GRUNDY COUNTY, Tenn. -- A gaping hole across the eastbound lanes of Interstate 24 could have been a tragedy, but instead it's just another major inconvenience for motorists caused by a natural geographic phenomenon, state officials said.
The Tennessee Department of Transportation awarded a $266,960 emergency contract to Highways, Inc. today at 3:30 p.m. to repair the damaged section of I-24 immediately.
Sometime around 8 a.m. CDT Tuesday a nearly two-foot-thick slab of asphalt highway gave way, opening a massive 500-square-foot hole that is 25 feet deep, according to the Tennessee Department of Transportation.
At that time of day, right at the Grundy-Coffee County line, it was only a matter of time before cars fell into the hole, but fortunately just one vehicle suffered minor damage and the driver was able to move away, said Ray Rucker, TDOT regional maintenance supervisor.
State officials said that's because transportation department employee David Shelton just happened to be heading to a job site in Franklin County when he spotted an 18-wheeler just barely make it past the hole before the last bit of asphalt fell into the pit.
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Staff photo by Danielle Moore/Chattanooga Times Free Press - TDOT workers assess damage done by a sinkhole near mile marker 127 near Grundy County Tuesday afternoon. The hole occurred at approximately 8 a.m. Tuesday morning and could have been caused by ground changes due to recent historic rainfall according to TDOT geological engineer Vanessa Bateman.
"I've never seen anything like this around here," Mr. Shelton said, standing by the large TDOT backhoe he positioned to stop traffic.
The cause, like a number of other natural calamities that have closed roads over the last year, was rain, officials said. Though Mr. Rucker said the cavernous hole could have been forming for years, heavy rains -- the same storms that flooded Nashville and swelled creeks in Chattanooga -- likely provided the final wash that made the road totally unstable.
"It's a slow-moving process, but all this excessive rain probably caused the groundwater to come up and wash the dirt away," said Vanessa Batement, a TDOT geotechnical engineer.
Sinkholes aren't uncommon in middle Tennessee and even in Chattanooga. The ground, which is reinforced with limestone, sits on top of the Manchester Aquifer, an underground layer of water-bearing rock.
State transportation officials said Tuesday that the interstate could reopen by Saturday, but there's plenty of work between then and now. First, contractors have to dig out the hole and make it stable. On Tuesday, as crews walked delicately around the hole, it still was growing, Mr. Rucker said.
Then, workers will have to place stable rock on top of natural bedrock, Ms. Bateman said. The whole process is going to cost $266,000, according to the transportation department.
Until then, motorists are left with a winding commute around the sinkhole.
"Oh, it's a sinkhole?" said Nashville resident Gordon Droitcour, who stopped at a Wendy's for a late lunch Tuesday before embarking on the detour. "So, how long is that going to take (the detour)?"
On Tuesday afternoon, the 13-mile trip from exit 114 to Highway 41 to State Route 50 and then back onto I-24 via exit 127 took 45 minutes. TDOT recommends motorists consider several alternatives rather than taking the mostly two-lane detour, because it could take even longer at peak travel times.
STEPS TO FIX THE SINKHOLE
1. Contractors will dig a much larger hole that has sloping sides so large machinery can access the sinkhole better.
2. Workers must dig deep into bedrock.
3. A barrier between the median and the new hole must be installed.
4. Stable rock and sand will be dumped on top of bedrock to create a more stable base.
5. Workers will dump fill dirt and lay new asphalt on the interstate.
Source: TDOT
They recommend motorists who are Chattanooga-bound take Interstate 65 south to U.S. 64 and then come into the city on westbound I-24 beyond the sinkhole. That adds about an hour and 15 minutes to the commute. Motorists also can take I-40 to State Route 111 and then take U.S. 27 into Chattanooga. That route also adds a little more than a hour to the commute.
Atlanta-bound motorists from Nashville should take I-65 south to Birmingham and then take Interstate 20 east into Atlanta, according to TDOT. That route is about an hour longer than traveling through Chattanooga.
This isn't the first natural disaster to create headaches for area motorists. A rock slide on U.S. 64 in Polk County, Tenn., in November 2009 virtually isolated the eastern part of that county for nearly six months. And a rock slide on the side of Signal Mountain in December closed the most convenient route to that town for more than a week.
A rock slide in October 2009 on I-40 in North Carolina was not cleared until late April.
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Interstate 24 sinkholeStaff photo by Danielle Moore/Chattanooga Times Free Press - TDOT workers assess damage done by a sinkhole near mile marker 127 near Grundy County Tuesday afternoon. The hole occurred at approximately 8 a.m. Tuesday morning and could have been caused by ground changes due to recent historic rainfall according to TDOT geological engineer Vanessa Bateman.
Adam Crisp covers education issues for the Times Free Press. He joined the paper's staff in 2007 and initially covered crime, public safety, courts and general assignment topics. Prior to Chattanooga, Crisp was a crime reporter at the Savannah Morning News and has been a reporter and editor at community newspapers in southeast Georgia. In college, he led his student paper to a first-place general excellence award from the Georgia College Press Association. He earned ...
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