Phase One was considered finished with completion Monday of a “final walkdown of completed repairs and improvements just downstream of the dam,” according to TVA.
Along with drainage improvements in the area, the initial sinkhole discovered in October 2014 has been repaired and a new Control Building parking area is complete.
A piezometer, a device which measures the pressure of groundwater at a specific point, is installed at the site of the sinkhole and will provide continuous monitoring of any additional movement in the area.
The exploratory drilling and grouting program on the earthen embankment continues with the arrival of the first overnight crew Monday night, signaling the beginning of 24-hour-a-day operations.
Shortly after the sinkhole was filled in 2014, 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 in 2015.
A long-term repair plan announced by TVA in late July of last year — 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 that will culminate with construction of a “concrete cutoff wall” within the earthen portion of the dam.
It will include a multi-stage combination of grout injections and concrete.
When completed, the wall 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.