Aiming to increase capacity and improve safety on Interstate 26 between Little Mountain and Irmo, the South Carolina Department of Transportation (SCDOT) has embarked on the $421 million Midlands Connection project.

“The interesting thing for the SCDOT is that this is the third largest contract that we have ever had,” says Brad S. Reynolds, Project Manager for SCDOT.

SCDOT divided the project into three segments, starting construction at the east end of the project, closest to Columbia. About 52,300 vehicles drive on the segment daily, with projections to reach 104,600 in 2040.

Secretary of Transportation Christy Hall called this section of I-26 “a vital link in our interstate system” in a statement.

The Midlands Connection will bring the corridor up to current standards. It is part of the state’s strategic 10-year plan.

“SCDOT’s task over 10 years, beginning in 2016 and beyond, is to repair and rebuild our transportation network to ensure that our citizens and businesses can travel on a safe and reliable system,” Reynolds says. “With additional funding from the legislative session in 2017, there were four main investment areas included in the plan and one of those is congestion on the interstate system. This project is contributing to about 16 miles of improvements on the interstate system helping us achieve our 10-year goal.”

Archer United Joint Venture, a partnership between Archer Western of Atlanta, Georgia, and United Infrastructure of Charlotte, North Carolina, received the design-build contract. Infrastructure Consulting & Engineering of Columbia, South Carolina, serves as the engineer of record, and HDR of Omaha, Nebraska, is handling construction engineering and inspection (CEI).

Reynolds explains that the department opted for design-build delivery because it offers “innovative construction methods and control of the final design,” along with the need for fewer “procurement phases, resulting in faster delivery of the project.”

The innovation included the traffic control plan and making all of the 10 bridges similar in their materials and construction, says Michael Christie, Senior Project Manager for Archer United.

The joint venture received the notice to proceed in July 2019. The first two segments are under construction now. Archer United has blended staff members together.

“Coming from the outside looking in, you would have a hard time determining who works for Archer Western and who works for United Infrastructure,” Christie says. “It works well.”

The project entails widening 16 miles of I-26 from MM 85 in Little Mountain to MM 101 in Irmo. From MM 85 to MM 97, crews will widen 12 miles from four to six lanes, and from MM 97 to MM 101, a four-mile stretch closest to Columbia, the number of lanes will be increased from four to eight lanes, Reynolds says. In addition, crews will rebuild the interchanges at exits 85, 91, and 97; replace 10 concrete-girder bridges, overpasses above the interstate; build a new weigh station; and add 306,000 square feet of new noise barriers at the Westcott Ridge and Arbor Springs neighborhoods.

“This is a large interstate project with significant traffic volumes, significant utility coordination and relocations, and right-of-way acquisition all a part of the construction contract, requiring extensive coordination and integration within the design-build team, with the SCDOT, and with third parties,” Reynolds says.

No significant environmental impacts were found during the National Environmental Policy Act process. Multiple permits were obtained from the state and the U.S. Army Corps of Engineers. Archer United was responsible for mitigation of the streams and wetlands.

The project began with segment three, from MM 85 to MM91, in 2020. It includes replacing three overpass bridges, modifying the exit 85 interchange. Segment one was next, from MM 97 to MM 101, and included replacing two overpass bridges and modifying the interchange at exit 97. It also started in 2020.

“What makes this a complex project is the traffic phasing,” Christie says.

The team has to keep two lanes of traffic open in each direction. Crews are working in a narrow space. Traffic has to be moved around to rebuild and expand the road.

Reynolds reports construction challenges are related to “making sure the traveling public is aware of traffic control patterns, and making sure utility relocations and right-of-way acquisition do not impact the schedule on the project.”

Crews are excavating 1.3 cubic yards of dirt on site and hauling in about 650,000 cubic yards of borrow material, which is primarily being placed on the cross road overpasses.

“We are adjusting the profile of the interstate, which raises most of the profiles of the cross roads,” Christie explains. “This also provides additional clearance for oversized loads.”

Currently, the interstate passes through rolling hills, with limited sightlines. Straightening and changing the vertical alignment of the road will improve safety.

The project also includes laying 85,000 linear feet of drainage pipe. About half is a median trunk line – which will be under the concrete barrier wall and run to existing streams – and basins, which will be added as part of the project. The balance is cross line pipe, including at the interchanges. The new pipe will tie in with the existing drainage pipes.

“The median is difficult to access with traffic,” Christie says. “The cross lines are changing and a lot of the drainage will be in a closed system rather than open ditches, like exists today.”

The new weigh station features a “weigh-in-motion” system and a building. The weigh-in-motion uses an array of sensors to determine the truck’s weight without it stopping.

Crews are using GPS and machine control on the dozers, graders, excavators, and concrete paving equipment to improve efficiency and meet schedule. Concrete is the final grading surface, with an asphalt drainage layer below.

The last segment, from MM 91 to MM 97, includes replacement of two overpass bridges, a modification of the exit 91 interchange and an upgrade to the weigh station near MM 94. It is expected to start in fall 2021. Completion of all three segments, by the same team, is expected in April 2024.

Reynolds reports he is proud of “this talented team on all sides: contractor, engineer of record, and the CEI.”

Photos courtesy of South Carolina Department of Transportation