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TVA: Boone Dam repairs on track for completion in 3-5 years

J. H. Osborne • Updated Jun 12, 2017 at 9:14 AM

BLOUNTVILLE — Tennessee Valley Authority officials released a “Boone Lake update” last week to report the agency’s long-term repair of Boone Dam is on track for completion between 2020 and 2022.

That’s within the time frame TVA officials estimated the project would take to complete when the repair plan was first made public about two years ago.

In last week’s update, TVA touted the following accomplishments since work began:

In December 2015, drill rigs went up on the dam and the following has been accomplished:

— Total man-hours: 649,036

— Low mobility grout (LMG) holes drilled and grouted: 539

— High mobility grout (HMG) holes drilled and grouted: 261

— Total drilling footage: 113,511 linear feet or 21.51 miles

— Total Grout Placed: 2,388 cubic yards or 239 average concrete truck loads

The LMG and HMG holes were drilled and grouted in order to fill voids within the earthen embankment.

Current status: The Boone Dam seepage remediation project remains on track for completion between 2020-2022. We’ve made some timeline modifications to move the berm construction forward in the schedule. At this time, we continue to evaluate the performance of the grouting work to ensure its effectiveness.

Next steps: During the summer, TVA will be constructing the upstream berm. This work will be visible to residents and there may be additional truck traffic due to rocks being carried for the new buttress. The berm will provide additional stability for the earthen embankment.

A sinkhole occurred in a non-public parking area on the downstream side of Boone Dam in October 2014. It was filled. Shortly afterward, sediment-filled seepage was discovered on the riverbank downstream of the dam.

That’s when TVA announced a quicker-than-usual drawdown to winter levels. Citing safety concerns and continuing work to solve the seepage issue, TVA later announced the lake’s level would not be raised unitl the seepage problem was solved long-term.

A long-term repair plan announced by TVA in late July 2015 — with an estimated completion time of five to seven years and a price tag of $200 million to $300 million — calls for a three-phased repair culminating with construction of a “concrete cutoff wall” within the earthen portion of the dam.

When completed, it will be several feet thick, extend underground as much as 250 feet, and run the entire length of the crescent-shaped earthen section — from the concrete section of the dam to the parking lot near the beach area.

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