source concentration information needed to adequately model migration
of contaminants from the site. In an ash basin the concentration of ash -related
constituents at the water table will more closely resemble the chemistry of water
discharged through the NPDES permitted outfall than the chemistry of groundwater that
is likely to migrate out of the facility and into groundwater.
13. Section 7.4.5, Page 17 — Groundwater Sampling — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that one or more of the existing monitoring wells may also be
sampled to supplement groundwater quality data. The most complete evaluation of
Con

groundwater quality at the site would be produced by sampling all existing wells
(compliance and voluntary) as well as the new proposed wells. The compliance and
voluntary wells were presumably installed for the purpose of evaluating site conditions in
their proximity. There is no readily apparent reason to limit the data upon which to base
future decisions. Water levels in all site wells, piezometers and impoundments should be
collected in one day rather than over a period of days as sampling is being done.
14. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 2. The list of analytical parameters on Table 2 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 2 should be modified to add cobalt, hexavalent
chromium, uranium and radium. These parameters are often found at elevated
concentrations in ash leachate and should be included to produce a thorough assessment.
The potential presence of these constituents will never be known unless they are included
on the list of required analytes.
15. Section 7.6, Page 17 — Site Conceptual Model — Neither of the proposed geologic cross
sections identified on Figure 4 pass through the 1985 ash basin. At least one cross
section should pass through the deepest area of each of the ash basins to evaluate the
relative positions of the bottom of the ash and the water table. A third cross section
should be constructed that passes through the 1985 ash basin. The water table and the
ash/soil interface at the base of each basin must be shown on each of the cross sections.
16. Section 7.7, Page 18 — Development of Groundwater Computer Model — The
groundwater model discussion provides no indication of information that will be used to
establish the source term used in the model. The plan includes no provision for data
collected from monitoring wells installed in as near the base of the ash. It is imperative
that realistic source term data be developed during the groundwater assessment to input
into the model. The discussion does indicate that SPLP leach tests will be conducted on
samples of ash and underlying soils collected during the investigation. The limitations of
using SPLP test results to estimate leachate source terms were previously discussed.
The work plan indicates that soil samples will be collected immediately below the ash
and at the bottom of the inside ash borings, neither of which will provide data about the
chemistry of pore water within the ash at the bottom of the impoundments. The need for
collecting pore water samples from wells set immediately above the base of the ash fill
was previously discussed.
The elevation water in the ponds is likely to have varied over time so that current
conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
groundwater model, once constructed, should be used to re-evaluate the direction
groundwater flow and areas of potential concern using historic pond water elevations.
7

Riverbend
Section 2.3, Page 3 - Regulatory Requirements — The text indicates that monitoring
wells MW-7SR and MW -713 are considered to represent background water quality. This
assertion must be tested before it may be taken as fact. The need for careful evaluation of
background conditions is especially important since the work plan indicates that the wells
have shown exceedances of water quality standards and the wells are located within the
area of potential interest identified in the drinking water well survey. This section as well
as section 7.5 of the work plan should be modified to evaluate the validity of background
groundwater monitoring locations and what the unimpacted background concentration
should be. Water quality from impacted wells identified as background must not be used
in calculation of site-specific background water quality concentrations.
2. Section 7.0, Page 9 — Assessment Work Plan — One of the primary goals of conducting
the groundwater assessment must be to identify the relative positions of the bottom
elevation of disposed ash and the underlying water table. Identification of the relative
positions of the bottom of disposed ash and the underlying water table in each ash basin
or storage area will have a significant impact on the potential effectiveness of various
closure scenarios.
3. Section 7.0, Page 9 — Assessment Work Plan — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that an undefined sub -set of the existing monitoring wells may also
be sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the site would be produced by sampling all existing wells
(compliance and voluntary) as well as the new proposed wells. The compliance and
voluntary wells were presumably installed for the purpose of evaluating site conditions in
their proximity. There is no readily apparent reason to limit the data upon which to base
future decisions.
4. Section 7.0, Page 10 — Assessment Work Plan — Collection and analysis of ash basin
water samples will likely be more representative of the quality of water that is discharged
through the permitted outfall rather than the leachate that is the source of groundwater
contamination. We have no objection to collecting ash basin water samples, but the
results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model.
5. Section 7.0, Page 10 — Assessment Work Plan — The work plan gives no indication that
water level elevations (impoundment water, groundwater, and surface waters) will be
identified. Multiple complete rounds of water elevation data are essential information
that must be collected to adequately characterize groundwater gradients and to identify
temporal and spatial variability, and will be necessary to calibrate the groundwater
model.
6. Section 7.1.2, Page 10 - Proposed Soil and Ash Sampling Locations and Depths —
Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin or storage area.
N.

At least one of the borings in each ash basin and storage area must be advanced at the
location expected to be located above the lowest point of disposed ash within each.
Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios.
7. Section 7.1.2, Page 10 - Constituent Sampling and Analyses - The constituent
sampling and analyses discussion indicates that soil and ash samples will be analyzed for
the parameters listed on Table 5 The list of analytical parameters on Table 5 is missing
several common ash -related parameters. Specifically, Table 5 should be modified to add
molybdenum, cobalt, hexavalent chromium, uranium and radium. These parameters are
often found at elevated concentrations in coal ash and should be included to produce a
thorough assessment. The potential presence or concentration of these constituents will
never be known unless they are included on the list of required analytes.
8. Section 7.1.2, Page 10 - Constituent Sampling and Analyses - The discussion and
footnote included in Table 5 indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples to evaluate leaching potential.
Application of short duration, low solid -ratio (dilute) leaching tests like the SPLP test
routinely underestimate the concentration of contaminants in flyash-derived leachates.
The procedure does not allow ash constituents sufficient time to come into equilibrium
with the fluid, the solid -water ratio is far more dilute than under disposal conditions, and
the laboratory conditions do not represent the disposal conditions under which leachate
will actually form. The National Research Council warned of the inadequacy of
laboratory characterization tests as surrogates for determining field leachate composition
specifically with respect to coal ash in their investigation of coal combustion ash disposal
in mined settings2. These tests were not designed or intended to represent predictions of
leachate that will form in the field, and to use them as such is inappropriate. Citing
results from outmoded tests that are widely acknowledged to be ineffective at predicting
leachate concentrations from saturated ash is a common industry practice that would call
into question the validity of the entire evaluation of current and potential future
environmental impacts.
9. Section 7.2, Page 11— Groundwater Sampling Plan — The work plan calls for water
table and deep (bedrock) monitoring wells to be constructed within ash storage units and
basins to characterize water chemistry within and beneath the ash. Wells screened within
the waste, at or near the bottom of each ash basin and storage area are critically needed to
characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
z Id.
I

evaluating the water table elevation within the ash, water table wells will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin, the concentration of ash -related constituents at the water
table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
10. Section 7.2, Page 11— Groundwater Sampling Plan — The BG -series wells identified
in the work plan may be thought to be properly placed to characterize background
chemistry, but this has not been shown to be the case at this time. It is inappropriate to
designate any well as representing background conditions before an evaluation of
background conditions has been completed. Water quality from impacted wells identified
as background must not be used in calculation of site-specific background water quality
concentrations.
11. Section 7.2.3, Page 12 — Groundwater Sampling — The discussion indicates that only
newly installed wells will be sampled. A more complete evaluation of groundwater
chemistry would be produced by including all existing wells (compliance and voluntary)
as well as the newly installed wells. There is no indication why previously existing wells
are not planned to be sampled as part of this assessment.
12. Section 7.2.3, Page 12 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 6. The list of analytical parameters on Table 6 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 6 should be modified to add molybdenum, cobalt,
hexavalent chromium, uranium and radium. These parameters are often found at elevated
concentrations in ash leachate and should be included to produce a thorough assessment.
The potential presence of these constituents will never be known unless they are included
on the list of required analytes.
13. Section 7.3.1, Page 14 — Ash Basin Surface Water Samples — Collection and analysis
of ash basin water samples will likely be more representative of the quality of water that
is discharged through the permitted outfall rather than the leachate that is the source of
groundwater contamination. We have no objection to collecting ash basin water samples,
but the results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model.
14. Section 7.5, Page 15 — Site -Specific Background Concentrations — The site-specific
background concentrations evaluation appears intended to investigate potential ways to
explain away exceedances of groundwater quality standards to naturally occurring
conditions or problems with sample collection methodology. This section of the work
plan should be modified to require evaluation of the validity of background groundwater
monitoring locations and what unimpacted background concentration should be. This
evaluation should consider more than the relationship between groundwater standard
exceedances and turbidity, or argue that high concentrations of ash -related constituents
10

s Id.
are naturally occurring in the groundwater. It should investigate whether historic high
ash basin water levels or leachate levels in ash storage areas may have provided sufficient
hydraulic head to reverse gradients and drive flow away from the impoundments in the
previously upgradient direction. If water in the impoundments or storage areas is or was
sufficiently high to reverse natural gradients, the previous and planned sampling could be
detecting ash -related contaminants that are or were migrating in what would be expected
to be upgradient under natural conditions. Use of impacted analyses from wells
erroneously assumed to represent background conditions would skew subsequent
statistical evaluations.
15. Section 7.6, Page 15 — Groundwater Model - The groundwater model discussion
indicates that several different pieces of information will be used to establish the source
term used in the model. None of the identified data sources include data collected from
monitoring wells installed near the base of the ash. It is imperative that realistic source
term data be developed during the groundwater assessment to input into the model. The
discussion indicates that the source term will be developed from leach tests and total
metals analysis, analysis of groundwater or surface water samples collected outside the
basin, analysis of water table wells screened within the ash, and data from other sites.
Each of the proposed data sources is problematic.
The text and Table 5 indicate that the Synthetic Precipitation Leaching Procedure (SPLP)
testing will be conducted on ash samples to evaluate leaching potential. Application of
short duration, low solid -ratio (dilute) leaching tests like the SPLP test routinely
underestimate the concentration of contaminants in flyash-derived leachates. The
procedure does not allow ash constituents sufficient time to come into equilibrium with
the fluid, the solid -water ratio is far more dilute than under disposal conditions, and the
laboratory conditions do not represent the disposal conditions under which leachate will
actually form. The National Research Council warned of the inadequacy of laboratory
characterization tests as surrogates for determining field leachate composition
specifically with respect to coal ash in their investigation of coal combustion ash disposal
in mined settings3. These tests were not designed or intended to represent predictions of
leachate that will form in the field, and to use them as such is inappropriate. Citing
results from inappropriate tests that are widely acknowledged to be ineffective at
predicting leachate concentrations from saturated ash is a common industry practice that
would call into question the validity of the entire evaluation of current and potential
future environmental impacts. The limitations of establishing source term concentrations
using SPLP tests can be readily avoided by installing and sampling monitoring wells at
the base of the disposed ash.
The discussion indicates that analytical results from groundwater monitoring wells or
surface water sample locations outside of the basin might be used to develop
concentration source terms. These analyses suffer from the obvious limitation that the
water has already been released from the basins and has been diluted by groundwater or
surface water. The limitations of establishing source term concentrations using SPLP
11

Mavo
tests can be readily avoided by installing monitoring points at the base of the disposed
ash.
The limitations of using ash basin pore water analyses from wells installed across the
water table within the basin were previously addressed. Use of published or other data
from leach tests conducted at other facilities would not be site-specific and would likely
be limited by the common industry practice of using the same inappropriate test. The
limitations of establishing source term concentrations using SPLP tests can be readily
avoided by installing monitoring points at the base of the disposed ash.
When completed, the groundwater model should be used to investigate changes to
hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Section 1.0, Page 1 - Introduction — The text indicates that background monitoring
wells are presently located upgradient of the ash basin. This designation must be tested
before it may be taken as fact. The elevation of water in the ash basin during coal plant
operations may have been sufficiently above the surrounding area that groundwater
flowed radially away from the impoundments, effectively transporting ash basin
contaminants toward the "background wells". This mechanism could reasonably be
expected to transport ash -related contaminants in groundwater away from the source and
account for the exceedances of 2L groundwater standards at background wells noted in
Table 1.
2. Section 1.0, Page 2 — Introduction — One of the primary goals of conducting the
groundwater assessment must be to identify the relative positions of the bottom elevation
of disposed ash and the underlying water table. Identification of the relative positions of
the bottom of disposed ash and the water table in each ash basin or storage area will have
a significant impact on the potential effectiveness of various closure scenarios.
3. Section 2.3, Page 3 — Groundwater Monitoring System - The work plan identifies
wells thought to be properly placed to characterize background chemistry, but this has not
been shown to be the case at this time. It is inappropriate to designate any well as
representing background conditions before an evaluation of background conditions has
been completed. Evaluation of background should investigate whether historic high ash
basin water levels may have provided sufficient hydraulic head to reverse gradients and
drive flow away from the impoundments in the previously upgradient direction. If water
in the impoundments is or was sufficiently high to reverse natural gradients, the previous
and planned sampling could be detecting ash -related contaminants that are or were
migrating in what would be expected to be upgradient under natural conditions. New
background monitoring wells may or may not show similar concentrations to the existing
wells. Use of impacted analyses from wells erroneously assumed to represent
background conditions would skew subsequent statistical evaluations.
12

a Id.
4. Section 5.0, Page 8 — Site Geology and Hydrogeology — The discussion of groundwater
flow does not reflect the influence of ash basin water on groundwater flow direction in
the proximity of the basin. Infiltration of water from the impoundment and into the
groundwater may have created mounding in the area causing radial flow away from the
impoundment. The elevation of groundwater in the impoundment must be established
and compared to surrounding water elevations in order to establish the local groundwater
gradient in the vicinity of the impoundment.
5. Section 6.1, Page 10 — Preliminary Statistical Evaluation Results — The inter -well
statistical evaluation discussed in this section compares concentrations of ash -related
constituents in compliance wells to concentrations measured in existing "background"
wells. As was previously discussed, the existing wells currently identified as background
have not been evaluated to show that they are actually representative of unimpacted
groundwater quality. Detections of various parameters in these wells at concentrations
above the 2L standards is a potential indication that unimpacted background conditions
are not being used in this analysis. The statistical evaluation needs to be repeated once
unimpacted background water quality has been verified.
6. Section 7.1., Page 12 - Anticipated Ash Basin Boring Locations — Please verify
through review of construction records or pre -development topography where the lowest
elevation ash is expected to be located in each ash basin or storage area. At least one of
the borings in each ash basin and storage area must be advanced at the location expected
to be located above the lowest point of disposed ash within each. Identification of the
relative positions of the bottom elevation of disposed ash and the underlying water table
is critical in evaluating the effectiveness of possible closure scenarios.
7. Section 7.1., Page 13 - Anticipated Ash Basin Boring Locations — The discussion in
this section and Table 3 each indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples. The intended use of these samples is
not clear from the discussion, but it must be made clear from the onset that SPLP results
cannot be used to approximate the source term for ash basin leachate concentrations in
the groundwater model. Application of short duration, low solid -ratio (dilute) leaching
tests like the SPLP test routinely underestimates the concentration of contaminants in
flyash-derived leachates. The procedure does not allow ash constituents sufficient time
to come into equilibrium with the fluid, the solid -water ratio is far more dilute than under
disposal conditions, and the laboratory conditions do not represent the disposal conditions
under which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings4. These tests were not designed or intended to
represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
13

