After first receiving authorization from Congress more than 20 years ago, a now nearly $1 billion replacement to the Chickamauga lock could be operational in November 2027.
The lock at Chickamauga Dam is a chamber used to raise or lower vessels between different water levels on the Tennessee River.
Aiming to fix structural issues with the facility and ensure quicker, more fluid movement of freight, the U.S. Army Corps of Engineers is constructing a larger lock at the Chickamauga Dam that would accommodate nine barges at one time — eight more than the existing facility. The original structure was built in 1940 and could be decommissioned in 2029.
"We've put as many Band-Aids as we could on the Chickamauga Lock to keep it operational," Joseph Cotton, project manager for the lock replacement, said during a tour of the site Monday.
(READ MORE: Costs of new Chickamauga Lock triple over time)
The facility suffers from a chemical reaction that causes concrete at the lock to grow, creating cracks and structural issues that Cotton said the Corps and the Tennessee Valley Authority have managed through years of aggressive maintenance. Major Jesse Davis, deputy commander for the U.S. Army Corps of Engineers' Nashville district, said attentive monitoring from the Tennessee Valley Authority, the Corps and the agency's contractors has ensured the dam remains structurally sound.
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"Every action we're taking considers this reaction and ensures that the final product is going to have long-term reliability and safety," Davis said during a presentation.
Although other dams also experience issues with concrete growth, Cotton said this is a fairly unique phenomenon in the Chattanooga area. A stone called dolomite causes the reaction, creating a thin gel-like substance that puts tension on billions of rocks throughout the dam. Crews have to take that into account during every stage of the construction project, and they monitor the effects using 3,000 sensors installed across the entire lock and dam.
"The Chickamauga lock and dam is really the problem child of the entire system," Cotton said.
Aiming to alleviate similar issues in the future, Cotton said the Corps and its partners have worked to identify quarries with appropriate materials for the lock. Crews are using about 300,000 cubic yards of concrete for the project, Cotton said, which is enough to build a two-lane road from Chattanooga to Clarksville.
The Tennessee Valley Authority built the lock along the Chickamauga Dam in the late 1930s. The Army Corps of Engineers now operates the lock and took over maintenance in the 1980s.
More than 1 million tons of freight move through the gates each year, keeping hundreds of large semi trucks on the road. Last year, 1.3 million tons moved through the facility, Cotton said, and that number could exceed 1.5 million in 2024.
Photo Gallery
Replacement lock construction at Chickamauga Dam
(READ MORE: New Chickamauga Lock in Chattanooga topped with first of 36 monoliths)
The new lock chamber will be 110 feet by 600 feet, greater than the existing dimensions of 60 feet by 360 feet, and will reduce commercial transit times by 80%. It will preserve access to 318 miles of upstream waterways.
The Corps hopes to award a final contract for the project this fall. Officials expect the total cost to replace the lock is $954 million, which includes a $237 million appropriation in the past federal budget. The cost of the project has tripled over the past two decades amid congressional funding delays and additional problems with supplies and labor.
