Dam Safety Modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams, 42393-42394 [2014-17038]

Agencies

• Tennessee Valley Authority

[Federal Register Volume 79, Number 139 (Monday, July 21, 2014)]
[Notices]
[Pages 42393-42394]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-17038]


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TENNESSEE VALLEY AUTHORITY


Dam Safety Modifications at Cherokee, Fort Loudoun, Tellico, and 
Watts Bar Dams

AGENCY: Tennessee Valley Authority.

ACTION: Amended Record of Decision.

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SUMMARY: The Tennessee Valley Authority (TVA) is amending its July 2, 
2013, Record of Decision (ROD) for the Final Environmental Impact 
Statement for Dam Safety Modifications at Cherokee, Fort Loudoun, 
Tellico, and Watts Bar Dams. In the 2013 ROD, TVA decided to implement 
the dam safety modifications described in the preferred Alternative B, 
Permanent Modifications of Dam Structures: Combination of Concrete 
Floodwalls and Earthen Embankments. Based on the results of subsequent 
engineering and feasibility studies, TVA has revised its approach for 
the permanent modifications to incorporate the use of roller-compacted 
concrete (RCC) at Cherokee and Fort Loudoun Dams and increases in the 
elevations of modifications at Fort Loudoun, Tellico, and Watts Bar 
Dams. In May, 2014, TVA completed a Supplemental Analysis (SA) of the 
potential impacts of the proposed revisions to the dam safety 
modifications. Based on the Final Environmental Impact Statement (EIS) 
and the SA, TVA now amends the July 2013 ROD to incorporate the revised 
approach.

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: This notice is provided in accordance with 
the Council on Environmental Quality's regulations (40 CFR 1500 to 
1508) and TVA's procedures for implementing the National Environmental 
Policy Act (NEPA). 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, and 
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 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 crushed stone on top of the earthen embankments of 
each 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

[[Page 42394]]

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.
    TVA issued the Final EIS for the permanent dam safety modifications 
in May 2013. In the July 2013 ROD, TVA announced its decision to 
implement Alternative B--Permanent Modifications of Dam Structures: 
Combination of Concrete Floodwalls and Earthen Embankments, and has 
begun constructing the permanent modifications.

Supplemental Analysis

    The SA addresses Revised Alternative B--Permanent Modifications of 
Dam Structures: Combination of Concrete Floodwalls, Earthen 
Embankments, and Roller-Compacted Concrete. Under Revised Alternative 
B, TVA would construct the permanent modifications at Cherokee Dam with 
RCC or a combination of RCC and earthen embankment. The 40-foot 
increase in the height of the south spillway training wall and 
associated backfill have been determined to be unnecessary and would 
not be constructed. At Fort Loudoun Dam, TVA would increase the 
elevation of the permanent modifications by 1.0 foot and the 2,600-foot 
FTL-3 concrete floodwall would be replaced with a 1,400-foot section of 
RCC located on the current roadbed of US Highway 321 between the south 
end of the US Highway 321 bridge over Fort Loudoun Dam and the US 
Highway 321--Tellico Parkway intersection. This segment would be 
constructed after the Tennessee Department of Transportation completes 
the new US Highway 321 bridge located downstream of the dam and 
relocates traffic onto the new bridge and connecting roadway. A 250-
foot section of earthen embankment would be constructed near the 
intersection of US Highway 321 and Tellico Parkway. Flood protection in 
the remainder of the original FTL-3 segment would be provided by the 
increased elevation of the reconstructed US Highway 321 and Tellico 
Parkway; the entrance road into the Tellico Recreation Area would be 
modified to match this increased elevation. The elevation of Tellico 
Segment T-1 would be increased by 1.1 foot. The permanent modifications 
to the other segments at Tellico Dam would be the same as described in 
the selected Alternative B. At Watts Bar Dam, the elevation of the 
earthen embankments would be increased by 0.1 foot and the elevation of 
the WB-3 concrete floodwall would be increased by 1.5 foot. TVA is also 
considering increasing the height of the earthen embankments at Watts 
Bar Dam by an additional 1.5 to 2.5 feet, and increasing the height of 
the WB-3 concrete floodwall by 0.5 to 3.5 feet. These proposed actions 
are not among those included in this Record of Decision and are 
currently undergoing additional environmental analyses.
    As described in the SA, available at https://www.tva.com/environment/reports/dam_safety/index.htm, the proposed revisions to 
Alternative B would have no effect on most environmental resources. 
They do have the potential to affect cultural and historic resources, 
transportation, visual resources, recreation, and public safety. TVA 
has determined that these impacts would be short-term and minor and 
similar to or less than the impacts assessed for those resources in the 
Final EIS for Alternative B. Revised Alternative B would result in 
beneficial impacts to transportation at Fort Loudoun and Cherokee Dams 
and to public safety at Fort Loudoun compared to Alternative B due to 
reduced interference with traffic. Revised Alternative B would also 
reduce the impacts to visual resources at Cherokee and Fort Loudoun 
Dams.

Amended Decision

    TVA has decided to implement the Revised Alternative B--Permanent 
Modifications of Dam Structures: Combination of Concrete Floodwalls, 
Earthen Embankments, and Roller-Compacted Concrete. Revised Alternative 
B would result in fewer transportation and public safety impacts and 
minor beneficial impacts to visual resources in comparison to the 
previously selected Alternative B. Revised Alternative B would also 
result in a shorter overall construction period.

Mitigation Measures

    The July 2013 ROD lists mitigation measures associated with the 
selected Alternative B. These mitigation measures remain in effect and 
TVA has not identified the need for additional mitigation measures 
associated with Revised Alternative B.

    Dated: July 7, 2014.
John J. McCormick, Jr.,
Vice President, River Operations.
[FR Doc. 2014-17038 Filed 7-18-14; 8:45 am]
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