Crews prepare to construct cut-off wall at Boone Dam

David Floyd • May 18, 2019 at 12:28 AM

After about a million hours of work on site, crews are getting ready to begin a major part of the Boone Dam project: Building an underground concrete wall along the dam’s embankment.

“We know it’s been a lengthy project, but now there’s a very clear and defined endpoint in sight,” said TVA spokesperson Mary Ellen Miller, “and it is on the schedule that we promised all along.”

Sam Vinson, the principal manager for the Boone Dam project, said that, once complete, the wall will be made up of a line of tightly packed concrete columns that will be embedded in the ground. The wall is designed to stop erosion along the earthen embankment, which is adjacent to the dam, by blocking water seepage.

Crews are drilling holes along the embankment, and Vinson said workers will begin pouring concrete next week. Construction should last about two years.

The TVA expects the project will be complete in July 2022, which is within the five-to-seven-year timeframe the organization anticipated.

To get to this point, Miller said planners had to put in a lot of infrastructure, including a waste water treatment plant and an onsite concrete batch plant, which allows crews to produce concrete without relying on an outside facility.

“If we need concrete at 2 a.m. on Saturday morning, we don’t have to try to find the concrete,” Vinson said. He said crews will remove the facilities once the project is done.

Vinson said once crews finish construction, the TVA will raise reservoir levels to test the repairs, which will likely occur in spring or summer of 2021. “We may bring the reservoir up, hold it at some elevation for a few weeks to get data,” he said. “We can’t guarantee that it may not go down a little bit or even progress up a little bit.”

Miller said the TVA has not decided how much the water level will change or how long it will stay at adjusted levels, but she noted that the organization tries to give the public a 60-day notice before they change the water level. During repairs, TVA has tried to keep the water level between 1,350 and 1,355 feet — roughly 30 feet lower than its normal summer lake level of 1,382 feet.

In October 2014, the TVA discovered a sinkhole near the base of the Boone Dam embankment. In an effort to combat erosion and seepage along the earthen embankment, the TVA began a seven-year repair process that required the agency to lower the water level. To set a foundation for the concrete wall, and plug some gaps in the earthen layer, crews have injected grout mixtures into the embankment.

Clearing vegetation

In response to concerns from homeowners along the reservoir, TVA is also in the process of mulching more than 600 acres of vegetation on land that was exposed when water levels dropped.

The TVA isolated about 500 acres of land that needed to be cleared of vegetation, and members of the public identified an additional 100 acres that the organization added to its tally. Vinson said the money for this program comes from a different source than the budget for the Boone Dam repairs.

The TVA is now about halfway through the process, and Miller said the organization plans to have all 600 acres cut by the fall. “It’s not part of construction,” Miller said. “However ... we cared about what our neighbors said. We want to be a good neighbor here, so that’s why we moved forward on it.”

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