NC0004987_Notification of New Wetness (AOW 2016_20160419

Duke Energy
daShDUKE Marshal!Steam Station
ENERGY. 832East NC Hwy 150
Y Terrell,NC 28682
828-478-7700
Apr. 19, 2016
Sergei Chernikov, Ph.D.
Environmental Engineer II RECEIVED/NCDEQ/DWR
Complex NPDES Permitting Unit
NC Department of Environmental Quality APR 2 5 2016
1617 Mail Service Center, Raleigh, NC 27699-1617 Water Quality
Express Mail: 512 N. Salisbury St., Raleigh,NC 27604 Permitting Section
RE: APPROVAL REQUEST TO CONTINUE PILOT STUDY
FGD Wastewater Treatment— Vertical Flow Cells
Marshall Steam Station
Catawba County
NPDES Permit NC0004987
Dear Mr. Chernikov:
Duke Energy (Duke) is submitting this request to the NC Department of Environmental Quality
(NCDEQ) for approval to extend the pilot test period at Marshall Steam Station (Marshall) for
the FGD wastewater treatment Vertical Flow Cell area(VFC). Duke contacted(NCDEQ)on
June 4, 2015, to request approval to conduct a two-month pilot test at the Marshall's VFC which
included use of pressurized wastewater to more efficiently manage dispersion of mulch in each
of the cells. The pilot study was subsequently approved by NCDEQ on June 4th
The pilot test was initiated on July 9, 2015. Specifically, the pilot test consisted of using a
diesel-powered pump and spray nozzle system to disperse floating compost mats in the VFCs. A
diesel pump was placed inside a lined containment adjacent to the equalization basin (EQ)
discharge splitter box and a 6-inch diameter intake hose was placed in the EQ basin two feet
below the water surface. Pressurized wastewater was conveyed from the EQ to the VFC area via
a 4-inch diameter hose placed inside an external PVC pipe that served as a containment barrier
for the hose. This hose was connected to a pipe header located inside the lined VFC area where
a 1.5-inch diameter spray hose was attached at multiple locations between cells A-F. The spray
hoses were then used to direct the high pressure water to break apart floating mats of the
compost in each of the VFCs weekly, or as needed.
The VFC management team at Marshall found that the use of the diesel-pump and spray system
provided a safe and effective means of dispersing floating compost mats within the VFCs as
opposed to using a conventional hose. The pump and hose assembly provided a higher flow rate
and pressure for breaking up composts mats located near the center of the cells eliminating the
need for conventional/mechanical dispersion by boat and thereby improving both effectiveness
and safety of the cell maintenance.
www.duke-energy.com
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Duke Energy
Marshall Steam Station
8329 East NC Hwy 150
Terrell,NC 28682
828-478-7700
Upon initial testing, Duke requested an extension of the pilot test on September 9, 2015, from
NCDEQ that extended the test period through the end of 2015. The request was subsequently
ciii,approved by NCDEQ on September 9`h. The pilot test resumed operation through late November
2015, or until seasonal floating subsided during cooler months. -
The method used during late 2015 at Marshall has been shown to provide a more safe and
effective means to maintaining mulch dispersion in the VFCs. Duke is requesting that this pilot
test213e. approved for continuation through 2016. Additional, Duke seeks to have this method
included as an approved process within the revised NPDES permit NC0004987.
Please feel free to contact Environmental Specialist,Brad Loveland, at [phone] if you
have any questions regarding this request.
Sincerely,
`
44„.....„..„
Rick R. Roper
General Manager III
Marshall Steam Station
Power Generation Carolinas West
be w/attachment: Brad Loveland
Scott La Sala
Scott Parks
www.duke-energy.com
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