NC0003417_Lee 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
H. F. Lee Energy Complex
Dear Mr. Sullivan:
PAT MCCRORY
Gmremor
DONALD R. VAN DER VAART
Secrelory
S. JAY ZIMMERMAN
Director
On November 22, 2016, the North Carolina Department of Environmental Quality's Division of
Water Resources (Division) received the 30% Basis of Design (BOD) Report for the H.F. Lee
Energy Complex subject facility. Division staff from the Washington Regional Office have
reviewed the BOD Report and offer the following comments:
• Content for Appendix B through Appendix H is expected for the 60% BOD Report in order
to facilitate review of the proposed groundwater extraction system.
• Include a discussion on whether operation of dewatering well system will impact any
potential wetlands (or whether wetlands are in the area). If potential impacts are
determined, the plan should include piezometers to monitor water levels in adjacent
wetlands.
Recovery wells projected to have a 300' radius of influence with 3' drawdown at the well.
Hydraulic Conductivity is 136 ft/day. Nine wells are proposed with 300' spacing. Would
more wells with closer spacing being pumped at a lower rate (with less drawdown and
radius of influence) achieve same goal of plume control/recover and result in a lower
probability of wetland degradation?
Recovery well design indicates wells will be 25' — 40' deep with bottom 10' screened. If
so, top of screen will be well below top of surficial water table (-4' — 8' bls). Also, well
logs indicate upper stratigraphy is tighter fine sand/silty clayey sands whereas deeper
portions where screens would be located are coarser/gravelly sand. What is the rationale
for the proposed screened interval?
State of North Carolina I Envlroumeotal Quality I Water Resources
1617 Mad service Center I Raleigh, North Carolina 27699-1617
919 707 9000

• AQTESOLV Modelling comments for PTW-I. Why are there differences in the following
aquifer properties in the different model configurations?
o Step Drawdown (Attachment 2): Aquifer Model type is confined, saturated
thickness is 19.75', anisotropy is 1
o Pump Test (Attachment 3): Model type is unconfined, saturated thickness is 40'
anisotropy is 0.256
• The "groundwater remediation system" will be the same "unit" as the wastewater treatment
system used to further treat water generated during the dewatering phase of the active ash
basin. There doesn't appear to be a part of the BOD report that will cover the "treatment
system design" and demonstrate that it will satisfy intended treatment levels (for the water
that will ultimately be discharged out Outfal1001.
• Revisions to the groundwater models should be provided to the Division to account for
deficiencies in the original submittals. It is recommended that a brief description be
provided of, at a minimum, the new model domain, new boundaries, and new boundary
conditions. This information may be provided to the Division under separate cover
(technical memorandum, for example) concurrently with (or prior to) the 100% BOD
report. This will allow the Division to provide input prior to publishing model results
within the final BOD report.
If you have any questions, please feel free to contact the Washington Regional Office at (252) 946-
6481 or Steve Lanter at [phone].
Sincerely,
S. J y ZZerm�PG.,,irector
Division of Water Resources
cc: David May — WARO Regional Office Supervisor
WQROS Central File Copy
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