[Federal Register Volume 78, Number 168 (Thursday, August 29, 2013)]
[Notices]
[Pages 53494-53496]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-21134]
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TENNESSEE VALLEY AUTHORITY
Dam Safety Modifications at Cherokee, Fort Loudoun, Tellico, and
Watts Bar Dams
AGENCY: Tennessee Valley Authority.
ACTION: Issuance of Record of Decision.
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SUMMARY: This notice is provided in accordance with the Council on
Environmental Quality's regulations (40 CFR parts 1500 to 1508) and
TVA's procedures for implementing the National Environmental Policy Act
(NEPA). TVA has decided to adopt the preferred alternative in its final
environmental impact statement (EIS) for the dam safety modifications
at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams. The notice of
availability (NOA) of the Final Environmental Impact Statement for Dam
Safety Modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar
Dams was published in the Federal Register on May 31, 2013. This
alternative, Permanent Modifications of Dam Structures: Combination of
Concrete Floodwalls and Earthen Embankments, will protect the four dams
against failure during the Probable Maximum Flood (PMF) event while
minimizing the adverse effects to the appearance and recreational use
of the dam reservations.
FOR FURTHER INFORMATION CONTACT: Charles P. Nicholson, NEPA Compliance
Manager, Tennessee Valley Authority, 400 West Summit Hill Drive, WT
11D, Knoxville, Tennessee 37902-1499; telephone 865-632-3582, or email
[email protected].
SUPPLEMENTARY INFORMATION: TVA is an agency and instrumentality of the
United States, established by an act of Congress in 1933, to foster the
social and economic welfare of the people of the Tennessee Valley
region and to promote the proper use and conservation of the region's
natural resources. A fundamental part of this mission was the
construction and operation of an integrated system of dams and
reservoirs. As directed by the TVA Act, TVA uses this system to manage
the water resources of the Tennessee River for the purposes of
navigation, flood control, power production. Consistent with these
purposes, TVA operates the system to provide a wide range of other
benefits.
As the Federal agency responsible for the operation of numerous
dams, and consistent with the Federal Guidelines for Dam Safety issued
by the Federal Emergency Management Agency, TVA prepares for the worst
case flooding event in order to protect against dam failure, loss of
life, major property damage, and impacts to critical facilities. This
worst case flooding event is known as the PMF, defined as the flood
that may be expected from the most severe combination of critical
meteorological and hydrological conditions that are reasonably possible
in a particular area. Nuclear Regulatory Commission (NRC) nuclear plant
operating regulations also require that nuclear plants be protected
against the adverse effects of the PMF. TVA periodically reviews and
revises its calculations of PMF elevations. During the most recent
review (completed in 2008), TVA determined that the updated PMF
elevations at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams, as
well as at TVA's Watts Bar and
[[Page 53495]]
Sequoyah Nuclear Plants, were higher than previously calculated.
The differences in PMF elevations are sufficient to indicate that a
PMF event could cause water to flow over the top of the dams, even with
the floodgates wide open, possibly resulting in dam failure. Failure of
one or more of these dams would result in extensive damage to
buildings, infrastructure, property, and natural resources, as well as
potential personal injury and loss of life.
In 2009, TVA implemented temporary measures at the four dams to
remain consistent with Federal guidelines and to comply with nuclear
operating regulations for safe operations of the river and reservoir
system, and to minimize the potential effects of the PMF. These
temporary measures consisted of raising the heights of the four dams by
installing interconnected, fabric lined HESCO Concertainer[supreg]
units filled with No. 10 crushed stone on top of the earthen
embankments of each dam. These HESCO barriers raised the height of each
dam by 3 to 8 feet and provided additional floodwater storage capacity.
The length of the HESCO barrier floodwalls totaled approximately 19,100
feet (7,000 feet at Cherokee; 4,500 feet at Fort Loudoun; 6,000 feet at
Tellico; and 1,600 feet at Watts Bar). TVA also installed a permanent
concrete apron on approximately 2 acres of the downstream earthen
embankment of Watts Bar Dam.
In a January 25, 2012 letter from NRC to TVA, NRC stated that the
HESCO barriers were not capable of resisting impacts from large debris
during a flood and are not acceptable as a long-term solution to
protecting the dams, and downstream nuclear plants, during the PMF. At
the time the NRC letter was received, TVA had not made any decisions
about whether or how to replace the HESCO barriers. After receiving the
letter, TVA made the commitment to NRC to develop and implement
permanent dam safety modifications to replace the temporary measures at
the four dams.
Alternatives Considered
TVA considered three alternatives in the Draft EIS and the Final
EIS. These alternatives are:
Alternative A--No Action. TVA would leave the HESCO barriers in
place and replace or maintain them as necessary. The major maintenance
activity would be the replacement of the geotextile liners on
approximately five-year cycles. This would require removing the crushed
stone from the containers, removing and replacing the liners, and then
refilling the containers with the previously used crushed stone. The
HESCO barriers would continue to minimize the potential for failure of
the four dams and prevent an increase in flooding at downstream
locations, including TVA's nuclear plants, during the PMF. As stated in
the above-mentioned NRC letter, this is not a long-term solution
acceptable to NRC. It does, however, represent the current baseline
conditions and is therefore the appropriate No Action alternative.
