20031112 Ver 6_More Info Received_20091208

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Draft Minimum Flow Plan
East Fork Hydroelectric Project on the Tuckasegee River
DAFT
(FERC No. 2698)
Prepared for:
DUKE ENERGY
CAROLINAS, LLC
?Duke
rgy.
do December 2008
'Cable of Contents
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TERMS, ABBREVIATIONS, AND ACRONYMS ....
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...................
................................................
1.0 INTRODUCTION
...................................................................,......<.............................................1
2.0 PROJECT DESCRIPTION
........................................................................................................1
3.0 PROJECT OPERATION
............................................................................................................5
3.1 Cedar Cliff Powerhouse Minimum Flow Facility ............
6
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3.1.1 Proposed Operational Changes ...............
............
6
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3.2 Wolf Creek Dam Minimum Flow Facility .................
...............................
3.2.1 Proposed Operational Changes ....................
10
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4.0 SCHEDULE
................................................................................................................................15
5.0 ENVIRONMENTAL CONSIDERATIONS
...................................................... .........16
6.0 CONSULTATION
.....................................................................................................................16
7.0 REFERENCES
........................................................................................................ ..16
C,
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List of Figures
• Figure 1 Project Location Map ......................................................................................................3
Figure 2 East Fork Project Cedar Cliff ..........................................................................................8
Figure 3 Cedar Cliff Minimum Project Conceptual Design Option 1 .........................................1.1.
Figure 4 Cedar Cliff Minimum Flow Conceptual Deisgn Option 2 ............................................12
Figure 5 Wolf Creek Dam Bypass ..............................................................................................13
Figure b Wolf Creek Minimum Flow Conceptual Design ..........................................................14
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Duke Energy Carolinas East Fork Project FERC No. 2698
Minimum Flow Plan
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TERMS, ABBREVIATIONS, AND ACRONYMS
et's cubic feet per second
FERC Federal Energy Regulatory Commission
FSCD First Stage Consultation Document
msl mean seal level
NCDENR-DWQ North Carolina Department of Environment and Natural Resources -
Division of Water Quality
NCDENR-DWR North Carolina Department of Environment and Natural Resources -
Division of Water Resources
NCWRC North Carolina Wildlife Resources Commission
NPDES National Pollution Discharge Elimination System
PLC Programmable logic controller
SA Settlement Agreement
USES United States Forest Service
USFWS United States Fish and Wildlife Service
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Duke Energy Carolinas East Fork Project FERC No. 2698
Minimum Flow Plan
• 1.0 INTRODUCTION
In 2004, Duke Energy (Duke) filed a license application for the East Fork Project with the
Federal :Energy Regulatory Commission (FERC) (Duke Energy 2004). The license application
presented the results of numerous studies of the Nantahala Area Hydroelectric Projects and
proposed new license conditions for the East Fork Project consistent with a negotiated
Settlement Agreement (SA), which was signed on October 29, 2003 by the majority of the
members of the Tuckasegee Cooperative Stakeholder Team (TCST). The SA proposed a
License Article 404 to address minimum flows on the East Fork Hydroelectric Project (Project)
(FERC # 2698) (Duke Energy 2004). 't'his Draft Minimum Flow Plan (Plan) is a description of
proposed plans and/or options for meeting minimum flow requirements for the Project.
Continuous minimum flows will be required in two locations: from the Cedar Cliff
Development Powerhouse into the East Fork Tuckasegee River and from the Wolf Creek Dam
into the Wolf Creek Bypassed Reach. This Plan is an initial summary of how Duke intends to
mcet the minimum flow requirements and takes into consideration the Low Inflow Protocol for
9 the West Fork and East Fork Projects (Duke Energy 2003).
2.4 PROJECT DESCRIPTION
Duke Energy Carolinas, LLC (Duke) owns and operates the Project (Figure 1), located on the
East Fork of the Tuckasegee River in Jackson County, North Carolina. The Project (Project)
consists of three developments; Cedar Cliff, Bear Creek, and Tennessee Creek. The Cedar Cliff
and Bear Creek developments consist of a reservoir, dam, intake, water conveyance, and a
concrete powerhouse containing a single generating unit. The Tennessee Creek Development
consists of two dams and reservoirs, the Tanasee Creek. Dam and the Wolf Creek Dam (Duke
Energy 2004).
