Tennessee Valley Authority has arrived at a proposed repair project to correct water seepage and erosion at Boone Dam.
TVA engineers and other dam safety experts are recommending the construction of a composite seepage barrier inside the earthen embankment portion, which has been experiencing the seepage and erosion. This barrier would involve a multi-stage combination of grout injections and concrete.
“The proposed composite seepage barrier should prevent further erosion and we are confident will provide the most robust, long-lasting repair,” said John McCormick, vice president of safety, river management and environment with TVA.
The initial cost estimate for the repair is $200 million to $300 million, and it is expected to take five to seven years to complete.
Preliminary testing and site preparation work is already under way.
Seepage under the embankment was discovered in October 2014, in the form of a sinkhole at the base of the structure. The sinkhole was repaired but a few days later seepage was discovered near the location of the original sinkhole. A thorough investigation revealed a complex series of underground geological pathways allowing water from both upstream and downstream sources to cause internal erosion. If left uncorrected, the erosion could eventually lead to failure of the dam.
Boone Dam is 160 feet high and 1,532 feet long and impounds water for an 89-MW hydroelectric powerhouse.
The public will have the opportunity to comment on the proposal during a formal environmental review process scheduled for later this year, as well as during public meetings in the community.
TVA is a corporate agency of the U.S. that provides electricity for business customers and local power distributors serving 9 million people in parts of seven southeastern states.