Sand Boxes Going?
Sand-filled gabion baskets line the embankment along Fort Loudoun Dam. TVA is raising the elevation of four of its dams to help reduce the risk of flooding in the event of inclement weather.

TVA details plans for modifying four dams

By Hugh G. Willett knoxnews.com

LOUISVILLE TVA officials met with the public Thursday to detail plans for modifying four area dams to better withstand an historic weather event as residents expressed concern about the impact on their property.

The open house was held at Louisville Town Hall to gather public comments and provide information on a series of proposed modifications to Cherokee, Fort Loudoun, Tellico and Watts Bar dams. The modifications are designed to protect TVA infrastructure, including nuclear power plants, from a probable maximum flood (PMF). Such a flood might occur once every thousand years or more.

TVA is facing a Nuclear Regulatory Commission mandate to provide PMF protection for nuclear plants on the Tennessee River, including the Bellefonte plant in Alabama, which was given a green light for completion by TVA's board in August, said TVA spokesman Bill Sitton.

It was during the recent flood modeling required by NRC for the Bellefonte plant that TVA concluded the local dams were not high enough to prevent overtopping during a PMF.

According to Sitton, options include leaving the "sand baskets" currently providing protection for the dams in place and maintaining them. The baskets, which have been criticized as unsightly since being installed in 2008, can last about five years before replacement, he said.

The second option involves permanent modifications in place of the "sand baskets" with concrete floodwalls and earthen embankments. Such modifications might be constructed by the 2013-2014 timeframe, Sitton said.

A third option includes removing the temporary structures now on the dams and constructing some kind of protective structures elsewhere on the river, perhaps closer to the nuclear plants themselves, he said.

Diagrams of the proposed modifications were available for the public at the Louisville event. Also available were options for public comment that included a comment box for written input, a laptop computer to provide online feedback and a stenographer capable of recording verbal feedback.

TVA will prepare an environmental report on the impact of the proposed solutions later in the fall, followed by another public comment period. TVA will use the information from the environmental report and the public comment to make a decision on the proper course of action in early 2012.

State Senator Randy McNally, R-Oak Ridge, who was at the Louisville event. He said he has been in touch with a group of Tellico Village residents concerned about the TVA proposals.

"I want to make sure they get their questions answered," he said.

The concerns of the Tellico Village residents are primarily focused on the modeling methodology used by TVA, McNally said.

According to Mike Eiffe, a TVA engineer in charge of flood modeling, there is a difference of opinion between his organization and some of the Tellico Village residents regarding how the PMF is calculated.

"They are still dissatisfied with our projections," he said.

Some of those who have complained about the PMF calculations would like to see TVA use a more likely event maybe a 250- or 500-year flood instead of a 1,000- or more year flood to calculate the risk.

By definition, the PMF that TVA has selected has a very little chance of occurring. The parameters for protecting the nuclear plants are set by the NRC, Eiffe said.

"If we can't convince NRC that we can handle such an event, they are going to say turn the lights out," he said. "There is little room for negotiating."

Louisville Alderman Joe Gallagher attended the event because he said many local residents have concerns about whether the TVA dam modifications would affect their lakeside property. He said he was glad to hear that TVA would not raise the water levels in the lake.

"I'm relieved, some residents were afraid this was going to have a dramatic effect on the shoreline," he said.

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