South Carolina DOT Adds Capacity with I-85 Widening
The Logistics of Traffic Patterns: South Carolina DOT Accelerates I-85 Widening with Design-Build and Traffic in Mind
Traffic continues to grow in much of the country. Many interstates are overwhelmed, and additions need to be made in order to allow for the added traffic and ease congestion. I-85, which runs from Virginia down to Alabama, is particularly busy in the area between Charlotte, North Carolina, and Greenville, South Carolina. In order to alleviate the congestion, the South Carolina section of this part of the route is being widened.
The South Carolina Department of Transportation (SCDOT) is undertaking a 21-mile project that goes from mile marker (MM) 77 in Spartanburg County to MM 98 in Cherokee County, which borders North Carolina. Simultaneously, a separate project is focusing on widening I-85 between MM 98 and MM 106, which is at the North Carolina state line.
For approximately 18 of the 21 miles (MM 80 to MM 98), I-85 is being expanded from four to six lanes. The other three miles or so (MM 77 to MM 80) is already six lanes. The current surfaces are also being reconstructed as the existing asphalt will be replaced by concrete. “The existing lanes are at the end of their life expectancy and the pavement is beginning to fail,” says Shane Parris, SCDOT’s District 4 Design-Build Engineer, who is administering the contract for SCDOT. “The increase in truck traffic in the area has had harsh impact on the road.” With the reconstruction, safety will be improved, and the road will be brought up to current standards.
There’s a bridge which belongs to the CSX railroad that crosses I-85 at MM 81. The railroad bridge is being replaced as part of the project. In addition, four interchanges are being completely rebuilt. “As it stands now, the interchanges and bridge are designed for a four-lane road,” says Parris. “The piers that hold the bridge up only have enough room for two lanes to go on either side.”
Besides redesigning the bridge and interchanges, they will be shifted slightly in order to maintain traffic on the existing overpass while the new bridge is completed. The interchange is basically in the same location but is shifted just enough to build the new bridge. Finally, the existing ramps at the interchanges are being rehabilitated and being brought up to standards.
The Benefits of Design-Build
The $435 million project, which is the second largest infrastructure improvement contract ever awarded in South Carolina, is being financed primarily by federal funds (80 percent) with the state picking up the remainder of the tab. SCDOT is utilizing a design-build contract for this project. The contractor is required to design, obtain permits, acquire right-of-way, coordinate utility relocation, and construct the 21 miles of interstate. SCDOT finds that design-build can accelerate a project and save money by encouraging innovative designs, materials, and construction practices.
Construction of the project began in the summer of 2017 and will continue till 2021. “We’re running a bit behind and are now looking for ways to accelerate the schedule. The contractor is in early stages of schedule review and mitigation,” says Parris. Weather issues and coordination with the rail road have led to the delays according to Parris. “When you have a third party, there’s an added layer which makes coordinating and communicating more challenging and leads to extra steps that take more time. They have to approve each step.”
Coordinating Heavy Traffic
Another challenge comes with working in a highly trafficked area. The average daily traffic for this segment of I-85 is 53,100 vehicles with approximately 25 percent of the total being truck traffic. “The main challenge when reconstructing in an area with existing traffic is the maintenance of traffic,” says Parris. “We have to make sure it works and drivers are safe when occupying the same space.” The project was designed with maintenance of traffic in mind.
During the day, the construction team works behind temporary barrier walls. The crews work at night when there are lane closures and on the weekends. “In design areas, we’re looking at maintenance of traffic so we have to have traffic in certain positions to construct certain items, which is part of the schedule review and mitigation that is being evaluated by the contractors’ designers,” says Parris.
There are multiple construction projects in the area with one taking place just south of the current project and a third future project being discussed. Regarding the project to the south, Parris says, “To coordinate the traffic control with a different entity that has different temporary traffic patterns can present issues on what construction activities can be done at that location.”
The contract for the third project was awarded last year and is currently in the design phase with construction scheduled to begin this summer. The project entails the same type of work as is being done between MM 80 and MM 97. It was broken up into different contracts based on the availability of funds. This will mean an additional entity will have to be consulted regarding traffic patterns making managing logistics all the more complex.
This project is another example of infrastructure keeping up with the new reality. It will improve safety for commuters and provide a financial boost to the local economy by increasing capacity and level of service to the interstate and interchanges. These benefits and the resulting easing of congestion will improve convenience and surely make commuters in the area happy.