NC0000396_04_NCDENR DEP 11_04_2014_20150823

NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Resources
Pat McCrory
Governor
November 4, 2014
Mr. Harry Sideris
Senior Vice -President
Environment, Health, and Safety
Duke Energy
526 South Church Street
Mail Code EC3XP
Charlotte, NC 28202
RE: Duke Energy Progress, LLC
Asheville Steam Electric Plant
NPDES Permit No. NC0000396 — Buncombe County
Review of Groundwater Assessment Work Plan
Dear Mr. Sideris,
John E. Skvarla, III
Secretary
On September 26, 2014, the Division of Water Resources (Division) received the Groundwater
Assessment Work Plan (GAP) for the subject facility. The GAP was submitted in accordance
with the August 13, 2014, Notice of Regulatory Requirements (NORR) and G.S. 130A -
309.209(a)(1). After careful review, the Division has determined that the GAP is deficient in
detailing a strategy to achieve compliance with NCAC 15A 2L .0106(g), the NORR issued to
Duke, and (or) applicable general statutes. The plan as submitted fails to provide an adequate
level of detail regarding the planned assessment activities, which if left unchanged may lead to
an inadequate assessment of environmental conditions at the site. To assist you in drafting a
complete GAP, the Division offers you the following review comments which must be addressed
and incorporated into a revised groundwater assessment work plan. This review document is
separated into comments applicable to all previously submitted plans followed by comments
applicable to the referenced facility
General Comments Applicable to All Facilities
1. The Site Conceptual Model (SCM) section of the work plans does not provide sufficient
detail needed for the Division to adequately review the proposed data collection efforts.
The SCM section should include an "initial conceptual model' as described in
Groundwater Modeling Policy, May 31, 2007, page 6, paragraph 2, which states, "An
initial conceptual model should be developed from available regional and local studies
and information [existing site data], and initial site visits before significant site-specific
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data collection efforts are undertaken. This step is necessary to assure that adequate
types and quantities of data are collected..." The initial conceptual model will be refined
or modified later in the process as a result of data collection. The refined or modified
model, the SCM, will then be used as the foundation upon which any numerical models
are developed for the site. Importantly, the initial conceptual model should identify data
gaps and provide the context and rationale for the types and amounts of data collection
proposed in the work plans.
Refer to the Modeling policy, the Hydrogeologic Investigation and Reporting Policy
(May 31, 2007), and other pertinent references such as ASTM E1689-95, for the elements
expected in the initial conceptual model. Ensure also that the nature, sources, and sinks
of site contaminants of concern, along with their mobility, retention, and transport
characteristics are addressed.
2. The numerical modeling description presented in the GAP is inadequate. The draft GAP
states that fate and transport modeling will be conducted using MODFLOW and MT31)
or RT3D, with very little supporting rationale or information identified to justify the use
of the chosen model or approach. Explaining the rationale for the chosen model type and
design (including the inputs that will be needed for the model) will help make site
assessment data collection more efficient and may highlight deficiencies in the initial
conceptual model.
To provide context and rationale for the chosen model(s) and proposed data collection
efforts, provide in the GAP, at a minimum, the following information:
a) the purpose of any proposed numerical modeling,
b) the question(s) the model will help answer,
c) basic information about the model (type, boundaries, layers, whether/how
site heterogeneities will be modeled, etc.),
d) a description of the partition coefficient (Kd), how, where, and at what
depths it will be derived, and how/whether it will adequately account for
the dominant mechanisms of contaminant retention,
e) whether stream flow measurements are needed for the model and, if so,
when, where, and how those would be measured,
f) model limitations, and
g) specific data gaps (types, general locations and depths, etc) that must be
filled in order to develop the model(s).
Refer to Groundwater Modeling Policy, May 31, 2007 for the elements expected in any
numerical model developed for the site.

