20080915 Ver 2_More Info Received_20100830

Ph Duke
Energy®
August 27, 2010
Mr. Ian McMillan, Acting Supervisor
401 Oversight/Express Review Permitting Unit
North Carolina Division of Water Quality
1650 Mail Service Center
Raleigh, North Carolina 27699-1650
Subject: Bridgewater Hydroelectric Development
Linville Dam ESSI Project
Section 401 Request for Additional Information
DWQ Project # 08-0915
Dear Mr. McMillan:
MAJOR PROJECTS - CAROLINAS
Bridgewater
Project Mailing Address:
5657 Rays Dairy Avenue
Morganton. NC 28655
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DENR - WATFj^i QUALITY
VVETLA.NDS ANDS '-MATER BRANCH
Duke Energy Carolinas, LLC (Duke Energy) is submitting, for your review, the additional
information requested in your June 30, 2010 letter concerning Duke Energy's April 16, 2010
Section 401 Individual Permit (IP) application package. The IP application was submitted for
impacts to jurisdictional waters of the United States, including wetlands, which will be affected
by the Linville Dam Embankment Seismic Stability Improvement Project (ESSI Project).
During the Section 401 IP process, the NC Division of Water Quality (DWQ) determined that
the IP application package was incomplete and/or provided inaccurate information. In the June
30, 2010 letter from DWQ was a list of additional information needed to process the application.
The following are the DWQ's comments and requested information and Duke Energy's
responses:
NCDENR Comment #1: "If there are private mitigation banks with available credit, Duke
Energy will need to use them for mitigation rather than the EEP [N.C. Ecosystem Enhancement
Program]. Please acknowledge that there are no mitigation banks with available credit."
Duke Energy Response: The USACE webpage for Approved Mitigation Banks in North
Carolina (http://www.saw.usace.army.mil/wetlands/mitigation/Banks/index.html) developed by
the USACE Wilmington District was searched for available stream mitigation banks to be used
to offset stream losses associated with the Linville Dam ESSI Project. The webpage reviewed
was last updated by the USACE on 04/15/2010 and it indicated the closest mitigation bank to the
ESSI Project area is Pott Creek Mitigation Bank located near Lincolnton in Lincoln County.
This mitigation bank is a riparian bank located along the South Fork of the Catawba River and
has no stream credits available.
www, d uke-energy. com
NCDENR Comment #2: "The dam work is indeed exempt from Catawba rules, but the
proposed sediment and erosion control measures are not exempt in Zone 1. Additionally, please
provide plans showing where on the site borrow is coming from."
Duke Energy Response: Duke Energy understands that the proposed sediment and erosion
control measures are not exempt in Zone 1. As stated in the IP application, "The temporary
impacts to main stem buffers along the Catawba River are primarily due to the construction of
erosion and sediment control outfall structures. At present, the exact locations of the impacts are
not known due to the lack of an approved erosion and sediment control plan. As stated
previously, due to this project being considered dam maintenance, that causes additional buffer
disturbance beyond the footprint of the existing dam or is not covered under the U.S. Army
Corps of Engineers Nationwide Permit #3, these buffer impacts are considered "Allowable."
This fact was also verified in conversations with the DWQ (A. Chapman, personal
communication, February 16, 2010), which oversees the Catawba River buffer rules (15A NCAC
02B .0243). Therefore, no mitigation for impacts to buffers along the Catawba River main stem
will be necessary." This information was again verified with Ms. Chapman on July 12, 2010,
and she stated that the permit application was correctly prepared for impacts related to Catawba
River buffer rules.
Once the necessary sediment and erosion control plan and the Mining Permit packages are
submitted to the corresponding NCDENR Land Quality Section offices that indicate the location
of the borrow areas, if necessary, a copy of these packages will be submitted to Ms. Chapman of
the DWQ for approval that these impacts are Allowable.
NCDENR Comment #3: "A number of nearby parcels were to be donated to the State [North
Carolina] as compensatory mitigation for the FERC 401 Water Quality Certification for
Catawba-Wateree [Catawba-Wateree Project FERC #2232]. Please acknowledge that the
borrow area is not contained within the afore-mentioned parcels."
