A roadway on the north side of Nashville, TN, that comfortably handled 60,000 vehicles a day two decades ago is straining today under a load twice that heavy. The roadway is Interstate 65, which leaves Nashville and heads to Louisville, KY, and Indianapolis, IN.
Where it forks northeast away from Interstate 24, the highway passes through Nashville residential neighborhoods that are laced by numerous east-west streets.
It is this busy corridor passing under cross-town bridges that the Tennessee Department of Transportation (TDOT) is upgrading.
The most ambitious of the project’s individual legs is a $47 million revamping of the highway from near Dickerson Road almost to Old Hickory Boulevard, a distance of 2.5 mi. (4 km).
The basic work is widening the interstate to five lanes in each direction from an existing three lanes. A sixth lane is added at one point to feed a primary intersection.
The added lanes are just the beginning, however, because more lanes mean a wider corridor. That means that six bridges crossing over I-65 no longer will span it and must be replaced.
Furthermore, approximately one third of the way into the project, I-65 intersects with a major thoroughfare, Briley Parkway. A separate $36 million contract for improvement of that interchange includes construction of a flyover span to funnel southbound I-65 drivers onto Briley.
Randy Allen is the project manager of Rogers Group Inc. of Nashville, the prime contractor on the job.
As an engineer, he found satisfaction in meeting the challenges of constructing the flyover bridge. The structure is 1,570 ft. (479 m) long, significantly curved and rises approximately 100 ft. (30 m) in the air to pass over both I-65 and the parkway.
“It’s not a small curve, either,” said Allen. He notes that a vehicle enters the crossover bridge as a southbound I-65 traveler and 1,500 ft. (457.2 m) later exits the bridge headed due east on the parkway –– a 90-degree change of direction.
“It’s a very sharp curve, in fact,” said Allen.
The challenge for Allen and his crews came in piecing together the curved spans and their supporting columns while working within extremely small tolerances.
Sentry Steel Service of Hendersonville, TN, handles iron work for Rogers, primarily using on this job a Link-Belt 200-ton (181 t) crane, a smaller Manitowoc and several American truck cranes.
Each of the bridge’s reinforced concrete columns was positioned and rooted. Then a reinforced concrete cap 57 ft. (17.3 m) long and weighing 30 tons (28 t) was raised above it by Sentry crews.
The column and cap were not joined at that point. Rather, the cap, each of which is 5 ft. (1.5 m) tall and just as thick, was positioned above the column on scaffolds. Girders then were placed on the cap, with other scaffolds placed beneath them to help support their weight. The various pieces were field spliced.
To add to the engineering challenge, the tentative assembly could not be leveled at that point. It had to be canted at the appropriate angle to accommodate cars that would be cornering at speed on the looping roadway.
Only when various calibrations and computations confirmed that each column-and-cap assembly was situated so that curving girders from it would join seamlessly with the next unit were welders set free to make it tight.
“Everything had to be dead-on perfect,” said Allen. “It couldn’t be an eighth of an inch off. That’s the only way it could be done.”
Building the bridge was, said the engineer/manager, “a lot of fun.”
Unlike the flyover, which will serve only exiting southbound I-65 traffic, two new and wider bridges will serve far more numerous vehicles moving on the parkway itself.
One bridge is a seven-span structure, the other an eight-span, each bridge slightly more than 1,400 ft. (425 m) long. The goal of the interchange work is to ease congestion and speed the flow of intersecting traffic.
Six replacement bridges that will link neighborhoods across the interstate are much shorter than those on the parkway. They vary in width, and range in length from 220 ft. (67 m) to 417 ft. (127 m). Most are of steel fabrication, though a couple are pre-cast concrete.
Paving is the other major element of the construction project. Some 1.4 million cu. yds. (1.1 million cu m) of earth were carved away and relocated to create the wider footprint necessary for the additional lanes.
Subcontractors exclusively used Caterpillar equipment to blade the earth.
The interstate’s main lanes will be formed of 13 in. (.25 cm) of concrete; on-and-off ramps will be 10 in. (.3 cm) thick.
In all, more than 300,000 sq. yds. (250,000 sq m) of concrete will be poured through Gomaco slipform pavers operated by subcontractor Harper Construction Inc. of Shelbyville, TN.
Unfortunately, the pavement work has not proceeded smoothly. It has been hit with delays. How many delays?
“A lot,” said Doug Hagar, TDOT project supervisor.
From the onset, construction schedules have been rolled back by events beyond the control of contractors and TDOT supervisors.
Right-of-way for the widened corridor was to have been secured in spring 2000, for example, but was not completed until months later.
The immediate consequence was that utility relocation work required by the wider roadbed was pushed back. That work was not finished as planned in the winter months.
Rather than being able to pave when warm weather rolled around, the utility work necessarily continued. That shortened the season on the other end for paving.
The paving plan, said Hagar, was to construct and pave three new traffic lanes on the outside of existing I-65, then “flop the traffic onto the outside lanes and tear up and pave the inside ones.”
Working the plan has not been difficult. Working at all has been. Winter temperatures are dragging out the process.
“That’s why we’re sitting right here now, ready to pave but can’t because of the cold weather,” Hagar said in mid-January as a series of winter storms swept across the Southeast and Mid-Atlantic states.
When cold nights encroach on the project, Harper’s on-site concrete plant crew must allow two hours to shut down properly. It naturally follows that some days are longer and more productive than others.
Another obstacle that interrupted work is the busy residential character of the neighborhood. Crews have had to work around rush hour and weekend traffic, closing lanes and backing up lines of traffic as little as possible.
However, the worst time for them was between Thanksgiving and Christmas. A major shopping attraction, Rivergate Mall, lies just north of the project.
City and state officials off site concluded that frustrating Rivergate shoppers was a larger concern than frustrating contractors. The result: No lanes are closed at all during the entire month between holidays, even though in the midst of one holiday season bridge iron was delivered but could not be erected.
Still, the overall project is approximately 80 percent complete, said Allen. It is expected now to be finished in August.
The other visible element of the project is placement of noise barriers on both sides of the interstate. They range in height from 5 ft. (1.5 m) to 30 ft. (9 m), depending on the level of the roadbed in relation to adjacent residential units.
“Whatever it takes to get the decibels up and over the houses,” Hagar said.
Four of the noise abatement wall sections are reflective, meaning they are intended to bounce noise back into the trafficway or deflect it away from housing.
The fifth wall section is constructed of Durisol, the Canadian bonded material of cement and wood fiber. Its panels are designed to absorb sound rather than just redirect it. That wall along a stretch of the southbound lanes is being erected as an experiment.
The contract with Rogers also calls for installation of Intelligent Transportation System technology, by which traffic controllers can monitor and control traffic flow.
Just north of the I-65 segment worked on by Rogers, another leg of the job is proceeding. A separate contract was let a year after Rogers won the bidding for its segment.
The second project extends the corridor widening and paving another 3.5 mi. (5.6 km) but contains fewer bridges and no major interchanges.
LoJac Inc. of Lebanon, TN, is the contractor on that stretch of the project.