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3. The proposed borings, core, and well installation work are inadequate to understand,
characterize, and (or) model subsurface conditions at the sites. For piedmont and
mountain sites, the GAP shall propose field work necessary to evaluate and document the
following:
a) presence/absence, "
b) areal extent and depth/thickness,
c) flow and transport properties, and
d) heterogeneity of the following groundwater flow zones: alluvial/fluvial,
fill/residuum/saprolite, weathered rock (transition zone), and fresh,
competent fractured bedrock. Specifically, continuous core shall be
collected from land surface to a depth of at least 50 feet into fresh,
competent bedrock at a sufficient number of locations inside and outside
of ash basins to understand the flow system in areas proposed for
modeling and (or) areas of contaminant concern. All cores shall be
described/logged, photographed, and retained.
Data previously obtained from existing voluntary and compliance well borings and wells
shall also be used to understand and characterize the multipart flow system. Data
collection should also be sufficient for the development of any proposed numerical
models.
Note: Drilling and coring methods shall be used to prevent potential cross
contamination of flow zones, as stipulated in 15A NCAC 02C, and, where
applicable, to maintain structural integrity of dam.
4. Rather than abandoning the cored locations, consideration should be given to converting
borings to either a well nest/cluster or a piezometer nest/cluster. Nested/clustered wells
shall be open to each of the dominant flow zones through the use of appropriately sized
screens and discreet screened intervals and shall be installed to measure groundwater
quality and properties that may affect contaminant mobility and transport. If the boring is
not of sufficient diameter to install all of the necessary nested wells/piezometers, the
remaining wells/piezometers should be installed in the immediate vicinity.
In addition to the logging described in comment 3 above, each core location shall include
the collection of a solid phase sample at the following intervals:
a) immediately above the water table,
b) immediately below the water table,
c) within the saturated upper transition zone material (if not already included
in a) or b) above), and
d) from a primary, open, stained fracture within fresh bedrock, if these zones
exist.

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The sample(s) shall be analyzed, at a minimum, for the following:
type of material, formation from which it came, minerals present, chemical
composition as oxides, hydrous Fe, Mn, and Al oxides content, organic carbon
content, organic carbonate content, cation exchange capacity, anion exchange
capacity, surface area, moisture content, particle size analysis, Atterberg limits,
specific gravity, porosity, permeability, and any other physical properties or
analyses that may be required to estimate a batch partition coefficient Kd or
otherwise serve as input to a chosen model.
In addition, total analytes (see comment #12), SPLP analytes (see comment #12), and
speciation of selected inorganics shall be conducted for selected sample locations in
sufficient quantity and distribution to characterize the solid and aqueous chemistry and
geochemistry in locations and depths of contaminant concern, and this work shall be
clearly defined in the GAP. Inorganic speciation typically will include Fe and Mn, along
with others that may shed light on contaminant toxicity, mobility, and (or) prevailing
geochemical conditions. Sulfide and methane shall also be collected at selected locations
to evaluate geochemical conditions. Water and bed sediment samples from seeps and
streams shall be treated and analyzed in a manner consistent with the description above.
If a given analysis is believed to be unnecessary at a given location or depth based on site
conditions or assessment objectives, provide a detailed rationale for its omission for the
Division's consideration. In general, the collection strategy for ash samples from cores
inside of ash basins as described in the GAP appear to be adequate, along with the
proposed total and SPLP analyses. The need for additional core locations, where
applicable, is provided in the site-specific comment section below. Note that the chosen
numerical model(s), extent of contamination, and size of site shall drive the number,
distribution, and type of solid phase sample collection and analyses needed to understand
the retention and mobility of constituents of concern.
5. Duke shall describe the batch partition coefficient Kd, the individual inorganics that will
be tested, and whether multi -metals will be co -tested. Duke shall identify the
approximate number, distribution, and depths/flow zones of solid phase samples used to
derive the Ka(s) across the site.
6. The term "deep" as it relates to a well is subjective. For consistency and to avoid
confusion as to whether a deep well is open to transition zone material or competent
bedrock, please refer in all descriptions to each well as alluvial/fluvial, saprolite,
transition zone, or bedrock. If one or more of these zones are relatively thick, contain
more than one discreet flow zone, and should be thought of as "upper" and "lower", that
qualifying designation is also appropriate (for example, upper transition zone and lower
transition zone if the two intervals represent discreet flow intervals).
