2016-05-13 Roxboro Hutson Report Final

GEO-HYDRO, INC
Consulting in Geology and Hydrogeology
1928 E. 14th Avenue
Denver, Colorado 80206
[phone]
EXPERT REPORT OF
MARK A. HUTSON, PG
Roxboro Steam Electric Plant
S emora, NC
Prepared for:
Southern Environmental Law Center
601 West Rosemary Street
Suite 220
Chapel Hill, NC 27516-2356
May 2016

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1. Summary of Opinions Formed
Based upon my review of the available information I have formed the following opinions on closure
of the coal ash basins at the Roxboro Steam Electric Plant (Roxboro).
1. Coal ash stored in the Roxboro ash basins is the source of contamination detected in
groundwater.
2. Capping coal ash located within the Roxboro ash basins will not protect groundwater quality
downgradient of the basins.
3. The groundwater flow and transport model does not reflect real-world conditions.
4. Monitored Natural Attenuation (MNA) is not an acceptable groundwater remediation
strategy at Roxboro.
5. Capping coal ash located within the Roxboro ash basins will not be protective of surface
water quality.
6. Removal of the coal ash will remove the source and reduce the concentration and extent of
groundwater contaminants.
7. The coal combustion residual impoundment risk classification proposed by the North
Carolina Department of Environmental Quality (NCDEQ) improperly minimizes protection
of environmental quality.
The background and rationale behind each of these opinions are described in this report.

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2. Introduction
Duke Energy (Duke) reportedly stores approximately 33,390,000 tons of coal ash in various areas
around the Roxboro facility, including ash stored in two unlined ash basins (East and West), lined
and unlined landfills, and other ash filled areas'. An additional poorly identified and
uncharacterized Unnamed Eastern Extension impoundment was recently reported to NCDEQ. The
location and volume of additional coal ash contained in the Unnamed Eastern Extension
impoundment was not identified in any of the documents reviewed. Pollution caused by the coal ash
at this site is currently the subject of an enforcement action brought by the NCDEQ. Organizations
represented by the Southern Environmental Law Center are also parties to this litigation.
North Carolina General Assembly Session Law 2014-122, the Coal Ash Management Act (LAMA)
of 2014, required the owner of coal combustion waste surface impoundments to conduct
groundwater monitoring, assessment and remedial activities at coal ash basins across the state, as
necessary. The owner of the coal ash surface impoundments was required to submit a Groundwater
Assessment Plan (GAP) to NCDEQ by December 31, 2014. Comprehensive Site Assessment (CSA)
reports that reported the results of site characterization activities were required to be submitted
within 180 days of approval of the GAP. Information developed under the CSA provided the data to
be used to prepare Corrective Action Plans (CAP) that were to be submitted to NCDEQ within 90
days of submittal of the CSA. An agreement between Duke Energy and NCDEQ resulted in
breaking the CAP into Parts I and 2. As of this date only the CAP Part I has been produced for the
Roxboro site.
Further, CAMA specifies that any impoundments classified by NCDEQ as high-risk be closed no
later than December 31, 2019 by dewatering the waste and either, a) excavating the ash and
converting the impoundment to an industrial landfill, or b) excavating and transporting the waste off-
site for disposal in an appropriately licensed landfill. Intermediate -risk impoundments are required
to be closed similarly to high-risk impoundments, but under a relaxed closure deadline of December
31, 2024. Impoundments classified as low-risk by NCDEQ must be closed by December 31, 2029
either similarly to the high and intermediate -risk sites, or by dewatering to the extent practicable and
capping the waste in place.
In January 2016 the NCDEQ issued Draft Proposed Risk Classifications (NCDEQ, 2016) for 10 ash
impoundment sites, including Roxboro. NCDEQ assigned separate proposed risk classifications for
the West, East, and Unnamed Eastern Extension ash ponds. The East Ash Basin (EAB) was rated
low to intermediate risk and the West Ash Basin (WAB) was rated low risk, thus allowing for
closure of these impoundments by capping waste in place. The Unnamed Eastern Extension (UEE)
' SynTerra, 2015a
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impoundment was rated intermediate risk pending further assessment. On behalf of the Southern
Environmental Law Center, I have reviewed the Groundwater Assessment Plan (SynTerra, 2014),
Comprehensive Site Assessment (SynTerra, 2015a), the Corrective Action Plan Part 1 (SynTerra,
2015b), the Corrective Action Plan Part 2 (SynTerra, 2016), the Draft Proposed Risk Classifications
(NCDEQ, 2016), and three National Pollutant Discharge Elimination System (NPDES) discharge
monitoring reports (DMR's) for Roxboro (Duke Energy, 2014). 1 have also reviewed raw
groundwater model input and output files provided by Duke to facilitate understanding of the model
that informs the CAP Parts 1 and 2.
This report details my opinions regarding: the source of groundwater and surface water pollution at
Roxboro, potential remedies for that pollution discussed in the Corrective Action Plan, and the
proposed risk classification for the Roxboro site.