concentrations using SPLP tests can be readily avoided by measuring ash pore water
concentrations by installing and sampling monitoring wells set at the base of the disposed
ash. While useful for evaluating the water table elevation within the ash, water table
wells will not provide the source concentration information needed to adequately model
migration of contaminants from the site. In an ash basin the concentration of ash -related
constituents at the water table will more closely resemble the chemistry of water
discharged through the NPDES permitted outfall than the chemistry of groundwater that
is likely to migrate out of the facility and into groundwater.
8. Section 7.2.1, Page 13 — Inside Ash Basins — The work plan should require that each of
the ash basin soil borings be completed as monitoring wells or piezometers. Completion
of the ash borings as piezometers would facilitate determination of the elevation of
groundwater within and below the impoundment at very little cost since the borehole will
already be present.
9. Section 7.3, Page 13 — Anticipated Sediment and Surface Water Locations — Prior to
initiating field work the existing seep sampling information should be reviewed to verify
that all identified seeps have been accurately located, the elevation of the seep has been
determined, and that analytical data include all parameters required by the work plan for
groundwater samples. In the event that all of these pieces of information do not exist, the
seeps should be sampled as part of this investigation.
10. Section 7.4.29 Page 16 — Background Wells — The existing and new wells should be
evaluated before the designation as background may be taken as fact. See comment #4.
This section also indicates that installation and sampling of additional background well
data will be useful to broaden the range of potential background groundwater
concentrations. The goal of new background wells should be to determine what
unimpacted groundwater chemistry should be, not to provide as broad a range as
possible. Retaining assumed background wells that are actually impacted by ash basin
leachate in the background data set would skew statistical comparisons of background
and downgradient wells.
11. Section 7.4.3, Page 15 — Ash Basin Areas — While useful for evaluating the hydraulic
head at the base of the ash, unsampled piezometers will not provide the source
concentration information needed to adequately model migration of contaminants from
the site. Wells screened within the waste, at or near the bottom of the ash basin and
storage area are critically needed to characterize the concentration of ash -related
constituents in leachate that is migrating from the facility. Leachate concentrations in ash
storage areas and basins typically increase with depth. Leachate at or near the bottom of
the impoundment or landfill has migrated through the waste column and had sufficient
contact time to come into chemical equilibrium with the waste matrix. The chemical
composition of leachate collected from the bottom of the ash basins and storage areas will
more realistically represent the chemistry of leachate that is leaving the units to migrate
with groundwater and must be used in developing the source term for input to the
groundwater model.
12. Section 7.4.4, Page 15 — Downgradient Assessment Areas — The work plan identifies a
pair of wells identified as "sentinel wells". Sentinel wells are wells located ahead of a
14

characterized contaminant plume used to verify that the leading edge of the plume has not
progressed to that particular location. In this case, the location of the leading edge of
contamination has not been identified and is not likely static, making designation of
sentinel wells premature and potentially misleading. The wells should be designated as
additional wells until such time as the contaminant plume has been fully characterized.
13. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater assessment work
plan indicates that groundwater samples will be collected from the proposed monitoring
wells and that one or more of the existing monitoring wells may also be sampled to
supplement groundwater quality data. The most complete evaluation of groundwater
quality at the site would be produced by sampling all existing wells as well as the new
proposed wells. The existing wells were presumably installed for the purpose of
evaluating site conditions in their proximity. There is no readily apparent reason to limit
the data upon which to base future decisions. Water levels in all site wells, piezometers,
and impoundments should be collected in one day rather than over a period of days as
sampling is being done.
14. Section 7.4.5, Page 16 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 2. The list of analytical parameters on Table 2 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 2 should be modified to add cobalt, hexavalent
chromium, uranium, and radium. These parameters are often found at elevated
concentrations in ash leachate and should be included to produce a thorough assessment.
The potential presence of these constituents will never be known unless they are included
on the list of required analytes.
15. Section 7.7, Page 18 — Development of Groundwater Computer Model— The
groundwater model discussion provides no indication of information that will be used to
establish the source term used in the model. The plan includes no provision for data
collected from monitoring wells installed in as near the base of the ash. It is imperative
that realistic source term data be developed during the groundwater assessment to input
into the model. The discussion does indicate that SPLP leach tests will be conducted on
samples of ash and underlying soils collected during the investigation. The limitations of
using SPLP test results to estimate leachate source terms were discussed in Comment #7.
The work plan indicates that soil samples will be collected immediately below the ash
and at the bottom of the inside ash borings, neither of which will provide data about the
chemistry of pore water within the ash at the bottom of the impoundments. The need for
collecting pore water samples from wells set at the base of the ash fill was discussed in
comment #11.
The elevation water in the ponds is likely to have varied over time so that current
conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
15

groundwater model, once constructed, should be used to re-evaluate the direction
groundwater flow and areas of potential concern using historic pond water elevations.
H.F. Lee
1. Section 1.0, Page 1- Introduction — The text indicates that background monitoring
wells are presently located near the inactive and active ash basins. This designation must
be tested before it may be taken as fact. The locations of these wells, shown on Figures 2
and 3, indicate that they are located on the Neuse River floodplain in areas that would
likely be upgradient during portions of the year. Their location on the floodplain would
also indicate that during periods of high water in the Neuse River groundwater may
actually flow from the river, beneath the ash basins and toward the identified background
wells. The elevation of water in the ash basins during coal plant operations may have
been sufficiently above the surrounding area that groundwater flowed radially away from
the impoundments, effectively transporting ash basin contaminants toward the
"background wells". Either of these mechanisms could reasonably be expected to
transport ash -related contaminants in groundwater away from the river and account for
the exceedances of 2L groundwater standards at background wells noted in Table 1.
2. Section 1.0, Page 2 — Introduction — One of the primary goals of conducting the
groundwater assessment must be to identify the relative positions of the bottom elevation
of disposed ash and the underlying water table. Identification of the relative positions of
the bottom of disposed ash and the water table in each ash basin or storage area will have
a significant impact on the potential effectiveness of various closure scenarios.
3. Section 2.2, Page 3 — Ash Basins — The description of the ash basins does not indicate
whether they currently retain water. The aerial photograph that serves as the base for
Figure 2 shows an area devoid of vegetation at the southwest corner that may be an area
of standing water at certain times of the year. The aerial photograph that serves as the
base for Figure 3 clearly shows standing water. If present, the elevation of ponded water
in the impoundments must be identified. The proposed groundwater assessment must be
capable of determining if surface runoff is actually being retained in the ash basins or if
water in the impoundments represents the elevation of the water table at those locations.
4. Section 2.3, Page 3 — Groundwater Monitoring System - The work plan identifies
wells thought to be properly placed to characterize background chemistry, but this has not
been shown to be the case at this time. It is inappropriate to designate any well as
representing background conditions before an evaluation of background conditions has
been completed. Evaluation of background should investigate whether historic high ash
basin water levels may have provided sufficient hydraulic head to reverse gradients and
drive flow away from the impoundments in the previously upgradient direction. If water
in the impoundments is or was sufficiently high to reverse natural gradients, the previous
and planned sampling could be detecting ash -related contaminants that are or were
migrating in what would be expected to be upgradient under natural conditions. New
background monitoring wells may or may not show similar concentrations to the existing
wells. Use of impacted analyses from wells erroneously assumed to represent
background conditions would skew subsequent statistical evaluations.
16

s Id.
5. Section 5.0, Page 8 — Site Geology and Hydrogeology — The discussion of groundwater
flow does not reflect the influence of ash basin water on groundwater flow direction in
the proximity of the basins. Infiltration of water from the impoundments and into the
groundwater likely created mounding in the area creating radial flow away from the
impoundments in all directions. The elevation of groundwater in each impoundment
must be established in order to establish whether mounding of groundwater within and
below the impoundment persists even though plant operations have ceased.
6. Section 6.1, Page 10 — Preliminary Statistical Evaluation Results — The inter -well
statistical evaluation discussed in this section compares concentrations of ash -related
constituents in compliance wells to concentrations measured in existing "background"
wells. As was previously discussed, the existing wells currently identified as background
have not been evaluated to show that they are actually representative of unimpacted
groundwater quality. The statistical evaluation may need to be repeated once unimpacted
background water quality has been verified.
7. Section 7.1., Page 12 - Anticipated Ash Basin Boring Locations — Please verify
through review of construction records or pre -development topography where the lowest
elevation ash is expected to be located in each ash basin or storage area. At least one of
the borings in each ash basin and storage area must be advanced at the location expected
to be located above the lowest point of disposed ash within each. Identification of the
relative positions of the bottom elevation of disposed ash and the underlying water table
is critical in evaluating the effectiveness of possible closure scenarios.
8. Section 7.1., Page 12 - Anticipated Ash Basin Boring Locations — The discussion in
this section and Table 3 each indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples. The intended use of these samples is
not clear from the discussion, but it must be made clear from the onset that SPLP results
cannot be used to approximate the source term for ash basin leachate concentrations in
the groundwater model. Application of short duration, low solid -ratio (dilute) leaching
tests like the SPLP test routinely underestimates the concentration of contaminants in
flyash-derived leachates. The procedure does not allow ash constituents sufficient time
to come into equilibrium with the fluid, the solid -water ratio is far more dilute than under
disposal conditions, and the laboratory conditions do not represent the disposal conditions
under which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings5. These tests were not designed or intended to
represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by measuring ash pore water
concentrations by installing and sampling monitoring wells set at the base of the disposed
17

ash. While useful for evaluating the water table elevation within the ash, water table
wells will not provide the source concentration information needed to adequately model
migration of contaminants from the site. In an ash basin the concentration of ash -related
constituents at the water table will more closely resemble the chemistry of water
discharged through the NPDES permitted outfall than the chemistry of groundwater that
is likely to migrate out of the facility and into groundwater.
9. Section 7.2.1, Page 13 — Inside Ash Basins — The work plan should require that each of
the ash basin soil borings be completed as monitoring wells or piezometers. Completion
of the ash borings as piezometers would facilitate determination of the elevation of
groundwater below the impoundment at very little cost since the borehole will already be
present.
10. Section 7.3, Page 13 — Anticipated Sediment and Surface Water Locations — Prior to
initiating field work, the existing seep sampling information should be reviewed to verify
that all identified seeps have been accurately located, that the elevation of the seep has
been determined, and that analytical data include all parameters required by the work
plan for groundwater samples. In the event that all of these pieces of information do not
exist, the seeps should be sampled as part of this investigation.
11. Section 7.4.29 Page 16 — Background Wells — The existing and new wells should be
evaluated before the designation as background may be taken as fact. See comment #4.
12. Section 7.4.2, Page 16 — Ash Basins — The work plan indicates that previous assessment
activities at the plant have included installation of piezometers within the inactive ash
basin and that two pairs of piezometers will be installed within the active ash basin.
Shallow piezometers constructed to intercept the water table within the ash are needed to
evaluate the lateral and vertical gradients within the ash.
While useful for evaluating the hydraulic head at the base of the ash, unsampled
piezometers will not provide the source concentration information needed to adequately
model migration of contaminants from the site. Wells screened within the waste, at or
near the bottom of each ash basin and storage area are critically needed to characterize
the concentration of ash -related constituents in leachate that is migrating from the
facility. Leachate concentrations in ash storage areas and basins typically increase with
depth. Leachate at or near the bottom of the impoundment or landfill has migrated
through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model.
13. Section 7.4.5, Page 17 — Groundwater Sampling — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that one or more of the existing monitoring wells may also be
sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the site would be produced by sampling all existing wells as well
as the new proposed wells. The existing wells were presumably installed for the purpose
IN

of evaluating site conditions in their proximity. There is no readily apparent reason to
limit the data upon which to base future decisions. Water levels in all site wells,
piezometers, and impoundments should be collected in one day rather than over a period
of days as sampling is being done.
14. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 2. The list of analytical parameters on Table 2 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 2 should be modified to add cobalt, hexavalent
chromium, uranium, and radium. These parameters are often found at elevated
concentrations in ash leachate and should be included to produce a thorough assessment.
The potential presence of these constituents will never be known unless they are included
on the list of required analytes.
15. Section 7.7, Page 18 — Development of Groundwater Computer Model — The
groundwater model discussion provides no indication of information that will be used to
establish the source term used in the model. The plan includes no provision for data
collected from monitoring wells installed in as near the base of the ash. It is imperative
that realistic source term data be developed during the groundwater assessment to input
into the model. The discussion does indicate that SPLP leach tests will be conducted on
samples of ash and underlying soils collected during the investigation. The limitations of
using SPLP test results to estimate leachate source terms were discussed in Comment #8.
Sutton
The work plan indicates that soil samples will be collected immediately below the ash
and at the bottom of the inside ash borings, neither of which will provide data about the
chemistry of pore water within the ash at the bottom of the impoundments. The need for
collecting pore water samples from wells set at the base of the ash fill was discussed in
comment #12.
The elevation water in the ponds is likely to have varied over time so that current
conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
groundwater model, once constructed, should be used to re-evaluate the direction
groundwater flow and areas of potential concern using historic pond water elevations.
Section 1.0, Page 1 - Introduction — The text indicates that two of the existing wells are
considered to be background monitoring wells. This designation must be tested before it
may be taken as fact. The need for careful evaluation of background conditions is
especially important since the work plan (Table 1) indicates that the wells have shown
exceedances of water quality standards and the Drinking Water Well and Receptor
Survey show the wells to be located near the potential area of interest. Groundwater
quality data from wells that are potentially impacted by on-site or off-site sources should
19

not be used as unimpacted background water quality. Section 7.4.2 of the work plan
should be modified so that the validity of background groundwater monitoring locations
will be evaluated and so that new background monitoring locations will be established
and the existing wells will not be used in statistical evaluations if potential impacts from
on-site or off-site sources are confirmed.
2. Section 1.0, Page 2 — Introduction — One of the primary goals of conducting the
groundwater assessment must be to identify the relative positions of the bottom elevation
of disposed ash and the underlying water table. Identification of the relative positions of
the bottom of disposed ash and the water table in each ash basin or storage area will have
a significant impact on the potential effectiveness of various closure scenarios.
3. Section 2.3, Page 4 — Groundwater Monitoring System — The discussion indicates that
groundwater flow is radial, away from the ash management area, but identifies no
monitoring points to the west, between the ash ponds and Sutton Lake. The discussion
should describe any assumptions about the fate and transport of ash -related contaminants
to the west. Does Duke accept an assumption that contaminants are discharging directly
into Sutton Lake and/or the Cape Fear River? If not, how will the extent of
contamination and the fate of contaminants migrating in that direction be identified?
4. Section 5.0, Page 10 — Regional Geology and Hydrogeology — The text makes passing
reference to groundwater flow to the west from the ash management area at the end of
this section. Subsequent sections indicate no monitoring is planned to evaluate the fate
and transport of ash -related contaminants in that direction. See comment #3.
5. Section 6.2, Page 11— Groundwater Analytical Results — Detections of cadmium,
lead, selenium, and TDS in background or compliance wells at concentrations above the
2L standard are described as being potentially the result of sample turbidity or as
representing data outliers. Elevated sample turbidity is an indication of improper well
design or developments that indicate the need for installation of new monitoring points
(see comment #1). Recurrent detections of elevated ash -related parameters are more
likely to represent natural variation caused by variable groundwater flow direction,
changes in contaminant concentration related to water level variation, or other natural
events and call for additional investigation to evaluate the cause rather than blind
acceptance of the data as outliers.
6. Section 6.2, Page 11— Preliminary Statistical Evaluation — The inter -well statistical
evaluation discussed in this section compares concentrations of ash -related constituents in
compliance wells to concentrations measured in existing "background" wells. As was
previously noted, the work plan (Table 1) indicates that the existing wells have shown
exceedances of water quality standards and the Drinking Water Well and Receptor
Survey show the wells to be located near the potential area of interest. Comparisons to
these wells may not represent comparison to true unimpacted background.
7. Section 7.2, Page 14 — Anticipated Ash Basin Boring Locations — The work plan
indicates that no borings are planned for the New Ash Basin Area. The depth, chemistry
and physical properties of ash in each basin and storage area need to be characterized.
20

Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin or storage area.
At least one of the borings in each ash basin and storage area must be advanced at the
location expected to be located above the lowest point of disposed ash within each.
Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios.
8. Section 7.1., Page 14 - Anticipated Ash Basin Boring Locations — The discussion in
this section and Table 3 each indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples. The intended use of these samples is
not clear from the discussion, but it must be made clear from the onset that SPLP results
cannot be used to approximate the source term for ash basin leachate concentrations in
the groundwater model. Application of short duration, low solid -ratio (dilute) leaching
tests like the SPLP test routinely underestimate the concentration of contaminants in
flyash-derived leachates. The procedure does not allow ash constituents sufficient time
to come into equilibrium with the fluid, the solid -water ratio is far more dilute than under
disposal conditions, and the laboratory conditions do not represent the disposal conditions
under which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings6. These tests were not designed or intended to
represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by measuring ash pore water
concentrations by installing and sampling monitoring wells set at the base of the disposed
ash. While useful for evaluating the water table elevation within the ash, water table
wells will not provide the source concentration information needed to adequately model
migration of contaminants from the site. In an ash basin the concentration of ash -related
constituents at the water table will more closely resemble the chemistry of water
discharged through the NPDES permitted outfall than the chemistry of groundwater that
is likely to migrate out of the facility and into groundwater.
9. Section 7.2.1, Page 14 — Inside Ash Basins — The work plan should require that each of
the ash basin soil borings be completed as monitoring wells or piezometers. Completion
of the ash borings as piezometers or wells would facilitate determination of the elevation
of groundwater below the impoundment at very little cost since the borehole will already
be present. Completion borings as wells will facilitate collection of ash pore water and
underlying groundwater for chemical analysis.
10. Section 7.3, Page 14 — Anticipated Sediment and Surface Water Locations — Flow of
groundwater from the ash basins toward surface water in Sutton Lake and the Cape Fear
6 Id.
21

River was admitted in a previous section (see comment #3). Samples of surface water
from Sutton Lake and from the Cape Fear River are, at a minimum, necessary to evaluate
the chemistry of each of these receptors.
11. Section 7.4.2, Page 16 — Background Wells — See comment #1.
12. Section 7.4.2, Page 16 — Ash Management Area — Monitoring wells screened within
the waste, at or near the bottom of each ash basin and storage area, are critically needed
to characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
evaluating the water table elevation within the ash, piezometers will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin, the concentration of ash -related constituents at the water
table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
13. Section 7.4.4, Page 17 — Downgradient Assessment Areas — The description of
planned downgradient monitoring wells includes no planned wells in the vicinity of the
Former Ash Disposal Area. Additional monitoring wells located to adequately
characterize groundwater flow and quality in this vicinity are a glaring omission from this
plan.
14. Section 7.4.4, Page 17 — Downgradient Assessment Areas — Sutton Lake and the Cape
Fear River are located immediately downgradient to the west and southwest from all of
the ash management facilities, but characterization of groundwater flow in these
directions is completely missing from this plan. Duke can either stipulate that ash—
related contaminants are being discharged to these surface water receptors, or propose
methods to show that this in not occurring. Ignoring discharges from Duke's facilities
into surface waters is not an option.
15. Section 7.4.4, Page 17 — Downgradient Assessment Areas — The work plan identifies
six pairs of wells identified as "sentinel wells". Sentinel wells are wells located outside
of a characterized contaminant plume used to verify that the leading edge of the plume
has not progressed to that particular location. In this case, the location of the leading
edge of contamination has not been identified and is not likely static making designation
of sentinel wells premature and potentially misleading. The wells should be designated
as additional wells until such time as the contaminant plume has been fully characterized.
16. Section 7.4.5, Page 17 — Groundwater Sampling — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
22

monitoring wells and that one or more of the existing monitoring wells may also be
sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the site would be produced by sampling all existing wells
(compliance and voluntary) as well as the new proposed wells. The compliance and
voluntary wells were presumably installed for the purpose of evaluating site conditions in
their proximity. There is no readily apparent reason to limit the data upon which to base
future decisions. Water levels in all site wells, piezometers, and impoundments should be
collected in one day rather than over a period of days as sampling is being done.
17. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 2. The list of analytical parameters on Table 2 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 2 should be modified to add cobalt, hexavalent
chromium, uranium, and radium. These parameters are often found at elevated
concentrations in ash leachate and should be included to produce a thorough assessment.
The potential presence of these constituents will never be known unless they are included
on the list of required analytes.
18. Section 7.6, Page 17 — Influence of Pumping Wells on Groundwater System — This
section describes the potential installation of data loggers on one or more monitoring
wells to investigate the effect of nearby public and private water supply wells located
downgradient of the ash management areas. The discussion is inappropriately vague
given the potential that the public is being exposed to ash -related contaminants. At a
minimum, any nearby water supply wells thought to potentially be at risk should
immediately sampled, voluntarily without waiting for approval of the work plan, and
tested for the full suite of analytical parameters. Further, the plan must identify the wells
at risk, and identify data that will be collected and which wells will be instrumented. The
NCDENR should take an aggressive stance on this issue in order to minimize the public's
exposure to Duke's groundwater contaminants.
19. Section 7.6, Page 17 — Site Conceptual Model — At least one cross section should pass
through the deepest area of each of the ash basins (see comment #7) to evaluate the
relative positions of the bottom of the ash and the water table. The water table and the
ash/soil interface at the base of each basin must be shown on each of the cross sections.
20. Section 7.7, Page 18 — Development of Groundwater Computer Model— The
groundwater model discussion provides no indication of information that will be used to
establish the source term used in the model. The plan includes no provision for data
collected from monitoring wells installed in as near the base of the ash. It is imperative
that realistic source term data be developed during the groundwater assessment to input
into the model. The discussion does indicate that SPLP leach tests will be conducted on
samples of ash and underlying soils collected during the investigation. The limitations of
using SPLP test results to estimate leachate source terms were discussed in Comment #8.
23

The work plan indicates that soil samples will be collected immediately below the ash
and at the bottom of the inside ash borings, neither of which will provide data about the
chemistry of pore water within the ash at the bottom of the impoundments. The need for
collecting pore water samples from wells set at the base of the ash fill was discussed in
comment #12.
The elevation water in the ponds is likely to have varied over time so that current
conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
groundwater model, once constructed, should be used to re-evaluate the direction
groundwater flow and areas of potential concern using historic pond water elevations.
Roxboro
Section 1.0, Page 1 - Introduction — The text indicates that a background monitoring
well is presently located upgradient of the ash basin. This designation must be tested
before it may be taken as fact. Evaluation of unimpacted groundwater chemistry is
particularly important since the identified "background" monitoring points have shown
concentrations of ash -related parameters in concentrations above the 2L standard. The
elevation of water in the ash basin during coal plant operations may have been
sufficiently above the surrounding area that groundwater flowed radially away from the
impoundments, effectively transporting ash basin contaminants toward the "background
wells." This mechanism could reasonably be expected to transport ash -related
contaminants in groundwater away from the impoundments and account for the
exceedances of 2L groundwater standards at the background well noted in Table 1.
2. Section 1.0, Page 2 — Introduction — One of the primary goals of conducting the
groundwater assessment must be to identify the relative positions of the bottom elevation
of disposed ash and the underlying water table. Identification of the relative positions of
the bottom of disposed ash and the water table in each ash basin or storage area will have
a significant impact on the potential effectiveness of various closure scenarios.
3. Section 2.3, Page 3 — Ash Management Areas - Review of Figure 2 shows what
appears to be impoundments that have been constructed over the west ash basin. This
section should describe these impoundments, their use, and how leakage from these
impoundments might affect water levels and leachate generation in the west ash basin
4. Section 2.3, Page 4 — Groundwater Monitoring System - The work plan identifies one
well thought to be properly placed to characterize background chemistry, but this has not
been shown to be the case at this time. It is inappropriate to designate any well as
representing background conditions before an evaluation of background conditions has
been completed. Evaluation of background should investigate whether historic high ash
basin water levels may have provided sufficient hydraulic head to reverse gradients and
drive flow away from the impoundments in the previously upgradient direction. If water
in the impoundments is or was sufficiently high to reverse natural gradients, the previous
and planned sampling could be detecting ash -related contaminants that are or were
24

' Id.
migrating in what would be expected to be upgradient under natural conditions. New
background monitoring wells may or may not show similar concentrations to the existing
wells. Use of impacted analyses from wells erroneously assumed to represent
background conditions would skew subsequent statistical evaluations.
5. Section 5.0, Page 10 — Site Geology and Hydrogeology — The discussion of
groundwater gradients does not reflect the influence of ash basin water on groundwater
flow direction in the proximity of the basins. Infiltration of water from the impoundment
and into the groundwater may have created mounding in the area causing radial flow
away from the impoundment. The elevation of groundwater in the impoundments must
be established and compared to surrounding water elevations in order to establish the
local groundwater gradient in the vicinity of the impoundments.
6. Section 6.1, Page 11 — Preliminary Statistical Evaluation Results — The inter -well
statistical evaluation discussed in this section compares concentrations of ash -related
constituents in compliance wells to concentrations measured in existing "background"
wells. As was previously discussed, the existing wells currently identified as background
have not been evaluated to show that they are actually representative of unimpacted
groundwater quality. Detections of various parameters in these wells at concentrations
above the 2L standards are a potential indication that unimpacted background conditions
are not being used in this analysis. The statistical evaluation needs to be repeated once
unimpacted background water quality has been verified.
7. Section 7.1., Page 13 - Anticipated Soil Basin Boring Locations — Please verify
through review of construction records or pre -development topography where the lowest
elevation ash is expected to be located in each ash basin or storage area. At least one of
the borings in each ash basin and storage area must be advanced at the location expected
to be located above the lowest point of disposed ash within each. Identification of the
relative positions of the bottom elevation of disposed ash and the underlying water table
is critical in evaluating the effectiveness of possible closure scenarios.
8. Section 7.1., Page 13 - Anticipated Ash Basin Boring Locations — The discussion in
this section and Table 3 each indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples. The intended use of these samples is
not clear from the discussion but it must be made clear from the onset that SPLP results
cannot be used to approximate the source term for ash basin leachate concentrations in
the groundwater model. Application of short duration, low solid -ratio (dilute) leaching
tests like the SPLP test routinely underestimate the concentration of contaminants in
flyash-derived leachates. The procedure does not allow ash constituents sufficient time
to come into equilibrium with the fluid, the solid -water ratio is far more dilute than under
disposal conditions, and the laboratory conditions do not represent the disposal conditions
under which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings. These tests were not designed or intended to
25

represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by measuring ash pore water
concentrations by installing and sampling monitoring wells set at the base of the disposed
ash. While useful for evaluating the water table elevation within the ash, water table
wells will not provide the source concentration information needed to adequately model
migration of contaminants from the site. In an ash basin the concentration of ash -related
constituents at the water table will more closely resemble the chemistry of water
discharged through the NPDES permitted outfall than the chemistry of groundwater that
is likely to migrate out of the facility and into groundwater.
9. Section 7.2.1, Page 14 — Inside Ash Basins — The work plan should require that each of
the ash basin soil borings be completed as monitoring wells or piezometers. Completion
of the ash borings as piezometers would facilitate determination of the elevation of
leachate and groundwater, within and below the impoundment, at very little cost since the
borehole will already be present.
10. Section 7.3, Page 13 — Anticipated Sediment and Surface Water Locations — Prior to
initiating field work, the existing seep sampling information should be reviewed to verify
that all identified seeps have been accurately located, that the elevation of the seep has
been determined, and that analytical data include all parameters required by the work
plan for groundwater samples. In the event that all of these pieces of information do not
exist, the seeps should be sampled as part of this investigation.
11. Section 7.4.2, Page 16 — Background Wells — The existing and new wells should be
evaluated before the designation as background may be taken as fact. See comment #4.
This section also indicates that installation and sampling of additional background well
data will be useful to broaden the range of potential background groundwater
concentrations. The goal of new background wells should be to determine what
unimpacted groundwater chemistry should be, not to provide as broad a range as
possible. Retaining assumed background wells that are actually impacted by ash basin
leachate in the background data set would skew statistical comparisons of background
and downgradient wells.
12. Section 7.4.3, Page 17 — Ash Basin Areas — The work plan indicates that a number of
piezometers and monitoring wells are present in and around both ash basin areas.
Review of Figure 4 shows piezometers along the northwest side of the east basin and no
well of piezometers located within the west ash basin. The well location map seems to
indicate that not all of the east ash basin is covered by the lined landfill and wells could
be constructed. Groundwater monitoring wells should be constructed in each of the ash
basins. Wells screened within the waste, at or near the bottom of the ash basin and
storage area, are critically needed to characterize the concentration of ash -related
constituents in leachate that is migrating from the facility. Leachate concentrations in ash
storage areas and basins typically increase with depth. Leachate at or near the bottom of
26

the impoundment or landfill has migrated through the waste column and had sufficient
contact time to come into chemical equilibrium with the waste matrix. The chemical
composition of leachate collected from the bottom of the ash basins and storage areas will
more realistically represent the chemistry of leachate that is leaving the units to migrate
with groundwater and must be used in developing the source term for input to the
groundwater model.
13. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater assessment work
plan indicates that groundwater samples will be collected but does not specify that all
new and existing wells will be included. The most complete evaluation of groundwater
quality at the site would be produced by sampling all existing wells as well as the new
proposed wells. The existing wells were presumably installed for the purpose of
evaluating site conditions in their proximity. There is no readily apparent reason to limit
the data upon which to base future decisions. Water levels in all site wells, piezometers,
and impoundments should be collected in one day rather than over a period of days as
sampling is being done.
14. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 2. The list of analytical parameters on Table 2 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 2 should be modified to add cobalt, hexavalent
chromium, uranium, and radium. These parameters are often found at elevated
concentrations in ash leachate and should be included to produce a thorough assessment.
The potential presence of these constituents will never be known unless they are included
on the list of required analytes.
15. Section 7.7, Page 18 — Development of Groundwater Computer Model — The
groundwater model discussion provides no indication of information that will be used to
establish the source term used in the model. The plan includes no provision for data
collected from monitoring wells installed in as near the base of the ash. It is imperative
that realistic source term data be developed during the groundwater assessment to input
into the model. The discussion does indicate that SPLP leach tests will be conducted on
samples of ash and underlying soils collected during the investigation. The limitations of
using SPLP test results to estimate leachate source terms were discussed in Comment #7.
The work plan indicates that soil samples will be collected immediately below the ash
and at the bottom of the inside ash borings, neither of which will provide data about the
chemistry of pore water within the ash at the bottom of the impoundments. The need for
collecting pore water samples from wells set at the base of the ash fill was discussed in
comment #11.
The elevation water in the ponds is likely to have varied over time so that current
conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
27