There are four separate stream bypassed reaches associated with the Project: Tanasee Creek
Bypassed Reach, Wolf Creek Bypassed Reach, Bear Creek Bypassed Reach, and the Cedar Cliff
Bypassed Reach. The Tanasee Creek Bypassed Reach is approximately 1.5 miles from the dam
to the confluence of Wolf Creek and Tanasee Creek. The Wolf Creek Bypassed Reach is
• approximately 2.1 miles from the base of the dam to the confluence of Wolf Creek and Tanasee
Duke Energy Carolinas East Fork Project FERC No. 2698
Minimum Flow Plan
•
Creek. The Bear Creek Bypassed Reach is approximately 0.3 miles from the base of the dam to
the Bear Creek Powerhouse and the Cedar Cliff Bypassed Reach is approximately 0.4 miles from
the base of the dam to the Cedar Cliff Powerhouse. Combined. for the entire project, the
bypassed reaches total 4.3 miles (Duke Energy 2004).
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East Fork Hydroelectric Project
FERC No. 2698
Figure 1
Project Location Map
December 2008
Source: ESRI 9 2 Dataset Series, 2006
Duke Energy Carolinas East Fork Project FERC No. 2698
Minimum Flow Plan
Cedar Cliff Development
Cedar Cliff Powerhouse is located on the East Fork Tuckasegee River at River Mile 51.9, which
is 2.4 miles upstream of the confluence of the East and West Forks of the Tuckasegee River.
The Cedar Cliff Development consists of a reservoir (Cedar Cliff Lake), a sloping earth core dam
and rockfill embankment 590 ft in length with a maximum height of 173 ft. The dam impounds
the water of the East Fork of the Tuckasegee River near River Mile 52.1. The dam crest is 25 ft
wide and includes a concrete parapet wall along its entire length. A service spillway is
excavated in rock at the right abutment of the dam. Fuse plug crest elevation varies from
elevation 2,331 feet mean sea level (msl) to elevation 2,334 ft msl. Cedar Cliff Lake has a
surf'acc area of 1.21. acres at normal full pond elevation 2,330 ft msl. The reservoir is located on
the East Fork of the Tuckasegee River approximately just upstream of the confluence of the East
and West Forks of the Tuckasegee River. The drainage area of Cedar Cliff Lake is 80.7 square
miles and the average annual flow is approximately 229 cubic feet per second (cfs). The
reservoir is utilized for the production of hydroelectric power and recreational fishing (Duke
Energy 2004).
Bear Creek Development
Bear Creek Dam is located 4.8 miles upstream of the confluence of the East and West Forks of
the Tuckasegee River. The earth-faced rockfill dam is 215 ft high by 760 ft long and impounds
the water in the East Fork of the Tuckasegee River near River Mile 54.5; the nearby powerhouse
is being supplied with water from Bear Creek Lake. The dam crest is 25 ft wide and includes an
870 ft long segmented concrete parapet wall. The spillway from Bear Creek is located on the
right abutment and consists of one radial Tainter gate and two erodible fuse plug sections.
Located on the East Fork of the Tuckasegee River with its headwaters located approximately 200
yards downstream from the Tennessee Creek Powerhouse, Bear Creek Lake has a surface area of
473 acres at Normal Full Pond Elevation 2, 560 feet. (Duke Energy 2004).
Tennessee Creek Development
The Tennessee Creek Development consists of two dams and reservoirs, the Tanasee Creek Dam
and the Wolf Creek Dam. Both dams supply water for hydroelectric generation to the common
• powerhouse (Tennessee Creek Powerhouse) (Duke Energy 2004).
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Duke Energy Carolinas
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Tanasee Creek Dam
East Fork Project FERC No. 2698
Minimum Flow Plan
Tanasee Creek Dam is located 11 miles upstream of the confluence of the East and. West Forks
of the Tuckasegee River. Tanasee Creek Dam is a rockfill dam with a sloping earth core that has
a length of 385 ft, and a maximum height of 140 ft. Approximately 600 ft south of the Tanasee
Creek Dam's left abutment is a 225 ft long and 15 ft high earth and rockfill saddle dam. The
spillway consists of one radial Tainter gate and two erodible fuse plug sections located in a
channel excavated in the right abutment. Tanasee Creek Dam impounds the water in the East
Fork of the Tuckasegee River near River Mile 61.0 with about 968 feet of tunnel that connects to
the tunnel from Wolf Creek Lake. Tanasee Creek Lake has a surface area of 40 acres at Normal
Full Pond Elevation 3,080 ft. (Duke Energy 2004).
Wolf Creek Dam Bypassed Reach
Wolf Creek Dam is located 1.7 miles upstream of the confluence of Wolf Creek and the East
• Fork of the Tuckasegee River. Wolf Creek Dam is a rockfill dam with a sloping earth core that
has a length of 810 ft, and a maximum height of 175 ft. Wolf Creek Dam impounds the water in
Wolf Creek near River Mile 2.0 with about 1,704 feet of tunnel connecting to the tunnel from
Tanasee Creek Lake. The reservoir has a surface area of 176 acres at Normal Full Pond
Elevation 3,080 ft.