Duke Energy Response: In regards to the parcels that are to be donated to the State, Duke
Energy is contractually obligated to transfer to the State of North Carolina, the tracts that are
included in the Catawba-Wateree Comprehensive Relicensing Agreement (CRA). The land
parcels are not included in the CRA as flow mitigation - only the buffer conservation easements
(see CRA Section 4.5). The CRA specifically notes that the North Bend and Paddy Creek tracts
may be used for borrow (see 10.27.3.1, 10.27.3.4). In fact, Duke Energy and NCDENR
personnel have walked the tracts to consult on how to reclaim and re-vegetate these parcels post-
borrow. The Catawba-Linville tract was not mentioned in the CRA as a potential borrow site,
but there is no apparent prohibition stated in the CRA.
In addition to the preceding information, in order to fully meet the State's information needs,
Duke Energy respectfully asks NCDWQ to clarify the interest in these parcels and the parcels'
relationship to the current Water Quality Certification (WQC) application. Borrow on these
parcels will not violate the Catawba-Wateree CRA nor the previously issued WQC (issued
November 2008) and these parcels have not been proposed as mitigation for the instant WQC
application.
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NCDENR Comment #4: "This Office has major concerns about dewatering a mile of the
Catawba River for up to 3 months. Please expand your discussion on this option."
Duke Energy Response: The construction of the Bridgewater Powerhouse is required in order
to make room for the FERC-mandated ESSI improvements via removing the old powerhouse.
The new Bridgewater powerhouse also supports the requirements for continuous minimum flow
and recreation flow in the Bridgewater tailrace as defined in the Comprehensive Relicensing
Agreement (CRA) for the Catawba-Wateree Hydro Project. In addition, the units will be capable
of providing flow aeration to enhance dissolved oxygen levels in the tailrace and Linville River
reach. However, to get the new powerhouse on-line, the tying in of the new penstock is
necessary. This outage of the Bridgewater hydro plant will result in a shutoff of water, both
generation and seepage flows. This temporary outage will result in approximately 4,846 linear
feet (0.92 miles) of the Linville River reach, prior to the confluence of Muddy Creek/Old
Catawba River channel, being shut off from normal flows. This temporary outage is planned to
start around May 27, 2011, and complete within 90 days.
At the beginning of the outage Duke Energy will decrease flows in the Linville River reach by
stepping down the amount of seepage from the powerhouse. This reduction in flows will allow a
majority of the fish in the reach to relocate downstream as the water subsides. Any pools left
after the total reduction of flows will be surveyed for any remaining fish. These fish will be
removed by approved methods (e.g. seining, electroshocking, etc.) and released downstream or
to an appropriate waterbody. These best management practices should avoid any significant
impacts to fisheries within the Linville River reach for the duration of the temporary outage.
Potential impact on aquatic organisms will be lessened if the construction schedule allows the
timing of the outage outside the summer months (July through September). If the outage cannot
be completed outside the summer months, the temperature of the Muddy Creek/Catawba River
channel will be monitored with temperature loggers. If the temperature of the Muddy
Creek/Catawba River was to become critical, Duke Energy will evaluate options of providing
additional water to the Muddy Creek reach.
Duke Energy will make every effort to minimize any potential impacts on aquatic organisms.
As acknowledged in the Individual Permit Application, during this temporary outage, it is
approximated that the Muddy Creek drainage alone will provide at least 51 cubic feet per second
(cfs) to the reach below the confluence of the Linville River and Muddy Creek. This amount
was measured during a flow study that took place in the drought conditions in 2001. During the
outage, additional flows will be provided by utilizing the new minimum flow valve that has been
installed in the Catawba Dam Spillway, which is designed to provide flow into the Catawba
River bypass reach. This valve is designed to provide a maximum of 75 cfs into the bypassed
reach which will provide the additional flows requested.
During the outage, the flow will be monitored at the USGS Calvin Gage (#0213903612) daily
during the outage to document flows. These flow measurements will be forwarded to the
NCWRC on a weekly basis in a report/email that will also include details on the tie-in progress,
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schedule, fish monitoring, and any issues concerning the outage and the aquatic community
downstream of the confluence.