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3. Qualifications
The opinions expressed in this document have been formulated based upon my formal education in
geology and over thirty-five years of experience on a wide range of environmental characterization
and remediation sites. My education includes B.S. and M.S. degrees in geology from Northern
Illinois University and the University of Illinois at Chicago, respectively. I am a registered
Professional Geologist (PG) in Kansas, Nebraska, Indiana, and Wisconsin, a Certified Professional
Geologist by the American Institute of Professional Geologists, and am currently serving as Past
President of the Colorado Ground Water Association.
My entire professional career has been focused on regulatory, site characterization, and remediation
issues related to waste handling and disposal practices and facilities. I have worked on contaminated
sites in over 35 states and the Caribbean. My site characterization and remediation experience
includes activities at sites located in a full range of geologic conditions, involving soil and
groundwater contamination in both unconsolidated and consolidated geologic media, and a wide
range of contaminants. I have served in various technical and managerial roles in conducting all
aspects of site characterization and remediation including definition of the nature and extent of
contamination, directing human health and ecological risk assessments, conducting feasibility
studies for selection of appropriate remedies to meet remediation goals, and implementing remedial
strategies. For the last ten years much of my consulting activity has been related to groundwater
contamination and permitting issues at coal ash storage and disposal sites.
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4. Site Background
Site Setting and History
The Roxboro plant is a coal-fired electricity -generating facility located near Semora, in Person County
North Carolina. Hyco Reservoir borders the Roxboro plant to the north and west. Coal ash generated
at the plant has been sluiced to the ash basins and hauled to landfill overlying the ash basins since
operations commenced in 1966. The EAB was constructed in 1966 by constructing an earthen dam
across two unnamed creeks located southeast of the power station (Figure 1). An unlined landfill was
constructed over the top of the sluiced ash in the EAB in the late 1980s and a lined landfill was
constructed over the unlined landfill in 20042.
The ground surface elevation below the EAB dam was reported to be between 390 and 400 feet mean
sea level (MSI) 3. Groundwater elevations in EAB monitoring wells are reported to be between 464 and
469 ft ms14. The difference between the reported ash basin groundwater elevations and the natural
ground surface elevations underlying the EAB indicates that from 64 to 79 feet of saturated coal ash is
present within the EAB.
The WAB was constructed in 1973 by installing a dam across Sargents Creek, located south of the
power station. Coal combustion waste was historically sluiced into the WAB. A Flue Gas
Desulfurization (FGD) System, including a lined gypsum settling pond was constructed over a portion
of the WAB. The WAB currently remains in operation, receiving sluiced bottom ash from the power
station and surface waters discharged from the EAB and overlying lined landfill.
The ground surface elevation along the buried Sargents Creek was reported to be between 390 and 410
feet msl prior to construction of the WAB 5 Groundwater elevations in WAB monitoring wells are
reported to be between 448 and 463 ft ms16. The difference between the reported ash basin
groundwater elevations and the natural ground surface elevations underlying the basin indicates that
from 38 to 73 feet of saturated coal ash is present within the WAB.
Hydrogeology
The CSA describes three natural hydrogeologic units or zones of groundwater flow at the Roxboro
Plant. Coal ash is considered as its own hydrogeologic unit that is localized to the ash basins. The
zone closest to the surface is the shallow or surficial flow zone encompassing saturated conditions,
where present, in the saprolite and alluvium beneath the Site. A transition zone is encountered below
the shallow zone and is characterized primarily by partially weathered rock of variable thickness. The
2 SynTerra, 2015b, p. 1-2.
3 SynTerra, 2015b, Appendix E, p.3.
4 SynTerra, 2015a, Figure 6-5.
5 SynTerra, 2015b, Appendix E, p.4.
6 SynTerra, 2015a, Figure 6-5.
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bedrock flow zone occurs below the transition zone and is characterized by the storage and
transmission of groundwater in water -bearing fractures. Due to its limited occurrence and extent, the
shallow zone is considered part of the transition zone. Where present, groundwater exists under
unconfined conditions in each of the hydrogeologic units. The surficial/transition zone and bedrock
aquifers are interconnected.
On a regional scale groundwater appears to flow from highland areas in the south and east, to the
northwest toward Hyco Lake. On a local scale groundwater flow directions are poorly defined. Large
areas of the Bedrock Water Level Map included with both the CSA and CAP Part 1 (Figure 2) show
neither groundwater elevation data nor contours. Due to the scarcity of head data the description of
the groundwater flow system included in the Groundwater Modeling Report8 describes groundwater
flow in terms of inferred flows. The groundwater flow system beneath the eastern lobe of the EAB is
inferred to receive recharge from uplands to the south and east9, and discharge from the eastern lobe
by flowing toward the water intake canal, or northeast to a stream that drains the lake (now identified
as the unnamed eastern extension) that flows along the eastern side of the EAB and discharges into the
water intake canal10. Groundwater flow into the western lobe of the EAB is inferred to occur from the
west, south and east' 1. Groundwater discharges from the western lobe of the EAB are inferred to
occur to the north toward the plant. Further, the modeling report infers that groundwater beneath the
EAB flows toward discharge areas in wetlands and/or ponds located north of the EAB dam.
Groundwater flow into the WAB is inferred to flow into the basin from upland areas to the east.
Groundwater appears to discharge from the WAB to the north, west and south. Groundwater is
inferred to discharge from the WAB by flow to the north through and around the dam, through and
beneath the dam on the south end of the WAB, and to discharge into the canal located west of the
WAB.
Surface waters from the EAB, including groundwater that has discharged to surface water, are routed
to the west where it enters the northern end of the WAB. Sluice water used to transport bottom ash to
the WAB also discharges into the northern end of the WAB. Surface water from these sources, along
with precipitation and groundwater that discharges from the WAB, discharges through the filter dam at
the south end of the WAB and into the discharge canal. The discharge canal wraps around the west
side of the WAB, ultimately discharging into Hyco Lake. The CAP indicates 12 that seeps and surface
7 SynTerra, 2015a, p.26.
8 SynTerra, 2015b, Appendix E
9 The discussion of groundwater flow included in Appendix E (p. 4) erroneously indicates that flow toward the EAB is from
uplands to the north and west. Examination of head distribution maps included with the modeling report make it clear that
this statement in the text is in error.
10 SynTerra, 2015b, Appendix E, Section 2.2.
11 The Groundwater Modeling Report actually says recharge is from the north rather than the south. It appears that this was
a mistake as the limited groundwater head data shows higher heads located south of the west lobe.
12 SynTerra, 2015b, Section 2.2.3.
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water drain into NPDES-permitted surface water bodies, but fails to recognize that the parameters
required for testing under the NPDES permit are not those that are elevated by coal ash impacts.
Nature and Extent of Contamination
Data collected during the CSA show that groundwater is impacted by the ash basins with boron,
strontium, sulfate, total dissolved solids (TDS) and to a lesser extent, cobalt, iron, manganese, and
vanadium. 13 The CSA also determined that Hyco Lake and the plant's cooling water intake and
discharge canals are the primary receptors of impacted groundwater and seeps, and that groundwater
flow direction data and surface water data indicate that constituents of interest are migrating to the
14
reservoir
Some of the most problematic issues at the Roxboro plant are related to the interaction of groundwater
and surface water bodies on and around the plant site. The CAP Part 2 confirms this observation is
several locations 15. Rapid discharge of contaminated groundwater into surface drainages limits the
extent of groundwater contaminant plumes to the area beneath the basins, and between the basins and
surface discharge areas. Ash -impacted groundwater plumes are not restricted to the immediate area of
the basins by a lack of migration, their size is restricted because the contaminated groundwater
discharges to surface water.
Particularly problematic is the fact that the discharge channel that carries most of the discharge from
this site has still not been characterized. No surface water samples were collected from the outflow
channel even though all of the combined drainage from the East and West Ash Basins are routed to
Hyco Reservoir through this channel. Contaminated water is collected in the East Ash Basin and
pumped to the West Ash Bain where it is again passed through ash and presumably leaches additional
contaminants. The west discharge channel carries surface water discharge also receives groundwater
discharges from beneath the West Ash Basin. It should be expected that contaminant loading will
increase in the down stream direction. The fact that the west discharge canal outfall was not sampled
during the CSA, nor sampled as a data gap, would appear to indicated that Duke is not interested in
identifying the potential magnitude of impacts to Hyco Reservoir.
Characterization of water quality in Hyco Reservoir is inadequate. The surface water sample location
nearest to the discharge channel outfall point is NPDES outfall 003 (Figure 1-2) located between the
West Cooling and Hyco reservoirs. Review of discharge monitoring reports for outfall 003 shows that
selenium is the only coal ash related parameter that is included on the analyte list for sampling at this
location. All of the other key parameters expected to be found in discharges from the site are not being
monitored Outfall 003. Surface water sample locations SW -01, SW -2 and SW -3 are located at
tributaries along Hyco Reservoir that are located further from the outfall and separated from the
13 SynTerra, 2015b, p. 3-8
14 SynTerra, 2015a, p.114
15 An example is located in SynTerra, 2016, page 2-2, 4`h bullet
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reservoir by a long peninsula. None of the surface water sample locations adequately characterize
impacts to Hyco Reservoir.
Even without adequate characterization of water quality, the human Health Risk Assessment
concluded " that exposure to fish tissue caught from Hyco Reservoir and consumed under the
hypothetical recreational and subsistence fishing scenarios resulted in potentially unacceptable
noncarcinogenic health risk. This conclusion was based on fish tissue concentrations modeled from
surface water results in the absence of Hyco Reservoir surface water samples. The discussion
presented in the CAP part 2 cites uncertainty and overestimation associated with the fish tissue
modeling to assert that consumption of fish is not expected to pose risk to human health. However, as
was described above, the surface water samples that the modeling was based on does not include
characterization of the discharge from the west discharge channel, nor water directly from potentially
impacted areas of Hyco Reservoir. Additional characterization of surface water and sediment on the
site and in Hyco Reservoir is a severe data gap since potential hazards to human health from
consumption of fish from Hyco Reservoir were identified.
Determination of Background Water Quality
Accurate and appropriate determination of background water quality is of critical importance to
evaluation of groundwater impacts from the ash basins. Provisional background concentrations for
groundwater, as well as other media, were proposed in the CAP Part 1. The CAP Part 2 reported
analytical results from rounds 1 thru 4 of background groundwater sampling, but further evaluation of
results and background concentrations was deferred to future reports. Groundwater monitoring results
are currently being compared to provisional background concentrations that are based on an
incomplete data set.
Further, the values identified as the provisional background are either calculated values or are the
highest value recorded at any of the various locations, both of which are dependent on the distribution
of concentrations obtained during sampling. Water quality monitoring results are easily influenced by
sampling methods and techniques and can easily provide spurious data. Even the background data set
that is being developed by sampling new background wells around the Roxboro site are capable of
producing outliers in the data set that if not removed could skew the background concentration. The
complete data set needs to be evaluated for sampling or analytical problems and tested to eliminate
outliers that could skew the data prior calculating or selecting background concentrations.
Decisions about remedial strategies to be utilized to clean-up or at least temporarily contain ash -related
contaminants must not be based on incomplete or skewed background data. This is absolutely what is
happening with decisions currently being made on the Roxboro site.
16 SynTerra, 2016, Appendix D, Section 5.5, p. 5-16, 3rd paragraph
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Groundwater Mode
The groundwater flow and transport model of the site was constructed and used in the CAP Part 1 to
evaluate groundwater flow and investigate three remedial scenarios. The scenarios investigated
included the No Action scenario, a Cap -In -Place scenario, and an Ash Excavation scenario. The
model was used to predict contaminant distributions for the next 5, 15 and 30 years, under each
scenario. Groundwater modeling reported in the CAP Part 2 17 increased the time duration of model
runs to 100 years, but reported results only for the No Action and Cap -In -Place scenarios. The
Excavation scenario was omitted without explanation.
The No Action scenario'8 relies on natural attenuation processes to reduce contaminant concentrations
over time. The ash basin remains in place without modification and "the assumption is made that
current recharge and contaminant loading rates from the ash to the underlying formations are held
constant". "The flow system is assumed to be at steady state with respect to the conditions in 2015."
"Concentrations in the ash were held constant at the measured concentrations." Using these
assumptions the model predicts that the boron plumes will continue to expand laterally and downward,
