The total rehabilitation of an historic bridge is currently well under way in downtown Chattanooga, TN, with the project requiring the bridge be closed for at least two years.
“Though the temporary closure of the Market Street Bridge will be painful, the renovation project is absolutely necessary to maintaining this important and historic thoroughfare for generations to come,” said Chattanooga Mayor Ron Littlefield. “We are working closely with the North Shore merchants, residents and TDOT [Tennessee Department of Transportation] to ensure that the closure creates the least amount of inconvenience possible to our citizens.”
TDOT’s Regional Director Bob Brown noted that his organization “will do everything in our power to keep this project on schedule. Although this will be an inconvenience to those who normally use the bridge, the city of Chattanooga will have a totally refurbished bridge that will be a great source of pride when the project is complete.”
Known to locals as the Market Street Bridge, the official name is the Chief John Ross Bridge. Owned by the State of Tennessee, it is located on U.S. 127 (SR 8), and crosses the Tennessee River and the Riverfront Parkway.
The $13-million contract for the rehabilitation project was awarded to Mountain States Contractors LLC of Durham, NC, under the direction of Jerry Britton. Work began on Sept. 18 and is scheduled for completion in the fall 2007.
The bridge is currently the third-longest working bascule span in the world. It is opened using two 25-hp electric motors, with the rest of the work handled by counter weights.
The rehabilitation project involves the removal and replacement of beams and other supporting structures. In addition, a large number of repairs will be made to the structural steel in the drawbridge portion of the bridge, which is a double-leaf bascule span.
The contract also called for the replacement of the deteriorating bridge surface, with wider sidewalks and improved lighting on the bridge. While the traffic lanes will not be widened, the sidewalks will be extended by 18 in. on each side in an effort to make the bridge more pedestrian-friendly.
“This project will correct a number of problems on the bridge, which for its age is in pretty fair condition,” said Jennifer Osborne, regional community relations officer of TDOT.
She noted that some in-stream work, including removal of accumulated drift and repair scour of bridge piers, will not require bridge closing, and will take approximately six months.
“A major portion of the work will require the closing of the bridge, since it involves removal and replacement of beams and other supporting structures that could possibly destabilize the bridge’s structure,” Osborne said.
“There are also a large number of repairs to be made to the structural steel composing the double-leaf bascule span. All of these repairs are estimated to take approximately two years to perform, but the time will really depend on what is found once the work is started.”
The first step for the contractors involved the removal of the asphalt and concrete decks on the bridge. This was followed by hydro-demolition, which, Osborne explained is the use of water forced through lines to demolish layers of concrete and asphalt.
“It was pretty successful, too,” she said. “Every load of material from the bridge is carefully taken apart, with the rebar going to one area and the concrete going in another. The rebar is recycled by one company and the concrete is recycled by another.”
TDOT’s regional construction manager reported that all of the reinforcing steel that is removed from the bridge will be recycled.
Osborne noted that the project is currently on schedule, and one of the unique challenges is that the bridge must be demolished in the middle of a downtown area without damaging any structures underneath. A barge was placed in the water under the bridge to ensure that items falling off the bridge were caught.
“The bridge will be restored as it was when constructed in 1917, so there is much specialty concrete work involved,” Osborne said. “It is a historical structure, so any work done to it has to be historically correct.”
Britton noted that special care must be taken to ensure that the work is identical to the old structure.
“This project is unique in that it is the first time we’ve worked with concrete arches and a bascule bridge,” he said.
Adding to the difficulty and expense of the project is the fact that the city of Chattanooga has a number of new facilities in and under the bridge that must be protected from damage during the work.
“This is the first time that a construction project has had such a public communications effort to go along with the work,” Britton said. “Because the Market Street Bridge is one of Chattanooga’s most loved landmarks, we wanted to make sure folks had access to information about the renovation so that they know as much as possible about our efforts. This has been extremely helpful all the way around.”
According to Britton, the number of people assigned to the job varies from specialty to specialty, but the average number is approximately 50 workers focusing on the project each day.
Major subcontractors include Adman Electric of Chattanooga providing the electrical work and Gilley of Manchester, TN, providing the pre-stressed beams.
Equipment at the site includes Link-Belt HS132s, LS518s, LS 1338 and two 4300 track hoes.
A total of 3,500 yds. of concrete will be disposed of for the project, and 5,500 yds. will be brought in for construction.
Originally, TDOT planned to close the Market Street Bridge due to growing concerns about the deteriorating condition of the bridge. However, the city of Tennessee lobbied to hold off until the 21st Century Waterfront project was completed in May of last year, and TDOT made repairs to enable to bridge to stay open during that period.
The 21st Century Waterfront project has roots that reach back 20 years, and stems from a vision of a renaissance for the city of Chattanooga. Changes transformed the downtown riverfront, which now includes an aquarium, pedestrian pier and bridge, wading pools, a visitors’ center and numerous museums.
The $120-million transformation involved 129 acres. Osborne noted that all bridges in the Chattanooga downtown area are painted the same special color of blue, which is referred to in TDOT’s Nashville Structures Office as Chattanooga Blue.
TDOT noted that the renovated bridge will look much like the original — “only stronger, safer and ready to put into use for another 90 years.” CEG