7. Surface water and bed sediment sampling are limited or are not proposed in the GAP.
The Division expects base flow surface water and bed sediment sampling to be included
in the site assessment and the GAP. These data will provide information on surface water

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quality and will be useful in efforts to understand the interaction of ground and surface
water at the site. Sample locations and distribution shall be based on site specific
considerations, but seepage areas, key tributaries, and ash ponds should be given special
emphasis. Surface water data collected by the Division during the March 2014 sampling
event, and existing ground and surface water data collected by Duke should be used in
the sample design and site assessment.
8. It is expected that Duke conduct assessment work, including borings, wells, and surface
wateribed sediment sampling, offsite (outside of property boundaries) as needed for
adherence to 15A NCAC 02L.0106 (g)(4) and (or) for the evaluation of background
conditions. The plans as submitted do not adequately account for offsite assessment
work or provide a justification that offsite work is not needed. Proposed offsite
assessment locations should be described in the GAP.
9. It is expected that as data from wells, borings, and water samples are derived and
evaluated, Duke will identify and sample additional locations as needed to complete the
horizontal and vertical extent of impacts associated with coal ash to subsurface soils,
saprolite, bedrock, and the ground and surface water resources. These activities and
anticipated locations shall be proposed in the GAP and included in the assessment.
10. Please note that wells identified as "background" are subject to periodic review based on
an increased understanding of site chemistry and hydrogeologic conditions. If a well
currently identified or otherwise labeled as background does not, in fact, represent
background conditions, it shall be excluded from further consideration as "background".
The need for additional or replacement background wells shall be considered during site
assessment and (or) as outlined in the site specific comment section below. However, in
general, each facility must have a background well or wells screened or open to each of
the dominant flow systems that occur at the site that are associated with groundwater
contamination (e.g., alluvium, fluvial deposits, saprolite, transition zone, and (or)
competent bedrock). Each of these wells must represent ambient background conditions
unaffected by site or offsite activities. Offsite well placement will, in some cases, be
expected depending on the position and proximity of waste, compliance, and property
boundaries. At least four independent sampling events generally are needed for a well to
be used in formal statistical testing.
11. Quality control samples shall be proposed in the GAP. These shall include but are not
limited to, descriptions of field calibration procedures, collection of replicate
measurements, use of field blanks, use of "blind" quality control samples, etc.

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12. The analyte list for supply well sampling, compliance well sampling, and site assessment
sampling shall include, but is not limited to, the following:
Al, Sb, As, Ba, B, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Pb, Mg, Mn, Mo, Hg, Na, Ni,
Se, Sr, Tl, V, Zn, Cl, SO4, total dissolved solids (TDS), alkalinity, bicarbonate,
carbonate, total suspended solids (TSS), turbidity, pH, temperature, specific
conductance (SC), dissolved oxygen (DO), oxidation reduction potential (ORP),
and water level (water level measurements in supply wells may be omitted if well
head hardware prevents ready access). In addition, total combined radium (Ra -
226 + Ra -228) shall be measured on at least one occasion in selected compliance
wells of highest concern at each facility. Note that 15A NCAC 02H.0804 requires
certification for field parameters.
The GAP shall include the sampling frequency for each sample type. Justification must
be provided for Division consideration for any sample types/locations in which a sample
frequency of one is proposed.
13. Duke shall list and provide a detailed description of each coal combustion residuals
(CCR) waste storage or disposal area (unit) at each facility. This description shall state
the following:
a) known or approximate quantities of CCR waste stored in the unit(s);
b) details of the operational history of the unit(s), including years of use, all
known waste types, methods of emplacement, rationale for formal or
informal closure, and methods of closure or abandonment;
c) whether the unit is already included in the facility's current NPDES
permit;
d) whether the unit was permitted and managed by an agency other than the
Division and pertinent details of that permit;
e) whether there are additional permitted or unpermitted waste storage areas
within CCR waste storage areas;
f) the location and distribution of any coal ash used as structural fill or other
construction (i.e. roadbeds, storage pads, berms, etc.) both on and offsite
(proximal to the site); and
g) whether the existing compliance boundary captures all the CCR waste
storage areas or if revisions need to be made.