and increase in concentration over time. The predicted increases in plume size are predicted to be from
on the order of few hundred feet to very small. This result is likely due to constraints on plume size
related to known hydrologic boundaries as were described above. Once a plume reaches a hydrologic
boundary the constituents migrating with groundwater are transferred to the surface water system and
the groundwater plume does not continue to grow in size though contaminants continue to migrate
with surface water.
The Cap -In -Place scenario involves placing an unspecified low permeability cover over the ash basin
to prevent infiltration. The cover system is described in CAP Part 1 as a hybrid cap -in-place approach
or a low permeability surface cover19. In CAP Part 2 the cap is described as a "low permeable
composite cover (liner)"20, not necessarily a synthetic cap. The groundwater model assumes that
infiltration from above is set at zero, something that is not realistically achievable even with a well
constructed synthetic cap. Evaluation of realistic infiltration through the specific materials that are to
be used to construct the cap must be performed in order to accurately predict the volume of infiltration
and the volume of leachate that can be expected to migrate out of the basin. While MODFLOW does
not offer cap performance evaluations, other programs such as HELP could be used to generate
reasonable infiltration values for use in MODFLOW.
17 SynTerra, 2016, Appendix B
18 The entire description of this scenario is presented in the CAP, Appendix E, Section 6.1.
19 SynTerra, 2015b, p. ES -9 and 2-15
20 SynTerra, 2016, p. ES -2
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The CAP Part 2 makes a brief reference to a system of drains or other engineering controls will be
constructed to control inflow of groundwater and lower the groundwater table below the ash21. Use of
drains to lower the water table beneath the ash basins is not discussed anywhere other than in the
Executive Summary. No engineering controls other than installation of an assumed 100% effective
cap were included in modeling reported under this program. The impacts of engineering controls on
groundwater flow and contaminant transport cannot be known on the basis of information provided in
this document.
Results of simulation of the cap -in-place scenario predict that zones of boron concentration increase in
size and concentration relative to 2015 conditions, but the magnitude of the increases are less that
those calculated under the No Action scenario. Concerns with the Capping Ash Basin scenario include
the assumption of no recharge within the basin and changing the way that contaminant concentrations
in the source material are handled. The hydrogeology of the Roxboro impoundments (see description
of groundwater flow above) includes recharge into the basins from higher elevation areas to the south
and east. Capping of the ash in the basin will not control influx of groundwater from upland areas.
Discharges of groundwater into the ash basins are likely significant as groundwater discharges into the
basin were sufficient to maintain streams prior to their being buried under coal waste.
The Excavation scenario represents complete removal of the ash by inactivating the upper four model
layers, adding drain cells to simulate drainages, and setting recharge within the ash basin to ambient
levels. This scenario predicts the largest reduction in ash -related contaminant concentrations of any of
the tested scenarios. Despite providing the most improvement in groundwater quality the Excavation
Scenario was not selected by Duke as the recommended source control alternative and was not
included in the modeling reported in the CAP Part 2.
21 SynTerra, 2016, p. ES -2
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5. Opinion 1: Coal Ash Stored in the Roxboro Ash Basins is the
Source of Contamination Detected in Groundwater
Coal ash is the source of contaminants detected in groundwater at concentrations above applicable
standards in the vicinity and downgradient of the ash basin. Data collected during the CSA show
that groundwater is impacted by the ash basins with boron, strontium, sulfate, TDS and to a lesser
extent, cobalt, iron, manganese, and vanadium. 22 The lateral extent of groundwater impacts outside
of the ash basins is limited by the presence of water local discharge areas. The contaminated pore
water migrates out of the ash basins and either directly into surface water, or into groundwater that
subsequently discharges to surface water, and eventually into Hyco Lake. This interpretation is
consistent with the CSA which states that:
Hydrologic boundaries are present downgradient of the ash basins in the form of the
intake canal, the discharge canal and the cooling reservoir which discharges to Hyco
Lake. When the CCR constituents reach these hydrologic boundaries, they are
removed from the groundwater system, and they enter the surface water system. At
the Site, boron is the primary constituent that is migrating from the ash basins. 23
22 SynTerra, 2015b, p. 3-8
13 SynTerra 2015b, p.3-8
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6. Opinion 2: Capping Coal Ash Located Within the Roxboro Ash
Basin Will Not Protect Groundwater Quality Downgradient of the
Basins
The CAMA process proposed designation of the Roxboro site as low-risk creates the possibility that
Duke could pursue closure of the Roxboro impoundment by capping the disposed ash in place.
Capping the waste within the footprint of the ash basin will not be protective of groundwater quality
downgradient of the basin.
Environmental contaminants contained in coal ash are leached into groundwater when precipitation
infiltrates through the waste or, when groundwater flows through waste that has been placed below
the water table. In the case of the Roxboro ash basins, both of these processes are currently acting to
create the contaminated ash porewater, groundwater, and surface water that discharge into local
surface waters and eventually into Hyco Lake. The cap -in-place remedy would likely reduce the
amount of water that enters the waste from precipitation. This remedy would however do nothing to
reduce the amount of groundwater that flows laterally into the basin from surrounding geologic
units, through the capped waste, into downgradient groundwater, and eventually into Hyco Lake.
The lined landfill that was constructed over a portion of the EAB should function as a cap over the
ash disposed in the unlined landfill and ash basin. The CSA 24 indicates that construction of a lined
landfill has resulted in decreasing concentrations of iron, manganese and chromium in three
monitoring wells (GMW-06, GMW-10 and GMW-11). The available data set does not show a clear
pattern of decreasing contaminant concentrations related to construction of the lined landfill.
Review of the comprehensive analytical results from Roxboro 25 shows that large decreases in
several parameters were observed in some monitoring wells during the first few sampling events and
prior to construction of the lined landfill. Figures 3 and 4 show graphs of boron, sulfate, selenium
and TDS concentrations measured in samples from wells in the immediate vicinity of the lined
landfill. Sulfate, TDS, and selenium26 concentrations in some wells were very high initially and
show rapid declines in concentration between the initial sampling event in 2002 and 2004 when the
lined landfill was constructed. This is an indication that decreased contaminant concentrations in
wells since their early sampling events appear to have been due to improper well development or
sampling techniques rather than improving water quality resulting from landfill construction.
Boron, sulfate, and TDS concentrations have been increasing rapidly in monitoring well GMW-8
since 2013. Analytical data graphs show that concentrations of ash -related parameters in wells
24 SynTerra, 2015b, p.1-8
25 SynTerra, 2015a, Attachment 3
26 Note that boron was not included in the tested parameters until 2002, so the early concentrations of boron are
unknown.
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GMW-06, GMW-08 and GMW-11 have remained at or above water quality standards despite the
presence of the lined landfill. Continued detections of elevated concentrations 27 of ash -related
contaminants at in groundwater around the lined landfill indicates that ash underlying the lined
landfill continues to release contaminants to groundwater, even though most infiltration from above
has presumably been eliminated by the landfill liner. This result is to be expected at any location
where ash remains submerged below the local water table. Continued generation and downgradient
migration of leachate will occur in the Roxboro Ash basins unless all of the ash in the basin is
dewatered and remains above the high water table, a scenario that is unlikely to occur at Roxboro.
Groundwater modeling reports prepared in support of the CAPS provided no estimation of the
amount of saturated ash that would remain at Roxboro should the capping in place remediation
scenario be implemented. An estimate of the thickness of the remaining thickness of saturated ash
can be obtained by comparing the elevation of the natural ground surface beneath the basins to the
groundwater elevation in wells just outside of the basins28. The ground surface elevation below the
EAB dam was reported to be between 390 and 400 feet ms129. Groundwater elevations in EAB
monitoring wells located just outside of the basin are reported to be between 462 and 513 ft n1s130.
The difference between the lowest measured groundwater elevation in wells located just outside the
ash basin and the highest natural ground surface elevations underlying the EAB indicates that at least
62 feet of saturated coal should be expected to be present beneath the EAB were the cap in place
remediation scenario implemented.
The natural ground surface elevation beneath the WAB was reported to be between 390 and 410 feet
ms131. Groundwater elevations in WAB monitoring wells located just outside the ash basin are
reported to be between 452 and 456 ft ms132. The difference between the lowest measured
groundwater elevation in wells located just outside the ash basin and the highest natural ground
surface elevations underlying the WAB indicates that at least 42 feet of saturated coal should be
expected to be present beneath the WAB were the cap in place remediation scenario implemented.
The CAP Part 2 makes a brief reference to a system of drains or other engineering controls will be
constructed to control inflow of groundwater and lower the groundwater table below the ash33. Use
of drains to lower the water table beneath the ash basins is not discussed anywhere other than in the
Executive Summary. No engineering controls other than installation of an assumed 100% effective
27 above 2L standards
28 Estimates of the thickness of saturated ash that would likely remain were the capping ash in place scenario
implemented are provided since the groundwater modeling report did not provide an estimation. Further modeling, or
better model reporting, should be conducted to refine these estimates.
29 SynTerra, 2015b, Appendix E, p.3.
30 SynTerra, 2015a, Figure 6-5.
31 SynTerra, 2015b, Appendix E, p.4.
32 SynTerra, 2015a, Figure 6-5.
33 SynTerra, 2016, p. ES -2
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cap were included in modeling reported under this program. The impacts of engineering controls on
groundwater flow and contaminant transport cannot be known on the basis of information provided
in this document.
The modeling report indicates that excavation of the ash reduces the concentration of boron in
groundwater more than either the No Action or Cap -In -Place scenarios. This indicates that removal
of the Roxboro coal ash is the most effective option for improving groundwater quality and
minimizing future discharges to Hyco Lake. This is as would be expected considering that the cap in
place scenario would leave a significant thickness of saturated ash in place that would continue to
leach ash constituents into the groundwater far into the future. Even though there are serious flaws
in the groundwater modeling that artificially restrict groundwater impacts under the cap -in-place
scenario (see Opinion 3), the modeling effort confirms that ash excavation is the option that is most
protective of the environment and is a permanent solution.
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7. Opinion 3: The Groundwater Flow and Transport Model Does
Not Reflect Real -World Conditions
Groundwater models can be useful tools that can be employed to evaluate alternative actions at
waste disposal site such as Roxboro. This usefulness, however, is predicated on the model being
constructed in a manner that faithfully recreates actual field conditions. In this case, the models
include fundamental inconsistencies between observed and modeled conditions that cast doubt on
results and make it likely that the nature and extent of groundwater contamination under the cap -in
place scenario is understated. Each of the identified issues with the current model are identified
separately below.
Groundwater Flow Modeling
Model Geometry Artificially Isolates the Ash
The layering of ash used in the model flow model effectively works to restrict calculated flow of
water into/out of the ash layers. The MODFLOW code used to model the impoundment calculates
head and groundwater flux between each side, top, and bottom of adjacent cells. The ash in layers 1-
4 has no lateral continuity with any of the adjacent natural materials in the sides of the basin. The
layers extend laterally to the edge of the basin and terminate at a no flow boundary. Lateral flow of
groundwater from/to the sides of the basin into the ash is not considered in this model. When a
100% effective cap is assumed, the only flow in the ash of layers 1-4 is vertically into or out of the
underlying saprolite through the bottom of layer 4 (and top of layer 5). This prohibition of lateral
flow at the edges of the ash pond into/from the enclosing saprolite is compounded by the
corresponding imposition of the horizontal -to -vertical anisotropy for hydraulic conductivity. As
modeled, the vertical flow between the ash and saprolite is constrained by hydraulic conductivity
that is only 20% of that which would exist were the connection between the materials to occur
horizontally under the same gradients. The conditions included in this model create the equivalent
of a 100% effective liner on the top and sides and an 80% effective liner at the bottom of the ash.
This is, of course, not reflective of real—world conditions.
Assumption of Cap Effectiveness
The Cap—In-Place scenario assumes construction of a 100% effective cap over the ash in Layer 1.
While zero infiltration through the cap and into the ash is an easy assumption to make, in the real
world some infiltration through even the most robust cap systems is expected. When an assumed
100% effective cap over the top of the ash is combined with lateral isolation of the ash by no -flow
boundaries (described above), the only flow in the ash of layers 1-4 is vertically into or out of the
underlying saprolite through the bottom of layer 4. This is an assumed condition that has no basis in
the real world. The combined effect of artificially restricting inflow of groundwater from the sides
15

