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

Grainger, Jefferson, Loudon, Rhea, and Meigs Counties, Tennessee

To enhance flood protection, improve dam stability and meet Nuclear Regulatory Commission requirements, TVA is proposing to make permanent dam safety modifications to its Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams in Tennessee.  In 2009, TVA implemented precautionary measures and installed stone-filled HESCO barriers at the four dams and strengthened the downstream embankment of Watts Bar Dam in order to minimize the potential effect of a Probable Maximum Flood (PMF) event.  The PMF is defined as the flood that may be expected from the most severe combination of critical meteorological and hydrologic conditions that are reasonably possible in a particular drainage area.  Recently updated modeling of flood conditions during a PMF event showed the maximum floodwater elevations are higher than previously calculated.  The proposed dam safety modifications would allow the dams to safely pass the PMF floodwaters and avoid the potential damage to the dams resulting from being overtopped by floodwaters. 

TVA issued a draft environmental impact statement (DEIS) on the proposed dam safety modifications for public review on September 28, 2012.  The DEIS addresses three alternatives.  Under Alternative A, No Action, the approximately 18,000 feet of HESCO barrier floodwalls (7,000 feet at Cherokee, 4,500 feet at Fort Loudoun, 6,000 feet at Tellico, and 1,600 feet at Watts Bar) would remain in place and TVA would maintain them as necessary. Under Alternative B, Permanent Modifications of Dam Structures: Combination of Concrete Floodwalls and Earthen Embankments/Berms, TVA would replace the HESCO barriers with a combination of concrete floodwalls and raised earthen embankments or earthen berms.  Heights of the replacement floodwalls and embankments/berms would range from 2.3 feet at Watts Bar Dam to 6.6 feet at Cherokee Dam.  The use of either floodwalls or embankments/berms at a particular location is dependent on site and engineering constraints.  Floodwalls would be used at five of six locations at Cherokee Dam, all three locations at Fort Loudoun Dam, part of one and all of another of the four locations at Tellico Dam, and none of the four segments at Watts Bar Dam.  Under Alternative C, Permanent Modifications of Dam Structures: All Concrete Floodwalls, TVA would replace the HESCO barriers with concrete floodwalls at all locations.

Public Involvement

TVA published a notice of intent (NOI) to prepare an EIS or an environmental assessment of the proposal in the Federal Register in June 2011; a copy of the NOI is available below.  Public comments were invited on the scope of the project, including alternatives to meet the project need, and environmental issues that should be addressed, from June 14 to September 30, 2011.  Public meetings were held by TVA in July and September 2011.  TVA has considered the numerous comments received during public scoping in designing the alternatives and developing the DEIS.

The DEIS was issued for public review and comment on September 28, 2012.  TVA held a public meeting to accept comments on the DEIS on October 25, 2012 in Lenoir City, Tennessee.  The public comment period closed November 19, 2012.  TVA is now reviewing the comments and preparing the final EIS, which will be issued in early 2013.

Documents

PDF files require Adobe Acrobat Reader.

Notice of Intent (PDF, 193 kb)

Complete Draft Environmental Impact Statement (PDF, 12.6 mb)

Cover, Abstract, and Summary (PDF, 145kb)

Table of Contents (PDF, 188 kmb)

Chapter 1 - Purpose and Need for Action (PDF, 1.1 mb)

Chapter 2 - Alternatives (PDF, 1.4 mb)

Chapter 3 - Affected Environment and Environmental Consequences PDF, 4.5 mb)

Chapter 4 - Cumulative Impacts (PDF, 267 kb)

Chapter 5 - List of Preparers (PDF, 134 kb)

Chapter 6 - DEIS Recipients (PDF, 125 kb)

Chapter 7 - Literature Cited (PDF, 174 kb)

Appendix A - Photo Log (PDF, 3.3 mb)

Appendix B - Consultation Correspondence (PDF, 2.4 mb)

Contact

For further information, contact:

Charles P. Nicholson
Manager, NEPA Compliance
Tennessee Valley Authority
400 W. Summit Hill Drive, WT 11D
Knoxville, TN 37902-1499
(865) 632-3582
cpnicholson@tva.gov