The need to address problems with recurrent sediment seepage at Boone Dam will keep water levels in Boone Lake below winter drawdown levels for the foreseeable future, according to John McCormick, TVA Vice President of Safety, River Management and Environment.

Problems became apparent shortly after a sinkhole was discovered and fixed near the base of the embankment in October 2014, McCormick said, when water and sediment were found seeping from the riverbank below the dam.

“Sinkholes are not uncommon,” he said. “Seepage into the waterways is uncommon.”

TVA lowered the lake 10 feet below normal winter levels as it investigated the cause of the seepage. Initial results indicate that erosion may be occurring within the foundation of the earthen embankment at normal lake levels. Without correcting the issue, raising the level of the lake could potentially increase the rate of erosion.

The erosion within the foundation can be attributed to the geological structure within the foundation, McCormick said.

“Karst foundations is something that we have experience with,” he said. “All of East Tennessee is very heavy in karst foundations.

Karst topography is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes, dolines, and caves.

“In East Tennessee, it is commonly limestone,” McCormick said. “Limestone, as it starts to dissolve, it creates voids and those voids cause sinkholes.”

As water begins to flow through these voids, it causes further erosion which compounds the problem, he said.

“We detected this issue early, but it’s important that we take the proper steps now to prevent the possibility of more damage,” added McCormick. “The lake will remain at the current level or lower for at least the next year as we take the first steps in our repair work.”

Lowering the water level was the “first significant intervention” for the problem, McCormick said, adding that lowering the water level relieved pressure on the dam. The normal winter draw down level for Boone Lake is measured at 1,362 feet above sea level while the normal summer level is 1,382 feet above sea level, McCormick said.

“Currently we are operating between 1,350 and 1,355 depending on rainfall and what is going on upstream,” McCormick said.

Work is expected to begin this spring on using grout to improve conditions underneath the earthen embankment.

“We will be drilling down through the earthen dam and injecting that grout into those voids,” McCormick said, adding the grout being used is the same as material found in the foundations of most homes.

“This process is not an easy process because we are dealing with what is below the dam itself,” McCormick said. “The dam itself is very robust, we see no soft spots, no water. It is what is under the surface of the dam that is giving us alarm.”

“This process is a long process,” he added. “It is not something we can do overnight.”

At the same time, TVA engineers and industry experts will continue their work to determine the best permanent repair and analyze how lake levels will be impacted during construction.

“Our engineers and experts, who are some of the best in the country, are working with independent industry leaders to determine the best long-term repair options for the earthen embankment,” McCormick said. Because seepage is an “uncommon problem,” the TVA has enlisted the help of nationally known experts from outside the agency to help them investigate and handle the problem.

“The safety of downstream communities, industries, the public and our employees is our top priority,” McCormick said. “Boone Lake is an important part of the recreational and economic fabric of the area and we recognize the impact of keeping the lake low through the all-important summer months.”

While Boone Lake and the communities around it will be impacted, TVA officials say they do not believe the lowered level of that lake and work on the dam will affect other TVA managed lakes or the operations of other TVA dams in the area. That includes water levels at Watauga Lake and operations at Wilbur Dam.

“We don’t believe there will be any impact,” TVA spokesperson Gail Rymer said. “TVA’s River Operations team has evaluated the requirements at our dams and believe we can maintain the water flows while Boone Lake levels are down.”

Even though the water levels on Boone Lake will be held significantly lower, the lake will remain open for recreation but TVA recommends using extra caution

Boaters should use caution while operating on Boone Lake because of the lower-than-normal water levels. Even seasoned boaters familiar with Boone can get into an unsafe situation from shallow, underwater hazards like rocks, stumps and debris.

“We certainly want to encourage those hardy anglers who like fishing this time of year to take advantage of Boone Lake and all of the area lakes and rivers,” said Rebecca Tolene, vice president of Natural Resources. “Just be sure to be safe, always wear a life jacket and be extra careful on Boone because of the below normal water level.”

As TVA moves forward with work with repairs and planning, McCormick said the agency wants to work with the community and keep them informed of progress. A community Open House will be held March 10 at Daniel Boone High School in Gray, from 5-8 p.m. to provide information on the Boone Dam project.

The TVA also reminds the public that it is illegal to remove, disturb, dig or damage historical or cultural artifacts on federal property, including items exposed on land normally covered by water. The public is asked to leave such materials in place and report anyone digging for artifacts to 1-855-476-2489.

TVA’s website will provide up-to-date information about the Boone Dam project and current lake level information at www.tva.gov/boonedrawdown.