Duke Energy response to DEQ letter 02_10_2020 SW Evaluation Comments

DUKE 410 S. Wilmington Street.
Raleigh, NC 27601
t__73 ENERGY® Mailing Address
Mail Code NC 15
Raleigh, NC 27601
919-546-7863
March 5, 2020
Mr. Steven Lanter
North Carolina Department of Environmental Quality
Division of Water Resources
1636 Mail Service Center
Raleigh, NC 27699-1636
Subject: Response to North Carolina Department of Environmental Quality letter dated
February 10, 2020 — Surface Water Evaluation Comments
Dear Mr. Lanter:
Duke Energy is in receipt of the above -referenced letter from the North Carolina Department of
Environmental Quality (NCDEQ) which provided comments regarding surface water evaluation reports.
Duke Energy submitted these reports to NCDEQ between February 28, 2017 through November 22, 2019
for the Allen Steam Station, Belews Creek Steam Station, Dan River Combined Cycle Station, James E.
Rogers Energy Complex (Cliffside), HF Lee Energy Complex, Marshall Steam Station, Mayo Steam Electric
Plant, Riverbend Steam Station and Roxboro Steam Electric Plant.
NCDEQ had 'no comments at this time' regarding reports submitted for Allen Steam Station, James E.
Rogers Energy Complex (Cliffside), HF Lee Energy Complex, Marshall Steam Station, Mayo Steam Electric
Plant, and Roxboro Steam Electric Plant. The above -referenced letter included comments on the reports
submitted for Belews Creek Steam Station, Dan River Combined Cycle Station and Riverbend Steam
Station. A summary of NCDEQ comments provided in the February 10, 2020, letter and corresponding
responses are provided below.
Belews Creek Steam Station
The Belews Creek Surface Water Evaluation Report was originally submitted to NCDEQ on March 25,
2019. A revised Surface Water Evaluation Report was submitted as Appendix K in the Belews Creek
Corrective Action Plan (CAP) Update on December 31, 2019. The evaluation included results from
surface water sampling that occurred in the Dan River and Belews Reservoir during February 12 through
February 15, 2018.
Comment:
DEQ received the Surface Water Evaluation Report on March 25, 2019.
Response:
Acknowledged
Comment:
The report states. "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 report also states, "The sampling event occurred
after a period of rapid river stage decline (gage height of 16 feet to gage height of 3 feet)." DEQ's

March 5, 2020
Mr. Lanter Letter
Internal Technical Guidance: Evaluating Impacts to Surface Water from Discharging Groundwater
Plumes dated October 31, 2017 states, "When practical, sampling should be conducted at low or base
flow conditions." Therefore, DEQ requests that Duke Energy resample the surface water using DEQ's
above referenced guidance during a period of low or base flow conditions.
Response:
Surface water sample collection followed guidance provided by NCDEQ, such that surface water
samples from the Dan River and Belews Reservoir were collected "near bank" at locations that
minimize influence from flow conditions "...to avoid lateral mixing that can dilute the sample."
However, at the time surface water sample locations were proposed (early 2018) to complete the
surface water evaluation, groundwater affected by the ash basin had not been completely
delineated, and the Dan River and Belews Reservoir were tentatively identified as potential
receptors for groundwater migration from the ash basin.
During the time since surface water sampling was conducted in 2018, extensive assessment
activities have been completed to further characterize groundwater flow paths and groundwater
quality downgradient of the ash basin. Assessment activities include, but are not limited to:
• Installation of additional groundwater monitoring wells downgradient of the ash basin;
• Continued quarterly or semi-annually groundwater and seep sampling;
• Continued analytical result data evaluation;
• Groundwater modeling; and
• Geochemical modeling.
The combined assessment activities have provided significant information for more precise
characterization of the groundwater flow paths and groundwater quality, and further development
of the Conceptual Site Model (CSM). The CSM include complete horizontal and vertical delineation
of groundwater affected by the ash basin.