Alternative B--Permanent Modifications of Dam Structures:
Combination of Concrete Floodwalls and Earthen Embankments. TVA would
raise the heights of the dams as follows: Cherokee--6.6 feet; Fort
Loudoun--4.8 to 6.0 feet; Tellico--4.8 feet, and Watts Bar--3.5 feet.
These heights are approximately two feet greater than the PMF
elevations because of the need to maintain adequate freeboard to
minimize overtopping by waves. The length of floodwall and raised
earthen embankment at each dam would be as follows: Cherokee--5,300
feet of floodwall and 3,150 feet of embankment; Fort Loudoun--3,800
feet of floodwall and 250 feet of embankment; Tellico--3,400 feet of
floodwall and 2,450 feet of embankment; and Watts Bar--1,650 feet of
embankment. At Cherokee, TVA would also install about 40 post-tensioned
anchors into the concrete portion of the dam, construct a 13.6-foot
tall concrete floodwall on a 93-foot section of the dam, and raise the
height of a 400-foot long section of the south spillway training wall
by up to 40 feet. At Watts Bar, TVA would also strengthen an existing
concrete floodwall on the east end of the dam. TVA identified
Alternative B as its preferred alternative in both the Draft EIS and
Final EIS.
Alternative C--Permanent Modification of Dam Structures: All
Concrete Floodwalls. TVA would replace the HESCO barriers with concrete
floodwalls in approximately the same locations. The heights of the
floodwalls would be the same as the permanent modifications proposed
under Alternative B. The additional modifications to Cherokee and Watts
Bar dams described under Alternative B would be implemented under
Alternative C.
Public Involvement
TVA published a notice of intent to prepare the EIS in the Federal
Register on June 14, 2011. TVA sought input from Federal and state
agencies, Federally recognized Indian tribes, local organizations and
individuals during the 55-day public scoping period. Open house
meetings were held in Lenoir City and Louisville, Tennessee. TVA
received a total of 248 scoping comment letters; primary topics
included impacts to scenery, land use, and recreation at the dams; the
methodology used to calculate the PMF; and alternatives to the proposed
permanent dam modifications.
The notice of availability (NOA) of the Draft EIS was published in
the Federal Register on September 28, 2012. TVA held a public meeting
on the Draft EIS on October 22, 2012 and accepted comments until
November 19, 2012. TVA received 21 comment submissions on the Draft
EIS, and the Final EIS contains responses to these comments. After
considering the comments and the results of additional engineering
studies conducted after publication of the Draft EIS, TVA made several
modifications to Alternative B. These modifications included the use of
earthen embankments in place of some segments of concrete floodwalls at
Cherokee and Fort Loudoun. Earthen embankments would also be
constructed at several segments at Cherokee, Tellico, and Watts Bar
Dams identified in the Draft EIS as suitable for either floodwalls or
embankments. The increased use of earthen embankments would reduce the
visual impacts of floodwalls and restrictions on recreational use of
the dam reservations. It would also eliminate the need for gap closure
barriers between segments of floodwalls. An additional modification to
Alternative B is the elevation of the surface of roadways adjacent to
floodwall segments on saddle dams at Cherokee and Tellico. This measure
would reduce the effective height of the floodwalls for recreational
users walking the roads and eliminate obstructions to their views of
the reservoirs.
The NOA for the Final EIS was published in the Federal Register on
May 31, 2013.
Environmentally Preferred Alternative
Alternative A--No Action would likely result in the lowest level of
environmental impacts. The construction-related impacts resulting from
the two action alternatives, Alternatives B and C, would be largely
avoided. The current adverse impacts to visual resources and
recreational use of the dam reservations would continue. Of the two
action alternatives, Alternative B would result in greater impacts
during construction but reduced long-term impacts. Based on
consideration of the overall impacts, the difference between the two
action alternatives is small and Alternative B is
[[Page 53496]]
environmentally preferable over Alternative C.
Decision
TVA has decided to implement the preferred alternative identified
in the Final EIS, Alternative B--Permanent Modifications of Dam
Structures: Combination of Concrete Floodwalls and Earthen Embankments.
This alternative was selected over Alternative C--Permanent
Modification of Dam Structures: All Concrete Floodwalls because of the
reduced long-term impacts and slightly lower construction costs.
Alternative B also eliminates the need for gap closure barriers between
floodwall segments.
Mitigation Measures
TVA would use appropriate best management practices during all
phases of construction and maintenance associated with the proposed
action. TVA would also establish the necessary traffic controls such as
use of warning signs, flagmen, and lane closures during construction
and maintenance activities in order to minimize traffic and safety
impacts. In order to minimize impacts to potential habitat for the
endangered Indiana bat, TVA would comply with the terms of the
Memorandum of Agreement with the U.S. Fish and Wildlife Service. These
terms include delaying the removal of suitable roost trees where
feasible until after July 31, surveying for the presence of the bats
before removing suitable roost trees prior to July 31, and the
mitigation payment of $13,986 to the Indiana Bat Conservation Fund.
Dated: July 2, 2013.
John J. McCormick, Jr.,
Senior Vice President, River Operations & Renewables.
[FR Doc. 2013-21134 Filed 8-28-13; 8:45 am]
BILLING CODE 8120-08-P