[Federal Register Volume 76, Number 114 (Tuesday, June 14, 2011)]
[Notices]
[Pages 34799-34801]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-14637]


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TENNESSEE VALLEY AUTHORITY


Permanent Dam Safety Modification at Cherokee, Fort Loudoun, 
Tellico, and Watts Bar Dams, TN

AGENCY: Tennessee Valley Authority.

ACTION: Notice of intent.

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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 
Tennessee Valley Authority's (TVA) procedures for implementing the 
National Environmental Policy Act (NEPA). TVA will prepare an 
environmental review (in the form of an environmental assessment [EA] 
or an environmental impact statement [EIS]) to address the potential 
impacts to the natural, physical, and human environment resulting from 
various alternatives for permanent modifications to the existing dam 
facilities at Cherokee, Fort Loudoun, Tellico, and Watts Bar dams in 
Tennessee. The level of review will be determined after the public 
scoping process has been completed. TVA is evaluating long-term 
permanent solutions for dam safety modifications to replace interim 
modifications that were implemented at the dams.

DATES: To ensure consideration, comments on the scope of the 
environmental issues must be postmarked or e-mailed no later than 
August 5, 2011. When a draft environmental review (either an EA or EIS) 
is prepared, it will be made available for public review.

[[Page 34800]]


ADDRESSES: Written comments should be sent to Kenneth P. Parr, NEPA 
Specialist, NEPA Compliance, Environmental Permits and Compliance, 
Tennessee Valley Authority, 1101 Market Street (LP 5U), Chattanooga, 
Tennessee 37402-2801. Comments may be e-mailed to [email protected], 
submitted by fax to 423-751-3230, or entered online at http//
www.tva.com/environment/reports/index.htm.

FOR FURTHER INFORMATION CONTACT: David Lane, Environmental Engineer, 
Tennessee Valley Authority, 400 West Summit Hill Drive (GRN 2E), 
Knoxville, Tennessee, 37902-1499; e-mail: [email protected].

SUPPLEMENTARY INFORMATION:

Background

    TVA evaluates its dam safety program regularly (especially as 
technology and standards evolve and when more or better data become 
available) and modifies its dams as needed to ensure the structural 
integrity of TVA dams and the safety of the public. Periodic updates 
regarding maximum flood conditions are conducted when parameters used 
in flood modeling change, e.g., probable maximum precipitation or river 
operation guidelines. TVA assumes the most extreme weather event 
reasonably possible when determining maximum flood conditions of the 
river system. TVA's most recent probable maximum flood calculations 
indicate that a worst-case winter storm could cause water to go over 
the top of some dams even with the floodgates wide open, possibly 
causing dam failure. Failure of any dam would result in loss of stored 
water for navigation, impacts to fish and wildlife resources, loss of 
recreational opportunities, and possible property damage, personal 
injury, and loss of life. Failure also could result in failures to 
downstream dams.
    To minimize the potential effects of a severe flooding event 
predicted by revised probable maximum flood modeling, precautionary 
measures have been implemented on top of the earth embankments at four 
(Cherokee, Fort Loudoun, Tellico, and Watts Bar) dams. These measures 
included raising dam elevations about 3 to 4 feet by placing 
interconnected, fabric-lined, sand-filled HESCO containers in order to 
safely pass predicted worst-case floodwaters, to avoid dam overtopping 
and possible impacts to the downstream embankment, and to provide 
additional floodwater storage capacity. The downstream embankment of 
Watts Bar Dam has also been strengthened with concrete matting.
    TVA must now develop permanent solutions for the precautionary 
measures that were put in place to correct safety deficiencies 
identified at Cherokee, Fort Loudoun, Tellico and Watts Bar dams. The 
need for the proposed action is to prevent the impacts associated with 
dam failure. TVA has developed alternatives that consider the level of 
risk reduction to the public, constructability, potential environmental 
impacts, and cost.