Based on empirical Site data from numerous (over 30) groundwater monitoring events conducted
over multiple seasonal variations, and supported by groundwater flow and transport model
simulations, it has been determined that groundwater flow from the ash basin is naturally controlled
by hydraulic divides, with the predominant direction of groundwater flow being to the north. There
is no component of groundwater flow from the ash basin in the direction of the Belews Reservoir.
Groundwater monitoring analytical results, indicate that groundwater affected by the ash basin is
delineated to approximately 500 to 750 feet downgradient of the ash basin waste boundary. At its
nearest, the Dan River is approximately 2,300 feet from the ash basin waste boundary. Groundwater
flow and transport model simulations of mobile constituent (e.g., boron) migration also
demonstrate concurrence of delineation with empirical Site data. Additionally, groundwater flow
and transport predictive simulations indicate that future migration of groundwater mobile
constituents do not reach the Dan River. Less mobile groundwater constituents associated with the
ash basin generally attenuate within a localized area near the ash basin waste boundary.
Geochemical modeling indicates that future Site conditions will not affect mobility and attenuation
of the less mobile constituents.
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March 5, 2020
Mr. Lanter Letter
Based on the additional Site assessment activities it is determined that the Dan River and Belews
Reservoir are not currently, nor predicted to be in the future, receptors of affected groundwater
migration from the ash basin. Because the surface water evaluation is intended to characterize Site
affected groundwater to surface water pathways, and assess if affected groundwater migration has
resulted in constituent concentrations in Site surface water receptors greater than applicable 15A
North Carolina Administrative Code (NCAC) Subchapter 02B .0200 (02B) standards, Duke Energy
does not believe that resampling surface water locations in the Dan River or Belews Reservoir
should be conducted since neither is a receptor of affected groundwater migration. Complete
discussion and results of assessment activities mentioned herein are presented in the CAP Update
(SynTerra, 2019).
References for this Comment Response:
Corrective Action Plan Part Update — Belews Creek Steam Station, December 31, 2019 (SynTerra,
2019)
Comment:
DEQ recommends that Duke Energy contact the Winston-Salem Regional Office hydrogeologist prior to
sampling to ensure consensus with proposed sampling locations. The results of the surface water
evaluation shall be provided in an amendment to the Corrective Action Plan (CAP) Update for the facility
submitted on December 31, 2019.
Response:
While Duke Energy does not believe that resampling surface water locations in the Dan River or
Belews Reservoir should be conducted, Duke Energy does plan to conduct additional surface water
sampling from the Belews Reservoir for assessment of the additional source areas, including the
Coal Pile, Gypsum Pad, and Structural Fill. A work plan, with proposed Belews Reservoir sample
locations, will be submitted to DEQ for approval prior to conducting sampling.
Dan River Combined Cycle Station
The Dan River Surface Water Evaluation Report was submitted to NCDEQ on November 21, 2019. The
evaluation included results from surface water sampling that occurred in the Dan River during August 28
through 31, 2018.
Comment:
DEQ received the Surface Water Evaluation Report on November 21, 2019.
Response:
Acknowledged
Comment:
Lead and mercury were detected above the 15A NCAC 02B Surface Water Standards at sampling location
GW/SW-14. DEQ recommends that additional surface water sampling be performed in this tributary
upstream of GW/SW-14. DEQ recommends that additional surface water sampling be performed in this
tributary upstream of GW/SW-14, specifically upstream (if possible) and immediately downstream of the
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March 5, 2020
Mr. Lanter Letter
LCID Landfill. In addition, a review of available surface water monitoring data, especially lead and
mercury analytical results, should be included in an evaluation of site conditions considering
groundwater to surface water discharge. A discussion of these exceedonces and their potential source(s)
should be included in the upcoming CAP Update or for the facility.
