This track hoe adds rock to the foundation of a retaining wall at the US-27 bridge over 4th Street. Re-alignment of U.S. Highway 27, to remove the "S" curves, requires reconfiguring the 4th Street interchange in downtown Chattanooga.

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U.S. 27


The U.S. Highway 27 reconstruction project through downtown Chattanooga — the most expensive such work in state history — is behind schedule and over budget, mostly because of an unforgiving Mother Earth.

In fact, thanks to lots of unanticipated underground problems, the cost for the widening project on Highway 27 has jumped more than 13 percent from the original $126 million bid to an estimated $143 million, according to the Tennessee Department of Transportation. The job, originally scheduled for a July 2019 completion date, is now expected to be done by January 2020.

"During construction of the largest retaining wall on the project, wall #20, we encountered 10 times more rock than estimated when drilling for soldier piles," TDOT spokeswoman Jennifer Flynn said in an email. Soldier piles are H-shaped steel beams that are driven or drilled into the ground to support retaining walls.

"Additionally, when filling the voids in the slope with compaction grout, we encountered three times the amount of voids than originally estimated," Flynn said.

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Oct. 16, 2015: U.S. Highway 27 widening project let to contract

Bid price: $126.3 million

Estimated completion date: January 2020

PHASE I (2015)

Work focused on northbound bridges and retaining wall at Cameron Hill. Construction of new Main Street exit ramp begins

PHASE II (2016)

Traffic shifted, median work begins

Construction of retaining wall on Cameron Hill continues

Olgiati bridge work begins

PHASE III (2017)

Traffic shifted, southbound bridge work begins

Construction of Cameron Hill retaining wall continues

Olgiati Bridge work continues

PHASE IV (2018-2019)

Northbound entrance ramps at MLK and Fourth Street completed

Final asphalt paving and striping work completed

Lighting and ITS completed

Estimated project completion date: January 2020

Source: Tennessee Department of Transportation

That wasn't the end of surprises.

Flynn said that during retaining wall construction, crews "encountered foundry sand in multiple locations that had to be removed and taken to a landfill for proper disposal." Another unanticipated cost was the installation of struts on the Olgiati Bridge river piers to provide more support for the added lanes.

Construction costs continually climbed since the first estimate of $80 million was attached to the initial plan for downtown back in 2012. The project from Interstate 24 across the Olgiati Bridge started in 2015 as its sibling project north of the Olgiati wrapped up. Funding to pay for the rising cost is borne by the state and federal governments.

"[W]e work with the Federal Highway Administration to verify [and/or] justify any additional costs so that we can continue to get matching funds," Flynn said. Federal funding provides 80 percent of the money for additional costs and Tennessee kicks in the remaining 20 percent.

The original construction of the piece of Highway 27 that runs through downtown harks back to the 1950s and 1960s. Over the past half century, traffic volume has increased exponentially. The section's winding design has contributed to crashes and daily backups that helped make the Highway 27-Interstate 24 interchange the worst in Tennessee and one of the nation's worst commercial truck bottlenecks, according to the American Transportation Research Institute.

Work crews last week were scattered from one end of the project to the other. On the south end near the interchange with I-24, graders were leveling dirt down the center of the project toward Martin Luther King Jr. Boulevard, while on the downtown end of the Olgiati Bridge a small crew was tying in rebar for the lanes added to the bridge as the exit to Fourth Street.

Between them, a larger crew worked at the top of a retaining wall in the middle of the Fourth Street offramp loop where concrete was being poured into a wood-framed form.

Like bees, cars and trucks swarm through the cloverleaf in close quarters with construction crews.

Traffic snarls and crashes associated with the project have cause a few tweaks over the months. On-ramps that were previously signaled with yield signs now have stop signs to improve safe, one-at-a-time entrances to the highway. Speed monitors greet motorists at each end of the project with flashing warnings for any vehicle going faster than 45 mph.

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U.S. Highway 27 project features

9: Multi-phase bridges

31: Retaining walls

1.623: Miles of roadway

0.665: Miles of Olgiati Bridge in project

2.288: Miles of entire project

Source: Tennessee Department of Transportation

On Thursday, Grady Stageberg, construction engineer inspector for contractor Volkert Inc., was working atop one of the retaining walls using a device that detects lateral movement of the earth near the walls.

"The traffic pattern now is in phase II," Stageberg said as he performed measurements with the device, called an inclinometer. "Once they get the walls built, the traffic pattern will go into phase III."

Flynn said that traffic pattern change will come between now and Christmas.

"Southbound traffic will be switched to the new portion of the roadway currently being completed," Flynn said. "This will allow the contractor to construct the new southbound lanes and several ramps. Also, this should restore acceleration and deceleration room for some — not all — of the southbound ramps that were lost in the last traffic shift."

Despite the unexpected problems, construction is sticking pretty close to the original plan, Flynn said.

"While there have been increased costs, the plans predicted the need for some very specialized work to address most of the problems we have seen, just not to the scale that was eventually needed to overcome them," she said.

A Signal Mountain reader in May questioned the aesthetics of the project, particularly pointing to the now-complete phase I retaining walls on the north side of the Olgiati Bridge where the concrete surfaces are starting to become dirty.

"The project does have some aesthetic features. There is a specially selected form liner used to make the cast concrete on the project look similar to cut limestone block walls that are located throughout Chattanooga, along with the use of the tri-star from the Tennessee State Flag on the bridges," Flynn said.

"Although we appreciate aesthetics, TDOT is more concerned with putting their money into the construction of durable, functional items (bridges, roadways, retaining walls, etc.) and less on visual flair," she said.

But landscaping is planned for the project, though TDOT won't be part of it.

"There is a landscaping committee spearheaded by Judge Neil Thomas that is looking into beautification of the project area after the construction is completed," Flynn said. "The landscaping will not be started until sometime in early 2020 after construction is done on the project."

Contact staff writer Ben Benton at or 423-757-6569. Follow him on Twitter @BenBenton or at