Based on requirements specified in 15A NCAC 02L .0107 and a review of the
information discussed in a) to g) above, the Division will determine whether additional
units or areas need to be included in an existing or a new compliance boundary.
14. It is expected that the reporting limits associated with all analytical methods proposed in
the GAP be EPA approved and be at or below the state groundwater standards at 15A
NCAC 2L or surface water standards at 15A NCAC 2B.

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15. 15A NCAC 02C .0108(p) specifies that each non -water supply well be developed such
that the level of turbidity or settleable solids does not preclude accurate chemical
analyses of any fluid samples collected. The GAP shall acknowledge and state that well
construction design will be based on site specific conditions and shall be actively
modified in the field (alternate screen slot size, use of well sock, or others, for example)
to accommodate the grain size of the formation, as needed to minimize turbidity or
address other unforeseen issues. Any deviations from originally proposed protocols shall
be fully documented and provided to the Division.
16. The GAP shall state that well development and purging protocols will be based on site
specific conditions and shall be actively modified in the field as needed to minimize
turbidity or address other unforeseen issues. In all cases, well development and purging
prior to sample collection shall be conducted to specific field standards which shall be
clearly stated in the GAP. Deviations from this protocol or from other proposed
development and purging protocols shall be fully documented and provided to the
Division. If the Division concludes that turbidity is impacting analytical results for any
reason, a replacement well will, in some cases, be required.
17. Duke shall contact adjacent property owners for site access as needed to complete the
assessment activities. If Duke is unable to obtain access from an owner, Duke shall
request liaison assistance from the Division in writing. This request shall include all
contact information, details of all prior discussions regarding access to the property for
purposes of conducting site assessment, and results of those discussions. Duke shall
provide the Division a copy of any formal access agreements proposed for use.
18. The statewide 1:500,000 geologic map is not a substitute for local, larger scale geologic
mapping and site scale geologic information where available. The GAP shall propose the
use of fracture trace analysis (where applicable) and onsite/near-site geologic mapping to
better understand site geology. The scope of these efforts shall depend upon site
conditions and existing geologic information.
19. If proposed, please provide a detailed rationale for the use of Rotosonic or similar drill
method and why it is appropriate for use in the site assessments. Please address any
potential issues (such as the consolidation of aquifer material in the vicinity of the well
screen) that could affect aquifer or groundwater analyses.
20. The purpose, methods, and numbers (including anticipated depths/flow zone(s) and,
where known, locations) of packer testing shall be clearly detailed in the GAP.
21. The use of statistics to help establish background concentrations of specific parameters
shall be based on site-specific data and shall follow the methods approved for use by the
Division. In most cases, the methods outlined in RCRA Unified Guidance (U.S. EPA,
2009, EPA 530/R-09-007) are considered to be appropriate for use at these sites.
Background wells deemed appropriate for use in statistical analyses must be approved by
the Division. Final background determinations are made by the Division Director based
on available data and information.

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22. As part of the GAP, provide an oversized summary table of all existing compliance and
voluntary well data collected to date at the site. Please place all constituents, including
DO, SC, ORP, and turbidity, as headings across the top of the table, and all wells and
sample dates as rows along the left side of the table. Highlight in yellow those values
that exceed a 2L standard. Please also include on this table any surface water, ash, and
(or) ash leachate data relevant to the site. This table should be included in the GAP and
also made available in electronic (Excel or similar) format.