Response:
The Land Clearing and Inert Debris (LCID) landfill (Permit 79B-LCID) is a closed inert debris landfill
permitted through the NCDEQ Division of Waste Management and does not require assessment. In
a meeting to discuss NCDEQ comments on the Comprehensive Site Assessment (CSA) Update
(SynTerra, 2018), it was determined that Duke Energy would present evidence that the LCID landfill
is not a source and does not require assessment, including history and construction documentation.
This evidence will be provided in the forth -coming Updated Corrective Action Plan. The constituents
detected at GW/SW-14, lead and mercury, have not been identified as constituents of interest in
groundwater at Dan River as documented in the CSA. Therefore, Duke Energy does not believe that
additional surface water sampling in the vicinity of the LCID is warranted.
Lead
The dissolved lead concentration that resulted in the chronic lead value greater than the applicable
02B criteria at GW/SW-14 is anomalous and should be discarded from the chronic concentration
calculation. The dissolved lead concentrations observed at GW/SW-14 are greater than the total
concentrations (non -detect) at this sample location (Table 1), which prompts the addition of the
data quality flag'S1' ("Data review findings indicate result may be biased, however, date is
unusable."). The S1 data flag is included in Table 1. In order to calculate acute concentrations, two
samples were taken within one hour on August 29; however, the concentrations of dissolved lead in
these samples varied by one order of magnitude. Further, dissolved lead concentrations from other
samples collected at GW/SW-14 were less than the reporting limit. These facts indicate that the
sample results collected on August 29, 2018 are anomalous and the results should not be included in
the calculation of chronic lead values.
TABLE 1
LEAD CONCENTRATIONS AT GW/SW-14
Sample ID
Reporting Units
µg/L
µg/L
15A NCAC 02B (Class Q
NE
0.54
Sample
Collection Date
TOTAL
CONCENTRATION
DISSOLVED CONCENTRATION
GW/SW-14
08/28/2018
0.71
<0.1
GW/SW-14
08/29/2018
<0.1
3.6 S1
GW/SW-14 (2)
08/29/2018
<0.1
0.33 S1
GW/SW-14
08/30/2018
0.44
<0.1
GW/SW-14
1 08/31/2018
12.2
<0.1
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March 5, 2020
Mr. Lanter Letter
Mercury
The sampling and analytical procedures for mercury frequently cause inaccurate and/or imprecise
results due to the sensitivity of the sample collection and analytical methodology, which is the likely
reason for concentrations exceeding 02B criteria at GW/SW-14. Mercury was detected in the blank
for the samples taken on August 29, and 31, 2018 (data flags B and BC). The chronic concentration
calculated at GW/SW-14 is 0.003 µg/L greater than the 02B standard, which is likely attributable to
issues in the sampling methods or lab methods particular to mercury.
Riverbend Steam Station
The Riverbend Surface Water Evaluation Report was submitted to NCDEQ on July 24, 2019. The
evaluation included results from surface water sampling that occurred in the Catawba River during
March 13 through 16, 2018.
Comment:
DEQ received the Surface Water Evaluation Report on July 24, 2019.
Response:
Acknowledged
Comment:
Please ensure that the surface water sample nomenclature is the some in the report as in the Figures and
Tables.
Response:
Surface water samples for the evaluation were collected during March 2018. Sample nomenclature
is summarized:
Catawba River sample locations are referenced in report text and Figure 2-1 as RBSW-1
through RBSW-13.
Sample results from those locations are summarized in Tables 4-1, 4-2, and 4-3 as RBSW-01
through RBSW-13 [Le., with a leading zero (0) for samples RBSW-01 through RBSW-09].
The use of a leading zero is maintained in the comprehensive database for Riverbend, and often in
report tables, for organizational purposes.
Other sample nomenclature in report text references seeps addressed as part of the Riverbend
NPDES program:
• Twelve seep outfalls (Outfalls 101 through 112) are a part of the Riverbend NPDES program.
• Those outfall locations were labeled on Figure 2-1 as S-1 through S-12. That nomenclature
was used prior to the locations being identified as NPDES seep Outfalls 101 through 112.