Allen
groundwater model, once constructed, should be used to re-evaluate the direction
groundwater flow and areas of potential concern using historic pond water elevations.
Section 2.3, Page 4 - Regulatory Requirements — The text indicates that monitoring
well AB -R1 is considered by Duke Energy to represent background water quality because
it is located to the northwest of the active basin (i.e., upgradient). This assertion must be
tested before it taken as fact, no matter what Duke Energy considers a well to represent.
The need for careful evaluation of background conditions is especially important since
the work plan indicates that the well has shown exceedances of water quality standards.
Section 7.5 of the work plan should be modified to evaluate the validity of background
groundwater monitoring locations and what unimpacted background concentration should
be. See comment #12.
2. Section 7.0, Page 9 — Assessment Work Plan — One of the primary goals of conducting
the groundwater assessment must be to identify the relative positions of the bottom
elevation of disposed ash and the underlying water table. Identification of the relative
positions of the bottom of disposed ash and the underlying water table in each ash basin
or storage area will have a significant impact on the potential effectiveness of various
closure scenarios.
3. Section 7.0, Page 10 — Assessment Work Plan — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that an undefined sub -set of the existing monitoring wells may also
be sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the CSS site would be produced by sampling all existing wells
(compliance and voluntary) as well as the new proposed wells. The compliance and
voluntary wells were presumably installed for the purpose of evaluating site conditions in
their proximity. There is no readily apparent reason to limit the data upon which to base
future decisions.
4. Section 7.0, Page 10 — Assessment Work Plan — The work plan gives no indication that
water level elevations (impoundment water, groundwater, and surface waters) will be
identified. Multiple complete rounds of water elevation data is essential information that
must be collected to adequately characterize groundwater gradients and to identify
temporal and spatial variability, and will be necessary to calibrate the groundwater
model.
5. Section 7.1.2, Page 10 - Proposed Soil and Ash Sampling Locations and Depths —
Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin or storage area.
At least one of the borings in each ash basin and storage area must be advanced at the
location expected to be located above the lowest point of disposed ash within each.
Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios. See comment #4.

6. Section 7.1.2, Page 10 - Constituent Sampling and Analyses - The constituent
sampling and analyses discussion indicates that soil and ash samples will be analyzed for
the parameters listed on Table 5 The list of analytical parameters on Table 5 is missing
several common ash -related parameters. Specifically, Table 5 should be modified to add
molybdenum, cobalt, hexavalent chromium, uranium, and radium. These parameters are
often found at elevated concentrations in coal ash and should be included to produce a
thorough assessment. The potential presence or concentration of these constituents will
never be known unless they are included on the list of required analytes.
7. Section 7.2, Page 11— Groundwater Sampling Plan — The work plan calls for water
table and deep (bedrock) monitoring wells to be constructed within ash storage units and
basins to characterize pore water chemistry within the ash. Wells screened within the
waste, at or near the bottom of each ash basin and storage area, are critically needed to
characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
evaluating the water table elevation within the ash, water table wells will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin the concentration of ash -related constituents at the water
table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
8. Section 7.2, Page 11— Groundwater Sampling Plan — The BG -series wells identified
in the work plan may be thought to be properly placed to characterize background
chemistry, but this has not been shown to be the case at this time. It is inappropriate to
designate any well as representing background conditions before an evaluation of
background conditions has been completed. See comment #1.
9. Section 7.2.3, Page 12 — Groundwater Sampling — The discussion indicates that only
newly installed wells will be sampled. A more complete evaluation of groundwater
chemistry would be produced by installing all existing wells (compliance and voluntary)
as well as the newly installed wells. There is no indication why previously existing wells
are not planned to be sampled as part of this assessment.
10. Section 7.2.3, Page 12 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 6. The list of analytical parameters on Table 6 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 6 should be modified to add molybdenum, cobalt,
hexavalent chromium, uranium, and radium. These parameters are often found at
29

elevated concentrations in ash leachate and should be included to produce a thorough
assessment. The potential presence of these constituents will never be known unless they
are included on the list of required analytes.
11. Section 7.3.1, Page 14 — Ash Basin Surface Water Samples — Collection and analysis
of ash basin water samples will likely be more representative of the quality of water that
is discharged through the permitted outfall rather than the leachate that is the source of
groundwater contamination. We have no objection to collecting ash basin water samples,
but the results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model. See comment #7.
12. Section 7.5, Page 15 — Site -Specific Background Concentrations — The site-specific
background concentrations evaluation is obviously intended to investigate potential ways
to explain away exceedances of groundwater quality standards to naturally occurring
conditions or problems with sample collection methodology. This section of the work
plan should be modified to require evaluation of the validity of background groundwater
monitoring locations and of what unimpacted background concentration should be. This
evaluation should consider more than the relationship between groundwater standard
exceedances and turbidity, or argue that high concentrations of ash -related constituents
are naturally occurring in the groundwater. It should investigate whether historic high
ash basin water levels may have provided sufficient hydraulic head to reverse gradients
and drive flow away from the impoundments in the previously upgradient direction. If
water in the impoundments is or was sufficiently high to reverse natural gradients, the
previous and planned sampling could be detecting ash -related contaminants that are or
were migrating in what would be expected to be upgradient under natural conditions.
The use of impacted analyses from wells erroneously assumed to represent background
conditions would skew subsequent statistical evaluations.
13. Section 7.6, Page 15 — Groundwater Model — The groundwater model discussion
indicates that several different pieces of information will be used to establish the source
term used in the model. None of the identified data sources include data collected from
monitoring wells installed in as near the base of the ash. It is imperative that realistic
source term data be developed during the groundwater assessment to input into the
model. The discussion indicates that the source term will be developed from leach tests
and total metals analysis, analysis of groundwater or surface water samples collected
outside the basin, analysis of water table wells screened within the ash, and data from
other sites. Each of the proposed data sources is problematic.
The discussion and footnote included in Table 5 indicate that the Synthetic Precipitation
Leaching Procedure (SPLP) testing will be conducted on ash samples to evaluate
leaching potential. Application of short duration, low solid -ratio (dilute) leaching tests
like the SPLP test routinely underestimate the concentration of contaminants in flyash-
derived leachates. The procedure does not allow ash constituents sufficient time to come
into equilibrium with the fluid, the solid -water ratio is far more dilute than under disposal
conditions, and the laboratory conditions do not represent the disposal conditions under
which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
kro

leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings$. These tests were not designed or intended to
represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by installing monitoring points at
the base of the disposed ash as described in comment #7.
The discussion indicates that analytical results from groundwater monitoring wells or
surface water sample locations outside of the basin might be used to develop
concentration source terms. These analyses suffer from the obvious limitations of having
already been released from the basins and being diluted in flowing groundwater or
surface water, and interacting with aquifer materials prior to analyses. The limitations of
establishing source term concentrations using SPLP tests can be readily avoided by
installing monitoring points at the base of the disposed ash as described in comment #7.
The limitations of using ash basin pore water analyses from wells installed across the
water table within the basin was previously addressed in comment #7. Use of published
or other data from leach tests conducted at other facilities would not be site-specific and
would likely be limited by the common industry practice of using the same outmoded
tests as were proposed in Table 5. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by installing monitoring points at
the base of the disposed ash as described in comment #7.
When completed, the groundwater model should be used to investigate changes to
hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Cliffside
8 Id.
1. Section 2.3, Page 3 - Regulatory Requirements — This section of the work plan
describes the location of wells included in the compliance groundwater monitoring
system for the CSS ash basin. Locations of the wells are shown of Figures 2 and 3. The
work plan indicates that the locations of all compliance groundwater monitoring wells
were approved by the North Carolina Department of Environment and Natural Resources
(NCDNER) DWR Aquifer Protection Section (APS).
Monitoring well MW-25DR is listed as a compliance monitoring well for the CSS ash
basin. Compliance monitoring wells must be located in positions that will allow
detections releases from the facility being monitored. Monitoring well MW-25DR is
located across the Broad River from the CSS Ash Basin and therefore can under no
circumstances be considered an appropriately located compliance monitoring point.
NCDENR must re-evaluate use of well MW-25DR as a compliance monitoring well for
the CSS and require that an appropriate monitoring location be established.
31

2. Section 2.3, Page 3 — Regulatory Requirements — Monitoring wells MW -23D and
MW-23DR are listed as compliance monitoring wells for the CSS active ash basin.
Compliance monitoring wells must be located in positions that will allow detections
releases from the facility being monitored. Monitoring wells MW -23D and MW-23DR
appear on Figures 2 and 3 to be located across Suck Creek from the CSS Ash Basin.
Please explain how these wells can be considered as appropriately located compliance
monitoring points. NCDENR must re-evaluate use of wells MW -23D and MW-23DR as
compliance monitoring wells for the CSS and require that an appropriate monitoring
location be established.
3. Section 2.3, Page 4 - Regulatory Requirements — Exceedances of groundwater quality
standards at monitoring well MW-25DR for chromium and iron are noted in the text and
in Table 2. NCDENR should either require that the Groundwater Assessment Work Plan
be expanded or that a separate investigation be conducted to investigate of cause of these
exceedances. A separate investigation would seem appropriate since groundwater quality
at well MW-25DR is unrelated to water quality at the CSS ash basin.
4. Section 2.3, Page 4 - Regulatory Requirements — The text indicates that monitoring
wells MW -24D and MW-24DR are considered by Duke Energy to represent background
water quality as both wells are located south of the active basin (i.e., upgradient). This
assertion must be tested before it taken as fact, no matter what Duke Energy considers a
well to represent. The need for careful evaluation of background conditions is, in this
case, acute since the work plan identifies both wells MW -24D and MW-24DR have
shown exceedances of water quality standards. Section 7.5 of the work plan should be
modified to evaluate the validity of background groundwater monitoring locations and
what unimpacted background concentration should be. See comment #14.
5. Section 7.0, Page 10 — Assessment Work Plan — One of the primary goals of
conducting the groundwater assessment must be to identify the relative positions of the
bottom elevation of disposed ash and the underlying water table. Identification of the
relative positions of the bottom of disposed ash and the underlying water table in each
ash basin or storage area will have a significant impact on the potential effectiveness of
various closure scenarios.
6. Section 7.0, Page 10 — Assessment Work Plan — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that an undefined sub -set of the existing monitoring wells may also
be sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the CSS site would be produced by sampling all existing wells
(compliance and voluntary) as well as the new proposed wells. The compliance and
voluntary wells were presumably installed for the purpose of evaluating site conditions in
their proximity. There is no readily apparent reason to limit the data upon which to base
future decisions.
7. Section 7.0, Page 10 — Assessment Work Plan — The work plan gives no indication that
water level elevations (impoundment water, groundwater, and surface waters) will be
identified. Multiple complete rounds of water elevation data is essential information that
32

must be collected to adequately characterize groundwater gradients and to identify
temporal and spatial variability, and will be necessary to calibrate the groundwater
model.
8. Section 7.0, Page 10 — Assessment Work Plan — Groundwater seeps identified as part
of Duke Energy's NPDES permit renewal should be sampled. However, the site should
be inspected as part of the groundwater assessment in order identify seeps that may not
have been identified in Duke's submittal. Any additional seeps identified during this
inspection should be included in the list of groundwater seeps for sampling.
9. Section 7.1.2, Page 11 - Proposed Soil and Ash Sampling Locations and Depths —
Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin or storage area.
At least one of the borings in each ash basin and storage area must be advanced at the
location expected to be located above the lowest point of disposed ash within each.
Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios. See comment #4.
10. Section 7.1.2, Page 11 - Constituent Sampling and Analyses - The constituent
sampling and analyses discussion indicates that soil and ash samples will be analyzed for
the parameters listed on Table 4. The list of analytical parameters on Table 4 is missing
several common ash -related parameters. Specifically, Table 4 should be modified to add
molybdenum, cobalt, hexavalent chromium, uranium, and radium. These parameters are
often found at elevated concentrations in coal ash and should be included to produce a
thorough assessment. The potential presence or concentration of these constituents will
never be known unless they are included on the list of required analytes.
11. Section 7.2, Page 12 — Groundwater Sampling Plan — The work plan calls for water
table and deep (bedrock) monitoring wells to be constructed within ash storage units and
basins to characterize pore water chemistry within the ash. Wells screened within the
waste, at or near the bottom of each ash basin and storage area, are critically needed to
characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in coal ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
evaluating the water table elevation within the ash, water table wells will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin the concentration of ash -related constituents at the water
table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
33

12. Section 7.2, Page 13 — Groundwater Sampling Plan — The description of the BG -
series wells indicates that compliance wells MW-30S/D and MW-32S/D are considered
to be background at this time. It is inappropriate to designate any well as representing
background conditions before an evaluation of background conditions has been
completed. See comment #3.
13. Section 7.2.3, Page 14 — Groundwater Sampling — The discussion indicates that only
newly installed wells will be sampled. A more complete evaluation of groundwater
chemistry would be produced by installing all existing wells (compliance and voluntary)
as well as the newly installed wells. There is no indication why previously existing wells
are not planned to be sampled as part of this assessment.
14. Section 7.2.3, Page 14 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 5. The list of analytical parameters on Table 5 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 5 should be modified to add molybdenum, cobalt,
hexavalent chromium, uranium, and radium. These parameters are often found at
elevated concentrations in ash leachate and should be included to produce a thorough
assessment. The potential presence of these constituents will never be known unless they
are included on the list of required analytes.
15. Section 7.3.1, Page 14 — Ash Basin Surface Water Samples — Collection and analysis
of ash basin water samples will likely be more representative of the quality of water that
is discharged through the permitted outfall rather than the leachate that is the source of
groundwater contamination. We have no objection to collecting ash basin water samples,
but the results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model. See comment #10.
16. Section 7.3.2, Page 14 — Seep Samples — In addition to sampling, the location and
elevation of each seep should be determined. Seep location and elevation may be useful
in constructing and calibrating the groundwater model.
17. Section 7.5, Page 15 — Site -Specific Background Concentrations — The site-specific
background concentrations evaluation is obviously intended to investigate potential ways
to explain away exceedances of groundwater quality standards to naturally occurring
conditions or problems with sample collection methodology. This section of the work
plan should be modified to require evaluation of the validity of background groundwater
monitoring locations and what unimpacted background concentration should be. This
evaluation should consider more than the relationship between groundwater standard
exceedances and turbidity, or argue that high concentration of ash -related constituents are
naturally occurring in the groundwater. It should investigate whether historic high ash
basin water levels may have provided sufficient hydraulic head to reverse gradients and
drive flow away from the impoundments in the previously upgradient direction. If water
in the impoundments is or was sufficiently high reverse natural gradients, the previous
and planned sampling could be detecting ash -related contaminants that are or were
M

