NC0004987_Groundwater Extraction Wells_20181011

ii"iikt, DUKE
ENERGY®
Oct. 11, 2018
Mr.Jeff Poupart,Section Chief
NC DWR Permitting Section RECEIVE®/®E��®�R
1617 Mail Service Center
Raleigh,NC 27699-1617
OCT 1 5 2018
Subject: Groundwater extraction wells
Marshall Steam Station Water Resources
Permit#. NC0004987 Permitting Section
Catawba County
Dear Mr Poupart:
In accordance with requirements in North Carolina's Coal Ash Management Act(CAMA), Duke Energy is required
to cease the discharge of stormwater into the ash basin at Marshall Steam Station by December 31,2019.
As part of this effort, offsite stormwater will be rerouted and collected into two lined stormwater collection basins
located at the upstream end of the ash basin between the Structural Fill and Industrial Landfill#1. From the lined
collection basins, it will be conveyed to Industrial Stormwater Outfalls located to the north east of the ash basin
dam. (This system has been permitted though the Industrial Stormwater Permit NCS000549.) Because the lined
collection basins will be built into the ground, construction will involve excavation, and, during the excavation
process, the excavated area will need to be dewatered. Duke Energy's planned method of dewatering the area is to
install groundwater extraction wells upgradient of the excavation area and to route the pumped groundwater to the
ash basin.
In Duke Energy's opinion, this approach does not require a modification to the NPDES permit. As reflected in the
site's Comprehensive Site Assessments, groundwater flow in this area is toward the basin and this water would
discharge to the basin even in the absence of the extraction wells, so it does not constitute a new waste stream. It is
more correctly characterized as the movement of water within a system. Groundwater data does not reflect
contamination with coal ash constituents in this area, and there is no anticipated impact to the nature of the discharge
from the impoundment. To ensure the Department agrees with our understanding, Duke Energy requests the
Department's concurrence in writing prior to the anticipate start of extraction well construction on January 2019.
If there are any questions about this matter,please contact Brad Loveland(704)609-5637.
Sincerely,
f ,itiY(
Richard E.Baker,Jr.,P.E.,PMP
Director,EHS CCP Environmental Programs
Duke Energy
cc Brad Loveland/Filenet
Shannon Langley
Corey Basinger—Regional DWR Supervisor,Mooresville
Tyler Hardin,Duke Energy