The additional alternatives Duke Energy assessed included:
• Pumping over (State Road 1233) the Linville Dam
This alternative involves the pumping of lake water from Lake James over North Powerhouse
Road (State Road 1233). This alternative would involve the placement of 15 six-inch water
pumps to provide approximately 50 cfs to the Linville River reach. These pumps would have to
run 24 hours a day for the entire length of the outage. With the amount and frequency of
refueling, there is a concern with the possibility of a fuel spill into either Lake James or the
Linville Reach.
Per a similar project where Duke Energy had to provide continuous flows with pumps, the cost
was above $3,000,000. Even if the continuous flows were not necessary, the cost for the
intermittent flows in this case are estimated to probably exceed $2,000,000 due to mobilization,
additional clearing and access work. To place the pumps on a level surface, an area of the
Linville Dam would have to be excavated. The FERC would consider this a dam safety issue
and would not allow this action. In addition, the hoses would have to be either placed across the
road, which would mean a road closure or the pipes would have to be suspended over the
roadway. This would cause a traffic hazard for larger vehicles and the supports would have to be
embedded in the dam, which means the FERC would deem this, too, as a dam safety issue.
• Pumping through the Linville Dam
Similar issues as the Pumping over (State Road 1233) the Linville Dam Alternative, this
alternative would involve the placement of 15 six-inch water pumps that would have to run 24
hours a day for the entire length of the outage. The safety concerns and cost would be
approximately the same as the above alternative. Additionally, this alternative would require
multiple borings through the dam for the placement of the pipes from the pumps under the
roadway from the upstream side of the Linville Dam. The FERC would consider this a dam
safety issue and would not allow this action.
• Flow from Paddy Creek Spillway
This alternative would be to put numerous (approximately 20) large diameter hoses into the lake
and let them gravity feed down the spillway. This alternative would only provide additional
flows into the Muddy Creek Creek/Catawba River channel and not into the Linville River reach
below the Bridgewater powerhouse. The spillway flows directly into the Muddy Creek/Catawba
River channel.
• Pumping from Paddy Creek to Linville Reach
Downstream of Paddy Creek, at a meander bend in the Muddy Creek/Catawba River reach, there
is a topographic break that could be used to pump water from this reach directly into the
proposed affected portions of the Linville River.
This alternative would provide flows by the use of pumping which as noted in above alternatives
has a high safety and environmental risk as well as a high cost. This alternative would only
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provide some flows to less than half the effected reach. If the intermittent flows were used,
when the pumping ceased, a survey for stranded fish would have to be completed every time the
water would drain out of the reach.
Furthermore, per the July 9, 2010 email from Chris Goudreau of the NCWRC, besides the
biological issues noted in the above comment response, pumping large quantities of water [from
Muddy Creek to the Linville River reach] would need to consider the effects of impingement,
entrainment and mortality of organisms.
• Intermittent Flows to Reduce Cost
The use of intermittent flows was brought up by the USACE in place of the continuous flows as
assessed above. The use of intermittent flows would allow fish back into the dewatered reach
that could become stranded once flows were stopped. Therefore, every time the pumping
ceased, a survey for stranded fish would have to be completed. Furthermore, per the July 9,
2010 email from Chris Goudreau of the NCWRC; there could be potentially adverse
physiological and behavioral responses from aquatic species (fish, benthics, and mussels) during
repeated flow fluctuations over an 8 to 12 week period and this intermittent pumping could allow
for repeated exposures to predators.
Duke Energy does not have a choice but to perform this modification under order from the
FERC. Dewatering a section of the stream is indeed a major consequence of this order, and by
choosing the proposed alternative, Duke Energy is taking the necessary precautions to provide
flow, fish refuge, water supply to downstream communities, and also continues to strive to
shorten the duration of flow interruption by doing as much pre-work as possible to prepare for
this stage of construction.
Should you have any questions or comments regarding this letter, please feel free to call me at
[phone] or James A. McRacken of HDRIDTA at [phone].
Sincerely,
9onathan R. Wise
Project Director
Duke Energy
cc: James McRacken - HDRIDTA
Brian Chrisman - HDRIDTA
Kevin Barnett - NCDWQ Asheville
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