NC0004987_Modification_20191015

fis DUKE Marshall Steam Station
8320 East NC Hwy 150
ENERGY. Terrell,NC 28682
o:828.478.7700
October 15, 2019
Mr. Jeff Poupart
North Carolina Department of Environmental Quality
Division of Water Resources
1617 Mail Service Center RECEIVED
Raleigh, NC 27699-1617
OCT 18 2019
Subject: Marshall Steam Station
NPDES Permit NC0004987 NCDEQ/DWR/NPDES
Request for minor NPDES permit modification
Closing of Outfall 004
Dear Mr. Poupart:
The Flue Gas Desulfurization (FGD) at the subject facility system ceased discharging into the
FGD constructed wetland treatment system (CWTS - NPDES internal outfall 004) in April 2019.
In March 2019 the new FGD wastewater treatment system (WWTS - internal outfall 006) went
into operation replacing the CWTS. Some flows continued to discharge and were monitored
from outfall 004 as activities in preparation for final closure occurred from April into September.
These activities included removal of gypsum from the initial equalization settling basins and the
removal of mushroom compost from the vertical flow wetland cells. Outfall 004 was
permanently grouted shut on October 11, 2019. A minor NPDES permit modification is
therefore requested to remove outfall 004 from NPDES permit NC0004987. Enclosed is a
check for $260 in order to process the minor modification request.
The rainfall runoff from the area of the retired CWTS drains into the ash basin and discharges
out NPDES outfall 002. The CWTS was originallybuilt in a pennisula
p sula area within the ash basin
and was an integral part of the WWTS. The final cells are within the ash basin compliance
boundary. Thus Duke Energy considers the footprint of the CWTS to be part of the ash basin
and final closure of the CWTS is planned to be implemented as determined by the final
approved ash basin closure plans. In the interim the final cells of the CWTS have been
breached to allow for storm water to be managed within the ash basin and discharge via
NPDES outfall 002.
If you have questions, please contact Robert Wylie at [phone].
Sin ely,
Rick Roper, General Manager III
Marshall Steam Station
cc: Wes Bell - DEQ Mooresville Office
Enclosure: Check for Minor Modification Fee