[Federal Register Volume 79, Number 139 (Monday, July 21, 2014)]
[Notices]
[Pages 42393-42394]
From the Federal Register Online via the Government Publishing 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
[email protected].
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 http://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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