NC0024406_BCSS_Appendix B_20191231

Corrective Action Plan Update December 2019
Belews Creek Steam Station
APPENDIX B
SynTerra
COMPREHENSIVE SITE ASSESSMENT UPDATE
REPORT REVIEW COMMENTS AND RESPONSES

NC; -
Water Resources
Environmental Quality
April 26, 2018
Paul Draovitch
Senior Vice President
Environmental, Health & Safety
Duke Energy
526 South Church Street
Mail Code EC3XP
Charlotte, North Carolina 28202
Subject: 2017 Comprehensive Site Assessment Update Comments
Belews Creek Steam Station
Dear Mr. Draovitch:
ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Interim Director
On October 31, 2017, the North Carolina Department of Environmental Quality's (DEQ's) Division of
Water Resources (DWR) received the 2017 Comprehensive Site Assessment (CSA) Update report for the
subject facility. Based on the review conducted to date, DWR has concluded that the sufficient information
has been provided in the report to allow preparation of the Corrective Action Plan (CAP); however, there
are deficiencies that must be addressed prior to or in conjunction with preparation of an approvable
Corrective Action Plan (CAP).
As described in the attached itemized list of CSA Update Report Comments (Attachment 1), additional data
and/or data analysis will be needed to address data gaps, complete evaluation of exposure pathways, predict
time and direction of contaminant transport, and ultimately refine remedial design. The assessment of all
primary and secondary source areas (including, but not limited to, impoundments, landfills, ash storage
areas, ash stacks, structural fills, coal piles, and contaminated soils) must be included in the CAP's by
August 31, 2018, or in a CAP amendment. The DWR expects that information collected regarding the
source areas will be used to formulate the CAP recommendations. For source areas where this may not be
possible or areas where pollutants may be hydraulically isolated, please contact me to discuss.
In a letter dated December 5, 2017, Duke Energy proposed a CAP submittal date of May 31, 2018.
However, due to the additional requirements stated above, and the time it took the DEQ to generate
comments, the updated CAP for the Belews Creek facility will be due on August 31, 2018.
An overview of CSA Update report deficiencies includes the following:
• The report contents are presented in a data summary format, exhibiting a lack of conclusive data
analysis and interpretation of site conditions.
• This report fails to fully integrate and evaluate data collected from previous versions of the CSA
reports for the facility.
• The distribution of constituents of interest related to coal ash sources presented in the report often
fail, for at least some areas of the site, to fully and clearly acknowledge and delineate exceedances
of the 15A NCAC 2L or 2B standards above background levels.
--'Nothtng Compares
State of North Carolina I Environmental Quality I Division of Water Resources
Water Quality Regional Operations Section
1636 Mail Service Center I Raleigh, North Carolina 27699-1636
919-707-9129

• The characterization of other primary and secondary sources other than impoundments that
contribute to the groundwater plumes is inadequate, particularly near the chemical pond.
• As detailed more fully in the attached document, additional data gaps remain concerning
delineation of impacts from coal ash at the facility.
The deficiencies related to the site assessment at the facility, including those related to primary and
secondary sources other than impoundments, may limit the cleanup remedy and site management strategies
for a source area. The lack of a well -documented interpretation of the existing data, or missing data that
DEQ believes should be collected to support proposed corrective action, may result in the DEQ approving
corrective action measures that comply with the rules, but may not be the most cost-effective. For example,
monitored natural attenuation cannot be approved for source areas where no surface water samples have
been collected (but could be collected) that demonstrate the groundwater discharge does not result in
exceedances of 15A NCAC 2B .0200 regulatory standards.
The evaluation of preliminary background threshold values developed for the facility as part of the 2017
CSA Update report will be provided to Duke Energy as part of a separate correspondence.
The DEQ would like to schedule a meeting between upper level management from DEQ and Duke Energy,
including select technical staff, to discuss the more significant deficiencies associated with the CSA
submitted October 31, 2017. We will reach out to Duke in the next several days to schedule the meeting at
the earliest possible time. Duke Energy should contact the Winston-Salem Regional Office to initiate the
scheduling of additional meetings between DWR and Duke Energy's technical staff (including contractors)
to discuss deficiencies in greater detail. Promoting regular dialogue in a small group format assists in
addressing questions and problems that may come up during the development of the CAP, and better
ensures that Duke Energy is meeting DWR's expectations.
If you have any questions, please feel free to contact me at [phone]. Please contact Shuying Wang
(Winston-Salem Regional Office) at [phone] to discuss the CSA Update report deficiencies and
data gaps in more detail.
Sincerely,
S. Jay Zimmerman, P.G.
Division of Water Resources
Attachments: Attachment 1 Belews Creek Steam Station CSA Update Report Comments
cc: WSRO WQROS Regional Office Supervisor
WQROS Central File Copy

Comments for Belews Creek Steam Station Comprehensive Site Assessment Update
Submitted October 31, 2017
Groundwater Incident No.: 88227
Delineation of Groundwater Contamination
Questions remain concerning the accuracy of the delineation of horizontal and vertical extent of
groundwater contamination, which is a requirement of Coal Ash Management Act (CAMA) and
15A NCAC 02L .0106. The CAP shall include updated maps and data summary that address the
following:
■ The plume morphology of some constituents (beryllium, boron, and selenium in the
shallow zone, iron and vanadium in the deep zone, and thallium in both the shallow and
deep zones) are irregular and exhibit variable ranges of concentrations in the northwestern
area, which implies complex hydrogeological and geochemical conditions exist at this
portion of the site. This complexity with respect to contaminant distribution suggests that
more appropriately located downgradient well(s) are necessary to confirm site conditions
although coal combustion residuals (CCR) data does show that boron in GWA-19 is
sourced by the ash basin. For the same reason, it appears necessary to install a well(s)
downgradient from GWA-21 S to further delineate beryllium and thallium plumes. If
groundwater flow and fate/transport models do not indicate that the plumes will be
migrating off the property or causing any 02B violations, the installation of the additional
wells further downgradient may not be urgent or may not have to be done before the CAP,
but will have to eventually be installed for performance monitoring.
• High levels of boron have been consistently measured in MW-2-7 (22,700 µg/L, April 11,
2017) at Pine Hall Landfill. To determine the vertical extent, at least one additional
bedrock well appears to be needed. This was not requested earlier because the data from
the North Carolina Department of Environmental Quality (DEQ), Division of Waste
Management (DWM) was expected as this part assessment. If no additional deep or
bedrock well data from DWM can be provided, at least one deep or bedrock well is needed.
• In addition, boron was detected in CCR-6D at a concentration as high as 12,400 µg/L,
which also indicates that the vertical extent should be further delineated. A paired bedrock
well nest should be installed.
• With regards to porewater analysis, interpretations of site conditions that include analytical
results from specific sample locations (well IDs) are needed to justify the broad statement
regarding the decrease in concentrations. As the ash basin is an active basin, the cause for
decreasing concentrations in porewater should be evaluated, including implications for
constituent of interest (COI) concentration distribution and mobility.
• Provide an interpretation as to how the geochemical conditions affect or control the
distribution of COIs with site specific data (COI concentrations vs geochemical parameter
levels, identified with well IDs).
• Whether 11,200 µg/L of boron at GSA-20SA (Fig. 10-17) would drop to 852 µg/L at
GWA-11 S, and 184 µg/L at GWA-21 S through dilution alone should be discussed.
Whether the well positions or screened intervals of GWA-11 S and GWA-21 S are
measuring the flow path away from the hot spot should be discussed.
• High boron concentrations were detected in deep wells (e. g., 9,890 µg/L at GWA-20D and
5,420 µg/L at GWA-27D), but no 02L exceedances were measured in their paired bedrock
Page 1 of 4

wells. Whether these results are supported by site hydrogeologic conditions, such as
vertical hydraulic gradient and conductivity, should be discussed.
• For each water supply well that exhibits concentrations of constituents exceeding
02L/IMACs or preliminary background threshold values (PBTVs), whichever are higher,
provide an evaluation concerning potential receptors based on actual site data including
piper -diagrams, co-occurring constituents, proximity to CCRs, topographic setting,
geology, and dissolved oxygen, pH, etc.
• Provide an explanation why radium is not considered a COI.
• The pH values observed in GWA-19BR, GWA-20BR, and especially GWA-2713R, (the
most downgradient bedrock well in the northwest area) are consistently high likely due to
improper well construction. Whether these wells should be replaced needs to be discussed.
Other Potential Primm and Seconds Sources
As discussed previously, other primary and secondary sources must be assessed regarding impacts
to groundwater. Sources contributing to groundwater contamination associated with the
impoundments (commingled) must be assessed and the results incorporated into the CAP. Sources
that have impacted, or have the potential to impact groundwater (contaminated soils, stockpiles,
etc.) that are not known or believed to have commingled with the areas impacted by the
impoundment may be assessed separately in accordance with a schedule approved by the
Department. Additional information needed includes, but is not limited to, the following:
• Soil contamination should be delineated to either the site -specific preliminary background
concentrations (PBTVs) or Protection of Groundwater (POG) Preliminary Soil
Remediation Goals (PSRGs)levels, whichever are higher. If appropriate, use the equation
provided in the PSRG table to establish a POG PSRG for a constituent with 02L standard
that does not have one.
• Provide plan view maps and cross -sections (where applicable) to demonstrate that soil
contamination (POGPSRGs or PBTVs, whichever are higher) has been vertically and
horizontally delineated.
• Provide additional assessment concerning the comingling of plumes from the onsite
Structural Fill with the ash basin. To determine whether the contaminated groundwater
from the Structural Fill contributes to the plume resulted from the ash basin, at least, an
additional monitoring well between GWA-8S and the Structural Fill, but at the northern
side of Pine Hall Road, should be installed. The result will help determine whether the
source of boron in GWA-8S is from the ash basin or the structural fill. Sampling results
from SFMW-1D and SFMW-2D and bedrock well (expected from DWM) are also needed
to determine the vertical extent of the plume from the Structural Fill.
• Whether additional sediment assessment is needed at S-6, S-10, S-11, BCSW-007, BCSW-
008, and BCSW-19 area should be discussed.
• Please provide a description of the Chemical Pond in terms of its content, history, and
function relative to the NPDES permit.
• Provide an explanation of how and why soil contamination occurs outside of any waste
boundaries and more detailed discussion or evidence as to the reason for the elevated
concentrations of chromium, iron, strontium and vanadium in soils upgradient of the ash
basin (GWA-6S, GWA-7S and GWA-813).
Page 2 of 4

Maps, Figures, and Tables
Additional tables, maps and figures are necessary to better represent an understanding by Duke
concerning the horizontal and vertical extent of soil and groundwater impacts, associated risks to
receptors, secondary source impacts, etc. These include but are not limited to:
• Isoconcentration maps: If a well was sampled, even when pH was elevated, the data should
be used to plot isoconcentration maps with footnotes that explain that better quality data
are needed to provide a more accurate assessment of site conditions. In addition, as a
certain number of wells were not sampled in April 2017, the isoconcentration maps may
not represent true site conditions (plume shape and size). Therefore, all isoconcentration
maps should be updated with a complete sampling event including all wells, (including
CCR wells, if appropriate) and present the updated maps in the CAP. Otherwise, if the
maps could not be updated with adequate data, please provide isoconcentration maps for
each sampling event for boron. Furthermore, assumptions made concerning r how
groundwater plumes are depicted without a monitoring well in the middle of the ash basin
or the landfill should be provided. For examples figures 10-44, 10-54, etc.
• Figure 2-10 should be updated to include all CCR well locations.
• Additional comments regarding figures and tables can be discussed in detail between
WSRO and Duke Energy staff prior to completing the CAP.
02L/02B Surface Water Samplinx
Collection of surface water samples to evaluate impacts from contaminated groundwater is
necessary to understand the impacts associated with the migration of contaminants from the
groundwater system. Failure to adequately characterize known and potential impacts to surface
waters from groundwater will affect the corrective action strategies that can be proposed and
ultimately considered for approval by the Department. Comments include, but are not limited to,
the following:
• Additional surface water sampling along the east bank of Belews Reservoir was discussed
in May 18, 2017 meeting between Duke and DEQ. A sampling proposal was submitted by
Duke through an email on October 4, 2017 and agreed to by the division staff, however,
the proposed sampling was not performed. The additional agreed upon surface water
assessment must be completed and included in the CAP. All samples must be collected in
accordance with DEQ's Internal Technical Guidance: Evaluating Impacts to Surface
Water from Discharging Groundwater Plumes.
• For any sample results deemed invalid, state what caused the sample to be invalid, the
rationale for not including the data, and any proposed remedies such as plans for
resampling. (Refer to Section 9.1).
Groundwater Flow Contaminant Flow, and Trans ort
Additional information related to groundwater flow and the mechanisms affecting contaminant
migration is necessary, including but not limited to, the following:
• Provide a rationale or evidence that suggests that underground utilities will not serve as
preferential conduits for contaminant movement.
Page 3 of 4

• Section 6.5 states: "Hydraulic conductivity values for wells screened in saprolite have a
geometric mean of 2.65 x 10-4 cm/sec. Hydraulic conductivity values for wells screened in
the transition zone have a geometric mean of 7.91 x 10-5 cm/sec. These measurements
reflect the dynamic nature of the transition zone, where hydrologic properties can be
heavily influenced by the formation of clays and other weathering by-products. " To justify
this statement, please provide evidence showing the transition zone has higher clay content
and other weathering by-product than the shallow aquifer at this site as hydraulic
conductivity is lower in the transition zone than in the shallow aquifer.
• Provide an explanation or documentation concerning the statement (Section 6.6) that
bedrock fractures tend to be isolated with low interconnectivity and the primary porosity
is considered negligible, and correlate the statement to horizontal and vertical migrations
of COIs in the bedrock.
Mo— delin-
Additional information needed includes the following:
• Both groundwater and geochemical models must be updated and included in the revised
CAP due August 31, 2018.
• All COIs should be modeled unless a rationale for not doing so is provided.
• In Section 3.3, implications for leachability and downgradient mobility of contaminants
from the source area should be discussed, as well as, implications for transport model
source inputs and for transport and risk should be discussed.
• In Section 4.4, it should be discussed whether the effects of pumping from the private water
supply wells were accounted for in the model with regards to particle tracking.
• Groundwater divides that have been identified at Pine Hall Road and Middleton Loop Road
(Section 6.3) should be reconsidered, because existing information confirms groundwater
beneath the ash basin flows across Middleton Loop Road towards northwest. Whether there
is uncertainty with respect to the position of groundwater divides for modeling particle
tracks or transport should also be discussed.
Risk
• The updated status of alternative water supply for supply wells within 0.5 miles of the BC
indicates that 52 households are eligible, 41 selected water filtration systems, 6 opted out
of selections of water line and water filtration system (refused both), and 5 did not respond.
Please list names and addresses of these 11 households and identify these property on the
map. In addition, please also list the name and address for each vacant lot within 1500 feet
of CB and show them on the map.
• Each of the constituents of concern identified in CAP Part 2 report that exceed their
respective risk target should be discussed.
Page 4 of 4

From: Smith, Eric G[mailto:[e-mail]]
Sent: Wednesday, May 23, 2018 12:07 PM
To: Toepfer, John R; Sullivan, Ed M
Cc: Zimmerman, Jay; Wang, Shuying; Knight, Sherri; Risgaard, Jon; Lanter, Steven
Subject: Duke Coal: Belews Creek Full Draft Comments for Discussion Friday
*** Exercise caution. This is an EXTERNAL email. DO
NOT open attachments or click links from unknown
senders or unexpected email. ***
John & Ed:
As promised, attached are the full set of comments prepared by WSRO on the Belews Creek Steam
Station Updated CSA Report. These comments will serve as basis for discussion during this Friday's
technical meeting at the Winston-Salem Regional Office.
-Eric G. Smith
Eric G. Smith
Program Consultant
Division of Water Resources
Water Quality Regional Operations Section
Animal Feeding Operations & Groundwater Protection Branch
Department of Environmental Quality
919 807 6407 office
eric.g.smith(@ncdenr.gov
512 N. Salisbury St
1636 Mail Service Center
Raleigh, NC 27699-1636
> Nothinq ConTares ,
Email correspondence to and from this address is subject to the
North Carolina Public Records Law and may be disclosed to third parties.

Draft Comments about the CSA Update Report, October 31, 2017, Belews Creek Steam Station
Groundwater Incident No.: 88227
(Note, text noted as Italics are cited directly from the report or other documents)
I. General:
1. The CSA is still incomplete. Delineation of horizontal and vertical extent of soil and groundwater
contamination is required by CAMA and 2L and has been highlighted since August 13, 2014
when the Notice of Regulatory Requirements was issued to Duke Energy for its 14 facilities. As
noted, plume shapes (beryllium, boron, and selenium in shallow zone, iron and vanadium in
deep zone, and thallium in shallow and deep zones) are so irregular and concentrations varied
dramatically in the northwest area, which implies complex hydrogeological and geochemical
conditions. Therefore, additional further downgradient well(s) appears to be necessary
although CCR data does show that boron in GWA-19 is sourced by the ash basin. Based on the
plume occurrence, GWA-31 is a side -gradient well, not a directly downgradient well. For the
same reason, to further delineate beryllium and thallium plumes, a further downgradient well
from GWA-21S appears to be needed.
2. Vertical extent: High level of boron has been consistently measured in MW-2-7 (22700 µg/L,
April 11, 2017) at Pine Hall Landfill. To determine the vertical extent, a bedrock well appears to
be needed. This was not requested before because it was thought to be addressed by DWM as
this part assessment is overseen by DWM. In addition, boron was detected in CCR-6D at a
concentration as high as 12400 µg/L. If it is safe (at the foot of the main dam), a paired bedrock
well should be installed.
3. How much additional data we can gain from DWM assessment at the Structural Fill? Whether
the contaminated groundwater from the Structural Fill contributes the plume caused from the
ash basin needs to be determined before CAP development. Sampling results from SFMW-1D
and SFMW-2D and bedrock well may be needed to determine the vertical extent. In addition, at
least, an additional monitoring well between GWA-8S and the Structural Fill, but in the
northside of Pine Hall Road, appears to be needed to determine the source of boron in GWA-8S
or whether plumes are comingled.
4. Plan view maps and cross -sections are needed to show that the soil contamination
(concentrations exceed Protection of Groundwater (POG) Preliminary Soil Remediation Goals
PSRGs or Provisional Background Threshold Values (PBTVs), whichever are higher) has been
vertically and horizontally delineated.
5. The Chemical Pond should be further characterized as a source, including information such as its
content, history, and whether it was a component of the NPDES permit permitted waste water
system.
6. In addition, to investigate any 2B violations that maybe caused from groundwater discharge,
additional surface water sampling along the east bank of Belews Reservoir was discussed in May
18, 2017 meeting between Duke and DEQ. Subsequently, a sampling proposal was submitted by
Duke through an email on October 4, 2017. However, the proposed sampling was not
performed, but more were proposed in the report. Need to know the result or status of the
proposed sampling.
7. Whether plumes of boron, chloride, and other COls are still expanding or moving should be
thoroughly evaluated.

8. The pH value in GWA-19BR, GWA-20BR, and GWA-27BR, especially GWA-27BR, the most down
gradient bedrock well in NW is consistently high. Whether these wells should be replaced need
to be discussed.
9. Updated status of alternative water supply for supply wells within 0.5 miles of BC indicates that
52 households are eligible, 41 selected water filtration systems, 6 opted out of selections of
water line and water filtration system (refused both), and 5 did not respond. Please list names
and addresses of these 11 households and identify these property on the map. In addition,
please also list the name and address for each vacant lot within 1500 ft of CB and show them on
the map.
10. Document "no impact" to each private supply well which contains constituents that were also
found in coal ash and exceeds 2L/IMAC or PBTV, whichever is higher, by providing pieces of
evidence, such as geology, hydrogeology, geochemistry, etc.
11. Provide specific evaluation for water supply wells BC1 and BC13 is needed. These two wells may
be potentially impacted from groundwater impacted by coal ash. BC1 is relatively close to the
ash basin and upward hydraulic gradient was measured in the area. Boron was detected in BC-
13.
12. Whether plumes of boron and chloride are still expanding or moving should be thoroughly
evaluated, and conclusions should be made. Representative wells should be selected for trend
analysis (i.e. increasing/decreasing COI trends).
13. Whether 11,200 µg/L of boron at GSA-20SA (Fig. 10-17) would drop to 852 µg/L at GWA-11S,
and 184 µg/L at GWA-21S through dilution alone should be discussed. Whether the well
positions or screened intervals of GWA-11S and GWA-21S are measuring the flow path away
from the hot spot should be discussed.
14. High boron concentrations were detected in deep wells (e. g., 9890 µg/L at GWA-20D and 5420
µg/L at GWA-27D), but no 2L exceedances were measured in their paired bedrock wells.
Whether these results are supported by site hydrogeologic conditions and/or groundwater
hydraulic property, such as vertical hydraulic gradient and conductivity, should be discussed.
15. Isoconcentration maps: If a well was sampled, even pH was elevated, the data should be used to
plot isoconcentration maps with noting until good data is available. In addition, as a certain
number of wells were not sampled in April 2017, isoconcentration maps should be plotted with
considering historical data; otherwise, plume occurrences may not be representative. For
examples figure 10-7, figure 10-10, etc. Furthermore, attention should be paid for how
groundwater plumes should be drawn without a monitoring well in the middle of the ash basin
or the landfill. For examples figures 10-44, 10-54, etc. Representative cross sections should be
selected for assessment of vertical extent.
16. Whether the raw coal pile area should be assessed needs to be discussed. Plumes of cobalt,
manganese, strontium may be sourced by the coal pile.
17. Figure 2-10 should be updated to include all CCR well locations.
18. Synterra must review and certify that the data and evaluations contained in this report are
accurate and correct no matter who performed previous work. (Note, at very beginning of the
report, Work Performed by Others: "The seal of the licensed geologist for this CSA applies to
activities conducted and interpretations derived after the HDR reports were submitted. This
submittal relies on the professional work performed by HDR and references that work.")
2

II. Section Specific Comments:
1. Executive Summary
a. ES.3.2. "Although several water -supply well concentrations reported are greater
than the site specific provisional background threshold values (PBTVs), the
concentrations are within the background concentration range for similar Piedmont
geologic settings." This statement is too general. Please note that no concentration
range for similar Piedmont geologic setting is provided rather than PBTVs from 11
Duke Energy coal ash sites simply piled and presented in Section 4. These sites are
in different geologic setting or hydrogeologic units, so concentrations of trace
metals in groundwater can be different.
b. ES.3.3. "Several surface water bodies flow from the topographic divide along
Middleton Loop Road toward the Dan River within a 0.5-mile radius of the ash
basin." The word "several" should be replaced by a numerical number. Whether
they are permitted effluent channels or jurisdictional waters should be clarified. If
these are jurisdictional waters, whether they are impacted by CCR should be
summarized.
c. ES.3.4. "Water -supply well data collected since the risk assessment was completed
indicates several wells located to the west-southwest and northeast of the ash basin had
concentrations of chromium, cobalt, iron, manganese, vanadium that exceeded their
respective water quality standards, however all reported concentrations were less than
their respective EPA risk -based tap waterscreening levels." As these metals are
discussed, arsenic detected in six wells above 2L Standard should also be mentioned.
Their EPA risk -based tap water screening levels should be given or the source should be
referred.
d. ES.4.2. As discussing extent of contamination, the vertical extent and concentrations at
the deepest depth for each COI at the site should be summarized. Please also note that
"Cobalt exceedances were not reported in the deep and bedrock flow layers." is not true.
It may not be detected at or beyond the compliance boundary, but was detected above
its PBTV/IMAC in several deep wells and one bedrock well, AB-113R, within the ash basin.
e. ES.4.3. Maximum Contaminant Concentrations (Source Information), please note that
no maximum contaminant concentrations were mentioned under this paragraph at all.
f. ES.S
• "The BCSS ash basin is currently designated as "Intermediate" risk under CAMA,
requiring closure of the ash basin by 2024. However, groundwater and surface
water quality data provide no indications of potential risk to human and wildlife
receptors related to constituent migration through the groundwater pathway
from the ash basin. These findings support a proposed "low" risk classification."
Please note that to lower the site risk classification to Low, the site needs to
meet all criteria set in CAMA. In addition, "21_-213" sampling support is needed,
but has not been completed. More thorough evaluation of each water supply
well containing exceedances of 2L/IMACs is also needed.
3

• "Boron, beryllium, chloride, chromium, cobalt, manganese, and thallium are the
primary constituents detected in groundwater greater than PBTVs and 2L/IMAC
near or beyond the compliance boundary." Why is only primary and why only
these constituents are considered primary? All COls that need remedial actions
should be listed here.
g. Figure ES-1
• The model does not reflect groundwater flow directions very well.
Groundwater does not only flow N. NW, but also E. In addition, based on
groundwater elevation contour maps, (figures 6-6 through 6-11) and boron
detected in GWA-8S, Pine Hall Road may not be a groundwater divide.
• In addition, the boron plume caused from Pine Hall Road Landfill should be
extended further to SW beneath the landfill unless there is a monitoring well in
the middle of the landfill and does not indicate boron detection.
• The edge -line of the plume next to the Structural Fill should not be closed
because the structural fill is considered the source of the plume.
h. As noted on Figure ES-1 (and some other later figures), streams were from AMEC NRTR
REPORT, 2015. Please include the AMEC report into Reference section.
2. Section 2
a. Figures 2-2 to 2-4, with all features loaded, are hard to see original features existed at
the time photo was taken or changes in land use from 1951 to 1977. Please remove all
overloaded layers but the waste boundary of the ash basin and Duke's property line.
b. The unnamed streams shown on figures 2-6 and 2-7, and other relevant figures in later
sections, should be consistent or the same. As the Dan River is the NPDES permitted
receiving stream and a potential groundwater discharge receptor, please consider
making it visible on all relevant figures/maps if possible.
c. Can figure 2-10 also show locations (borings) where Kd samples were collected?
Otherwise, a separate figure for Kd sample location and depth should be provided.
d. 2-2. "... (Figure 2-7). Natural topography at the BCSS site ranges from an approximate
high elevation of 878 feet (NAVD 88) southeast..." Should be the last word southeast be
southwest?
e. 2-5. "The Craig Road Landfill, FDG Landfill and the structural fill are located south of the
ash basin and are not hydrogeologically connected to the ash basin". If boron detected
in GWA-8S is from the structural fill, the structural fill may be hydrogeologically
connected to the ash basin; to determine, whether boron in GWA-8S is from the ash
basin or the structural fill needs to be further investigated.
3. Section 3
a. "For the BCSS site, sources include the ash basin, Pine Hall Road Landfill, and the former
chemical pond." More information about the former chemical pond is needed. As a
source, it should be discussed as Ash Basin or Pine Hall Road Landfill was in this section.
b. 3.3
4

