Inspecting Chickamauga Dam
HAMILTON CO., Tenn. (WRCB-TV) - The Chickamauga Dam's four hydro-power generators light our homes. Just one of its turbines moves almost 5-and-a-half million gallons of lake water a minute! We tagged along with TVA inspectors for an exclusive look. "Our dams and the communities around our dams are top priority," said TVA Senior Vice President of River Operations john McCormick.
Every day since 1940, spanning more than a mile across the Tennessee River, this dam has held back the waters of Chickamauga Lake. There are seventeen spillways that house enormous steel gates. The top gates each weigh 123,000 lbs., the bottom gates even more. Every now and then they need to be raised and inspected. But, first you have to warn the boaters. A wall of water is about to be released and no matter how well the catfish might be biting, it is good to make tracks. After the blaring siren has sounded and the all-clear is given, a super-duty crane goes into motion. A relatively small amount of water trapped between the two gates is released, giving just a hint of the raw power of the river.
TVA owns 49 dams. They are all monitored, constantly, from headquarters and on-site. Flat panel computers look almost out of place in Chickamauga's 40's era control house. "These structures vary from about 40 to 100 years old and as a result, there is constant repairs and upkeep," explained TVA Dam Safety Officer Mike Scott.
When they get to physically look at the structure, they check for a chemical reaction between the cement and the aggregate causes the dam to swell! "As a result of that," said Scott, "it puts stresses on the concrete. And we go back in and we literally bolt it together to make sure it stays intact."
Construction of the new lock helps relieve some of that pressure, as well. There are simpler problems, too. Like when old logs and debris get caught where they should not be. This happened on our visit and that is when these guys earn their keep. "More than likely with that one we'll use an engineered man basket and lower a guy from here and just have him in that basket, tied-off," said TVA Hydro-Tech Brad Roberson. "He'll reach down and clean it out and we'll lift him right back out."
John McCormick observed, "Somebody asked me once, said, 'Hey, how long does a dam last?' And I didn't have a good answer for them. I have one now. We just celebrated a hundred years at Ocoee. Ocoee 1 is a hundred years old and it's actually in as good a shape today as it was, matter of fact, it's better today than it was a hundred years ago."
The structures are pretty stout, as was demonstrated in October of 2010 when a tornado roared right up the Tennessee and over the Chickamauga Dam. The result was a little debris and some downed traffic lights on the Thrasher Bridge above.
"The number one priority is to have safe facilities for our people, for our employees, for our communities and so," said Mike Scott. "This is the foundation of knowing where we're at."