CLINCH MOUNTAIN — Almost 10 months after massive mountainslides, triggered by torrential rainfall and flash flooding in February, caused the closure of two main thoroughfares between Hawkins and Hancock counties, both roads remain closed, but an official told the Review and the Eagle this week that relief is in sight for “detour weary” travellers on SR 66 and SR 70.
“SR 66 is expected to be back open in mid- to-late December,” Mark Nagi, a public affairs officer for the Tenn. Dept. of Transportation said in response to an emailed inquiry from the two newspapers. “SR 70N is expected to be back open on or before December 5.”
However, because there is a secondary, smaller slide “just over the top of the mountain”, SR 70N will be signal-controlled to one-lane traffic at that point.
“This is part of a project being let (for bids) in December and will be required to maintain one lane of traffic at all times during construction,” Nagi said.
The Hwy. 70 project was let to construction on Feb. 27, to Charles Blalock & Sons, Inc.
The estimated cost of construction as of earlier this fall stood at $8,721,569.71.
More than 152,000 tons of graded solid rock — amounting to 7,600 truck loads — were required to reconstruct the slope of SR 70, most of it hauled from a quarry near Rogersville.
Nearly 25,000 linear feet of solid “concrete” nails were needed for soil stabilization on the steep slope that gave way in February, sweeping along with it two vehicles, the driver of one losing his life in the massive collapse.
The contract added a drainage system for storm water to prevent future failures.
More than 200 feet of 42-inch drain pipe has been installed that will carry water from a small stream and rain runoff from the top of the slide area to more than 150 feet below where it will empty into a drainage ditch lined with rip-wrap rocks, underneath and across to the other side of the lower portion of Hwy. 70.
The contractor excavated down the huge slide area while a subcontractor worked to install the concrete soil nail shoring system above. It was during this process that unstable soil conditions were encountered — that were not anticipated in the original design plans — that had to be dealt with.
That problematic soil had to be removed and additional soil nails installed to properly stabilize the slope, an engineer said.
In Hawkins County, Clinch School remains on a four-day school week because of lengthy detours and the additional time required for students and faculty to travel to and from the campus.
Hwy. 66 slide project update
Graded solid rock amounting to more than 156,000 tons has been applied to seven different locations spread over a mile-long stretch of highway to help repair the Hwy. 66 slide.
That section of roadway also collapsed in late February.
The $15,184,562 contract was let on March 1 to Summers & Taylor, Inc., and work began on April 18.
“When we were inspecting the slide area initially, we found several other areas that needed repairs while we were in there,” an engineer said. “Now, we have to mill the road and repave the smaller areas and those will be done.”
The larger portion of the slide area, however, is requiring almost as much reconstruction work as the Hwy. 70 site, he said.
An unexpected “hiccup”, engineers said, was the discovery on Sept. 11, during the excavation process, of acid-producing pyrite rock, which is uncommon to east Tennessee.
According to federal regulations, that pyritic material — some 40,000 tons of it — had to be removed and trucked to an approved landfill in Morristown that will accept it, at an estimated cost of $1.6 million.
Unlike the Hwy. 70 project, both lanes had to be completely reconstructed.
“We wanted to identify whatever needed to be addressed while we are in there,” an engineer said in an earlier visit to the site, “because we don’t want to have to re-do this again in five years. Those smaller five sites are not as critical, but if you don’t address them, they could end up something like this,” he said, waving a hand at the massive slide construction zone on Hwy. 70. “And I don’t believe anyone wants that.”
Another engineer said that TDOT will have its crews come in to both sites — hopefully before those roads reopen to the public, while traffic flow is limited — and do any necessary preventative maintenance, like cutting trees from rights-of-way, cleaning out ditches, and repairing shoulders and pavement damaged by heavy truck traffic.