• The total volume of coal ash and the volume of saturated ash should be
estimated, respectively. If de -watering is done, the amount of saturated ash
remaining should also be estimated.
• "Concentrations of arsenic, boron, chromium, cobalt, iron, manganese,
selenium, and vanadium were reported above soil background concentrations
and the North Carolina Preliminary Soil Remediation Goals (PSRGs) for industrial
Health and/or Protection of Groundwater for ash samples collected within the
ash basin waste boundary (Appendix B, Table 4)." As characterizing the source,
concentrations of these contaminants and the volume of contaminated soil, the
secondary source, should be discussed.
• "The results of the SPLP analyses indicated that antimony, arsenic, chromium,
cobalt, iron, manganese, selenium, thallium, and vanadium exceeded their
respective 2L Standard or IMAC." In addition to this simple data summary,
implications for leachability and downgradient mobility from the source area
should be discussed; implications for transport model source inputs and for
transport and risk should be discussed.
• "Background soil SPLP data collected from various sites in the Piedmont is
presented as Table 3-3." Note that no Table 3-3 is provided in this report.
• "The following metals leach from naturally occurring soils in similar geologic
settings at concentrations greater than 2L or IMAC: barium, chromium, cobalt,
iron, manganese, nickel, thallium, and vanadium." Please provide a table listing
both background soil and coal ash SPLP data. Please also explain what is meant
by "similar geologic settings".
• "The pore water sampling results show a decrease in constituent concentrations
at some locations with most locations showing stable concentrations. No
significant increases in constituent concentrations were observed." This
statement needs to be supported with values and wells from which the values
were measured and trend plots. Implications should also be discussed. Data is
needed to support "no significant increases".
• "The ash pore water is generally anoxic to mixed (oxic-anoxic)." Where does it
vary from this and why and how does this relate to COI concentration
distribution and mobility should be discussed.
• "Ash pore water at BCSS for AB-4S, AB-7S, and AB-8S resembles bituminous coal
ash leachate water from EPRI's 2006 study which is a calcium -magnesium -
sulfate water type. In comparison, BCSS ash pore water from AB-6S and AB-8SL
have an elevated bicarbonate component." What caused the change and what
are the Implications should be discussed.
4. Section 4
a. "It is anticipated that any underground utilities present at the site would not act as
potential preferential pathways for contaminant migration through underground utility
corridors to water supply well receptors." Rationale or evidence is needed for this
statement.
b. 4.2
5

c. 4.3
• "Based on the report, 19 of the 58 households surrounding BCSS have been
recommended for installation of an individual filtration system." Why only 19
have been recommended? What status or what is the problem with the rest of
households should be discussed. Please provide a table listing the status of
each well. The wells/households who are not willing to have a filtration system
to be installed should be identified.
• "Several surface water bodies that flow from the topographic divide along
Middleton Loop Road toward the Dan River were identified within a 0.5-mile
radius of the ash basin." As surface waters may be potential receptors, all
jurisdictional water bodies within 0.5 miles should be shown on a map or Figure
4-2. Each of surface water bodies should be identified with its classification and
distance from the compliance boundary. Whether it has been impacted by
groundwater from the ash pond should be discussed.
• For each supply well, what co-occurring CCR constituents were found in the well
and whether these constituents were sourced by the coal ash basin or other
coal ash fills should be discussed.
• 'Based on the bedrock groundwater flow direction at the site (Figures 6-10 and
6-11, ... The remaining water supply wells identified in the area are located
upgradient or sidegradient substantially beyond the expected flow zone of the
BCSS ash basin." Please discuss whether pumping affects are considered and on
what basis the "expected flow zone" extent was determined. More attention
should be paid on BC1. It is not far from the compliance or waste boundary and
elevated manganese was detected in it.
• 'Boron was not detected in any of these water supply wells sampled
sidegradient of the ash basin along Old Plantation Road." Whether boron was
detected in other supply wells should be also mentioned here.
• Figure 4-3, why only these three supply wells (13C2 (well 1&2) and BC-2019) are
shown in the figure? If not all, at least BC4, BC4A and BC413 should be included
as they are located right downgradient of Pine Hall Road Landfill.
• Whether boron detected in BC13 is an indicator of impact of coal ash should be
discussed. If it cannot be determined, the well should be monitored regularly.
• PBTVs presented in Table 4-4 should be consistent with values presented in
later other tables. For example, manganese PBTV for Deep flow layer 55 ug/L is
in Table 4-4 while it is 13 µg/L in Table 10-2.
• Please provide a table comparing the background concentration range for
similar Piedmont geologic setting (must be from the similar geologic setting) to
each water supply well constituent with concentration exceeding the bedrock
PBTV or 2L standard, whichever is higher.
d. 4.4. "The reverse particle tracks did not reach the BCSS Compliance Boundary, indicating
the water supply wells located beyond the compliance boundary did not have ash -
related impacts (Figure 4-2). With this statement, whether the model account for water
supply well pumping influences and limitations of the flow model and of using particle
track analysis on bedrock wells should be discussed.
0

e. 4.5
• Whether there are any intakes for drinking water supply from downstream of
permitted outfall 003 at the Dan River should be documented, and if there is
any, what is the distance to the intake for the closest intake?
• Whether Belews Reservoir is a potential receptor or has been impacted by coal
ash basin should be further evaluated with additional sampling.
5. Section 6
a. 6.1.3. Information and summary on structural geology are good, but should be related
to local site conditions and, most importantly, to potential contaminant movement,
which was not done.
6.1.4. "Results also indicate a significant composition of MnO from both the BCSS soils
and transition zone with ranges from 0.03% to 0.1% for soils and 0.05% to 0.14% for
transition zone." Why this composition at these levels are considered significant and its
context/implications should be discussed.
c. 6.1.6. A north -trending diabase dike is mapped in Figure 6-1. Whether it affects
groundwater flow and contaminant transport at the site should be evaluated and
whether additional assessment is needed to determine whether there is any effect
should be also discussed.
d. 6.3. "A groundwater divide is located approximately along Pine Hall Road and to the
west of the ash basin along Middleton Loop Road." Data used to conclude this and
whether there is any uncertainty in its position and, if so, whether the uncertainty is an
issue for modeling particle tracks or transport should be discussed. Please note that the
uncertainty does exist because it is clear in the northwest area, groundwater has
crossed Middleton Loop Road and flows northwest from the ash basin.
e. 6.4
• "Applying this equation to wells installed during the CSA activities yields the
following average horizontal hydraulic gradients (measured in feet/foot):
Shallow wells: 0.009 ft/ft
Deep wells: 0.010 ft/ft
Bedrock wells: 0.019 ft/ft
Generally horizontal gradients in the ash basin range from 0.002 to 0.004 ft/ft.
Horizontal gradients outside the waste boundary range from 0.006 to 0.035
ft/ft. The hydraulic gradient south of the ash basin (GWA-12BR to MW-202BR)
and northwest of the dam (GWA-16S to GWA-11S) is likely due to the much
higher relief between the basin and downgradient areas." Generally,
groundwater table is parallel to ground surface; however, the average
horizontal hydraulic gradient in shallow wells appears to be much smaller than
the surface slope, which needs to be reevaluated. In addition, these results
need to be related back to contaminant transport and specific areas of interest.
Moreover, what is more important than a generalized "average" gradient across
all shallow wells, for example, the gradient across the shallow wells in
northwest and north of the dam or other specific areas of interest (i.e. along
specific, "hot" flow paths) should be evaluated. The findings should continually
7

f. 6.5
g. 6.6
relate back to contamination and its specific movement. The variations should
be shown on a map with the transects that were used to compute these.
• "Applying this calculation to wells installed during the CSA activities yields the
following average vertical hydraulic gradients (measured in feet/foot):
Shallow to Deep wells: 0.0195 ft/ft
Deep to Bedrock wells: 0.0967 ft/ft
Based on review of the results, vertical gradients were mixed across the site but
with more locations showing downward gradient values. More upward values
were noted south of the ash basin and the topographic high of Pine Hall Road
near Belews Reservoir (GWA-12, GWA-23, and BG-3 locations), downgradient of
the basin near the Dan River (GWA-30 and GWA-31) and northeast of the basin
(BG-2)." It is easy to understand upward values measured downgradient of the
ash basin near the Dan River or in discharge areas. However, what resulted in
upward values measured in these upgradient wells, for example, at the
topographic high of Pine Hall Road near Belews Reservoir and northeast of the
basin should be discussed. In addition, this should be to related back to
contaminant transport and specific areas of interest as well. Whether these
findings bolster or undercut the conceptual model and whether the vertical
gradients in some locations are contrary to what is expected, for example,
upward potential vertical gradients were measured at BG-2 and BG-3 (Table 6-
14) should be discussed. As these two background well -clusters were thought
to be drilled in upgradient, an explanation should be given to help understand
the case. What the recharge source is, if not the ash basin, for each of these
two areas need to be discussed.
• Results of pumping tests conducted for Basis of Design (BOD) report should be
integrated into this section to estimate hydraulic conductivity for the area. (The
BOD report was provided by Duke Energy to satisfy a requirement set in the
Settlement Agreement between DEQ and Duke Energy signed on September 29,
2015, which requires accelerated remediation to be implemented at sites that
demonstrate off -site groundwater impacts.)
• "Hydraulic conductivity values for wells screened in saprolite have a geometric
mean of 2.65 x 10-4 cm/sec. Hydraulic conductivity values for wells screened in
the transition zone have a geometric mean of 7.91 x 10-5 cm/sec. These
measurements reflect the dynamic nature of the transition zone, where
hydrologic properties can be heavily influenced by the formation of clays and
other weathering by-products." It is true that hydraulic conductivity can be
heavily influenced by clay content of the formation because clay content will
lower hydraulic conductivity, therefore, please provide evidence showing the
transition zone has higher clay content and other weathering by-product than
the shallow aquifer at this site as hydraulic conductivity is lower in the transition
zone than in the shallow aquifer, which is normally not the case.
W

h. 6.7
• "Average groundwater seepage velocity results are summarized in Table 6-13"
Please note that most of values, as computed, are not even necessarily along
flow paths (E.g. GWA-16S to GWA-11S). In such cases, the values are
completely erroneous. Also, why is the table divided into multiple columns for
ash, fill, M1, M2 for a single flow path and single flow unit? Is one value (M1,
e.g.) more representative than another for a given flow unit? Seepage velocities
need to be computed across specific areas of interest (e.g. along "hot" flow
paths). In addition, as indicated in the table, horizontal groundwater velocity is
greater in transition zone (TZ) than that in shallow zones M1 or M2. However,
hydraulic conductivity discussed above (6.5) is lower in transition zone than in
shallow aquifer. Please check whether there is anything wrong.
• "... Primary (matrix) porosity is negligible". Please provide rationale and
references for this statement.
• "Bedrock fractures encountered at BC55 tend to be isolated with low
interconnectivity." Please show the data and how this was determined.
• "Groundwater flow in bedrock fractures is anisotropic and difficult to predict,
and velocities change as groundwater moves between fractures of varying
orientations, gradients, pressure, and size. For these reasons, bedrock
groundwater velocities calculated using the seepage velocity equation are not
representative of actual site conditions and were not calculated." It is true, but
combining with aquifer testing results conducted in the northwest area for the
Interim Action Plan, bedrock groundwater velocity should be calculated, at
least, for that area.
• "Constituents like cobalt and thallium have much higher Kd values, and will
move at a much slower velocity than groundwater as it sorbs onto surrounding
soil." Moving velocities of constituents like cobalt and thallium also depend on
other geochemical conditions, such as pH and Eh, which should also be
discussed.
• "Continued vertical migration of groundwater is also evidenced by detected
constituent concentrations..." Please show data and wells, and discuss
implications.
• "It should be noted that the fractured bedrock flow system is highly
heterogeneous in nature and high permeability zones with a geomean in situ
horizontal conductivity of 0.00003 cm/sec observed, but these hydraulic.... etc...."
Why a "geomean" rather than simple mean or median was chosen to use needs
to be discussed.
6.9.2. "Relatively fewer northwest -trending lineaments, and more north -trending
lineaments (both being subparallel to regional diabase dike orientations) were identified
on aerial photography. Few west-northwest trending lineaments were identified, and
northeast trending lineaments identified on aerial photography are oriented primarily
N25E..... etc." Please discuss the implications for groundwater flow and contaminant
transport in specific areas of interest. The discussion should focus on "hot" flow paths
and explain how any observed lineaments affect the flow, transport, and risk.
0

j. Cross -sections should show lithology described in the boring logs as cross -sections
provided in CSA Supplement 2 report.
k. Additional cross -sections should be added: one from GWA-8 to GWA-19 as boron plume
expands to NW and another one perpendicular to Cross -Section A -A', from east to west
through the main dam of the ash basin because of transect B-B' is not perpendicular to
A -A' .
I. To determine groundwater flow directions better, all available monitoring wells
(voluntary, compliance, and groundwater assessment monitoring wells) in all three flow
units must be measured for water level in a single sampling event once and Figures 6-6
through 6-11 should be revised with the measurements.
m. For Table 6-12, please explain why the water level was not measured for each
groundwater elevation field filled with three dashes
n. Table 6-13, horizontal gradients to NE-E from the ash basin should be also
evaluated/determined and listed in this Table.
o. Please provide a map showing where (wells) aquifer tests, including slug tests, were
conducted and testing results.
6. Section 7
a. Figure 7-1 should also show and highlight soil concentrations exceeding PBTVs that
exceed POG PSRGS in unsaturated zone. In addition, a plane view map showing
horizontal extent and cross -sections showing vertical extent of contaminated soil should
be provided.
b. If contaminated soil were detected beyond the waste boundary, what is the source and
how the contaminants were transported away from the sources should be discussed.
c. 7.1. Soil contamination cleanup level should be either the site- PBTVs or POG PSRGS
levels, whichever are higher. Therefore, POG PSRG values for chloride, sulfate, and
vanadium should be calculated using the calculation in the PSRG table as these values
have not be established. Calculated values should be also shown on Table 7-2.
d. 7.2
• "Soil sample test results indicate shallow impacts to the soil beneath the ash
basin." To what depth the impacts have reached and estimated volume with
concentrations exceeding PBTVs should be discussed and estimated.
• "Concentrations of boron from wells beyond the compliance boundary did not
exceed PSRG values and only two locations exceeded the PBTV at GWA-6S and
MW-200BR. The majority of exceedances are sporadic and do not indicate the
ash basin as a source of soil impacts beyond the waste boundary." Please
provide the basis for this statement and explain as the ash basin is not the
source, what will be the source.
• "Elevated concentrations of chromium, iron, strontium and vanadium in areas
upgradient of the ash basin (GWA-6S, GWA-7S and GWA-8D) are not influenced
by the ash basin and associated with natural soil geochemistry. Saturation and
other factors may also affect constituent occurrence in the samples." This
statement needs to be supported by data and more detailed discussion. Please
note that boron was detected in GWA-8S.
10

7. Section 8
a. This section is more a data summary. At least, what these data mean to water quality
and to human health and the environment and whether additional assessment or any
corrective action will be needed should be discussed.
b. 8.1. Whether additional assessments are needed at S-6, 5-10, 5-11, BCSW-007, BCSW-
008, and BCSW-19 area should be discussed. It should also be discussed why for some
areas only arsenic or selenium was detected at concentrations exceeding the PBTVs and
whether additional assessments are needed.
8. Section 9
a. "For this CSA, it is pertinent that a comparison with NCDENR Title 15A, Subchapter 028.
Surface Water and Wetland Standards (28) standards includes only sample results from
named surface waters. AOWs, wastewater and wastewater conveyances (effluent
channels), and industrial storm water are evaluated and regulated in accordance with
the NPDES Program administered by NCDEQ DWR." Why are only "named" surface
waters? Are all AOWs or unnamed streams and wetlands located on or near the site are
considered effluent channels? If not, then they will be jurisdictional waters, which
should be evaluated with 2B standard. Please also note that some of AOWs are
identified as effluent channels in the anticipated permit which has not been issued.
b. "Sample SW-DR-U has had contaminant concentrations reported as being greater than
the background surface water sample (and reported 28 surface water standard
exceedances), which suggests that there may be influence from the ash basin at this
location along the Dan River. However, contaminant concentrations detected in SW-DR-
U were similar to those in sample 003, collected at the ash basin discharge structure
flume in the designated effluent channel, indicating that the location of sample SW-DR-U
may be too close to the designated effluent channel to reflect actual water quality in the
Dan River." Please provide the data (sampling results, such as boron, chloride, TDS, etc,
from SW-DR-U and Outfall 003) and indicate the distance (in feet) of the location from
the Outfall.
c. Please state whether the additional surface water samples recently collected from the
Dan River were collected in accordance with DEQ Internal Technical Guidance:
Evaluating Impacts to Surface Water from Discharging Groundwater Plumes. Whether
samples were collected at base flow conditions should be also documented.
d. Additional assessment (for impacts of groundwater discharge on Belews Reservoir) as
proposed on the map submitted through October 4, 2017 email is needed to complete
the CSA.
e. 9.1
• "Analytical results with the dissolved phase concentrations greater than their
associated total reportable concentrations are not included in the assessment as
they are considered invalid." What caused the problem should be discussed and
whether it is necessary to resample should be discussed.
• "Sample results from the Dan River indicate that field parameters (turbidity, pH,
and DO), total concentrations of chloride, selenium, and TDS, dissolved
concentrations (cadmium and lead) have been reported as being greater than 28
11

values on one or two occasions, but not consistently." Need to state
implications for 2L-2B conclusions.
9. Section 10
a. 10.1. BG-2D was missed but should also be listed in NCDEQ approved background well
list.
b. 10.2
• Please discuss whether all monitoring wells are positioned properly (horizontally
and vertically) and a certain number of wells are installed along "hot" flow path.
• The maximum, the average concentrations of each of COls, estimated mass of
contaminants, and the volume of contaminated water should be summarized in
a table.
• "... The second quarter 2017 data is the primary dataset used for generating
isoconcentration maps and graphical representation of data such as Piper
diagrams." What other data were used should be given in order for DEQ to
evaluate those maps or figures.
• Each COI Isoconcentration map was well descripted, but how the site
geochemical conditions control the particular distribution was almost not
interpreted.
• For groundwater Isoconcentration maps, dash line should be used after contour
lines cross the waste boundary of Pine Hall Road Landfill and the ash basin from
outside of the waste boundary because of lack monitoring wells in the middle of
the landfill or the basin where is filled with water or saturated ash.
• For Figures 10-17 and 10-18, as the Structure Fill is the potential source for
contaminants detected at GWA-8S and GWA-23S/D, isoconcentration line 700
µg/L should not be closed on the Structure Fill side.
• Figures 10-17 and 10-18, isoconcentration 700 µg/L contour line between GWA-
11S and GWA-1S in the shallow zone and near AB-1D in the deep zone do not
appear to be plotted properly. Why the lines sharply curve toward the basin?
• Although as shown on Figures 10-5 to 10-64, the extent of groundwater
migration from the ash basin at concentrations greater than background and 2L
extend downgradient of the ash basin do not appear to reach the Dan River,
whether 11,200 µg/L of boron at GSA-20SA (Fig. 10-17) would drop to 852 µg/L
at GWA-11S, and 184 µg/L at GWA-21S through dilution alone should be
discussed. Whether the well positions or screened intervals are measuring the
flow path away from the hot spot should be discussed.
• Please note that several constituents are above 2L in the area north of the ash
basin, beyond compliance boundary, such as Be (shallow and deep), Cr (shallow
and deep), Co (shallow), Fe (deep), Mn (shallow, deep, and BR), and TI (shallow
and deep), but it is unclear why, since boron migration seemed to be limited to
the area right around the compliance wells. How site geochemical conditions
resulted in or control these occurrences should be discussed in the report.
• High boron concentrations were detected in deep wells (e. g., 9890 µg/L at
GWA-20D and 5420 µg/L at GWA-27D), but no 2L exceedances were measured
12

c. 10.3
d. 10.4
in their paired bedrock wells. Whether these results are supported by site
hydrogeologic conditions and/or groundwater hydraulic property, such as
vertical hydraulic gradient and conductivity, should be discussed.
• "Monitoring wells GWA-19BR, GWA-20BR, and GWA-27BR are located
northwest of the ash basin. These wells are grout contaminated (high pH) and
their data is not considered valid. The boron concentrations reported in these
monitoring wells are similar to the boron background concentration." As pH may
affect the concentration of COls and the data is not considered valid, whether
these wells (especially GWA-2713R, a downgradient leading -edge bedrock well)
need to be replaced or whether additional bedrock wells are needed should be
discussed. Please also state boron concentrations of the background and these
wells to support the statement.
• For monitoring wells that were not sampled in April 2017 sampling event, the
most recent sampling result or the historical average should be used in
construction of these isoconcentration maps. For example, Figure 10-19, none
of bedrock wells in the northwestern area was sampled, which makes for a very
limited snapshot of CCR movement in the bedrock unit. If the data from those
bedrock wells cannot be justified due to high pH values and it is necessary to
replace the wells, please provide a proposal for replacement of wells as soon as
possible.
• It seems that GWA-24S has never been sampled. It is time to evaluate whether
the well should be replaced.
• To determine whether GWA-8S is soured by the ash basin or the Structural Fill,
additional well(s) appears to be needed if no data from DMW can be used.
• Results from SFMW-2D, SFMW-1D (and paired shallow and bedrock wells) from
assessing Structure Fill should be provided. The data will help to evaluate the
source of boron measured in GWA-8 and GWA-23.
• Please explain why BG-1S is considered a downgradient well on shallow
groundwater Isoconcentration maps. If it is an error, please correct it.
• Please list or indicate COls exceeding PBTVs that exceed 2L/IMACs in Table 10-3
or a new table. The table should also show cleanup levels that are either PBTVs
or 2L/IMACs, whichever is higher.
• Table 10-3 lists all COls developed for the site. As not all of COls exist in all
three flow zones, please also list them for each flow zone or unit.
• Please list COls found in water supply wells, which exceed PBTVs or 2L/IMACs,
whichever is higher.
• Each of water supply wells containing constituents exceeding 2L/IMACs or
PBTVs, whichever is higher, should be evaluated as potential receptors based on
actual data, piper -diagram, co-occurring constituents, proximity to CCRs, and
topographic setting. Conclusions must be drawn. Only in this way can potential
supply well impacts be ruled out and a CAP be properly developed.
13

10. Section 11
a. 11.1
• "Monitoring wells installed for other regulatory programs have added additional
details about the orientation and extent of the downgradient plume and have
helped refine an understanding of the distribution of the plume." Does this
mean or include CCR wells? Please specify the programs.
• "The boron concentration is non -detect in monitoring wells GWA-30S and GWA-
31S which define the leading edge of the boron plume in the shallow flow layer.
West of the ash basin the boron concentrations are non -detect or less than the
PBTV at the compliance boundary." Please note that as discussed earlier, in the
area to the west of GWA-195, boron has not been delineated. The last sample
(4/4/2017) detected boron at 2110 µg/L, but no well is located west of this
point.
• "Figures 11-1 through 11-3 depict concentration versus distance from the source
along the plume centerline for COls." Interpretations of what these figures
mean/say should be included.
• "Cross-section B-B' is a transect perpendicular to the plume centerline." This
transect does not appear to be perpendicular to the plume centerline or Cross-
section A -A'. As higher concentrations were detected at the base of and along
the dam, a cross-section along the base of the dam, from GWA-31 to GWA-22
should be added. In addition, please evaluate as contaminants are also moving
to northwest, whether another cross-section from GWA-7 through the source to
GWA-31 should be added.
• "The well screens in the CAMA wells accurately monitor groundwater conditions
and impact to the shallow and deep flow layers." Please explain on what basis
this statement was made.
• "Likewise, as it has been demonstrated with the installation of deeper bedrock
well AB-4BRD beneath the ash basin (AB-9BRD is grout contaminated and the
data is not usable), impact to the bedrock flow unit is confined to the top
approximately 100-140 feet of fractured bedrock." Please provide corroborating
data, such as depth to water of the well and sampling results from the well.
• "Groundwater elevations are not available to calculate vertical gradients in the
well clusters installed near and along the base of the dam." Please explain why
and evaluate whether additional wells are needed. Currently there are two well
clusters: MW-200S/D/BR and GWA-24S/D/BR, but GWA-24S has been always
d ry.
• "A downward gradient exists to the east and west of the designated effluent
channel downgradient of the dam." Please provide well IDs and their head
values and explain what this implies for groundwater flow and transport.
• "As groundwater and the plume migrate in the downgradient direction,
unimpacted groundwater enters the system from upgradient recharge areas to
the west and east, mitigating the concentration of some COls (e.g., boron)."
Please provide evidence and data to support this statement.
14