3.0 PROJECT OPERATION
Cedar Cliff
As required by the May 5, 1999 Order Approving Settlement and Amending License, a
minimum flow of 10 efs is released from the Cedar Cliff Development into the East Fork
Tuckasegee River. This minimum instantaneous flow is for the protection and enhancement of
fish and wildlife resources, as well as maintenance of water quality. The normal target elevation
for the Cedar Cliff Project is 98 ft on a year round basis (Duke Energy 2004).
Bear Creek
From May 1 to September 1 of each year, Bear Creek Lake level is maintained at or near
Elevation 2,558 ft msl. (USGS). From September 1 to January 1, the reservoir is drawn down to
• elevation 2553.0 ft msl and maintained at that level until March 1 to provide storage for the
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Duke Energy Carolinas East Fork Project FERC No. 2698
Minimum Flow Plan
historically wet period that occurs in the spring. The reservoir is filled from March 1 to May 1
(Duke Energy 2004).
Tennessee Creek
Both Tanasee Creek and the Wolf Creek reservoirs follow the same Normal Target Elevations.
From May 1 to October 1 each year, the reservoirs are maintained at or near Elevation 3,073 tt
msl (USGS). The reservoirs are drawn down to Elevation 3,065 ft tnsl from October 1 to
January 1 and maintained at that elevation until March 1. The reservoirs are filled during the
March to May period.
Day to day operations are based on estimated inflows, Normal Target Elevations, local
recreational needs, and electric system. load and voltage support needs. On a daily basis, the
reservoirs are maintained within a prescribed Normal Operating Range, above or below the
Normal. Target Elevations. All of the generating stations are operated as peaking units under
normal flow and water conditions. If peaking does not maintain the reservoir elevation within
• the normal operating range, the plants are operated for an additional time period at a reduced
load to lower the reservoir elevation. During periods of high inflow and high reservoir elevation,
the plants are operated at maximum load, 24 hours a day to avoid spilling if possible. In general,
during periods of normal inflow, the plants will generate a prescribed number of hours per day to
support electric customer needs and the downstream flow needs in the main stem of the
Tuckasegee River, typically during different periods each day.
Currently, there are no ininimurn flow requirements for the Bear Creek, Cedar Cliff, Tennessee
Creek, or Wolf Creek bypassed reaches.
3.1 Cedar Cliff Powerhouse Minimum Flow Facility
3.1.1. Proposed Operational Changes
Non-generation minimum flow requirements per the SA of 10 efs from December 1 through June
30 and 35 cfs for the remainder of the year will be met by either: (1) constriction of a new
• turbine and powerhouse adjacent to the existing Cedar Cliff Powerhouse or (2) with a
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Duke Energy Carolinas
East Fork Project FERC No. 2698
Minimum Flow Plan
is modification to the existing 10 cfs valve
? (Figure 2), The new minimum flow facility will be able
to pass continuously the anticipated requirement of 10 cfs of water for 7 months (December
through June) of the year and 35 cfs of water for the remaining 5 months (July through
November). Threshold Minimum Flows established in the Low Inflow Protocol would come
into effect during droughts.
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Duke Energy Carolinas East Fork Project FERC No. 269$
Minimum Flow Plan
• Flow requirements may be met by one of two different types of turbines at the Cedar Cliff
Development, The turbines being considered are the Francis reaction type and the Turgo
impulse type. The Turgo turbine will have the ability to operate continuously at a relatively high
efficiency through the wide range of required flow (6 - 35 cfs) (Figure 3). The Francis turbine is
inherently not well suited for operation at the 6 cfs flow and operates with relatively low
efficiency at the 10 cfs flow (Figure 4). Therefore, if the Francis turbine is selected as the best
overall option, a bypass valve will be installed to pass the lower required flows should a drought
situation occur. To ensure that minimum flow requirements are being met, taps will be installed
on either type of generating unit to measure the flow rate and pressure drop through the system.
Likewise, an orifice meter will be installed on the minimum flow valve to monitor the same
parameters should a valve be needed. The data from either the generating units or valve will be
recorded and transmitted to a central programmable logic controller (PLC) where it will be
recorded and stored.
With either option, a small new powerhouse structure will be constructed just outside the
• existing powerhouse, adjacent to the tailrace, to house the new minimum flow unit.
The penstock for the new unit will branch off the main un'it's penstock through an existing
manhole cover. The minimum flow unit's penstock will be 24-inches in diameter. An isolation
valve will be provided at the connection of the minimum flow penstock to the main penstock. A
turbine inlet isolation valve will also be provided to handle emergency shutdown of the
generating unit in case of a load rejection or other problern if the turbine is unable to shut down.