Proposed Alternatives

    TVA has performed preliminary internal scoping and identified a No 
Action Alternative and two Action Alternatives: permanent modifications 
to dam structures and removal of the temporary HESCO baskets before the 
end of their useful life.
    The No Action Alternative is the current existing condition at the 
Cherokee, Fort Loudoun, Tellico, and Watts Bar dam sites. A permanent 
concrete mat structure has been installed in the downstream embankment 
of Watts Bar Dam, and HESCO baskets have been installed at Cherokee, 
Fort Loudoun, Tellico, and Watts Bar dams. These items would remain in 
place and would be maintained as needed. These temporary measures were 
installed to prevent floodwaters from potentially overtopping the dams 
and to ensure the integrity of the downstream embankments, thus 
increasing the public safety of downstream residents and the safety of 
TVA's critical nuclear facility operations.
    Under the first Action Alternative, the HESCO baskets would be 
replaced, and permanent dam modifications would be made to each of the 
four dam structures. The potential modifications could include 
construction of concrete floodwalls, raising of earth embankments, or a 
combination of floodwalls and raised earth embankments. The permanent 
concrete mat structure in the downstream embankment of Watts Bar Dam 
would remain in place. Under this alternative, the potential for 
overtopping of the dams during a probable maximum flood event would be 
prevented. This would ensure that the integrity of the downstream 
embankments would be maintained and thereby increase the public safety 
of downstream residents and the safety of TVA's critical nuclear 
facilities.
    Under the second Action Alternative, TVA would consider removal of 
the temporary HESCO baskets from the dam structures before the end of 
their useful life. The permanent concrete mat structure installed in 
the downstream embankment of Watts Bar Dam would remain. This 
alternative is similar to the situation at the dams prior to placing 
the HESCO baskets on the dams as an interim solution for management of 
the potential maximum flood events. Under this alternative, overtopping 
of the dams would be possible during a very low-risk probable maximum 
flood event. The downstream integrity of the dam embankments could be 
compromised, thus jeopardizing the public safety of downstream 
residents and the safety of TVA's critical facilities. The analysis of 
this alternative would contain a discussion/justification regarding the 
reasons for placing the baskets on top of the dams to address this low-
risk event.

Proposed Issues To Be Addressed

    The environmental review will contain descriptions of the existing 
environmental and socioeconomic resources within the area that would be 
affected by construction, operation, and maintenance of the proposed 
permanent dam modifications. Evaluation of potential environmental 
impacts to these resources will include, but will not necessarily be 
limited to, the potential impacts on water quality, aquatic and 
terrestrial ecology, endangered and threatened species, wetlands, 
aesthetics and visual resources, recreation, land use, historic and 
archaeological resources, and socioeconomic resources. The need and 
purpose of the project will be described. The final range of issues to 
be addressed in the environmental review will be determined, in part, 
from scoping comments. The preliminary identification of reasonable 
alternatives and environmental issues in this notice is not meant to be 
exhaustive or final.

Public and Agency Participation

    The environmental review is being prepared to inform decision 
makers and the public about the potential environmental effects of 
TVA's options for minimizing the potential effects of a severe flooding 
event predicted by revised probable maximum flood modeling. The draft 
EA or EIS is anticipated to be available in late summer 2011. Any 
changes to this schedule will be posted on the TVA Web site: http://www.tva.com/environment/reports/index.htm. The environmental review 
process will also serve to inform the public and the decision makers of 
the reasonable measures that would be implemented to minimize adverse 
impacts. Other Federal, state, and local agencies and governmental 
entities are invited to provide scoping comments. These agencies 
include, but are not limited to,

[[Page 34801]]

the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, 
Tennessee Department of Environment and Conservation, and the Tennessee 
State Historic Preservation Officer.
    The public is invited to submit comments on the scope of the 
environmental review no later than the date given under the DATES 
section of this notice. TVA will conduct an additional public review 
after the draft EA or EIS is prepared.

    Dated: June 8, 2011.
Anda A. Ray,
Senior Vice President, Environment and Technology.
[FR Doc. 2011-14637 Filed 6-13-11; 8:45 am]
BILLING CODE 8120-08-P