• "Further, it can be concluded that monitoring wells across the site are
appropriately placed and screened to the correct elevations to monitor
groundwater quality." On what basis? Please support this statement with
rationale/data.
• Boron concentration has been increasing in a significant number of wells,
including plume downgradient leading edge wells, such as GWA-IS, GWA-
21S/D, GWA-195, MW-103S/D, and MW-200S/BR, and wells, MW-4, OB-9, and
MW2-7, at Pine Hall Road Landfill. Whether these increases indicate the plumes
still expanding should be discussed thoroughly. In addition, boron
concentration in GWA-8S is increasing, but this well is considered an upgradient
well for ash basin, which indicates the Structure Fill being the source. As
commented for Section 10, additional well(s) between GWA-8S and the
Structure Fill is needed to confirm this.
• Figure 11-37, the footnote indicates that PBTV for deep flow layer is 55 ug/L,
while Table 10-2 indicates 13 ug/L which is approved by DEQ.
b. 11.2. "Plume chemical characterization is detailed below for each COI..." This
subsection is good information as a very broad, site wide overview and summary, less
site specific except concentrations, but should be further discussed for CAP
development for specific areas of concern. For instance, "Despite the low apparent
mobilization percentage, manganese can be detected in relatively high concentrations in
ash pore water." Why and what this mean regarding site remediation should be
explained.
c. 11.3
• "Additional metal oxy-hydroxide phases of iron (HFO) and aluminum (HAO) data
are needed to support geochemical modeling conducted as part of the CAP. Soil
and rock samples will be collected from previously installed borings or from
additionally drilled boreholes along the primary groundwater flow transects..."
Based on the data presented in this report, DEQ agrees to collect additional
metal oxy-hydroxide phases of iron (HFO) and aluminum (HAO) data as
proposed in this section to refine geochemical modeling conducted as part of
the CAP, particularly in downgradient locations northwest of the ash basin.
Please provide a map and cross section showing both existing and proposed
sample locations and depths.
• "To help determine potential routes of exposure and receptors related to the ash
management areas, additional surface water samples will be collected from
Belews Reservoir and the Dan River near the stream/river bank most likely to be
impacted by potentially contaminated groundwater discharge..." Until this
pending assessment is done, the CSA is still incomplete. Please provide this
office a proposed schedule if the proposed samples have not been collected;
otherwise, please submit the sampling results as soon as possible.
11. Section 12
a. "As previously noted, AOW locations are outside the scope of this risk assessment
because AOWs, wastewater, and wastewater conveyances (effluent channels) are
15

permitted under the NPDES Program administered by NCDEQ DWR." AOW locations
that are not considered effluent channels should be assessed and discussed.
b. "New maximum concentrations of antimony, arsenic, beryllium, hexavalent chromium,
nickel, and selenium were detected that exceeded human health risk screening values;
however, no values exceeded respective site -specific RBCs. There is no evidence these
constituents pose human health risks from groundwater exposure." Please provide
summary tables comparing new maximum concentrations of constituents of potential
concern (COPCs) to the site -specific human health risk -based concentrations (RBCs) for
human health and ecological receptors.
c. "The sample location SW-DR-D is adjacent to NPDES outfall 003 discharging ash sluice
and FGD wastewater and is not representative of Dan River conditions downstream of
plant operations." "NPDES outfall 003 discharging ash sluice and FGD wastewater"
should be revised as "NPDES outfall 003 discharging wastewater from the ash basin
which ash sluice and FGD wastewater discharge to".
d. The ecological risk assessment reported in CAP 2 report indicated that risk estimates for
several COPCs are above risk targets for some water dependent mammals and birds, if
and where these species are present at the BCSS site. However, only cobalt was
evaluated in this report. Each of COPCs identified in CAP 2 report above risk targets
should be discussed in this report.
e. A table summarizing surface water quality sampling results and showing LOAEL, ADD,
TRV should be given in this section as LOAEL, ADD, and TRV are used to evaluate
whether surface waters risk the ecological receptors.
f. To evaluate whether coal ash has impacted or has any potential risk for any water
supply wells and whether the well water has any risk for human consumption, in
addition to 2L/IMAC and DHHS screening levels, EPA MCL and tap water Regional
Screening Levels (RSL) were also used. Therefore, to support the statement and
conclusion, DHHS screening levels, MCL, and RSL should be added into Table 4-3 and
referred in this section, or provide a concise table including these referenced levels in
this section.
g. 'Based on review and analysis of groundwater and surface water data, there is no
evidence of risks to humans and wildlife at BCSS attributed to CCR constituent migration
in groundwater from the ash basins. This update to the human health and ecological risk
assessment supports a proposed NCDEQ Risk Classification of 'Low"." As commented
earlier, site risk classification should be classified in accordance with CAMA and also
depends on the potential risk that depends on how the ash basin is closed and how the
contaminated soil and groundwater are addressed. Updated groundwater fate and
transport modeling results to be presented in the CAP will help as well.
12. Section 13
a. All COls should be modeled unless rationales are given.
b. If a PBTV for a constituent is higher than 2L/IMAC, whether the constituent
concentration exceeds the PBTV at the compliance boundary or receptors should be
also modeled.
16

c. Whether a GW/SW mixing model should be updated and included in the CAP should be
discussed in this report.
d. Because the summary is too general and the models are still being updated, our review
cannot be completed until updated modeling reports are received.
e. It should be discussed in the updated flow modeling report that whether the
uncertainty in model parameters and predictions can be quantified, and therefore, the
error in model predictions can be evaluated.
f. 13.3. "Based on the available data for the upstream and downstream Belews Reservoir
samples and the known COI distribution in groundwater the BCSS ash basin is not the
source of 2B exceedances in Belews Reservoir." This statement is not conclusive. Please
note that SW-BL-D is too far from the bank to assess 2L/2B violations. In addition, the
seep sample location, S-6 near Belews Reservoir, was consistently detected boron above
2L. To determine whether there is any 2B exceedances in Belews Reservoir and
whether the ash basin is the source, additional sampling is needed.
13. Section 14
a. "The ash basin pore water was determined to be a source of impact to groundwater."
This statement not is not quite right, but should be consistent with Section 3. Section 3
indicated: "For the BCSS site, sources include the ash basin, Pine Hall Road Landfill, and
the former chemical pond."
b. "Some COIs, such as boron, readily solubilize and migrate with minimal retention. In
contrast, some COls such as arsenic readily adsorb to aquifer materials, do not readily
solubilize, and thus are relatively immobile." As summarize assessment results, all COls
that are readily mobile and all COls are relatively immobile should be listed rather than
boron and arsenic only.
c. "Boron is also detected in the bedrock flow layer at monitoring well OB-9, located
north/northwest of the Pine Hall Road Landfill at a concentration greater than the PBTV
and less than the 2L standard." Based on the information provided in Section 6, OB-9 is
a deep well and the concentration of boron from this well is greater than 2L. Please
check and correct statement as necessary.
d. 'Boron results exceed the 2L standard beneath the Pine Hall Road Landfill in the deep
flow layer, but are non -detect at the compliance boundary." This statement may not be
true in downgradient or to the north where the plume migrated outside of the CB and
comingled to the plume caused from the ash basin.
e. Legends of Figures 14-97 to 14-99 indicate: "Wetland and stream boundaries provided
by AMEC Foster Wheeler. Note these do not appear to be inclusive of all the boundaries
as shown in the AMEC Forster Wheeler NRTR Belews Creek Report." This sounds like
that these figures do not include all surface water bodies. Please check it further to see
whether this is what the statement means. If yes, all related figures need to be revised
to include all jurisdictional waters.
f. "The bedrock aquifer is generally the source of water for supply wells in the area. As
outlined above, the bedrock aquifer has not been impacted by CCR constituent migration
from the ash basin with the exception of a grout contaminated well beneath the ash
17

basin main dam." As bedrock wells were contaminated with well grout material,
whether additional wells or assessment is needed should be discussed.
g. The leading edge of the boron plume in the shallow flow zone in NW of the ash
basin, GWA-19S area, has not been delineated and should be addressed before
moving to the CAP.
h. From Figure 14-98, it looks like that S-2-D, S-3-D, and S-5-D were collected from the Dan
River; however, the results are not listed in Table 2, Surface Water Results, of Appendix
B, but in Table 3, AOW and WW Results. If they were not collected from the Dan River,
please correct the figure; otherwise, list them in Table 2, Surface Water Results.
i. As indicated earlier (comment on Section 11), concentrations of some of COls, including
boron in some downgradient wells, such as GWA-19S, are still increasing. The number
of wells in which concentrations of Ba, B, Cd, Cl, and Sr were increasing is more than the
number of wells in which the concentrations were decreasing. Whether plumes are still
expanding needs to be evaluated and conclusions need to be made.
14. Section 15
a. 15.1. "The horizontal and vertical extent of exceedances has been defined (Figure ES-1)
sufficiently for preparation of the CAP." Please note that no vertical extent shown on
Figure ES-1. What the text says should be consistent with what the figure shows.
Furthermore, additional delineation west of GWA-19SA appears to be needed.
b. 15.2
c. 15.4
• "Assessment findings determined that pore water in the ash basin is the primary
source of impact to groundwater. As previously discussed, residual
concentrations of arsenic, selenium and strontium in soil beneath the ash basin
may also represent a secondary source." Does this statement mean that the CCR
or coal ash that is the source of pore water is not the source of groundwater
contamination? The CCR should be the source as discussed earlier. Please
clarify.
• "These topographic divides generally function as groundwater divides, although
groundwater flow across topographic divides may be possible based on
hydraulic head conditions from the ash basin and the existence of preferential
flow paths within the shallow and/or deep flow layers." Based on the
occurrence groundwater plumes, such as boron, this statement should be
revised because the plume has crossed (not "may be possible") Middleton Loop
Road, a topographic divide.
• "... As outlined above, the bedrock aquifer has not been impacted by CCR
constituent migration from the ash basin." Again, this statement is inconclusive
because no wells including bedrock wells were installed in the middle of the ash
basin due to safety concern. In addition, GWA-27BR is grout contaminated and
pH is consistently high. Although no boron was not detected but data is
considered invalid. Therefore, the vertical extent in this area may have not be
properly determined, which need to be discussed.
18

d. 15.4
• "Constituent concentrations in bedrock groundwater directly downgradient of
the ash basin are less than 2L with the exception of manganese, which appears
to be due to geochemical conditions." Although it has been mentioned several
times in the report that manganese concentrations reported in bedrock
groundwater are likely due to natural geochemical conditions, what
geochemical conditions and how the conditions affect the distribution of
manganese were not discussed but is expected.
• "Monitoring wells GWA-19BR, GWA-20BR, and GWA-27BR are located
northwest of the ash basin. These wells are grout contaminated (high pH) and
their data is not considered valid. The boron concentrations reported in these
monitoring wells are similar to the boron background concentration." This
statement is simply from Section 10, which is neither a conclusion nor a
recommendation. As commented earlier, since pH has been consistently high in
GWA-27BR, whether the well should be replaced to further delineate the
vertical extent in this area should be discussed.
• "It is assumed a source control measure of either capping the ash basin and
minimizing infiltration, or excavation, or a combination of the two, will be
designed following completion of the risk classification process." At this phase,
the risk classification process should be completed. As it has not been done,
please make a clear recommendation or plan for completion.
• Comments on "The following Site conditions significantly limit the effectiveness
of a number of possible technologies."
1. "The area that may require groundwater remediation is between the toe
of the basin dam and the compliance boundary to the north." Please
specify the limitations this condition will propose for remediation. In
addition, this area should be one of the areas..., not the area.
2. "The COls that may potentially need to be addressed are predominantly
found in the downgradient bedrock formations." Does this mean
bedrock aquifer? If yes, this statement does not appear to be
consistent with isoconcentration maps and cross -sections. For instance,
boron has not been detected at concentration above 2L standard in any
bedrock wells so far. Please list COls, bedrock wells, and concentrations
to support this statement.
3. "Groundwater flow is primarily through the upper fractured bedrock unit
and...." There are three flow units. Groundwater hydraulic data and
plume information from this report does not support this statement.
For instance, boron migrated farther in shallow unit than in other two
units.
• Groundwater extraction combine with source control and MNA is to be
proposed in the updated CAP, which appears to be reasonable. Real challenge
is probably source control. Details are expected in the CAP.
19

CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC - Belews Creek Steam Station SynTerra
1.0 OVERVIEW OF CSA UPDATE REPORT DEFICIENCIES
Overview of CSA Update Report Deficiencies Comment 1
The report contents are presented in a data summary format, exhibiting a lack of conclusive data
analysis and interpretation of site conditions.
Response Summary 1
The report contents are presented in data summary format to clearly provide the
facts regarding site characterization. Duke Energy disagrees with the comment that
data analysis conclusions and interpretation of site conditions were not provided.
However, a more thorough discussion regarding site conditions and conclusions are
provided in the CAP Update report supported with tables, figures and modeling
results as specified in the CAP Content Guidance (April 27, 2018 and September 10,
2019 NCDEQ letters).
Overview of CSA Update Report Deficiencies Comment 2
The report fails to fully integrate and evaluate data collected from previous versions of the CSA
reports for the facility.
Response Summary 2
As indicated above, all historical and current CSA data (as of report issuance) was
provided in tabular and pictorial form for succinct definition of site conditions.
Previous CSA and CAP submittals provided detailed information that was not
deemed necessary for repetitiveness in the CSA Update report, however, the CAP
Update report incorporates pertinent information from the previous reports to fully
address site conditions for corrective action.
Overview of CSA Update Report Deficiencies I Comment 3
The distribution of constituents of interest related to coal ash sources presented in the report
often fail, for at least some areas of the site, to fully and clearly acknowledge and delineate
exceedances of the 15A NCAC 2L or 2B standards above background levels.
Response Summary 3
Deficiencies regarding 2L exceedances are better defined/delineated in the CAP
Update report. Additional sampling to assess groundwater (02L) to surface water
(02B) interaction has been conducted and provided in Appendix K of the CAP
Update report.
Overview of CSA Update Report Deficiencies Comment 4
The characterization of other primary and secondary sources other than impoundments that
contribute to the groundwater plumes is inadequate, particularly near the chemical pond.
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
Response Summary 4
An overview of primary and secondary sources, the Pine Hall Road Landfill, along
with NCDEQ consensus, is presented in Section 3.0 of the CAP Update report.
Overview of CSA Update Report Deficiencies Comment 5
As detailed more fully in the attached document, additional data gaps remain concerning
delineation of impacts from coal ash at the facility.
Response Summary 5
Noted. Additional data gaps as presented in the site specific CSA comments are
addressed in the CAP Update report with appropriate references within the
document.
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
2.0 CSA UPDATE REPORT FORMAL COMMENTS AND RESPONSES
DEQ Formal Comment 1
The plume morphology of some constituents (beryllium, boron, and selenium in the shallow
zone, iron and vanadium in the deep zone, and thallium in both the shallow and deep zones) are
irregular and exhibit variable ranges of concentrations in the northwestern area, which implies
complex hydrogeological and geochemical conditions exist at this portion of the site. This
complexity with respect to contaminant distribution suggests that more appropriately located
downgradient well(s) are necessary to confirm site conditions although coal combustion
residuals (CCR) data does show that boron in GWA-19 is sourced by the ash basin. For the same
reason, it appears necessary to install a well(s) downgradient from GWA-21S to further
delineate beryllium and thallium plumes. If groundwater flow and fate/transport models do not
indicate that the plumes will be migrating off the property or causing any 02B violations, the
installation of the additional wells further downgradient may not be urgent or may not have to
be done before the CAP, but will have to eventually be installed for performance monitoring.
Response Summary 1
To address further delineation of COI plumes downgradient of the GWA-21S
cluster, an additional well cluster, CCR-13S/D/BR, was installed approximate to the
S-4 AOW location in October 2018 (see Figure 1-2, CAP Update report). The
installation activities are documented in the 2018 Annual Report submitted April 30,
2018. As described in the CAP Update Report Section 6.2.2.1 Groundwater COI
Extent, and presented in Figure 6-11a through Figure 6-21b, the extent of the
constituents mentioned above has been well defined (horizontally and vertically)
with the inclusion of assessment data from the CCR-13S/D/BR well cluster.
Constituent behavior related to plume movement and potential 02B impacts are
further described in transport modeling along with geochemical modeling that
incorporates this area of concern as presented in Appendix G (Flow and Transport
Model Report), Appendix H (Geochemical Model Report) and Appendix K (Surface
Water Evaluation Report) of the CAP Update report.
DEQ Formal Comment 2
High levels of boron have been consistently measured in MW-2-7 (22,700 µg/L, April 11, 2017)
at Pine Hall Landfill. To determine the vertical extent, at least one additional bedrock well
appears to be needed. This was not requested earlier because the data from the North Carolina
Department of Environmental Quality (DEQ), Division of Waste Management (DWM) was
expected as this part assessment. If no additional deep or bedrock well data from DWM can be
provided, at least one deep or bedrock well is needed.
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
Response Summary 2
It is Duke Energy's position that vertical assessment wells (bedrock) are not
necessary with respect to hydrogeologic gradient (to the north) and
analytical/hydrogeological data from the downgradient existing well cluster AB-
4S/SL/SAP/D/BR/BRD demonstrating vertical assessment control in that area. As
described in Section 6.1.2 Chemistry within the Waste Boundary and presented in
Figure 6-6a (General Cross -Section A -A', Ash Basin Conservative Group), bedrock
underlying the ash basin is not impacted by the overlying ash materials with the
exception of a downward vertical gradient present at the dam due to the hydraulic
head of the ponded water. The layered ash within the basin has resulted in
relatively low vertical hydraulic conductivity, further reducing the potential for
downward flow of pore water into underlying residual material. As described in
Section 6.2.2 COI Migration at or Beyond Compliance Boundary, the bedrock
hydraulic conductivity at the Site and calculated fracture apertures decrease with
increasing depth below the top of rock (Appendix F, Deep Bedrock Evaluation
Report). Based on the orientations of lineaments and open bedrock fractures,
horizontal groundwater flow within the bedrock should occur approximately
parallel to the hydraulic gradient, with no preferential flow direction (i.e., no
expected, significant anisotropy). The MW-2-7 well is within the review/compliance
boundary under DWM regulatory jurisdiction.
DEQ Formal Comment 3
In addition, boron was detected in CCR-6D at a concentration as high as 12,400 µgIL, which
also indicates that the vertical extent should be further delineated. A paired bedrock well nest
should be installed.
Response Summary 3
Additional vertical assessment wells in the bedrock were installed at the crest of the
ash basin dam based on revised groundwater flow and transport modeling for the
CAP. Duke Energy complete the additional installation of wells voluntarily.
The deep bedrock wells were paired with existing well clusters AB-1, AB-2 and AB-3
and include AB-1BR/BRD, AB-2BR/BRD and AB-3BR. Flow and transport (F&T)
modeling demonstrates the greatest downward vertical gradient of COI migration
will occur at the dam owing to hydraulic head differences created by the dam. CCR-
6D is located near the toe of the dam, where F&T modeling demonstrates an upper
vertical gradient supported with artesian effects in bedrock demonstrated in MW-
200BR. Additional discussion regarding COI distribution related to groundwater
migration in the vicinity of the dam is provided in Section 6.2.2 COI Migration at, or
Beyond Compliance Boundary and presented on Figure 6-6a (General Cross -Section
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
A -A', Ash Basin Conservative Group). The installation and sampling activities for
the deep bedrock wells installed within the dam structure is provided in the
Bedrock Evaluation Report (Appendix F).
DEQ Formal Comment 4
With regards to porewater analysis, interpretations of site conditions that include analytical
results from specific sample locations (well IDs) are needed to justify the broad statement
regarding the decrease in concentrations. As the ash basin is an active basin, the cause for
decreasing concentrations in porewater should be evaluated, including implications for
constituent of interest (COI) concentration distribution and mobility.
Response Summary 4
Ash pore water constituent concentration trends are discussed in Section 6.1.2
Chemistry within Waste Boundary. In ash pore water samples collected from wells
within the ash basin, arsenic, boron, chloride, iron, manganese, sulfate, and total
dissolved solids (TDS) have been reported at concentrations greater than the 02L
standards; cobalt, thallium, and vanadium have been reported at concentrations
greater than IMACs; and molybdenum and strontium have been reported at
concentrations greater than background threshold values (CAP Update Report,
Appendix C, Table 1).
Hydrographs and geochemical water quality parameter time series plots for one ash
pore water monitoring location and three downgradient groundwater monitoring
locations are included on Figure 6-7. In general ash pore water and groundwater
geochemical parameters appear stable under changing site conditions. Ash pore
water pH and ORP do not appear to be significantly affected by lowering the ash
basin pond's water level, and therefore represent stable conditions in which an
increase in constituent dissolution and mobility is unlikely to occur. Additionally,
groundwater pH and ORP, monitored beneath and downgradient of the ash basin,
are unaffected by even larger reductions in water levels, indicating stable
geochemical conditions in which constituent dissolution and mobility are unlikely to
occur.
DEQ Formal Comment 5
Provide an interpretation as to how the geochemical conditions affect or control the distribution
of COIs with site specific data (COI concentrations vs geochemical parameter levels, identified
with well IDs).
Response Summary 5
Each COI exhibits a unique geochemical behavior related to the specific constituent
Ka, response to changing geochemical parameters (i.e., pH and Ex), and sorption
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
capacity of the soil and/or rock matrix. Geochemical modeling indicates non -
conservative, reactive COIs (e.g., arsenic, beryllium, and thallium) will remain in
mineral phase assemblages that are stable under variable site conditions north of the
basin, demonstrating sorption as an effective attenuation mechanism (CAP Update
Appendix H). Geochemical modeling indicates variably reactive COIs (e.g., cobalt,
iron, and manganese) can exhibit mobility, depending on pore water geochemistry
and availability of sorption sites (CAP Update Appendix H). Non -reactive COIs
[e.g., boron, chloride, lithium, and total dissolved solids (TDS)] are relatively non -
reactive species under the range of Site -specific Ex and pH conditions (CAP Update
Appendix H). That is, these constituents would be expected to migrate in
groundwater as soluble species and are not strongly attenuated by reactions with
solids but are reduced in concentration with distance by physical processes such as
mechanical mixing (dispersion), dilution, and diffusion into less permeable zones.
Current conditions simulations from the groundwater flow and transport and
geochemical models predict constituent distribution and geochemical behavior
consistent with empirical Site data (CAP Update Appendix G and H).
COIs that are relatively mobile, such as boron, move largely attenuated through the
groundwater system under the prevailing hydraulic gradients (horizontal and
vertical) until discharged to a surface water body. As a result, boron tends to be the
constituent that is detectable at concentrations from background at the greatest
distance horizontally and vertically from the ash basin due to its low Ka value and
high mobility. Therefore, boron is considered the best indicator of the leading edge
of the plume. Unlike most of the other COIs that are detected in the ash pore water,
boron has a low affinity for sorbing to soil or bedrock solids under Site water
chemistry conditions. Using boron data, the horizontal flow -through system is
consistent with Site -specific data, supporting the CSM. COIs chloride, lithium, and
TDS also have low Ka values, but have horizontal and vertical distributions
generally within the footprint of and smaller than the boron plume, and are
localized to the ash basin waste boundary.
Other CCR-related constituents in the groundwater include arsenic, beryllium,
cobalt, iron, manganese, strontium, and thallium. The distribution of these other
COIs in groundwater are generally limited within the footprint of the boron plume.
The extent of migration along the prevailing flow paths of the other constituents is
controlled by the hydraulic properties of the system and by geochemical processes.
Under typical Ex and pH conditions, most of the COIs would not migrate
appreciably beyond the ash basin within the groundwater system and do not exhibit
discernable plumes. Predictive modeling has demonstrated that potential corrective
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
actions such as basin closure and groundwater extraction will not result in
geochemical changes substantial enough to significantly affect constituent mobility.
Further discussion of geochemical behavior and mobility of COIs is addressed in
Section 6.2.1 Constituent Management Approach and discussing in Section 6.2.2 COI
Migration at or Beyond Compliance Boundary supported with geochemical
modeling as provided in Section 4.0 of the Geochemical Modeling Report (CAP
Update Appendix H).
DEQ Formal Comment 6
Whether 11,200 µg/L of boron at GSA-20SA (Fig. 10-17) would drop to 852 µg/L at GWA-11S,
and 184 µg/L at GWA-21S through dilution alone should be discussed. Whether the well
positions or screened intervals of GWA-11S and GWA-21S are measuring the flow path away
from the hot spot should be discussed.
Response Summary 6
Based on site specific geochemical model simulations, the majority of boron is
expected to be conservatively transported and only attenuated by physical means
(see Section 4.4 Appendix H, Geochemical Modeling Report). Therefore, boron
migration is hydraulically driven and undergoes dilution effects with migration
away from the source. As depicted on the shallow water level map (Figure 5-4a),
monitoring wells GWA-11S and GWA-21S are downgradient from GWA-20SA.
With current understanding of site hydrogeology and the geochemical behavior of
boron, the decrease in concentration of boron with distance from the source is
expected. Wells GWA-11S and GWA-21S are downgradient of the ash basin.
Following site flow conditions defined in the F&T model (Appendix D), these
shallow monitoring wells measure constituent migration from the ash basin.
DEQ Formal Comment 7
High boron concentrations were detected in deep wells (e.g., 9,890 µg/L at GWA-20D and 5,420
µg/L at GWA-27D), but no 02L exceedances were measured in their paired bedrock wells.
Whether these results are supported by site hydrogeologic conditions, such as vertical hydraulic
gradient and conductivity, should be discussed.
Response Summary 7
The high concentrations detected in the deep wells and non -detections in the paired
bedrock wells are likely attributed to low connectivity between the transition zone
and fractured bedrock in this area. Lithological boring logs report few fracture
occurrences in bedrock northwest of the basin during drilling activities of GWA-
20D/BR and GWA-27D/BR. Well screens from GWA-20D and GWA-20BR are
approximately 20 vertical feet apart, with few partially opened fractures noted
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
during drilling. Well screens from GWA-27D and GWA-27BR are approximately 65
vertical feet apart, with limited fracture occurrences reported during drilling.
Reported conductivity and absence of constituent migration from deep to bedrock
flow zones support the unlikely presence of a strongly connected fracture system
from deep to bedrock flow zones. Well clusters GWA-20/SA/D/BR and GWA-
27S/D/BR are an example of the low connectivity between the transition zone and
bedrock at BCSS. This contention is address in the F&T modeling report (CAP
Update Appendix G).
DEQ Formal Comment 8
For each water supply well that exhibits concentrations of constituents exceeding 02LIIMACs or
preliminary background threshold values (PBTVs), whichever are higher, provide an evaluation
concerning potential receptors based on actual site data including piper -diagrams, co-occurring
constituents, proximity to CCRs, topographic setting, geology, and dissolved oxygen, pH, etc.
Response Summary 8
Information regarding water supply wells can be found in Section 6.3.2 Water
Supply Wells Associated With Source Area with comparisons of analytical data to
applicable standards and explanation of potential impacts provided on Table 6-9
Water Supply Well Summary.
DEQ Formal Comment 9
Provide an explanation why radium is not considered a COI.
Response Summary 9
Radium-226 and radium-228 are not considered COIs at Belews Creek based on the
following
• There are no total radium exceedances in ash pore water analytical results
• Exceedances of total radium are horizontally and vertically spatially sporadic
across the Site and flow zones with no apparent pattern along Site flow
conditions.
Historical total radium exceedances of either the Federal MCL or BTV, whichever is
greater, have occurred in wells AB-21), BG-11), GWA-19S, GWA-201), GWA-20SA,
GWA-271), MW-200D and MW-202S; however subsequent sampling events have
recorded total radium concentrations below the Federal MCL and are not considered
for additional monitoring of radium. Wells AB-9BRD, GWA-10S, and MW-104BR
have had at least three historical total radium exceedances of either the Federal
MCL, including the most recent sample collected for total radium. AB-9BRD and
MW-104BR have high pH indicative of grout impact. MW-104BR had been since
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
replaced with MW-104BRA with no exceedance of radium indicated for two
sampling events.
DEQ Formal Comment 10
The pH values observed in GWA-19BR, GWA-20BR, and especially GWA-27BR, (the most
downgradient bedrock well in the northwest area) are consistently high likely due to improper
well construction. Whether these wells should be replaced needs to be discussed.
Response Summary 10
These wells are identified in the current IMP. It has been documented, with DEQ
concurrence, that boron is not sensitive to pH related grout impacts. Because
bedrock wells GWA-19BR and GWA-27BR have no boron detected in all sample
results, these wells provide vertical and horizontal delineation of the bedrock boron
plume northwest of the basin and should be maintained in the IMP.
Well GWA-20BR has historical detections of boron with the maximum concentration
of 91.4 ug/L. This well also has detectable concentrations of several COIs including
antimony, arsenic, chromium, molybdenum and vanadium. Leaching, dissolution
and sorption of these constituents are pH dependent, where high alkaline pH
increases the likelihood that measureable concentrations in groundwater (Izquierdo
et al., 2012). Based on Site Kd values for arsenic, chromium, molybdenum and
vanadium derived from extensive geochemical modeling it is unlikely these
constituents at concentration levels observed are a reflection of migration of these
constituents from the ash basin. Although antimony demonstrates a low Kd value
and can be as mobile as boron, antimony is influenced by high pH conditions. It is
likely the alkaline pH measured in GWA-20BR is affecting constituent leaching
behavior in groundwater that is not representative of background conditions or
migration of constituents in groundwater from the ash basin. Based on these results,
well GWA-20BR is appropriate for monitoring migration of boron from the ash
basin, but not for constituents that are mobilized under high pH conditions
including antimony, arsenic, chromium, molybdenum, and vanadium.
DEQ Formal Comment 11
Soil contamination should be delineated to either the site -specific preliminary background
concentrations (PBTVs) or Protection of Groundwater (POG) Preliminary Soil Remediation
Goals (PSRGs) levels, whichever are higher. If appropriate, use the equation provided in the
PSRG table to establish a POG PSRG for a constituent with 02L standard that does not have
one.
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
Response Summary 11
Discussion of analytes considered for soil COIs can be found in Section 6.1.2
Chemistry within Waste Boundary (Soil within the Waste Boundary), along with a
discussion and method for calculating chloride and sulfate POG PSRG values of
which did not have existing standards for comparative purposes. Analytical results
for unsaturated soil within the waste boundary can be found on Table 6-3 Summary
of Unsaturated Soil Analytical Results. Only unsaturated fill material sample AB-01S
(20-21.5 feet bgs), collected from the ash basin dam, has concentrations of arsenic
(61.1 mg/kg) and iron (40,600 mg/kg) greater than the PSRG for POG or BTV,
whichever is greater. Arsenic and iron concentration are within range of background
soil concentration (Table 6-3). Additionally, source control and ash basin closure
activities will lower water elevation in this area, reducing the potential for leaching
constituents into the groundwater system. No other unsaturated soil samples within
the waste boundary had concentrations greater than PSRG POG or BTV values.
DEQ Formal Comment 12
Provide plan view maps and cross -sections (where applicable) to demonstrate that soil
contamination (POG PSRGs or PBTVs, whichever are higher) has been vertically and
horizontally delineated.
Response Summary 12
A discussion regarding the extent of unsaturated soil COIs in provided in Section
6.2.2.1 Unsaturated Soil COI Extent. Unsaturated soils samples at or near the
compliance boundary were collected from borings during well installation activities
upgradient of the ash basin from wells GWA-05S, GWA-07S, GWA-08D, GWA-
09GTB, and MW-202BR; and downgradient of the ash basin from wells GWA-01S,
GWA-10D, and MW-200BR (Figure 6-5 Unsaturated Soil Sample Locations). An
evaluation of the potential nature and extent of COIs in unsaturated soil beyond the
waste boundary was conducted by comparing unsaturated soil concentraitons with
BTVs or PSRG POG standards, whichever is greater (Table 6-3). PSRG POG
standards were calculated for chloride (938 mg/kg) and sulfate (1,438 mg/kg) (Table
6-2). Although greater than the BTV or PSRG POG, arsenic, chromioum, iron, and
selenium detections at or near the compliance boundary are within the range of
concentrations detected in soil samples from background locations as shown in
Table 6-3. Additionally, all unsaturated soil samples with values reported greater
than the PSRG POG standard or BTV, including barium detected at GWA-09GTB
(40-41.5), are vertically delineated by groundwater constituent concentrations in the
corresponding flow layer of the soil sample depth.
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Because all soil concentrations, with the exception of barium, are within range of
background soil concentrations, and all soil concentrations are delineated by
groundwater concentrations, indicating there is no potential secondary source to
groundwater from leaching of soil constituents, no soil exceedances are identified
for corrective action at the Site.
DEQ Formal Comment 13
Provide additional assessment concerning the comingling of plumes from the onsite Structural
Fill with the ash basin. To determine whether the contaminated groundwater from the Structural
Fill contributes to the plume resulted from the ash basin, at least an additional monitoring well
between GWA-8S and the Structural Fill, but at the northern side of Pine Hall Road, should be
installed. The result will help determine whether the source of boron in GWA-8S is from the ash
basin or the structural fill. Sampling results from SFMW-ID and SFMW-2D and bedrock well
(expected from DWM) are also needed to determine the vertical extent of the plume from the
Structural Fill.
Response Summary 13
Other facilities at the Site are not part of the source area addressed herein. A
consensus was reached with the NCDEQ DWR regarding sources not considered for
corrective action as part of this CAP Update was provided in a letter from NCDEQ
to Duke Energy dated April 5, 2019 (CAP Update Appendix A). The letter states that
a CSA for primary and secondary sources not associated with impoundments,
including the Structural Fill at Belews Creek, are due March 31, 2020. Assessment of
the Structural Fill, and other primary and secondary sources at Belews Creek, are
ongoing with state approved work plans and agreed upon well installation
locations. To date, six additional wells have been drilled around the Structural Fill as
a part of the additional source assessment, including bedrock wells SFMW-1BR and
SFMW-2BR, co -located with deep wells SFMW-1D and SFMW-2D. Newly installed
wells at the Structural Fill have been sampled for the first time in October 2019.
Water levels (Figures 5-4a through 5-4c) support groundwater divides control the
flow of groundwater within the ash basin and PHR Landfill drainage system, south,
east and west of the source area. With the exception of the northwest corner of the
ash basin, groundwater on the basin side of each ridge flows toward the basin while
groundwater on the opposite side of the ridge flows away from the basin. The
hydraulic divides provide natural hydraulic control of ash basin constituent
migration within the stream valley system, with the predominant direction of
groundwater flow being to the north. Groundwater model simulations support the
hydraulic separation of the ash basin and the Structural Fill and indicate that
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lowering the hydraulic head in the ash basin by decanting and subsequent closure
will strengthen groundwater divide (CAP Update Appendix G).
Constituent concentrations of conservative constituents including boron, chloride
and TDS, support a hydraulic divide represented along Pine Hall Road creating
separate groundwater plumes from these two source areas. Boron concentrations
from shallow well GWA-08S are less than the 02L Standard of 700 µg/L, no boron is
detected GWA-81); and the nearest well between GWA-8S/D and the Structural Fill
is SFMW-2D which has had no boron detected from two rounds of sampling (Cap
Update, Appendix C, Table 1).
Additional well installation, sampling activities, and Site assessment relating to the
Structural Fill will be documented in the Structural Fill CSA report.
DEQ Formal Comment 14
Whether additional sediment assessment is needed at S-6, S-10, S-11, BCSW-007, BCSW-008,
and BCSW-19 area should be discussed.
Response Summary 14
Several of the sediment locations are related to facility operations (BCSW-007) or
solid waste facilities unrelated to the ash basin (BCSW-008 (FGD Landfill) and
BCSW-19 (Craig Road Landfill)). These locations are not within the ash basin
drainage system and therefore are not considered part of the ash basin CAP
assessment activities. Non -constructed seeps S-2, S-6, S-8, S-9, S-10 and S-18 contain
evidence of impact from the coal ash basin; elevated concentrations of arsenic,
chromium, cobalt, and iron greater than preliminary soil remediation goals (PSRG)
standard, and impacts from those seeps are deemed covered by the approved SOC.
The SOC contains provisions for monitoring and evaluation of the seeps after
decanting of free wastewater from the ash basin. For these locations, the evaluation
of current conditions is addressed by the terms of the SOC and the evaluation of
future conditions at these locations will be performed as required by the SOC.
Sediment sampling is not required by the SOC. Seep S-11 is a constructed seep and
monitoring is established per terms of the NPDES Permit. Sediment sampling is not
required under the NPDES Permit. If additional sediment sampling is performed at
seep locations dispositioned by the SOC, sample activities and analytical results will
be documented in the CAP amendment.
DEQ Formal Comment 15
Please provide a description of the Chemical Pond in terms of its content, history, and function
relative to the NPDES permit.
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Response Summary 15
The Chemical Pond is a small impoundment that was utilized to collect chemical
wash -down water from boiler cleanings. The Chemical Pond is located east of the
PHR Landfill and within a remnant finger of the ash basin (Figure 1-2). The 2.9 acre
pond was reportedly constructed from 1972 to 1974 and was last used during the
spring of 2009. Boiler and filter cleaning wastes were generated from chemical
cleaning of the steam station boilers, which were cleaned on an as -needed basis. The
chemical cleaning wastes were pumped to the chemical holding pond. After
treatment, the pond effluent was discharged into the ash basin at a controlled rate to
provide further treatment. Historic chemical rinse water inflows to the ash basin
from boiler and other equipment cleanings were highly variable and difficult to
predict. Duke Energy estimates that a minimum of 750,000 gallons of rinse water
would be used during a typical boiler cleaning event. The chemicals and
approximate amounts for one boiler cleaning are as follows:
Chemical
Amount
Hydroxyacetic acid
50,300 pounds
Formic Acid
20,600 pounds
Ammonium Hydroxide
2,100 gallons
Ammonium Bifluoride*
4,200 pounds
Hydrazine
700 pounds
Corrosion Inhibitor (Proprietary)
500 pounds
According to the current NPDES permit, waste streams from the Chemical Pond
were monitored through NPDES Outfall 003. The Chemical Pond is considered
within the scope of the CAP since the impoundment is a part of the ash basin.
Additional information regarding the Chemical Pond content, history, and function
can be found in Section 3.0 of the CAP Update report.
DEQ Formal Comment 16
Provide an explanation of how and why soil contamination occurs outside of any waste
boundaries and more detailed discussion or evidence as to the reason for the elevated
concentrations of chromium, iron, strontium and vanadium in soils upgradient of the ash basin
(GWA-6S, GWA-7S, and GWA-8D).
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Response Summary 16
Information regarding upgradient, unsaturated and saturated soil samples from
borings GWA-6S, GWA-7S, and GWA-8D can be found in Section 6.2.2.2
Unsaturated Soil COI Extent.
While some strontium and vanadium soil concentrations from GWA-6S, GWA-7S,
and GWA-8D are above the PBTV, all are below the PSRG POG value. All chromium
concentrations but two (GWA-6S (68.5-70') and GWA-7S (30-31.5')) are below the
site specific PBTV; and all iron concentrations but one (GWA-6S (68.5-70')) are below
the site specific PBTV. Soil chemistry results of elemental composition were
completed for soil sample GWA-7D (44') (CSA, 2015). Results indicated this area has
the highest concentrations of cobalt, chromium, nickel, tin, vanadium and zinc
compared to any other onsite soil samples. Nickle, tin and zinc are not considered
to be COI's related to the ash basin. Chromium, iron and vanadium are naturally
occurring in the Piedmont region, and based on site specific Ka values are a
relatively immobile. Due to the natural occurrence of elements, understanding of
Site groundwater divides and flow directions, and the unlikeliness that chromium,
iron and vanadium have migrated in groundwater a significant extent from the ash
basin (based on extensive groundwater monitoring data and geochemical modeling)
as well as the absence of other Site COI's, these elevated soil metals concentrations
do not suggest migration of these constituents from the ash basin.
DEQ Formal Comment 17
Isoconcentration maps: If a well was sampled, even when pH was elevated, the data should be
used to plot isoconcentration maps with footnotes that explain that better quality data are needed
to provide a more accurate assessment of site conditions. In addition, as a certain number of
wells were not sampled in April 2017, the isoconcentration maps may not represent true site
conditions (plume shape and size). Therefore, all isoconcentration maps should be updated with a
complete sampling event including all wells, (including CCR wells, if appropriate) and present
the updated maps in the CAP. Otherwise, if the maps could not be updated with adequate data,
please provide isoconcentration maps for each sampling event for boron. Furthermore,
assumptions made concerning how groundwater plumes are depicted without a monitoring well
in the middle of the ash basin or the landfill should be provided. For examples figures 10-44, 10-
54, etc.
Response Summary 17
Under a COI management matrix approach, revised isoconcentration maps are
provided using updated analytical data from CAMA and CCR monitoring
incorporating available qualified data through June 2019 as CAP Update Figure 6-
11a through 6-21b.
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Installation of a groundwater monitoring well in the middle of a lined or capped
landfill is not feasible without affecting the integrity and effectiveness of the source
control measures in place.
DEQ Formal Comment 18
Figure 2-10 should be updated to include all CCR well locations.
Response Summary 18
A revised Site Layout figure to include CCR well locations is provided as Figure 1-2
of the CAP Update report.
DEQ Formal Comment 19
Additional comments regarding figures and tables can be discussed in detail between WSRO and
Duke Energy staff prior to completing the CAP.
Response Summary 19
This item has been further discussed during the NCDEQ meeting on May 25, 2018.
DEQ Formal Comment 20
Additional surface water sampling along the east bank of Belews Reservoir was discussed in May
18, 2017 meeting between Duke and DEQ. A sampling proposal was submitted by Duke
through an email on October 4, 2017 and agreed to by the division staff, however, the proposed
sampling was not performed. The additional agreed upon surface water assessment must be
completed and included in the CAP. All samples must be collected in accordance with DEQ's
Internal Technical Guidance: Evaluating Impacts to Surface Water from Discharging
Groundwater Plumes.
Response Summary 20