The facility map that Duke Energy routinely provides to NCDEQ as part of Riverbend
comprehensive data submittals illustrates those sample locations as being coincident.
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March 5, 2020
Mr. Lanter Letter
The seep outfalls were referenced, but not used, as part of the surface water evaluation. In future
reports, use of clear and consistent sample nomenclature in text, figures, and tables will be ensured
through quality reviews.
Comment:
Additional monitoring at RBSW-08 is recommended due to the high levels of manganese.
Response:
A North Carolina 02B surface water standard is not currently established for manganese. Prior to the
January 1, 2015 amendment to 15A NCAC 02B, a 02B surface water standard of 200 µg/L in Class WS
(Water Supply) surface water was established for manganese. As referenced in the paragraphs that
follow, the 02B standard for manganese was purposely removed as part of the most recent North
Carolina Triennial Review process required by the Clean Water Act. The review period occurred from
2007 to 2014.
On November 13, 2014, the North Carolina Environmental Management Commission (EMC) adopted
amendments to the 02B regulations following the most recent Triennial Review. Based on the
review process, the NCDEQ Division of Water Resources (DWR) determined that there was no
evidence to conclude that discharges of manganese will affect any beneficial uses of North Carolina
water. The amended 02B regulation removed the previously established 02B standard for
manganese on January 1, 2015.
USEPA recommends a criterion of 50 µg/L for manganese in surface water that is classified as a
water supply. This concentration corresponds to the USEPA Secondary Maximum Contaminant Level
(SMCL) established for aesthetic considerations related to taste, color, and staining applicable to
drinking water systems, not to surface water. As part of the Triennial Review process, NCDEQ noted
that this guidance could be used by water suppliers, if ever warranted, to protect users from
objectionable taste and/or staining of laundry. This recommended criterion of 50 µg/L does not
represent a human health or ecological risk in surface water or even in end -user drinking water.
Comparisons with applicable USEPA National Recommended Water Quality Criteria for Protection of
Aquatic Life, Human Health, and/or Water Supply were provided in the Riverbend surface water
evaluation report Table 4-3 as reference. As stated by USEPA, those criteria are not a regulation, nor
do they impose a legally binding requirement. Therefore, comparisons with those criteria are only
for situational context.
The surface water evaluation sampling and results are summarized as follows:
• Surface water samples were collected at Riverbend in the Catawba River from March 13-16,
2018, in accordance with the NCDEQ-approved work plan.
• Manganese concentrations were less than the 50 µg/L USEPA recommended criterion in
samples collected at the RBSW-8 location on March 13, March 14, and March 16.
• The manganese concentrations were only slightly greater than 50 µg/L in RBSW-8 samples
collected on March 15 (55 µg/L and 67 µg/L).
• All of the Riverbend surface water evaluation samples yielded manganese concentrations
less than the 200 µg/L historical 02B standard that was removed in 2015.
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March 5, 2020
Mr. Lanter Letter
Based on the following:
• the lack of a 02B surface water standard for manganese,
the purposeful withdrawal of the historical North Carolina 02B standard from the NCDEQ
02B regulation during the last Triennial Review,
the USEPA approval of the action for withdrawal,
the applicability of the USEPA value as a guideline to finished drinking water, not to surface
water.
Duke Energy believes there is no need to resample for a parameter that is technically and regulatory
irrelevant in this situation. Any further sampling and data generation at RBSW-8 or other surface
water sampling locations in the Catawba River would only produce additional data that are
irrelevant.
If you have any questions or need any clarification regarding the information provided, feel free to contact
me at or at 919-546-7863 at your convenience.
RAToepDfer,
y sub itted,
J .E.
Lead Engineer, Duke Energy EHS CCP
Waste & Groundwater Programs
cc: Mr. Eric Smith — DEQ DWR
Mr. Ed Sullivan — Duke Energy
Duke Energy NC W&GW Programs Team