Tennessee DOT Widens US-321 Near Fort Loudon Dam
The Tennessee Department of Transportation’s (TDOT) $70 million widening of a 1.7-mile stretch of SR-73 (US-321) to four lanes at the Fort Loudoun Dam requires the construction of three bridges and is well on its way to completion. This project will complete the process of creating four lanes on US-321 from Interstate 40 and Maryville.
“The project is moving along well,” says Clint Bane, TDOT Regional Construction Supervisor. “The canal and river bridges are moving along smoothly.”
The uppermost of nine dams built by the Tennessee Valley Authority (TVA) on the Tennessee River, the Fort Loudoun Dam came online in 1943. Twenty years later, the J. Carmichael Greer Bridge was built across the 4,190-foot-long dam. About 20,553 vehicles cross the two-lane bridge daily, with about 10 percent of that being truck traffic.
With time, the TVA decided it wanted to close that bridge and sought out an alternative alignment. In 2005, TVA and TDOT agreed on a plan.
“The TVA requested we remove the road off of the dam, so it would keep its facilities separated from public access,” Bane says. Therefore, “we are constructing the new bridge downstream over the river.”
The existing Greer bridge interferes with the TVA’s ability to perform maintenance on the dam, since any maintenance operations require stopping bridge traffic. The new configuration, when it opens in January 2017, also will limit public access to the dam.
Scope of Work
Vaughn & Melton Consulting Engineers of Knoxville, Tennessee, designed the roadway portion and TDOT designed the bridges for the project. Parsons Brinckerhoff of Nashville, Tennessee, is providing construction engineering and inspection services for the bridges and the highway reconstruction.
Charles Blalock and Sons of Sevierville, Tennessee, received the construction contract in August 2012. The project includes hauling in 870,000 cubic yards of dirt for grading from an off-site borrow pit arranged by the contractor; installing drainage, sewer and water lines; and constructing three bridges, necessary due to the road widening.
“The grading was a large part of this project,” Bane says. “Ninety-five percent of that work is complete.”
The first bridge, a three-span structure with concrete I-beam girders, passes over the Norfolk Southern Railroad tracks, which run under US-321. It features concrete paving and has been successfully completed.
The second, 1,400-foot long, four-span bridge crosses the Tennessee River, about 1,000 feet downstream from the existing Greer bridge. The steel girders rest on concrete piers. Piers two and three are complete, and pier one is about 40 percent finished. Abutment beams at each end of the bridge are complete. Beam erection should start at the fourth span in the next couple of months. This bridge, at $32 million, represents nearly half of the cost of the entire project.
The final 1,100-foot-long, five-span bridge runs parallel to the Greer bridge over the Tellico Canal. During this project, Blalock is building a twin bridge next to the existing bridge to handle the two new lanes of traffic. This structure also employs steel girders on concrete piers. The substructure has been completed and work continues on the balance of the bridge.
The project got off to a slow start, as the contractor secured land access to the river from the TVA and environmental permits for marine construction. Much of the work on the river bridge takes place on barges.
“It’s a very large bridge, with large girders,” Bane says. “Anytime you are building over a river, it’s a challenge. The contractor has done very well with it. He has a lot of experience with it.”
The presence of the endangered snail darter, a small fish, prevents the contractor from working on the water from February 1 to May 1 of each year, during fish spawning season. The snail darter was at the center of an environmental law case, involving the TVA, which went all the way to the Supreme Court during the 1970s.
“The contractor has to plan his work around the snail-darter season,” Bane explains. “He has a lot of grading, drainage and utility work, and he works on those items during these months.”
Once all of the road and bridge work is complete, Blalock will dismantle piece by piece the existing Greer bridge without damaging the dam or interfering with dam functions. Some local citizens would like to see the bridge remain as a pedestrian bridge, connecting walking trails and providing beautiful views of the water. But plans remain firm, for safety and liability reasons, to remove the structure at a cost of about $1 million within the existing contract.
“The next biggest challenge will be when they remove the existing bridge off of the dam,” Bane says. “It’s a very unique part of the project. It has to be done in a way there is no damage to the dam or TVA facilities.”