Surface water sampling related to potential groundwater impacts to the Dan River
and Belews Reservoir was conducted in January/February 2018. The sampling
efforts were completed in accordance with DEQ's Internal Technical Guidance as
referenced. The sampling activities, results and evaluation are provided in
Appendix K of the CAP Update report.
DEQ Formal Comment 21
For any sample results deemed invalid, state what caused the sample to be invalid, the rationale
for not including the data, and any proposed remedies such as plans for resampling. (Refer to
Section 9.1).
Response Summary 21
In reference to Section 9.1 (CSA Update, 2017), the following statement was made
"Analytical results with the dissolved phase concentrations greater than their
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associated total reportable concentrations are not included in the assessment as they
are considered invalid". The invalid reference is related to the detection of
hexavalent chromium at greater concentrations than total chromium. Total
chromium in its aqueous phase exists in two different chemical forms, trivalent
chromium or hexavalent chromium. Because total chromium is a measurement of
both chemical forms, it is not possible to have hexavalent chromium data with
greater concentrations than total chromium.
For the CAP evaluation, only validated data is used. The data validation process
involves a thorough review to quality control criteria including:
• Does sample field preservation meet EPA or method recommendations
• Was the sample prepared/analyzed after the recommended holding time
• Is the analyte concentration in a blank greater than 10x the Reporting Limit
(RL) and/or greater than the EPA Primary MCL/NCAC 2L Groundwater
Standard (or other applicable standard)
• Is the Laboratory Control Sample (LCS) recovery less than 50% or greater
than 150% (meaning the lab's method/instrumentation failed quality control
for the analyte(s) and, therefore, cannot be relied upon to provide reliable
data)
If the data fails the QC criteria, the data is considered unusable and flagged with an
RO designation. The rationale for not including RO flagged data is, in our
professional judgement, the data cannot be relied on as accurate due to an error with
the collection and/or analysis methods.
DEQ Formal Comment 22
Provide a rationale or evidence that suggests that underground utilities will not serve as
preferential conduits for contaminant movement.
Response Summary 22
NORR CSA guidance requires that subsurface utilities are to be mapped within
1,500 feet of the known extent of groundwater impact in order to evaluate the
potential for preferential pathways. Identification of piping near and around the ash
basin was conducted by Stantec in 2014 and 2015 and utilities around the Site were
also included on a 2015 topographic map by WSP USA, Inc. (SynTerra, 2017b). It is
anticipated that any underground utilities present at the Site would not act as
potential preferential pathways for contaminant migration through underground
utility corridors especially to water supply well receptors because the depth to the
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water table is greater than typical corridor construction depths for underground
utilities.
DEQ Formal Comment 23
Section 6.5 states: "Hydraulic conductivity values for wells screened in saprolite have a
geometric mean of 2. 65 x 10-4 cm/sec. Hydraulic conductivity values for wells screened in the
transition zone have a geometric mean of 7.91 x 10-5 cmisec. These measurements reflect the
dynamic nature of the transition zone, where hydrologic properties can be heavily influenced by
the formation of clays and other weathering by-products." To justify this statement, please
provide evidence showing the transition zone has higher clay content and other weathering by-
product than the shallow aquifer at this site as hydraulic conductivity is lower in the transition
zone than in the shallow aquifer.
Response Summary 23
From hydraulic conductivities reported in the CSA Update, shallow wells (saprolite)
have a range from 3.70E-6 to 3.76E-3 cm/sec. Only one shallow monitoring well (AB-
2S) out of 24 shallow monitoring wells had a hydraulic conductivity similar to clay
(3.70E-6). In the deep wells, approximately ten wells (AB-31), BG-11), GWA-71),
GWA-10D, GWA-11D, GWA-16D, GWA-11), GWA-18D, GWA-19D, and GWA-22D)
out of 33 wells have hydraulic conductivities ranging from 3.43E-7 to 9E-6 cm/sec.
The analyzed slug tests show approximately 4% of the shallow wells have hydraulic
conductivities similar to clay. In the deep wells approximately 30% of the wells
analyzed in slug tests have low permeability similar to clay (Domenico and
Schwartz, 1990). It should be noted that the ten wells in the deep zone with
conductivities similar to clay are spatially sporadic and do not indicate a site wide
occurrence.
DEQ Formal Comment 24
Provide an explanation or documentation concerning the statement (Section 6.6) that bedrock
fractures tend to be isolated with low interconnectivity and the primary porosity is considered
negligible, and correlate the statement to the horizontal and vertical migrations of COIs in the
bedrock.
Response Summary 24
Slug tests conducted in BCSS bedrock wells, screened near the top of the bedrock
surface, gave hydraulic conductivity values ranging from2.82E-7 to 8.82E-4 cm/sec.
However, hydraulic characteristics of existing BCSS bedrock monitoring wells have
few or no field data to support horizontal or vertical spatial extrapolation of
fractured hydraulic characteristics, especially at depths greater than existing
monitoring zones. Consistent with Legrand 1988, fractured impermeable bedrock is
the most abundant lithologic unit underlying the Piedmont region and deeper
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bedrock zones are largely unfractured (represented by high rock quality designation
(RQD) values, and lithology recorded during installation of BCSS deep bedrock well
AB-9BRD, in which case they would have even lower permeability and conductivity
not currently represented by available BCSS bedrock data. The range of observed
conductivity in the bedrock wells highlights the very large degree of heterogeneity
in the system and the need for further evaluation of bedrock and deep bedrock
interconnectivity and porosity to understand the horizontal and vertical migrations
of COIs in the bedrock.
As described in Section 6.2.2 COI Migration at or Beyond Compliance Boundary
(Bedrock Fracture Network for Groundwater Flow), the bedrock hydraulic
conductivity at the Site and calculated fracture apertures decrease with increasing
depth below the top of rock (Appendix F, Deep Bedrock Evaluation Report). The
observed decline in bedrock hydraulic conductivity and hydraulic aperture with
increasing depth is consistent with expectations based on the literature (Gale, 1982
and Neretnieks, 1985), and indicates that the overall volumetric rate of groundwater
flow in the bedrock decreases with depth (Appendix F). The available data do not
indicate any predominant bedrock fracture sets at BCSS. Overall, a wide range of
open fracture dip angles and dip directions is observed. Based on the orientations of
lineaments and open bedrock fractures, horizontal groundwater flow within the
bedrock should occur approximately parallel to the hydraulic gradient, with no
preferential flow direction (i.e., no expected, significant anisotropy) (Appendix F).
Consistent with this interpretation, the current groundwater flow model for BCSS
does not simulate plan -view anisotropy.
As described in Section 6.2.2 COI Migration at or Beyond Compliance Boundary
(Bedrock Matrix Characteristics for Flow and Transport), rock core samples from
bedrock locations which represent areas of affected groundwater migration, north
and northwest of the ash basin and are interpreted to coincide with zones of
preferential groundwater flow, were analyzed for porosity, bulk density and thin
section petrography. The reported matrix porosity values ranged from 0.50 percent
to 0.73 percent with an average of 0.62 percent. Bulk density ranged from 2.80 grams
per cubic centimeter (g/cm3) to 2.84 g/cm3 with an average of 2.82 g/cm3 (Appendix
F). Petrographic evaluation classified both samples as mica schist with a foliated
fabric (i.e., the elongated minerals are oriented parallel to each other or form some
bands). The principal minerals are biotite, quartz, muscovite, and plagioclase
(Appendix F). The reported matrix porosity values are within the range of those
reported for crystalline rocks in the literature (Freeze and Cherry, 1979; Lofgren,
2004; Zhou and others, 2008; Ademeso and others, 2012). The presence of
measurable matrix porosity suggests that matrix diffusion contributes to plume
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retardation at the site (Lipson and others, 2005). The influences of matrix diffusion
and sorption are implicitly included in the groundwater fate and transport model as
a component of the Kd term used for the bedrock layers model.
DEQ Formal Comment 25
Both groundwater and geochemical models must be updated and included in the revised CAP
due August 31, 2018.
Response Summary 25
The updated Flow and Transport Model can be found in Appendix G and the
updated Geochemical Model can be found in Appendix H of the CAP Update
report.
DEQ Formal Comment 26
All COIs should be modeled unless a rationale for not doing so is provided.
Response Summary 26
All COIs are modeled either in the updated Flow and Transport model or the
updated Geochemical Model with the exception of molybdenum. Molybdenum is
not modeled in the PHREEQC portion of the geochemical model because surface
complexation constants are not available within the surface complexation
database. However, molybdenum is discussed in terms of general geochemical
behavior and reactivity in groundwater within the Geochemical evaluation of plume(s)
and Site geochemical data section of the Geochemical Modeling report. The updated
Flow and Transport Model can be found in Appendix G and the updated
Geochemical Model can be found in Appendix H.
DEQ Formal Comment 27
In Section 3.3, implications for leachability and downgradient mobility of contaminants from the
source area should be discussed, as well as, implications for transport model source inputs and
for transport and risk should be discussed.
Response Summary 27
Leaching studies of consolidated ash samples were conducted using EPA methods
1313 and 1316 (USEPA, 2012a, b). Using Method 1316 data, the Kd and total
concentration of a COI on the solid phases were determined and represent
leachability and mobility of each source area constituent. Specifically, site specific
developed Kd values for boron and chloride in the coal ash are used in the Flow and
Transport model as source inputs. TDS was assigned the same Ka values as chloride.
This modeling approach for the predictive simulations of future COI transport allow
the COI concentration in the ash to vary with time in response to flushing by
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groundwater and representative realistic site conditions. Additionally, potential
changes to site conditions from various remedial activities is discussed in terms of
the Kd value in the geochemical model by evaluating how changes in pH and Ex
might affect the mobility of Site COIs (Appendix H, CAP Update report).
DEQ Formal Comment 28
In Section 4.4, it should be discussed whether the effects of pumping from the private water
supply wells were accounted for in the model with regards to particle tracking.
Response Summary 28
The water supply wells within the Site area remove only a small amount of water
from the overall hydrologic system and do not impact groundwater flow patterns
near the ash basin. The assumed consumption rates and locations of the water
supply wells are included in the Flow and Transport model which demonstrates this
conclusion (Appendix G). Further information can be found in Section 4.4 Flow
Model Sources and Sinks of Appendix G Updated Groundwater Flow and Transport
Modeling Report.
DEQ Formal Comment 29
Groundwater divides that have been identified at Pine Hall Road and Middleton Loop Road
(Section 6.3) should be reconsidered, because existing information confirms groundwater
beneath the ash basin flows across Middleton Loop Road towards northwest. Whether there is
uncertainty with respect to the position of groundwater divides for modeling particle tracks or
transport should also be discussed.
Response Summary 29
Information regarding Comment 29 can be found in Section 5.1 Flow Model
Residual Analysis and Figure 5-12 of the Updated Groundwater Flow and Transport
Modeling Report (Appendix G).
DEQ Formal Comment 30
The updated status of alternative water supply for supply wells within 0.5 miles of the BC
indicates that 52 households are eligible, 41 selected water filtration systems, 6 opted out of
selections of water line and water filtration system (refused both), and 5 did not respond. Please
list names and addresses of these 11 households and identify these properties on the map. In
addition, please also list the name and address for each vacant lot within 1500 feet of CB and
show them on the map.
Response Summary 30
On August 31, 2018, Duke Energy provided completion documentation to NCDEQ
to fulfill the requirements of House Bill 630. NCDEQ provided correspondence,
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dated October 12, 2018, to confirm that Duke Energy satisfactorily completed the
alternate water provisions under G.S. Section 130A-3099.211(cl) at BCSS. Both
documents are provided in CAP Update Appendix D. Households that opted out or
did not respond to the water treatment system program survey are identified in
CAP Update Appendix D.
Additionally, CAP Updated Figure 5-7a and 5-7b shows the private and public
water supply well locations with reference to water treatment systems installed
along with vacant parcels and residential properties whose owners have either
decided to opt out of the water treatment system program or did not respond to the
offer.
DEQ Formal Comment 31
Each of the constituents of concern identified in CAP Part 2 report that exceed their respective
risk target should be discussed.
Response Summary 31
The constituents of concern for groundwater and surface water that exceed their
respective risk target as identified in CAP Part 2 report are discussed in Section 6.4
Human and Ecological Risks. The update to the risk assessment evaluates
groundwater and surface water results for samples collected since the 2016 risk
assessment (March 2015 to June 2019) to confirm or update risk conclusions in
support of remedial actions is provided in detail in the Updated Human and
Ecological Risk Assessment (Appendix E).
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3.0 CSA UPDATE REPORT DRAFT COMMENTS AND RESPONSES
General Draft Comments
DEQ Draft Comment 1
The CSA is still incomplete. Delineation of horizontal and vertical extent of soil and
groundwater contamination is required by CAMA and 2L and has been highlighted since
August 13, 2014 when the Notice of Regulatory Requirements was issued to Duke Energy for its
14 facilities. As noted, plume shapes (beryllium, boron, and selenium in shallow zone, iron and
vanadium in deep zone, and thallium in shallow and deep zones) are so irregular and
concentrations varied dramatically in the northwest area, which implies complex hydrogeological
and geochemical conditions. Therefore, additional further downgradient well(s) appears to be
necessary although CCR data does show that boron in GWA-19 is sourced by the ash basin.
Based on the plume occurrence, GWA-31 is a side -gradient well, not a directly downgradient
well. For the same reason, to further delineate beryllium and thallium plumes, a further
downgradient well from GWA-21S appears to be needed.
Response Summary 1
See DEQ Formal Comment 1 response summary.
DEQ Draft Comment 2
Vertical extent: High level of boron has been consistently measured in MW-2-7 (22700 µg/L,
April 11, 2017) at Pine Hall Landfill. To determine the vertical extent, a bedrock well appears to
be needed. This was not requested before because it was thought to be addressed by DWM as this
part assessment is overseen by DWM. In addition, boron was detected in CCR-6D at a
concentration as high as 12400 µglL. If it is safe (at the foot of the main dam), a paired bedrock
well should be installed.
Response Summary 2
See DEQ Formal Comments 2 and 3 response summaries.
DEQ Draft Comment 3
How much additional data we can gain from DWM assessment at the Structural Fill? Whether
the contaminated groundwater from the Structural Fill contributes the plume caused from the
ash basin needs to be determined before CAP development. Sampling results from SFMW-1D
and SFMW-2D and bedrock well may be needed to determine the vertical extent. In addition, at
least, an additional monitoring well between GWA-8S and the Structural Fill, but in the
northside of Pine Hall Road, appears to be needed to determine the source of boron in GWA-8S
or whether plumes are comingled.
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Response Summary 3
See DEQ Formal Comment 13 response summary.
DEQ Draft Comment 4
Plan view maps and cross -sections are needed to show that the soil contamination
(concentrations exceed Protection of Groundwater (POG) Preliminary Soil Remediation Goals
PSRGs or Provisional Background Threshold Values (PBTVs), whichever are higher) has been
vertically and horizontally delineated.
Response Summary 4
An evaluation of the potential nature and extent of COIs in unsaturated soil at or
beyond the waste boundary was conducted by comparing unsaturated soil
concentraitons with background values or PSRG POG standards, whichever is
greater (CAP Update Table 6-3) can be found in CAP Update Section 6.1.1.4. A map
(Figure 6-5) of unsaturated soil and method for calculating chloride and sulfate POG
PSRG values of which did not have existing standards for comparative purposes
(CAP Update Table 6-2).
Data indicate unsaturated soil COI concentrations are generally consistent with
background concentrations or are less than regulatory screening values. In the few
instances where unsaturated soil COI concentrations are greater than PSRG POG
standards or background values, COI concentrations are within range of
background dataset concentrations or there are no mechanisms by which the COI
could have been transported from the ash basin to the unsaturated soils.
DEQ Draft Comment 5
The Chemical Pond should be further characterized as a source, including information such as its
content, history, and whether it was a component of the NPDES permit permitted waste water
system.
Response Summary 5
An overview of primary and secondary sources, along with reference to NCDEQ
consensus, is presented in Section 3.0 of the CAP Update.
The Chemical Pond is identified as hydrologically connected within the drainage
systems (i.e. watershed) of the ash basin. This small impoundment used to collect
chemical wash -down water, used in boiler cleaning, is located south of the ash basin.
The Chemical Pond was formerly part of the ash basin waste water treatment
system and drained to the ash basin. The pond was reportedly constructed from
1972 to 1974 with last use indicated during the spring of 2009. There are no
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historical engineering or construction documents pertaining to the Chemical Pond
or its dam. However, according to AECOM's BC-408 Feasibility Study report, 2015,
the Chemical Pond encompasses about 2.9 acres. According to the NCDEQ Dam
Safety Inventory, the dam is 508 feet long with a crest width of approximately 20
feet and side slopes of 2H:1V. Based on Light Detection and Ranging (LIDAR)
topographic information, the dam is assumed to be approximately 20 feet high at its
maximum point.
The Chemical Pond is closed and no longer receives inflows and is now drained
with its water level control valve locked in the open position. The pond was used to
collect chemical wash -down water from boiler cleaning. Inflows into this portion of
the ash basin system were reportedly received on average every three to four years
with last receipt indicated during the spring of 2009. Boiler and filter cleaning
wastes were generated from chemical cleaning of the steam station boilers, which
were cleaned on an as -needed basis. The chemical cleaning wastes were pumped to
the chemical holding pond. After treatment, the pond effluent was discharged into
the ash basin at a controlled rate to provide further treatment. Historic chemical
rinse water inflows to the ash basin from boiler and other equipment cleanings were
highly variable and difficult to predict. Duke Energy estimates that a minimum of
750,000 gallons of rinse water would be used during a typical boiler cleaning event.
Waste streams from the Chemical Pond were monitored through former Outfall 003.
There is no evidence that source material associated with the Chemical Pond has
contributed to any COI migration in groundwater, and therefore this facility is not
carried forward as source for corrective action. However, it is understood that this
area represents inflow to the ash basin drainage network and a critical area to
understand the effects of decanting, and therefore the ash basin finger north of the
chemical pond, along with other ash basin fingers are monitored for effects of
decanting and dewatering using pressure transducers.
DEQ Draft Comment 6
In addition, to investigate any 2B violations that may be caused from groundwater discharge,
additional surface water sampling along the east bank of Belews Reservoir was discussed in May
18, 2017 meeting between Duke and DEQ. Subsequently, a sampling proposal was submitted by
Duke through an email on October 4, 2017. However, the proposed sampling was not performed,
but more were proposed in the report. Need to know the result or status of the proposed
sampling.
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Response Summary 6
The proposal for sampling surface water locations within Belews Reservoir and the
Dan River to assess groundwater -to -surface water affects was approved by NCDEQ
in early 2018 and sampling was completed in February 2018.
Surface water samples were collected from the Dan River and Belews Reservoir to
confirm groundwater downgradient of the ash basin has not resulted in surface
water concentrations greater than 02B water quality standards. Groundwater
monitoring data consistently indicate the ash basin constituent plume does not
extend to either the Dan River or the Belews Reservoir. A map of all surface water
sample locations for groundwater discharge to surface water evaluation is included
in CAP Update Appendix K. Surface water samples were collected, using division
approved protocols, to evaluate acute and chronic water quality values. Surface
water samples were also collected at background locations (upgradient of potential
migration areas) within the Dan River, and Belews Reservoir. Analytical results
were evaluated with respect to 02B water quality standards and background data.
DEQ Draft Comment 7
Whether plumes of boron, chloride, and other COIs are still expanding or moving should be
thoroughly evaluated.
Response Summary 7
Plume behavior stability for conservative COIs is discussed in Section 6.1.5.1 of the
CAP Update report. This aligns with the CAP guidance provided by NCDEQ) in a
letter to Duke Energy, dated April 27, 2018 and adjusted on September 10, 2019.
Plume behavior stability was evaluated using statistical trend analysis for all
constituents (CAP Update Table 6-7). Results of the trend analysis suggest the
northern and northwestern groundwater plumes appear unstable, with several
conservative constituents indicating increasing concentration trends, with some
locations greater than comparative criteria.
DEQ Draft Comment 8
The pH value in GWA-19BR, GWA-20BR, and GWA-27BR, especially GWA-27BR, the most
down gradient bedrock well in NW is consistently high. Whether these wells should be replaced
need to be discussed.
Response Summary 8
See DEQ Formal Comment 10 response summary.
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CSA Update Report Comments and Responses December 2019
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DEQ Draft Comment 9
Updated status of alternative water supply for supply wells within 0.5 miles of BC indicates that
52 households are eligible, 41 selected water filtration systems, 6 opted out of selections of water
line and water filtration system (refused both), and 5 did not respond. Please list names and
addresses of these 11 households and identify these property on the map. In addition, please also
list the name and address for each vacant lot within 1500 ft. of CB and show them on the map.
Response Summary 9
See DEQ Formal Comment 30 response summary.
DEQ Draft Comment 10
Document "no impact" to each private supply well which contains constituents that were also
found in coal ash and exceeds 2L/IMAC or PBTV, whichever is higher, by providing pieces of
evidence, such as geology, hydrogeology, geochemistry, etc.
Response Summary 10
All water supply wells within 0.5 miles of the ash basin are upgradient and/or
separated from the ash basin by a hydrologic divide. Groundwater concentrations of
boron, which is a constituent that conservatively indicates influence from the Belews
Creek ash basin or closed PHR Landfill, is not detected in the vicinity of the water
supply wells and is only detected in bedrock monitoring wells at locations within
the compliance boundary, approximately over 3,000 feet from the closest water
supply well.
Table 6-9 in the CAP Update highlights each private water supply well with
comparisons to 02L/IMAC or PBTV standards. Each exceedance is rationalized with
pieces of evidence stating geology and hydrogeology.
DEQ Draft Comment 11
Provide specific evaluation for water supply wells BC1 and BC13 is needed. These two wells may
be potentially impacted from groundwater impacted by coal ash. BC1 is relatively close to the ash
basin and upward hydraulic gradient was measured in the area. Boron was detected in BC-13.
Response Summary 11
Table 6-9 in the CAP Update highlights each private water supply well with
comparisons to 02L/IMAC or PBTV standards. Each exceedance is rationalized with
pieces of evidence stating geology and hydrogeology. All water supply wells within
0.5 miles of the ash basin are upgradient and/or separated from the ash basin by a
hydrologic divide.
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CSA Update Report Comments and Responses December 2019
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DEQ Draft Comment 12
Whether plumes of boron and chloride are still expanding or moving should be thoroughly
evaluated, and conclusions should be made. Representative wells should be selected for trend
analysis (i.e. increasing/decreasing COI trends).
Response Summary 12
Plume behavior stability for conservative COIs is discussed in Section 6.1.5.1 of the
CAP Update report. This aligns with the CAP guidance provided by NCDEQ in a
letter to Duke Energy, dated April 27, 2018 and adjusted on September 10, 2019.
Plume behavior stability was evaluated using statistical trend analysis for all
constituents (CAP Update Table 6-7).
DEQ Draft Comment 13
Whether 11,200 µglL of boron at GSA-20SA (Fig. 10-17) would drop to 852 µglL at GWA-11S,
and 184 µglL at GWA-21S through dilution alone should be discussed. Whether the well
positions or screened intervals of GWA-11S and GWA-21S are measuring the flow path away
from the hot spot should be discussed.
Response Summary 13
See DEQ Formal Comment 6 response summary.
DEQ Draft Comment 14
High boron concentrations were detected in deep wells (e. g., 9890 µglL at GWA-20D and 5420
µglL at GWA-27D), but no 2L exceedances were measured in their paired bedrock wells.
Whether these results are supported by site hydrogeologic conditions andlor groundwater
hydraulic property, such as vertical hydraulic gradient and conductivity, should be discussed.
Response Summary 14
See DEQ Formal Comment 7 response summary.
DEQ Draft Comment 15
Isoconcentration maps: If a well was sampled, even pH was elevated, the data should be used to
plot isoconcentration maps with noting until good data is available. In addition, as a certain
number of wells were not sampled in April 2017, isoconcentration maps should be plotted with
considering historical data, otherwise, plume occurrences may not be representative. For
examples figure 10-7, figure 10-10, etc. Furthermore, attention should be paid for how
groundwater plumes should be drawn without a monitoring well in the middle of the ash basin
or the landfill. For examples figures 10-44, 10-54, etc. Representative cross sections should be
selected for assessment of vertical extent.
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CSA Update Report Comments and Responses December 2019
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Response Summary 15
Noted. Revised isoconcentration maps are provided using updated analytical data
from CAMA, CCR, compliance monitoring incorporating available qualified data
through April 2019 as Figures 6-11a through 6-21b. Constituent contours mapped in
shallow deep, and bedrock when present include; arsenic, beryllium, boron,
chloride, cobalt, iron, lithium, manganese, strontium, TDS, and thallium.
DEQ Draft Comment 16
Whether the raw coal pile area should be assessed needs to be discussed. Plumes of cobalt,
manganese, strontium may be sourced by the coal pile.
Response Summary 16
A consensus was reached with the NCDEQ DWR regarding sources not considered
for corrective action as part of this CAP Update was provided in a letter from
NCDEQ to Duke Energy dated April 5, 2019 (CAP Update Appendix A). The letter
states that a CSA for primary and secondary sources not associated with
impoundments, including the coal pile at Belews Creek, are due March 31, 2020.
Assessment of the coal pile, and other primary and secondary sources at Belews
Creek, are ongoing with state approved work plans and agreed upon well
installation locations.
To date, 22 groundwater monitoring wells have been installed around the coal pile
as a part of the additional source assessment. Newly installed wells at the coal pile
have been sampled for the first time in October 2019. Additional well installation,
sampling activities, and Site assessment relating to the coal pile will be documented
in the CSA report.
DEQ Draft Comment 17
Figure 2-10 should be updated to include all CCR well locations.
Response Summary 17
Noted. A comprehensive Site layout map showing Site features, NPDES Outfalls,
source area waste boundaries and compliance boundaries (if applicable), and all
media (i.e. soil, groundwater, surface water, sediment) sample locations is included
as Figure 1-2 in the CAP Update.
DEQ Draft Comment 18
SynTerra must review and certify that the data and evaluations contained in this report are
accurate and correct no matter who performed previous work. (Note, at very beginning of the
report, Work Performed by Others: "The seal of the licensed geologist for this CSA applies to
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activities conducted and interpretations derived after the HDR reports were submitted. This
submittal relies on the professional work performed by HDR and references that work. ")
Response Summary 18
Noted. A review of anomalous historical sample results for constituents of interest
was completed by SynTerra.
Section Specific Draft Comments — Executive Summary
DEQ Draft Comment is
ES.3.2. "Although several water -supply well concentrations reported are greater than the site
specific provisional background threshold values (PBTVs), the concentrations are within the
background concentration range for similar Piedmont geologic settings." This statement is too
general. Please note that no concentration range for similar Piedmont geologic setting is
provided rather than PBTVs from 11 Duke Energy coal ash sites simply piled and presented in
Section 4. These sites are in different geologic setting or hydrogeologic units, so concentrations of
trace metals in groundwater can be different.
Response Summary is
In the CAP Update Table 6-9, water supply well concentrations were compared to
BCSS site specific background values, rather than Piedmont background values.
Per the CAP guidance provided by NCDEQ) in a letter to Duke Energy, dated April
27, 2018 and adjusted on September 10, 2019 "A discussion of regional background
concentrations for similar geologic settings may be provided as context for BTVs."
The BCSS and nine other Duke Energy facilities (Allen Steam Station, Buck Steam
Station, Cape Fear Steam Electric Plant, Cliffside Steam Station, Dan River Steam
Station, Marshall Steam Station, Mayo Steam Electric Plant, Riverbend Steam
Station, and Roxboro Steam Electric Plant) are situated in the Piedmont
physiographic province of north -central North Carolina. The nine Duke Energy
facilities are located within a 120-mile radius from Belews Creek. Statistically
derived background values from these facilities provide a geographic regional
background range for comparison. Generally background values derived from the
Piedmont facilities are similar, with some exceptions. Piedmont background value
ranges are presented in Table 4-3 in the CAP Update for information purposes.
DEQ Draft Comment lb
ES.3.3. "Several surface water bodies flow from the topographic divide along Middleton Loop
Road toward the Dan River within a 0.5-mile radius of the ash basin." The word "several"
should be replaced by a numerical number. Whether they are permitted effluent channels or
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CSA Update Report Comments and Responses December 2019
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jurisdictional waters should be clarified. If these are jurisdictional waters, whether they are
impacted by CCR should be summarized.
Response Summary 1b
A depiction of surface water features — including wetlands, ponds, unnamed
tributaries, seeps, streams, lakes, and rivers — within a 0.5-mile radius of the ash
basin compliance boundary is provided in CAP Update Figure 5-6. The surface
water information is provided from the Natural Resources Technical Report (NRTR)
prepared by AMEC Foster Wheeler (July, 2015). The NRTR report identifies 10
jurisdictional streams north and northwest of the Belews Creek ash basin.
A Special Order by Consent (SOC) was issued to Duke Energy on July 19, 2018, to
address the elimination of seeps from Duke Energy's coal ash basins during the
separate and independent process of ash basin closure. Per the SOC seeps at Belews
Creek are subject to the monitoring and evaluation requirements contained in the
SOC. Non-dispositioned seeps, where monitoring conducted has indicated the
presence of CCR affects, include: S-2, S-6, S-8, S-9, S-10, S-11, and S-18. Seeps S-2,
S10, S-11 are located within three of 10 jurisdictional streams north and northwest of
the ash basin. CAP Update Table 6-8 summarizes 02B exceedances and potential
corrective action plans per seep location.
DEQ Draft Comment is