23. As part of future site assessment reporting deliverables, provide at a minimum the
following tables, graphs, and maps:
a) box (whisker) plots, for locations sampled on four or more events (show
min, 25, 50, 75, max); align plots for multiple locations on one chart;
construct a similar chart for each constituent of concern (COC),
b) stacked time -series plots (for each COC, stack multiple wells/locations
using same x-axis to discern seasonal trends; construct similar chart for
each COC; consider also showing turbidity, DO, ORP, or other constituent
on plot to demonstrate influence,
c) piper and (or) stiff diagrams showing selected monitor wells, supply wells,
surface water locations, ash leachate as separate symbols,
d) correlation charts, where applicable,
e) orthophoto potentiometric maps for "like" flow zones (maps for bedrock
wells likely will be plotted on a different map than maps for transition
zone wells),
f) orthophoto potentiometric difference maps, showing the difference in
vertical heads between selected flow zones,
g) orthophoto iso -concentration maps for selected COCs and flow zones,
h) orthophoto map showing relationship between ground and surface water
samples for selected COC(s),
i) geologic cross sections,
j) photographed borings/core for each boring location, and
k) others as appropriate.
For summary statistics tables, avoid presenting "average" value(s) unless the
constituent(s) at the location in question is (are) normally distributed, in which case a
mean and standard deviation are acceptable. For non -normal data, use of the median
value is more appropriate. In either case, use of the maximum value is often misleading
if it is a formally -tested outlier or is associated with high turbidity; footnote maximum
values as appropriate.
24. With respect to the use of the terms "may" versus "will', the GAP shall use the term
"will" or clearly state, in detail, why the qualifying term "may" is used. In either case,
the Division reserves the right to request at any time additional work needed to meet site
assessment objectives. During the assessment, if Duke decides that additional work is

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needed at a facility, the Division shall be contacted immediately with a description of the
proposed work and timeline.
25. Any assumptions or timelines stated in the GAP shall not be used as justification to
circumvent the mandatory deadlines established by legislative order, Governor's
Executive Action, or NORR.
Additional Comments Specific to the Referenced Facility
26. Note that various comments previously submitted to Duke for past coal ash -related
deliverables were not acknowledged or incorporated into subsequent documents. These
comments remain in effect, and may or may not be re -iterated in this letter. For each
review comment in this letter that is not incorporated into the final assessment plan, you
must provide a detailed rationale for its omission. These numbered responses may be
provided in a cover letter that accompanies the final work plan for each site.
27. GAP, Page 4: "CB -5 is located in an upgradient position along the French Broad River
floodplain." While C13-5 is upgradient of C13-6, it appears to be downgradient of the
1982 ash basin. The final work plan should 1) acknowledge that horizontal and vertical
flow data are very limited in this area, and 2) propose the installation of additional nest(s)
in this area to better understand horizontal and vertical flow directions.
28. GAP, Page 4: "Background well CB -9 and compliance boundary wells CB -4B and CB -8
were installed as bedrock wells." P-9: "... CB -9 being screened in weathered bedrock."
These two statements seem to contradict each other. It should be established whether
C13-9 is a competent bedrock well (open to a fracture or fracture set) or a transition zone
(weathered bedrock) well as transport properties would potentially vary significantly
between the two.
29. 15A NCAC 02L .0106(g)(5) states that the site assessment shall include "geological and
hydrogeological features influencing the movement, chemical, and physical character of
the contaminants". To meet this requirement, a clear distinction must be made between
wells in different flow zones characterized by different flow and transport properties. For
each monitor well previously installed at the site, state the flow zone(s) (fill, alluvium,
saprolite, transition zone, bedrock) across which it is screened and provide this
information in the GAP table described in comment #22. This information should also be
determined for newly installed wells and provided in the site assessment report.
30. GAP, page 8: Paragraph 1 states, "The two layers, regolithlsaprolite or alluvium, and
consolidated bedrock form the basic framework of the groundwater system. The
transition zone between regolith and consolidated bedrock can be a significant
hydrogeologic feature in the system." The Division concurs that the transition zone,
where present, represents a significant "feature" and that this feature acts as a flow zone
with dissimilar properties to that of the saprolite and to that of consolidated bedrock. The
same is true of alluvium. It follows that four dominant flow zones, each with distinct

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groundwater flow and transport properties, occur at the Asheville Plant. See comment
#3.
