NC0022406_WSRO BOD Comments Letter FINAL_20170201

Water Resources
ENVIRONMENTAL QUALITY
February 1, 2017
Ed Sullivan
Duke Energy
526 South Church Street
Mail Code EC13K
Charlotte, North Carolina 28202
Subject: Basis of Design Report Comments
Belews Creek Steam Station
Dear Mr. Sullivan:
ROY COOPER
Goremor
MICHEAL S. REGAN
Secrelary
S. JAY ZIMMERMAN
Director
On December 29, 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 Winston-Salem Regional Office have reviewed the BOD Report and offer
the following comments:
1. While itis acknowledged this is a 30% Basis of Design Report, several components of this
document are sparse or are not present, making an evaluation of the proposed system
problematic. Please work to provide more information across all facets of system design,
especially regarding further aquifer testing and groundwater modeling, to facilitate review
of the Final Basis of Design Report.
2. The scope and objectives outlined in Section 1.1.4 are not clear and should be refined for
the Final Basis of Design Report.
3. The evaluation of remedial alternatives in Section 3.2 is not thorough and requires more
consideration in the Final Basis of Design Report.
4. Section 2.1 Geology and Hydrogeology indicates that in the area of Parcel A, groundwater
flows across the topographic divide of Middleton Loop Road to the northwest toward
Parcel A and the Dan River. Please evaluate whether the crossing is due to head conditions
from the ash basin or preferential flow paths within the shallow and/or deep flow layers
and, if necessary, adjust the designed system accordingly.
5. As indicated in 2.2.2 Summary of HDR Recent Groundwater Quality Results, the boron
concentration in GWA-19S exhibited a value elevated above 2L Standards, displaying a
significantly higher level than wells GWA-18S and GWA-10S that are located between
GWA-19S and the edge of the ash basin. The distribution of boron in this area does not
appear to conform to the LeGrand slope -aquifer model. Additional characterization is
needed to delineate the extent of potential CCR impacts and evaluate the possibility of a
State of North Carolina I Environmental Quality I Water Resources
1617 Mail service Center [ Raleigh, North Carolina 27699-1617
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preferential pathway in the area. Based on Appendix A figure 2, an additional shallow
monitoring well west of the plume should be installed to further refine the plume.
6. Please also show groundwater concentrations on the Cross -Sections in Appendix A, which
helps evaluate the designed system.
7. Only five deep (transition zone) wells spaced approximately 200 feet were proposed for
phase 1. Based on the distribution of the groundwater contamination plumes and the
aquifer testing results, the designed phase I groundwater extraction system may not be able
to prevent the groundwater from flowing across the boundary toward Parcel A because of
less number of recovery wells. Please note, Section 3.4 indicated that up to twenty 6 -inch
diameter extraction wells may be needed along the southeastern side of Middleton Loop
Road based upon a spacing of 45 feet as suggested from the pumping test report.
Furthermore, as indicated in Section 4.1, following the Phase I implementation, greater
pumping rates and drawdown levels may be needed so a design flow rate of 80 gpm is
currently anticipated, which means more wells may be needed. It is reasonable to have a
phased approach for system design and installation because of variable hydrogeologic
conditions. However, it is not clear on what basis only five deep wells were proposed for
phase I. More information on the rationale for the limited number is needed along with
discussion regarding additional phases of work.
8. In addition, there are no plans for potential phase 2 extraction well testing, which may be
needed, or proposed monitoring well locations to evaluate performance of the proposed
system. This information should be provided as part of the Final Basis of Design Report
to facilitate review of the progress concerning the design package,
9. Further aquifer testing in deep (transition) zone is needed after the phase I extraction wells
are installed. In addition, testing of an extraction well or wells at the western portion the
proposed extraction system should be considered to evaluate the heterogeneity and
anisotropy of the aquifer system in an area where there may be preferential pathways as
indicated by elevated leading edge indicators at GW 195.
10. The distance between each observation well and the testing well should be measured and
listed in the table. An enlarged area map clearly showing pumping and observation wells
should be provided.
11. To evaluate impacts from the coal ash basin through the groundwater discharge, surface
water samples should be collected from the Dan River in the vicinity of where S-2
discharges to evaluate site conditions for the proposed interim action.
12. Page 2-5 paragraph 4, last line, 217 feet/day, the number does not sound right. Please
check and correct it.
2

13. The boring log for EW -1 seems to indicate that the well screen fully penetrates the
transition zone. The well screens in the boring logs for TW -2 and TW -1 don't appear to
fully penetrate the transition zone. TW -2 and TW -1 do not appear on the cross sections in
Figures 3 and 4. The well screen in GW -20D does not appear to fully penetrate the
transition zone. Heterogeneity in the aquifer appears to be a significant factor based on the
recharge rates. Therefore, the results of the pumping test on TW -1 may not have provided
sufficient data to calculate hydraulic conductivity and transmissivity for the deep flow
zone.
If you have any questions, please feel free to contact Shuying Wang, the Winston-Salem Regional
Office, at [phone] or Steve Lanter at [phone].
Sincerely,
S. Jay Zimmerman, P.G., Director
Division of Water Resources
cc: Sherri Knight — WSRO Regional Office Supervisor
WQROS Central File Copy