9 Id.
migrating in what would be expected to be upgradient under natural conditions. Use of
impacted analyses from wells erroneously assumed to represent background conditions
would skew subsequent statistical evaluations.
18. Section 7.6, Page 15 — Groundwater Model — The groundwater model discussion
indicates that several different pieces of information will be used to establish the source
term used in the model. None of the identified data sources include data collected from
monitoring wells installed in as near the base of the ash. It is imperative that realistic
source term data be developed during the groundwater assessment to input into the
model. The discussion indicates that the source term will be developed from leach tests
and total metals analysis, analysis of groundwater or surface water samples collected
outside the basin, analysis of water table wells screened within the ash, and data from
other sites. Each of the proposed data sources is problematic.
The discussion and footnote included in Table 4 indicate that the Synthetic Precipitation
Leaching Procedure (SPLP) testing will be conducted on ash samples to evaluate
leaching potential. Application of short duration, low solid -ratio (dilute) leaching tests
like the SPLP test routinely underestimate the concentration of contaminants in flyash-
derived leachates. The procedure does not allow ash constituents sufficient time to come
into equilibrium with the fluid, the solid -water ratio is far more dilute than under disposal
conditions, and the laboratory conditions do not represent the disposal conditions under
which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings9. These tests were not designed or intended to
represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by installing monitoring points at
the base of the disposed ash as described in comment #10.
The discussion indicates that analytical results from groundwater monitoring wells or
surface water sample locations outside of the basin might be used to develop
concentration source terms. These analyses suffer from the obvious limitations of having
already been release from the basins and being diluted in flowing groundwater or surface
water, and interacting with aquifer materials prior to analyses. The limitations of
establishing source term concentrations using SPLP tests can be readily avoided by
installing monitoring points at the base of the disposed ash as described in comment #10.
The limitations of using ash basin pore water analyses from wells installed across the
water table within the basin was previously addressed in comment #10. Use of published
or other data from leach tests conducted at other facilities would not be site-specific and
would likely be limited by the common industry practice of using the same outmoded
35

tests as were proposed in Table 4. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by installing monitoring points at
the base of the disposed ash as described in comment #10.
When completed, the groundwater model should be used to investigate changes to
hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Marshall
Section 2.3, Page 3 - Regulatory Requirements — Unlike other reviewed groundwater
assessment work plans submitted by Duke Energy, the Marshall work plan does not
indicate that background monitoring wells currently exist. It is unclear how a NCDENR-
approved compliance monitoring program has functioned without information about
background groundwater quality. The need for careful evaluation of background
conditions is especially important since the work plan indicates that many wells have
shown exceedances of water quality standards.
2. Section 7.0, Page 9 — Assessment Work Plan — One of the primary goals of conducting
the groundwater assessment must be to identify the relative positions of the bottom
elevation of disposed ash and the underlying water table. Identification of the relative
positions of the bottom of disposed ash and the underlying water table in each ash basin
or storage area will have a significant impact on the potential effectiveness of various
closure scenarios.
3. Section 7.0, Page 10 — Assessment Work Plan — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that an undefined sub -set of the existing monitoring wells may also
be sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the site would be produced by sampling all existing wells
(compliance, landfill and voluntary) as well as the new proposed wells. Collection of
data from the landfill monitoring wells located in the vicinity of the FGD Residue landfill
are particularly necessary due to the proximity of residential and Public water supply
wells located just west of the landfill and a distinct lack of new planned wells in that area.
The compliance, landfill, and voluntary wells were presumably installed for the purpose
of evaluating site conditions in their proximity. There is no readily apparent reason to
limit the data upon which to base future decisions.
4. Section 7.0, Page 10 — Assessment Work Plan — The work plan gives no indication that
water level elevations (impoundment water, groundwater, and surface waters) will be
identified. Multiple complete rounds of water elevation data is essential information that
must be collected to adequately characterize groundwater gradients, identify temporal
and spatial variability, and will be necessary to calibrate the groundwater model.
5. Section 7.1.2, Page 10 - Proposed Soil and Ash Sampling Locations and Depths —
Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin or storage area.
we

At least one of the borings in each ash basin and storage area must be advanced at the
location expected to be located above the lowest point of disposed ash within each.
Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios.
6. Section 7.1.2, Page 10 - Constituent Sampling and Analyses - The constituent
sampling and analyses discussion indicates that soil and ash samples will be analyzed for
the parameters listed on Table 4. The list of analytical parameters on Table 4 is missing
several common ash -related parameters. Specifically, Table 4 should be modified to add
molybdenum, cobalt, hexavalent chromium, uranium, and radium. These parameters are
often found at elevated concentrations in coal ash and should be included to produce a
thorough assessment. The potential presence or concentration of these constituents will
never be known unless they are included on the list of required analytes.
7. Section 7.2, Page 11— Groundwater Sampling Plan — The work plan calls for water
table and deep (bedrock) monitoring wells to be constructed within ash landfills and
basins to characterize pore water chemistry within the ash. Wells screened within the
waste, at or near the bottom of each ash basin and storage area are critically needed to
characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
evaluating the water table elevation within the ash, water table wells will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin the concentration of ash -related constituents at the water
table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
8. Section 7.2, Page 11— Groundwater Sampling Plan — The AB -series wells should be
expanded to include installation of monitoring wells in all ash landfills, including
industrial landfill and the FGD residue landfill, to evaluate the elevation of leachate in all
landfills. Mounding of leachate in landfills can have a significant effect on the direction
of groundwater flow in the vicinity of each landfill. Measurement of leachate head
within each landfill is necessary to understand groundwater flow directions across the
facility.
9. Section 7.2, Page 11— Groundwater Sampling Plan — The discussion of well OB -1
indicates that one water table well will be installed in the area for collection of water
levels only. Given the proposed location of well OB -1 between two lobes of the ash
impoundment, it is unclear why sample collection from this location is not proposed.
37

Please provide a valid rationale for not sampling this well or modify the work pan to
include this well in the sampling program.
10. Section 7.2, Page 11— Groundwater Sampling Plan — Review of the well location
map (Figure 3) referenced in this section shows that no monitoring wells are proposed for
installation in the area north of the active ash basin and industrial landfill. A pair of wells
(shallow and deep) should be installed along the property boundary north of the industrial
landfill to asses water quality north of the ash basin and identify possible impacts from
the industrial landfill.
11. Section 7.2, Page 11— Groundwater Sampling Plan — Review of the well location
map (Figure 3) referenced in this section shows that no monitoring wells are proposed for
installation in the area southwest of the active ash basin and the FGD residue landfill.
Two pairs of wells (shallow and deep) should be installed southwest of the active ash
basin. One pair should be installed between the active ash basin and the FGD residue
landfill. A second pair of wells should be installed west of the FGD residue landfill,
between the landfill and nearby water supply wells. These wells are critical additions to
the proposed monitoring system since the drinking water supply well and receptor survey
for this site indicates that groundwater is likely flowing from the FGD residue landfill
toward the property boundary and the nearby wells.
12. Section 7.2, Page 11— Groundwater Sampling Plan — The BG -series wells identified
in the work plan may be thought to be properly placed to characterize background
chemistry, but this has not been shown to be the case at this time. It is inappropriate to
designate any well as representing background conditions before an evaluation of
background conditions has been completed.
13. Section 7.2.3, Page 12 — Groundwater Sampling — The discussion indicates that only
newly installed wells will be sampled. A more complete evaluation of groundwater
chemistry would be produced by including all existing wells (compliance, landfill and
voluntary) as well as the newly installed wells. There is no indication why previously
existing wells are not planned to be sampled as part of this assessment.
14. Section 7.2.3, Page 12 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 5. The list of analytical parameters on Table 5 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 5 should be modified to add molybdenum, cobalt,
hexavalent chromium, uranium, and radium. These parameters are often found at
elevated concentrations in ash leachate and should be included to produce a thorough
assessment. The potential presence of these constituents will never be known unless they
are included on the list of required analytes.
15. Section 7.3.1, Page 14 — Ash Basin Surface Water Samples — Collection and analysis
of ash basin water samples will likely be more representative of the quality of water that
is discharged through the permitted outfall rather than the leachate that is the source of
M:

groundwater contamination. We have no objection to collecting ash basin water samples,
but the results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model.
16. Section 7.5, Page 15 — Site -Specific Background Concentrations — The site-specific
background concentrations evaluation is obviously intended to investigate potential ways
to explain away exceedances of groundwater quality standards to naturally occurring
conditions or problems with sample collection methodology. This section of the work
plan should be modified to require evaluation of the validity of background groundwater
monitoring locations and of what unimpacted background concentration should be. This
evaluation should consider more than the relationship between groundwater standard
exceedances and turbidity, or argue that high concentration of ash -related constituents are
naturally occurring in the groundwater. It should investigate whether historic high ash
basin water levels may have provided sufficient hydraulic head to reverse gradients and
drive flow away from the impoundments in the previously upgradient direction. If water
in the impoundments is or was sufficiently high to reverse natural gradients, the previous
and planned sampling could be detecting ash -related contaminants that are or were
migrating in what would be expected to be upgradient under natural conditions. Use of
impacted analyses from wells erroneously assumed to represent background conditions
would skew subsequent statistical evaluations.
17. Section 7.6, Page 15 — Groundwater Model — The groundwater model discussion
indicates that several different pieces of information will be used to establish the source
term used in the model. None of the identified data sources include data collected from
monitoring wells installed in as near the base of the ash. It is imperative that realistic
source term data be developed during the groundwater assessment to input into the
model. The discussion indicates that the source term will be developed from leach tests
and total metals analysis, analysis of groundwater or surface water samples collected
outside the basin, analysis of water table wells screened within the ash, and data from
other sites. Each of the proposed data sources is problematic.
The discussion and footnote included in Table 4 indicate that the Synthetic Precipitation
Leaching Procedure (SPLP) testing will be conducted on ash samples to evaluate
leaching potential. Application of short duration, low solid -ratio (dilute) leaching tests
like the SPLP test routinely underestimate the concentration of contaminants in flyash-
derived leachates. The procedure does not allow ash constituents sufficient time to come
into equilibrium with the fluid, the solid -water ratio is far more dilute than under disposal
conditions, and the laboratory conditions do not represent the disposal conditions under
which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings10. These tests were not designed or intended
to represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
W

Buck
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by installing monitoring points at
the base of the disposed ash as described in comment #7.
The discussion indicates that analytical results from groundwater monitoring wells or
surface water sample locations outside of the basin might be used to develop
concentration source terms. These analyses suffer from the obvious limitations of having
already been released from the basins and being diluted in flowing groundwater or
surface water, and interacting with aquifer materials prior to analyses. The limitations of
establishing source term concentrations using SPLP tests can be readily avoided by
installing monitoring points at the base of the disposed ash as described in comment #7.
The limitations of using ash basin pore water analyses from wells installed across the
water table within the basin was previously addressed in comment #7. Use of published
or other data from leach tests conducted at other facilities would not be site-specific and
would likely be limited by the common industry practice of using the same outmoded
tests as were proposed in Table 4. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by installing monitoring points at
the base of the disposed ash as described in comment #7.
When completed, the groundwater model should be used to investigate changes to
hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Section 2.3, Page 4 - Regulatory Requirements — The text indicates that monitoring
wells MW -6S and MW -61) are considered to represent background water quality. This
assertion must be tested before it taken as fact. Section 7.5 of the work plan should be
modified to evaluate the validity of background groundwater monitoring locations and
what unimpacted background concentration should be.
2. Section 7.0, Page 10 — Assessment Work Plan — One of the primary goals of
conducting the groundwater assessment must be to identify the relative positions of the
bottom elevation of disposed ash and the underlying water table. Identification of the
relative positions of the bottom of disposed ash and the underlying water table in each
ash basin or storage area will have a significant impact on the potential effectiveness of
various closure scenarios.
3. Section 7.0, Page 10 — Assessment Work Plan — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that an undefined sub -set of the existing monitoring wells may also
be sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the site would be produced by sampling all existing wells
(compliance and voluntary) as well as the new proposed wells. The compliance and
voluntary wells were presumably installed for the purpose of evaluating site conditions in

their proximity. There is no readily apparent reason to limit the data upon which to base
future decisions.
4. Section 7.0, Page 10 — Assessment Work Plan — The work plan gives no indication that
water level elevations (impoundment water, groundwater, and surface waters) will be
identified. Multiple complete rounds of water elevation data is essential information that
must be collected to adequately characterize groundwater gradients, identify temporal
and spatial variability, and will be necessary to calibrate the groundwater model.
5. Section 7.1.2, Page 11 - Proposed Soil and Ash Sampling Locations and Depths —
Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin or storage area.
At least one of the borings in each ash basin and storage area must be advanced at the
location expected to be located above the lowest point of disposed ash within each.
Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios.
6. Section 7.1.2, Page 11 - Constituent Sampling and Analyses - The constituent
sampling and analyses discussion indicates that soil and ash samples will be analyzed for
the parameters listed on Table 4 The list of analytical parameters on Table 4 is missing
several common ash -related parameters. Specifically, Table 4 should be modified to add
molybdenum, cobalt, hexavalent chromium, uranium, and radium. These parameters are
often found at elevated concentrations in coal ash and should be included to produce a
thorough assessment. The potential presence or concentration of these constituents will
never be known unless they are included on the list of required analytes.
7. Section 7.2, Page 12 — Groundwater Sampling Plan — The work plan calls for water
table and deep (bedrock) monitoring wells to be constructed within ash storage units and
basins to characterize pore water chemistry within the ash. Wells screened within the
waste, at or near the bottom of each ash basin and storage area are critically needed to
characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
evaluating the water table elevation within the ash, water table wells will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin, the concentration of ash -related constituents at the water
table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
41