GEO-HYDRO, INC
of the basin into the ash and assuming a 100% effective cap is to provide overly optimistic
evaluations of the effectiveness of the cap -in-place remedial scenario. Specific cap materials must
be identified and a realistic estimate of infiltration must be incorporated into the model, including
how they change as the cap materials deteriorate over time, if the Cap -In -Place scenario is to be
seriously evaluated.
Fate and Transport Modeling
Constant Concentration Cells Within the Ash
The Roxboro baseline and the no action transport simulations have a huge number of fixed
concentration (source) cells that define the concentrations levels within the four ash layers. There
are 42,232 constant concentration cells in the ash (10,558 in each of Layers 1 — 4). Each cell defines
the concentration of 4 components. Due to the restrictions of the flow model, all flow to/from the
ash ponds occurs through the cells of Layer 4. The use of constant concentrations in the ash in Layer
4 cells means that concentration of each constituent in water leaving the ash basin is completely
determined by the fixed concentration assigned for each Layer 4 cell that discharges leachate,
regardless of the distribution of constituent concentrations within rest of the ash.
The cap -in-place scenario is dramatically different. The number of constant concentration cells is
greatly reduced, but not they are not eliminated. Instead of 42,232 such cells, this scenario has only
930 constant concentrations cells. All of 930 constant concentration cells are in Layer 4. The
remaining 41302 ash cells in Layers 1 thru 4 are variable concentration cells. In MT3DMS variable
concentration cells add no contaminants to the groundwater. Coincident with installation of the cap,
the modeler assumes that any ash that remains saturated is somehow incapable of producing
contamination for any constituent except for the remaining 930 constant concentration cells. The
shift in the MT3DMS source from leachate producer to inert media has no justification.
The remaining 930 cells generate contamination in perpetuity. However, the concentrations of
contaminants generated upon installation of the cap bears no apparent relationship to the
concentrations generated immediately prior to the installation of the cap. In the case of boron, each
of the 930 cells is a constant concentration of 3000 ppm. There is no explanation in the report as to
why these cells and these alone will continue to generate contamination, why that contamination for
boron would be at 3000 ppm in each cell regardless of previously simulated concentrations. It is
also noted that any leachate with higher boron concentrations migrating through these cells would
have its concentration reduced to 3000 ppm before further migration.
The impact of these 930 cells on the remaining 3 constituents is even more dramatic. The constant
concentrations for each of these constituents in each of the 930 cells is zero. This means that upon
installation of the cap, this scenario sets any previous concentrations in these cells to zero. It also
16

