In Chattanooga, Tenn., the second phase of construction on the I-75/ I-24 interchange improvement project is on track for a spring 2026 completion. The Tennessee Department of Transportation (TDOT) is overseeing the design-build effort, with the cost of Phase II work estimated at $162 million.

"The original plan was to reconstruct the entire interchange in a single project," Jeff Blevins, TDOT Region 2 manager of alternative delivery, told Construction Equipment Guide. "However, due to funding limitations, it was divided into two phases. Phase II fulfills the remaining objectives of the initial design, ensuring that the full scope of improvements is realized."

The previous interchange featured a left-hand exit ramp from I-75 north to I-24 west, which did not comply with current design standards. Phase I relocated the exit to the right and enhanced the I-75 north entrance ramp from Ringgold Road. These changes eliminated problematic weaving patterns and increased overall capacity with additional lanes on I-75.

"Phase II adds lanes to I-24 between the core of the interchange and Germantown Road and reconfigures entrance and exit ramps in both directions at Moore Road, eliminating weaving issues on I-24," said Blevins. "It also extends the new lanes on I-75 from Phase I to the East Brainerd Road exit, further improving traffic flow.

According to Blevins, the Hamilton County interchange serves as a critical junction for both passenger and commercial traffic traveling between Nashville, Knoxville and Atlanta. It's one of the region's most heavily used corridors.

Phase II work began in 2023. Wright Brothers Construction Company of Charleston serves as general contractor for the ongoing project, where completion of the center lanes on the I-75 bridge over the railroad and the concrete approach lanes is pending. Blevins said work has progressed smoothly, especially considering the scale and complexity of the work involved.

Phase II lane closures have been strategically scheduled during nighttime hours and select weekends to minimize disruption. Motorists have experienced minor delays during peak travel times and have generally been supportive.

"They will benefit from increased capacity, reduced weaving conflicts, streamlined entrance and exit ramps and improved overall traffic efficiency throughout the corridor," said Blevins.

Blevins also noted that construction access has been one of Phase II's biggest challenges.

"This has affected employees, dump trucks, material deliveries, etc. as far as difficulties with ingress/egress of certain areas. Joint lines — matching tie-in points from Phase I — also have been an issue. Some construction limits do not overlap into Phase I, and an in-depth survey is required beyond what is originally provided to ensure a smooth transition between phases."

Blevins said I-24 bridges, retaining walls, noise barrier walls and drainage are complete. I-24 surface paving, texture coating and I-75 bridge Phase II continue.

Regarding the widening of I-24 from Germantown Road to Spring Creek Road, "This involved multiple traffic phases, in order to construct soldier pile/soil nail walls to retain the tight vicinity of North and South Terraces. This also required enhanced drainage features to direct storm runoff from the widened asphalt surface," said Blevins.

Other tasks included removing concrete pavement and replacing it with asphalt, replacing the South Moore and McBrien Road bridges and constructing noise barrier walls that line nearly the entire length from Germantown to Spring Creek.

Reconfiguring the entrance and exit ramps to the North and South Terraces involved in-depth studies into the effectiveness of the established traffic control plans to allow for the safety of workers and the traveling public. Closing both entrance and exit ramps between Belvoir and Moore allowed expedited construction and has resulted in a higher quality product, without multiple phase joints in the area.

Roughly 150,000 cu. yds. of dirt are being moved during Phase II. As part of excavation efforts, much of the material excavated was unsuitable to use as borrow in other areas of the project.

"A portion of the project required borrow material and rip-rap as fill in areas that retained subsurface water," said Blevins. "Due to heavy traffic, excavation areas were sequenced to maintain production, as many areas were unavailable at any given time with the current traffic phasing."

As for the widening of I-75 from west of the CSX Railroad overpass to the East Brainerd Road interchange, demolition and reconstruction of the bridge over CSX Railroad was necessary to accommodate a fifth lane in each direction and new vertical clearances over the railroad. Placement of concrete pavement to allow the fifth lane and match the new vertical alignment was also necessary, as was realignment of the East Brainerd entrance ramp to I-75 southbound.

Replacing the I-75 bridge over the CSX railroad involved shifting traffic to the median and constricting I-75 to three lanes in each direction. Crews had to demo the existing bridge outside of traffic and shift vehicles to the newly constructed portion of the bridge in both directions. Work also included demolishing and reconstructing the interior portion of the bridge and tying into the recently constructed first phase.

Blevins stressed that rubblization was a major factor in the expedited delivery of the project.

"This alternative allowed the existing concrete to serve as a base layer for the new asphalt in fill areas. Rubblization had minimal impact on noise and eliminated the need for excavation in several areas. In addition, barrier walls play a key role in reducing the noise of the remaining construction activities."

Heavy equipment used during Phase II includes excavators, dozers, motor graders, dump trucks, rollers, loaders, skid steers, cranes, manlifts, pile drivers, drills, concrete screeds, bucket trucks, guardrail post drivers, trenchers, boring machines, brooms, asphalt pavers and shuttle buggies.

Aggregate, concrete, asphalt, pipe, reinforcing steel, steel piles and concrete beams are among the chief materials required to complete the work.

Blevins also remarked that the elements can have a drastic effect on construction.

"Grading, asphalt paving and concrete placement are greatly weather-dependent. Most items of work can be completed during the winter months, whilst keeping in mind temperature constraints on concrete placement and asphalt paving surface layers. Production is impacted by heavy frosts and winter weather. Lower temperatures do not allow moisture on the ground to deplete as quickly as other seasons of work."

As crews head into the final stretch, Blevins said it's rewarding to witness the amount of progress made on the project.

"We take tremendous pride in knowing we are serving hundreds of thousands of commuters every day. Allowing the public to travel safer and quicker to their destination than when we first mobilized is a large accomplishment." CEG