8. Section 7.2, Page 11— Groundwater Sampling Plan — The BG -series wells identified
in the work plan may be thought to be properly placed to characterize background
chemistry, but this has not been shown to be the case at this time. It is inappropriate to
designate any well as representing background conditions before an evaluation of
background conditions has been completed.
9. Section 7.2.3, Page 13 — Groundwater Sampling — The discussion indicates that only
newly installed wells will be sampled. A more complete evaluation of groundwater
chemistry would be produced by including all existing wells (compliance and voluntary)
as well as the newly installed wells. There is no indication why previously existing wells
are not planned to be sampled as part of this assessment.
10. Section 7.2.3, Page 13 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 5. The list of analytical parameters on Table 5 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 5 should be modified to add molybdenum, cobalt,
hexavalent chromium, uranium, and radium. These parameters are often found at
elevated concentrations in ash leachate and should be included to produce a thorough
assessment. The potential presence of these constituents will never be known unless they
are included on the list of required analytes.
11. Section 7.3.1, Page 14 — Ash Basin Surface Water Samples — Collection and analysis
of ash basin water samples will likely be more representative of the quality of water that
is discharged through the permitted outfall rather than the leachate that is the source of
groundwater contamination. We have no objection to collecting ash basin water samples,
but the results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model.
12. Section 7.5, Page 15 — Site -Specific Background Concentrations — The site-specific
background concentrations evaluation appears to be intended to investigate potential
ways to explain away exceedances of groundwater quality standards to naturally
occurring conditions or problems with sample collection methodology. This section of
the work plan should be modified to require evaluation of the validity of background
groundwater monitoring locations and what unimpacted background concentration should
be. This evaluation should consider more than the relationship between groundwater
standard exceedances and turbidity, or argue that high concentration of ash -related
constituents are naturally occurring in the groundwater. It should investigate whether
historic high ash basin water levels may have provided sufficient hydraulic head to
reverse gradients and drive flow away from the impoundments in the previously
upgradient direction. If water in the impoundments is or was sufficiently high to reverse
natural gradients, the previous and planned sampling could be detecting ash -related
contaminants that are or were migrating in what would be expected to be upgradient
under natural conditions. Use of impacted analyses from wells erroneously assumed to
represent background conditions would skew subsequent statistical evaluations.
42

" Id.
13. Section 7.6, Page 15 — Groundwater Model — The groundwater model discussion
indicates that several different pieces of information will be used to establish the source
term used in the model. None of the identified data sources include data collected from
monitoring wells installed in as near the base of the ash. It is imperative that realistic
source term data be developed during the groundwater assessment to input into the
model. The discussion indicates that the source term will be developed from leach tests
and total metals analysis, analysis of groundwater or surface water samples collected
outside the basin, analysis of water table wells screened within the ash, and data from
other sites. Each of the proposed data sources is problematic.
The text and Table 4 indicate that the Synthetic Precipitation Leaching Procedure (SPLP)
testing will be conducted on ash samples to evaluate leaching potential. Application of
short duration, low solid -ratio (dilute) leaching tests like the SPLP test routinely
underestimate the concentration of contaminants in flyash-derived leachates. The
procedure does not allow ash constituents sufficient time to come into equilibrium with
the fluid, the solid -water ratio is far more dilute than under disposal conditions, and the
laboratory conditions do not represent the disposal conditions under which leachate will
actually form. The National Research Council warned of the inadequacy of laboratory
characterization tests as surrogates for determining field leachate composition
specifically with respect to coal ash in their investigation of coal combustion ash disposal
in mined settings 11. These tests were not designed or intended to represent predictions of
leachate that will form in the field, and to use them as such is inappropriate. Citing
results from outmoded tests that are widely acknowledged to be ineffective at predicting
leachate concentrations from saturated ash is a common industry practice that would call
into question the validity of the entire evaluation of current and potential future
environmental impacts. The limitations of establishing source term concentrations using
SPLP tests can be readily avoided by installing monitoring points at the base of the
disposed ash.
The discussion indicates that analytical results from groundwater monitoring wells or
surface water sample locations outside of the basin might be used to develop
concentration source terms. These analyses suffer from the obvious limitations of having
already been release from the basins and being diluted in flowing groundwater or surface
water, and interacting with aquifer materials prior to analyses. The limitations of
establishing source term concentrations using SPLP tests can be readily avoided by
installing monitoring points at the base of the disposed ash.
The limitations of using ash basin pore water analyses from wells installed across the
water table within the basin were previously addressed. Use of published or other data
from leach tests conducted at other facilities would not be site-specific and would likely
be limited by the common industry practice of using the same inappropriate test. The
limitations of establishing source term concentrations using SPLP tests can be readily
avoided by installing monitoring points at the base of the disposed ash.
43

When completed, the groundwater model should be used to investigate changes to
hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Belews Creek
1. Section 2.2, Page 2 — Plant Description — Figures 2 and 3 each show an area identified
as a Structural Fill located south of the Ash Basin. Please provide a description of what
was used to fill this area and how the fill was closed, if applicable. This discussion is
needed so that any potential for groundwater or surface water impacts from the structural
fill area can be factored into evaluation of the proposed groundwater assessment.
2. Section 2.2, Page 2 — Ash Basin Description — The work plan shows that a permitted
ash landfill is located on the southwest corner of the facility, but no construction, closure,
or monitoring information is provided. This landfill is located in the vicinity, and
potentially upgradient, of existing and planned monitoring wells and soil borings
described in the work plan. The work plan should provide a description of landfill
construction and closure along with identification of groundwater monitoring so that
potential effects of the landfill on existing and planned groundwater monitoring wells can
be evaluated.
3. Section 2.3, Page 4 - Regulatory Requirements — The text indicates that monitoring
wells MW -202S and MW -202D are considered to represent background water quality.
This assertion must be tested before it taken as fact, this is especially true since the wells
appear to potentially be located downgradient of the Pine Hall Road Ash Landfill, and
exceedances of 2L standards have been reported in MW -2021). Section 7.5 of the work
plan should be modified to evaluate the validity of background groundwater monitoring
locations and what unimpacted background concentrations should be.
4. Section 7.0, Page 10 — Assessment Work Plan — One of the primary goals of
conducting the groundwater assessment must be to identify the relative positions of the
bottom elevation of disposed ash and the underlying water table. Identification of the
relative positions of the bottom of disposed ash and the underlying water table in each
ash basin or storage area will have a significant impact on the potential effectiveness of
various closure scenarios.
5. Section 7.0, Page 10 — Assessment Work Plan — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that an undefined sub -set of the existing monitoring wells may also
be sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the site would be produced by sampling all existing wells
(compliance and voluntary) as well as the new proposed wells. The compliance and
voluntary wells were presumably installed for the purpose of evaluating site conditions in
their proximity. There is no readily apparent reason to limit the data upon which to base
future decisions.

6. Section 7.0, Page 10 — Assessment Work Plan — The work plan gives no indication
that water level elevations (impoundment water, groundwater, and surface waters) will be
identified. Multiple complete rounds of water elevation data is essential information that
must be collected to adequately characterize groundwater gradients, identify temporal
and spatial variability, and will be necessary to calibrate the groundwater model.
7. Section 7.1.29 Page 11 - Proposed Soil and Ash Sampling Locations and Depths —
Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin or storage area.
At least one of the borings in each ash basin and storage area must be advanced at the
location expected to be located above the lowest point of disposed ash within each.
Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios.
8. Section 7.1.2, Page 11 - Proposed Soil and Ash Sampling Locations and Depths —
Since the work plan provides no description of the ash landfill or structural fill areas, we
are apparently supposed to take it as an article of faith that there is no reason that these
areas may be potential sources of groundwater contaminants and no investigation of these
areas as possible sources will be necessary. Please provide enough information about the
ash landfill and structural fill areas that the need for sampling in and around these areas
can be evaluated.
9. Section 7.1.2, Page 11 - Constituent Sampling and Analyses - The constituent
sampling and analyses discussion indicates that soil and ash samples will be analyzed for
the parameters listed on Table 4 The list of analytical parameters on Table 4 is missing
several common ash -related parameters. Specifically, Table 4 should be modified to add
molybdenum, cobalt, hexavalent chromium, uranium, and radium. These parameters are
often found at elevated concentrations in coal ash and should be included to produce a
thorough assessment. The potential presence or concentration of these constituents will
never be known unless they are included on the list of required analytes.
10. Section 7.2, Page 12 — Groundwater Sampling Plan — The work plan calls for water
table and deep (bedrock) monitoring wells to be constructed within ash storage units and
basins to characterize pore water chemistry within the ash. Wells screened within the
waste, at or near the bottom of each ash basin and storage area, are critically needed to
characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
evaluating the water table elevation within the ash, water table wells will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin, the concentration of ash -related constituents at the water
45

table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
11. Section 7.2, Page 11— Groundwater Sampling Plan — The BG -series wells identified
in the work plan may be thought to be properly placed to characterize background
chemistry, but this has not been shown to be the case at this time. It is inappropriate to
designate any well as representing background conditions before an evaluation of
background conditions has been completed.
12. Section 7.2.1, Page 13 — Well Installation and Development — The discussion
indicates that only newly installed wells will be sampled. A more complete evaluation of
groundwater chemistry would be produced by including all existing wells (compliance
and voluntary) as well as the newly installed wells. There is no indication why
previously existing wells are not planned to be sampled as part of this assessment.
13. Section 7.2.3, Page 13 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 5. The list of analytical parameters on Table 5 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 5 should be modified to add molybdenum, cobalt,
hexavalent chromium, uranium, and radium. These parameters are often found at
elevated concentrations in ash leachate and should be included to produce a thorough
assessment. The potential presence of these constituents will never be known unless they
are included on the list of required analytes.
14. Section 7.3.1, Page 14 — Ash Basin Surface Water Samples — Collection and analysis
of ash basin water samples will likely be more representative of the quality of water that
is discharged through the permitted outfall rather than the leachate that is the source of
groundwater contamination. We have no objection to collecting ash basin water samples,
but the results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model.
15. Section 7.5, Page 15 — Site -Specific Background Concentrations — The site-specific
background concentrations evaluation appears to be intended to investigate potential
ways to explain away exceedances of groundwater quality standards to naturally
occurring conditions or problems with sample collection methodology. This section of
the work plan should be modified to require evaluation of the validity of background
groundwater monitoring locations and what unimpacted background concentration should
be. This evaluation should consider more than the relationship between groundwater
standard exceedances and turbidity, or argue that high concentration of ash -related
constituents are naturally occurring in the groundwater. It should investigate whether
historic high ash basin water levels may have provided sufficient hydraulic head to
reverse gradients and drive flow away from the impoundments in the previously
upgradient direction. If water in the impoundments is or was sufficiently high to reverse
natural gradients, the previous and planned sampling could be detecting ash -related
we

12 Id.
contaminants that are or were migrating in what would be expected to be upgradient
under natural conditions. Use of impacted analyses from wells erroneously assumed to
represent background conditions would skew subsequent statistical evaluations.
16. Section 7.6, Page 15 — Groundwater Model — The groundwater model discussion
indicates that several different pieces of information will be used to establish the source
term used in the model. None of the identified data sources include data collected from
monitoring wells installed in as near the base of the ash. It is imperative that realistic
source term data be developed during the groundwater assessment to input into the
model. The discussion indicates that the source term will be developed from leach tests
and total metals analysis, analysis of groundwater or surface water samples collected
outside the basin, analysis of water table wells screened within the ash, and data from
other sites. Each of the proposed data sources is problematic.
The text and Table 4 indicate that the Synthetic Precipitation Leaching Procedure (SPLP)
testing will be conducted on ash samples to evaluate leaching potential. Application of
short duration, low solid -ratio (dilute) leaching tests like the SPLP test routinely
underestimate the concentration of contaminants in flyash-derived leachates. The
procedure does not allow ash constituents sufficient time to come into equilibrium with
the fluid, the solid -water ratio is far more dilute than under disposal conditions, and the
laboratory conditions do not represent the disposal conditions under which leachate will
actually form. The National Research Council warned of the inadequacy of laboratory
characterization tests as surrogates for determining field leachate composition
specifically with respect to coal ash in their investigation of coal combustion ash disposal
in mined settings 12. These tests were not designed or intended to represent predictions of
leachate that will form in the field, and to use them as such is inappropriate. Citing
results from outmoded tests that are widely acknowledged to be ineffective at predicting
leachate concentrations from saturated ash is a common industry practice that would call
into question the validity of the entire evaluation of current and potential future
environmental impacts. The limitations of establishing source term concentrations using
SPLP tests can be readily avoided by installing monitoring points at the base of the
disposed ash.
The discussion indicates that analytical results from groundwater monitoring wells or
surface water sample locations outside of the basin might be used to develop
concentration source terms. These analyses suffer from the obvious limitations of having
already been release from the basins and being diluted in flowing groundwater or surface
water, and interacting with aquifer materials prior to analyses. The limitations of
establishing source term concentrations using SPLP tests can be readily avoided by
installing monitoring points at the base of the disposed ash.
The limitations of using ash basin pore water analyses from wells installed across the
water table within the basin were previously addressed. Use of published or other data
from leach tests conducted at other facilities would not be site-specific and would likely
be limited by the common industry practice of using the same inappropriate test. The
47

limitations of establishing source term concentrations using SPLP tests can be readily
avoided by installing monitoring points at the base of the disposed ash.
When completed, the groundwater model should be used to investigate changes to
hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Weatherspoon
Section 1.0, Page 1 - Introduction — The text indicates that a existing background
monitoring well BW -I is located upgradient of the ash basin. The designation as a
background well must be tested before it is taken as fact. Evaluation of unimpacted
groundwater chemistry is particularly important since the identified "background"
monitoring well has shown concentrations of ash -related parameters in concentrations
above the 2L standard and the well lies within the potential area of interest identified in
the Drinking Water Well and Receptor Survey. The elevation of water in the ash basin
during coal plant operations may have been sufficiently above the surrounding area that
groundwater flowed radially away from the impoundments, effectively transporting ash
basin contaminants toward the "background wells". This mechanism could reasonably be
expected to transport ash -related contaminants in groundwater away from the
impoundments and account for the exceedances of 2L groundwater standards at the
background well noted in Table 1.
2. Section 1.0, Page 2 — Introduction — One of the primary goals of conducting the
groundwater assessment must be to identify the relative positions of the bottom elevation
of disposed ash and the underlying water table. Identification of the relative positions of
the bottom of disposed ash and the water table in each ash basin or storage area will have
a significant impact on the potential effectiveness of various closure scenarios.
3. Section 2.3, Page 3 — Groundwater Monitoring System - The work plan identifies one
well thought to be properly placed to characterize background chemistry, but this has not
been shown to be the case at this time. It is inappropriate to designate any well as
representing background conditions before an evaluation of background conditions has
been completed. Evaluation of background should investigate whether historic high ash
basin water levels may have provided sufficient hydraulic head to reverse gradients and
drive flow away from the impoundments in the previously upgradient direction. If water
in the impoundments is or was sufficiently high to reverse natural gradients, the previous
and planned sampling could be detecting ash -related contaminants that are or were
migrating in what would be expected to be upgradient under natural conditions. New
background monitoring wells may or may not show similar concentrations to the existing
wells. Use of impacted analyses from wells erroneously assumed to represent
background conditions would skew subsequent statistical evaluations.
4. Section 5.0, Page 10 — Site Geology and Hydrogeology — The discussion of
groundwater gradients does not reflect the influence of ash basin water on groundwater
flow direction in the proximity of the basins. Infiltration of water from the impoundment
and into the groundwater may have created mounding in the area causing radial flow

