OAK GROVE, Tenn. (AP) — Lasers have a pretty ominous reputation in popular culture, but at Boone Dam, they serve a decidedly non-destructive purpose.
Specialized robots, or "Boone Bots," are being used to measure minuscule shifts in the dam's foundation. Housed in a small building along the shoreline, the robots shoot small lasers at about 70 targets on and around the structure every hour. These measurements are reviewed by TVA engineers and compared to prior measurements.
To date, the robots have not found anything out of the ordinary, but Tennessee Valley Authority spokesman Jim Hopson said they act as a good precautionary measure in the event work on the Boone Dam embankment causes any changes in the orientation of the structure.
"I think a lot of people forget ... that some of the core borings that we're doing are in excess of 300 feet below the level of the embankment," Hopson said. "There's a lot of geology under there that we have to be concerned about and understanding exactly how everything is working. This laser measurement system allows us to measure infinitesimally small movements that give us a very clear understanding of how the work we're doing today is impacting the stability of the embankment."
Crews are in the process of injecting high- and low-mobility grout into hundreds of holes in the embankment, which will set a sturdy foundation and waterproof the perforations underneath the dam.
"So far, we have not seen anything unexpected, especially as we have started the grouting process itself," Hopson said. "The embankment is very stable, everything looks very good from the testing of this grouting, and that sensor network is part of why we know that everything does look as planned and why we're confident that we're on the right track to correcting this problem."
Hopson said a majority of the sensors were in place within a few months of crews discovering the seepage underneath Boone Dam.
But the Boone Bots are just one of the precautionary measures officials have taken to ensure the repair process does not have a long-lasting, detrimental impact on the lake's facilities or the surrounding ecosystem.
One of those is decidedly less high-tech than robots.
Last year, TVA and the Tennessee Wildlife Resources Agency donated about 500 seedlings to Dennis Scheer, a member of the Boone Watershed Partnership and the Boone Lake Association.
Volunteers planted those seedlings around several local bodies of water, including Beaver Creek, Sinking Creek and Boone Lake, to limit the effect of erosion and create habitats for fish, serving as spawning areas and giving fish a protective place to hide from predators.
According to a weekly update released by TVA on July 19, Scheer reported that the seedlings have had a 90- to 95-percent success rate.
This has been particularly helpful on Boone Lake.
"When we had to lower the lake down to its current levels, we recognized that that exposed a large portion of the bank that isn't traditionally exposed to air," Hopson said, "and when you have that kind of case, you don't have any ground cover, anything on there, you can potentially get erosion."
The Boone Bots have been particularly helpful to engineers during the repair process, providing them with an accurate representation of even the most minute impacts the project could have on the dam.
"Every drill hole that we make, we refine the repair plan a little bit because we're getting real time data from really a three-dimensional view of exactly what the ground is like underneath the embankment," Hopson said.