I-75, I-24 'Split' project slated for summer 2021 finish as new design takes shape

The $132.6 million improvement project just north of the Georgia state line at the Interstate 75-Interstate 24 interchange - otherwise known as the "Split" - is on track for completion by summer 2021 as some of the most significant features of the redesign begin to take shape.

Marietta, Georgia,-based C.W. Matthews Co. is working to complete new ramps and a new leg of I-75 to switch traffic onto its new alignment this fall, Tennessee Department of Transportation spokeswoman Jennifer Flynn said.

"This will allow construction of the remaining structures and ramps in the spring and summer of 2021 with traffic in its final alignment soon afterward," Flynn said.

More than 100,000 vehicles a day travel the interchange, known for its daily backups, outdated merge lanes and frequent crashes.

The project consists of widening existing roads and ramps, increasing the radius of ramps, reconfiguring entrance and exit ramps on I-75, shifting the interchange to the west and modifying the Tennessee Welcome Center area traffic circulation, according to TDOT. The project includes new bridges for Spring Creek Road over I-24, as well as interstate bridges throughout the interchange area.

The Split is one of two Chattanooga area interchanges to make the list of the country's 100 worst bottlenecks from the American Transportation Research Institute, the other interchange being the I-24 to U.S. Highway 27 for downtown Chattanooga. Neither of the interchanges ended up in the national top 20, however. TDOT Commissioner John Schroer, during a June 2017 project kickoff event, called the Split "about the worst interchange in the state of Tennessee."

Now, northbound drivers on I-75 headed for downtown Chattanooga and Nashville pile into the two left-hand lanes to bottleneck into a two-to-one lane merge onto I-24 West. This awkward merging creates a massive daily backup that extends south into Georgia when traffic is heavy.

Motorists will see constant change as the project's bridges and retaining walls form the layout of the new interchange, TDOT Region 2 director Joe Deering said in an email. Crews are now working on six bridges and five retaining walls and back-filling them with earth already stored onsite, Deering said.

"All existing bridges will be replaced while maintaining the existing number of lanes in all directions," he said.

In recent weeks, drivers headed north through the backup now can see a two-lane-wide ramp forming on the right near the Tennessee Welcome Center that takes aim at a new bridge pier, part of one of the most dramatic changes to the Split's traffic pattern in the project that began a year ago this week.

Flynn said the grading and structural work in front of the welcome center is for a new ramp that will connect Ringgold Road and welcome center traffic to I-75 North.

"At the interchange, structural bridge and retaining wall work is progressing to support the construction of the new interstate-to-interstate ramps," Flynn said of northbound I-75 drivers' view. "To the driver's left, crews are constructing the future I75 NB and SB mainline and I-75 NB to I-24 WB fly-over ramp bridge."

Southbound I-75 drivers will see the same structural bridge and retaining wall work, and the "most prominent structure first encountered after the split is the bridge and walls carrying the future I-24 East to I-75 North ramp which will be elevated over the entire interchange," she said.

That ramp now passes though the interchange at ground level.

Above I-24 west of the interchange, the replacement of the Spring Creek Road Bridge is being performed in two stages to maintain local traffic flow in both directions over the interstate. The northbound lanes of Spring Creek Road now are closed as that half of the bridge is replaced, and traffic will be shifted onto the new portion by early fall 2020, followed by replacement of the southbound side's bridge.

"[T]raffic is expected to be in its final configuration with two lanes in each direction in spring of 2021," Flynn said. The bridges over I-24 at McBrien and Moore roads will be replaced later and aren't yet funded, she said.

"Those bridges are planned to be replaced in the second phase of the interchange modification project, which will widen I-24 from the interchange to near Germantown Road," she said. "This second phase is tentatively planned to start shortly after the completion of the current work on the I-75/I-24 interchange and is contingent on funding."

The interchange project is being coordinated with TDOT's adjacent $32.9 million bridge replacement project launched last month less than a mile away at the Belvoir Avenue bridge over I-24 and the Germantown Road overpass on I-24. The construction manager on that project is Bell & Associates Construction and the design manager is Barge Design Solutions.

The future widening of I-24 requires the replacement of the bridges along the corridor between Germantown Road and the interchange because the existing overhead bridges don't have the space between their supports to allow more lanes, according to Flynn.

"The Moore Road and McBrien Road bridges will be replaced after the replacements are complete at Germantown Road, Belvoir Avenue and Spring Creek Road," she said. "This will happen along with the widening of I-24 in Phase-2 of the interchange modification."

Despite heavy rains, a tornado outbreak and the COVID-19 pandemic, crews have kept pace, Flynn said.

"The heavy rains and storms made work in low-lying areas difficult, but work was able to progress in other areas while the flood waters receded," she said. There was no storm damage reported in the project.

Due to the impact on travel from the coronavirus pandemic, the reduction in traffic has improved safety and efficiency for the delivery of materials and in moving equipment to and around the project site, Flynn said.

"With less traffic comes higher speeds, and law enforcement have been on the interstates night and day patrolling the work zones," she said.

Flynn noted crews "have modified their health and safety plans to ensure that they are safe when working together in groups or teams."

Meanwhile, Deering urged motorists to be on alert.

"It is very important that motorists pay attention to the constant changes on the road through the work zone," he said.

Contact Ben Benton at bbenton@timesfreepress.com or 423-757-6569. Follow him on Twitter @BenBenton or at www.facebook.com/benbenton1.