31. GAP, page 9: Paragraph 2 states, "CB -9 was installed in an area previously mapped as
mica gneiss; however, the cuttings during well installation appeared to represent mica
schist. " State whether and how data will be collected to conclude if a well is installed in
an area of mica gneiss or mica schist. Also explain why this may be important in the site
assessment.
32. GAP, page 10: Paragraph 4 states, "As discussed by LeGrand (2004), the French Broad
River and its tributaries are groundwater discharge zones for the saprolite and bedrock
aquifer at the site." It should be noted that LeGrand (2004) discusses generalized,
conceptual understandings of groundwater occurrence and movement in the Piedmont
and Mountain region and does not discuss conditions at the Asheville Plant. This
discussion should be amended in the GAP.
33. GAP, page 10: Paragraph 4 states, "The unnamed tributary along the southern property
line creates a hydrogeologic boundary to the south of the site." As previously noted in
our review comment letter of May 9, 2014, sufficient data do not exist to support this
conclusion. Strategically placed well/piezometer nests should be proposed at this feature
to support your conclusions. Similarly, whether or not other on- or near -plant tributaries
are hydrologic "boundaries" has not been demonstrated.
34. Site conceptualizations should not be presented as fact without supporting data as this
confuses the site record and a clear understanding of what we do and do not know about
site conditions; rather, site conceptualizations should be qualified statements or
presumptions about the system, and subject to confirmation using actual site data. This
should be noted for all subsequent deliverables, to include the GAP, site assessment
report, and others.
35. GAP, page 11: The second paragraph states, "CB -4B is screened in the first water -
bearing zone with the upper bedrock..." And the next paragraph states, "There is a
downward vertical head of approximately six feet from the lower saprolite (CB -4) to the
upper weathered bedrock (CB -4B)." These two statements seem to contradict each other.
See comment #3.
36. GAP, page 15: Paragraph 4 states, "Drilling will be extended to approximately 20 feet
below the bottom of the ash (to bedrock refusal) to allow for characterization of the
underlying native." See comment #3.
37. GAP, page 16: Section 7.3 states, "Surface water and sediment samples are not
anticipated at this time. See comment #7. Tributary, seep, and bed sediment samples
should focus on areas at the base of the 1964 and 1982 dams, in the French Broad flood
plain, and in tributaries to the French Broad River, and should be collected during base
flow conditions. These samples also should be collected near the time of well sampling

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to minimize concerns about potential temporal variability between surface and
groundwater samples.
38. GAP, page 17: Paragraph 4 states, "Outer well casings (6 -inch casing) will be advanced
to auger refusal and set approximately 2 feet into competent rock .... Air rotary drilling
(or other appropriate drilling method) will be used to advance the borehole a minimum
of 15-20 feet into competent rock with the intent of setting a 10 foot well screen at least
10 feet below the bottom of the casing." See comment #3.
39. GAP, page 17: Paragraph 5 states, "Open borehole wells may be constructed at select
locations..." State where these are proposed and what criteria will be used to determine
their need. Also, "Potentially useful logging methods include caliper, electrical
resistivity, natural gamma, ..." State the conditions under which these methods may be
appropriate and the criteria used to determine their need.
40. GAP, page 19: Paragraph 2 states, `four (4) additional well pairs are anticipated to
refine groundwater flow with the transition and bedrock zones." And paragraph 3 states,
"two (2) additional well pairs and one (1) deep well", and paragraph 4 states, "...four (4)
bedrock wells... " The final work plan should state that well nests (not "pairs") shall be
installed based on local geology encountered at the time of drilling, and shall include
dominant flow zones as described in comment #3 and #4.
41. GAP, page 19: Background Wells: See comment #10.
42. GAP, Figure 3: The figure incorrectly depicts the position of the blue band (presumably
the French Broad River). Monitor wells CB -5, CB -6, and CB -7. CB -5, CB -7, and the
property boundary are depicted in the river.