GEO-HYDRO, INC
means that any water migrating through these cells from the overlying ash is also reset to zero.
There is no real-world scenario for this to be a result of installing a cap to prevent infiltration.
Constant Concentration Cells Beneath the Ash Landfill
In addition to the 42,232 constant concentration cells within the ash for the baseline and no -act
scenarios. There are 275 constant concentration cells, each with 4 components, in Layer 7; 320
constant concentration cells, each with 4 components, in Layer 8, and 26 constant concentration
cells, each with 4 components in Layer 9. These cells are assigned constant contaminant values that
represent the postulated concentrations in leachate that migrates downward from waste disposal
facilities to the water table. The concentrations that are assigned to the water table beneath the
gypsum pile and the unlined landfill are not developed from concentrations of leachate within the
facilities. The methodology used to develop the water table assigned concentration beneath the
landfill is problematic.
There are no data from within the landfill regarding leachate composition. In lieu of using facility -
specific water quality data, the modelers postulated that leachate within the landfill would be similar
to pore water within the ash ponds. The water quality within the ash ponds varies significantly from
place to place. The aggregate data from the ash pond analyses were used to develop a single value
for assignment to the water table. There are a variety of methods that could be used estimate a single
value of a contaminant from a variable data set. The method chosen by the Roxboro modelers is not
among the valid ones.
The geometric mean of the boron data from the ash pond was assumed representative of the landfill
leachate at the water table. A geometric mean is a specialized averaging technique that is used to
find a central value of numbers that are log -normally distributed. There is no expectation that
concentrations of a contaminants found in pore water in heterogeneous deposits of ash in the ponds
are log -normally distributed. The effect of using the geometric mean of concentration data is that
the geometric mean is weighted toward the small values of the sample being averaged. For example,
a leachate sample of 1 and a leachate sample of 10,000 (both within the range of values observed for
boron) have an arithmetic mean (standard averaging technique) of 5000.5. The geometric mean is
100. If the ash leachate is the landfill can be assumed to be similar or analogous to the pore water of
the ponded ash, an appropriate composite value for modeling purposes will be higher than the
geometric mean of the data from the ponded ash. The same geometric mean of the observed ash
value is used elsewhere in the model; where no data exist, the geometric mean is assumed. The
effect of using this value is almost certainly an underestimation of the source concentrations in the
model.
Subsequent to the installation of the cap, the modeler eliminates the constant concentrations cells at
the water table beneath the waste disposal facilities. This represents the cessation of leachate
17

