Brittney Lofthouse – Contributing Writer
Heavy rains in February caused significant cracks to appear in both lanes of the Jackson County side of Cowee Mountain. What started as a four-inch-deep crack in one spot along Highway 441 between Franklin and Dillsboro quickly expanded and by the time it is fully repaired, will cost the North Carolina Department of Transportation (NCDOT) about $14 million.
David Uchiyama, Communications Officer for the Western Mountains Area of the NC DOT, said that the original plan for the DOT was to repave the crack, something that has occurred every couple of years when the ground settles. After the crack was repaved in the Spring, it became quickly evident that it wasn’t going to be a quick fix.
“Engineers got to looking at the road and found that the drainage underneath the road has essentially failed and needed to be completely replaced,” said Uchiyama. “We got an emergency repair contract to fix the drainage issue and that was completed on Aug.5.”
When engineers began looking to repair the drainage issues beneath the road, they discovered a much more serious issue. A full geotechnical review of Cowee Mountain was ordered to fully assess the damage. Geotechnical concerns include expansive soils, potential for erosion, lavacap, bedrock, mudflow, soils with a high liquefaction potential, a high water table, frost heave potential, and other issues. The geotechnical report revealed significant erosion and problems with the reinforcement wall on the backside of Cowee Mountain, which is essentially holding up the road.
“When the drainage was completed, we switched our focus to the wall and fully reinforcing the road to prevent any catastrophic damage,” said Uchiyama.
To address the wall issue, Uchiyama said that a new soil nail wall will be established. Soil nail walls consists of installing passive reinforcement (i.e., no post-tensioning) in existing ground by installing closely spaced steel bars or sections (i.e., nails) and placing a front face support. Soil nails are later grouted if they are installed in drilled holes.
The construction change for the soil nail wall was added to the emergency contract originally issued in the Spring. The contract was awarded to WNC Paving out of Waynesville. During the next phase of the project, the two northbound lanes will be excavated and the 28 foot soil nail wall will be built to support and stabilize the southbound lanes currently in use. Once that is complete, the old wall will be removed and rock buttress built to support the road. Rock buttress or rock fill is a fill rehabilitation method on unstable slope. Its main purpose is to reduce erosion from rainfall which can change the geometry of a slope thus making it unstable. According to Uchiyama, that phase is expected to begin within the next two weeks.
From the time the work is completed, the DOT expects it to take 6-9 months to complete, meaning Cowee Mountain will not be back to normal until next summer. With 14,000 travelers a day, Uchiyama says that the plan is to keep the road open the entire time. WNC Paving is at the mercy of the weather as to when they can complete the paving of the newly reinforced road. Asphalt plants close for the winter toward the end of October early November and do not open back up until late March or early April.
To date, the DOT has spent $855,000 for the work that has been completed, and according to Uchiyama, the state is looking to spend another $13 million to complete the project.