Dam Safety Modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams, 53494-53496 [2013-21134]

Agencies

• Tennessee Valley Authority

[Federal Register Volume 78, Number 168 (Thursday, August 29, 2013)]
[Notices]
[Pages 53494-53496]
From the Federal Register Online via the Government Printing 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 
cpnicholson@tva.gov.

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