away from the impoundment. The elevation of groundwater in the impoundments must
be established and compared to surrounding water elevations in order to establish the
local groundwater gradient in the vicinity of the impoundments.
5. Section 6.1, Page 11 — Preliminary Statistical Evaluation Results — The inter -well
statistical evaluation discussed in this section compares concentrations of ash -related
constituents in compliance wells to concentrations measured in existing "background"
wells. As was previously discussed, the existing wells currently identified as background
have not been evaluated to show that they are actually representative of unimpacted
groundwater quality. Detections of various parameters in this well at concentrations
above the 2L standards are a potential indication that unimpacted background conditions
are not being used in this analysis. The statistical evaluation needs to be repeated once
unimpacted background water quality has been identified.
6. Section 7.1., Page 12 - Anticipated Soil Basin Boring Locations — Please verify
through review of construction records or pre -development topography where the lowest
elevation ash is expected to be located in each ash basin or storage area. At least one of
the borings in each ash basin and storage area must be advanced at the location expected
to be located above the lowest point of disposed ash within each. Identification of the
relative positions of the bottom elevation of disposed ash and the underlying water table
is critical in evaluating the effectiveness of possible closure scenarios.
7. Section 7.1., Page 13 - Anticipated Ash Basin Boring Locations — The discussion in
this section and Table 3 each indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples. The intended use of these samples is
not clear from the discussion but it must be made clear from the onset that SPLP results
cannot be used to approximate the source term for ash basin leachate concentrations in
the groundwater model. Application of short duration, low solid -ratio (dilute) leaching
tests like the SPLP test routinely underestimate the concentration of contaminants in
flyash-derived leachates. The procedure does not allow ash constituents sufficient time
to come into equilibrium with the fluid, the solid -water ratio is far more dilute than under
disposal conditions, and the laboratory conditions do not represent the disposal conditions
under which leachate will actually form. The National Research Council warned of the
inadequacy of laboratory characterization tests as surrogates for determining field
leachate composition specifically with respect to coal ash in their investigation of coal
combustion ash disposal in mined settings 13. These tests were not designed or intended
to represent predictions of leachate that will form in the field, and to use them as such is
inappropriate. Citing results from outmoded tests that are widely acknowledged to be
ineffective at predicting leachate concentrations from saturated ash is a common industry
practice that would call into question the validity of the entire evaluation of current and
potential future environmental impacts. The limitations of establishing source term
concentrations using SPLP tests can be readily avoided by measuring ash pore water
concentrations by installing and sampling monitoring wells set at the base of the disposed
ash. While useful for evaluating the water table elevation within the ash, water table
wells will not provide the source concentration information needed to adequately model
13 Id.
•

migration of contaminants from the site. In an ash basin the concentration of ash -related
constituents at the water table will more closely resemble the chemistry of water
discharged through the NPDES permitted outfall than the chemistry of groundwater that
is likely to migrate out of the facility and into groundwater.
8. Section 7.2.1, Page 13 — Inside Ash Basins — The work plan should require that each of
the ash basin soil borings be completed as monitoring wells or piezometers. Completion
of the ash borings as piezometers would facilitate determination of the elevation of
leachate and groundwater, within and below the impoundment, at very little cost since the
borehole will already be present.
9. Section 7.3, Page 14 — Anticipated Sediment and Surface Water Locations — Prior to
initiating field work the existing seep sampling information should be reviewed to verify
that all identified seeps have been accurately located, the elevation of the seep has been
determined, and that analytical data include all parameters required by the work plan for
groundwater samples. In the event that all of these pieces of information do not exist, the
seeps should be sampled as part of this investigation.
10. Section 7.4.2, Page 16 — Background Wells — Both the existing and new wells should be
evaluated before the designation as background is taken as fact. This section indicates
for the first time that the existing background well might be impacted by metals that are
migrating from a nearby used auto parts junkyard. No information about the location of
the junkyard or how its potential impact on monitoring well BW -1 will be evaluated are
provided. The goal of new background wells should be to determine what unimpacted
groundwater chemistry should be. Retaining assumed background wells that are actually
impacted by ash basin leachate or other sources would skew statistical comparisons of
background and downgradient wells.
11. Section 7.4.3, Page 17 — Ash Basin Areas — The work plan indicates that a number of
piezometers and monitoring wells are present in and around the ash basin. Please review
the information on the previously installed ash basin wells and verify that at least one
existing well is screened near the base of the ash. Wells screened within the waste, at or
near the bottom of the ash basin and storage area, are critically needed to characterize the
concentration of ash -related constituents in leachate that is migrating from the facility.
Leachate concentrations in ash storage areas and basins typically increase with depth.
Leachate at or near the bottom of the impoundment or landfill has migrated through the
waste column and had sufficient contact time to come into chemical equilibrium with the
waste matrix. The chemical composition of leachate collected from the bottom of the ash
basins and storage areas will more realistically represent the chemistry of leachate that is
leaving the units to migrate with groundwater and must be used in developing the source
term for input to the groundwater model.
12. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater assessment work
plan indicates that groundwater samples will be collected but does not specify that all
new and existing wells will be included. The most complete evaluation of groundwater
quality at the site would be produced by sampling all existing wells as well as the new
proposed wells. The existing wells were presumably installed for the purpose of
50

evaluating site conditions in their proximity. There is no readily apparent reason to limit
the data upon which to base future decisions. Water levels in all site wells, piezometers
and impoundments should be collected in one day rather than over a period of days as
sampling is being done.
13. Section 7.4.5, Page 17 — Groundwater Sampling — The groundwater sampling
discussion indicates that groundwater samples will be analyzed for the parameters listed
on Table 2. The list of analytical parameters on Table 2 is essentially the parameter list
required by the facility's NPDES permit with a few added general water quality
parameters. The proposed parameter list is missing several common ash -related
parameters. Specifically, Table 2 should be modified to add cobalt, hexavalent
chromium, uranium, and radium. These parameters are often found at elevated
concentrations in ash leachate and should be included to produce a thorough assessment.
The potential presence of these constituents will never be known unless they are included
on the list of required analytes.
14. Section 7.7, Page 18 — Development of Groundwater Computer Model— The
groundwater model discussion provides no indication of information that will be used to
establish the source term used in the model. The plan includes no provision for data
collected from monitoring wells installed in as near the base of the ash. It is imperative
that realistic source term data be developed during the groundwater assessment to input
into the model. The discussion does indicate that SPLP leach tests will be conducted on
samples of ash and underlying soils collected during the investigation. The limitations of
using SPLP test results to estimate leachate source terms were discussed in Comment #7.
The work plan indicates that soil samples will be collected immediately below the ash
and at the bottom of the inside ash borings, neither of which will provide data about the
chemistry of pore water within the ash at the bottom of the impoundments. The need for
collecting pore water samples from wells set at the base of the ash fill was discussed in
comment #11.
The elevation water in the ponds is likely to have varied over time so that current
conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
groundwater model, once constructed, should be used to re-evaluate the direction
groundwater flow and areas of potential concern using historic pond water elevations.
Dan River
1. Section 2.3, Page 4- Regulatory Requirements — The text indicates that monitoring
well MW -23D is considered to represent background water quality. This assertion must
be tested before it may be taken as fact. The need for careful evaluation of background
conditions is especially important since the work plan indicates that the well has shown
exceedances of water quality standards and the Drinking Water Well and Receptor
Survey shows estimated groundwater flow directions from the ash management areas
toward MW -23D. The proposed location of proposed background wells BG-5S/D are
similarly indicated to be downgradient of potential source areas including the closed
51

LCID landfill. This section as well as section 7.5 of the work plan should be modified to
indicate that the validity of background groundwater monitoring locations will be
evaluated and unimpacted background concentrations will be determined. Water quality
from impacted wells identified as background must not be used in calculation of site-
specific background water quality concentrations.
2. Section 6.0, Page 9 — Groundwater Monitoring Results — The text indicates that a data
report previously prepared by AMEC will be considered during the groundwater
assessment. With no prior knowledge of the contents of that report, we cannot evaluate
the applicability of that data. Please provide a summary of the data from the AMEC
report that will be used in this evaluation.
3. Section 7.0, Page 10 — Assessment Work Plan — One of the primary goals of
conducting the groundwater assessment must be to identify the relative positions of the
bottom elevation of disposed ash and the underlying water table. Identification of the
relative positions of the bottom of disposed ash and the underlying water table in each
ash basin or storage area will have a significant impact on the potential effectiveness of
various closure scenarios such as capping in place.
4. Section 7.0, Page 10 — Assessment Work Plan — The description of the assessment
work plan indicates that groundwater samples will be collected from the proposed
monitoring wells and that an undefined sub -set of the existing monitoring wells may also
be sampled to supplement groundwater quality data. The most complete evaluation of
groundwater quality at the site would be produced by sampling all existing wells
(compliance, voluntary, and ash basin closure) as well as the new proposed wells. The
compliance and voluntary wells were presumably installed for the purpose of evaluating
site conditions in their proximity. There is no readily apparent reason to limit the data
upon which to base future decisions.
5. Section 7.0, Page 10 — Assessment Work Plan — Collection and analysis of ash basin
water samples will likely be more representative of the quality of water that is discharged
through the permitted outfall rather than the leachate that is the source of groundwater
contamination. We have no objection to collecting ash basin water samples, but the
results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model.
6. Section 7.0, Page 10 — Assessment Work Plan — The work plan gives no indication that
water level elevations (impoundment water, groundwater, and surface waters) will be
identified. Multiple complete rounds of water elevation data is essential information that
must be collected to adequately characterize groundwater gradients, identify temporal
and spatial variability, and will be necessary to calibrate the groundwater model.
7. Section 7.1.2, Page 11 - Proposed Soil and Ash Sampling Locations and Depths —
Please verify through review of construction records or pre -development topography
where the lowest elevation ash is expected to be located in each ash basin and storage
area. At least one of the borings in each ash basin and storage area must be advanced at
the location expected to be located above the lowest point of disposed ash within each.
52

Identification of the relative positions of the bottom elevation of disposed ash and the
underlying water table is critical in evaluating the effectiveness of possible closure
scenarios.
8. Section 7.1.2, Page 11 - Constituent Sampling and Analyses - The discussion and
footnote included in Table 5 indicate that the Synthetic Precipitation Leaching Procedure
(SPLP) testing will be conducted on ash samples to evaluate leaching potential.
Application of short duration, low solid -ratio (dilute) leaching tests like the SPLP test
routinely underestimate the concentration of contaminants in flyash-derived leachates.
The procedure does not allow ash constituents sufficient time to come into equilibrium
with the fluid, the solid -water ratio is far more dilute than under disposal conditions, and
the laboratory conditions do not represent the disposal conditions under which leachate
will actually form. The National Research Council warned of the inadequacy of
laboratory characterization tests as surrogates for determining field leachate composition
specifically with respect to coal ash in their investigation of coal combustion ash disposal
in mined settings 14. These tests were not designed or intended to represent predictions of
leachate that will form in the field, and to use them as such is inappropriate. Citing
results from outmoded tests that are widely acknowledged to be ineffective at predicting
leachate concentrations from saturated ash is a common industry practice that would call
into question the validity of the entire evaluation of current and potential future
environmental impacts.
9. Section 7.2, Page 11— Groundwater Sampling Plan — The work plan calls for water
table and deep (bedrock) monitoring wells to be constructed within ash storage units and
basins to characterize water chemistry within and beneath the ash. Wells screened within
the waste, at or near the bottom of each ash basin and storage area are critically needed to
characterize the concentration of ash -related constituents in leachate that is migrating
from the facility. Leachate concentrations in ash storage areas and basins typically
increase with depth. Leachate at or near the bottom of the impoundment or landfill has
migrated through the waste column and had sufficient contact time to come into chemical
equilibrium with the waste matrix. The chemical composition of leachate collected from
the bottom of the ash basins and storage areas will more realistically represent the
chemistry of leachate that is leaving the units to migrate with groundwater and must be
used in developing the source term for input to the groundwater model. While useful for
evaluating the water table elevation within the ash, water table wells will not provide the
source concentration information needed to adequately model migration of contaminants
from the site. In an ash basin the concentration of ash -related constituents at the water
table will more closely resemble the chemistry of water discharged through the NPDES
permitted outfall than the chemistry of groundwater that is likely to migrate out of the
facility and into groundwater.
'4 Id.
10. Section 7.2, Page 12 — Groundwater Sampling Plan — The BG -series wells identified
in the work plan may be thought to be properly placed to characterize background
chemistry, but this has not been shown to be the case at this time. It is inappropriate to
designate any well as representing background conditions before an evaluation of
53

background conditions has been completed. The need for careful evaluation of
background conditions is especially important since the work plan indicates that the well
has shown exceedances of water quality standards and the Drinking Water Well and
Receptor Survey shows estimated groundwater flow directions from the ash management
areas toward MW -23D. The proposed location of proposed background wells BG-5S/D
are similarly indicated to be downgradient of potential source areas including the closed
LCID landfill. Water quality from impacted wells identified as background must not be
used in calculation of site-specific background water quality concentrations.
11. Section 7.2.3, Page 13 — Groundwater Sampling - The constituent sampling and
analyses discussion indicates that soil and ash samples will be analyzed for the
parameters listed on Table 5. However, the list of analytical parameters on Table 5 is
missing several common ash -related parameters. Specifically, Table 5 should be
modified to add molybdenum, cobalt, hexavalent chromium, uranium, and radium. These
parameters are often found at elevated concentrations in coal ash and should be included
to produce a thorough assessment. The potential presence or concentration of these
constituents will never be known unless they are included on the list of required analytes.
12. Section 7.2.3, Page 12 — Groundwater Sampling — The discussion indicates that only
newly installed wells will be sampled. A more complete evaluation of groundwater
chemistry would be produced by including all existing wells (compliance, voluntary, and
ash basin closure) as well as the newly installed wells. There is no indication why
previously existing wells are not planned to be sampled as part of this assessment.
13. Section 7.3.1, Page 14 — Ash Basin Surface Water Samples — Collection and analysis
of ash basin water samples will likely be more representative of the quality of water that
is discharged through the permitted outfall rather than the leachate that is the source of
groundwater contamination. We have no objection to collecting ash basin water samples,
but the results of these analyses cannot be interpreted to represent the source term used in
developing the groundwater model.
14. Section 7.5, Page 14 — Site -Specific Background Concentrations — The site-specific
background concentrations evaluation appears intended to investigate potential ways to
explain away exceedances of groundwater quality standards as the result of naturally
occurring conditions or problems with sample collection methodology. This section of
the work plan should be modified to require evaluation of the validity of background
groundwater monitoring locations and what unimpacted background concentrations
should be. This evaluation should consider more than the relationship between
groundwater standard exceedances and turbidity, or argue that high concentrations of ash -
related constituents are naturally occurring in the groundwater. It should investigate
whether historic high ash basin water levels or leachate levels in ash storage areas may
have provided sufficient hydraulic head to reverse gradients and drive flow away from
the impoundments in the previously upgradient direction. If water in the impoundments
or storage areas is or was sufficiently high to reverse natural gradients, the previous and
planned sampling could be detecting ash -related contaminants that are or were migrating
in what would be expected to be upgradient under natural conditions. Use of impacted
54