ES.3.4. "Water -supply well data collected since the risk assessment was completed indicates
several wells located to the west-southwest and northeast of the ash basin had concentrations of
chromium, cobalt, iron, manganese, vanadium that exceeded their respective water quality
standards, however all reported concentrations were less than their respective EPA risk -based
tap water screening levels." As these metals are discussed, arsenic detected in six wells above 2L
Standard should also be mentioned. Their EPA risk -based tap water screening levels should be
given or the source should be referred.
Response Summary 1c
An updated human health and ecological risk assessment pertaining to Belews
Creek was prepared and is included in CAP Update Appendix E. An evaluation of
arsenic is included in the updated risk assessment. Primary conclusions of the risk
assessment include: 1) there is no evidence of risks to on -Site or off -Site human
receptors potentially exposed to CCR constituents that might have migrated from
the ash basin; and 2) there is no evidence of risks to ecological receptors potentially
exposed to CCR constituents that might have migrated from the ash basin.
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CSA Update Report Comments and Responses December 2019
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DEQ Draft Comment 1d
ES.4.2. As discussing extent of contamination, the vertical extent and concentrations at the
deepest depth for each COI at the site should be summarized. Please also note that "Cobalt
exceedances were not reported in the deep and bedrock flow layers." is not true. It may not be
detected at or beyond the compliance boundary, but was detected above its PBTV/IMAC in
several deep wells and one bedrock well, AB-1BR, within the ash basin.
Response Summary id
Noted.
DEQ Draft Comment le
ES.4.3. Maximum Contaminant Concentrations (Source Information), please note that no
maximum contaminant concentrations were mentioned under this paragraph at all.
Response Summary 1e
Noted. Maximum constituent concentrations at or beyond the compliance boundary
are included in Table 6-6 of the CAP Update.
DEQ Draft Comment if
ES.5
• "The BCSS ash basin is currently designated as "Intermediate" risk under CAMA,
requiring closure of the ash basin by 2024. However, groundwater and surface water
quality data provide no indications of potential risk to human and wildlife receptors
related to constituent migration through the groundwater pathway from the ash basin.
These findings support a proposed "low" risk classification." Please note that to lower the
site risk classification to Low, the site needs to meet all criteria set in CAMA. In addition,
"2L-2B" sampling support is needed, but has not been completed. More thorough
evaluation of each water supply well containing exceedances of 21,/IMACs is also needed.
• 'Boron, beryllium, chloride, chromium, cobalt, manganese, and thallium are the primary
constituents detected in groundwater greater than PBTVs and 2L/IMAC near or beyond
the compliance boundary." Why is only primary and why only these constituents are
considered primary? All COIs that need remedial actions should be listed here.
Response Summary if
• Noted. Pursuant to G.S. Section 130A-309.213(d)(1) a November 13, 2018
letter from NCDEQ to Duke Energy, documented the classification of the
CCR surface impoundment at the Site as low -risk (CAP Update Appendix A).
The letter cited that Duke Energy has "established permanent water supplies
as required by G.S. Section 130A-309.211(cl)" and has "rectified any
deficiencies identified by, and otherwise complied with the requirements of,
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any dam safety order issued by the Environmental Management
Commission... pursuant to G.S. Section 143-215.32." The relevant closure
requirements for low -risk impoundments are in G.S. Section 130A-
309.214(a)(3), which states low -risk impoundments shall be closed as soon as
practicable, but no later than December 31, 2029.
• Noted. A COI management process was developed by Duke Energy at the
request of NCDEQ to gain understanding of the COI behavior and
distribution in groundwater and to aid in selection of the appropriate
remedial approach. Constituent requiring corrective action are discussed in
CAP Update Section 6.1.3.
DEQ Draft Comment 1g
Figure ES-1
• The model does not reflect groundwater flow directions very well. Groundwater does not
only flow N. NW, but also E. In addition, based on groundwater elevation contour maps,
(figures 6-6 through 6-11) and boron detected in GWA-8S, Pine Hall Road may not be a
groundwater divide.
• In addition, the boron plume caused from Pine Hall Road Landfill should be extended
further to SW beneath the landfill unless there is a monitoring well in the middle of the
landfill and does not indicate boron detection.
• The edge -line of the plume next to the Structural Fill should not be closed because the
structural fill is considered the source of the plume.
Response Summary 1g
• The flow and transport model has been undergoing a process of continuous
improvement and refinement by including new field data. The continuous
improvement process is designed to increase the accuracy and reliability of
the performance predictions. Updated groundwater elevation maps are
included as CAP Update Figures 5-4a through 5-4c. Additionally vector
velocity figures (CAP Update Figures 5-5a through 5-5c) are included in the
CAP Update, and provide further detail on groundwater flow direction and
velocity.
• Boron isoconcentration maps use empirical Site data and groundwater flow
and transport predictions to interpolate areas between well points. Updated
isoconcentration maps of boron indicate there is boron below the landfill.
• Noted. Site assessment relating to the Structural Fill will be documented in
the Structural Fill CSA report.
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CSA Update Report Comments and Responses December 2019
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DEQ Draft Comment 1h
As noted on Figure ES-1 (and some other later figures), streams were from AMEC NRTR
REPORT, 2015. Please include the AMEC report into Reference section.
Response Summary 1h
Noted. This reference is included in the CAP Update: Amec Foster Wheeler. July,
2015. "Natural Resources Technical Report."
Section Specific Draft Comments — Section 2
DEQ Draft Comment 2a
Figures 2-2 to 2-4, with all features loaded, are hard to see original features existed at the time
photo was taken or changes in land use from 1951 to 1977. Please remove all overloaded layers
but the waste boundary of the ash basin and Duke's property line.
Response Summary 2a
Noted. The 1966 aerial photo is included in the CAP Update as Figure 1-3 with no
Site features outlined besides the waste boundary and Duke Energy property line.
DEQ Draft Comment 2b
The unnamed streams shown on figures 2-6 and 2-7, and other relevant figures in later sections,
should be consistent or the same. As the Dan River is the NPDES permitted receiving stream
and a potential groundwater discharge receptor, please consider making it visible on all relevant
figures/maps if possible.
Response Summary 2b
Noted. All streams are represented the same on all CAP Update figures. The Dan
River is included and identified in relevant figures.
DEQ Draft Comment 2c
Can figure 2-10 also show locations (borings) where Kd samples were collected? Otherwise, a
separate figure for Kd sample location and depth should beprovided.
Response Summary 2c
Locations of Kd samples collected at the BCSS are identified on Figure 1 of the
geochemical modeling report (CAP Update Appendix H).
DEQ Draft Comment 2d
2-2. "... (Figure 2-7). Natural topography at the BCSS site ranges from an approximate high
elevation of 878 feet (NAVD 88) southeast... " Should be the last word southeast be southwest?
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CSA Update Report Comments and Responses December 2019
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Response Summary 2d
Correct. "Natural topography at the BCSS site ranges from an approximate high elevation
of 878 feet (NAVD 88) southwest of the ash basin near the intersection of Pine Hall Road
and Middleton Loop Road to an approximate low elevation of 646 feet at the base of the
earthen dike located at the north end of the ash basin."
DEQ Draft Comment 2e
2-5. "The Craig Road Landfill, FDG Landfill and the structural fill are located south of the ash
basin and are not hydrogeologically connected to the ash basin". If boron detected in GWA-8S is
from the structural fill, the structural fill may be hydrogeologically connected to the ash basin; to
determine, whether boron in GWA-8S is from the ash basin or the structural fill needs to be
further investigated.
Response Summary 2e
Constituent concentrations of conservative constituents including boron, chloride
and TDS, support a hydraulic divide represented along Pine Hall Road creating
separate groundwater plumes from these two source areas. Boron concentrations
from shallow well GWA-08S are less than the 02L Standard of 700 µg/L, no boron is
detected GWA-8D; and the nearest well between GWA-8S/D and the Structural Fill
is SFMW-2D which has had no boron detected from two rounds of sampling (Cap
Update, Appendix C, Table 1).
Section Specific Draft Comments — Section 3
DEQ Draft Comment 3a
"For the BCSS site, sources include the ash basin, Pine Hall Road Landfill, and the former
chemical pond." More information about the former chemical pond is needed. As a source, it
should be discussed as Ash Basin or Pine Hall Road Landfill was in this section.
Response Summary 3a
See response to DEQ Draft Comment 5 response summary.
DEQ Draft Comment 3b
3.3
1. The total volume of coal ash and the volume of saturated ash should be estimated,
respectively. If de -watering is done, the amount of saturated ash remaining should also be
estimated.
2. "Concentrations of arsenic, boron, chromium, cobalt, iron, manganese, selenium, and
vanadium were reported above soil background concentrations and the North Carolina
Preliminary Soil Remediation Goals (PSRGs) for industrial Health and/or Protection of
Groundwater for ash samples collected within the ash basin waste boundary (Appendix
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B, Table 4)."As characterizing the source, concentrations of these contaminants and the
volume of contaminated soil, the secondary source, should be discussed.
3. "The results of the SPLP analyses indicated that antimony, arsenic, chromium, cobalt,
iron, manganese, selenium, thallium, and vanadium exceeded their respective 2L
Standard or IMAC." In addition to this simple data summary, implications for
leachability and downgradient mobility from the source area should be discussed,
implications for transport model source inputs and for transport and risk should be
discussed.
4. "Background soil SPLP data collected from various sites in the Piedmont is presented as
Table 3-3. " Note that no Table 3-3 is provided in this report.
5. "The following metals leach from naturally occurring soils in similar geologic settings at
concentrations greater than 2L or IMAC: barium, chromium, cobalt, iron, manganese,
nickel, thallium, and vanadium." Please provide a table listing both background soil and
coal ash SPLP data. Please also explain what is meant by "similar geologic settings".
6. "The pore water sampling results show a decrease in constituent concentrations at some
locations with most locations showing stable concentrations. No significant increases in
constituent concentrations were observed." This statement needs to be supported with
values and wells from which the values were measured and trend plots. Implications
should also be discussed. Data is needed to support "no significant increases".
7. "The ash pore water is generally anoxic to mixed (oxic-anoxic). " Where does it vary from
this and why and how does this relate to COI concentration distribution and mobility
should be discussed.
8. "Ash pore water at BCSS for AB-4S, AB-7S, and AB-8S resembles bituminous coal ash
leachate water from EPRI's 2006 study which is a calcium -magnesium- sulfate water
type. In comparison, BCSS ash pore water from AB-6S and AB-8SL have an elevated
bicarbonate component." What caused the change and what are the Implications should
be discussed.
Response Summary 3b
1. Based on topographic and bathymetric surveys, the ash basin is estimated to
contain approximately 9,975,800 cubic yards (cy) of ash (Closure Options
Analysis, AECOM, 2018). Using modeled potentiometric levels of the
saturated ash surface compared to pre -ash basin historical topographic
contours, the volume of saturated ash within the basin under pre -decanting
conditions was approximately 9,180,000 cubic yards (AECOM, 2019).
2. Soil as a secondary source is discussed in CAP Update Section 6.1.4.
3. Two of the four Leaching Environmental Assessment Framework (LEAF)
tests (EPA Methods 1313 and 1316) were conducted on ash samples from
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BCSS to evaluate leaching characteristics of the Site -specific source material
(coal ash). Leach testing of ash samples reveals that the mass of leachable
COIs (ex: B, Co, Se) is less than the measured total mass determined by
complete sample digestion. LEAF testing on Site -specific ash samples was
conducted to better parameterize the source term in the flow and transport
model; LEAF data was also used to describe geochemical behavior of source
material (ash) in more detail in CAP Update Appendix H.
4. No saturated soils have been analyzed at Belews Creek for leachable
inorganics using SPLP procedures EPA Method 1312.
5. The soil background dataset and background values is included in CAP
Updated Appendix C, Table 4. Analytical results for ash synthetic
precipitation leaching procedures (SPLP) in included in CAP Update
Appendix C, Table 6. Similar geologic setting mean similar geologic and
hydrogeologic features, such as the settings of nine Duke Energy facilities
located in the Piedmont physiographic province of north -central North
Carolina.
6. An evaluation of trends in Site geochemical data is included as Attachment B
to the Geochemical Modeling report (CAP Update Appendix H).
7. Each COI exhibits unique geochemical properties related to the specific
constituent partition coefficient (Kd), response to changing geochemical
parameters (i.e., pH and Ex), and sorption capacity of the aquifer materials.
For example, ash decanting might introduce additional dissolved oxygen and
alter the Ex of the system; or sulfide mineral oxidation could cause locally
reduced pH values. Therefore, the effects of changing pH and Ex were
considered for each COI. An updated evaluation of trends in ash pore water
Site data is included as Attachment B to the Geochemical Modeling report
(CAP Update Appendix H).
8. Changes in ash pore water type could be from sourcing of coal burned at the
BCSS or from volume of different waste streams discharge to the ash basin
overtime.
Section Specific Draft Comments — Section 4
DEQ Draft Comment 4a
"It is anticipated that any underground utilities present at the site would not act as potential
preferential pathways for contaminant migration through underground utility corridors to water
supply well receptors." Rationale or evidence is needed for this statement.
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Response Summary 4a
See response to DEQ Formal Comment 22 response summary.
DEQ Draft Comment 4b
4.2
1. 'Based on the report, 19 of the 58 households surrounding BCSS have been recommended
for installation of an individual filtration system." Why only 19 have been
recommended? What status or what is the problem with the rest of households should be
discussed. Please provide a table listing the status of each well. The wells/households who
are not willing to have a filtration system to be installed should be identified.
2. "Several surface water bodies that flow from the topographic divide along Middleton
Loop Road toward the Dan River were identified within a 0.5-mile radius of the ash
basin. " As surface waters may be potential receptors, all jurisdictional water bodies
within 0.5 miles should be shown on a map or Figure 4-2. Each of surface water bodies
should be identified with its classification and distance from the compliance boundary.
Whether it has been impacted by groundwater from the ash pond should be discussed.
Response Summary 4b
1. On August 31, 2018, Duke Energy provided completion documentation to
NCDEQ to fulfill the requirements of House Bill 630. NCDEQ provided
correspondence, dated October 12, 2018, to confirm that Duke Energy
satisfactorily completed the alternate water provisions under G.S. Section
130A-3099.211(cl) at BCSS. Both documents are provided in CAP Update
Appendix D. Households that opted out or did not respond to the water
treatment system program survey are identified in CAP Update Appendix D.
2. A depiction of surface water features — including wetlands, ponds, unnamed
tributaries, seeps, streams, lakes, and rivers — within a 0.5-mile radius of the
ash basin compliance boundary is provided in CAP Update Figure 5-6.
Associated North Carolina surface water classifications for jurisdictional
water, Belews Reservoir and the Dan River, are summarized in CAP Update
Table 5-3. Discussion of surface water in included in CAP Update Section
6.2.1 and CAP Update Appendix K.
DEQ Draft Comment 4c
4.3
1. For each supply well, what co-occurring CCR constituents were found in the well and
whether these constituents were sourced by the coal ash basin or other coal ash fills
should be discussed.
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2. "Based on the bedrock groundwater flow direction at the site (Figures 6-10 and 6-11, .. .
The remaining water supply wells identified in the area are located upgradient or
sidegradient substantially beyond the expected flow zone of the BCSS ash basin." Please
discuss whether pumping affects are considered and on what basis the "expected flow
zone" extent was determined. More attention should be paid on BC1. It is not far from
the compliance or waste boundary and elevated manganese was detected in it.
3. 'Boron was not detected in any of these water supply wells sampled sidegradient of the
ash basin along Old Plantation Road." Whether boron was detected in other supply wells
should be also mentioned here.
4. Figure 4-3, why only these three supply wells (BC2 (well 1&2) and BC-2019) are shown
in the figure? If not all, at least BC4, BC4A and BC4B should be included as they are
located right downgradient of Pine Hall Road Landfill.
5. Whether boron detected in BC13 is an indicator of impact of coal ash should be discussed.
If it cannot be determined, the well should be monitored regularly.
6. PBTVs presented in Table 4-4 should be consistent with values presented in later other
tables. For example, manganese PBTV for Deep flow layer 55 ug/L is in Table 4-4 while it
is 13 µg/L in Table 10-2.
7. Please provide a table comparing the background concentration range for similar
Piedmont geologic setting (must be from the similar geologic setting) to each water
supply well constituent with concentration exceeding the bedrock PBTV or 2L standard,
whichever is higher.
Response Summary 4c
1. Section 6.2.2.2 of the CAP Update discusses findings of drinking water supply
well surveys and groundwater sampling results from water supply wells.
2. Because much of the area surrounding the ash basin is either residential
properties, farm land, or undeveloped land, potential offsite pumping
influences would be limited to domestic and public water supply wells.
Water supply wells are outside, or upgradient of the groundwater flow
system containing the ash basin. Flow and transport modeling indicated
private water wells within the model area remove only a small amount of
water from the overall hydrologic system (CAP Update Appendix G). The
expected flow zone for water supply wells is bedrock.
BC-1 is located northeast of the ash basin, in the vicinity of nearby
background wells BG-1S/D and BG-2S/D/BRA. Manganese concentrations of
background wells in this area range from 54.5 to 104 µg/L. Manganese
concentrations are not related to the ash basin at this upgradient, background
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locations based on flow directions and therefore concentrations are naturally
occurring.
3. Groundwater concentrations of boron is not detected in the vicinity of the
water supply wells and is only detected in bedrock monitoring wells at
locations within the compliance boundary, approximately over 3,000 feet
from the closest water supply well. Section 6.2.2.2 of the CAP Update provide
more discussion on water supply well analytical results.
4. All water supply well locations are depicted on Figure 5-7 of the CAP
Update.
5. Based on flow and transport modeling, groundwater from the ash basin does
not flow in the direction of water supply well BC-13 (SynTerra map ID BC-
2016). This homeowner has accepted a water treatment system. Duke Energy
has a performance monitoring plan in place, with details of the plan outlined
in the Permanent Water Supply Water Treatment Systems document. Duke
Energy will provide quarterly maintenance of the water treatment systems to
include replenishing expendables (salt for brine tank and neutralizer media)
and providing system checks and needed adjustments. Laboratory samples
of pre-treated and treated water will be collected annually to coincide with
system installation, unless there is evidence the system is not performing
properly, in which case samples will be collected more frequently.
6. Noted.
7. Piedmont background ranges for information purposes are included on Table
6-6 of the CAP Update.
DEQ Draft Comment 4d
4.4. "The reverse particle tracks did not reach the BCSS Compliance Boundary, indicating the
water supply wells located beyond the compliance boundary did not have ash- related impacts
(Figure 4-2). With this statement, whether the model account for water supply well pumping
influences and limitations of the flow model and of using particle track analysis on bedrock wells
should be discussed.
Response Summary 4d
Particle tracking is not available for Belews Creek. Flow and transport modeling
indicated private water wells within the model area remove only a small amount of
water from the overall hydrologic system (CAP Update Appendix G).
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DEQ Draft Comment 4e
4.5
1. Whether there are any intakes for drinking water supply from downstream of permitted
outfall 003 at the Dan River should be documented, and if there is any, what is the
distance to the intake for the closest intake?
2. Whether Belews Reservoir is a potential receptor or has been impacted by coal ash basin
should be further evaluated with additional sampling.
Response Summary 4e
1. No drinking water supply along the Dan River is identified downstream of
former Outfall 003. Outfall 003 is anticipated to be decommissioned with the
approval of the modification request to the NPDES permit.
2. Evaluation of potential impacts to Belews Reservoir from the ash basin is
included in Appendix K of the CAP Update.
Section Specific Draft Comments — Section 6
DEQ Draft Comment 6a
6.1.3. Information and summary on structural geology are good, but should be related to local
site conditions and, most importantly, to potential contaminant movement, which was not done.
Response Summary 6a
Noted. A robust conceptual site model (CSM) is included in CAP Update Section 5.0
with discussion of geological and hydrogeological setting and its relation to COI
migration.
DEQ Draft Comment 6b
6.1.4. "Results also indicate a significant composition of MnO from both the BCSS soils and
transition zone with ranges from 0.03% to 0.1% for soils and 0.05% to 0.14% for transition
zone." Why this composition at these levels are considered significant and its
context/implications should be discussed.
Response Summary 6b
Manganese can exist in multiple oxidation states ranging from Mn(II) to Mn(VII).
Under the Ex and pH conditions of the groundwater at the BCSS, Mn(II) is the
dominant oxidation state. It is noteworthy that several other Mn mineral phases are
possible including relatively common soil minerals such as hausmannite (Mn304),
manganite (MnOOH), birnessite (Mn02), and rhodochrosite (MnCO3). The common
soil minerals manganite, hausmannite, and birnessite are more likely to dominate
these systems (McKenzie, 1989). The minerals hausmannite, birnessite, and
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manganite have lower solubility and may lead to the dissolved manganese
concentrations being controlled by solubility if higher Ex conditions lead to
formation of these Mn(III) and Mn(IV) minerals.
Aqueous species of Mn(III) and Mn(IV) are not expected because trivalent Mn(III) is
unstable in aqueous systems and Mn(IV) is generally insoluble and will precipitate
from solution as MnO2(s) minerals birnessite or pyrolusite. The level of MnO
provides data and evidence of manganese precipitation occurring at Belews Creek.
DEQ Draft Comment 6c
6.1.6. A north -trending diabase dike is mapped in Figure 6-1. Whether it affects groundwater
flow and contaminant transport at the site should be evaluated and whether additional
assessment is needed to determine whether there is any effect should be also discussed.
Response Summary 6c
Noted. Based on analytical data from groundwater wells within the area of the
diabase dike and flow and transport modeling, the dike does not appear to
contribute to contaminant transport at the site. Instead, it is the natural subsurface
heterogeneities at the Site represented by three flow zones that distinguish the
interconnected groundwater system. And based on the orientations of lineaments
and open bedrock fractures at Belews Creek, horizontal groundwater flow within
the bedrock should occur approximately parallel to the hydraulic gradient, with no
preferential flow direction (CAP Updated Appendix F). Consistent with this
interpretation, the current groundwater flow model for BCSS does not simulate
plan -view anisotropy.
DEQ Draft Comment 6d
6.3. "A groundwater divide is located approximately along Pine Hall Road and to the west of the
ash basin along Middleton Loop Road." Data used to conclude this and whether there is any
uncertainty in its position and, if so, whether the uncertainty is an issue for modeling particle
tracks or transport should be discussed. Please note that the uncertainty does exist because it is
clear in the northwest area, groundwater has crossed Middleton Loop Road and flows northwest
from the ash basin.
Response Summary 6d
Data collected from the Site is the foundation for the flow and transport model
hydraulic parameters. Horizontal hydraulic conductivity and the horizontal to
vertical hydraulic conductivity anisotropy ratio are the main hydraulic parameters
in the model. The distribution of these parameters is based primarily on the model
hydrostratigraphy, with additional horizontal and vertical variation. Initial
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estimates of parameters were based on literature values, results of slug and core
tests, and simulations performed using a preliminary flow model. Flow and
transport model simulation all predict groundwater divides east, west and south of
the ash basin. From the flow and transport model (CAP Update Appendix G) The
red line in Figure 5-15 traces the groundwater divide around the ash basin. This
divide wraps around the west, south, east, and part of the northern side of the basin
area. On the inside of the divide, groundwater flows toward the ash basin (blue
arrows); outside of the divide, groundwater flows away from the ash basin.
Groundwater from the ash basin flows to the north and northwest near the dam and
the northwestern corner of the ash basin (orange arrows). Mobile COIs are
transported from the ash basin in this area.
The model supports that no groundwater divide currently exists northwest of the
ash basin but a notable result of the model simulation for year 2020 after the ash
basin is decanted, but before closure action construction is complete, is that the
natural groundwater divide along Middleton Loop Road, west of the ash basin, will
be re-established.
DEQ Draft Comment 6e
6.4
1. "Applying this equation to wells installed during the CSA activities yields the following
average horizontal hydraulic gradients (measured in feet/foot): Shallow wells: 0.009 ft/ft
i. Deep wells: 0.010 ft/ft
ii. Bedrock wells: 0.019 ft/ft
b. Generally horizontal gradients in the ash basin range from 0.002 to 0.004 ft/ft.
Horizontal gradients outside the waste boundary range from 0.006 to 0.035 ft/ft.
The hydraulic gradient south of the ash basin (GWA-12BR to MW-202BR) and
northwest of the dam (GWA-16S to GWA-11S) is likely due to the much higher
relief between the basin and downgradient areas." Generally, groundwater table
is parallel to ground surface; however, the average horizontal hydraulic gradient
in shallow wells appears to be much smaller than the surface slope, which needs to
be reevaluated. In addition, these results need to be related back to contaminant
transport and specific areas of interest. Moreover, what is more important than a
generalized "average" gradient across all shallow wells, for example, the gradient
across the shallow wells in northwest and north of the dam or other specific areas
of interest (i.e. along specific, "hot" flow paths) should be evaluated. The findings
should continually relate back to contamination and its specific movement. The
variations should be shown on a map with the transects that were used to
compute these.
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2. "Applying this calculation to wells installed during the CSA activities yields the
following average vertical hydraulic gradients (measured in feet/foot):
i. Shallow to Deep wells: 0.0195 ft/ft
ii. Deep to Bedrock wells: 0.0967 ft/ft
b. Based on review of the results, vertical gradients were mixed across the site but
with more locations showing downward gradient values. More upward values
were noted south of the ash basin and the topographic high of Pine Hall Road near
Belews Reservoir (GWA-12, GWA-23, and BG-3 locations), downgradient of the
basin near the Dan River (GWA-30 and GWA-31) and northeast of the basin
(BG-2)." It is easy to understand upward values measured downgradient of the
ash basin near the Dan River or in discharge areas. However, what resulted in
upward values measured in these upgradient wells, for example, at the
topographic high of Pine Hall Road near Belews Reservoir and northeast of the
basin should be discussed. In addition, this should be to related back to
contaminant transport and specific areas of interest as well. Whether these
findings bolster or undercut the conceptual model and whether the vertical
gradients in some locations are contrary to what is expected, for example, upward
potential vertical gradients were measured at BG-2 and BG-3 (Table 6-should be
discussed. As these two background well -clusters were thought to be drilled in
upgradient, an explanation should be given to help understand the case. What the
recharge source is, if not the ash basin, for each of these two areas need to be
discussed.
Response Summary 6e
1. Updated discussion of Site -wide groundwater occurrence and flow, including
horizontal gradients was provided in the 2018 CAMA Annual Interim
Monitoring Report. As noted above Site horizontal gradient are discussed in
more detail with relation to constituent transport in support of the CSM. A
key conclusion pertaining to horizontal gradients and groundwater flow
beneath the ash basin was ash pore water flow within stratified ash and the
shallow flow zone is generally horizontal with a small upward component of
flow. This horizontal flow across the basin limits the transport of COIs
downward in the ash basin.
2. Updated discussion of Site -wide groundwater occurrence and flow, including
vertical gradients was provided in the 2018 CAMA Annual Interim
Monitoring Report. As noted above Site vertical gradient are discussed in
more detail with relation to constituent transport in support of the CSM. Key
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conclusions pertaining to groundwater vertical gradients and flow beneath
the ash basin include:
• An upward vertical gradient is present at the upland edge of the ash
basin.
• Downward vertical gradients occur at the ash basin dam.
• Upward vertical gradients occur beyond the dam near groundwater
discharge zones.
DEQ Draft Comment 6f
6.5
1.Results of pumping tests conducted for Basis of Design (BOD) report should be integrated
into this section to estimate hydraulic conductivity for the area. (The BOD report was
provided by Duke Energy to satisfy a requirement set in the Settlement Agreement between
DEQ and Duke Energy signed on September 29, 2015, which requires accelerated
remediation to be implemented at sites that demonstrate off -site groundwater impacts.)
2. "Hydraulic conductivity values for wells screened in saprolite have a geometric mean of 2.65
x 10-4 cm/sec. Hydraulic conductivity values for wells screened in the transition zone have a
geometric mean of 7.91 x 10-5 cmisec. These measurements reflect the dynamic nature of the
transition zone, where hydrologic properties can be heavily influenced by the formation of
clays and other weathering by-products." It is true that hydraulic conductivity can be
heavily influenced by clay content of the formation because clay content will lower hydraulic
conductivity, therefore, please provide evidence showing the transition zone has higher clay
content and other weathering by-product than the shallow aquifer at this site as hydraulic
conductivity is lower in the transition zone than in the shallow aquifer, which is normally
not the case.
Response Summary 6f
1. Noted. Updated discussion of Site -wide groundwater occurrence and flow,
including horizontal and vertical gradients, and hydraulic conductivity,
seepage velocity was provided in the 2018 CAMA Annual Interim
Monitoring Report. Conductivity and seepage velocities were calculated for
different areas of the site on 2018 CAMA Annual Interim Monitoring Report
Table 3-1.
2. Updated evaluation of site hydraulic conductivities (CAP Update Appendix
G) supports that the transition zone does have a high conductivity than the
saprolite flow zone. Saprolite slug tests performed at the Site ranged from
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0.01 ft/d to 11 ft/d. Transition zone slug tests performed at the Site ranged
from 0.001 ft/d to 32 ft/d.
DEQ Draft Comment 6g
6.6
1. "Average groundwater seepage velocity results are summarized in Table 6-13" Please note
that most of values, as computed, are not even necessarily along flow paths (E.g. GWA-16S
to GWA-11S). In such cases, the values are completely erroneous. Also, why is the table
divided into multiple columns for ash, fill, M1, M2 for a single flow path and single flow
unit? Is one value (M1, e.g.) more representative than another for a given flow unit?