GEO-HYDRO, INC
migration from the facilities to the underlying groundwater. No explanation is offered to justify that
there would be the cessation of leakage from these facilities as a result of installation of the cap over
the ash.

GEO-HYDRO, INC
8. Opinion 4: Monitored Natural Attenuation Is Not An Acceptable
Groundwater Remediation Strategy at Roxboro
The CAP Part 134 indicates that Duke may evaluate monitored natural attenuation (MNA) as a
potential groundwater remedy for certain area of the Roxboro site. This document attempts to make
it appear that MNA is a viable remedial option for impacted groundwater downgradient of the
Roxboro ash basin. From a technical standpoint, MNA remedies typically require:
• That there are no current receptors, including surface water or wetland discharges and water
supply wells.
• That there is sufficient lateral space between the contaminant source and groundwater
discharge areas to allow natural attenuation to reduce contaminant concentrations prior to
reaching a receptor.
• Evidence that the location of the leading edge of the contaminant plumes be stable (not be
expanding).
• That there is a natural reduction in contaminant concentrations along flow paths.
• That there is sufficient space between the contaminant source and groundwater discharge
areas to allow a monitoring system to be established, including sentry wells located ahead of
the leading edge of the contaminant plume.
None of these technical factors for considering NINA as an appropriate remedial strategy at the
Roxboro site are met. From a scientific standpoint there is no justification for considering MNA.
The CAP Part 2 continues to try to make it appear that MNA is a viable remedial option for this ash
basin. An evaluation of NINA provided in the CAP Part 235 does not support its use at Roxboro.
For instance, the document states:
"However, at Roxboro, that portion of groundwater flow within bedrock (where bedrock is
unweathered and has no soil like properties) is not likely to sorb large amounts of the key
constituents." (p.6-9, top paragraph), and
"Roxboro is primarily underlain by bedrock and for this reason there is insufficient data to
observe significant trends." (p.6-11, last sentence)
Since sorption of key constituents is not likely to be effective in bedrock and Roxboro is primarily
underlain by bedrock, it is hard to imagine a rationale for concluding that MNA is an appropriate
remedial option other than a cost driven evaluation.
34 SynTerra, 2015b, p.5-1
35 SynTerra, 2016, Section 6.4.1
19

GEO-HYDRO, INC
The CAP attempt to make it appear that NINA is a viable remedial option for impacted downgradient
of the Roxboro ash basin. However, MNA is not a viable closure option for this site for several
reasons including the following:
• Duke Energy has not proposed removal of the waste for disposal in a secure location.
Hydrogeologic conditions presented in this document shows that some of the ash would
remain saturated after capping. Saturated ash will continue to leach metals into groundwater
that will flow toward and eventually discharge into Hyco Lake. As a practical matter, in the
absence of removal all sources of contamination cannot be controlled
Many of the ash -related constituents in groundwater at this site neither degrade nor attenuate.
The Geochemical Site Conceptual Mode136 states that boron is an indicator of coal ash
impacts to groundwater because it "is essentially inert, has limited potential for sorption and
lacks an affinity to form complexes with other ions." The characteristics of the contaminant
plumes alone are sufficient to render the Roxboro site ineligible to use MNA as a
remediation strategy.
36 SynTerra, 2015b, Section 3.3
20