43. GAP, Figure 4: Well locations: To better define horizontal and vertical flow gradients
and chemistry in selected areas, additional borings and monitor well/piezometer nests
should be located as follows, to augment the locations depicted in Figure 4:
a) east of CB -1,
b) south of CB -2 and north of the unnamed tributary,
c) approximately midway between CB -3 and CB -4,
d) just southwest of the toe of the 1982 dam, immediately adjacent to the
iron -stained seepage/spring area west-southwest of AW -2213,
e) south-southeast of CB -5,
f) approximately midway between CB -5 and CB -6,
g) between CB -6 and the French Broad River (FBR),
h) approximately midway between CB -7 and AW -9,
i) approximately midway between AW -7 and AW -8, and
j) west of CB -8 and beside the FBR.

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If a given boring or nest is believed to be unnecessary based on site conditions or
assessment objectives, provide a detailed rationale for its omission for the Division's
consideration.
44. GAP, Figure 4 and Table 3: Well sampling and analyses: Each of the nests installed as
part of comment #18, along with all wells currently depicted on Figure '4, should be
sampled synoptically for water chemistry (see comment #12 for list of required analytes).
In addition to those analytes listed in comment # 12, the Division concurs with the
proposed analysis of methane, sulfide, bromide, and total organic carbon. If the sampling
of a specific well is believed to be unnecessary based on site conditions or assessment
objectives, provide a detailed rationale for its omission for the Division's consideration.
If a specific analyte(s) at a specific well is (are) believed to be unnecessary based on site
conditions or assessment objectives, provide a detailed rationale for its omission for the
Division's consideration.
45. GAP, Figure 4: Ash basin sample locations. To ensure an adequate distribution of ash
basin sample locations:
a) AB -1 should be moved north about 200 feet,
b) AB -3 should be moved about 500 feet to the south east,
c) AB -7 should be moved about 300 feet east-southeast,
d) an additional location should be added in the southwestern corner of the
1982 basin, and
e) an additional location should be added in the center of the 1982 basin.
46. GAP, page 21: Geologic cross sections are needed to understand subsurface fill, source
areas, historic stream channels, and the geology comprising the multipart flow system
along important transects at the site. A cross section is needed approximately 700 feet
northeast of, and parallel to, 13-13% crossing through both ash basins. A cross section is
also needed close to, and approximately parallel to, the FBR. A cross section is needed
along the dominant flow direction from contamination in the vicinity of CB -3/3R to the
FBR. And a cross section is needed along the dominant flow direction from the area of
contamination around in the vicinity of CB -8 to the FBR. Geologic cross sections are
expected along any transects that are numerically modeled.
47. Surface geophysics is often an effective tool to help with subsurface mapping. In many
cases, it may be used to better define the occurrence and depth of fill, regolith, and
bedrock. In some settings it may also be used to provide information about the water
table. Given the size of the site and the complex subsurface, Duke should evaluate the
use of geophysics in selected areas of the facility.
Your assessment plan must be submitted to the DWR Asheville Regional Office and Central
Office for review within 30 days of the receipt of this letter. A revised plan must be submitted
that fully incorporates the responses to the above comments rather than a letter response
intended to supplement the previously submitted plans.

Duke Energy Progress, LLC - Asheville
November 4, 2014
Page 13 of 13
Please note that failure to conduct a complete assessment pursuant to the above referenced rule
and statute will be considered a violation, subject to potential enforcement actions by the
Division.
We appreciate your attention and prompt response in this matter. If you have questions, please
do not hesitate to call Ted Campbell at 828-296-4500.
Sincerely,
S. Jdf Z#=erman, P.G., Chief
Water Quality Regional Operations Section
Cc: WQROS — ARO
WQROS — Central Office
Don van der Vaart
Synterra (Attn: Kathryn Webb) —148 River Street, Suite 220, Greenville, SC 29601