Seepage velocities need to be computed across specific areas of interest (e.g. along "hot" flow
paths). In addition, as indicated in the table, horizontal groundwater velocity is greater in
transition zone (TZ) than that in shallow zones M1 or M2. However, hydraulic
conductivity discussed above (6.5) is lower in transition zone than in shallow aquifer. Please
check whether there is anything wrong.
2. "... Primary (matrix) porosity is negligible". Please provide rationale and references for this
statement.
3. "Bedrock fractures encountered at BCSS tend to be isolated with low interconnectivity."
Please show the data and how this was determined.
4. "Groundwater flow in bedrock fractures is anisotropic and difficult to predict, and velocities
change as groundwater moves between fractures of varying orientations, gradients, pressure,
and size. For these reasons, bedrock groundwater velocities calculated using the seepage
velocity equation are not representative of actual site conditions and were not calculated." It
is true, but combining with aquifer testing results conducted in the northwest area for the
Interim Action Plan, bedrock groundwater velocity should be calculated, at least, for that
area.
Response Summary 6g
1. Updated evaluation and discussion of groundwater seepage velocities, that
used an integrated approach with flow and transport model data, was
included in the 2018 CAMA Annual Interim Monitoring Report Section 3.1.
Conductivity ranged from 0.05 to 4.0 feet per day (ft/day) for the shallow flow
zone, from 0.04 to 7.0 ft/day for the deep flow zone, and from 0.0005 to 0.7
ft/day for the bedrock flow zone. The horizontal groundwater seepage flow
velocity can be estimated using a modified form of the Darcy Equation. Using
the October 2018 groundwater elevation data, the a average horizontal
groundwater flow velocity in the vicinity of the ash basin was:
0.09 ft/day (34.5 ft/yr) in the shallow flow zone
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0.06 ft/day (21.4 ft/yr) in the deep flow zone
0.20 ft/day (71.3 ft/yr) in the bedrock flow zone
2. Matrix porosity and bulk density analysis was performed on bedrock cores
from screened intervals of groundwater monitoring wells north and
northwest of the ash basin. The reported matrix porosity values ranged from
0.50 to 0.73 percent, with an average of 0.62 percent. Bulk density ranged
from 2.80 to 2.84 with an average of 2.82 grams per cubic centimeter. These
values represent porosity from fractured zones in the bedrock. Generally
water flows almost entirely through the fractures in bedrock, this approach
requires a small effective porosity value (-0.01 or less) be used for the
transport calculations to compute a realistic pore velocity.
3. An evaluation of bedrock fracture characteristics and implications for
groundwater flow is included the Fractured Bedrock Evaluation report
(Appendix F of the CAP Update report). Deep bedrock borehole logging data
were used to characterize depths of flow zones to set targets for monitoring
well screen placement, hydraulic conductivity, the hydraulic apertures of
fractures and fracture spacing, and the in -situ orientations of bedrock
fractures. Results support that overall, calculated fracture apertures decrease
with increasing depth in the deep bedrock. The available data do not indicate
any predominant bedrock fracture sets at BCSS. Overall, a wide range of open
fracture dip angles and dip directions is observed supporting that there is low
interconnectivity between bedrock fractures.
4. Noted. Bedrock groundwater velocities were calculated for areas located
around the ash basin, including west of Structural Fill, south of the ash basin,
west of the ash basin, northwest of the ash basin and north of the ash basin.
Results of bedrock velocities are included on Table 3-1 in the 2018 CAMA
Annual Interim Monitoring Report.
DEQ Draft Comment 6h
6.7
1. "Constituents like cobalt and thallium have much higher Kd values, and will move at a
much slower velocity than groundwater as it sorbs onto surrounding soil. "Moving
velocities of constituents like cobalt and thallium also depend on other geochemical
conditions, such as pH and Eh, which should also be discussed.
2. "Continued vertical migration of groundwater is also evidenced by detected constituent
concentrations... " Please show data and wells, and discuss implications.
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3. "It should be noted that the fractured bedrock flow system is highly heterogeneous in nature
and high permeability zones with a geomean in situ horizontal conductivity of 0.00003
cm/sec observed, but these hydraulic.... etc...." Why a "geomean" rather than simple mean
or median was chosen to use needs to be discussed.
Response Summary 6h
1. Noted. Constituent transport based on geochemical conditions is discussed in
detail in the CAP Update geochemical model (Appendix H).
2. CAP Update Section 5.0 discusses groundwater flow and its relation to
constituent transport. North of the ash basin, velocity vectors (CAP Updated
Figure 5-5a) under pre -decanting conditions indicate groundwater velocity is
greatest (5.0 to 10.0 feet/day) beneath and immediately downstream of the
ash basin dam and flows predominantly north. The elevated constituent
concentrations found in groundwater near the dam is due to the operating
hydraulic head in the basin. The ponded water in the basin is the most
important factor contributing to constituent migration in groundwater.
3. Noted. Approaches to data evaluation for the CAP Updated relied on a
measure of central tendency analysis to capture the appropriate measure of
central tendency and determine if a dataset is best represented as an
arithmetic mean, geometric mean, or median.
DEQ Draft Comment 6i
6.9.2. "Relatively fewer northwest -trending lineaments, and more north -trending lineaments
(both being subparallel to regional diabase dike orientations) were identified on aerial
photography. Few west-northwest trending lineaments were identified, and northeast trending
lineaments identified on aerial photography are oriented primarily N25E.....etc." Please discuss
the implications for groundwater flow and contaminant transport in specific areas of interest.
The discussion should focus on "hot" flow paths and explain how any observed lineaments affect
the flow, transport, and risk.
Response Summary 6i
A lineament study is completed in the Fractured Bedrock Evaluation report
(Appendix F of the CAP Update report). Data indicate a predominant lineament
orientation of northeast -southwest, but with lineaments cross -cutting of various
orientations. The cross -cutting orientation supports limited interconnectivity in
bedrock fractures at Belews Creek.
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DEQ Draft Comment 6j
Cross -sections should show lithology described in the boring logs as cross -sections provided in
CSA Supplement 2 report.
Response Summary 6j
CAP Update cross sections were constructed using boring log lithology depth
contacts for wells included on the transect of the cross section. Cross sections were
developed using accurate vertical scaling to best represent lithology.
DEQ Draft Comment 6k
Additional cross -sections should be added: one from GWA-8 to GWA-19 as boron plume
expands to NW and another one perpendicular to Cross -Section A -A; from east to west through
the main dam of the ash basin because of transect B-B' is not perpendicular to A -A'.
Response Summary 6k
Cross section B-B' (Figure 6-3) in the CAP Update satisfies the request above to
include a cross section from east to west through the main dam of the ash basin.
DEQ Draft Comment 61
To determine groundwater flow directions better, all available monitoring wells (voluntary,
compliance, and groundwater assessment monitoring wells) in all three flow units must be
measured for water level in a single sampling event once and Figures 6-6 through 6-11 should be
revised with the measurements.
Response Summary 61
Noted. Update water level maps are included in the CAP Update as Figures 5-4a
through 5-4c.
DEQ Draft Comment 6m
For Table 6-12, please explain why the water level was not measured for each groundwater
elevation field filled with three dashes.
Response Summary 6m
Noted. CAP Update Table 5-1 provide water level measurements from a
comprehensive water level sweep of the Site, the dataset use to create water level
maps. Where a monitoring well has no water level recorded, the well was indicted
as "dry" in the field, meaning water level was below the dedicated pump elevation.
Dedicated pump elevations for wells indicated as "dry" are provided on Table 5-1
for information purposes.
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DEQ Draft Comment 6n
Table 6-13, horizontal gradients to NE-E from the ash basin should be also evaluated/determined
and listed in this Table.
Response Summary 6n
Noted. Horizontal gradients were calculated for several areas of interest around the
ash basin, including west of Structural Fill, south of the ash basin, west of the ash
basin, northwest of the ash basin and north of the ash basin. Results of horizontal
gradients are included on Table 3-1 in the 2018 CAMA Annual Interim Monitoring
Report.
DEQ Draft Comment 6o
Please provide a map showing where (wells) aquifer tests, including slug tests, were conducted
and testing results.
Response Summary 6o
An Ash Basin Pumping Test Report for Belews Creek was submitted to NCDEQ in
January 2019. This report included information on ash basin pumping test results,
with supporting figures and tables. Additionally, a hydraulic conductivity map
summarizing well locations, screen intervals and conductivity results based off slug
testing was submitted to NCDEQ in 2018.
Section Specific Draft Comments — Section 7
DEQ Draft Comment 7a
Figure 7-1 should also show and highlight soil concentrations exceeding PBTVs that exceed
POG PSRGS in unsaturated zone. In addition, a plane view map showing horizontal extent and
cross -sections showing vertical extent of contaminated soil should be provided.
Response Summary 7a
See response to DEQ Draft Comment 4. Data (Cap Update Table 6-2) indicate
unsaturated soil COI concentrations are generally consistent with background
concentrations or are less than regulatory screening values. In the few instances
where unsaturated soil COI concentrations are greater than PSRG POG standards or
background values, COI concentrations are within range of background dataset
concentrations or there are no mechanisms by which the COI could have been
transported from the ash basin to the unsaturated soils.
DEQ Draft Comment 7b
If contaminated soil were detected beyond the waste boundary, what is the source and how the
contaminants were transported away from the sources should be discussed.
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Response Summary 7b
Based on data evaluation, there are no mechanisms by which the COI could have
been transported from the ash basin to the unsaturated soils.
DEQ Draft Comment 7c
7.1. Soil contamination cleanup level should be either the site- PBTVs or POG PSRGs levels,
whichever are higher. Therefore, POG PSRG values for chloride, sulfate, and vanadium should
be calculated using the calculation in the PSRG table as these values have not be established.
Calculated values should be also shown on Table 7-2.
Response Summary 7c
Noted. Vanadium has an established PSRG POG value of 350 mg/kg. For
constituents lacking an established target concentration for soil remediation (i.e.
chloride and sulfate), the following equation was used in general accordance with
the references in Subchapter 02L. 0202 to calculate a POG value (CAP Updated Table
6-2). Resulting PSRG POG calculated values for chloride and sulfate were 938 mg/kg
and 1,438 mg/kg, respectively and are used on the soil analytical data table (CAP
Update Appendix C, Table 4)
DEQ Draft Comment 7d
7.2
1. "Soil sample test results indicate shallow impacts to the soil beneath the ash basin." To
what depth the impacts have reached and estimated volume with concentrations
exceeding PBTVs should be discussed and estimated.
2. "Concentrations of boron from wells beyond the compliance boundary did not exceed
PSRG values and only two locations exceeded the PBTV at GWA-6S and MW-200BR.
The majority of exceedances are sporadic and do not indicate the ash basin as a source of
soil impacts beyond the waste boundary." Please provide the basis for this statement and
explain as the ash basin is not the source, what will be the source.
3. "Elevated concentrations of chromium, iron, strontium and vanadium in areas
upgradient of the ash basin (GWA-6S, GWA-7S and GWA-8D) are not influenced by the
ash basin and associated with natural soil geochemistry. Saturation and other factors
may also affect constituent occurrence in the samples." This statement needs to be
supported by data and more detailed discussion. Please note that boron was detected in
GWA-8S.
Response Summary 7d
1. Soil beneath the ash basin is saturated. Affected saturated soil and rock is
considered a component of the groundwater flow system and can serve as a
source for groundwater COIs at the Site. The potential leaching and sorption
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of constituents in the saturated zone is included in the flow and transport and
geochemical model evaluations (CAP Updated Appendix G and H) by
continuously tracking the COI concentrations over time in the saprolite,
transition zone, and bedrock materials throughout the models.
2. Affected saturated soil and rock is considered a component of the
groundwater flow system and can serve as a source for groundwater COIs at
the Site. The potential leaching and sorption of constituents in the saturated
zone is included in the flow and transport and geochemical model
evaluations (Appendix G and H) by continuously tracking the COI
concentrations over time in the saprolite, transition zone, and bedrock
materials throughout the models. Unsaturated soil and rock is considered a
potential secondary source to groundwater. Constituents present in
unsaturated soil or partially saturated soil (vadose zone) have the potential to
leach into the groundwater system if exposed to favorable geochemical
conditions for chemical dissolution to occur. COIs in unsaturated soil are
discussed in Section 6.1 of the CAP Update report.
3. See DEQ Draft Comment 7d item 1 response summary
Section Specific Draft Comments — Section 8
DEQ Draft Comment 8a
This section is more a data summary. At least, what these data mean to water quality and to
human health and the environment and whether additional assessment or any corrective action
will be needed should be discussed.
Response Summary 8a
Noted.
DEQ Draft Comment 8b
8.1. Whether additional assessments are needed at S-6, 5-10, S-11, BCSW-007, BCSW- 008, and
BCSW-19 area should be discussed. It should also be discussed why for some areas only arsenic
or selenium was detected at concentrations exceeding the PBTVs and whether additional
assessments are needed.
Response Summary 8b
A Special Order by Consent (SOC) was issued to Duke Energy on July 19, 2018, to
address the elimination of seeps from Duke Energy's coal ash basins during the
separate and independent process of ash basin closure. Per the SOC seeps at Belews
Creek are subject to the monitoring and evaluation requirements contained in the
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SOC. Non-dispositioned seeps, where monitoring conducted has indicated the
presence of CCR affects, include: S-2, S-6, S-8, S-9, S-10, S-11, and S-18. Additional
seep characterization will be conducted post -ash basin decanting per the schedule
established by the SOC.
Section Specific Draft Comments — Section 9
DEQ Draft Comment 9a
"For this CSA, it is pertinent that a comparison with NCDENR Title 15A, Subchapter 02B.
Surface Water and Wetland Standards (2B) standards includes only sample results from named
surface waters. AOWs, wastewater and wastewater conveyances (effluent channels), and
industrial storm water are evaluated and regulated in accordance with the NPDES Program
administered by NCDEQ DWR." Why are only "named" surface waters? Are all AOWs or
unnamed streams and wetlands located on or near the site are considered effluent channels? If
not, then they will be jurisdictional waters, which should be evaluated with 2B standard. Please
also note that some of AOWs are identified as effluent channels in the anticipated permit which
has not been issued.
Response Summary 9a
Noted. An updated evaluation of surface waters at the site under current and future
conditions is include in CAP Update Appendix K. Seeps are regulated by the SOC.
Discussion of impact to seeps and potential corrective action measures are included
in Table 6-8
DEQ Draft Comment 9b
"Sample SW-DR-U has had contaminant concentrations reported as being greater than the
background surface water sample (and reported 2B surface water standard exceedances), which
suggests that there may be influence from the ash basin at this location along the Dan River.
However, contaminant concentrations detected in SW -DR- U were similar to those in sample
003, collected at the ash basin discharge structure flume in the designated effluent channel,
indicating that the location of sample SW-DR-U may be too close to the designated effluent
channel to reflect actual water quality in the Dan River." Please provide the data (sampling
results, such as boron, chloride, TDS, etc, from SW-DR-U and Outfall 003) and indicate the
distance (in feet) of the location from the Outfall.
Response Summary 9b
Sample results for SW-DR-U and 003 are provided in quarterly data submittals. The
distance from SW-DR-U and Outfall 003 is approximately 100 feet.
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DEQ Draft Comment 9c
Please state whether the additional surface water samples recently collected from the Dan River
were collected in accordance with DEQ Internal Technical Guidance: Evaluating Impacts to
Surface Water from Discharging Groundwater Plumes. Whether samples were collected at base
flow conditions should be also documented.
Response Summary 9c
Surface water samples collected from the Dan River and Belews Reservoir were
collected using methods consistent with NCDEQ guidance protocol. CAP Update
Appendix K provides detail of the surface water sample collection method for
surface water samples to assess groundwater -to -surface water impact.
Samples were collected from February 12-15, 2018 after a period of five days that
had 2.38 inches of measurable precipitation; however, there was 0.04 inches of
measureable precipitation during the four -day sampling event. The sampling event
occurred after a period of rapid river stage decline (gage height of 16 feet to gage
height of 3 feet).
Analytical results from samples in the Dan River and Belews Reservoir indicate
constituent concentrations less than applicable 02B criteria with the exception of
turbidity in Dan River samples (CAP Update Appendix K). Dan River turbidity
data trends decrease over the sampling period, therefore elevated turbidity is likely
a result of suspended solids from surface water runoff during the prior rainfall
event.
DEQ Draft Comment 9d
Additional assessment (for impacts of groundwater discharge on Belews Reservoir) as proposed
on the map submitted through October 4, 2017 email is needed to complete the CSA.
Response Summary 9d
Noted. The report titled Surface Water Evaluation to Assess 15A NCAC 02B .0200
Compliance for Implementation of Corrective Action Under 15A NCAC 02L .0106 W and
(l) was submitted to NCDEQ in March 2019.
DEQ Draft Comment 9e
9.1
1. "Analytical results with the dissolved phase concentrations greater than their associated
total reportable concentrations are not included in the assessment as they are considered
invalid." What caused the problem should be discussed and whether it is necessary to
resample should be discussed.
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2. "Sample results from the Dan River indicate that field parameters (turbidity, pH, and
DO), total concentrations of chloride, selenium, and TDS, dissolved concentrations
(cadmium and lead) have been reported as being greater than 2B values on one or two
occasions, but not consistently. " Need to state implications for 2L-2B conclusions.
Response Summary 9e
1. Noted. The Dan River was sampled in February 2018 for assessment of
groundwater -to -surface water impacts. Sample locations were near (generally
within 100 feet) surface water locations SW-DR-1, SW-DR-2, SW-DR-3, SW-DR-
UA, SW-DR-U, SW-DR-D, and SW-DR-4. The evaluation concluded that no
constituents with concentrations greater than 02B standards, with the exception
of turbidity (see CAP Update Appendix K for discussion), were detected in the
Dan River. Therefore, re -sampling is not recommended at this time.
2. An evaluation following DEQ's Internal Technical Guidance: Evaluating Impacts to
Surface Water from Discharging Groundwater Plumes was completed for surface
water bodies surrounding the Belews Creek station, including the Dan River and
Belews Reservoir. The evaluation confirmed that groundwater migration has not
resulted in constituent concentrations in the Dan River and Belews Reservoir
greater than applicable 15A NCAC 02B .0200 standards for: arsenic, barium,
beryllium, cadmium, chloride, chromium (hexavalent and trivalent), copper,
fluoride, lead, mercury, nickel, nitrate and nitrite, selenium, silver, sulfate, total
dissolved solids, thallium, total hardness, and zinc.
Section Specific Draft Comments — Section 10
DEQ Draft Comment 10a
10.1. BG-2D was missed but should also be listed in NCDEQ approved background well list.
Response Summary 10a
Noted.
DEQ Draft Comment 10b
10.2
1. Please discuss whether all monitoring wells are positioned properly (horizontally and
vertically) and a certain number of wells are installed along "hot" flow path.
2. The maximum, the average concentrations of each of COIs, estimated mass of
contaminants, and the volume of contaminated water should be summarized in a table.
3. "... The second quarter 2017 data is the primary dataset used for generating
isoconcentration maps and graphical representation of data such as Piper diagrams."
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What other data were used should be given in order for DEQ to evaluate those maps or
figures.
4. Each COI Isoconcentration map was well descripted, but how the site geochemical
conditions control the particular distribution was almost not interpreted.
5. For groundwater Isoconcentration maps, dash line should be used after contour lines
cross the waste boundary of Pine Hall Road Landfill and the ash basin from outside of the
waste boundary because of lack monitoring wells in the middle of the landfill or the basin
where is filled with water or saturated ash.
6. For Figures 10-17 and 10-18, as the Structure Fill is the potential source for
contaminants detected at GWA-8S and GWA-23S/D, isoconcentration line 700 µglL
should not be closed on the Structure Fill side.
7. Figures 10-17 and 10-18, isoconcentration 700 µglL contour line between GWA-11S
and GWA-IS in the shallow zone and near AB-1D in the deep zone do not appear to be
plotted properly. Why the lines sharply curve toward the basin?
8. Although as shown on Figures 10-5 to 10-64, the extent of groundwater migration from
the ash basin at concentrations greater than background and 2L extend downgradient of
the ash basin do not appear to reach the Dan River, whether 11,200 µglL of boron at
GSA-20SA (Fig. 10-17) would drop to 852 µglL at GWA-11S, and 184 µglL at GWA-
21S through dilution alone should be discussed. Whether the well positions or screened
intervals are measuring the flow path away from the hot spot should be discussed.
9. Please note that several constituents are above 2L in the area north of the ash basin,
beyond compliance boundary, such as Be (shallow and deep), Cr (shallow and deep), Co
(shallow), Fe (deep), Mn (shallow, deep, and BR), and Tl (shallow and deep), but it is
unclear why, since boron migration seemed to be limited to the area right around the
compliance wells. How site geochemical conditions resulted in or control these
occurrences should be discussed in the report.
10. High boron concentrations were detected in deep wells (e. g., 9890 µglL at GWA-20D
and 5420 µglL at GWA-27D), but no 2L exceedances were measured in their paired
bedrock wells. Whether these results are supported by site hydrogeologic conditions
and/or groundwater hydraulic property, such as vertical hydraulic gradient and
conductivity, should be discussed.
11. "Monitoring wells GWA-19BR, GWA-20BR, and GWA-27BR are located northwest of
the ash basin. These wells are grout contaminated (high pH) and their data is not
considered valid. The boron concentrations reported in these monitoring wells are similar
to the boron background concentration." As pH may affect the concentration of COIs and
the data is not considered valid, whether these wells (especially GWA-27BR, a
downgradient leading -edge bedrock well) need to be replaced or whether additional
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bedrock wells are needed should be discussed. Please also state boron concentrations of the
background and these wells to support the statement.
12. For monitoring wells that were not sampled in April 2017 sampling event, the most
recent sampling result or the historical average should be used in construction of these
isoconcentration maps. For example, Figure 10-19, none of bedrock wells in the
northwestern area was sampled, which makes for a very limited snapshot of CCR
movement in the bedrock unit. If the data from those bedrock wells cannot be justified due
to high pH values and it is necessary to replace the wells, please provide a proposal for
replacement of wells as soon as possible.
13. It seems that GWA-24S has never been sampled. It is time to evaluate whether the well
should be replaced.
14. To determine whether GWA-8S is soured by the ash basin or the Structural Fill,
additional well(s) appears to be needed if no data from DMW can be used.
15. Results from SFMW-2D, SFMW-ID (and paired shallow and bedrock wells) from
assessing Structure Fill should be provided. The data will help to evaluate the source of
boron measured in GWA-8 and GWA-23.
16. Please explain why BG-1S is considered a downgradient well on shallow groundwater
Isoconcentration maps. If it is an error, please correct it.
Response Summary 10b
1. Since the updated CSA submitted in October 2017,12 groundwater
monitoring wells have been installed to increase spatial horizontal and
vertical monitoring of groundwater quality around the source area.
Additional wells were installed for:
a. Characterization of shallow groundwater below the ash basin
b. Characterization of shallow, deep, and bedrock groundwater east of
the former constructed wetland treatment system
c. Delineation of groundwater water quality in each flow zone
downgradient of Parcel A and well pair GWA-21S/D
d. Delineation of groundwater quality in shallow and deep bedrock
below the ash basin dam
Additionally, a bedrock groundwater monitoring well with historically high pH
related to poor well construction was replaced in October 2018. Three
effectiveness monitoring plan flow paths consisting of 37 groundwater
monitoring wells, 10 new wells and 27 existing wells, are proposed to monitor
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areas where the groundwater plume is unstable during corrective action. It is
recommended that an additional three well clusters be installed within the ash
basin footprint post -closure to characterize groundwater below the ponded
portion of the ash basin.
2. Maximum and average concentrations of each COI for wells downgradient
and at or beyond the compliance boundary are included in the COI
management matrix Table 6-6 in the CAP Update. Volume of source material
is described in Section 6.0 of the CAP Update.
3. Noted. Data used for CAP Update isoconcentration and cross section maps is
included in Table 6-5 Means of Groundwater COIs in the CAP Update. A
measure of central tendency analysis of groundwater COI data (January 2018
to April 2019) was conducted and means were calculated to support the
analysis of groundwater conditions to provide a basis for defining the extent
of the COI migration at or beyond the compliance boundary. A measure of
central tendency analysis was completed to capture the appropriate measure
of central tendency (arithmetic mean, geometric mean, or median) for each
dataset of constituent concentrations.
Additionally, all Site data, including, but not limited to, groundwater, soil,
surface water and sediment, is included in Appendix C comprehensive
analytical data table.
4. Noted.
5. Noted.
6. Noted. Additional site assessment is ongoing to fully understand potential
affects to groundwater from the Structural Fill. Site assessment relating to the
Structural Fill will be documented in the Structural Fill CSA report.
7. Noted. Updated isoconcentration maps for boron shallow, deep, and bedrock
are included as CAP Update Figures 6-13a through 6-13c.
8. See DEQ Formal Comment 6 response summary.
9. Noted. The CAP Update discusses geochemical processes ability to stabilize
and limit certain constituent migration along flow paths and how it relates to
Site conditions in more detail. Discussion of COIs in the CAP Update focuses
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on the concept that each COI exhibits a unique geochemical behavior related
to the specific constituent partition coefficient (Kd), response to changing
geochemical parameters (i.e., pH and redox potential) and sorption capacity
of the soil and/or rock. Based on geochemical modeling:
a. Non -conservative, reactive COIs (i.e., arsenic and beryllium) will
remain in mineral phase assemblages that are stable under variable
Site conditions north and northwest of the basin, demonstrating
sorption as an effective attenuation mechanism.
b. Variably reactive COIs (e.g., cobalt and manganese) can exhibit
mobility depending on pore water geochemical conditions and
availability of sorption sites.
c. Non -reactive COIs (e.g., boron, chloride, and TDS) migrate in
groundwater as soluble species and are not strongly attenuated by
reactions with solids but are reduced in concentration with distance
primarily by physical processes such as mechanical mixing
(dispersion), dilution, and diffusion into less permeable zones.
Geochemical modeling (CAP Update Appendix H) discusses Site geochemical
conditions and the resulting mobility of constituents at the Site in detail.
10. See DEQ Formal Comment 14 response summary.
11. Sorption of boron to clay particles might occur, especially for groundwater
with slightly alkaline to alkaline pH values. Maximum boron sorption occurs
at pH values between 7.5 standard units (S.U.) and 10 S.U., then decreases at
pH values greater than 10 S.U. (EPRI 2005, ATSDR 2010). Grout contaminated
wells are characterized by having pH greater than 10 S.U., therefore boron
concentration results of wells with pH greater than 10 S.U. still provide an
accurate depiction the groundwater boron plume. Bedrock wells with pH
greater than 10 S.U. but with boron less than the 02L standard are not
recommended to be replaced at this time. If boron concentrations increase to
levels greater than the 02L standard, indicating groundwater at the location is
affected by the ash basin, well replacement would be considered. One
additional bedrock well CCR-13BR was installed northwest of the ash basin
and downgradient of GWA-21S/D. Boron is not detected at this location, and
vertically and horizontally delineates helps to delineate the boron plume
extent northwest of the ash basin. Because boron is less than the 02L standard
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in bedrock wells at or beyond the compliance boundary no additional
bedrock wells are recommended at this time. Boron concentrations of all
bedrock wells are included on CAP Update isoconcentration map Figure 6-
13c.
12. Noted. Data for wells with high pH have since been depicted on
isoconcentration maps and noted as such. See additional detail regarding
high pH and boron concentrations for bedrock wells at the Site in response
summary for item 11 of this comment.
13. GWA-24S is shallow well that has been historically dry. In October 2018 there
was sufficient water in GWA-24S to collect a sample. Sample results for
boron, sulfate and TDS were all below background values. Replacing the well
is not recommended because this location is not affected by groundwater by
the ash basin, and there is limited available water in the shallow flow zone in
this region of the Site.
14. Additional assessment of the Structural Fill, including six new wells installed,
was approved by DWM in June 2019 and conducted in August 2019. Results
of the additional assessment will be included in the CSA for the Structural
Fill, to be submitted in March 2020.
15. Data from SFMW-2D, SFMW-1D, and other recently installed wells around
the Structural Fill are provided to DEQ in a quarterly data submittal package.
16. Noted. BG-1S is upgradient, this has been corrected for all maps since CSA
Update submittal.
DEQ Draft Comment 10c
1. Please list or indicate COIs exceeding PBTVs that exceed 2LIIMACs in Table 10-3 or a
new table. The table should also show cleanup levels that are either PBTVs or 2LIIMACs,
whichever is higher.
2. Table 10-3 lists all COis developed for the site. As not all of COIs exist in all three flow
zones, please also list them for each flow zone or unit.
Response Summary 10c
1. Noted. CAP Update Table 6-5 provides a summary of COIs exceeding
background, 02L standards, IMAC values, or background, whichever is
greater for the area downgradient, in the direction of groundwater flow from
the source area.
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2. Noted. CAP Update Table 6-6 is a COI management approach that evaluates
COIs per flow zone base on multiple lines of evidence.
DEQ Draft Comment 10d
1. Please list COIs found in water supply wells, which exceed PBTVs or 2L/IMACs,
whichever is higher.
2. Each of water supply wells containing constituents exceeding 2L/IMACs or PBTVs,
whichever is higher, should be evaluated as potential receptors based on actual data,
piper -diagram, co-occurring constituents, proximity to CCRs, and topographic setting.
Conclusions must be drawn. Only in this way can potential supply well impacts be ruled
out and a CAP be properly developed.
Response Summary 10d
1. Ten of the 20 COIs identified in the CSA Update were present greater than
02L standards, IMAC values, or bedrock background, whichever is greater,
including: antimony, arsenic, hexavalent chromium, total chromium, cobalt,
iron, manganese, molybdenum, strontium and vanadium.
2. CAP Update Table 6-9 provides a water supply well -by -well summary of COI
exceedances and characterization. Lines of evidence, including water level
maps, vector velocity maps, isoconcentration maps, and flow and transport
modeling are used to support rationale for water supply well characterization
summary.
Section Specific Draft Comments — Section 11
DEQ Draft Comment 11a
11.1
