The engineers at STV have developed an innovative interchange design in concert with their build-partner, The Lane Construction Corporation, that will help complete the heavily traveled Outer Loop of Charlotte For the awarded $93 million Interstate 85/485 interchange design-build contract, STV chose to explore an alternative design during the technical proposal phase. The "turbine interchange" was the alternative that was selected and is expected to provide significant cost savings during construction. Once completed, it will be the first interchange of its kind in North Carolina and one of just a small handful of similar designs in the entire United States. The original plan for the interchange called for a modified clover, which was then redesigned to a four-level stack design to eliminate low-speed loops. The redesign was problematic because it included a number of high-level, long-span bridges that would be difficult to construct, and would require an off-site detour for interstate traffic. Within basically the same footprint as the original design, the turbine interchange offers a two-level design with semi-directional ramps, utilizing smaller, single-span bridges, reduced columns and flatter roadway profiles than the four-level design. The turbine design will also have less impact on traffic during construction and make it easier to widen the roadway in the future. The turbine interchange uses less construction materials, which will shave about $30 million from the project costs while providing a safer and efficient interchange for motorists Construction on the interchange is expected to begin in late 2011 and is scheduled to be completed in 2014. Once finished, the project will help close Charlotte's Outer Loop, I-485, which connects to major roadways such as I-77, NC 16, NC 115 and US 74. An analysis by the North Carolina Department of Transportation projects that the Outer Loop will carry about 130,000 vehicles per day by 2035. With more than 1,700 employees in 32 offices, STV is a leader in providing planning, engineering, architectural, construction management services and environmental services for transportation systems, infrastructure, buildings and other facilities. Engineering News-Record ranked STV 14th in its Top 25 Highways firms survey and 10th in its Top 50 Transportation firms survey. STV is 100 percent employee-owned. For more information, visit our website at www.stvinc.com or follow @STVGroup on Twitter.

• published: 14 Sep 2011
• views: 3062