Carolina Crossroads Corridor Improvements

carolina crossroads traffic

Carolina Crossroads Corridor Improvements

Preliminary Environmental and Engineering Work Set Stage for Major Corridor Redevelopment

Located in the heart of South Carolina, the I-20/26/126 corridor is the crossroads of the state economy and the major hub for the Midlands’ commuters, travelers and commerce. In addition to being a main route in and out of Columbia, I-26 is a thoroughfare for travelers headed to the coast and mountains and a major cargo route between Lowcountry ports and Upstate manufacturers. Last improved in the 1980s, the I-20/26/126 corridor does not meet current traffic demands and had earned the nickname “Malfunction Junction.” Finding a solution has become the state’s top interstate priority.

Since 2015, HDR has served as the prime consultant to complete alternatives development, environmental analysis and documentation, public stakeholder engagement, and preliminary design for completion of the EIS and ROD in spring of 2019.

Project Split into Five Phases

The $1.6 billion project has been divided into five phases, with our team assisting on each phase. HDR is providing procurement and design review support for the phase 1, 2 and 3 design-build projects and will perform final design for phases 4 and 5. We also led a nine-month permitting process that concluded with a first of its kind permit to cover all five phases. Throughout project implementation, HDR will also provide bridge hydraulics, storm system and water quality design, utility coordination, strategic communications support, and park and ride analysis.

Upon completion, the corridor will have added capacity with additional lanes in each direction on I-26 as well as 12-foot inside shoulders for emergency vehicles. Traffic flow and speed will be improved through seven reconstructed interchanges, including the replacement of cloverleaf loops with smoothly flowing directional ramps and longer, separated exits. When the project is complete, these changes will save each driver an average of 112 hours per year that would have otherwise been spent sitting in traffic.

carolina crossroads project facts

New Approach for Design-Build Permits

Knowing changes to the design may happen during the construction phases, our team coordinated with SCDOT and the USACE to determine that a more flexible approach was needed for such a large, multi-phase design-build project. This innovative approach estimated the overall impacts and allowed permit modifications to be made within the design-build contracts for the first three of the five phases.  

The permit also included permittee responsible mitigation which provides 65,000 linear feet of stream restoration and preservation and wetland mitigation to make up for the impacts associated with construction of the project. The plan will be maintained by the South Carolina Department of Natural Resources when the project is completed.

The first two phases of the project began construction in 2021, with the entire project scheduled to be completed in 2029.

carolina crossroads traffic


Project of the Year (2022)
Extreme Awards
National Recognition Award (2020)
Engineering Excellence Awards
American Council of Engineering Companies