The generating unit will be comprised of a turbine, generator, governor and associated high-
pressure hydraulic system, control panel boards, generator protection relays and metal clad
switchgear. Power output from the generating unit will connect into the existing 480 VAC hydro
station auxiliary power system. Auxiliary power for the new powerhouse structure will be
obtained from the same existing system.

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Duke Energy Carolinas
East Fork Project FERC No. 2698
Minimum Flow Plan
• 3.2 Wolf Creek Dam Minimum Flow Facility
3.2.1 Proposed Operational Changes
The minimum flow requirement of 6 efs per the SA will be met through installation of a
minimum flow release system at Wolf Creek Dam (Figures 5 and 6). This will be accomplished
with a pipe trench with embedded piping in order to convey flow from the intake structure
through the dam.
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Duke Energy Carolinas East Fork Project FEKC No. 2698
Minimum Flow Plan
• A minimum flow intake structure with trash rack will be installed upstream of the dam to limit
the size of passing debris. A valve pit will be excavated from the rock base near the toe of the
fuse plug to provide housing for the actuated V-ball control valve. The valve pit will consist of a
lockable cover for maintenance on the enclosed valve. An isolation valve upstream of the dam
will also be used to discontinue flow for maintenance purposes.
The V-ball control valve will regulate the flow monitored by a magnetic flow tube and flow
transmitter. The magnetic flow tube will be installed upstream of the fuse plug; submerged
under the lake at an elevation of 3060 ft.
Below a pond elevation of 3062.5 ft, flow through the pipe would drop to less than 6 efs. The full
pond elevation is 3080 ft.
The transmitter will be remotely located and hardwired in watertight rigid conduit back to the
gatehouse to provide data to the monitoring box. The monitoring box will store flow rate data
for specific periods of time and will provide a continuous readout of flow.
In order to install the minimum flow release system, the existing fuse plug that is located at the
center of the dam will be removed. The fuse plug will be rebuilt upon completion of the project.
The engineering concepts presented in this Minimum Flow Plan may need to be modified
subsequent to further engineering discussions and agency consultations.
4.4 SCHEDULE
The continuous minimum flow requirements for the Project were negotiated and proposed to the
FERC in the SA (Duke Energy 2003), which was filed with FERC on January 8, 2004. Proposed
License Article 404 in the SA contains the negotiated minimum flows for the Project along with
a proposed implementation schedule, as follows: Within 6 months of license acceptance, Duke
will file the Plan for FERC approval to modify the Project facilities as outlined in the Plan. This
filing will take place after consultation with the North Carolina Wildlife Resources Commission
• (NCWRC), North Carolina Department of Environment and Natural Resources - Division of
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Duke Energy Carolinas East Fork Project FERC No. 2698
Minimum Flow Plan
• Water Resources (NCDENR-DWR), North Carolina Department Environment and Natural
Resources - Division of Water Quality (NCDENR-DWQ), United States Fish and Wildlife
Service (USFWS), and the United States Forest Service (USFS). Within. one year following
FERC approval of the Plan, Duke will complete the modifications of Project facilities identified
in the Plan and begin providing the minimum flows as specified in Article 404. Duke will
calibrate the flow measurement devices within 60 days following installation and at least once
every two years thereafter.
5.0 ENVIRONMENTAL CONSIDERATIONS
Water quality and other environmental effects of these modifications were considered in the
preceding Section 401 Water Quality Certification. Application fbr the East Fork Project. None
of these proposed modifications will degrade water quality. The modifications will also provide
enhanced aquatic habitat in the East Fork Tuckasegee River and the Wolf Creek Bypassed
Reach. The proposed operational changes will have no impacts any Rare Threatened or
• Endangered (RTE) species documented in the Project area.
Construction associated with the minimum flow release structures will occur in previously
disturbed areas that are immediately adjacent to the existing flow release structures. Project
modifications are not anticipated to adversely affect the cultural or recreational resources within
the Project boundary. Duke will obtain all necessary environmental permits prior to
commencing with Project modifications.
6.0 CONSULTATION
To be inserted upon agency consultation
7.0 REFERENCES
Duke Energy Corporation. 2003. East Fork. Tuckasegee River Hydroelectric Projects FERC
#2686 and #2698 Settlement Agreement Notebook.
•
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Duke Energy Carolinas
East Fork Project FERC No. 2698
Minimum Flow Plan
• , 2004. East Fork Tuckasegee River Hydroelectric Project FERC #2698 License
Application Volume I.
2004. West Fork Tuckasegee River Hydroelectric Projects FERC #2686 Final. License
Application.
2006. Preliminary Final Environmental Assessment For Hydropower Licenses Nantahala
East Projects.
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