NC0000396_BOD Comments Letter FINAL_20161221

Water Resources
ENVIRONMENTAL QUALITY
December 21, 2016
Ed Sullivan
Duke Energy
526 South Church Street
Mail Code EC13K
Charlotte, North Carolina 28202
Subject: Basis of Design Report Comments
Asheville Steam Electric Plant
Dear Mr. Sullivan:
PAT MCCRORY
Gavemor
DONALD R. VAN DER VAART
Secretory
S. JAY ZIMMERMAN
Direclor
On November 22, 2016, the North Carolina Department of Environmental Quality's Division of
Water Resources (Division) received the Basis of Design (BOD) Report for the subject facility.
Division staff from the Asheville Regional Office have reviewed the BOD Report and offer the
following comments:
Section 1.1.2, Interim Action Plan
The report states that "interim action activities will consist of continued assessment of
downgradient areas at both ash basins and pilot testing with potential of installing a
groundwater extraction system near the NE side corner of the 1964 basin". It is not clear
why there is still only a "potential" of installing the groundwater extraction system,
particularly given the fact that the extraction system is the focus of the accelerated
remediation strategy and the main purpose of the BOD Report. Since preliminary results
from pumping tests indicate conductive fractures exist in the study area that would facilitate
design of a groundwater extraction system, at least conceptual design details should be
included in this submittal. Robust details concerning design of a groundwater extraction
system are expected for the 60% BOD Report.
Section 1.1.4, Scope and Objectives of the Interim Action
1. The report states that "seep and surface water data indicate exceedances of 2L standards
or 11114CS for boron, chloride, cobalt, iron, manganese, mercury, selenium, sulfate, TDS,
and vanadium." These data, along with groundwater data from the target area, should be
provided in summary form in the BOD Report as a benchmark for evaluating system
performance. Please explain the significance of surface water samples exceeding the 2L
State of North Carolina I Envircornental Quality I Weterltesources
1617 Met service Center I Raleigh, North Carolina 27699-1617
919 707 9000

or Interim Maximum Allowable Concentration (IMAC) standards and how this relates to
corrective action requirements in 2L and (or) CAMA.
Section 2.1, Refined Site Conceptual Model, Geology and Hydrogeology
1. Nowhere in this section is it mentioned that a flood plain wetland complex west of the site
is an area of contaminated groundwater discharge. Contaminated groundwater originates
beneath the ash basins, flows downgradient, and discharges either to the French Broad
River or to seeps and channels in this low lying area. The contaminated seeps and channels
empty to the French Broad River through 5 stream channels. Disregarding the wetland
complex is a major omission in the conceptual model. Please explain why such a
fundamental component of groundwater flow and contaminant transport is not described
in the report. Please explain how this area is expected to be affected by the proposed
extraction system and how it is being addressed in the flow and transport models.
2. Nowhere in this section is it mentioned that a possible hydraulic connection exists between
on-site ash basins and supply well(s) west of the French Broad River. A great deal of effort
has gone into studying and understanding this possibility, as evidenced in the
Comprehensive Site Assessment (CSA) Supplemental Report (Syntena, 2016)
(conclusions are pending), and yet the report states unequivocally on page 2-2 that the
French Broad River is a hydraulic boundary. To ensure that the conceptual model is
relevant and up to date, it is recommended that this possibility and any corresponding data
be briefly described. This is particularly important since the purpose of the interim action
is to reduce contaminants moving off site.
Section 2.2, Summary of Baseline Conditions
This section states that "geophysical logging and pumping tests demonstrate a high degree
of heterogeneity at the site". The report also points out how this heterogeneity effects the
variability of contaminant concentrations in wells in close proximity. During the pumping
test boron concentrations in the highly -connected extraction well EXT -01 stabilized at
about 11,000 ug/L versus only about 800 ug/L in the poorly -connected extraction well
EXT -02 located about 200 feet away. Based on the 11,000 ug/L measurement, it appears
that the heart of the plume is not being measured downgradient (no other monitor well in
this area is measuring boron concentrations above 6140 ug/L and most wells are between
1000 and 5000 ug/L). Please explain how the project team can be confident that the
maximum plume concentrations are being measured with the existing monitor wells
available in this area, particularly given the highly heterogeneous groundwater flow system
through which the contaminants move and the fact that some wells (EXT -2, e.g.) are not
open to primary zones of constituent mass. If maximum concentrations are not being
measured, how would this be expected to affect the groundwater assessment or transport
model calibration and long term predictions.
2. Boron isotope sampling was proposed (CSA Addendum, Synterra, 2016) to help evaluate
whether or not boron concentrations in supply wells west of the French Broad River are
associated with coal ash (to date, two wells contain unexplained, anomalous boron

