NC0003417_Modification Request_20210430

tta DUKE Duke Energy Progress LLC
H. F. Lee Energy Complex
le1199 Black Jack Church Roao
ENERGY, Goldsboro, NC 27530
April 30, 2021
Sergei Chernikov, PhD
Industrial Permitting Branch RECEIVED
NC Division of Water Resources
1617 Mail Service Center .\PR 30 �021
Raleigh, NC 27699-1617
NCDEQ/DWR/NPDES
Subject: NPDES permit modification request
H.F. Lee Energy Complex
NC0003417
Wayne County
Dear Dr. Chernikov,
Duke EnergyProgress, LLC (Duke Energy) herebyrequests modification of the subject NPDES
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permit to make the following changes in support of ash basin excavation activities:
1) Modify the flow limit associated with outfalls 005a and 005b. Currently, these outfalls are
limited to a monthly average flow volume of 1.0 MGD respectively. These outfalls are
associated with closure of inactive ash basins that were generally operational from the 1950's
through the mid-1980's.
Historically, these areas have flooded very infrequently. From 1950 through 2015, the river
level got high enough to flood this area 9 times (average once every 7.2 years). From 2016
to current, the river has risen high enough to flood the basins 7 times (average once every 0.7
years) with 5 of these events occurring in the last 1.5 years. The water from flooding
generally takes several months for the water levels in the basins to dissipate. Duke is
evaluating ways to mitigate any future flooding impacts but those will take some time to
evaluate, permit and implement, if proven feasible and allowable, so the increased flow
capacity is needed to aid excavation and ultimate closure. The current 1.0 MGD flow limit
could require stoppage of work for months at a time. The current permit issuance considered
both outfalls simultaneously from a reasonable potential analysis standpoint therefore:
Duke request that the flow limit be based on the combined flow of outfall 005a and
005b. This will allow for needed flexibility in handling water from flooding and heavy
precipitation between basins as needed.
Additionally, Duke Energy requests that the combined flow limit be modified to 8.0
MGD.
www.duke-energy.com

For additional clarity, the higher flows would generally be associated with higher river flow
conditions as they are requested as a mechanism to mitigate impacts from intense
precipitation and flooding. Therefore, they would not be expected to be occurring during low
river flow conditions at which permit limits and terms are set to protect.
2.) Duke Energy requests 4 new emergency spillway outfalls be added to the permit
associated with the planned construction of emergency spillways in the inactive ash
basin dams.
Construction of emergency spillways in the inactive ash basins is needed to provide added
safety of the basins as these spillways will allow flow from flooding events described above
and heavy precipitation to enter and/or exit the basin in a controlled manner reducing
potential overtopping of the basin's dams. The spillways are being permitted through dam
safety as well and generally consists of long (- 150 ft), shallow indentations in the dam
intended to allow for flow to pass in a controlled and safe manner.
Attachment 1 shows the current planned locations for each emergency spillway. Duke
requests that sampling of releases from the spillways be waived due to safety concerns with
site access conditions under which the emergency spillways would be functioning. Water
exiting the spillways would generally be receding flood waters should that situation occur.
Approximate latitude and longitudes for the spillways are as follows:
Spillway 005s1: 35° 22' 55.24"N
78°06' 31.05"W
Spillway 005s2: 35° 22' 47.91"N
78° 06' 07.51"W
Spillway 005s3w: 35° 22' 32.63"N
78° 06' 24.88"W
Spillway 005s3e: 35° 22' 25.02"N
78° 06' 15.55"W
3.) Remove outfall 003 from the permit. This outfall was originally permitted and
constructed to be used for the combined cycle generation plants operations but has been
discontinued. The line has been physically severed and blanked off.

A check in the amount of$1,030 is included with this submittal cover to cover the required
permit modification fee. Should you have any questions about this request please feel free to
contact Mr. Shannon Langley at [phone] or Joyce Dishmon at (33) 623-0238.
Sinc rely,
Jeffr Hin
P nt Man ger
H.F. Lee Energy Complex
Attachment
Cc: Mike Graham
Sharat Gollamudi
Shannon Langley—via email
Joyce Dishmon/FileNet—via email

Attachment 1
Location map of proposed inactive ash basin emergency
spillways
NPDES permit modification request
H.F. Lee Energy Complex
April, 2021

IN-
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150'SPILLWAY/OUTFALL-� -, i /
10.00 'y 4 INACTIVE BASINS 1 AND 2 /
r: - _ 18.00 18.00 20.00 /
28+00
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+00 3S•$ . ASH�-SHEET PILE WALL STACKED TO
1��ytt ELEVATION 83 00' �,,,
`�.� 100 q / EL 84.00 r.EXISTING GRADE NADV88 z. 100
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15C'SPILLWAYroUTFALL W W10.00 12.00 14.00 16•00 16.00 20+00 T2+00 24+00 26+00 2E60 3W00 32.00 3N00 35.80
�. - DISTANCE(FEET)
A; / INACTIVE BASINS 1 AND 2
- HORIZONTAL:1"=300'
VERTICAL:1"=30'
•
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ASH STACKED To
INACTIVE BASIN 3 ELEVATION B3 W
r SHEET PILE WALL NADV88
cg7 r b/'� EXISTING GRADE
10.p0 ( 100 '3C SHEET PILE WALL 11
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DISTANCE(FEET)
150'SPILLWAWOUTFALL-.
150 SPILL WAYOUTFALL INACTIVE BASIN 3
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V HORIZONTAL:1"=300'
VERTICAL:1"=30'
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