1. "Monitoring wells installed for other regulatory programs have added additional details
about the orientation and extent of the downgradient plume and have helped refine an
understanding of the distribution of the plume." Does this mean or include CCR wells?
Please specify the programs.
2. "The boron concentration is non -detect in monitoring wells GWA-30S and GWA- 31S
which define the leading edge of the boron plume in the shallow flow layer. West of the
ash basin the boron concentrations are non -detect or less than the PBTV at the
compliance boundary." Please note that as discussed earlier, in the area to the west of
GWA-19S, boron has not been delineated. The last sample (41412017) detected boron at
2110 µg/L, but no well is located west of this point.
3. "Figures 11-1 through 11-3 depict concentration versus distance from thesource along
the plume centerline for COIs." Interpretations of what these figures mean/say should be
included.
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4. "Cross-section B-B' is a transect perpendicular to the plume centerline." This transect
does not appear to be perpendicular to the plume centerline or Cross- section A -A'. As
higher concentrations were detected at the base of and along the dam, a cross-section
along the base of the dam, from GWA-31 to GWA-22 should be added. In addition, please
evaluate as contaminants are also moving to northwest, whether another cross-section
from GWA-7 through the source to GWA-31 should be added.
5. "The well screens in the CAMA wells accurately monitor groundwater conditions and
impact to the shallow and deep flow layers." Please explain on what basis this statement
was made.
6. "Likewise, as it has been demonstrated with the installation of deeper bedrock well AB-
4BRD beneath the ash basin (AB-9BRD is grout contaminated and the data is not
usable), impact to the bedrock flow unit is confined to the top approximately 100-140 feet
of fractured bedrock." Please provide corroborating data, such as depth to water of the
well and sampling results from the well.
7. "Groundwater elevations are not available to calculate vertical gradients in the well
clusters installed near and along the base of the dam. " Please explain why and evaluate
whether additional wells are needed. Currently there are two well clusters: MW-
200S/D/BR and GWA-24S/D/BR, but GWA-24S has been always dry.
8. "A downward gradient exists to the east and west of the designated effluent channel
downgradient of the dam." Please provide well IDs and their head values and explain
what this implies for groundwater flow and transport.
9. "As groundwater and the plume migrate in the downgradient direction, unimpacted
groundwater enters the system from upgradient recharge areas to the west and east,
mitigating the concentration of some COIs (e.g., boron)." Please provide evidence and
data to support this statement.
10. "Further, it can be concluded that monitoring wells across the site are appropriately
placed and screened to the correct elevations to monitor groundwater quality." On what
basis? Please support this statement with rationale/data.
11. Boron concentration has been increasing in a significant number of wells, including
plume downgradient leading edge wells, such as GWAAS, GWA- 21S/D, GWA-195,
MW-103S/D, and MW-200S/BR, and wells, MW-4, OB-9, and MW2-7, at Pine Hall
Road Landfill. Whether these increases indicate the plumes still expanding should be
discussed thoroughly. In addition, boron concentration in GWA-8S is increasing, but
this well is considered an upgradient well for ash basin, which indicates the Structure
Fill being the source. As commented for Section 10, additional well(s) between GWA-8S
and the Structure Fill is needed to confirm this.
12. Figure 11-37, the footnote indicates that PBTV for deep flow layer is 55 uglL, while Table
10-2 indicates 13 uglL which is approved by DEQ.
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Response Summary 11a
1. Yes. CCR monitoring program has helped provide horizontal and vertical
extent and delineation in areas between the ash basin waste boundary and
ash basin compliance boundary.
2. Noted. GWA-31S/D provide accurate and sufficient horizontal and vertical
delineation downgradient of GWA-19SA based on groundwater flow
direction (CAP Update Figure 5-4a and 5-4b)
3. Noted. Where applicable concentration versus distance figures will describe
observations of COI distribution relative to the compliance boundary.
Updated concentration versus distance plots are included in CAP Update
Appendix I Monitored Natural Attenuation (MNA) for Inorganic
Constituents in Groundwater report as Figures 5-4 to 5-15.
4. Cross section B-B' (CAP Update Figure 6-3) in the CAP Update satisfies the
request above to include a cross section from east to west through the main
dam of the ash basin.
5. A total of 61 shallow groundwater monitoring wells, 68 deep groundwater
monitoring wells, and 29 bedrock groundwater monitoring are installed in
areas around the ash basin and PHR Landfill. Well location is typically
approved by DEQ through work plan review and comments. Wells are
installed and screened in saturated zones that exhibit at least 1 gallon per
minute of flow, and at depths where the screen would remain submerged.
Well construction and maintenance follows regulatory protocols (NCAC Title
15A Subchapter 02C).
There have been 30 groundwater monitoring sampling events at Belews
Creek. Results of these monitoring events have resulted in a very large
dataset that has informed the development of additional Site assessment and
this CAP Update. This dataset is a component of model inputs. Current
conditions simulations from the groundwater flow and transport and
geochemical models predict constituent distribution and geochemical
behavior that are consistent with empirical Site data (CAP Update Appendix
G and H).
6. Water level measurements are included in Table 5-1. Hydraulic gradients
from within the ash basin (CAP Update Section 5.1.2.3) and correlation
between saturated ash and groundwater (CAP Update Section 6.1.1.5)
discusses how layered ash within the basin has resulted in relatively low
vertical hydraulic conductivity, the upward flow of water into the basin and
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layered ash within the basin minimizes downward vertical constituent
migration to groundwater immediately underlying saturated ash in the
upgradient ends of the basin where AB-9BRD and AB-4BRD are located. CAP
Update Table 6-1 summarizes boron concentrations from groundwater below
the ash basin to support this component of the conceptual site model.
7. Shallow groundwater monitoring well GWA-24S has typically been a dry
well since well installation. There was sufficient water to sample the well
during Fall 2018, however vertical gradients are calculated using April 2019
groundwater elevations. Calculation of a downward vertical gradient
between the deep and bedrock flow zones was approximately 0.2 ft/ft
between the deep and bedrock flow zones. The gradient between the shallow
and deep flow zone, if available shallow water, would likely be of similar
direction and magnitude.
Bedrock groundwater monitoring MW-200BR is a free flowing artesian well,
requiring a pressure gage to be installed on the well head for accurate water
level readings via pressure conversion. Calculation of an upward vertical
gradient between the shallow flow zone (MW-200S) and the bedrock flow
zone was approximately -0.3 ft/ft.
8. Site comprehensive groundwater level measurements were conducted in
April 2019. Data from field measurements are reported on CAP Update Table
5-1. Water level field measurements provide data for preparing water level
maps and determining groundwater flow directions at the Site.
9. Based on analytical data from areas northeast and northwest of the ash basin
and groundwater flow direction, there are areas of that represent unaffected
groundwater, such as GWA-31S/D and GWA-2S/D that contribute to
groundwater flow downgradient of the ash basin.
10. See DEQ Draft Comment 11a item 5 response summary.
11. See DEQ Draft Comment 3 response summary.
12. Noted.
DEQ Draft Comment 11b
11.2. "Plume chemical characterization is detailed below for each COI..." This subsection is
good information as a very broad, site wide overview and summary, less site specific except
concentrations, but should be further discussed for CAP development for specific areas of
concern. For instance, "Despite the low apparent mobilization percentage, manganese can be
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detected in relatively high concentrations in ash pore water." Why and what this mean
regarding site remediation should be explained.
Response Summary 11b
Noted. Geochemical modeling (CAP Update Appendix H) provides evaluation
using Site data and discussion of each COI in regard to groundwater remediation.
DEQ Draft Comment 11c
11.3
1. "Additional metal oxy-hydroxide phases of iron (HFO) and aluminum (HAO) data are
needed to support geochemical modeling conducted as part of the CAP. Soil and rock
samples will be collected from previously installed borings or from additionally drilled
boreholes along the primary groundwater flow transects... " Based on the data presented
in this report, DEQ agrees to collect additional metal oxy-hydroxide phases of iron
(HFO) and aluminum (HAO) data as proposed in this section to refine geochemical
modeling conducted as part of the CAP, particularly in downgradient locations
northwest of the ash basin. Please provide a map and cross section showing both existing
and proposed sample locations and depths.
2. "To help determine potential routes of exposure and receptors related to the ash
management areas, additional surface water samples will be collected from Belews
Reservoir and the Dan River near the stream/river bank most likely to be impacted by
potentially contaminated groundwater discharge... " Until this pending assessment is
done, the CSA is still incomplete. Please provide this office a proposed schedule if the
proposed samples have not been collected; otherwise, please submit the sampling results
as soon as possible.
Response Summary 11c
1. Locations of HFO samples collected at the BCSS are identified on Figure 1 of
the geochemical modeling report (CAP Update Appendix H).
2. A groundwater (02L) to surface water (02B) mixing model for the surface
waters that could be potentially affected by future groundwater plume
migration has been conducted and provided in Appendix K of the CAP
Update report.
Section Specific Draft Comments — Section 12
DEQ Draft Comment 12a
"As previously noted, AOW locations are outside the scope of this risk assessment because
AOWs, wastewater, and wastewater conveyances (effluent channels) are permitted under the
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NPDES Program administered by NCDEQ DWR."AOW locations that are not considered
effluent channels should be assessed and discussed.
Response Summary 12a
A Special Order by Consent (SOC) was issued to Duke Energy on July 19, 2018, to
address the elimination of seeps from Duke Energy's coal ash basins during the
separate and independent process of ash basin closure. The locations included in the
SOC are subject to the monitoring and evaluation requirements contained in the
SOC. Attachment A to the SOC identifies the following seeps:
• Non -constructed seeps to be monitored — S-2, S-6, S-8, S-9, and S-10
• Non -constructed seeps dispositioned — S-1, S-3, S-4, S-5, S-7, S-12, S-13, S-14,
S-15, and S-16
• Constructed seep to be monitored per terms of the NPDES Permit S-11 [non -
constructed seep S-18 flow to a portion of the NPDES wastewater treatment
system (i.e. seep S-11) and is monitored per terms of the NPDES Permit]
For seeps that have the potential to not be fully dispositioned post -decanting
include: S-2, S-6, S-8, S-9, S-10, S-11, and S-18, CAP Update Table 6-8 provides a
summary of seep general location, approximate flow rate, and potential correction
action strategies for seep locations.
DEQ Draft Comment 12b
"New maximum concentrations of antimony, arsenic, beryllium, hexavalent chromium, nickel,
and selenium were detected that exceeded human health risk screening values; however, no
values exceeded respective site -specific RBCs. There is no evidence these constituents pose
human health risks from groundwater exposure." Please provide summary tables comparing new
maximum concentrations of constituents of potential concern (COPCs) to the site -specific
human health risk -based concentrations (RBCs) for human health and ecological receptors.
Response Summary 12b
An update to the BCSS human health and ecological risk assessment is included in
CAP Update Appendix E.
DEQ Draft Comment 12c
"The sample location SW-DR-D is adjacent to NPDES outfall 003 discharging ash sluice and
FGD wastewater and is not representative of Dan River conditions downstream of plant
operations." "NPDES outfall 003 discharging ash sluice and FGD wastewater" should be
revised as "NPDES outfall 003 discharging wastewater from the ash basin which ash sluice and
FGD wastewater discharge to".
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CSA Update Report Comments and Responses December 2019
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Response Summary 12c
Noted.
DEQ Draft Comment 12d
The ecological risk assessment reported in CAP 2 report indicated that risk estimates for several
COPCs are above risk targets for some water dependent mammals and birds, if and where these
species are present at the BCSS site. However, only cobalt was evaluated in this report. Each of
COPCs identified in CAP 2 report above risk targets should be discussed in this report.
Response Summary 12d
Noted. An update to the BCSS human health and ecological risk assessment is
included in CAP Update Appendix E.
DEQ Draft Comment 12e
A table summarizing surface water quality sampling results and showing LOAEL, ADD, TRV
should be given in this section as LOAEL, ADD, and TRV are used to evaluate whether surface
waters risk the ecological receptors.
Response Summary 12e
An update to the BCSS ecological risk assessment is included in CAP Update
Appendix E. Attachment 8 of the risk assessment contains a summary of the
LOAEL, ADD and TRV results.
DEQ Draft Comment 12f
To evaluate whether coal ash has impacted or has any potential risk for any water supply wells
and whether the well water has any risk for human consumption, in addition to 2L/IMAC and
DHHS screening levels, EPA MCL and tap water Regional Screening Levels (RSL) were also
used. Therefore, to support the statement and conclusion, DHHS screening levels, MCL, and
RSL should be added into Table 4-3 and referred in this section, or provide a concise table
including these referenced levels in this section.
Response Summary 12f
An update to the BCSS human health and ecological risk assessment is included in
CAP Update Appendix E. Attachment 2 of the risk assessment contains the
screening assessment for site groundwater. Section 5.4 and 6.3 of the CAP Update
report describes the evaluation of potential impacts to water supply wells. Results
from surveys conducted to identify potential receptors for groundwater, including
public and private water supply wells and surface water features within a 0.5-mile
radius of the ash basin compliance boundary are summarized in the CAP Update.
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
DEQ Draft Comment 12g
"Based on review and analysis of groundwater and surface water data, there is no evidence of
risks to humans and wildlife at BCSS attributed to CCR constituent migration in groundwater
from the ash basins. This update to the human health and ecological risk assessment supports a
proposed NCDEQ Risk Classification of "Low"." As commented earlier, site risk classification
should be classified in accordance with CAMA and also depends on the potential risk that
depends on how the ash basin is closed and how the contaminated soil and groundwater are
addressed. Updated groundwater fate and transport modeling results to be presented in the CAP
will help as well.
Response Summary 12g
Noted. Pursuant to G.S. Section 130A-309.213(d)(1) a November 13, 2018 letter from
NCDEQ to Duke Energy, documented the classification of the CCR surface
impoundment at the Site as low -risk (CAP Update). The letter cited that Duke
Energy has "established permanent water supplies Appendix A as required by G.S.
Section 130A-309.211(cl)" and has "rectified any deficiencies identified by, and
otherwise complied with the requirements of, any dam safety order issued by the
Environmental Management Commission... pursuant to G.S. Section 143-215.32."
Section Specific Draft Comments — Section 13
DEQ Draft Comment 13a
All COIs should be modeled unless rationales are given.
Response Summary 13a
Noted. All COIs are modeled using flow and transport of geochemical modeling
(CAP Update Appendix G and H).
DEQ Draft Comment 13b
If a PBTV for a constituent is higher than 2LIIMAC, whether the constituent concentration
exceeds the PBTV at the compliance boundary or receptors should be also modeled.
Response Summary 13b
Noted. Background values are considered in both the flow and transport and
geochemical model.
DEQ Draft Comment 13c
Whether a GW/SW mixing model should be updated and included in the CAP should be
discussed in this report.
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CSA Update Report Comments and Responses December 2019
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Response Summary 13c
A groundwater (02L) to surface water (02B) mixing model for surface waters that
could be potentially affected by future groundwater plume migration has been
conducted and provided in Appendix K of the CAP Update report.
DEQ Draft Comment 13d
Because the summary is too general and the models are still being updated, our review cannot be
completed until updated modeling reports are received.
Response Summary 13d
Noted. Completed flow and transport and geochemical modeling reports are
included in CAP Update Appendix G and H.
DEQ Draft Comment 13e
It should be discussed in the updated flow modeling report that whether the uncertainty in model
parameters and predictions can be quantified, and therefore, the error in model predictions can be
evaluated.
Response Summary 13e
Flow and transport model calibration and sensitivity analysis is discussed in Section
5.0 of the Updated Groundwater Flow and Transport Modeling Report (CAP
Update Appendix G). Hydraulic conductivity is calibrated in the flow model and the
initial specified source zone concentrations and Kd are calibrated in the transport
model. Sensitivity analyses are conducted for groundwater recharge, hydraulic
conductivity, and Kd. The normalized root mean squared error is used to quantify
the error when comparing the computed values and observed values for both the
flow and transport
models. DEQ Draft Comment 13f
13.3. 'Based on the available data for the upstream and downstream Belews Reservoir samples
and the known COI distribution in groundwater the BCSS ash basin is not the source of 2B
exceedances in Belews Reservoir." This statement is not conclusive. Please note that SW-BL-D is
too far from the bank to assess 2L/2B violations. In addition, the seep sample location, S-6 near
Belews Reservoir, was consistently detected boron above 2L. To determine whether there is any
2B exceedances in Belews Reservoir and whether the ash basin is the source, additional sampling
is needed.
Response Summary 13f
Additional sampling to assess groundwater (02L) to surface water (02B) interaction
has been conducted and provided in Appendix K of the CAP Update report.
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Section Specific Draft Comments — Section 14
DEQ Draft Comment 14a
"The ash basin pore water was determined to be a source of impact to groundwater." This
statement not is not quite right, but should be consistent with Section 3. Section 3 indicated:
"For the BCSS site, sources include the ash basin, Pine Hall Road Landfill, and the former
chemical pond."
Response Summary 14a
Noted. While the ash basin and Pine Hall Road Landfill are the source units, it is the
waste material within the unit's waste boundary and COIs leaching from the waste
material to the ponded water in the basin that are the factors contributing to
constituent migration in groundwater.
DEQ Draft Comment 14b
"Some COIs, such as boron, readily solubilize and migrate with minimal retention. In contrast,
some COIs such as arsenic readily adsorb to aquifer materials, do not readily solubilize, and thus
are relatively immobile. "As summarize assessment results, all COIs that are readily mobile and
all COIs are relatively immobile should be listed rather than boron and arsenic only.
Response Summary 14b
Noted. COIs discussed in the CAP Update are frequently evaluated in subsets based
on constituent properties (i.e. mobility) or characteristics common to various
groupings as presented at the geochemical modeling report (CAP Update, Appendix
H). See response summary for DEQ Draft Comment 10b item 9 for COI groupings
and constituent properties. Belews Creek COI groupings include:
Non -conservative Variable
• Arsenic • Cobalt
• Barium • Chromium (VI)
• Beryllium • Iron
• Cadmium • Manganese
• Chromium (Total) • Selenium
• Strontium • Sulfate
• Thallium • Molybdenum
• Vanadium
Conservative
• Antimony
• Boron
• Chloride
• Total Dissolved Solids
(TDS)
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
DEQ Draft Comment 14c
"Boron is also detected in the bedrock flow layer at monitoring well OB-9, located
north/northwest of the Pine Hall Road Landfill at a concentration greater than the PBTV and
less than the 2L standard." Based on the information provided in Section 6, OB-9 is a deep well
and the concentration of boron from this well is greater than 2L. Please check and correct
statement as necessary.
Response Summary 14c
Noted. OB-9 is a deep well and represented as deep well on CAP Update figures.
DEQ Draft Comment 14d
"Boron results exceed the 2L standard beneath the Pine Hall Road Landfill in the deep flow
layer, but are non -detect at the compliance boundary." This statement may not be true in
downgradient or to the north where the plume migrated outside of the CB and comingled to the
plume caused from the ash basin.
Response Summary 14d
Agreed, comingled plumes between the ash basin and the PHR Landfill are present
within the ash basin and landfill compliance boundaries, particularly in the shallow
flow zone (CAP Update Figure 6-13a).
Groundwater sampling data indicate constituents similar to COIs identified from
CAMA groundwater monitoring of the ash basin (e.g. boron and chloride) are
present in groundwater beneath and within a limited horizontal extent of the landfill
footprint. All groundwater COI migration from the landfill occurs within with the
landfill compliance boundary, with the exception of some COI migration north of
the landfill, within the ash basin compliance boundary. Groundwater COI migration
from the landfill is predicted to not migrate beyond the landfill compliance
boundary in the future. Groundwater from the closed landfill and the ash basin
primarily flows north, where corrective action is planned.
DEQ Draft Comment 14e
Legends of Figures 14-97 to 14-99 indicate: "Wetland and stream boundaries provided by
AMEC Foster Wheeler. Note these do not appear to be inclusive of all the boundaries as shown in
the AMEC Forster Wheeler NRTR Belews Creek Report." This sounds like that these figures do
not include all surface water bodies. Please check it further to see whether this is what the
statement means. If yes, all related figures need to be revised to include all jurisdictional waters.
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
Response Summary 14e
Noted. Wetland and stream boundaries provided by AMEC Foster Wheeler that are
within 0.5 miles of the ash basin compliance boundary are depicted on the CAP
Update figures.
DEQ Draft Comment 14f
"The bedrock aquifer is generally the source of water for supply wells in the area. As outlined
above, the bedrock aquifer has not been impacted by CCR constituent migration from the ash
basin with the exception of a grout contaminated well beneath the ash basin main dam." As
bedrock wells were contaminated with well grout material, whether additional wells or
assessment is needed should be discussed.
Response Summary 14f
See DEQ Draft Comment 10b item 11 response summary.
DEQ Draft Comment 14g
The leading edge of the boron plume in the shallow flow zone in NW of the ash basin, GWA-19S
area, has not been delineated and should be addressed before moving to the CAP.
Response Summary 14g
To address further delineation of COI plumes downgradient of the GWA-21S
cluster, an additional well cluster, CCR-13S/D/BR, was installed approximate to the
S-4 AOW location in October 2018 (see Figure 1-2, CAP Update report). Boron is
non -detect at CCR-13S, delineating the leading edge of the northwest boron plume
between GWA-21S and CR-13S.
DEQ Draft Comment 14h
From Figure 14-98, it looks like that S-2-D, S-3-D, and S-5-D were collected from the Dan
River; however, the results are not listed in Table 2, Surface Water Results, of Appendix B, but
in Table 3, AOW and WW Results. If they were not collected from the Dan River, please correct
the figure; otherwise, list them in Table 2, Surface Water Results.
Response Summary 14h
Noted. Sample results for S-2-D, S-3-D, S-5-D, and other surface water samples
collected from the Dan River are included in CAP Update Appendix C, Table 2.
DEQ Draft Comment 14i
As indicated earlier (comment on Section 11), concentrations of some of COIs, including boron
in some downgradient wells, such as GWA-19S, are still increasing. The number of wells in
which concentrations of Ba, B, Cd, Cl, and Sr were increasing is more than the number of wells
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
in which the concentrations were decreasing. Whether plumes are still expanding needs to be
evaluated and conclusions need to be made.
Response Summary 14i
See DEQ Draft Comment 7 response summary.
Section Specific Draft Comments — Section 15
DEQ Draft Comment 15a
15.1. "The horizontal and vertical extent of exceedances has been defined (Figure ES-1)
sufficiently for preparation of the CAP." Please note that no vertical extent shown on Figure ES-
1. What the text says should be consistent with what the figure shows. Furthermore, additional
delineation west of GWA-19SA appears to be needed.
Response Summary 15a
Noted. Vertical extent of constituents in groundwater is defined in cross section
figures included in the CAP Update (Figures 6-6a through 6-6c and Figures 6-22a
through 6-22c). Groundwater monitoring wells GWA-31SID are located northwest of
GWA-19SA, and provide both horizontal and vertical delineation of the
groundwater plume.
DEQ Draft Comment 15b
15.2
1. "Assessment findings determined that pore water in the ash basin is the primary source
of impact to groundwater. As previously discussed, residual concentrations of arsenic,
selenium and strontium in soil beneath the ash basin may also represent a secondary
source. " Does this statement mean that the CCR or coal ash that is the source of pore
water is not the source of groundwater contamination? The CCR should be the source as
discussed earlier. Please clarify.
2. "These topographic divides generally function as groundwater divides, although
groundwater flow across topographic divides may be possible based on hydraulic head
conditions from the ash basin and the existence of preferential flow paths within the
shallow and/or deep flow layers." Based on the occurrence groundwater plumes, such as
boron, this statement should be revised because the plume has crossed (not "may be
possible") Middleton Loop Road, a topographic divide.
3. "... As outlined above, the bedrock aquifer has not been impacted by CCR constituent
migration from the ash basin." Again, this statement is inconclusive because no wells
including bedrock wells were installed in the middle of the ash basin due to safety
concern. In addition, GWA-27BR is grout contaminated and pH is consistently high.
Although no boron was not detected but data is considered invalid. Therefore, the vertical
extent in this area may have not be properly determined, which need to be discussed.
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CSA Update Report Comments and Responses December 2019
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Response Summary 15b
1. Affected saturated soil and rock beneath the ash basin is considered a
component of the groundwater flow system and can serve as a source for
groundwater COIs at the Site. The potential leaching and sorption of
constituents in the saturated zone is included in the flow and transport and
geochemical model evaluations (Appendix G and H) by continuously
tracking the COI concentrations over time in the saprolite, transition zone,
and bedrock materials throughout the models. Based on the CSM presented
in CAP Update Section 5.0 the ponded water in the basin is the most
important factor contributing to constituent migration in groundwater. The
ash basin and PHR Landfill were constructed within a former perennial
stream valley in the Piedmont of North Carolina, and exhibit limited
horizontal and vertical constituent migration, with the predominant area of
migration occurring near and downgradient of the ash basin dam.
2. Noted. A groundwater divide is located east of the ash basin and PHR
Landfill represented by a topographical ridge approximated by Pine Hall
Road and a topographical ridge west of the ash basin and PHR Landfill along
Middleton Loop. Another groundwater divide exists north of the ash basin
along a ridgeline that extends from the east of the basin dam toward the
northeast. An exception is a localized area near the northwest corner of the
ash basin, where the hydraulic head created by the operational water level in
the ash basin causes groundwater from the ash basin to flow beyond a thin
pre -basin topographical divide along Middleton Loop.
3. See DEQ Draft Comment 8 response summary
DEQ Draft Comment 15c
15.4
1. "Constituent concentrations in bedrock groundwater directly downgradient of the ash
basin are less than 2L with the exception of manganese, which appears to be due to
geochemical conditions. " Although it has been mentioned several times in the report that
manganese concentrations reported in bedrock groundwater are likely due to natural
geochemical conditions, what geochemical conditions and how the conditions affect the
distribution of manganese were not discussed but is expected.
2. "Monitoring wells GWA-19BR, GWA-20BR, and GWA-27BR are located northwest of
the ash basin. These wells are grout contaminated (high pH) and their data is not
considered valid. The boron concentrations reported in these monitoring wells are similar
to the boron background concentration." This statement is simply from Section 10, which
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CSA Update Report Comments and Responses December 2019
Duke Energy Carolinas, LLC — Belews Creek Steam Station SynTerra
is neither a conclusion nor a recommendation. As commented earlier, since pH has been
consistently high in GWA-27BR, whether the well should be replaced to further delineate
the vertical extent in this area should be discussed.
Response Summary 15c
1. Manganese sorption occurs through both surface complexation on ferrihydite
and ion exchange with clay minerals. Therefore, sorption of manganese can
be strongly influenced by pH (surface complexation) and the presence of
competing divalent ions (ion exchange). The high variability in Site
manganese Kd values in the pH range 5-7 is primarily due to competition
with other diavalent ions (e.g., Ca+2, Mg+2) for ion exchange sites. Simulation
of manganese aqueous concentrations along the north and northwest
transects are in agreement with the emperical Site data. In particular, the
measured data in the north bedrock transect that falls below the 02L standard
at the compliance boundary is accurately simulated after 10 shifts. Further
discussion of geochemical Site conditions and manganese mobility are
included in CAP Update Appendix H.
2. See DEQ Formal Comment 10 response summary.
DEQ Draft Comment 15d
15.4
"It is assumed a source control measure of either capping the ash basin and
minimizing infiltration, or excavation, or a combination of the two, will be designed
following completion of the risk classification process. " At this phase, the risk
classification process should be completed. As it has not been done, please make a
clear recommendation or plan for completion.
2. Comments on "The following Site conditions significantly limit the effectiveness of a
number of possible technologies. "
o "The area that may require groundwater remediation is between the toe of the
basin dam and the compliance boundary to the north." Please specify the
limitations this condition will propose for remediation. In addition, this area
should be one of the areas..., not the area.
o "The COIs that may potentially need to be addressed are predominantly found
in the downgradient bedrock formations." Does this mean bedrock aquifer?
If yes, this statement does not appear to be consistent with isoconcentration
maps and cross -sections. For instance, boron has not been detected at
concentration above 2L standard in any bedrock wells so far. Please list COIs,
bedrock wells, and concentrations to support this statement.
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CSA Update Report Comments and Responses December 2019
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o "Groundwater flow is primarily through the upper fractured bedrock unit and
...." There are three flow units. Groundwater hydraulic data and plume
information from this report does not support this statement. For instance,
boron migrated farther in shallow unit than in other two units.
3. Groundwater extraction combine with source control and MNA is to be proposed in
the updated CAP, which appears to be reasonable. Real challenge is probably source
control. Details are expected in the CAP.
Response Summary 15d
1. See DEQ Draft Comment 12g response summary.
2. Noted. Section 6.4 and Table 6-12 of the CAP Update report provides a
review of remedial technology screening for the Site. Three potential
corrective action remedial alternatives are evaluated using screening criteria.
One criteria is technical and logistical feasibility that considers limitations the
alternative might propose.
Updated discussion of the conceptual site model and distribution of COIs in
each flow zone are included in CAP Update Section. As described in Section
6.1.3 a COI management process was developed by Duke Energy at the
request of NCDEQ to gain understanding of the COI behavior and
distribution in groundwater and to aid in selection of the appropriate
remedial approach.
3. Noted. Source control activities completed or in -progress as interim response
actions are discussed in CAP Update Section 6.1. Ash basin closure is detailed
in a separate document prepared by AECOM (Ash Basin Closure Plan
Report, Belews Creek Steam Station AECOM 2019).
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