concentrations). Because water quality in supply wells is a high priority and appropriately
evaluated as an "interim action", it is recommended that the isotope work be formally
included in this effort and report. This will allow an expedited evaluation of the supply
wells in question and would lead, if needed, to an expedited remedy.
Section 3.3, Groundwater Flow Modeling
The Division is unable to review the appropriateness of any revisions made to the
groundwater flow model. Revisions were requested earlier in the year by the Division to
account for deficiencies in the original submittal. It is recommended that a brief description
be provided of, at a minimum, the new model domain, new boundaries, and new boundary
conditions. This would allow the Division to provide preliminary concurrence (or
recommended changes) of the revised model. This level of transparency could save the RP
a great deal of time and effort working on a product that may or may not provide the
information needed for Corrective Action Plan (CAP) approval. Alternatively, this
information may be provided to the Division under separate cover (technical memorandum,
for example) concurrently with (or prior to) the 60% BOD report. This will allow the
Division to provide input prior to publishing model results within the final BOD report.
Section 3.5, Fate and Transport Modeling
The Division is unable to review the appropriateness of any revisions made to the Fate and
Transport model. Revisions were requested earlier in the year by the Division to account
for deficiencies in the original submittal. It is recommended that a brief description be
provided of the most significant changes to the F -T model and at what specific location(s)
(that is, compliance boundary, specific wells, French Broad River, and (or) streams) that
the results will be generated. This would allow the Division to provide preliminary
concurrence (or recommended changes) of the new model.
Section 4.0, Pumping Tests
1. As noted in the report, the analytical methods developed by Cooper -Jacob are based on
certain aquifer assumptions that do not hold at the site. For example, Cooper -Jacob
assumes homogeneous, isotropic, and uniformly thick aquifers, horizontal layers that
extend infinitely in the radial direction, etc. Theis methods are also based on many of these
same assumptions. As discussed at length in the report, highly heterogeneous conditions
prevail in the area of the pumping tests. While it is acknowledged that useful information
may be obtained using these analytical methods, aquifer test results that affect system
design (extraction well spacing, e.g.) and operation (pumping rates, e.g.) obviously should
be used with caution. The report seems to recognize this as potential adjustments in
extraction well placement, number, and flow rates are envisioned.
Section 5.0, Analytical Results
1. Wells ABMW-2 and ABMW-4 are discussed in the text but are not shown in either the
Fig. 1-2 in the BOD report or the Fig. 1-2 in the Pump Test report.

Section 8. 1, System Performance Metrics
1. The Division is unable to review the appropriateness of the selected metrics by which the
system performance will be judged. These metrics were not provided. This is a key section
of the report. These metrics should be defined and clearly presented in this 30% submittal.
The only reference to this is that the groundwater extraction system will be operated "to
achieve the objectives of this accelerated groundwater remediation effort." It goes on to
say that "an anticipated initial drawdown of three feet is expected to meet this objective"
but the authors do not define "this objective" nor do they define the length of time that the
initial drawdown should be maintained, why this amount of drawdown is needed, and to
what purpose. Ultimately, the purpose of the system is to gain hydraulic control and reduce
contaminant concentrations and this should be the central focus of the project team.
Page 1-3 states that "the primary objective of the groundwater extraction system is to
accelerate the reduction of constituents in groundwater to below 2L at and beyond the
compliance boundary". It is strongly recommended that a performance metric be defined
in terms of groundwater concentrations of boron in specific monitor wells (see comment 2
in the List of Figures section below for a list of recommended target wells). If boron does
not decrease in the target wells after a selected amount of time it calls into question whether
the system is capable of meeting its objective to control downgradient groundwater
concentrations. In addition, the following constituents that are occurring above 21/IMAC
in this area should be formally monitored to judge system performance: Cl, Co, Fe, Mn,
5O4, TDS, V. The concentrations of Co, Fe, Mn, and V likely are driven in part by
geochemical conditions that should be formally evaluated as part of pH and Eh time series
monitoring, geochemical modeling, and transport predictions.
List of Figures
1. Fig. 1-2: Please check the mapped position of wells shown in fig. 1-2, Conceptual
Remediation System (BOD Report). EXT -1 appears to be mapped incorrectly, based on
information in table 4-1 that provides distances to MW -08S and MW -09S and based on its
position shown in fig. 1-2, Pump Test Well Location Map. Also, please clarify whether
wells B -1-A, B-1, and B-2, shown in fig. 1-2 in close proximity to EXT -2, were used in
the pumping tests?
2. The Division is unable to review the appropriateness of Fig. 3-1 and 3-2. Specific wells
that will be used to plot pH -time and Eh -time are not provided. Recommend plotting pH
and Eh time series for each of the following wells: EXT -01, MW -8S, MW -9S, MW -17A,
CB -8, MW -9D, MW -18D, MW -913R, GW -2, MW- 18BR, and any other utilized extraction
wells for these plots.
3. Need an additional figure: "Stacked" boron vs time plots to include: EXT -01, MW -8S,
MW -9S, MW -17A, CB -8, MW -9D, MW -18D, MW -913R, GW -2, MW -1813R, and any
other utilized extraction wells based on sampling once every 60 days during the first year
of operation.
51

4. Need an additional figure: Shallow potentiometric surface map, pre -pumping and during
pumping. Map should also include the stage of proposed NPDES effluent channels at the
time of the potentiometric measurements.
5. Need an additional figure: Deep (TZ) potentiometric surface map, pre -pumping and during
pumping. Map should also include the stage of proposed NPDES effluent channels at the
time of the potentiometric measurements.
6. Need an additional figure: Bedrock potentiometric surface map, pre -pumping and during
pimping -
List of Appendices
1. Unable to review appropriateness of Appendix E, Technical Specifications. No
information is provided regarding what technical specifications will be presented.
If you have any questions, please feel free to contact the Asheville Regional Office at (828) 296-
4500 or Steve Lanter at [phone].
Sincerely,
S*G
JaZ merman, P.G., Director
Division of Water Resources
cc: Landon Davidson — ARO Regional Office Supervisor
WQROS Central File Copy