GEO-HYDRO, INC
8. Opinion 5: Capping Coal Ash Located Within the Roxboro Ash
Basin Will Not Be Protective of Surface Water Quality
The most problematic issues at the Roxboro plant are related to the interaction of groundwater and
surface water bodies on and around the plant site. The CAP indicates in several locations that the
lateral extent of groundwater contamination is generally limited to areas beneath or immediately
downgradient of the ash basins. However, at the Roxboro site the ash basins are bounded by
drainage features on around the perimeter of the basins that act as groundwater discharge areas.
Ash -impacted groundwater plumes are not restricted to the immediate area of the basins by a lack of
migration; their size is restricted only because the contaminated groundwater discharges to surface
water features. This is particularly problematic since water quality in the outflow channel that
carries most of the discharge from this site has not been characterized. No surface water samples
were collected from the outflow channel even though the combined drainage from the East and West
Ash Basins are passed through this channel to Hyco Reservoir.
Surface water monitoring conducted under NPDES Permit NC0003425 does not include the most
common analytical parameters that are found in ash impacted waters. This means that a major
discharge of likely ash -impacted water from the Roxboro site into Hyco Lake was not sampled as
part of the CSA and is not being appropriately monitored under NPDES requirements. The
chemistry and volume of water that flows through canals and into Hyco Lake under current and
expected closure conditions must be evaluated to assure that the selected remedy is protective of
water quality in Hyco Reservoir.
Water quality in Hyco Reservoir has also never been adequately characterized. The surface water
sample location nearest to the discharge channel outfall point is NPDES outfall 003 located between
the West Cooling and Hyco reservoirs. Review of discharge monitoring reports for outfall 003
shows that selenium is the only coal ash related parameter that is included on the analyte list for
sampling at this location. All of the other key parameters expected to be found in discharges from
the site are not being monitored Outfall 003. Surface water sample locations SW -01, SW -2 and SW -
3 are located at tributaries along Hyco Reservoir that are located further from the outfall and
separated from the reservoir by a long peninsula. None of the surface water sample locations
adequately characterize impacts to Hyco Reservoir.
Even without adequate characterization of water quality, the Human Health Risk Assessment
concluded 37 that exposure to fish tissue caught from Hyco Reservoir and consumed under the
hypothetical recreational and subsistence fishing scenarios resulted in potentially unacceptable
noncarcinogenic health risk. This conclusion was based on fish tissue concentrations modeled from
surface water results in the absence of actual Hyco Reservoir surface water samples. The discussion
37 SynTerra, 2016, Appendix D, Section 5.5, p. 5-16, 3rd paragraph
21

GEO-HYDRO, INC
presented in the CAP part 2 cites uncertainty and overestimation associated with the fish tissue
modeling to assert that consumption of fish is not expected to pose risk to human health. However,
as was described above, the surface water samples that the modeling was based on do not include
characterization of the discharge from the west discharge channel, nor water directly from
potentially impacted areas of Hyco Reservoir. Additional characterization of surface water and
sediment on the site and in Hyco Reservoir is a severe data gap since a potential hazard to human
health from consumption of fish from Hyco Reservoir was identified.
A cap -in-place remedy would not be protective of surface water quality. While a cap would likely
reduce the amount of water that enters the waste from precipitation, this remedy would do nothing to
reduce the amount of groundwater that flows laterally into the basin from surrounding geologic
units, through the capped waste, into downgradient surface water drainages, and eventually into
Hyco Lake. Groundwater would continue to flow into the ash basins from adjacent upland areas.
Groundwater that flows through the ash will continue to leach metals from the ash and transport
those metals down -gradient before discharging into adjacent surface water features. Even though
there are serious flaws in the groundwater modeling that artificially restrict groundwater impacts
under the cap -in-place scenario (see Opinion 3), the modeling effort confirms that ash excavation is
the option that is most protective of the environment and is a permanent solution.
22

GEO-HYDRO, INC
9. Opinion 6: Removal of the Coal Ash Will Remove the Source and
Reduce the Concentration and Extent of Groundwater
Contaminants
Removal (excavation) of the coal ash from the Roxboro ash basin is the only remediation scenario
that will separate the coal ash source materials from groundwater and eliminate flow of
contaminated groundwater and surface water into Hyco Lake. Excavation of the ash will remove the
source of groundwater and surface water contaminants, and reduce the concentration and extent of
current contaminants. The groundwater flow and transport model of the site was used in the CAP to
evaluate groundwater flow and investigate three remedial scenarios. The scenarios investigated
included the Existing Conditions scenario, a Capping Ash in Place scenario, and a Removal of Ash
scenario. The model was used to predict contaminant distributions for the next 5, 15 and 30 years,
under each scenario. The model showed that the Removal of Ash scenario resulted in the largest
reduction in ash -related contaminant concentrations of any of the modeled scenarios. Even though
there are serious flaws in the groundwater modeling that artificially restrict groundwater impacts
under the cap -in-place scenario (see Opinion 3), the modeling effort confirms that ash excavation is
the option that is most protective of the environment and is a permanent solution.
23

GEO-HYDRO, INC
10. Opinion 7: The Coal Combustion Residual Impoundment Risk
Classification Proposed by NCDEQ Improperly Minimizes
Protection of Environmental Quality
A risk ranking process was specified in CAMA to determine the type of closure permitted at each
facility. The law specifically requires NCDEQ to classify each impoundment as either high-risk,
intermediate -risk, or low-risk, based on consideration, at a minimum, of all of the following criteria.
(1) Any hazards to public health, safety, or welfare resulting from the impoundment.
(2) The structural condition and hazard potential of the impoundment.
(3) The proximity of surface waters to the impoundment and whether any surface waters are
contaminated or threatened by contamination as a result of the impoundment.
(4) Information concerning the horizontal and vertical extent of soil and groundwater
contamination for all contaminants confirmed to be present in groundwater in exceedance of
groundwater quality standards and all significant factors affecting contaminant transport.
(5) The location and nature of all receptors and significant exposure pathways.
(6) The geological and hydrogeological features influencing the movement and chemical and
physical character of the contaminants.
(7) The amount and characteristics of coal combustion residuals in the impoundment.
(8) Whether the impoundment is located within an area subject to a 100 -year flood.
(9) Any other factor the Department deems relevant to establishment of risk.
In order to evaluate each impoundment on the nine criteria the NCDEW established a risk
classification group38. The Risk Classification Group was broken into three sub -groups of people
based on areas of expertise (Groundwater, Surface Water, and Dam Safety) to develop a set of risk
factors to address each of the nine required criteria. Each subgroup reportedly placed a primary
emphasis on risk as it relates to the public from a groundwater, surface water, and dam safety
perspective and established one key factor that "plays a significant role in assigning an overall
classification" for that group. Other factors not identified as Key Factors were supposedly used to
"refine the risk classification and address the actual or potential risk to the environment and natural
resources."
The result of the risk classification methodology utilized by NCDEQ is that environmental and
ecologic risks posed by the Roxboro site were not fully considered by NCDEQ when establishing
the overall site risk and clean-up priorities. This resulted in the West, East, and Unnamed Eastern
Extension ash ponds being assigned Low, Low to Intermediate, and Intermediate risk ratings,
" NDEQ, 2016, p. 13, Classification Methodology
24

