Contractors have worked around the clock to stabilize and secure the hillside along Interstate 75 in Campbell County.
Much of the initial work has involved ground-breaking methods such as launched soil nails to provide immediate relief to the crumbling surface. The long-term fix will require a time-tested and less sophisticated method to lay a solid groundwork for the interstate.
"We basically take non-degradable rock to build the embankment back from the ground up," said TDOT engineer David Barker. "Our situation right now is getting this rebuilt as quickly as possible and yet maintaining traffic on what we have left."
Crews have to solidify what is left of the embankment and clean out the loose debris below. Then large rocks are brought in at the base of the embankment.
"That will be their working platform to bring this on up. We do have plenty of rock available in Tennessee so rebuilding something out of rock is an option we use a lot. A lot of places don't have a rock readily available to utilize, but it is a resource we have," said Barker.
If you want an idea of what the finished repairs on I-75 will look like, you don't have to travel very far from the current construction site. TDOT made a very similar repair in 2005 about one mile south of the current collapse.
"The slide in 2005 was not as big as the current one. The one we're working on now is probably 50 percent larger, maybe even twice as big. But the same principles apply in terms of piling the rock and filling it in. This limestone is lighter in color, so if you look on Google Earth at I-75 you can easily find the site of the 2005 slide. There's so much rock here it shows up as a white spot along the interstate," said Barker.
Barker said there is plenty of solid foundation beneath the crumbling surface at the current site.
"Identifying stable material is not the biggest challenge. For us, the biggest challenge is working on a road while keeping it open," said Barker. "There are not any good detours for this part of I-75, so we are really working to get it back open again. When we are done, this shouldn't be going anywhere from now on once we get it built."
TDOT estimates one southbound lane of I-75 will re-open Monday. Until then, detours will remain in place for all southbound traffic beginning at Jellico. TDOT's website provides full detour details for all types of commercial and passenger traffic.