1s Id.
analyses from wells erroneously assumed to represent background conditions would skew
subsequent statistical evaluations.
15. Section 7.5, Page 15 — Site -Specific Background Concentrations — In the event that
the evaluation of site-specific background concentrations shows that sample turbidity is
correlated to analyte concentration, the well must be re -developed to remove excess
turbidity and re -sampled. Use of data from inadequately developed monitoring wells in
the background data set will inappropriately skew subsequent statistical evaluations.
Background concentration ranges must reflect concentration of analytes in groundwater
and not be reflective of variations in well development.
16. Section 7.6, Page 15 — Groundwater Model - The groundwater model discussion
indicates that several different pieces of information will be used to establish the source
term used in the model. None of the identified data sources include data collected from
monitoring wells installed near the base of the ash. It is imperative that realistic source
term data be developed during the groundwater assessment to input into the model. The
discussion indicates that the source term will be developed from leach tests and total
metals analysis, analysis of groundwater or surface water samples collected outside the
basin, analysis of water table wells screened within the ash, and data from other sites.
Each of the proposed data sources is problematic.
The text and Table 4 indicate that the Synthetic Precipitation Leaching Procedure (SPLP)
testing will be conducted on ash samples to evaluate leaching potential. Application of
short duration, low solid -ratio (dilute) leaching tests like the SPLP test routinely
underestimate the concentration of contaminants in flyash-derived leachates. The
procedure does not allow ash constituents sufficient time to come into equilibrium with
the fluid, the solid -water ratio is far more dilute than under disposal conditions, and the
laboratory conditions do not represent the disposal conditions under which leachate will
actually form. The National Research Council warned of the inadequacy of laboratory
characterization tests as surrogates for determining field leachate composition
specifically with respect to coal ash in their investigation of coal combustion ash disposal
in mined settings 15. These tests were not designed or intended to represent predictions of
leachate that will form in the field, and to use them as such is inappropriate. Citing
results from inappropriate tests that are widely acknowledged to be ineffective at
predicting leachate concentrations from saturated ash is a common industry practice that
would call into question the validity of the entire evaluation of current and potential
future environmental impacts. The limitations of establishing source term concentrations
using SPLP tests can be readily avoided by installing and sampling monitoring wells at
the base of the disposed ash as.
The discussion indicates that analytical results from groundwater monitoring wells or
surface water sample locations outside of the basin might be used to develop
concentration source terms. These analyses suffer from the obvious limitation that the
water has already been released from the basins and has been diluted by groundwater or
surface water. The limitations of establishing source term concentrations using SPLP
55

tests can be readily avoided by installing monitoring points at the base of the disposed
ash.
The limitations of using ash basin pore water analyses from wells installed across the
water table within the basin were previously addressed. Use of published or other data
from leach tests conducted at other facilities would not be site-specific and would likely
be limited by the common industry practice of using the same inappropriate test. The
limitations of establishing source term concentrations using SPLP tests can be readily
avoided by installing monitoring points at the base of the disposed ash.
When completed, the groundwater model should be used to investigate changes to
hydraulic gradients caused by historic high basin water levels as well as current low
water levels.
Drinking Water Well and Receptor Survey Comments
Cape Fear
Section 3.4, Page 4 — Groundwater Flow Direction Determination Results — The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded. The discussion of groundwater flow direction is based
on a limited set of water level readings in the existing compliance and voluntary
monitoring wells. The elevation of water in the ponds is likely to have varied over time
so that current conditions may not be representative of earlier conditions. Historic pond
water elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest.
Riverbend
Mayo
Section 4.3, Page 13 — Groundwater Flow Directions — The discussion of
groundwater flow direction is based on a very limited set of water level readings in the
compliance and voluntary monitoring wells and current approximate ash basin pond
elevation data. The elevation of water in the ponds is likely to have varied over time so
that current conditions may not be representative of earlier conditions. Historic pond
water elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
Section 3.4, Page 5 — Groundwater Flow Direction Determination Results — The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded. The discussion of groundwater flow direction is based
on a limited set of water level readings in the existing monitoring wells. The elevation of
56

water in the ponds is likely to have varied over time so that current conditions may not be
representative of earlier conditions. Historic pond water elevations should be reviewed
and high water elevations should be used to identify changes in hydraulic gradient that
might identify other areas of potential interest.
H.F. Lee
Section 3.4, Page 5 — Groundwater Flow Direction Determination Results — The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded. The discussion of groundwater flow direction is based
on a limited set of water level readings in the existing monitoring wells. The elevation of
water in the ponds is likely to have varied over time so that current conditions may not be
representative of earlier conditions. Historic pond water elevations should be reviewed
and high water elevations should be used to identify changes in hydraulic gradient that
might identify other areas of potential interest.
Sutton
1. Section 3.4, Page 6 — Groundwater Flow Directions — The discussion of groundwater
flow direction is based on a very limited set of water level readings in the compliance and
voluntary monitoring wells and current approximate ash basin pond elevation data. The
elevation of water in the ponds is likely to have varied over time so that current
conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
2. Section 5.0, Page 9 and Figure 3 —Summary of Findings — The findings of the
Drinking Water Well and Receptor Survey raise serious questions about public safety.
Even without evaluating the effects of groundwater pumping from nearby residential and
public water supply wells, Figure 3 indicates high confidence that the direction of
groundwater flow at the compliance boundary is toward many water supply wells.
The findings of this survey call for immediate action by NCDENR to protect the public
health and welfare. All residential wells located within the areas of potential concern
should immediately be sampled for the expanded list of ash -related parameters. All
public water supply wells within 0.5 -mile of the ash basin compliance boundary should
immediately be sampled. Any indications of potential ash impacts in a residential well
should prompt an expansion of the sampling area. Duke Energy should immediately be
directed to begin evaluating the potential effects of pumping on groundwater flow
directions and the distribution of ash -related contaminants.
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Roxboro
Section 3.4, Page 5 — Groundwater Flow Direction Determination Results — The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded. The discussion of groundwater flow direction is based
on a limited set of water level readings in the existing monitoring wells. The elevation of
water in the ponds is likely to have varied over time so that current conditions may not be
representative of earlier conditions. Historic pond water elevations should be reviewed
and high water elevations should be used to identify changes in hydraulic gradient that
might identify other areas of potential interest.
Allen
The findings of the Drinking Water Supply Well and Receptor Survey are of particular concern
at the Allen Steam Station. Residential water supply wells were found to be present within areas
of potential concern for impacts from the active ash basin. Immediate action by NCDENR is
necessary to assure that the health and welfare of residents near the Allen site are protected.
1. Section 4.3, Page 13 and Figure 3 — Groundwater Flow Directions — The findings of
the Drinking Water Well and Receptor Survey are alarming. Even without evaluating the
effects of groundwater pumping from nearby residential and public water supply wells,
Figure 3 indicates low to moderate confidence that the direction of groundwater flow at
the compliance boundary is toward the ash basins and storage areas. If fact, the northern
area of the site shows moderate confidence indications that groundwater is flowing away
from the ash storage area and across the compliance boundary. Properties with identified
residential wells are located adjacent to the active and inactive ash basins and within the
identified areas of potential concern on the west side of the active ash basin.
The findings of this survey call for immediate action by NCDENR to protect the public
health and welfare. All residential wells located within the areas of potential concern
should immediately be sampled for the expanded list of ash -related parameters. All
public water supply wells within 0.5 -mile of the ash basin compliance boundary should
immediately be sampled. Any indications of potential ash impacts in a residential well
should prompt an expansion of the sampling area. Duke Energy should immediately be
directed to begin evaluating the potential effects of pumping on groundwater flow
directions and the distribution of ash -related contaminants.
2. Section 4.3, Page 13 — Groundwater Flow Directions — The discussion of
groundwater flow direction is based on a very limited set of water level readings in the
compliance and voluntary monitoring wells and current approximate ash basin pond
elevation data. The elevation of water in the ponds is likely to have varied over time so
that current conditions may not be representative of earlier conditions. Historic pond
water elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
direction of flow and areas of potential interest should be re-evaluated using historic pond
M.

water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
Cliffside
1. Section 4.3, Page 13 — Groundwater Flow Directions — The discussion of
groundwater flow direction is based on a very limited set of water level readings in the
compliance and voluntary monitoring wells and current approximate ash basin pond
elevation data. The elevation of water in the ponds is likely to have varied over time so
that current conditions may not be representative of earlier conditions. Historic pond
water elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
2. Section 4.3, Page 13 — Groundwater Flow Directions — The effect of groundwater
pumping at residential wells, especially where there is a concentration of residential wells
has not been evaluated to date. Water wells located close to the ash basins, such as to the
southeast of the active basin, should be sampled for the expanded list of ash -related
parameters in order to establish that neither high basin water levels nor the combined
effects of residential pumping has caused contamination of the nearby wells.
Marshall
1. Section 4.3, Page 13 and Figure 3 — Groundwater Flow Directions — Even without
evaluating the effects of groundwater pumping from nearby residential and public water
supply wells, Figure 3 indicates low to moderate confidence that the direction of
groundwater flow at the compliance boundary is toward the ash basins and storage areas
on the northeast, west and southwest portions of property. The southwest area of the site
shows high confidence indications that groundwater is flowing away from the FGD
Residue Landfill in the vicinity of residential wells and a public water supply well. Two
assumed residential supply wells are located within the identified area of potential
concern. These two wells and the public water supply well located west of the FGD
landfill should be immediately sampled to evaluate potential impacts on area residents.
Groundwater elevation and analytical data from all available wells (compliance, landfill,
and voluntary) must be included in the groundwater assessment. Additional monitoring
points should be installed within and in the vicinity the FGD residue landfill to evaluate
the potential impact that the landfill may have on groundwater flow (see comment #11).
2. Section 4.3, Page 13 — Groundwater Flow Directions — The discussion of
groundwater flow direction is based on a very limited set of water level readings in the
compliance and voluntary monitoring wells and current approximate ash basin pond
elevation data. The elevation of water in the ponds is likely to have varied over time so
that current conditions may not be representative of earlier conditions. Historic pond
water elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
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direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
Buck
The findings of the Drinking Water Supply Well and Receptor Survey are of particular concern
at Buck. Residential water supply wells were found to be present very near the area of potential
interest for impacts from the Cell l ash. Immediate action by NCDENR is necessary to assure
that the health and welfare of residents near the Buck site are protected.
1. Section 4.3, Page 13 and Figure 3 — Groundwater Flow Directions — The findings of
the Drinking Water Well and Receptor Survey are of particular concern. Even without
evaluating the effects of groundwater pumping from nearby residential and public water
supply wells, Figure 3 indicates several low confidence estimates of the direction of
groundwater flow at the compliance boundary in the vicinity of residential wells on the
southwest corner of Cell 1. Properties with identified residential wells are located near
the active ash basins and adjacent to the potential area of interest on the southwest side of
the active ash basin.
The findings of this survey call for immediate action by NCDENR to protect the public
health and welfare. All residential wells located in the proximity of the potential area of
interest should immediately be sampled for the expanded list of ash -related parameters.
All public water supply wells within 0.5 -mile of the ash basin compliance boundary
should immediately be sampled. Any indications of potential ash impacts in a residential
well should prompt an expansion of the sampling area. Duke Energy should immediately
be directed to begin evaluating the potential effects of pumping on groundwater flow
directions and the distribution of ash -related contaminants.
2. Section 4.3, Page 13 — Groundwater Flow Directions — The discussion of
groundwater flow direction is based on a very limited set of water level readings in the
compliance and voluntary monitoring wells and current approximate ash basin pond
elevation data. The elevation of water in the ponds is likely to have varied over time so
that current conditions may not be representative of earlier conditions. Historic pond
water elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
Belews Creek
The findings of the Drinking Water Supply Well and Receptor Survey are of particular concern
at Belews Creek. Residential water supply wells were found to be present within and very near
the area of potential interest for impacts from the Active Ash Basin. Immediate action by
NCDENR is necessary to assure that the health and welfare of residents near the Belews site are
protected.

1. Section 4.3, Page 13 and Figure 3 — Groundwater Flow Directions — The findings of
the Drinking Water Well and Receptor Survey are concerning. Even without evaluating
the effects of groundwater pumping from nearby residential and public water supply
wells, Figure 3 shows residential wells within the potential area of interest on the
northeast corner of the site and additional residential wells located very near the area of
interest on the southwest corner of the site.
The findings of this survey call for immediate action by NCDENR to protect the public
health and welfare. All residential wells located in the proximity of the potential area of
interest should immediately be sampled for the expanded list of ash -related parameters.
All public water supply wells within 0.5 -mile of the ash basin compliance boundary
should immediately be sampled. Any indications of potential ash impacts in a residential
well should prompt an expansion of the sampling area. Duke Energy should immediately
be directed to begin evaluating the potential effects of pumping on groundwater flow
directions and the distribution of ash -related contaminants.
2. Section 4.3, Page 13 — Groundwater Flow Directions — The discussion of
groundwater flow direction is based on a very limited set of water level readings in the
compliance and voluntary monitoring wells and current approximate ash basin pond
elevation data. The elevation of water in the ponds is likely to have varied over time so
that current conditions may not be representative of earlier conditions. Historic pond
water elevations should be reviewed and high water elevation should be used to identify
changes in hydraulic gradient that might identify other areas of potential interest. The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
Weatherspoon
Section 3.4, Page 5 — Groundwater Flow Direction Determination Results — The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded. The discussion of groundwater flow direction is based
on a limited set of water level readings in the existing monitoring wells. The elevation of
water in the ponds is likely to have varied over time so that current conditions may not be
representative of earlier conditions. Historic pond water elevations should be reviewed
and high water elevations should be used to identify changes in hydraulic gradient that
might identify other areas of potential interest.
Dan River
Section 4.3, Page 13 — Groundwater Flow Directions — The discussion of
groundwater flow direction is based on a very limited set of water level readings in the
compliance and voluntary monitoring wells and current approximate ash basin pond
elevation data. The elevation water in the ponds is likely to have varied over time so that
current conditions may not be representative of earlier conditions. Historic pond water
elevations should be reviewed and high water elevation should be used to identify
61

changes in hydraulic gradient that might identify other areas of potential interest. The
direction of flow and areas of potential interest should be re-evaluated using historic pond
water elevations once the new monitoring wells have been installed and a complete round
of water levels has been recorded.
Conclusion
DENR has already pointed out some of the significant shortcomings of the Groundwater
Assessment Work Plans, but additional serious problems remain. DENR must require Duke
Energy to submit revised Work Plans and Receptor Surveys that resolve all of these issues in
order to ensure that they provide valid and accurate information on the severity of Duke's
groundwater pollution.
Thank you for your consideration of these comments. .
cc: Donald van der Vaart
S. Jay Zimmerman
Sincerely,
F
Frank S. Holleman III
Senior Attorney
62