GEO-HYDRO, INC
respectively, ratings that essentially ignore the known environmental impacts of the Roxboro ash
ponds. For example, Table 1 provides a listing of the groundwater risk classification factors and
associated ratings for each ash pond at Roxboro. Ten groundwater risk factors were established and
received ratings by NDEQ for each ash pond.
Table 1
Groundwater Risk Classifications
Unnamed Eastern
Groundwater Factors
East Ash Pond
West Ash Pond
Extension
Number of downgradient receptors within 1500 feet of
compliance boundary that are potentially or currently
Low Risk
Low Risk
Low Risk
known to be exposed to impacted water. (Key Factor)
Amount of stored CCR reported in an impoundment
High Risk
High Risk
High Risk
Depth of CCR with respect to the water table
High Risk
High Risk
High Risk
Exceedance of 2L or IMAC standards at or beyond the
High Risk
High Risk
High Risk
established CCR compliance boundary
Population served by water supply wells within 1,500 feet
Low /Intermediate
Low /Intermediate
Low /Intermediate
upgradient or side gradient of the compliance boundary
Risk
Risk
Risk
Population served by water supply wells within 1,500 feet
Low Risk
Low Risk
Low Risk
downgradient of the compliance boundary
Proximity of 2L or IMAC exceedances beyond the
High Risk
Intermediate Risk
High Risk
compliance boundary with respect to water supply wells
Groundwater emanating from the impoundment exceeds
High Risk
High Risk
High Risk
2L or IMAC and that discharges to a surface water body
Ingestion of contaminated soil or fugitive emissions
Low Risk
Low Risk
Low Risk
Data Gaps and Uncertainty
High Risk
High Risk
High Risk
The West Ash Pond received High or Intermediate ratings for 6 of the 10 groundwater risk
classification factors, one factor was rated as Low/Intermediate, and only 3 received ratings of Low
Risk. Only 30% of the rated groundwater risk classification factors were rated Low Risk, yet
NCDEQ gave the Roxboro West Pond an overall Low Risk rating for groundwater.
The East Ash Pond received 6 High Risk ratings, one factor was rated as Low/Intermediate, and only
3 received ratings of Low Risk. High risk rankings were assigned to 60% of the rated groundwater
risk classification factors, yet NCDEQ gave the Roxboro East Pond an overall Low to Intermediate
Risk rating for groundwater.
25

GEO-HYDRO, INC
The Unnamed Eastern Extension received High risk ratings for 6 of the 10 groundwater risk
classification factors, one factor was rated Low/Intermediate, and only 3 received ratings of Low
Risk. High risk rankings were assigned to 60% of the rated groundwater risk classification factors,
yet NCDEQ gave the Roxboro Unnamed Eastern Extension an overall Low Risk Rating for
groundwater.
Table 2 provides a listing of the surface water risk classification factors and associated ratings for
each of the Roxboro ash ponds. A total of eight surface water risk factors were rated by NCDEQ for
each pond. The West Pond received High or Intermediate ratings for 6 of the 8 surface water risk
classification factors and only 2 received ratings of Low Risk. Only 25% of the rated surface water
risk classification factors were rated Low Risk, yet NCDEQ gave the Roxboro West Pond an overall
Low Risk rating for surface water.
Table 2
Surface Water Risk Factors
Unnamed Eastern
Surface Water Factors
East Ash Pond
West Ash Pond
Extension
Landscape Position and Floodplain (Key Factor)
Low Risk
Low Risk
Low Risk
NPDES Wastewater and Ash Disposal Methods
Low/ Intermediate
High Risk
Intermediate / High
Risk
Risk
Impoundments Footprint Siting in Natural Drainage
High Risk
High Risk
High Risk
Way or Stream
Potential to Impact Surface Water Based on Total
High Risk
High Risk
Low Risk
Ash Amount at Facility
Potential to Impact Surface Water Based on Dilution
High Risk
High Risk
High Risk
Development Density of Single -Family Residences
Intermediate Risk
Intermediate Risk
Intermediate Risk
along Lake/Reservoir Shoreline
Classification of the Receiving Waters
Intermediate Risk
Intermediate Risk
Intermediate Risk
Proximity to Water Supply Intake
Low Risk
Low Risk
Low Risk
The East Pond received High or Intermediate ratings for 5 of the 8 surface water risk classification
factors, one factor was rated as Low/Intermediate, and only 2 received ratings of Low Risk. Only
25% of the rated groundwater risk classification factors were rated Low Risk, yet NCDEQ gave the
Roxboro East Pond an overall Low Risk rating for surface water.
The Unnamed East Extension Pond received High or Intermediate ratings for 5 of the 8 surface
water risk classification factors and only 3 received ratings of Low Risk. Only 37.5% of the rated
26

GEO-HYDRO, INC
surface water risk classification factors were rated Low Risk, yet NCDEQ gave the Unnamed
Eastern Extension pond an overall Low Risk rating for surface water.
The preceding analysis uses the risk ratings applied by NCDEQ with no evaluation or judgment
about whether they were or were not appropriately applied. The risk ratings given to the Roxboro
ash basins demonstrate that protection of environmental and natural resources is not being treated as
priority issues by the North Carolina agency entrusted with the responsibility to do just that. The
approach utilized by NCDEQ effectively ignores impacts to the natural environmental and natural
resources, and even ignores future human users of the groundwater and surface water resources. It
appears that in the view of NCDEQ the only way that a site can be rated as Intermediate or High
Risk is if a facility is located within a 100 -year floodplain or if 11 or more people within 1,500 feet
of the compliance boundary are potentially or currently known to be exposed to ash -impacted
groundwater39. It is hard to imagine that exposed persons 1 through 10 would agree with this rating
scheme.
39 NCDEQ, 2016, page 15, Key Factors
27

GEO-HYDRO, INC
References
Duke Energy, 2014, Discharge Monitoring Reports for September, October, and November 2014.
National Pollutant Discharge Elimination System, Permit NC0003425.
NCDEQ, 2016, Coal Combustion Residual Impoundment Risk Classifications, January 2016.
SynTerra, 2014, Groundwater Assessment Work Plan for Roxboro Steam Electric Plant, Semora,
NC, September 2014.
SynTerra, 2015a, Comprehensive Site Assessment Report, Roxboro Steam Electric Plant, Semora,
NC, September 2015.
SynTerra, 2015b, Corrective Action Plan, Part 1, Roxboro Steam Electric Plant, Semora, NC,
December 2015.
SynTerra, 2016, Corrective Action Plan, Part 2, Roxboro Steam Electric Plant, Semora, NC,
February 2016.
United States Geological Survey, Olive Hill, N.C., 7.5 Minute Topographic Map, 1968, revised
1994.

GEO-HYDRO, INC
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Roxboro Steam Electric Plant

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