Multi ID#'s_IAP Conditional Approval Letter FINAL_20160722

Water Resources
ENVIRONMENTAL QUALITY
Harry K. Sideris
Senior Vice President
Environmental, Health & Safety
Duke Energy
526 South Church Street
Mail Code EC3XP
Charlotte, North Carolina 28202
PAT MCCRORY
Governor
DONALD R. VAN DER VAART
Sec a ary
S. JAY ZIMMERMAN
July 22, 2016
gree«.
Subject: Interim Action Plans Conditional Approval
Asheville Steam Electric Plant, Belews Creek Steam Station, H. F. Lee Energy
Complex, and L. V. Sutton Energy Complex
Dear Mr. Sideris:
As part of the Settlement Agreement (Agreement) between the North Carolina Department of
Environmental Quality (DEQ) and Duke Energy, signed on September 29, 2015, Duke Energy is
required to implement accelerated remediation at the subject facilities that demonstrated off-site
groundwater impacts. On February 17, 2016, DEQ received Accelerated Remediation Summaries
for each subject facility. On March 28, 2016, DEQ sent a letter regarding technical direction for
the Accelerated Remediation Plans, subsequently referred to as Interim Action Plans, and
requested responses to specific items in each plan. On April 29, 2016, DEQ received the revised
plans for the subject facilities. The proposed schedules provided in the respective plans are
expected to be met unless revisions are communicated to and approved by DEQ. The remedial
system start -un dates for each facility shall be no later than March 31 2017 If the start-up
date cannot be met, Duke Energy shall submit in writing, no later than March 1, 2017, a request
for extension of this date and documentation of why the date cannot be met.
Based upon a review of the information submitted in the Interim Action Plans, conditional
approval of the conceptual approach proposed for all four (4) facilities is given in order to
implement tests to confirm the efficacy of the proposed remedial systems. DEQ's approval is
based on the information submitted in the proposed Interim Action Plans and is contingent upon
the following conditions that apply to all facilities:
1. Documentation of all groundwater constituents sampled and the associated analytical
methods that are part of the Interim Action Plans must be submitted to the respective
Regional Offices.
State of North Carolina I Environmental Quality I Water Resources
1617 Mail service Center I Raleigh, North Carolina 27699-1617
919 707 9000

2. Well development water or contaminated groundwater from the extraction wells during
testing may not be discharged to the land surface and must be captured and placed back
into the active basin. This should be addressed in the Application for Permit to Construct
an Extraction Well and potentially included as a condition in the Well Construction Permit.
3. Transport models must be developed to predict how long it will take for boron
concentrations (expected to be the most mobile of all the constituents of interest [COIs])
to decrease below 2L standards at the compliance boundary and at receptors at least through
2045. The models must be run to predict boron distribution under excavation and
excavation -and -extraction scenarios and provided as part of the transport model in an
appendix to the Basis of Design Report.
4. Changes to the groundwater system (decreased water level and (or) changes to pH, Eh, or
ionic strength) during extraction could result in enhanced mobilization for certain COIs.
This must be evaluated as part of all active remediation efforts proposed with results
provided as part of the geochemical model in an appendix to the Basis of Design Report.
5. Evaluation of alternative technologies or technical approaches to achieve Agreement
objectives related to potential off-site groundwater impacts must be considered as part of
the implementation of the Interim Action Plans. This focused evaluation of alternative
remedial alternatives must be provided as an appendix to the Basis of Design Report.
In addition, approval of the Interim Action Plans for the specific facilities are contingent on the
following conditions:
1. Asheville Steam Electric
• There are areas west-southwest and south of the 1982 basin at the Asheville facility
that contain offsite migration of groundwater and (or) seeps with boron and/or other
coal ash -related constituents detected at concentrations above 2L Standards. While the
Interim Action Plan specifies activities to evaluate the extent of offsite migration from
the area west-southwest of the 1982 basin by assessing groundwater conditions and
potential flow west of the French Broad River, nothing is proposed for the area south
of the 1982 basin. Information is needed to show which supply wells have been
sampled and which have not been sampled in these study areas along with analytical
results where available in order to understand site conditions and potential off-site
migration of coal ash -related COIs. This information must be compiled and submitted
to the Asheville Regional Office for review of data gaps at these locales as part of the
Interim Action Plan implementation.
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• The Interim Action Plan does not specify which water supply wells west of the French
Broad River will be logged using borehole geophysics. DEQ requests that borehole
geophysical logging be conducted in all five (5) water supply wells.
• The Interim Action Plan does not provide details about how bedrock monitor well MW-
18BRL was sited even though it states that the location was chosen "based on
groundwater chemistry data, observed geologic structures, and geographic relationship
between the Plant, French Broad River, and select water supply wells west of the
River". While this location may be optimal, no supporting information or rationale was
provided to suggest well installation at this location will meet objectives. The proposed
well location seems to be sited too far north to be relevant to the assessment of fracture
sets and flowpaths that could, potentially, connect the ash basins to the supply wells
located south of this location such as AS 14. A bedrock monitoring well at a different
location should be considered and communicated to the Asheville Regional Office.
• Evaluation of a slurry trench as an alternative remedial system is requested at the
Asheville facility as part of the Interim Action Plan. Installation of a slurry trench
(with, for example, limestone to increase the pH and sorptive capacity for certain
dissolved metals) may be as effective at contaminant removal as an extraction system
and would circumvent the need to dispose of contaminated extraction waters. Whether
or not boron and the other COIs such as arsenic, chloride, cobalt, iron, manganese,
selenium, total dissolved solids, hexavalent chromium in this area would be effectively
attenuated with a slurry trench must be evaluated using results of the geochemical
model or equivalent. Increasing the pH beyond a certain threshold can result in
contaminant mobilization rather than attenuation. These factors must be considered as
part of a slurry trench evaluation.
2. H.F. Lee Energy Complex
• DEQ agrees with the approach provided in the Interim Action Plan. However, the
potential effects of drawdown from the proposed extraction wells on nearby wetlands
shall be monitored and addressed as part of plan implementation.
3. Belews Creek Steam Station and the L.V. Sutton Energy Complex
• DEQ agrees with the approach proposed in the Interim Actions Plans for the Belews
Creek Steam Station and the L.V. Sutton Energy Complex; no additional conditions
are recommended at this time for these two facilities.
Before full implementation of the interim action at each of the above facilities, Duke Energy must
provide an Aquifer Test Report and a Basis of Design Report for final DEQ approval. The reports
must include (but are not limited to) baseline site conditions, specific aquifer characteristic data, a
refined site conceptual model, design basis, calculations and assumptions, system performance
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metrics, institutional controls, contingency plans, and construction and monitoring schedules.
Maps that show existing and inferred 2L Standards exceedances in groundwater across the facility
must be provided or referenced in the previously mentioned reports. In addition, engineering
design/specifications packages may be required by DEQ to review before implementation of
interim actions.
Please begin implementing these plans immediately to include the conditional items listed. If you
have any questions, please feel free to contact Steve Lanter at [phone].
Sincerely,
c- —
StaiZnnan, P.G., Director
Division of Water Resources
cc: Landon Davidson – ARO Regional Office Supervisor
David May – WARO Regional Office Supervisor
Jim Gregson – WIRO Regional Office Supervisor
Sherri Knight– WSRO Regional Office Supervisor
WQROS Central File Copy
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