20030147 Ver 2_Other Documents_20150623

June 23, 2015
Ms. Karen Higgins, Environmental Program Supervisor
Division of Water Resources, 40lPermitting Unit
North Carolina Department of Environment and Natural Resources
1617 Mail Service Center
Raleigh, NC 27699 -1617
Re: Duke Energy Progress, Inc.
Yadkin -Pee Dee Hydroelectric Project (FERC No. 2206)
Minimum Flow Deviation Notification
Dear Ms. Higgins:
I i 0 r•
" ►►
• :/ /f
Duke Energy Progress, Inc. (Duke Energy) is required by Condition No. 11 of the Yadkin -Pee
Dee Hydroelectric Project (Project) 401 Water Quality Certification (WQC) No. 3730 Modl to
notify the North Carolina Division of Water Resources (DWR) within five working days of
discovery of any deviation from the minimum flow requirements and/or lake level limitations set
forth in the New License issued by the Federal Energy Regulatory Commission (FERC) on April
1, 2015.
The Project experienced a brief deviation from the minimum flow requirement of 1200 cfs from
the Blewett Falls Development on Wednesday, June 17, 2015, between 0615 hours Eastern
Daylight Time (EST) and 0915 hours EDT (see Enclosed United States Geological Survey
(USGS) Gage No. 02129000 Pee Dee River Near Rockingham, NC). This occurred as a result of
a malfunctioning dissolved oxygen (DO) monitor in the tailrace that began recording low DO
values on the USGS Gage No. 0212880025 (Pee Dee River Below Powerhouse Dam near Pee
Dee, NC). DO enhancement at the Blewett Falls Development is accomplished with vent valves
that are programed to open and close based on the level of DO measured in the tailrace at USGS
Gage No. 0212880025. This monitor began to malfunction due to fouling late in the day on June
16, 2015 but did not fall below the 4.0 mg/1 minimum standard until early on June 17th. This low
value recorded by the gage caused the vent values to open to the maximum extent, which
resulted in a reduction in the amount of flow released from the hydro unit. Once this was
discovered, the generation from the minimum flow unit was increased to bring the flow above
the minimum flow requirement of 1200 cfs.
Duke Energy Environmental Services collected DO data in the tailrace to determine if the data
being recorded by the USGS Gage No. 0212880025 was valid. Values in the 7.5 mg /1 to 8.5
mg /l were recorded which confirmed the fouling of the USGS monitoring equipment. The

USGS was notified on Wednesday June 17, 2015 and the monitoring equipment was replaced on
Thursday June 18, 2015. USGS has removed the invalid DO data from the dataset.
Please note the New License and the 401 WQC presume the minimum flow from the Blewett
Falls Development has been met as long as the flow release recorded at the USGS Gage No.
02129000 is within five percent of the required minimum release. A "true -up" procedure is
allowed where flow releases falling within five percent below the minimum shall be offset by
flow releases five percent greater than the minimum in the same month (see 401 WQC,
Appendix A of New License, page 111, Minimum Flow Compliance and Monitoring). On June
17` over the three hours where the flow release recorded by the USGS Gage No. 02129000 was
below 1200 cfs (13 recorded values), only seven of those were greater than five percent below
the minimum flow requirement. Flow releases over the next two hours were well over the five
percent needed to meet the "true -up" requirement (see Enclosure 1).
Please contact me at (704) 382 -0293 (ai.tyer @ duke- eery co) if you have questions or
required additional information.
Sincerely,
Tami Styer, Project Manager H
Water Strategy and Hydro Licensing
Duke Energy
Enclosure
cc w/ enclosure: Jeff Lineberger
George Galleher
David Scott
Jennifer Burdette (NCDWR)
Enclosure 1: USGS Gage No. 02129000 Pee Dee River Near Rockingham, NC

Enclosure 1
USGS Gage No. 02129000 Pee Dee River Near Rockingham, NC
Flow Release Data for the Blewett Falls Development
Date/Time
Discharge (ft3/s)
Gage Height (feet)
06/17/2015 06:00 EDT
1,200P
1.94"
06/17/2015 06-15 EDT
1,180'
1.93'
06/17/2015 06:30 EDT
1,160P
1.92"
06/17/2015 06:45 EDT
1,160"
1.92P
06/17/2015 07:00 EDT
1,140P
1.91p
06/17/2015 07:15 EDT
1, 130"
1.90p
06/17/2015 07:30 EDT
MOP
1.91p
06/17/2015 07:45 EDT
1,130"
1.90p
06/17/2015 08:00 EDT
1,110p
1.89P
06/17/2015 08:15 EDT
],I lop
1,89"
06/17/2015 08:30 EDT
1,11 op
1.89P
06/17/2015 08:45 EDT
I'll op
1.89p
06/17/2015 09:00 EDT
1,130"
1.90p
06/17/2015 09:15 EDT
1,140"
1.91p
06/17/2015 09:30 EDT
1,200P
1.94P
06/1 7/201 5 09:45 EDT
1,250"
1.97"
/17/2051 :00 EDT
1,330"
2.01p
06/17/2015 10:15 EDT
1,41 Op
2.05p
06/17/2015 10:30 EDT
1,470"
2.08"
06/17/201510:45 EDT
1,560p
2.12P
6/17/201511 :00 EDT
1,600P
2.14p
06/17/2015 11:15 EDT
1,670p
117"